file which includes the numerous        
original illustrations4       ,see      
#dgiha-;h4htm or #dgiha-;h4zip3         
7https3_/_/www4gutenberg4org_/cache_/epu
b_/#dgiha_/pg#dgiha-;images4html7       
or                                      
7https3_/_/www4gutenberg4org_/files_/#dg
iha_/dgiha-;h4zip7         ,images of   
the original pages are available through
       ,internet ,archive_/,american    
,libraries4 ,see                        
https3_/_/archive4org_/details_/langleym
emoironm#jjlang   ,transcriber's note3  
,the original page numbers 7example3    
p#jeb7 are included in       the text to
 facilitate use of the index4           
,text enclosed by greater-than or       
less-than symbols is in       italics   
7italics74        ,small capitals have  
been trascribed as ,,all ,,capitals4    
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subscription4 ,a single       character 
following an underscore is subscripted  
7example3       ,h#b,o74 ,multiple      
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superscription4 ,a       single         
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version or in the html version4 ,if so1 
the reader should       consult the     
original page images referred to above4 
,an additional transcriber's note is at 
the end of the       text4              
,smithsonian ,contributions to          
,knowledge ,volume #bg ,number #c       
,,langley ,,memoir ,,on ,,mechanical    
,,flight  ,,part ,i4 #ahhg ,,to #ahif   
by  ,,samuel ,,pierpont ,,langley       
,edited by ,charles ,m4 ,manly  ,,part  
,,ii4 #ahig ,,to #aijc  by  ,,charles   
,m4 ,,manly  ,assistant in ,charge of   
,experiments        ,illustration       
7,publication #aidh7  ,city of          
,washington ,published by the           

,smithsonian ,institution #aiaa         
,commission to whom this ,memoir has    
been referred3 ,otto ,hilgard ,tittman1 
,george ,owen ,squier1 ,albert ,francis 
,zahm4  ,the ,lord ,baltimore ,press    
,baltimore1 ,,md41 ,u4 ,s4 ,a4 #fgjji   
page iii  ,,advertisement   ,the present
 work1 entitled 8,langley ,memoir on    
,mechanical ,flight10 as planned by the 
late ,secretary ,samuel ,pierpont       
,langley1 follows his publications on   
8,experiments in ,aerodynamics0 and     
8,the ,internal ,work of the ,wind0     
printed in #ahia and #ahic1             
respectively1 as parts of ,volume #bg of
 the ,smithsonian ,contributions to     
,knowledge4  ,this ,memoir was in       
preparation at the time of ,mr4         
,langley's death in #aijf1 and ,part ,i1
 recording experiments from #ahhg to    
#ahif1 was written by him4 ,part ,,ii1  
on experiments from #ahig to #aijc1 has 
been written by ,mr4 ,charles ,m4       
,manly1 who became ,mr4 ,langley's      
,chief ,assistant in ,june1 #ahih4 ,the 

sources of information for this ,part   
were the original carefully recorded    
accounts of the experiments described4  
,it is expected later to publish a third
 part of the present memoir1 to consist 
largely of the extensive technical data 
of tests of the working of various types
 of curved surfaces1 propellers1 and    
other apparatus4  ,it is of interest    
here to note that experiments with the  
,langley type of aerodrome#a did not    
actually cease in ,december1 #aijc1 when
 he made his last trial with the        
man-carrying machine1 but as recently as
 ,august #f1 #aijg1 a ,french aviator   
made a flight of nearly #ejj feet with  
an aerodrome of essentially the same    
design4 7,see ,appendix47  ,in          
accordance with the established custom  
of referring to experts in the subject  
treated1 all manuscripts intended for   
publication in the ,smithsonian         
,contributions to ,knowledge1 this work 
was examined and recommended by a       
,commission consisting of ,mr4 ,o4 ,h4  

,tittman1 ,superintendent of the ,united
 ,states ,coast and ,geodetic ,survey1  
who witnessed some of the field trials1 
,george ,o4 ,squier1 ,ph4 ,d4 7,johns   
,hopkins71 ,major1 ,signal ,corps1 ,u4  
,s4 ,army1 and ,albert ,francis ,zahm1  
,ph4 ,d41 of ,washington ,city4         
,,charles ,d4 ,,walcott1  ,secretary of 
the ,smithsonian ,institution4          
,,footnotes3  #a ,the name 8aerodrome0  
was given by ,secretary ,langley to the 
flying machine in #ahic1 from  7to      
traverse the air7 and  air              
runner4--,internal ,work of the ,wind1  
p4 #e4      ,,preface   ,the present    
volume on ,mechanical ,flight consists1 
as the title-page indicates1 of two     
parts4 ,the first1 dealing with the long
 and notable series of early experiments
 with small models1 was written almost  
entirely by ,secretary ,langley with the
 assistance of ,mr4 ,e4 ,c4 ,huffaker   
and ,mr4 ,g4 ,l4 ,fowler in #ahig4 ,such
 chapters as were not complete have been
 finished by the writer and are easily  

noted as they are written in the third  
person4 ,it has been subjected only to  
such revision as it would have received 
had ,mr4 ,langley lived to supervise    
this publication1 and has therefore the 
highest value as an historical record4  
,the composition of the second part1    
dealing with the later experiments with 
the original and also new models and the
 construction of the larger aerodrome1  
has necessarily devolved upon me4 ,this 
is in entire accordance with the plan   
formed by ,mr4 ,langley when ,i began to
 work with him in #ahih1 but it is to me
 a matter of sincere regret that the    
manuscript in its final form has not had
 the advantage of his criticism and     
suggestions4 ,if the reader should feel 
that any of the descriptions or         
statements in this part of the volume   
leave something to be desired in        
fullness of detail1 it is hoped that    
some allowance may be made for the fact 
that it has been written in the scanty  
and scattered moments that could be     

snatched from work in other lines which 
made heavy demands upon the writer's    
time and strength4 ,it is believed1     
however1 that sufficient data are given 
to enable any competent engineer to     
understand thoroughly even the most     
complicated phases of the work4         
,persons who care only for the          
accomplished fact may be inclined to    
underrate the interest and value of this
 record4 ,but even they may be reminded 
that but for such patient and           
unremitting devotion as is here         
enregistered1 the now accomplished fact 
of mechanical flight would still remain 
the wild unrealized dream which it was  
for so many centuries4  ,to such men as 
,mr4 ,langley an unsuccessful experiment
 is not a failure but a means of        
instruction1 a necessary and often an   
invaluable stepping-stone to the desired
 end4 ,the trials of the large aerodrome
 in the autumn of #aijc1 to which the   
curiosity of the public and the         
sensationalism of the newspapers gave a 

character of finality never desired by  
,mr4 ,langley1 were to him merely       
members of a long series of experiments1
 as much so as any trial of one of the  
small aerodromes or even of one of the  
earliest rubber-driven models4 ,had his 
health and strength been spared1 he     
would have gone on with his experiments 
undiscouraged by these accidents in     
launching and undeterred by criticism   
and misunderstanding4  ,moreover1 it is 
to be borne in mind that ,mr4 ,langley's
 contribution to the solution of the    
problem is not to be measured solely by 
what he himself accomplished1 important 
as that is4 ,he began his investigations
 at a time when not only the general    
public but even the most progressive men
 of science thought of mechanical flight
 only as a subject for ridicule1 and    
both by his epoch-making investigations 
in aerodynamics and by his own devotion 
to the subject of flight itself he      
helped to transform into a field of     
scientific inquiry what had before been 

almost entirely in the possession of    
visionaries4  ,the original plans for   
this publication provided for a third   
part covering the experimental data     
obtained in tests of curved surfaces and
 propellers4 ,owing to the pressure of  
other matters on the writer1 the        
preparation of this third part is not   
yet complete and is reserved for later  
publication4   ,,charles ,m4 ,,manly4   
,,new ,,york ,,city4      ,,contents    
,,part ,i   ,i4 ,introductory ''' #a    
,,ii4 ,preliminary ''' #e               
,experiments with small models ''' #f   
,abbreviations and symbols employed ''' 
#ad     ,experiments with ,aerodromes   
,nos4 #cj and #ca ''' #af   ,,iii4      
,available motors ''' #ba     ,india    
rubber ''' #ba     ,steam engine ''' #bd
     ,gunpowder1 hot-water1 compressed  
air ''' #be     ,gas1 electricity '''   
#bf     ,carbonic-acid gas ''' #bh      
,,iv4 ,early steam motors and other     
models ''' #cj   ,v4 ,on sustaining     
surfaces ''' #da     ,experiments in the

 open wind ''' #db     ,relation of air 
to weight and power ''' #dc   ,,vi4     
,balancing the aerodrome ''' #de        
,lateral and longitudinal stability ''' 
#de   ,,vii4 ,history of construction of
 frame and engines of    aerodromes ''' 
#ec     #ahic ''' #ec     #ahid ''' #fd 
#ahie ''' #ge     #ahif ''' #gi         
,,viii4 ,history of construction of     
sustaining and guiding    surfaces of   
aerodromes #d1 #e1 and #f ''' #hj       
,introduction ''' #hj     #ahic1 #ahid  
''' #ha     #ahie ''' #he     #ahif ''' 
#hi   ,,ix4 ,history of launching       
apparatus and field trials of           
aerodromes #d1 #e1 and #f ''' #ib       
#ahib ''' #ib     #ahic ''' #ic         
,field trials ''' #ic     #ahid ''' #if 
#ahie ''' #aja     #ahif ''' #ajf   ,x4 
,description of the launching apparatus 
of aerodromes    ,nos4 #e and #f '''    
#aaj     ,description of ,aerodrome ,no4
 #e ''' #aaa     ,description of        
,aerodrome ,no4 #f ''' #abj   ,,part    
,,ii   ,i4 ,introductory ''' #abc       

,,ii4 ,general considerations ''' #abh  
,,iii4 ,experiments with models ''' #acc
     ,condensed record of flights of    
aerodromes ,nos4 #e and #f1    from     
,june #g to ,august #c1 #ahii ''' #ace  
,june #g--;aerodrome ,no4 #f ''' #ace   
,june #ac--;aerodrome ,no4 #f ''' #acg  
,june #bb--;aerodrome ,no4 #f ''' #aci  
,june #bc--;aerodrome ,no4 #f ''' #adj  
,june #bg--;aerodrome ,no4 #e ''' #adj  
,june #cj--;aerodrome ,no4 #e ''' #ada  
,july #a to ,july #h ''' #adb     ,july 
#aa to ,july #ad--;aerodrome ,no4 #e '''
 #adc     ,july #ai--;aerodrome ,no4 #e 
''' #add     ,july #bg--;aerodrome ,no4 
#f ''' #ade     ,july #bh--;aerodrome   
,no4 #f ''' #adf     ,july              
#bi--;aerodrome ,no4 #e ''' #adg        
,august #a--;aerodrome ,no4 #e ''' #adh 
,august #c--;aerodrome ,no4 #e ''' #adi 
,,iv4 ,house-boat and launching         
apparatus ''' #aef   ,v4 ,construction  
of frame of large aerodrome ''' #afd    
,transverse frame ''' #agd              
,propellers ''' #agh     ,aviator's car 

''' #ahe   ,,vi4 ,construction of       
supporting surfaces ''' #ahh   ,,vii4   
,equilibrium and control ''' #bjg       
,,viii4 ,the experimental engine '''    
#bah   ,,ix4 ,the quarter-size model    
aerodrome ''' #bbf   ,x4 ,construction  
and tests of the large engine ''' #bcd  
,,xi4 ,shop tests of the aerodrome '''  
#bea   ,,xii4 ,field trials in #aijc '''
 #bee     ,statement made by ,mr4 ,manly
 to associated press ''' #bff           
,report of ,war ,department1 ,january1  
#aijd ''' #bgf     ,langley aerodrome1  
,official ,report of ,board of          
,ordnance1    ,october1 #aijd ''' #bgh  
,statement to the ,press ''' #bhj       
,present status of the work ''' #bha    
,blriot ,machine of #aijg on ,langley   
type ''' #bhc   ,appendix4 ,study of    
,american ,buzzard and 8,john ,crow0 '''
 #bhe     ,instructions to assistants   
''' #bid     ,data sheets #a to #ab ''' 
#big   ,index ''' #cji      ,,list ,,of 
,,plates    #a4 ,rubber-motor model     
aerodromes ,nos4 #aa1 #ac1 #ad1 #ae1    

#bf1  #cj1 #ca ''' #af   #b4            
,rubber-motor model aerodromes ,nos4    
#aa1 #ac1 #ad ''' #af   #c4             
,rubber-motor model aerodromes ,nos4    
#ae1 #bd ''' #af   #d4 ,rubber-motor    
model aerodrome ,no4 #bf ''' #af   #e4  
,rubber-pull model aerodrome ''' #bd    
#f4 ,rubber-pull model aerodrome ''' #bd
   #g4 ,rubber-pull model aerodrome ''' 
#bd   #h4 ,rubber-pull model aerodrome  
''' #bd   #i4 ,rubber-pull model        
aerodrome ''' #bd   #aj4 ,steel frames  
of aerodromes ,nos4 #j1 #a1 #b1 #c1     
#ahia and  #ahib ''' #cc   #aa4 ,steel  
frames of aerodromes ,nos4 #d1 #e1 #f1  
#ahic1 #ahie1  and #ahif ''' #ec   #ab4 
,burners1 aeolipiles1 and separators '''
 #ef   #ac4 ,boilers of aerodromes '''  
#ef   #ad4 ,aerodrome ,no4 #e1 ,december
 #c1 #ahie4 ,plan view4 ,rudder  removed
 ''' #gh   #ae4 ,aerodrome ,no4 #e1     
,december #c1 #ahie4 ,side view ''' #gh 
#af4 ,early types of wings and systems  
of guying ''' #ha   #ag4 ,aerodrome ,no4
 #e4 ,plan of wings and system of guying

 '''  #hi   #ah4 ,house-boat with       
overhead launching apparatus1 #ahif ''' 
#ajf   #ai4 ,paths of aerodrome flights1
 ,may #f and ,november #bh1  #ahif1 near
 ,quantico1 ,va41 on the ,potomac ,river
 ''' #ajh   #bj4 ,instantaneous         
photograph of the aerodrome at the      
moment after launching in its flight at 
,quantico on the  ,potomac ,river1 ,may 
#f1 #ahif4 ,enlarged ten times ''' #ajh 
#ba4 ,instantaneous photograph of the   
aerodrome at a  distance in the air     
during its flight at ,quantico on the   
,potomac ,river1 ,may #f1 #ahif4        
,enlarged ten times ''' #ajh   #bb4     
,instantaneous photograph of the        
aerodrome at a  distance in the air     
during its flight at ,quantico on the   
,potomac ,river1 ,may #f1 #ahif4        
,enlarged ten times ''' #ajh   #bc4     
,overhead launching apparatus ''' #ajh  
#bd4 ,overhead launching apparatus '''  
#ajh   #be4 ,side view of steel frame of
 aerodrome ,no4 #e suspended  from      
launching-car1 ,october #bd1 #ahif '''  

#aab   #bf;,a4 ,dimensioned drawing of  
boiler coils1 burners1 pump1  needle    
valve1 and thrust bearing ''' #aaf      
#bf;,b4 ,dimensioned drawing of engine  
,no4 #e ''' #aaf   #bg;,a4 ,side and end
 elevations of aerodrome ,no4 #e1 ,may  
#aa1  #ahif ''' #aaf   #bg;,b4          
,aerodrome ,no4 #e4 ,plan view4 ,october
 #bd1 #ahif ''' #aaf   #bh4 ,steel frame
 of aerodrome ,no4 #f on launching car  
''' #abj   #bi;,a4 ,plan view of        
aerodrome ,no4 #f4 ,october #bc1 #ahif  
''' #abb   #bi;,b4 ,side elevation of   
aerodrome ,no4 #f4 ,october #bc1 #ahif  
'''  #abb   #cj4 ,plan view of steel    
frames and power plants of  aerodromes  
,nos4 #e and #f ''' #abb   #ca4 ,details
 of aerodrome ,no4 #e ''' #abb   #cb4   
,drawings of proposed man-carrying      
aerodrome1 #ahih ''' #acj   #cc4 ,path  
of flight of aerodrome ,no4 #f1 ,june   
#g1 #ahii ''' #acf   #cd4 ,paths of     
flight of aerodrome ,no4 #f1 ,june #ac  
and #bc1  #ahii ''' #adj   #ce4         
,aerodrome ,no4 #e on launching-ways '''

 #adb   #cf4 ,paths of flights of       
aerodrome ,no4 #e1 ,july #bi1 #ahii ''' 
#adh   #cg4 ,experimental forms of      
superposed surfaces1 #ahih1 #ahii4      
7,see also plates #fd and #fe47 ''' #aec
   #ch4 ,house-boat and launching       
apparatus1 #ahii ''' #aef   #ci4 ,method
 of attaching guy-wires to guy-posts to 
relieve  torsional strain ''' #aeh      
#dj4 ,general plan and details of       
launching-car ''' #afj   #da4 ,aerodrome
 on launching-car ''' #afj   #db4       
,details of clutch-post for             
launching-car ''' #afj   #dc4 ,front end
 of track just preparatory to launching 
aerodrome ''' #afj   #dd4 ,resistance of
 wires at given velocities ''' #aff     
#de4 ,frame of aerodrome ,a1 ,january   
#ca1 #aijj ''' #afh   #df4 ,frame of    
aerodrome ,a1 ,january #ca1 #aijj '''   
#afh   #dg4 ,frame of aerodrome ,a1     
,february #a1 #aijj ''' #afh   #dh4     
,frame of aerodrome ,a1 ,february #a1   
#aijj ''' #afh   #di4 ,guy-wire system1 
,july #aj1 #aijb ''' #agj   #ej4        

,guy-wire system1 ,july #aj1 #aijb '''  
#agj   #ea4 ,guy-wire system1 ,july #aj1
 #aijb ''' #agj   #eb4 ,scale drawing of
 aerodrome ,a4 ,end elevation ''' #agj  
#ec4 ,scale drawing of aerodrome ,a4    
,side elevation ''' #agj   #ed4 ,scale  
drawing of aerodrome ,a4 ,plan ''' #agj 
#ee4 ,frame fittings and guy-wire       
attachments1 etc4 ''' #agd   #ef4 ,frame
 fittings and guy-wire attachments1 etc4
 ''' #agd   #eg4 ,frame fittings and    
guy-wire attachments1 etc4 ''' #agd     
#eh4 ,bed plate gears1 etc4 ''' #agf    
#ei4 ,wing clamps ''' #ahc   #fj4       
,hoisting aerodrome to launching-track  
''' #ahd   #fa4 ,aerodrome on           
launching-car2 front wings in place1    
guy-wires adjusted ''' #ahd   #fb4      
,details of guy-posts ''' #ahd   #fc4   
,guy-post and pin on launching-car '''  
#ahd   #fd4 ,experimental type of       
superposed wings1 ,march #b1 #ahii '''  
#aib   #fe4 ,experimental type of       
superposed wings1 ,march #b1 #ahii '''  
#aib   #ff4 ,details of ribs and        

fittings for wings ''' #bjj   #fg4      
,cross-section of ribs ''' #bja   #fh4  
,automatic equilibrium devices ''' #bab 
#fi4 ,mechanism of control ''' #bab     
#gj4 ,plan view of quarter-size model   
aerodrome1 ,june #a1  #aijj ''' #bcb    
#ga4 ,plan view of quarter-size model   
aerodrome ''' #bcb   #gb4 ,end1 side1   
and three-quarter elevations of         
quarter-size model aerodrome ''' #bcb   
#gc4 ,launching-car with floats ''' #bcb
   #gd4 ,launching-car with floats '''  
#bcb   #ge4 ,quarter-size model         
aerodrome equipped with superposed      
surfaces1 ,june #aa1 #aija4 ,side view  
''' #bcb   #gf4 ,quarter-size model     
aerodrome equipped with superposed      
surfaces1 ,june #aa1 #aija4 ,end view   
''' #bcb   #gg4 ,cylinders of engine of 
quarter-size model aerodrome '''  #bcc  
#gh4 ,engine of aerodrome ,a4 ,section  
through cylinder and  drum ''' #bcf     
#gi4 ,engine of aerodrome ,a4 ,end      
elevation1 port side ''' #bcf   #hj4    
,engine of aerodrome ,a4 ,top plan '''  

#bcf   #ha4 ,engine of aerodrome ,a4    
,elevation starboard bed plate1         
sparking mechanism ''' #bcf   #hb4      
,dynamometer tests of large engine '''  
#bdh   #hc4 ,dynamometer tests of large 
engine ''' #bdh   #hd4 ,dynamometer     
tests of large engine ''' #bdh   #he4   
,location of house-boat in center of    
,potomac ,river1  ,july #ad1 #aijc '''  
#bef   #hf4 ,quarter-size model         
aerodrome mounted on launching-car  ''' 
#bfj   #hg4 ,quarter-size model         
aerodrome in flight1 ,august #h1 #aijc  
''' #bfj   #hh4 ,quarter-size model     
aerodrome in flight1 ,august #h1 #aijc  
''' #bfj   #hi4 ,quarter-size model     
aerodrome in flight1 ,august #h1 #aijc  
''' #bfj   #ij4 ,quarter-size model     
aerodrome in flight1 ,august #h1 #aijc  
''' #bfj   #ia4 ,quarter-size model     
aerodrome in flight1 ,august #h1 #aijc  
''' #bfj   #ib4 ,quarter-size model     
aerodrome in flight1 ,august #h1 #aijc  
''' #bfj   #ic4 ,quarter-size model     
aerodrome at end of flight1 ,august  #h1

 #aijc ''' #bfj   #id4 ,hoisting wing of
 full-size aerodrome ''' #bfc   #ie4    
,flight of large aerodrome1 ,october #g1
 #aijc ''' #bff   #if4 ,flight of large 
aerodrome1 ,october #g1 #aijc ''' #bff  
#ig4 ,aerodrome being recovered1        
,october #g1 #aijc ''' #bgj   #ih4      
,aerodrome in water1 ,october #g1 #aijc 
''' #bgj   #ii4 ,aerodrome in water1    
,october #g1 #aijc ''' #bgj   #ajj4     
,aerodrome in water1 ,october #g1 #aijc 
''' #bgj   #aja4 ,attempted launching of
 aerodrome1 ,december #h1 #aijc '''     
#bgd      ,,references    ,aerodynamics4
 ,see ,langley1 ,s4 ,p4 ,experiments in 
,aerodynamics4   ,l',aronaute4 ,see     
,pnaud1 ,a4   ,aeronautical ,society4   
,see ,harting1 ,p4   ,aroplane          
automoteur4 ,see ,pnaud1 ,a4            
,balancing of ,engines1 ,steam1 ,gas1   
and ,petrol4 ,see ,sharp1  ,a4          
,century ,magazine4 ,see ,maxim1 ,h4 ,s4
   ,comptes ,rendus1 of the ,sessions of
 the ,academy of  ,sciences4 ,see       
,langley1 ,s4 ,p4 ,description du vol   

mchanique4   ,encyclopdia ,britannica4  
,see ,flight and ,flying ,machines4     
,experiments in ,aerodynamics4 ,see     
,langley1 ,s4 ,p4   ,flight and ,flying 
,machines4 ,encyclopdia ,britannica1    
#ith  ed41 ,vol4 #i1 #ahgi1 ,edinburgh1 
pp4 #cjh-cbb1 figs4 #a-de4   ,harting1  
,p4 ,observations of the relative size  
of the wings  and the weight of the     
pectoral muscles in the vertebrated     
flying animals4 ,annual ,report of the  
,aeronautical ,society  of ,great       
,britain1 ,no4 #e1 #ahgj1 ,greenwich1   
pp4 #ff-gg4   ,il nuovo aeroplano       
,blriot1 ,bollettino della ,societ      
,aeronautica ,italiana1 ,anno ,,iv1 ,n4 
#h1 ,agosto #aijg1 ,roma1  pp4 #bgi-bhb1
 figs4 #d4   ,langley1 ,bollettino della
 ,societ ,aeronautica ,italiana1  ,anno 
,,ii1 ,num4 #aa-ab1 ,nov4-,dic4 #aije1  
,roma1 pp4 #ahg-ahh1  figs4 #aj4        
,langley1 ,s4 ,p4 ,description du vol   
mchanique4 ,comptes  ,rendus de         
l',acadmie des ,sciences1 ,t4 #abb1 ,mai
 #bf1 #ahif1  ,paris1 pp4 #aagg-aagh4   

,langley1 ,s4 ,p4 ,experiments in       
,aerodynamics4 ,smithsonian             
,contributions to ,knowledge1 ,vol4 #bg1
 #ahia1 ,washington1 ,d4  ,c41 pp4 #aae1
 pl4 #aj4   ,langley1 ,s4 ,p4 ,le       
travail intrieur du vent4 ,revue de     
l',aronautique1 #f;e anne1 #c;e         
livraison1 #ahic1 ,paris1 pp4  #cg-fh4  
,langley1 ,s4 ,p4 ,the ,flying ,machine4
 ,mc,clures ,magazine1 ,vol4  #i1 ,no4  
#b1 ,june1 #ahig1 ,n4 ,y41 pp4 #fdg-ffj4
   ,langley1 ,s4 ,p4 ,the ,internal     
,work of the ,wind4 ,smithsonian        
,contributions to ,knowledge1 ,vol4 #bg1
 #ahic1 ,washington1 ,d4  ,c41 pp4 #bc1 
pl4 #f4   ,mc,clure's ,magazine4 ,see   
,langley1 ,s4 ,p4 ,the ,flying          
,machine4   ,maxim1 ,h4 ,s4 ,aerial     
navigation4 ,the power required4        
,century ,magazine1 ,vol4 #db1 ,no4 #f1 
,oct41 #ahia1 ,n4 ,y41 pp4  #hbi-hcf1   
figs4 #a-f4   ,pnaud1 ,a4 ,aeroplane    
automoteur4 ,l',aronaute1 #e;e anne1    
,no4 #a1 ,jan41 #ahgb1 ,paris1 pp4 #b-i1
 figs4 #a-d4   ,revue de l',aronautique4

 ,see ,langley1 ,s4 ,p4 ,le travail     
intrieur du vent4   ,sharp1 ,a4         
,balancing of ,engines1 ,steam1 ,gas1   
and ,petrol4  ,new ,york1 ,longmans1    
,green  ,co41 #aijg4   ,wellner1 ,georg4
 ,versuche ueber den ,luftwiderstand    
gewlbter ,flchen im ,winde und auf      
,eisenbahnen4   ,zeitschrift fr         
,luftschiffahrt1 ,bd4 #ab1 ,beilage1    
#ahic1  ,berlin1 pp4 #a-dh4             
,zeitschrift fr ,luftschiffahrt4 ,see   
,wellner1 ,georg4   p#jja      ,,langley
 ,,memoir ,,on ,,mechanical ,,flight    
,,part ,i4 #ahhg ,,to #ahif   ,,by ,s4  
,p4 ,,langley   ,,edited ,,by ,,charles 
,m4 ,,manly    ,,chapter ,i             
,,introductory  ,i#b announced in       
#ahia1c as the result of experiments    
carried on by me through previous years1
 that it was possible to construct      
machines which would give such a        
velocity to inclined surfaces that      
bodies indefinitely heavier than the air
 could be sustained upon it1 and moved  
through it with great velocity4 ,in     

particular1 it was stated that a plane  
surface in the form of a parallelogram  
of #gf4b cm4#ab4b cm4 7#cjd4h inches71  
weighing #ejj grammes 7#a4a lbs471 could
 be driven through the air with a       
velocity of #bj metres 7#fe4f feet7 per 
second in absolutely horizontal flight1 
with an expenditure of #a_/bjj          
horse-power1 or1 in other terms1 that #a
 horse-power would propel and sustain in
 horizontal flight1 at such a velocity  
7that is1 about #dj miles an hour71 a   
little over #bjj pounds weight of such  
surface1 where the specific gravity of  
the plane was a matter of secondary     
importance1 the support being derived   
from the elasticity and inertia of the  
air upon which the body is made to run  
rapidly4  ,it was further specifically  
remarked that it was not asserted that  
planes of any kind were the best forms  
to be used in mechanical flight1 nor was
 it asserted1 without restrictions1 that
 mechanical flight was absolutely       
possible1 since this depended upon our  

ability to get horizontal flight during 
transport1 and to leave the earth and to
 return to it in safety4 ,our ability   
actually to do this1 it was added1 would
 result from the practice of some       
unexplored art or science which might be
 termed ,aerodromics1 but on which ,i   
was not then prepared to enter4  ,i had 
at that time1 however1 made certain     
preliminary experiments with flying     
models1 which have been continued up to 
the present year1#d and at the same time
 ,i have continued experiments distinct 
from these1 with the small              
whirling-table established at           
,washington4 ,the results obtained from 
the latter being supplemental to those  
published in 8,experiments in           
,aerodynamics10 and p#jjb being more or 
less imperfect1 were at first intended  
not for publication1 but for my own     
information on matters where even an    
incomplete knowledge was better than the
 absence of any4  ,it is to be          
remembered that the mechanical          

difficulties of artificial flight have  
been so great that1 so far as is known1 
never at any time in the history of the 
world previous to my experiment of ,may1
 #ahif1 had any such mechanism1 however 
actuated1 sustained itself in the air   
for more than a few seconds--never1 for 
instance1 a single half-minute--and     
those models which had sustained        
themselves for these few seconds1 had   
been in almost every case actuated by   
rubber springs1 and had been of such a  
size that they should hardly be         
described as more than toys4 ,this      
refers to actual flights in free air1   
unguided by any track or arm1 for1 since
 the most economical flight must always 
be a horizontal one in a straight       
line1#e the fact that a machine has     
lifted itself while pressed upward      
against an overhead track which compels 
the aerodrome to move horizontally and  
at the proper angle for equilibrium1 is 
no proof at all of real 8flight40  ,i   
desire to ask the reader's consideration

 of the fact that even ten years ago1#f 
the whole subject of mechanical flight  
was so far from having attracted the    
general attention of physicists or      
engineers1 that it was generally        
considered to be a field fitted rather  
for the pursuits of the charlatan than  
for those of the man of science4        
,consequently1 he who was bold enough to
 enter it1 found almost none of those   
experimental data which are ready to    
hand in every recognized and reputable  
field of scientific labor4 ,let me      
reiterate the statement1 which even now 
seems strange1 that such disrepute      
attached so lately to the attempt to    
make a 8flying-machine10 that hardly any
 scientific men of position had made    
even preliminary investigations1 and    
that almost every experiment to be made 
was made for the first time4 ,to cover  
so vast a field as that which           
aerodromics is now seen to open1 no     
lifetime would have sufficed4 ,the      
preliminary experiments on the primary  

question of equilibrium and the         
intimately associated problems of the   
resistance of the sustaining surfaces1  
the power of the engines1 the method of 
their application1 the framing of the   
hull structure which held these1 the    
construction of the propellers1 the     
putting of the whole in initial motion1 
were all to be made1 and could not be   
conducted with the exactness which would
 render them final models of accuracy4  
,i beg the reader1 therefore1 to recall 
as he reads1 that everything here has   
been done with a view to putting a trial
 aerodrome successfully in flight within
 a few years1 and thus giving an early  
demonstration of the only kind which is 
conclusive in the eyes of the scientific
 man1 as well as of the general         
public--a demonstration that mechanical 
flight is possible---by actually flying4
  ,all that has been done1 has been with
 an eye principally to this immediate   
p#jjc result1 and all the experiments   
given in this book are to be considered 

only as approximations to exact truth4  
,all were made with a view1 not to some 
remote future1 but to an arrival within 
the compass of a few years at some      
result in actual flight that could not  
be gainsaid or mistaken4  ,although many
 experimenters have addressed themselves
 to the problem within the last few     
years--and these have included men of   
education and skill--the general failure
 to arrive at any actual flight has     
seemed to throw a doubt over the        
conclusions which ,i had announced as   
theoretically possible4  ,when1         
therefore1 ,i was able to state that on 
,may #f1 #ahif1 such a degree of success
 had been attained that an aerodrome1   
built chiefly of steel1 and driven by a 
steam engine1 had indeed flown for over 
half a mile--that this machine had      
alighted with safety1 and had performed 
a second flight on the same day1 it was 
felt that an advance had been made1 so  
great as to constitute the long desired 
experimental demonstration of the       

possibility of mechanical flight4 ,these
 results were communicated to the       
,french ,academy in the note given      
below4#g  ,independently of the         
preliminary experiments in aerodynamics 
already published1 ,i had been engaged  
for seven years in the development of   
flying models4 ,although the work was   
discouraging and often resulted in      
failure1 success was finally reached    
under the conditions just referred to1  
which obviously admitted of its being   
reached again1 and on a larger scale1 if
 desired4 p#jjd  ,in view of the great  
importance of these experiments1 as     
demonstrating beyond question the       
practicability of the art of mechanical 
flight1 and also in view of the yet     
inchoate state of this art1 ,i have     
thought it worth while to publish an    
account of them somewhat in detail1 even
 though they involve an account of      
failures2 since it is from them1 that   
those to whom it may fall to continue   
such constructions1 will learn what to  

avoid1 as well as the raison d'etre of  
the construction of the machines which  
have actually flown4  ,in an established
 art or science1 this description of the
 essays and failures which preceded full
 knowledge would have chiefly an        
historical interest4 ,here almost       
nothing is yet established beyond the   
fact that mechanical flight has actually
 been attained4 ,the history of failure 
is in this case1 then1 if ,i do not     
mistake1 most necessary to an           
understanding of the road to future     
success1 to which it led1 and this has  
been my motive in presenting what ,i    
have next to say so largely in narrative
 form4   p#jje    ,,chapter ,,ii        
,,preliminary  ,part ,i of the present  
work is intended to include an account  
of the experiments with actual flying   
models1 made chiefly at or near         
,washington1 from the earliest with     
rubber motors up to the construction of 
the steam aerodromes that performed the 
flights of ,may #f and ,november #bh1   

#ahif4  ,an account of some observations
 conducted at ,washington1 with the     
whirling table1 on the reaction of      
various surfaces upon the air1 is       
relegated to a later part4  ,the        
experiments with working models1 which  
led to the successful flights1 were     
commenced in #ahhg1 and it has seemed to
 me preferable to put them at first in  
chronological order1 and to present to  
the reader what may seem instructive in 
their history1 while not withholding    
from him the mistaken efforts which were
 necessarily made before the better path
 was found4 ,in this same connection1 ,i
 may say that ,i have no professional   
acquaintance with steam engineering1 as 
will1 indeed1 be apparent from the      
present record1 but it may be observed  
that none of the counsel which ,i       
obtained from those possessing more     
knowledge was useful in meeting the     
special problems which presented        
themselves to me1 and which were solved1
 as far as they have been solved1 by    

constant 8trial and error40  ,i shall1  
then1 as far as practicable1 follow the 
order of dates in presenting the work   
that has been done1 but the reader will 
observe that after the preliminary      
investigations and since the close of   
#ahic1 at least four or five independent
 investigations1 attended with constant 
experiment and radically distinct kinds 
of construction1 have been going on     
simultaneously4 ,we have1 for instance1 
the work in the shop1 which is of two   
essentially different kinds3 first1 that
 on the frames and engines1 which       
finally led to the construction of an   
engine of unprecedented lightness2      
second1 the experimental construction of
 the supporting and guiding surfaces1   
which has involved an entirely different
 set of considerations1 concerned with  
equilibrium and support in flight4      
,these constructions1 however           
successful1 are confined to the shop and
 are1 as will be seen later1 useless    
without a launching apparatus4 ,the     

construction of a suitable launching    
apparatus itself involved difficulties  
which took years to overcome4 ,and1     
finally1 the whole had to be tested by  
actual flights in free air1 which were  
conducted at a place some #cj miles     
distant from the shop where the original
 construction went on4 p#jjf            
,simultaneously with these1 original    
experiments with the whirling-table were
 being conducted along lines of         
research1 which though necessary have   
only been indicated4 ,we have1 then1 at 
least five subjects1 so distinct that   
they can only be properly treated       
separately1 and accordingly they will be
 found in ,chapters ,,vii1 ,,viii1 ,,ix 
and ,x1 and in ,part ,third in          
preparation4  ,it is inevitable that in 
so complex a study some repetition      
should present itself1 especially in the
 narrative form chosen as the best      
method of presenting the subject to the 
reader4 ,each of these chapters1 then1  
will contain its own historical account 

of its own theme1 so that each subject  
can be pursued continuously in the order
 of its actual development1 while1 since
 they were all interdependent and were  
actually going on simultaneously1 the   
order of dates which is followed in each
 chapter will be a simple and sufficient
 method of reference from one to the    
other4    ,,experiments ,,with ,,small  
,,models  ,in order to understand how   
the need arises for such experiments in 
fixing conditions which it might appear 
were already determined in the work     
8,experiments in ,aerodynamics10#h it is
 to be constantly borne in mind1 as a   
consideration of the first importance1  
that the latter experiments1 being      
conducted with the whirling-table1 force
 the model to move in horizontal flight 
and at a constant angle4 ,now these are 
ideal conditions1 as they avoid such    
practical difficulties as maintaining   
equilibrium and horizontality1 and for  
this reason alone give results more     
favorable than are to be expected in    

free flight4  ,besides this1 the values 
given in 8,aerodynamics0 were obtained  
with rigid surfaces1 and these surfaces 
themselves were small and therefore     
manageable1 while larger surfaces1 such 
as are used in actual flight1 would need
 to be stiffened by guys and like means1
 which offer resistance to the air and  
still further reduce the results        
obtained4 ,it is1 therefore1 fairly     
certain1 that nothing like the lift of  
#bjj pounds to the horse-power for a    
rate of #dj miles an hour1#i obtained   
under these ideal conditions with the   
whirling-table1 will be obtained in     
actual flight1 at least with plane      
wings4  ,the data in 8,aerodynamics0    
were1 then1 insufficient to determine   
the conditions of free flight1 not alone
 because the apparatus compels the      
planes to move in horizontal flight1 but
 because other ideally perfect          
conditions are obtained by surfaces     
rigidly attached to the whirling-table  
so as to present an angle to the wind of

 advance which is invariable during the 
course of the experiment1 whereas the   
surfaces employed in actual flight may  
evidently change this angle and cause   
p#jjg the aerodrome to move upward or   
downward1 and thus depart from          
horizontal flight so widely as to bring 
prompt destruction4  ,to secure this    
balance1 or equilibrium1 we know in     
theory1 that the center of gravity must 
be brought nearly under the center of   
pressure1 by which latter expression we 
mean the resultant of all the forces    
which tend to sustain the aerodrome2 but
 this center of pressure1 as may in fact
 be inferred from 8,aerodynamics10#aj   
varies with the inclination of the      
surface4 ,it varies also with the nature
 of the surface itself1 and for one and 
the same surface is constantly shifted  
unless the whole be rigidly held1 as it 
is on the whirling-table1 and as it     
cannot be in free flight4  ,here1 then1 
are conditions of the utmost importance1
 our knowledge of which1 as derived from

 ordinary aerodynamic experiments1 is   
almost nothing4 ,a consideration of this
 led me to remark in the conclusion of  
8,aerodynamics03   8,i have not         
asserted1 without qualification1 that   
mechanical flight  is practically       
possible1 since this involves questions 
as to the  method of constructing the   
mechanism1 of securing its safe ascent  
and descent1 and also of securing the   
indispensable condition  for the        
economic use of the power ,i have shown 
to be at our  disposal--the condition1  
,i mean1 of our ability to guide it in  
the  desired horizontal direction during
 transport--questions which1 in  my     
opinion1 are only to be answered by     
further experiment and which  belong to 
the inchoate art or science of          
aerodromics on which ,i do  not enter40 
,it is this inchoate art of aerodromics 
which is begun in the following         
experiments with actual flying machines4
  ,in all discussions of flight1        
especially of soaring flight1 the first 

source to which one naturally looks for 
information is birds4 ,but here correct 
deductions from even the most accurate  
of observations are very difficult1     
because the observation cannot include  
all of the conditions under which the   
bird is doing its work4 ,if we could but
 see the wind the problem would be      
greatly simplified1 but as the matter   
stands1 it may be said that much less   
assistance has been derived from        
studious observations on bird-flight    
than might have been anticipated1       
perhaps because it has been found thus  
far impossible to reproduce in the      
flying machine or aerostatic model the  
shape and condition of wing with its    
flexible and controllable connection    
with the body1 and especially the       
instinctive control of the wing to meet 
the requirements of flight that are     
varying from second to second1 and which
 no automatic adjustment can adequately 
meet4  ,at the time ,i commenced these  
experiments1 almost the only            

flying-machine which had really flown   
was a toy-like model1 suggested by ,a4  
,pnaud1 a young ,frenchman of singular  
mechanical genius1 who contributed to   
the world many most original and        
valuable papers on ,aeronautics1 which  
may be found in the journal             
8,l',aeronaute40 ,his aeroplane is a toy
 in size1 with a small propeller p#jjh  
whose blades are usually made of two    
feathers1 or of stiff paper1 and whose  
motive power is a twisted strand of     
rubber4 ,this power maintains it in the 
air for a few seconds and with an       
ordinary capacity for flight of #ej feet
 or so1 but it embodies a device for    
automatically securing horizontal       
flight1 which its inventor was the first
 to enunciate4#aa  ,although ,pnaud     
recognized that1 theoretically1 two     
screws are necessary in an aerial       
propeller1 as the use of a single one   
tends to make the apparatus revolve on  
itself1 he adopted the single screw on  
account of the greater simplicity of    

construction that it permitted4 ,one of 
these little machines is shown as ,no4  
#aa1 ,plates #a and #b4  ,,ab is a stem 
about #b4e mm4 in diameter and #ej cm4  
long4 ,it is bent down at each end1 with
 an offset which supports the rubber and
 the shaft of the screw to which it is  
hooked4 ,the screw ,,hh#a is #ba cm4 in 
diameter1 and has two blades made of    
stiff paper2 two are preferable1 among  
other reasons1 because they can be made 
so that the machine will lie flat when  
it strikes in its descent4 ,about the   
middle of ,,ab there is a 8wing0 surface
 ,,dc1 #de cm4 long and #aa cm4 broad1  
the ends ,c and ,d being raised and a   
little curved4 ,in front of the screw is
 the horizontal rudder ,,gk having a    
shape like that of the first surface1   
with its ends also turned up1 and       
inclined at a small negative angle with 
this wing surface4 ,along its center is 
a small fin-like vertical rudder that   
steers the device laterally1 like the   
rudder of a ship4  ,the approximately1  

but not exactly1 horizontal rudder      
serves to hold the device in horizontal 
flight1 and its operation can best be   
understood from the side elevation4 ,let
 ,,cd be the wing plane set nearly in   
the line of the stem1 which stem it is  
desired to maintain1 in flying1 at a    
small positive angle1 1 with the        
horizon1  being so chosen that the      
tendency upward given by it will just   
counteract the action of gravity4 ,the  
weight of the aeroplane1 combined with  
the resistance due to the reaction of   
the air caused by its advance would1    
under these conditions1 just keep it    
moving onward in a horizontal line1 if  
there were no disturbance of the        
conditions4 ,there is1 however1 in the  
wing no power of self-restoration to the
 horizontal if these conditions are     
disturbed4 ,but such a power resides in 
the rudder ,,gk1 which is not set       
parallel to the wing1 but at a negative 
angle 7#a7 with it equal to the positive
 angle of the wing with the horizon4 ,it

 is obvious that1 in horizontal flight1 
the rudder1 being set at this angle1    
presents its edge to the wind of advance
 and consequently offers a minimum      
resistance as long as the flight is     
horizontal4 ,if1 however1 for any reason
 the head drops down1 the rear edge of  
the rudder is raised1 and it is at once 
subjected to the action of the air upon 
its upper surface1 which has a tendency 
to lower the rear of the machine and to 
restore horizontality4 ,should the head 
rise1 the lower p#jji surface of the    
rudder is subjected to the impact of the
 air1 the rear end is raised1 and       
horizontality again attained4 ,in       
addition to this1 ,pnaud appears to have
 contemplated giving the rudder-stem a  
certain elasticity1 and in this shape it
 is perhaps as effective a control as   
art could devise with such simple means4
  ,of the flight of his little machine1 
thus directed1 ,pnaud says3   8,if the  
screw be turned on itself #bdj times and
 the whole left free  in a horizontal   

position1 it will first drop2 then1 upon
 attaining  its speed1 rise and perform 
a regular flight at #g or #h feet from  
the  ground for a distance of about #dj 
metres1 requiring about #aa seconds  for
 its performance4 ,some have flown #fj  
metres and have remained  in the air #ac
 seconds4#ab ,the rudder controls the   
inclination to  ascend or descend1      
causing oscillations in the flight4     
,finally the  apparatus descends gently 
in an oblique line1 remaining itself    
horizontal40  ,the motive power is a    
twisted hank of fine rubber strips1     
which weighs #e grammes out of a total  
of #af grammes for the whole machine1   
whose center of gravity should be in    
advance of the center of surface ,,cd1  
as will be demonstrated in another      
place4 ,this device attracted little    
notice1 and ,i was unfamiliar with it   
when ,i began my own first constructions
 at ,allegheny1 in #ahhg4  ,my own      
earliest models employed a light wooden 
frame with two propellers1 which were   

each driven by a strand of twisted      
rubber4#ac ,in later forms1 the rubber  
was enclosed and the end strains taken  
up by the thinnest tin-plate tubes1 or  
better still1 paper tubes strengthened  
by shellac4  ,little was known to me at 
that time as to the proper proportions  
between wing surface1 weight and power2 
and while ,i at first sought to infer   
the relation between wing surface and   
weight from that of soaring birds1 where
 it varies from #a_/b to #a sq4 ft4 of  
wing surface to the pound1 yet the ratio
 was successively increased in the      
earlier models1 until it became #d sq4  
ft4 to #a pound4 ,it may be well to add1
 however1 that the still later          
experiments with the steam-driven       
models1 in which the supporting surface 
was approximately #b sq4 ft4 to the     
pound1 proved that the lack of ability  
of these early rubber-driven models to  
properly sustain themselves even with #d
 sq4 ft4 of wing surface to the pound1  
was largely due to the fact that the    

wings themselves had not been stiff     
enough to prevent their being warped by 
the air pressure generated by their     
forward motion4  ,during the years ,i   
presently describe1 these tentative     
constructions were p#jaj renewed at     
intervals without any satisfactory      
result1 though it became clear from     
repeated failures1 that the motive power
 at command would not suffice1 even for 
a few seconds' flight for models of     
sufficient size to enable a real study  
to be made of the conditions necessary  
for successful flight4  ,in these       
earliest experiments everything had to  
be learned about the relative position  
of the center of gravity1 and what ,i   
have called the center of pressure4 ,in 
regard to the latter term1 it might at  
first seem that since the upward        
pressure of the air is treated as       
concentrated at one point of the        
supporting surface1 as the weight is at 
the center of gravity1 this point should
 be always in the same position for the 

same supporting surface4 ,this relation1
 however1 is never constant4 ,how       
paradoxical seems the statement that1 if
 ab be such a supporting surface in the 
form of a plane of uniform thickness and
 weight1 suspended at c 7ac being       
somewhat greater than cb7 and subjected 
to the pressure of a wind in the        
direction of the arrow1 the pressure on 
the lesser arm cb will overpower that on
 the greater arm ac6 ,we now know1      
however1 that this must be so1 and why1 
but as it was not known to the writer   
till determined by experiments published
 later in 8,experiments in              
,aerodynamics10 all this was worked out 
by trial in the models4  ,illustration3 
,,fig4 #a4 ,diagram of suspended plane  
showing position of ,c4 ,p4  ,it was    
also early seen that the surface of     
support could be advantageously divided 
into two1 with one behind the other1 or 
one over the other1 and this was often1 
though not always1 done in the models4  
,at the very beginning another          

difficulty was met which has proved a   
constant and ever-increasing one with   
larger models--the difficulty of        
launching them in the air4 ,it is       
frequently proposed by those unfamiliar 
with this difficulty1 to launch the     
aerodrome by placing it upon a platform 
car or upon the deck of a steamer1 and  
running the car or boat at an increasing
 speed until the aerodrome1 which is    
free to rise1 is lifted by the wind of  
advance4 ,but this is quite             
impracticable without means to prevent  
premature displacement1 for the large   
surface and slight weight renders any   
model of considerable size unmanageable 
in the least wind1 such as is always    
present in the open air4 ,it is1        
therefore1 necessary in any launching   
apparatus that the aerodrome be held    
rigidly until the very moment of        
release1 and that instant and           
simultaneous release from the apparatus 
be made at all the sustaining points at 
the proper moment4 p#jaa  ,there is but 

a very partial analogy in this case to  
the launching of a ship1 which is held  
to her ways by her great weight4 ,here1 
the 8ship0 is liable to rise from her   
ways or be turned over laterally at any 
instant1 unless it is securely fastened 
to them in a manner to prevent its      
rising1 but not to prevent its          
advancing4  ,the experiments with       
rubber-driven models commenced in       
,april1 #ahhg1 at the ,allegheny        
,observatory1 were continued at         
intervals 7partly there1 but chiefly in 
,washington7 for three or four years1   
during which time between thirty and    
forty independent models were           
constructed1 which were so greatly      
altered in the course of experiment that
 more nearly one hundred models were in 
reality tried4 ,the result of all this  
extended labor was wholly inconclusive1 
but as subsequent trials of other motors
 7such as compressed air1 carbonic-acid 
gas1 electric batteries1 and the like7  
proved futile1 and 7before the steam    

engine7 only the rubber gave results1   
however unsatisfactory1 in actual       
flight1 from which anything could be    
learned1 ,i shall give some brief       
account of these experiments1 which     
preceded and proved the necessity of    
using the steam engine1 or other like   
energetic motor1 even in experimental   
models4  ,an early attempt was made in  
,april1 #ahhg1 with a model consisting  
of a frame formed of two wooden pieces1 
each about #a metre long and #d         
centimetres wide1 made for lightness1 of
 star-shaped section1 braced with       
cross-pieces and carrying two long      
strips of rubber1 each about #a mm4     
thick1 #cj mm4 wide1 #b metres long1    
doubled1 weighing #cjj grammes4 ,each of
 these strips could be wound to about   
#cjj turns1 one end being made fast to  
the front of the frame1 the other to the
 shaft of a four-bladed propeller #cj   
cm4 in diameter4 ,the wings were made of
 lightest pine frames1 over which paper 
was stretched1 and were double1 one     

being superposed upon the other4 ,each  
was #ae cm4 wide1 and #abj cm4 long4    
,the distance between them was #ab cm4  
and the total surface a little more than
 #cfjj sq4 cm4 7#d square feet74 ,in    
flying1 the rubber was so twisted that  
the propellers were run in opposite     
directions4 ,the weight of the whole    
apparatus was not quite #a kilogramme1  
or about #a pound to #b feet of         
sustaining surface1 which proved to be  
entirely too great a weight for the     
power of support4 ,when placed upon the 
whirling-table1 it showed a tendency to 
soar at a speed of about ten miles an   
hour1 but its own propellers were       
utterly insufficient to sustain it4  ,in
 this attempt1 which was useful only in 
showing how much was to be learned of   
practical conditions1 the primary       
difficulty lay in making the model light
 enough and sufficiently strong to      
support its power4 ,this difficulty     
continued to be fundamental through     
every later form2 but besides this1 the 

adjustment of the center of gravity to  
the center of pressure of the wings1 the
 disposition of the wings themselves1   
the size of the propellers1 the         
inclination and number of their blades1 
and a great number of other details1    
presented themselves for examination4   
p#jab ,even in the first model1 the     
difficulty of launching the machine or  
giving it the necessary preliminary     
impulse was disclosed--a difficulty     
which may perhaps not appear serious to 
the reader1 but which in fact required  
years of experiment to remove4  ,by     
,june1 #ahhg two other models1 embodying
 various changes that had suggested     
themselves1 had been constructed4 ,each 
of these had a single propeller 7one an 
#ah-a_/b-;inch propeller with eight     
adjustable blades1 the other a #bd-;inch
 propeller with four adjustable blades7 
and was sustained by two pairs of curved
 wings #d feet #g inches long4 ,it is1  
however1 unnecessary to dwell further on
 these details1 since these models also 

proved altogether too heavy in relation 
to their power1 and neither of them ever
 made an actual flight4  ,at this period
 my time became so fully occupied with  
the experiments in aerodynamics 7which  
are not here in question7 that during   
the next two years little additional was
 done in making direct investigations in
 flight4  ,in ,june1 #ahhi1 however1 new
 rubber-driven models were made in which
 the wooden frames were replaced by     
tubes of light metal1 which1 however1   
were still too heavy1 and these         
subsequently by tubes of paper covered  
with shellac1 which proved to be the    
lightest and best material in proportion
 to its strength that had been found4   
,the twisted rubber was carried within  
these tubes1 which were made just strong
 enough to withstand the end-strain it  
produced4 ,the front end of the rubber  
being made fast to an extremity of the  
tube1 the other end was attached        
directly to the shaft of the propeller1 
which in the early models was still     

supplied with four blades4  ,a detailed 
description of one of these early       
models1 ,no4 #bf1 shown in ,plates #a   
and #d1 follows3  ,in each of the two   
tubes of paper1 stiffened with shellac1 
which form a part of the framing1 is    
mounted a hank of twisted rubber1 which 
connects with a propeller at the rear4  
,there are two pairs of wings1          
superposed and inclined at an angle1 the
 one above1 the other below the frame4  
,a light stem connected with the frame  
bears a triangular ,pnaud tail and      
rudder4   ,length of model              
#aje  cm4  ,spread of wings             
#hc     ,width of upper wings           
#ad     ,width of lower wings           
#ai     ,diameter of propeller          
#bi     ,area of upper wings            
#aacd sq4 cm4  ,area of lower wings     
#aedh      ,area of tail                
#add      ,weight of wings              
#ea grammes  ,weight of tail            
#g     ,weight of frame                 
#ch     ,weight of wheels               

#bj     ,weight of rubber 74#ji pound7  
#dj     ,total weight                   
#aef     ,no4 of turns of rubber        
#ajj  ,time of running down             
#h seconds  ,horse-power from preceding 
data      #j4jja ,,hp   ,the aerodromes 
made at this time were too heavy1 as    
well as too large1 to be easily launched
 by hand1 and it was not until #ahia    
that the first one was constructed light
 enough to actually fly4 ,this first    
flight was obtained from the north      
window of the dome of the ,allegheny    
,observatory1 on ,march #bh1 #ahia1 and 
imperfect as it was1 served to show that
 the proper balancing of the aerodrome  
which would bring the center of gravity 
under the center of pressure1 so as to  
give a horizontal flight1 had yet to be 
obtained4  ,from this time on until     
#ahic1 experiments continued to be made 
with rubber-driven models1 of which1 as 
has been stated1 nearly #dj were        
constructed1 some with two propellers1  
some with one2 some with one propeller  

in front and one behind2 some with      
plane1 some with curved1 wings2 some    
with single1 some with superposed1      
wings2 some with two pairs of wings1 one
 preceding and one following2 some with 
the ,pnaud tail2 and some with other    
forms4 ,a few of these early forms are  
indicated on the accompanying ,plates #a
 to #d1 but it does not seem necessary  
to go into the details of their         
construction4   ,no4 #aa with which an  
early flight was made1 closely resembles
 the  ,pnaud model4   ,no4 #ac has two  
propellers1 one in front and one behind1
 with a  single wing4   ,no4 #ad has two
 propellers1 nearly side by side1 but   
one slightly in  advance1 with a single 
wing and a flat horizontal tail4   ,no4 
#ae has one leading propeller and two   
broad wings1 placed one  behind the     
other4   ,no4 #cj has the propeller     
shafts at an angle1 and one pair of     
wings4   ,no4 #ca has the propeller     
shafts at an angle1 and two pairs of    
wings  superposed4  ,the wings in       

general were flat1 but in some cases    
curved4 ,the rubber was usually wound to
 about #ajj turns1 and trouble          
continually arose from its 8kinking0 and
 unequal unwinding1 which often caused  
most erratic flights4  ,it is sufficient
 to say of these that1 rude as they     
were1 much was learned from them about  
the condition of the machines in free   
air1 which could never be learned from  
the whirling-table or other constrained 
flight4  ,the advantages and also the   
dangers of curved wings as compared with
 plane ones1 were shown1 and the general
 disposition which would secure an even 
balance1 was ascertained2 but all this  
was done with extreme difficulty1 since 
the brief flights were full of          
anomalies1 arising from the imperfect   
conditions of observation4 ,for         
instance1 the motor power was apparently
 exhausted more rapidly when the        
propellers were allowed to turn with the
 model at rest1 than when it was in     
motion1 though in theory1 in the latter 

case more power would seem to be        
expended and a greater speed of         
revolution obtained in a given time4    
,the longest flights obtainable did not 
exceed #f or #h seconds in time1 nor #hj
 to #ajj feet in distance1 and were not 
only so brief1 but1 owing to the        
spasmodic action of the rubber and other
 causes1 so irregular1 that it was      
extremely difficult to obtain even the  
imperfect results which were actually   
deduced from them4 p#jad                
,,abbreviations ,,and ,,symbols         
,,employed  ,the following rules and    
symbols were adopted for determining the
 relative position of points on the     
aerodrome1 some of them during #ahia1   
and some of them since4 ,all are given  
here for convenience of reference1      
though their chief application is to the
 larger steam aerodromes described      
later4 ,those which immediately follow  
were meant to give some of the notation 
of descriptive geometry in untechnical  
language for the use of the workmen     

employed4 ,let ,x1 ,y and ,z be three   
lines at right angles to each other1 and
 passing through the same point in      
space1 ,o1 lying at any convenient      
distance above the floor of the         
work-shop4 ,the line ,x lies ,north and 
,south2 the line ,y lies ,east and      
,west1 and the line ,z points to the    
zenith4 ,now place the aerodrome on the 
floor so that its principal axis lies   
horizontally in the plane ,,xz1 with its
 head pointing ,north1 and in such a    
position that a line passing through the
 center of the propellers shall coincide
 with the line ,y4  ,illustration3      
,,fig4 #b4 ,diagram showing mensural    
coordinates4  ,when measurements are    
made on or parallel to the line ,x1 the 
point of intersection ,o will be marked 
#aejj centimetres1 and distances toward 
the ,south will be less than1 and       
distances toward the ,north greater than
 #aejj centimetres4  ,when measurements 
are made on or parallel to the line ,z1 
the point ,o will be considered to be   

marked #bejj centimetres1 and distances 
above will be greater than1 and         
distances below will be less than #bejj 
centimetres4 p#jae  ,lastly1 when       
measurements are made on or parallel to 
the line ,y1 the point ,o will be marked
 #cejj centimetres1 and distances toward
 the ,east will be greater than1 and    
distances toward the ,west will be less 
than #cejj centimetres4 ,measurements in
 these latter directions will be        
comparatively infrequent because the    
center of gravity and center of pressure
 both lie in the plane ,,xz4            
,,example  ,in the figure the point ,t  
in the tail1 if #ae centimetres to the  
,south of ,o1 would be graduated #adhe  
centimetres4 ,a weight 7,w7 #be         
centimetres below the axis1 would be    
graduated #bdge centimetres4 ,a point   
#ej centimetres above the axis would be 
graduated #beej centimetres1 etc4  ,,cg 
represents the ,center of ,gravity of   
the aerodrome1 or 7with subscript       
letters7 of any specially designated    

part1 or with reference to some         
indicated condition4  ,,cg#a ,,cg#b     
represent the ,center of ,gravity as    
referred to the first1 or horizontal1   
and to the second1 or vertical plane1   
respectively4  ,,cp represents the      
,center of ,pressure#ad of the whole    
aerodrome1 or 7with a subscript7 of any 
specially designated part4  ,,cf        
represents the ,center of ,figure of the
 aerodrome1 or of any specially         
designated part4  ,subscripts3   8fw0   
refers to the front wings4        8#a0  
refers to the plane ,,xy4  8rw0 refers  
to the rear wings4         8#b0 refers  
to the plane ,,xz4  8r0  refers to a    
state of rest4        8#c0 refers to the
 plane ,,yz4  8m0  refers to a state of 
motion4  8,a0 represents the total area 
of the supporting surface2 8a0          
represents the total area of the tail2  
,,hp represents the horse-power by      
,prony brake measurement4 8,horse-power 
by formula0 is given by ,maxim's        
formula3#ae               rev4diam4 of  

propellerpitchthrust  ,,hp              
------------------------------------4   
#cc1jjj  7,this formula was not in use  
at the time of the rubber-motor         
experiments1 for which the thrust was   
not taken4 ,it appears to assume the    
conditions where the screws from a fixed
 position move a mass of still air1 are 
the same as those of free flight4 ,its  
results1 however1 are in better         
agreement with experiment than might be 
anticipated47  8,flying-weight0 means   
everything borne in actual flight1      
including fuel and water4 p#jaf         
,remembering that the principal object  
of all these experiments is to be able  
to predict that setting of the wings and
 tail with reference to the center of   
gravity which will secure horizontal    
flight1 we must understand that in the  
following tables 7see ,no4 #cj7 the     
figures ,,cpm  #aeaf4e cm4 mean a       
prediction that the center of pressure  
of the sustaining surfaces in motion    
7,,cpm7 is to be found in a certain     

position #aeaf4e2 that is1 #af4e cm4 in 
advance of the line joining the         
propeller shafts4 ,this prediction has  
been made by means of previous          
calculation joined with previous        
experimental adjustment4 ,we know in a  
rough way where the ,,cp will fall on   
the wings when they are exposed         
independently if flat1 and at a certain 
angle1 and where it will fall on the    
tail4 ,from these1 we can find where the
 resulting ,,cp of the whole sustaining 
surface will be4  ,it would seem that   
when we have obtained the center of     
gravity by a simple experiment1 we have 
only to slide the wings or tail forward 
and back until the 7calculated7 center  
of pressure falls over this observed    
center of gravity4 ,but in the very act 
of so adjusting the wings and tail1 the 
center of gravity is itself altered1 and
 the operation has to be several times  
repeated in order to get the two values 
7the center of pressure and center of   
gravity7 as near each other as they are 

found in the above-mentioned table1 our 
object being to predict the position    
which will make the actual flight itself
 horizontal4 ,how far this result has   
been obtained1 experiment in actual     
flight alone can show1 and from a       
comparison of the prediction with the   
results of observation1 we endeavor to  
improve the formula4  ,the difficulties 
of these long-continued early           
experiments were enhanced by the        
ever-present difficulty which continued 
through later ones1 that it was almost  
impossible to build the model light     
enough to enable it to fly1 and at the  
same time strong enough to withstand the
 strains which flight imposed upon it4  
,the models were broken up by their     
falls after a few flights1 and had to be
 continually renewed1 while owing to the
 slightness of their construction1 the  
conditions of observation could not be  
exactly repeated2 and these flights     
themselves1 as has already been stated1 
were so brief in time 7usually less than

 six seconds71 so limited in extent     
7usually less than twenty metres71 and  
so wholly capricious and erratic1 owing 
to the nature of the rubber motor and   
other causes1 that very many experiments
 were insufficient to eliminate these   
causes of mal-observation4  ,it is not  
necessary to take the reader through    
many of them1 but not to pass over      
altogether a labor which was so great in
 proportion to the results1 but whose   
results1 such as they were1 were the    
foundation of all after knowledge1 ,i   
will1 as illustrations1 take from an    
almost unlimited mass of such material  
the observations of ,november #bj1      
#ahia1 which were conducted with ,model 
,no4 #cj with a single pair of wings1   
shown in ,plate #a1 and with another    
one1 ,no4 #ca1 also shown p#jah in      
,plate #a1 with superposed wings1 which 
was used for the purpose of comparison4 
,s4 ,p4 ,langley was the observer1 the  
place of observation the larger upper   
hall of the ,smithsonian building1 at   

,washington1 the time being taken by a  
stop-watch1 and the distance by a scale 
laid down upon the floor4 ,the models   
were in every case held by an assistant 
and launched by hand1 being thrown off  
with a slight initial velocity4 ,in the 
case of ,no4 #cj1 the preliminary       
calculation of the position of the      
center of pressure had been made by the 
process already described2 the center of
 gravity1 with reference to the         
horizontal plane1 was determined by     
simply suspending the whole by a cord4  
,illustration3 ,,pl4 #a                 
,,rubber-,,motor ,,model ,,aerodromes   
,,nos4 #aa1 #ac1 #ad1 #ae1 #bf1 #cj1 #ca
  ,illustration3 ,,pl4 #b               
,,rubber-,,motor ,,model ,,aerodromes   
,,nos4 #aa1 #ac1 #ad  ,illustration3    
,,pl4 #c  ,,rubber-,,motor ,,model      
,,aerodromes ,,nos4 #ae1 #bd            
,illustration3 ,,pl4 #d                 
,,rubber-,,motor ,,model ,,aerodrome    
,,no4 #bf    ,,observation ,,of         
,,november #bj1 #ahia4  ,,observer1 ,s4 

,p4 ,l4  ,,locality1 ,,upper ,,hall1    
,,smithsonian ,,building4               
----------------------------------------
----------------------------            
,no4 #cj4                 ,no4 #ca4     
,single wings4         ,superposed      
wings4                                  
----------------------------------------
---------------------------- ,,cpm      
#aeaf4e cm4 ,,cg#a                      
#aeae cm4              #aeag cm4 ,,cfw  
#aebh cm4 ,length 7without fender7      
#abj cm4  #c4id ft4    #abj cm4  #c4id  
ft4 ,width over wing tips      #abj cm4 
#c4id ft4    #abj cm4  #c4id ft4 ,weight
 of rubber 7#gb   grammes in each tube7 
#add gr4  #j4cb lbs4   #add gr4  #j4cb  
lbs4 ,total flying weight   7including  
tail7        #dcb gr4  #j4ie lbs4   #ejf
 gr4  #a4aa lbs4 ,turns of rubber       
#cj                    #cj    ,diameter 
of propellers     #cg cm4  #a4ba ft4    
#cg cm4  #a4ba ft4 ,width of propellers 
#g cm4  #j4bc ft4      #g cm4  #j4bc ft4
 ,pitch of propellers        #ej cm4    

#a4fd ft4     #ej cm4  #a4fd ft4        
,each pair #aihd sq4 cm4 ,area of wings 
7each      #aihd sq4 cm4                
#b4ac sq4 ft4   #iib sq4 cm47           
#b4ac sq4 ft4    ,total #cifh sq4 cm4   
#d4bf sq4 ft4  ,area of tail            
#cgc sq4 cm4           #cgc sq4 cm4     
#j4dj sq4 ft4         #j4dj sq4 ft4     
----------------------------------------
----------------------------  ,area of  
wings and tail in ,no4 #cj1 #bceg sq4   
cm4  #b4ec sq4 ft4    #b4ec sq4 ft4     
4#ie  #b4g4 ,therefore1 there are #b4g  
or nearly    #c square feet of          
sustaining area to the pound4           
----------------------------------------
----------------------------            
,flight4,aerodrome4                     
,results4                               
----------------------------------------
----------------------------    #a      
,no4 #cj    ,with #cj turns of the      
rubber1 flew low through                
#aj metres4     #b      ,no4 #cj        
,flew heavily through #ab metres4     #c

      ,no4 #ca    ,flew high and turned 
to left2 distance not noted4     #d     
,no4 #ca    ,the right wing having been 
weighted 7to depress it                 
and correct the tendency to turn to the 
left71                       model flew 
high1 but the rubber ran down when it   
had obtained a flight of #aj metres4    
#e      ,no4 #ca    ,the wings were     
moved backward until the ,,cp           
stood at #adic4 ,the model still turned 
to the left2                            
flight lasted three and a-half seconds2 
distance                       not      
noted4     #f      ,no4 #ca    ,vertical
 tail was adjusted so as to further     
increase                       the      
tendency to go to the right4 ,in spite  
of all                       this1 the  
model turned sharply to the left1 flying
                       with a nearly    
horizontal motion2 time of flight       
not noted2 distance not noted4     #g   
,no4 #cj    ,straight horizontal flight2
 time three and                         

three-fifth seconds1 when rubber ran    
down2                       distance #ac
 metres4     #h      ,no4 #cj           
,straight flight as before2 time two and
 four-fifth                             
seconds2 distance #ac metres4     #i    
,no4 #cj    ,with a curved wing in the  
same position as the flat               
wing had previously occupied1 model flew
 up and                       struck the
 ceiling 7nearly #cj feet high71 turning
                       to right1 with a 
flight whose curtate length was         
#aj metres4     #aj     ,no4 #cj        
,wing having been carried back #e       
centimetres1 model                      
still flew up1 but not so high1 and     
still turned                       to   
the right4     #aa     ,no4 #cj         
,wings carried back #e centimetres more2
 model still                       flew 
high2 time two and two-fifths seconds2  
distance #ac metres4     #ab     ,no4   
#cj    ,wings carried back #d           
centimetres more2 model still           

flew high during a flight of #ac metres4
                                        
----------------------------------------
----------------------------  ,the      
observations now ceased1 owing to the   
breaking up of the model4  ,the objects 
of these experiments1 as of every other1
 were to find the practical conditions  
of equilibrium and of horizontal flight1
 and to compare the calculated with the 
observed positions of the center of     
pressure4 ,they enable us to make a     
comparison of the performances given by 
earlier ones with a light rubber motor1 
with the relatively heavy motors used   
to-day1 as well as a comparison of      
single flat1 single curved1 and         
superposed flat wings4  ,the average    
time of the running down of the rubber  
in flight was something like three      
seconds1 while the average time of its  
running down when standing still was but
 one and a half seconds4 ,it might have 
been expected from theory that it would 
take longer to run down when stationary1

 than in flight1 and this was one of the
 many anomalies observed1 whose         
explanation was found later in the      
inevitable defects of such apparatus4   
,the immediate inferences from the day's
 work were3  #a4 ,that the calculated   
position of the ,,cp at rest1 as related
 to the ,,cg1 is trustworthy only in the
 case of the plane wing4  #b4 ,the      
formula altogether failed with the      
curved wing1 for which the ,,cp had to  
be carried indefinitely further         
backward4  ,on comparing the previous   
flights of ,november #ad1 with these1 it
 seems that with the old rubber motor of
 #ce grammes and #ej turns1 the single  
wing1 either plane or curved1 is        
altogether inferior to the double wing2 
while with the increased motor power of 
this day1 the single wing1 whether plane
 or curved1 seems to be as good as the  
double wing4 ,it also seems that the    
curved wing was rather more efficient   
than the plane one4  ,the weight of the 
rubber in each tube was #gb grammes1 or 

#j4af pounds2 mean speed of flight in   
horizontal distance #d-a_/b metres      
7about #ae feet7 per second4#af  ,from  
experiments already referred to1 there  
were found available #cjj foot-pounds of
 energy in a pound of rubber as         
employed1 and in #j4af of a pound1 #dh  
foot-pounds of energy were used2        
#dh_/cc1jjj or #j4jjade  the horse-power
 exerted in p#jai one minute1 but as the
 power was in fact expended in #a_/bj of
 that time we have #bjj4jjade  #j4jbi2  
that is1 during the brief flight1 about 
#j4jc of a horse-power was exerted1 and 
this sustained a total weight of only   
about a pound4  ,in comparing this      
flight with the ideal conditions of     
horizontal flight in 8,aerodynamics10 it
 will be remembered that this model's   
flight was so irregular and so far from 
horizontal1 that in one case it flew up 
and struck the lofty ceiling4 ,the angle
 with the horizon is1 of course1 so     
variable as to be practically unknown1  
and therefore no direct comparison can  

be instituted with the data given on    
page #ajg of 8,experiments in           
,aerodynamics10 but we find from these  
that at the lowest speed there given of 
about #ce feet per second1 #j4jc of a   
horse-power exerted for three seconds   
would carry nearly one pound through a  
distance of somewhat over #ajj feet in  
horizontal flight4  ,the number of turns
 of the propellers multiplied by the    
pitch corresponds to a flight of about  
#af metres1 while the mean actual flight
 was about #ab4 ,it is probable1        
however1 that there was really more slip
 than this part of the observation would
 indicate4 ,it was also observed that   
there seemed to be very little          
additional compensatory gain in the     
steering of ,no4 #cj for the weight of  
the long rudder-tail it carried4 ,it may
 be remarked that in subsequent         
observations the superiority of the     
curved wing in lifting power was        
confirmed1 though it was found more     
liable to accident than the flatter one1

 tending to turn the model over unless  
it was very carefully adjusted4  ,it may
 also be observed that these and        
subsequent observations show1 as might  
have been anticipated1 that as the motor
 power increased1 the necessary wing    
surface diminished1 but that it was in  
general an easier and more efficient    
employment of power to carry a surface  
of four feet sustaining area to the     
pound than one of three1 while one of   
two feet to the pound was nearly the    
limit that could be used with the rubber
 motor4#ag  ,it may be remarked that the
 flights this day1 reckoned in          
horizontal distance1 were exceptionally 
short1 but that the best flights at     
other times obtained with these models  
7#cj and #ca7 did not exceed #be metres4
 ,such observations were continued in   
hundreds of trials1 without any much    
more conclusive results4 p#jbj  ,the    
final results1 then1 of the observations
 with rubber-driven models 7which were  
commenced as early as #ahhg1 continued  

actively through the greater portion of 
the year #ahia and resumed1 as will be  
seen later1 even as late as #ahie71 were
 not such as to give information        
proportioned to their trouble and cost1 
and it was decided to commence          
experiments with a steam-driven         
aerodrome on a large scale4   p#jba     
,,chapter ,,iii  ,,available ,,motors   
,in the introductory chapter to         
8,experiments in ,aerodynamics10 it was 
asserted that   8,these researches have 
led to the result that mechanical       
sustentation of heavy bodies in the air1
 combined with very great  speeds1 is   
not only possible1 but within the reach 
of mechanical  means we actually        
possess40  ,it was1 however1 necessary  
to make a proper selection in order to  
secure that source of power which is    
best adapted to the requirements of     
mechanical flight4 ,pnaud had used india
 rubber as the cheapest and at the same 
time the most available motor for the   
toys with which he was experimenting1   

but when models were constructed that   
were heavier than anything made prior to
 #ahhg1 it appeared1 after the          
exhaustive trials with rubber referred  
to in the preceding chapter1 that       
something which could give longer and   
steadier flights must be used as a      
motor1 even for the preliminary trials1 
and the construction of the large       
steam-driven model known as ,no4 #j1 and
 elsewhere described1 was begun4 ,even  
before the completion of this1 the      
probability of its failure grew so      
strong that experiments were commenced  
with other motors1 which it was hoped   
might be consistent with a lighter      
construction4  ,these experiments which 
commenced in the spring of #ahib and    
continued for nearly a twelvemonth1 were
 made upon the use of compressed air1   
carbonic-acid gas1 electricity in       
primary and storage batteries1 and      
numerous other contrivances1 with the   
result that the steam engine was finally
 returned to1 as being the only one that

 gave any promise of immediate success  
in supporting a machine which would     
teach the conditions of flight by actual
 trial1 though it may be added that the 
gas engine which was not tried at this  
time on account of engineering          
difficulties1 was regarded from the     
first as being the best in theory and   
likely to be ultimately resorted to4    
,all others were fundamentally too      
heavy1 and weight was always the        
greatest enemy4  ,it is the purpose of  
this chapter to pass in brief review the
 work that was done and the amount of   
energy that was obtained with these     
several types of motors1 as well as the 
obstacles which they presented to       
practical application upon working      
aerodromes4    ,,india ,,rubber  ,india 
rubber is the source of power to which  
the designer of a working model         
naturally turns1 where it is desirable  
that it shall be1 above all1 light and  
free from the necessity of using        
complicated mechanism4 ,rubber motors   

were1 p#jbb therefore1 used on all of   
the earlier models1 and served as the   
basis of calculations made to determine 
the amount of power that would be       
required to propel aerodromes with other
 sources of energy4  ,some of the       
disadvantages inherent in the use of    
rubber are at once apparent1 such as the
 limited time during which its action is
 available1 the small total amount of   
power1 and the variability in the amount
 of power put forth in a unit of time   
between the moment of release and the   
exhaustion of the power4 ,in addition1  
serious1 though less obvious            
difficulties1 present themselves in     
practice4  ,there are two ways in which 
rubber can be used2 one by twisting a   
hank of strands1 and1 while one end is  
held fast1 allowing the other to        
revolve2 the other1 by a direct         
longitudinal stretching of the rubber1  
one end being held fast and the other   
attached to the moving parts of the     
mechanism4 ,the former method was       

adopted by ,pnaud1 and was also used in 
all of my early constructions1 but while
 it is most convenient and simple in its
 7theoretical7 application1 it has1 in  
addition to the above drawbacks1 that of
 knotting or kinking1 when wound too    
many turns1 in such a way as to cause   
friction on any containing tube not made
 impracticably large1 and also that of  
unwinding so irregularly as to make the 
result of one experiment useless for    
comparison with another4  ,in #ahie1    
some experiments were made in which the 
latter method was used1 but this was    
found to involve an almost impracticable
 weight1 because of the frame 7which    
must be strong enough to withstand the  
end pull of the rubber7 and the         
mechanism needed to convert the pull    
into a movement of rotation4  ,as the   
power put forth in a unit of time       
varies1 so there is a corresponding     
variation according to the original     
tension to which the rubber is          
subjected4 ,thus in some experiments    

made in #ahhi with a six-bladed         
propeller #ah4h inches in diameter1     
driven by a rubber spring #a4c inches   
wide1 #j4ab inch thick and #c feet long1
 doubled1 and weighing #j4ch pound1 the 
following results were obtained3        
,number of twists of rubber          #ej
           #ge          #ajj  ,time     
required to run down            #g sec4 
#aj sec4      #ab sec4  ,foot-pounds    
developed             #cg4e             
#fc4j        #abd4f  ,foot-pounds       
developed per min4   #cba4d             
#cgh4j        #fbc4j  ,horse-power      
developed           #j4jjig             
#j4jaae       #j4jahi  ,thus we see     
that1 with twice the number of turns1   
more than three times the amount of work
 was done and almost twice the amount of
 power developed1 giving as a maximum   
for this particular instance #cbh       
foot-pounds per pound of rubber4  ,the  
usual method of employing the twisted   
rubber was to use a number of fine      
strands formed into a hank looped at    

each end4 ,one of these hanks1          
consisting of #afb single or #ha double 
strands of rubber1 and weighing #gc     
grammes1 when given #ea turns developed 
#ee foot-pounds of work1 which was put  
out in #d seconds4 ,this corresponds to 
#j4ja horse-power per minute for one    
pound of rubber4 p#jbc  ,the results of 
a large number of tests show that one   
pound of twisted rubber can put forth   
from #dej to #ejj or more foot-pounds of
 work1 but at the cost of an overstrain1
 and that a safe working factor can     
hardly be taken at higher than #cjj     
foot-pounds1 if we are to avoid the     
8fatigue0 of the rubber1 which otherwise
 becomes as marked as that of a human   
muscle4  ,while twisting is an          
exceedingly convenient form of          
application of the resilience of rubber 
to the turning of propelling wheels1 the
 direct stretch is1 as has been         
remarked1 much more efficient in        
foot-pounds of energy developed by the  
same weight of rubber4 ,it was found    

that rubber could not1 without undue    
8fatigue10 be stretched to more than    
four and a half times its original      
length1 though experiments were made to 
determine the amount of work that a     
rubber band1 weighing one pound1 was    
capable of doing1 the stretching being  
carried to seven times its original     
length4 ,the results varied with the    
rubber used and the conditions of       
temperature under which the experiments 
were tried1 ranging from #aedc          
foot-pounds to #bfjj foot-pounds4 ,the  
tests led to the conclusion that1 for   
average working1 one pound of rubber so 
stretched1 is capable of doing #bjjj    
foot-pounds of work1 but1 owing to the  
weight of the supporting frame and of   
the mechanism1 this result can be       
obtained only under conditions          
impracticable for a flying machine4 ,in 
the more practicable twisted form it    
furnishes1 as has been said1 less than a
 fifth of that amount4  ,the conclusions
 reached from these experiments are3    

#a4 ,the length of the unstretched      
rubber remaining the same1 the          
sustaining power will be directly       
proportional to the weight of rubber2   
#b4 ,with a given weight of rubber1 the 
end strain is inversely proportional to 
the length of the unstretched rubber2   
#c4 ,with a given weight of rubber1 the 
work done is constant1 whatever the     
form2 hence if we let w  the work in    
foot-pounds1 g  the weight of the rubber
 in pounds1 and k  a constant taken at  
#bjjj as given above1 we have   w  kg   
#bjjj g foot-pounds4  ,this is for an   
extension of seven units of length1 so  
that for a unit of extension we would   
have approximately   w  #cjj g          
foot-pounds  which for four units of    
extension corresponds very closely to   
the #acjj foot-pounds which ,pnaud      
claims to have obtained4  #d4 ,the end  
strain varies with the cross-section for
 a given unit of extension4  ,these     
results can lead to but one conclusion2 
that for the development of the same    

amount of power when that amount shall  
be #a horse-power or more1 rubber weighs
 enormously more than a steam engine1   
besides being less reliable p#jbd for a 
sustained effort1 and1 therefore1 cannot
 be used for propelling aerodromes      
intended for a flight that is to be     
prolonged beyond a few seconds4#ah  ,it 
may be desirable to present a tabular   
view of the theoretical energy of       
available motors1 which it will be      
noticed is a wholly different thing from
 the results obtained in practice4      
,thus1 we represent the weight of rubber
 only1 without regard to the weight of  
the frame required to hold it4 ,in the  
steam engine1 we consider the           
theoretical efficiency per pound of     
fuel1 without regarding the enormous    
waste of weight in water in such small  
engines as these1 or the weight of the  
engine itself4 ,we treat the hot-water  
engine in like manner1 and in regard to 
carbonic acid and compressed air1 we    
take no note of the weight of the       

containing vessel1 or of the cylinders  
and moving parts4 ,in the same way we   
have the theoretical potency of         
electricity in primary and storage      
batteries1 without counting the weight  
of the necessary electromotors2 and of  
the inertia-engine without discussing   
that of the mechanism needed to transmit
 its power4  ,foot-pounds of energy in  
one pound of   ,gasoline                
#ae1fbe1bhj   ,alcohol                  
#i1gba1hjf   ,gunpowder                 
#ifj1jjj   ,hot water1 under pressure of
 #ajj atmospheres                       
#chc1gab   ,air1 under pressure of #ajj 
atmospheres1 isothermal    expansion    
#abj1ehd   ,liquid carbonic acid1 at    
temperature of #cj and pressure    of   
#ajj atmospheres                        
#gh1hjj   ,electric battery2            
short-lived1 thin walled2 chromic acid  
and platinum                            
#ge1jjj   ,steel ring1 #h inches in     
diameter1 at speed of #cjjj turns    per
 minute                                 

#ai1jjj   ,storage battery              
#ag1efj   ,rubber1 pulled               
#b1jjj   ,rubber1 twisted               
#cjj  ,it may be interesting to consider
 next1 in even a roughly approximate    
way1 what may be expected from these    
various sources of energy in practice4  
,,steam ,,engine  ,the steam engine on a
 small scale1 and under the actual      
restrictions of the model1 must         
necessarily be extremely wasteful of    
power4 ,if we suppose it to realize #b  
per cent of the theoretical energy      
contained in the fuel1 we shall be      
assuming more than was actually         
obtained4 ,the energy of the fuel cannot
 be obtained at all1 of course1 without 
boiler and engine1 whose weight1 for the
 purpose of the following calculation1  
must be added to that of the fuel2 and  
if we suppose the weight of the boilers1
 engines and water1 for a single        
minute's flight1 to be collectively ten 
pounds1 we shall take an optimistic view
 of what may be expected under ordinary 

conditions4 ,we have in this view       
#a_/ejj of the p#jbe theoretical        
capacity possibly realizable under such 
conditions1 but if we take #a_/ajjj we  
shall probably be nearer the mark4 ,even
 in this case we have1 when using       
gasoline as fuel1 #ae1fbe foot-pounds   
per minute1 or nearly #j4ej horse-power1
 as against 4#jjia horse-power in the   
case of the rubber1 so that even with   
this waste and with the weight of the   
engines necessary for a single minute's 
service1 the unit weight of fuel        
employed in the steam engine gives #ee  
times the result we get with rubber4    
,illustration3 ,,pl4 #e  ,,rubber-,,pull
 ,,model ,,aerodrome  ,illustration3    
,,pl4 #f  ,,rubber-,,pull ,,model       
,,aerodrome  ,illustration3 ,,pl4 #g    
,,rubber-,,pull ,,model ,,aerodrome     
,illustration3 ,,pl4 #h  ,,rubber-,,pull
 ,,model ,,aerodrome  ,illustration3    
,,pl4 #i  ,,rubber-,,pull ,,model       
,,aerodrome  ,with alcohol we have about
 #b_/c the result that is furnished by  

gasoline1 since nearly the same boiler  
and engine will be used in either case4 
,certain difficulties which at first    
appeared to be attendant on the use of  
gasoline on a small scale induced me to 
make the initial experiments with       
alcohol4 ,this was continued because of 
its convenience during a considerable   
time1 but it was finally displaced in   
favor of gasoline1 not so much on       
account of the superior theoretical     
efficiency of the latter1 as for certain
 practical advantages1 such as its      
maintaining its flame while exposed to  
wind1 and like considerations4          
,,gunpowder  ,although there are other  
explosives possessing a much greater    
energy in proportion to their weight    
than gunpowder1 this is the only one    
which could be considered in relation to
 the present work1 and the conclusion   
was finally reached that it involved so 
great a weight in the containing        
apparatus and so much experiment1 that1 
although the simplicity of its action is

 in its favor where crude means are     
necessary1 experiments with it had      
better be deferred until other things   
had been tried4    ,,hot-,,water        
,,engine  ,a great deal of attention was
 given to the hot-water engine1 but it  
was never put to practical use in the   
construction of an aerodrome1 partly on 
account of the necessary weight of a    
sufficiently strong containing vessel4  
,,compressed ,,air  ,compressed air1    
like the other possible sources of      
power1 was investigated1 but            
calculations from well-authenticated    
data showed that this system of         
propelling engines would probably be    
inadequate to sustain even the models in
 long flights4 ,as the chief difficulty 
lies in the weight1 not of the air1 but 
of the containing vessel1 numerous      
experiments were made in the            
construction of one at once strong and  
light4 ,the best result obtained was    
with a steel tube #dj mm4 in diameter1  
#dbh mm4 in length1 closed at the ends  

by heads united by wires1 which safely  
contained #ech cubic cm4 of air at an   
initial pressure of #ajj atmospheres for
 a weight of #eba grammes4 p#jbf  ,if we
 suppose this to be used1 by means of a 
proper reducing valve1 at a mean        
pressure of #ajj pounds1 for such an    
engine as that of ,aerodrome ,no4 #e1   
which takes #fj cubic cm4 of air at each
 stroke1 we find that 7if we take no    
account of the loss by expansion7 we    
have #ah1cbi foot-pounds of energy      
available1 which on the engine described
 will give #cjb revolutions of the      
propellers4  ,there are such limits of  
weight1 and the engines must be driven  
at such high speeds1 that the increased 
economy that might be obtained by       
re-heating the air would be out of the  
question4 ,the principal object in using
 it would have been the avoidance of    
fire upon the aerodrome1 and the        
expansion of the unheated air would     
probably have caused trouble with       
freezing1 while the use of hot 7i4 e4   

superheated7 water was impracticable4   
,so when1 after a careful computation1  
it was found that1 having regard to the 
weight of the containing vessel1 only   
enough compressed air could be stored at
 #gb atmospheres and used at #d1 to run 
a pair of engines with cylinders #j4i   
inch in diameter by #a4f inches stroke1 
at a speed of #abjj revolutions per     
minute for #bj seconds1 all further     
consideration of its adaptation to the  
immediate purpose was definitely        
abandoned4 ,this course1 however1 was   
not taken until after a model aerodrome 
for using compressed air had been       
designed and partially built4 ,then1    
after due consideration1 it was decided 
to make the test with carbonic-acid gas 
instead4    ,,gas  ,the gas engine      
possesses great theoretical advantages4 
,at the time of these experiments1 the  
gas engine most available for the       
special purposes of the models was one  
driven by air drawn through gasoline4   
,as the builders could not agree to     

reduce the weight of a one horse-power  
engine more than one-half of the then   
usual model1 and as the weight of the   
standard engine was #dgj pounds1 it was 
obvious that to reduce this weight to   
the limit of less than #c pounds was    
impracticable under the existing        
conditions1 and all consideration of the
 use of gas was abandoned provisionally1
 although a gasoline engine of          
elementary simplicity was designed but  
never built4 ,i purposed1 however1 to   
return to this attractive form of power 
if ,i were ever able to realize its     
theoretical advantages on the larger    
scale which would be desirable4         
,,electricity  ,as it was not intended  
to build the model aerodromes for a long
 flight1 it was thought that the        
electric motor driven by a primary or   
storage battery might possibly be       
utilized4 ,it therefore occurred to me  
that a battery might be constructed to  
give great power in proportion to its   
weight on condition of being            

short-lived1 and that in this form a    
battery might perhaps advantageously    
take the place of the dangerous         
compressed-air tubes that were at the   
time 7#ahic7 p#jbg under consideration  
for driving the models4 ,i assumed that 
the longest flight of the model would be
 less than five minutes4 ,any weight of 
battery1 then1 that the model carried in
 consumable parts lasting beyond this   
five minutes would be lost1 and hence it
 was proposed to build a battery1 the   
whole active life of which would be     
comprised in this time1 to actuate a    
motor or motors driving one or two      
propellers4  ,according to ,daniell1    
when energy is stored in secondary      
batteries1 over #cjj1jjj megergs per    
kilogramme of weight can be recovered   
and utilized if freshly charged4        
#cjj1jjj megergs  #j4fif horse-power for
 #a min4  #cjj1jjj megergs  #j4aci      
horse-power for #e min4  ,in a zinc and 
copper primary battery with sulphuric   
acid and water1 one kilogramme of zinc1 

oxidized1 furnishes at least #abjj      
calories as against #hjjj for one       
kilogramme of carbon1 but it is stated  
that the zinc energy comes in so much   
more utilizable a form that the zinc1   
weight for weight1 gives practically1   
that is in work1 #dj per cent that of   
carbon4 ,the kilogramme of carbon gives 
about #hjjj heat units1 each equal to   
#ajg kilogrammetres1 or about #f1agf1jjj
 foot-pounds4 ,of this1 in light        
engines1 from #e to #aj per cent1 or at 
least #cjh1hjj foot-pounds1 is utilized1
 and #b_/e of this1 or about #abd1jjj   
foot-pounds1 would seem to be what the  
kilogramme of zinc would give in actual 
work4 ,but to form the battery1 we must 
have a larger weight of fluid than of   
zinc1 and something must be allowed for 
copper4 ,if we suppose these to bring   
the weight up to #a kilogramme1 we might
 still hope to have #ej1jjj foot-pounds 
or #a4e horse-power for one minute1 or  
#j4c horse-power for #e minutes4        
,storage batteries were offered with a  

capacity of 4#be horse-power for #e     
minutes per kilogramme1 but according to
 ,daniell one cannot expect to get more 
than #j4aci horse-power from a freshly  
charged battery of that weight for the  
same time4  ,the plan of constructing a 
battery of a long roll of extremely thin
 zinc or magnesium1 winding it up with a
 narrower roll of copper or platinized  
silver1 insulating the two metals and   
then pouring over enough acid to consume
 the major portion of the zinc in #e    
minutes1 was carefully considered1 but  
the difficulties were so discouraging1  
that the work was not undertaken4  ,the 
lightest motors of #a horse-power       
capacity of which any trace could be    
found weighed #be pounds1 and a         
prominent electrician stated that he    
would not attempt to construct one of   
that weight4  ,in trials with a #a_/b   
horse-power motor driving an #hj cm4    
propeller of #a4jj pitch-ratio1 ,i      
apparently obtained a development of    
#j4ef indicated horse-power at #abfe    

revolutions2 but at lower speeds when   
tried with the ,prony brake1 the brake  
horse-power fell to #j4aj at #edf       
revolutions1 and even at #afej          
revolutions p#jbh it was but #j4bfb     
indicated1 with a brake horse-power of  
#j4add1 or #ee per cent of that         
indicated4  ,with these results both of 
theoretical calculation and practical   
experiment1 all thought of propelling   
the proposed aerodrome by electricity   
was necessarily abandoned4              
,,carbonic-,,acid ,,gas  ,at the first  
inception of the idea1 it seemed that   
carbonic-acid gas would be the motive   
power best adapted for short flights4   
,it can be obtained in the liquid form1 
is compact1 gives off the gas at a      
uniform pressure dependent upon the     
temperature1 and can be used in the     
ordinary steam engine without any       
essential modifications4 ,the only      
provision that it seemed1 in advance1   
necessary to make1 was that of some sort
 of a heater between the reservoir of   

liquid and the engine1 in order to      
prevent freezing1 unless the liquid     
itself could be heated previous to      
launching4  ,the engines in which it was
 first intended to use carbonic acid    
were the little oscillating cylinder    
engines belonging to ,aerodrome ,no4 #a4
 ,the capacity of each cylinder was     
#ba4b cu4 cm41 so that #hd4h cu4 cm4 of 
gas would be required to turn the       
propellers one revolution when admitted 
for the full stroke1 and #aja1gfj cubic 
cm4 for #abjj revolutions4 ,the density 
of the liquid at a temperature of #bd   
,c4 was taken as 4#gb1 and as #a volume 
of liquid gives #ahj volumes of gas at a
 pressure of #b-a_/b atmospheres1 we    
have #aja1gfj_/ahj  #efe cu4 cm4 of     
liquid1 or #djg grammes required for    
#abjj revolutions of the engines4       
,thus1 a theoretical calculation seemed 
to indicate that a kilogramme of liquid 
carbonic acid would be an ample supply  
for a run of two minutes4 ,the          
experiments were1 at first1 somewhat    

encouraging4 ,the speed and apparent    
power of the engines were sufficient for
 the purpose1 but the length of time    
during which power could be obtained was
 limited4  ,in #ahib1 #dae grammes of   
carbonic acid drove the engines of      
,aerodrome ,no4 #c #gjj revolutions in  
#fj seconds1 #ijj in #ge1 and #ajjj in  
#he seconds1 at the end of which time   
the gas was entirely expended4 ,the     
diameter of these cylinders was #b4d    
cm41 the stroke of the pistons #g cm41  
and the work done1 that of driving a    
pair of #ej cm4 propellers1 when taken  
in comparison with the propeller tests  
detailed elsewhere1 amounted to an      
effective horse-power of about #j4aj for
 the output of the engine4  ,the        
difficulties1 however1 that were        
experienced were those partially        
foreseen4 ,the expansion of the gas made
 such serious inroads upon the latent   
heat of the liquid1 that lumps of solid 
acid were formed in the reservoir1 and  
could be heard rattling against the     

sides when the latter was shaken1 while 
the expansion of the exhaust caused such
 a lowering of temperature at that      
point1 that the p#jbi pipes were soon   
covered with a thick layer of ice1 and  
the free exit of the escaping gas was   
prevented4  ,such difficulties are to be
 expected with this material1 but here  
they were enhanced by the small scale of
 the construction and the constant      
demand for lightness4 ,and it was found 
to be very hard to fill the small       
reservoirs intended to carry the supply 
for the engines4 ,when they were screwed
 to the large case in which the liquid  
was received and the whole inverted1 the
 small reservoir would be filled from   
one-third to one-half full1 and nothing 
that could be done would force any more 
liquid to enter4  ,in view of these     
difficulties1 and the objections to     
using a heater of any sort for the gas1 
as well as the absolute lack of success 
attendant upon the experiments of others
 who were attempting to use liquid      

,,co#b as a motive power on a large     
scale elsewhere1 experiments were at    
first temporarily and afterwards        
permanently abandoned4  ,the above      
experiments extended over nearly a year 
in time1 chiefly during #ahib1 and      
involved the construction and use of the
 small aerodromes ,nos4 #a1 #b1 and #c1 
presently described4   p#jcj            
,,chapter ,,iv  ,,early ,,steam ,,motors
 ,,and ,,other ,,models  ,in dealing    
with the development of the aerodrome1  
subsequent to the early rubber-driven   
models1 the very considerable work done 
and the failures incurred with other    
types of motors than steam1 have been   
briefly dealt with in the preceding     
chapter1 but are scarcely mentioned     
here1 as no attempts at long flights    
were ever successful with any other     
motor than steam1 and no information was
 gained from any of the experiments made
 with compressed air1 gas1 carbonic     
acid1 or electricity1 that was of much  
value in the development of the         

successful steam machines4  ,in         
,november1 #ahia1 after the long and    
unsatisfactory experiments with         
rubber-driven models already referred   
to1 and before most of the experiments  
with other available motors than steam  
had been made1 ,i commenced the         
construction of the engines and the     
design of the hull of a steam-driven    
aerodrome1 which was intended to        
supplement the experiments given in     
8,aerodynamics0 by others made under the
 conditions of actual flight4  ,in      
designing this first aerodrome1 here    
called ,no4 #j1 there was no precedent  
or example1 and except for the purely   
theoretical conditions ascertained by   
the experiments described in            
8,aerodynamics10 everything was unknown4
 ,next to nothing was known as to the   
size or form1 as to the requisite       
strength1 or as to the way of attaching 
the sustaining surfaces2 almost nothing 
was known as to the weight permissible1 
and nothing as to the proper scale on   

which to build the aerodrome1 even if   
the design had been obtained1 while     
everything which related to the actual  
construction of boiler and engines      
working under such unprecedented        
conditions was yet to be determined by  
experiment4  ,the scale of the actual   
construction was adopted under the      
belief that it must be large enough to  
carry certain automatic steering        
apparatus which ,i had designed1 and    
which possessed considerable weight4 ,i 
decided that a flying machine if not    
large enough to carry a manager1 should 
in the absence of a human directing     
intelligence1 have some sort of         
automatic substitute for it1 and be     
large enough to have the means of       
maintaining a long and steady flight1   
during which the problems 7which the    
rubber-driven models so imperfectly     
answered7 could be effectually solved4  
,when1 in #ahia1 it was decided to      
attempt to build this steam aerodrome1  
the only engine that had been made up to

 that time with any claim to the        
lightness and power ,i was seeking1 was 
the ,stringfellow engine1 exhibited at  
the ,crystal ,palace in ,london1 in     
#ahfh1 which it was then announced      
developed #a horse-power p#jca for a    
total weight 7boiler and engines7 of #ac
 pounds4 ,the original engine came into 
the possession of the ,institution in   
#ahhi as an historical curiosity1 but on
 examination1 it was at once evident    
that it never had developed1 and never  
could develop the power that had been   
attributed to it1 and probably not      
one-tenth so much4  ,with the results   
obtained on the whirling-table at       
,allegheny as a basis1 a theoretical    
computation of the weight which #a      
horse-power would cause to soar showed  
that1 with a plane whose efficiency     
should be equal to that of a #cjd4h inch
 plane set at an angle of #e and moving 
at a speed of #cd miles an hour1 #a     
horse-power would support #abj          
pounds4#ai ,with a smaller angle even   

better results could be obtained1 but as
 the difficulties of guidance increase  
as the angle diminishes1 ,i did not     
venture to aim at less than this4 ,in   
this computation1 no allowance was made 
for the fact that these results were    
obtained by a mechanism which forcibly  
maintained the supporting surface in the
 ideal condition of the best attainable 
angle of attack as if in perfect        
equilibrium1 and above all in the       
equally ideal condition of perfectly    
horizontal flight4  ,besides this1 ,i   
had to consider in actual flight the air
 resistance due to the guy wires and    
hull1 but after making an allowance of  
as much as three-quarters for these     
differences between the conditions of   
experiment and those of free flight1 ,i 
hoped that #a horse-power would serve to
 carry #cj pounds through the air if a  
supporting surface as large as #c feet  
to the pound could be provided1 and this
 was the basis of the construction which
 ,i will now describe4  ,the general    

form of this ,aerodrome ,no4 #j1 without
 wings or propellers1 is shown in the   
accompanying photograph in ,plate #aj4  
,its dimensions and its weights1 as     
first designed1 and as finally found    
necessary1 are as follows3              
,,comparison ,,of ,,estimated ,,and     
,,actual ,,weights ,,of ,,parts ,,of    
,,aerodrome 8#j0--;,,in ,,pounds ,,and  
,,ounces4                               
,estimated   ,actual                    
lbs4 oz4   lbs4 oz4 ,engines            
#d    #j     #d    #a ,boilers and      
,burners                                
#h   #aa    #ac   #ad ,pumps and        
,attachments                            
#j    #j     #a   #aj ,steering         
,apparatus                              
#j    #f     #j    #j ,frame of ,hull   
and ,braces1 including bowsprit   and   
tail tube                               
#g    #g     #h   #aa ,oil tank covering
 and pipes                          #j  
#j     #j   #ac ,shafts1 ball bearings  
7#b3a7 and wooden   propellers 7#a3g7   

#a   #ad     #c    #h ,wings 7#e3d7 and 
guys 7#j3i7                           #d
    #j     #e   #ac ,tail               
#a    #e     #b    #b ,jacket at prow   
#j    #j     #d    #j                   
---------  ---------       ,total       
without oil or water                    
#bg   #aa    #dd    #h  7,the weights   
attained in the actual making were1 as  
is seen1 nearly double those first      
estimated1 and this constant increase of
 weight under the exigencies of         
construction was a feature which could  
never be wholly eliminated47 p#jcb      
,after studying various forms for the   
hull or body of the prospective         
aerodrome1 ,i was led to adopt the lines
 which ,nature has used in the mackerel 
as most advantageous so far as the      
resistance of the air was concerned1 but
 it proved to be difficult in           
construction to make the lines of the   
bow materially different from those of  
the stern1 and in this first model the  
figure was symmetrical throughout4  ,as 

,i wish that my experience may be of    
benefit to the reader1 even in its      
failures1 ,i will add that ,i made the  
not unnatural mistake of building on the
 plan on which the hull of an ordinary  
ship is constructed2 that is1 making the
 hull support the projecting bowsprit   
and other parts4 ,in the aerodrome1 what
 corresponds to the bowsprit must       
project far in advance of the hull to   
sustain the front wings1 and a like     
piece must project behind it to sustain 
the rear wings and the tail1 or the     
supporting surfaces of whatever kind4   
,the mistake of the construction lay in 
disjoining these two and connecting them
 indirectly by the insufficiently strong
 hull which supported them4 ,this hull  
was formed of longitudinal ,u-shaped    
ribs of thin steel1 which rested on     
rings made of an alloy of aluminum1     
which possessed the lightness of the    
latter metal with very considerable     
toughness1 but which was finally        
unsatisfactory4 ,i may say              

parenthetically that in none of the     
subsequent constructions has the        
lightness of aluminum been found to     
compensate for its very many            
disadvantages4 ,the two rods1 which were
 each #a metre in length1 were with     
difficulty kept rigorously in line1     
owing to the yielding of the            
constructionally weak hull4 ,it would   
have been better1 in fact1 to have      
carried the rod straight through at any 
inconvenience to the disposition of the 
boilers and the engine4  ,illustration3 
,,pl4 #aj  ,,steel ,,frames ,,of        
,,aerodromes ,,nos4 #j1 #a1 #b1 #c1     
#ahia ,,and #ahib  ,i may add that the  
sustaining surfaces1 which were to be   
nearly flat wings1 composed of silk     
stretched from a steel tube with wooden 
attachments1 were to p#jcc have been    
carried on the front rod1 but1 as       
subsequent experience has shown1 these  
wings would have been inadequate to the 
work1 both from their insufficient size 
and their lack of rigidity4  ,the       

propellers1 which were to be #hj cm4 in 
diameter1 #a4be pitch-ratio1 and which  
were expected to make from five to six  
hundred revolutions a minute1 were      
carried on the end of long tubular      
shafts1 not parallel1 but making with   
each other an angle of #be degrees1 and 
united by gears near the bow of the     
vessel in the manner shown in ,plate    
#aj4  ,the first engines were of the    
oscillating type1 with the piston-rod   
connected directly to the crank2 were   
very light1 and were unprovided with    
many of the usual fittings belonging to 
a steam engine1 such as rod or piston   
packing2 and their construction was     
crude in comparison with their          
successors4 ,they were tested with the  
,prony brake and found to be deficient  
in power1 for with a steam pressure of  
#hj pounds to the square inch1 they ran 
at the rate of #aagj revolutions per    
minute1 and developed only 4#cfc        
horse-power4 ,it soon became evident    
that they were too light for the work   

that it was intended that they should   
do1 and steps were taken1 even before   
the completion of these tests1 for the  
construction of a pair of more powerful 
cylinders1 which should also be provided
 with a special boiler for the          
generation of the steam4 ,acting upon   
the supposition1 in a saving of steam1  
it was decided to work with compounded  
cylinders4 ,as two propellers were to be
 used1 they were each fitted with a     
distinct pair of cylinders working      
directly upon the shaft1 but so         
connected by gearing that they were     
compelled to turn at the same rate of   
speed4  ,the cylinders were of the      
inverted oscillating type1 like the     
first pair of engines1 but1 unlike them1
 they were single-acting4 ,the          
dimensions were3 diameter of            
high-pressure cylinder #a4be inches2 low
 pressure1 #a4id inches1 with a common  
stroke of #b inches1 and with cranks set
 opposite to each other so that one     
cylinder was always at work4 ,the       

cylinders were held at their upper ends 
by a strap passing around a hollow      
conical trunk1 which served the double  
purpose of a support for the cylinders  
and an intermediate receiver between    
them4 ,this receiver had a mean inside  
diameter of #a4be inches1 with a length 
of #d4ge inches1 so that it had about   
twice the cubical capacity of the       
high-pressure cylinder1 while the       
displacement of the low-pressure        
cylinder was about #b4e times that of   
the high2 ratios that would have given  
satisfactory results1 perhaps1 had the  
steam pressure and other conditions been
 favorable to the use of the compound   
principle in this place4 ,there were no 
valves for the admission of the steam1  
for1 inasmuch as the engines were       
single-acting1 it was possible to make  
ports in the cylinder-head act as the   
admission and exhaust ports as the      
cylinder oscillated1 and thus avoid the 
complication and weight of eccentric and
 valves4 p#jcd  ,these cylinders were   

set in a light frame at an angle of #be 
with each other1 or #ab4e with the      
median line of the aerodrome1 and drove 
the long propeller shafts as shown in   
,plate #aj1 ,no4 #j4 ,at the extreme    
forward end of the crank-shafts there   
was a pair of intermeshing bevel gears  
which served to maintain the rate of    
revolution of the two propellers the    
same4  ,illustration3 ,,fig4 #c4        
,boilers in use in #ahia-ahib4  ,the    
boiler built for this work was a        
beehive-shaped arrangement of coils of  
pipe4 ,it consisted at first1 as shown  
in ,fig4 #c1 of three double coils of   
#c_/h-;inch copper pipe coiled up in the
 shape of a truncated cone1 carrying in 
the central portion a pear-shaped       
receiver into the upper portion of which
 the water circulating through the coils
 discharged4 ,each of these receivers   
was connected at the top with the bottom
 of a long cylindrical drum1 with       
hemispherical ends1 which formed a steam
 space from which supply for the engines

 was drawn4 ,the lower ends of the coils
 were connected with an injection pipe  
supplying the water4 ,each 8beehive0 had
 #bc turns of tubing1 and had a base of 
#g4e inches and a top diameter of #f    
inches1 the steam drum being #b4e inches
 in diameter4 ,i may here say that in   
the selection of the general type of    
boiler for the work to be done1 there   
was never any hesitation regarding the  
use of the water-tube variety4 ,their   
superiority for the quick generation of 
large volumes of steam had been so      
pronounced that nothing else seemed     
capable of competing with p#jce them in 
this respect1 regardless of the absolute
 economy of fuel that might or might not
 be exhibited4 ,hence1 to the end of my 
experiments nothing else was used4      
,even before the 8beehive0 boiler was   
completed1 ,i was anxious to ascertain  
what could be done with a coil of pipe  
with a stream of water circulating      
through it1 as well as with various     
forms of burners1 for ,i realized that  

the success of the apparatus depended   
not only upon getting an exceedingly    
effective heating surface1 but also an  
equally effective flame to do the       
heating4  ,for fuel ,i naturally turned 
to the liquids as being more compact and
 readily regulated4 ,whether to use some
 of the more volatile hydrocarbons or   
alcohol1 was still an unsolved problem1 
but my opinion at the time was that1 on 
the limited scale of the model1 better  
results could probably be obtained with 
alcohol4  ,in the experiments made with 
a coil preliminary to the trial of the  
8beehive0 boiler1 ,i tried a simple     
horizontal coil of #c_/h-;inch copper   
pipe into which two forked burners      
working on the ,bunsen principle and    
using city illuminating gas1 were       
thrust4 ,the jets were about #a_/b inch 
apart4 ,the arrangement primed so badly 
that the engines could not get rid of   
the entrained water1 and would only make
 a few turns4  ,i then tried the same   
coil with two #a4be-;inch drums in the  

inside and with five longitudinal water 
tubes at the bottom1 beneath which were 
the same two forked burners used in the 
previous experiment4 ,the coils were    
covered with a sheet of asbestos1 and   
two round burners were added4 ,this     
boiler would hold a steam pressure of   
about #ae pounds and run the engine     
slowly2 but if the pressure were allowed
 to rise to #fj pounds1 the engine would
 drive a #b-;foot propeller of #ah-;inch
 pitch at the rate of about #fej turns  
per minute for from #hj to #ij seconds1 
while the steam ran down to #aj pounds1 
showing that this boiler1 at least1 was 
too small4 ,this was further shown in a 
trial of the plain coil made in         
,october1 #ahia2 #f pounds of water were
 evaporated in #cb minutes under a      
pressure of #fj pounds4 ,this was at the
 rate of #aa4be pounds per hour1 or1    
taking the ,u4 ,s4 ,centennial standard 
of #cj pounds of evaporation per        
horse-power1 gave an available output of
 less than #a_/c horse-power4  ,with    

these results before me1 ,i decided to  
make a trial of the 8beehive0 principle 
upon a smaller scale than in the boiler 
designed for ,aerodrome ,no4 #j4 ,i used
 a small boiler of which the inner coil 
consisted of #h turns of #c_/h-;inch    
copper tube about #bh gauge thick1 and  
the outer coil of #aa turns of          
#a_/d-;inch copper pipe4 ,this gave #ab 
feet of #c_/h-;inch1 and #af feet of    
#a_/d-;inch tubing4 ,the drum was of    
,no4 #bg gauge1 hard planished copper4  
,with this boiler consuming #f oz4 of   
fuel1 #hj4c oz4 of water were evaporated
 in #bh minutes1 or at the rate of about
 #aj4ge pounds per hour4 ,as these coils
 contained but #b4bb square feet of     
heating surface1 and as the three to be 
built would contain #c4g square feet    
each1 it was estimated the p#jcf #aj    
square feet afforded by them could      
safely be depended upon to provide steam
 for a #a horse-power engine4 ,as far as
 fuel consumption was concerned1 the    
rate of evaporation was about #ae4f     

pounds of water per pound of gasoline1  
all of which was satisfactory4  ,the    
burner originally designed for use in   
connection with the 8beehive0 boilers1  
consisted of a small tank in which a    
quantity of gasoline was placed1 the    
space above being filled with compressed
 air4 ,rising from the bottom of this   
tank was a small pipe coiling back and  
down and ending in an upturned jet from 
which the gas generated in the coil     
would issue4 ,the burner thus served to 
generate its own gas and act as a heater
 for the boilers at the same time4  ,in 
the construction of ,aerodrome ,no4 #j1 
four of the 8beehive0 coils were placed 
in a line fore and aft4 ,the fuel tank  
was located immediately back of the rear
 coil and consisted of a copper cylinder
 #aa cm4 in diameter and #i cm4 long4   
,the engines were placed immediately in 
front of the coils1 all the apparatus   
being enclosed in a light framing1 as   
shown in the photograph 7,plate #aj74   
,extending front and back from the hull 

were the tubes for supporting the wings 
and tail1 each one metre in length4 ,the
 cross-framing for carrying the         
propeller shafts was built of tubing    
#a4e cm4 diameter1 and the shafts       
themselves were of the same size4 ,the  
ribs of the hull were rings made of     
angle-irons measuring #a4eja4ge cm41    
which were held in place longitudinally 
by five #j4g cm4 channel bars4  ,as it  
had been learned in the preliminary     
experiments with the model 8beehive0    
boiler that the heated water would not  
of itself cause a sufficiently rapid    
circulation to be maintained through the
 tubes to prevent them from becoming    
red-hot1 two circulating pumps were     
added for forcing the water through the 
coils of the two forward and two rear   
boilers respectively1 the water being   
taken from the lower side of the drum   
and delivered into the bottom of the    
coils1 which were united at that point  
for the purpose4 ,a worm was placed upon
 each of the propeller shafts1 just back

 of the engines1 meshing in with a gear 
on a crank-shaft from which the pumps   
were driven4 ,this shaft rotated at the 
rate of #a to #bd1 so that for #abjj    
revolutions of the engine1 it would make
 but #ej1 driving a single-acting       
plunger #a4b cm4 in diameter and #b cm4 
stroke4  ,apparently all was going well 
until ,i began to try the apparatus4    
,first1 there was a difficulty with the 
burner1 which could not be made to give 
forth the relative amount of heat that  
had been obtained from the smaller      
model1 and steam could not be           
maintained4 ,with one 8beehive0         
connected with the compound engine1 and 
a #gj cm4 propeller on the shaft1 there 
were about #bej turns per minute for a  
space of about #ej seconds1 in which    
time the steam would fall from #ij      
pounds to #be pounds1 and the engine    
would stop4 ,then1 as we had no         
air-chamber on the pumps at the time1   
they would not drive the water through  
the coils4 ,subsequent experiments1     

however1 showed that the boilers could  
be p#jcg depended upon to supply the    
steam that the compound engines would   
require2 but after the whole was        
completed1 the weight1 if nothing else1 
was prohibitory4  ,i had gone on from   
one thing to another1 adding a little   
here and a little there1 strengthening  
this part and that1 until when the hull 
was finally completed with the engines  
and boilers in place1 ready for the     
application of the wings1 the weight of 
the whole was found 7allowing #g pounds 
for the weight of the wings and tail7 to
 be almost exactly #de pounds1 and      
nearly #eb pounds with fuel and water4  
,to this excessive weight would have to 
be added that of the propellers1 and as 
the wings would necessarily have to be  
made very large in order to carry the   
machine1 and as the difficulties of     
launching had still to be met1 nothing  
was attempted in the way of field       
trials1 and with great disappointment   
the decision was made in ,may1 #ahib    

7wisely1 as it subsequently appeared7 to
 proceed no further with this special   
apparatus4  ,however1 inasmuch as this  
aerodrome with its engines and boilers  
had been completed at considerable      
expense1 it was decided to use the      
apparatus as far as it might be         
practicable1 in order to learn what must
 be done to secure a greater amount of  
success in the future4 ,the fundamental 
trouble was to get heat4 ,in the first  
place there was trouble with the        
burners1 for it seemed to be impossible 
to get one that would vaporize the      
gasoline in sufficient quantity to do   
the work1 and various forms were        
successively tried4  ,all of the early  
part of #ahib was passed in trying to   
get the boilers to work at a steam      
pressure of #ajj pounds per square inch4
 ,on account of the defects in the tubes
 and elsewhere this required much       
patient labor4 ,the writer1 even thus   
early1 devised a plan of using a sort of
 aeolipile1 which should actuate its own

 blast1 but this had to be abandoned on 
account of the fact that the pear-shaped
 receivers would not stand the heat4    
,this necessitated a number of          
experiments in the distillation of gas1 
in the course of which there was trouble
 with the pumps1 and a continual series 
of breakages and leakages1 so that the  
middle of ,april came before ,i had     
secured any further satisfaction than to
 demonstrate that possibly the boilers  
might have a capacity sufficient for the
 work laid out for them to do2 but      
subsequent experiments showed that even 
in this ,i was mistaken1 for it was only
 after additional jets had been put in  
between the coils that ,i succeeded in  
getting an effective horse-power of     
#j4dc out of the combination4  ,finally1
 on the #adth of ,april1 after having   
reduced the capacity of the pumps to the
 dimensions given above 7for the stroke 
was originally #a4be inch7 ,i obtained  
the development of #a full horse-power  
by the engine for #da seconds1 with a   

steam pressure of #ajj pounds per square
 inch1 and a rate of revolution of #gbj 
per minute4 ,but at the end of this     
brief period1 the shafts sprung and the 
worm was thrown out of gear4 p#jch  ,i  
pass over numerous other experiments1   
for their only result was to make it    
clear that the aerodrome1 as it had been
 constructed1 could not be made to work 
efficiently1 even if its great weight   
had not served as a bar to its flight4  
,it was1 therefore1 decided to proceed  
with the construction of another4       
,after the failure of the first         
steam-driven model ,no4 #j1 which has   
just been described1 subsequent light   
models were constructed4 ,these1 three  
in number1 made with a view to the      
employment of carbonic acid or          
compressed air1 but also to the possible
 use of steam1 are shown in ,plate #aj1 
,nos4 #a1 #b1 #c2 on the same scale as  
the larger model which had preceded     
them4 ,in describing these1 it will be  
well to mention constructive features   

which were experimented on in them1 as  
well as to describe the engines used4   
,in ,no4 #a1 which was intended to be on
 about #b_/e the linear scale of ,no4   
#j1 the constructive fault of the       
latter1 that of making the support      
depend on a too flexible hull1 was      
avoided1 and the straight steel tube    
78midrod0 it will hereafter be called7  
was carried through from end to end1    
though at the cost of inconvenience in  
the placing of the machinery1 in what   
may be called the hull1 which now became
 simply a protective case built around  
this midrod4 ,the mistaken device of the
 long shafts meeting at an angle1 was1  
however1 retained1 and the engines first
 tried were a pair of very light ones of
 crude construction4  ,these were later 
replaced by a pair of oscillating       
engines1 each #c cm4 diameter by #c cm4 
stroke1 with a combined capacity of #db 
cubic cm4 and without cut-off4 ,the     
midrod was made of light steel tubing #b
 cm4 outside diameter4 ,the framing for 

the hull was formed by a single ring of 
,u section1 #h cm4 across and #ah cm4 in
 depth1 stayed by five ribs of wood     
measuring #j4gj4c cm4 ,the inclined     
propeller shafts1 which were connected  
by a pair of bevel gears as in ,no4 #j1 
were made of tubing #j4e cm4 outside    
diameter1 and were intended to turn     
propellers of from #dj to #de cm4 in    
diameter4 ,the weight1 without engine or
 reservoir for gas1 was #aafa grammes4  
,with a weight equivalent to that of the
 intended reservoir and engines plus    
that of the proposed supporting         
surfaces1 the whole weight1 independent 
of fuel or water1 was #b4b kilogrammes4 
,the engines1 which were not strong     
enough to sustain a pressure of over #b 
atmospheres1 at an actual pressure of   
#bj pounds drove the #de cm4 propellers 
through the long ,v shafts and lifted   
only about #a_/g of the flying weight of
 the machine4 ,the power developed at   
the ,prony brake was collectively only  
about 4#jd horse-power1 giving #abjj    

turns a minute to two #dj cm4           
propellers4 ,this was the best result   
obtained4  ,this aerodrome was completed
 in ,june1 #ahib1 but changes in the    
engines and other attempted improvements
 kept it under experiment until         
,november of that year1 when it appeared
 to be inexpedient to do anything more  
with it4  ,aerodrome ,no4 #b 7see ,plate
 #aj71 was a still smaller and still    
lighter construction1 in which1 however1
 the midrod was bent 7not clearly shown 
in the p#jci photograph71 so as to      
afford more room in the hull4 ,this     
introduced a constructional weakness    
which was not compensated by the added  
convenience1 but the principal          
improvement was the abandonment of the  
inclined propeller shafts1 which was    
done at the suggestion of ,mr4 ,j4 ,e4  
,watkins1 so that the propellers were   
carried on parallel shafts as in marine 
practice4 ,these parallel shafts were   
driven by two very small engines with   
cylinders #b4c cm4 in diameter by #d cm4

 stroke1 with a collective capacity of  
#cc cu4 cm4 and without cut-off1 which  
were mounted on a cross-frame attached  
to the midrod at right angles near the  
rear end of the hull4  ,these engines1  
driven either by steam or by            
carbonic-acid gas developed #j4jce      
horse-power at the ,prony brake1 giving 
#gej revolutions of the #de cm4         
propellers1 and lifting about #a_/e of  
the total weight which it was necessary 
to provide for in actual flight4 ,a     
higher rate of revolution and a better  
lift were occasionally obtained1 but    
there was little more hope with this    
than with the preceding models of       
obtaining power enough to support the   
actual weight in flight1 although such  
sacrifices had been made for lightness  
that every portion of the little model  
had been reduced to what seemed the     
limit of possible frailty consistent    
with anything like safety4 ,thus the    
midrod was lighter than that of ,no4 #a1
 being only #a cm4 in outside diameter4 

,the frame was made of thin wooden      
strips #e mm4#c4e mm41 united by light  
steel rings4 ,the cross framing carrying
 the engines was also of wood1 and was  
formed of four strips1 each #g mm4#c mm4
 ,the shafts were but #d mm4 in         
diameter4  ,as these engines did not    
give results that were satisfactory1    
when using carbonic-acid gas1           
experiments were commenced to secure a  
boiler that would furnish the requisite 
steam4 ,as the 8beehive0 boiler had     
proved to be too heavy1 and as the steam
 obtained from it had been inadequate to
 the requirements1 something else had to
 be devised4 ,a few of the boilers used 
in #ahib are shown in ,fig4 #c4 ,the one
 marked ,a is one of the 8beehives10    
while an element of another form tried  
is that marked ,b4 ,it consisted of     
#c_/h-;inch copper tubes joined to a    
drum of #aj-oz4 copper4 ,this was made  
in ,may1 #ahib1 and was tested to a     
pressure of #ej atmospheres1 when it    
burst without any tearing of the metal4 

,in ,july another boiler like that shown
 at ,c in ,fig4 #c was made4 ,this was  
formed of tubes #c cm4 in diameter1 and 
weighed #cdh grammes4 ,it carried about 
#cjj grammes of water and stood a steam 
pressure of #abe pounds per square inch1
 but failed to maintain sufficient steam
 pressure4  ,accordingly1 in the same   
month1 a third boiler like that shown at
 ,d was built4 ,it consisted of a tube  
#ab inches long to which were attached  
fifteen #a_/d-;inch tubes each #g inches
 long1 in the manner shown4 ,the heating
 surface of this boiler1 including the  
tubes and the lower half of the drum1   
amounted to #gej square cm41 and it was 
thought that this would be sufficient to
 supply steam for a flight of a p#jdj   
minute and a half4 ,but when a test was 
made1 it also was found to be deficient 
in steaming power even after changes    
were made in it which occupied much     
time4  ,by the first of ,october1 #ahib1
 there had been built one large         
aerodrome that could not possibly fly1 a

 smaller one1 ,no4 #a1 on #b_/e the     
linear scale of ,no4 #j1 with a pair of 
engines but no means of driving them1   
and the still smaller ,no4 #b with a    
boiler that was yet untried4  ,aerodrome
 ,no4 #c 7,plate #aj7 was an attempt to 
obtain better conditions than had       
existed in the preceding model without  
any radical change except that of moving
 the cross frame1 which carried the     
engines and propellers1 nearer the front
 of the machine4 ,instead of the        
oscillatory engines used up to this     
time1 two stationary cylinder engines1  
each #b4d cm4 in diameter and #d cm4    
stroke1 having a combined capacity of   
#cf cu4 cm4 without cut-off were        
employed for driving the propellers4    
,the engines1 though occasionally run in
 trials with steam from a stationary    
boiler1 were intended to be actuated    
either by compressed air or             
carbonic-acid gas contained in a        
reservoir which was not actually        
constructed1 but whose weight was       

provisionally estimated at #a           
kilogramme4 ,the weight of the aerodrome
 without this reservoir was but #ajej   
grammes1 including the estimated weight 
of the sustaining surfaces1 which       
consisted principally of two wings1 each
 about #a metre in length by #cj cm4 in 
breadth and which were in fact so slight
 in their construction1 that it is now  
certain that they could not have        
retained their shape in actual flight4  
,the only trials made with this         
aerodrome1 then1 were in the shop1 of   
which it is sufficient to cite those of 
,november #bb1 #ahib1 when under a      
pressure of #cj pounds1 the maximum     
which the engines would bear1 two #ej   
cm4 propellers were driven at #ijj      
revolutions per minute1 with an         
estimated horse-power of #j4jg1 about   
#ce per cent of the weight of the whole 
machine being lifted4 ,this was a much  
more encouraging result than any which  
had preceded1 and indicated that it was 
possible to make an actual flight with  

the aerodrome if the boilers could be   
ignored1 the best result having been    
obtained only with carbonic acid        
supplied without limit from a           
neighboring ample reservoir4  ,this     
aerodrome was also tested while mounted 
upon a whirling-arm and allowed to      
operate during its advance through the  
air4 ,the conclusion reached with it at 
the close of #ahib1 after a large part  
of the year passed in experiments with  
carbonic-acid gas and compressed air1   
was that it was necessary to revert to  
steam1 and that whatever difficulties   
lay in the way1 some means must be found
 of getting sufficient power without the
 weight which had proved prohibitory in 
,no4 #j4  ,with this chapter1 then1 and 
with the end of the year #ahib1 ,i close
 this very brief account of between one 
and two years of fruitless experiment in
 the construction of models supplied    
with various motors1 subsequent to and  
on a larger scale indeed than the       
toy-like ones of india rubber1 but not  

even so efficient as those had been1    
since they had never procured a single  
actual flight4   p#jda    ,,chapter ,v  
,,on ,,sustaining ,,surfaces  ,the      
following general considerations may    
conveniently precede the particular     
description of the balancing of the     
aerodrome4  ,in 8,experiments in        
,aerodynamics10 ,i have given the result
 of trials1 showing that the pressure   
7or total resistance7 of a wind on a    
surface #a foot square1 moving normally 
at the velocity of #a foot per second1  
is #j4jjaff pounds1 and that this       
pressure increases directly as the      
surface of the plane1 and 7within our   
experimental condition7 as the square of
 the velocity1#bj results in general    
accordance with those of earlier        
observers4  ,i have further shown by    
independent investigations that while   
the shape of the plane is of secondary  
importance if its movement be normal1   
the shape and 8aspect0 greatly affect   
the resultant pressure when the plane is

 inclined at a small angle1 and         
propelled by such a force that its      
flight is horizontal1 that is1 under the
 actual conditions of soaring flight4   
,i have given on page #fj of            
8,aerodynamics10 the primary equations1 
,p  ,p#ij;,f77  k,a,v#b;,f771  ,w  ,p   
cos   k,a,v#b;,f77 cos 1  ,r  ,p sin    
k,a,v#b;,f77 sin 1  where ,w is the     
weight of the plane under examination   
7sometimes called the 8lift072 ,r the   
horizontal component of pressure        
7sometimes called the 8drift072 k is the
 constant already given2 ,a the area in 
square feet2 ,v the velocity in feet per
 second2 ,f a function of  7to be       
determined by experiment72  the angle   
which1 under these conditions1 gives    
horizontal flight4  ,i have also given  
on page #ff of the same work the        
following table showing the actual      
values obtained by experiment on a      
plane1 #cjd4h inches 7 #a sq4 ft471     
weighing #ejj grammes 7#a4a pounds73    
,weight with planes ,angle   ,soaring   

speed ,horizontal   ,work expended    of
 like form that with        ,v4         
pressure     per minute     #a          
horse-power will horizon                
,r4        #fj ,,rv4       drive through
 the  4                                 
air at velocity ,v4 -------             
------------- ----------                
----------------- --------------------  
,metres  ,feet   ,grammes4  ,kilogram-  
,foot-   ,kilo-     ,pounds4            
per     per              metres4        
pounds4 grammes4          sec4    sec4  
#de    #aa4b    #cf4g    #ejj           
#ccf      #b1dcd     #f4h        #ae    
#cj     #aj4f    #cd4h    #bge          
#age      #a1bfh    #ac4j        #bi    
#ae     #aa4b    #cf4g    #abh          
#hf        #fbc    #bf4e        #eh  #aj
     #ab4d    #dj4g     #hh         #fe 
#dgd    #cd4h        #gg   #e     #ae4b 
#di4h     #de         #da        #big   
#ee4e       #abb   #b     #bj4j    #fe4f
     #bj         #bd        #agd        
#ie4j       #bji   ,it cannot be too    

clearly kept in mind that these values  
refer to horizontal flight1 and that for
 this the weight1 the work1 the area1   
the angle and the velocity are          
inseparably connected by the formul     
already given4  ,it is to be constantly 
remembered also1 that they apply to     
results obtained under almost perfect   
theoretical conditions as regards not   
only the maintenance of equilibrium and 
horizontality1 but also the rigid       
maintenance of the angle  and the       
comparative absence of friction1 and    
that these conditions are especially    
8theoretical0 in their exclusion of the 
internal work of the wind observable in 
experiments made in the open wind4      
,,experiments ,,in ,,the ,,open ,,wind  
,i have pointed out#ba that an          
indefinite source of power for the      
maintenance of mechanical flight1 lies  
in what ,i have called the 8internal    
work0 of the wind4 ,it is easy to see   
that the actual effect of the free wind1
 which is filled with almost infinitely 

numerous and incessant changes of       
velocity and direction1 must differ     
widely from that of a uniform wind such 
as mathematicians and physicists have   
almost invariably contemplated in their 
discussions4  ,now the artificial wind  
produced by the whirling-table differs  
from the real wind not only in being    
caused by the advancing object1 whose   
direction is not strictly linear1 and in
 other comparatively negligible         
particulars1 but especially in this1    
that in spite of little artificial      
currents the movement on the whole is   
regular and uniform to a degree         
strikingly in contrast with that of the 
open wind in nature4  ,in a note to the 
,french edition of my work1 ,i have     
called the attention of the reader to   
the fact that the figures given in the  
,smithsonian publication can show only a
 small part of the virtual work of the  
wind1 while the plane1 which is used for
 simplicity of exposition1 is not the   
most advantageous form for flight2 so   

that1 as ,i go on to state1 the         
realization of the actually successful  
aerodrome must take account of the more 
complex conditions actually existing in 
nature1 which were only alluded to in   
the memoir1 whose object was to bring to
 attention the little considered        
importance of the then almost unobserved
 and unstudied minute fluctuations which
 constitute the internal work of the    
wind4 ,i added that ,i might later      
publish some experimental investigations
 on the superior efficiency of the real 
wind over that artificially created4    
,the experiments which were thus alluded
 to in #ahic1 were sufficient to        
indicate the importance of the subject1 
but the data have not been preserved4   
,what immediately follows refers1 it    
will be observed1 more particularly to  
the work of the whirling-table4 p#jdc   
,,relation ,,of ,,area ,,to ,,weight    
,,and ,,power  ,in order to get a more  
precise idea of the character of the    
alteration introduced into these        

theoretical conditions by the variation 
of any of them1 let us1 still confining 
ourselves to the use of the             
whirling-table1 suppose that the plane  
in question while possessing the same   
weight1 shape1 and angle of inclination1
 were to have its area increased1 and to
 fix our ideas1 we will suppose that it 
became #d square feet instead of #a as  
before4 ,then1 from what has already    
been said1 ,v1 the velocity1 must vary  
inversely as the square root of the     
area2 that is1 it must1 under the given 
condition1 become one-half of what it   
had been1 for if ,v did not alter1 the  
impelling force continuing the same1 the
 plane would rise and its flight no     
longer be horizontal1 unless the weight1
 now supposed to be constant1 were      
itself increased so as to restore       
horizontality4  ,i have repeated ,table 
,,xiii under the condition that the area
 be quadrupled1 while all the other     
conditions remain constant1 except the  
soaring speed1 which must vary4         

----------------------------------------
------------------          ,soaring    
,work4             ,weight4             
speed                                   
--------------------------------------- 
7feet per   ,work expended     ,weight  
of like                 second7   per   
minute4       planes   which            
,v4   ,a  #d sq4 ft4    #a ,h4,p4 will  
drive                       ,w  #ejj gr4
      through  the  air                 
#a4a lbs4     with velocity ,v4         
----------------------------------------
------------------                      
,foot-pounds4        ,pounds4           
#de    #ah4d              #a1bag        
#cj              #cj     #ag4d          
#fcd             #eg              #ae   
#ah4d                #cab               
#aaf              #aj     #bj4d         
#bcg            #aed               #e   
#bd4i                #adh               
#bdd               #b     #cb4h         
#hg            #dah                     
----------------------------------------

------------------   ,w is the weight of
 the single plane2 ,a is the area2 ,r is
 the  horizontal 8drift40 ,wt is the    
weight of like planes which #a ,h4 ,p4  
will drive at velocity ,v4 ,work is     
,,rv4   ,i4 ,if ,work is constant1 ,r   
varies as ,a4 ,,ii4 ,if ,r is constant1 
,work varies as #a_/7;,a74 ,,iii4 ,if ,w
 is constant while ,a varies1  the      
weight which #a ,h4 ,p4 will support    
varies as ,a4  ,the reader is reminded  
that these are simply deductions from   
the equations given in 8,aerodynamics10 
and that these deductions have not been 
verified by direct trial1 such as would 
show that no new conditions have in fact
 been introduced in this new            
application4 ,while1 however1 these     
deductions cannot convey any confidence 
beyond what is warranted by the original
 experiments1 in their general          
trustworthiness as working formul at    
this stage of the investigations1 we    
may1 ,i think1 feel confidence4  ,i may1
 in view of its importance1 repeat my   

remark that the relation of area and    
weight which obtain in practice1 will   
depend upon yet other than these        
theoretical considerations1 for1 as the 
flight of the free aerodrome cannot be  
expected to be exactly horizontal nor   
maintained at any constant small angle1 
the p#jdd data of 8,aerodynamics0       
7obtained in constrained horizontal     
flight with the whirling-table7 are here
 insufficient4 ,they are insufficient   
also because these values are obtained  
with small rigid planes1 while the      
surfaces we are now to use cannot be    
made rigid under the necessary          
requirements of weight1 without the use 
of guy wires and other adjuncts which   
introduce head resistance4  ,against all
 these unfavorable conditions we have   
the favoring one that1 other things     
being equal1 somewhat more efficiency   
can be obtained with suitable curved    
surfaces than with planes4#bb  ,i have  
made numerous experiments with curves of
 various forms upon the whirling-table1 

and constructed many such supporting    
surfaces1 some of which have been tested
 in actual flight4 ,it might be expected
 that fuller results from these         
experiments should be given than those  
now presented here1 but ,i am not yet   
prepared to offer any more detailed     
evidence at present for the performance 
of curved surfaces than will be found in
 ,part ,,iii4#bc ,i do not question that
 curves are in some degree more         
efficient1 but the extreme increase of  
efficiency in curves over planes        
understood to be asserted by ,lilienthal
 and by ,wellner1 appears to have been  
associated either with some imperfect   
enunciation of conditions which gave    
little more than an apparent advantage1 
or with conditions nearly impossible for
 us to obtain in actual flight4  ,all   
these circumstances considered1 we may  
anticipate that the power required 7or  
the proportion of supporting area to    
weight7 will be very much greater in    
actual than in theoretical 7that is1 in 

constrained horizontal7 flight1 and the 
early experiments with rubber-driven    
models were in fact successful only when
 there were from three to four feet of  
sustaining surface to a pound of weight4
 ,when such a relatively large area is  
sought in a large aerodrome1 the        
construction of light1 yet rigid1       
supporting surfaces becomes a nearly    
insuperable difficulty1 and this must be
 remembered as consequently affecting   
the question of the construction of     
boiler1 engines and hulls1 whose weight 
cannot be increased without increasing  
the wing area4   p#jde    ,,chapter ,,vi
  ,,balancing ,,the ,,aerodrome  ,by    
8balancing0 ,i mean such an adjustment  
of the mean center of pressure of the   
supporting surfaces with reference to   
the center of gravity and to the line of
 thrust1 that for a given speed the     
aerodrome will be in equilibrium1 and   
will maintain steady horizontal flight4 
8,balance0 and 8equilibrium0 as here    
used are nearly convertible terms4      

,,lateral ,,stability  ,equilibrium may 
be considered with reference to lateral 
or longitudinal stability4 ,the lateral 
part is approximately secured with      
comparative ease1 by imitating ,nature's
 plan1 and setting the wings at a       
diedral angle1 which ,i have usually    
made #aej4 ,stability in this sense     
cannot be secured in what at first seems
 an obvious way--by putting a           
considerable weight in the central plane
 and far below the center of gravity of 
the aerodrome proper1 for this          
introduces rolling4 ,thence ensues the  
necessity of carrying the center of     
gravity more nearly up to the center of 
pressure than would otherwise be        
necessary1 and so far introducing       
conditions which tend to instability1   
but which seem to be imposed upon us by 
the circumstances of actual flight4     
,with these brief considerations        
concerning lateral stability1 ,i pass on
 to the far more difficult subject of   
longitudinal stability4                 

,,longitudinal ,,stability  ,my most    
primitive observation with small gliding
 models was of the fact that greater    
stability was obtained with two pairs of
 wings1 one behind the other1 than with 
one pair 7greater1 that is1 in the      
absence of any instinctive power of     
adjustment74  ,this is connected with   
the fact that the upward pressure of the
 air upon both pairs may be resolved    
into a single point which ,i will call  
the 8center of pressure10 and which1 in 
stable flight1 should 7apart from the   
disturbance by the propeller thrust7 be 
over the center of gravity4 ,the center 
of pressure in an advancing inclined    
plane in soaring flight is1 as ,i have  
shown in 8,aerodynamics10 and as is     
otherwise well known1 always in advance 
of the center of figure1 and moves      
forward as the angle of inclination of  
the sustaining surfaces diminishes1 and1
 to a less extent1 as horizontal flight 
increases in velocity4 ,these facts     
furnish the elementary ideas necessary  

in discussing this problem of           
equilibrium1 whose solution is of the   
most vital importance in successful     
flight4 p#jdf  ,the solution would be   
comparatively simple if the position of 
the ,,cp could be accurately known      
beforehand1 but how difficult the       
solution is may be realized from a      
consideration of one of the facts just  
stated1 namely1 that the position of the
 center of pressure in horizontal flight
 shifts with the velocity of the flight 
itself1 much as though in marine        
navigation the trim of a steamboat's    
hull were to be completely altered at   
every change of speed4 ,it may be       
remarked here that the center of        
pressure1 from the symmetry of the      
aerodrome1 necessarily lies in the      
vertical medial plane1 but it may be    
considered with reference to its        
position either in the plane ,,xy 7cp#a7
 or in the plane ,,yz 7cp#b74 ,the      
latter center of pressure1 as referred  
to in the plane ,,yz1 is here           

approximately calculated on the         
assumption that it lies in the          
intersection of this vertical plane by a
 horizontal one passing through the     
wings half way from root to tip4        
,experiments made in ,washington1 later 
than those given in 8,aerodynamics10    
show that the center of pressure1 7cp#a7
 on a plane at slight angles of         
inclination1 may be at least as far     
forward as one-sixth the width from the 
front edge4 ,from these later           
experiments it appears probable also    
that the center of pressure moves       
forward for an increased speed even when
 there has been no perceptible          
diminution of the angle of the plane    
with the horizon1 but these             
considerations are of little value as   
applied to curved wings such as are here
 used4 ,some observations of a very     
general nature may1 however1 be made    
with regard to the position of the wings
 and tail4  ,in the case where there are
 two pairs of wings1 one following the  

other1 the rear pair is less efficient  
in an indefinite degree than the front1 
but the action of the wings is greatly  
modified by their position with         
reference to the propellers1 and from so
 many other causes1 that1 as a result of
 a great deal of experiment1 it seems   
almost impossible at this time to lay   
down any absolute rule with regard to   
the center of pressure of any pair of   
curved wings used in practice4  ,later  
experiments conducted under my direction
 by ,mr4 ,e4 ,c4 ,huffaker1 some of     
which will appear in ,part ,,iii1       
indicate that upon the curved surfaces  
,i employed1 the center of pressure     
moves forward with an increase in the   
7small7 angle of elevation1 and backward
 with a decrease1 so that it may lie    
even behind the center of the surface4  
,since for some surfaces the center of  
pressure moves backward1 and for others 
forward1 it would seem that there might 
be some other surface for which it will 
be fixed4 ,such a surface in fact       

appears to exist in the wing of the     
soaring bird4 ,these experiments have   
been chiefly with rigid surfaces1 and   
though some have been made with elastic 
rear surfaces1 these have not been      
carried far enough to give positive     
results4  ,the curved wings used on the 
aerodromes in late years have a rise of 
one in twelve1 or in some cases of one  
in eighteen1#bd and for these latter the
 following empirical local rule has been
 adopted3 p#jdg   ,the center of        
pressure on each wing with a horizontal 
motion of #bjjj  feet per minute1 is    
two-fifths of the distance from front to
 rear4  ,where there are two pairs of   
wings of equal size1 one following the  
other1 and placed at such a distance    
apart and with such a relation  to the  
propellers as here used1 the following  
wing is assumed to  have two-thirds of  
the efficiency of the leader per unit of
 surface4  ,if it is half the size of   
the leader1 the efficiency is assumed to
  be one-half per unit of surface4 ,if  

it is half as large again as  the       
leader1 its efficiency is assumed to be 
eight-tenths per unit  of surface4 ,for 
intermediate sizes of following wing1   
intermediate  values of the efficiency  
may be assumed4  ,these rules are purely
 empirical and only approximate4 ,as    
approximations1 they are useful in      
giving a preliminary balance1 but the   
exact position of the center of pressure
 is rarely determinable in either the   
horizontal or vertical plane1 except by 
experiment in actual flight4 ,the       
position of the center of gravity is    
found with all needed precision by      
suspending the aerodrome by a plumb-line
 in two positions1 and noting the point 
of intersection of the traces of the    
line1 and this method is so superior to 
that by calculation1 that it will       
probably continue in use even for much  
larger constructions than the present4  
,the principal factor in the adjustment 
is the position of the wings with       
reference to the center of gravity1 but 

the aerodrome is moved forward by the   
thrust of its propellers1 and we must   
next recall the fact of experiment that 
as it is for constructional reasons     
difficult to bring the thrust line in   
the plane of the center of pressure of  
the wings1 it is in practice            
sufficiently below them to tend to tip  
the front of the aerodrome upward1 so   
that it may be that equilibrium will be 
attained only when ,,cp#a is not over   
,,cg#a4  ,in the discussion of the      
equilibrium1 then1 we must consider also
 the effect of thrust1 and usually      
assume that this thrust-line is at some 
appreciable distance below the center of
 pressure4  ,we may conveniently        
consider two cases3  #a4 ,that the      
center of pressure is not directly over 
the center of gravity2 that is1         
,,cg#a;,,cp#a  a1 and estimate what the 
value of a should be in order that1     
during horizontal flight1 the aerodrome 
itself shall be horizontal2 or1 p#jdh   
#b4 ,consider that the center of        

pressure is directly over the center of 
gravity 7,,cp#a;,,cg#a  #j71 and in this
 case inquire what angle the aerodrome  
itself may take during horizontal       
flight4  ,first case4 ,the diagram      
7,fig4 #d7 represents the resultants of 
the separate system of forces acting on 
the aerodrome1 and these resultants will
 lie in a vertical medial plane from the
 symmetry of their disposition4  ,let af
 represent the resultant of the vertical
 components of the pressure on the      
wings2 the horizontal component will lie
 in the line ae4  ,illustration3 ,,fig4 
#d4 ,diagram showing relation under     
certain conditions of thrust1 ,c4 ,p4   
and ,c4 ,g4  ,let the center of gravity 
be in the line bd1 and the resultant    
thrust of the propellers be represented 
by cd4  ,let ,w  weight of aerodrome4   
,let ,t  thrust of propellers4  ,then if
 we neglect the horizontal hull         
resistance1 which is small in comparison
 with the weight1 equilibrium obtains   
when ,wab  ,tbd4  ,second case4 ,the    

diagram 7,fig4 #e7 represents the same  
system of forces as ,fig4 #d1 but in    
this case the point of support is       
directly over the center of gravity g1  
when the axis of the aerodrome is       
horizontal4  ,let ,w  weight of         
aerodrome4  ,let ,t  thrust of          
propellers4  ,let ,r  distance of ,,cg#b
 below ,,cp#b  ag4  ,let ,s  distance of
 thrust-line below ,,cp#b  ad4  ,if now 
the aerodrome under the action of the   
propellers be supposed to turn about the
 ,,cp#b 7or1 a7 through an angle 1 so   
that g takes the position g1 we p#jdi   
obtain by the decomposition of the force
 of gravity an element gk  ,w sin  which
 acts in a direction parallel to the    
thrust-line4  ,if we again neglect the  
horizontal hull resistance1 equilibrium 
will be obtained when       kgag  ,tad  
or  ,,wr sin   ,,ts                     
sin#a7,,ts_/,,wr7   ,illustration3 ,fig4
 #e4 ,diagram showing relation under    
certain conditions of thrust1 ,c4 ,p4   
and ,c4 ,g4  ,the practical application 

of these rules is greatly limited by the
 uncertainty that attaches to the actual
 position of the center of pressure1 and
 this fact and also the numerical values
 involved may be illustrated by         
examples4    ,,condition ,,of           
,,aerodrome ,,no4 #f1 ,,november #bh1   
#ahif  ,the weight was #ab4e kilos4 ,on 
,november #bh1 the steam pressure was   
less than #ajj pounds1 and the thrust   
may be taken at #d4e kilos4 ,the        
distance bd was #be cm4   ,hence        
#ab4e;ab  #d4ex#be cm4             ab   
#i cm4  ,this appears to give the       
position of ,,cp#a1 but ,,cp#a is a     
resultant of the pressure on both wings1
 and its position is determined by the  
empirical rule just cited4 ,we p#jej    
cannot tell in fact1 then1 with         
exactness how to adjust the wings so    
that ,,cg#a;,,cp#a may be #i cm41 and   
equilibrium was in fact obtained in     
flight when 7the empirically determined7
 ,,cg#a;,,cp#a  #c cm4  ,again1 let it  
be supposed that ,,cp#a was really over 

,,cg#a 4 4 4 4 ,the distance of the     
center of gravity below the center of   
pressure is #dc cm4  ,r4   ,then   sin#a
 7#d4ebe7_/7ab4edc7  #ab nearly4  ,the  
doubt as to the actual position of the  
resultant center of pressure1 then1     
renders the application of the rule     
uncertain4 ,in practice1 we are         
compelled 7unfortunately7 after first   
calculating the balance1 by such rules  
as the above1 and after it has been thus
 found with approximate correctness1 to 
try a preliminary flight4 ,having       
witnessed the actual conditions of      
flight1 we must then readjust the       
position of the wings with reference to 
the center of gravity1 arbitrarily1     
within the range which is necessary4    
,this readjustment should be small4     
,illustration3 ,,fig4 #f4 ,diagram      
showing effect of ,pnaud tail4  ,in the 
preceding discussion it has been assumed
 that1 if there is a flat tail or       
horizontal rudder1 it supports no       
portion of the weight4 ,this is not an  

indispensable condition but it is very  
convenient1 and we shall assume it4 ,in 
this case the action of the so-called   
,pnaud rudder becomes easily            
intelligible4 ,this is a device1 already
 referred to in ,chapter ,,ii1 made by  
,alphonse ,pnaud for the automatic      
regulation of horizontal flight1 and it 
is as beautiful as it is simple4  ,let  
,,ab 7,fig4 #f7 be a schematic          
representation of an aerodrome whose    
supporting surface is ,bb1 and let it be
 inclined to the horizon at such an     
angle  that its course at a given speed 
may be horizontal4 ,so far it does not  
appear that1 if the aerodrome be        
disturbed from this horizontal course1  
there is any self-regulating power which
 could restore it to its original       
course2 but now let there be added a    
flat tail ,,ac set at an angle  with the
 wing4 ,this tail serves simply for     
direction1 and not for the support of   
the aerodrome1 which1 as already stated1
 is balanced so that the ,,cg comes     

under the ,,cp of the wing ,bb4  ,it    
will be seen on a simple inspection that
 the tail under the given conditions is 
horizontal1 and that1 presenting its    
edge to the wind of advance1 it offers  
no resistance to it1 so that if the     
front rises and the angle  increases1   
the wind will strike on the under side  
of the tail and thereby tend to raise   
the rear and depress p#jea the front    
again4 ,if the angle  diminish1 so that 
the front drops1 the wind will strike   
the upper surface of the tail1 and      
equally restore the angle  to the amount
 which is requisite to give horizontal  
flight4 ,if the angle  is not chosen    
originally with reference to the speed  
so as to give horizontal flight1 the    
device will still tend to continue the  
flight in the straight line which the   
conditions impose1 whether that be      
horizontal or not4  ,from this          
description of its action1 it will be   
seen that the ,pnaud tail has the       
disadvantage of giving an undulatory    

flight1 if the tail is made rigid4 ,this
 objection1 however1 can be easily      
overcome by giving to it a certain      
amount of elasticity4 ,it does not      
appear that ,pnaud gave much attention  
to this feature1 but stress is laid upon
 it in the article 8,flight10 in the    
ninth edition of the ,encyclopdia       
,britannica1 and ,i have introduced a   
simple device for securing it4  ,the    
complete success of the device implies a
 strictly uniform velocity and other    
conditions which cannot well he         
fulfilled in practice4 ,nevertheless1 it
 is as efficient a contrivance for its  
object as has yet been obtained4  ,more 
elaborate devices have been proposed1   
and a number of them1 depending for     
their efficiency upon the action of a   
variety of forces1 have been constructed
 by the writer1 one of which will be    
described later4 ,this has the advantage
 that it tends to secure absolutely     
horizontal flight1 but it is much       
inferior in simplicity to the ,pnaud    

tail4  ,apart from considerations about 
the thrust1 the ,,cp is in practice     
always almost directly over the ,,cg1   
and this relationship is1 according to  
what has been suggested1 obtained by    
moving the supporting surfaces          
relatively to the ,,cg1 or vice versa1  
remembering1 however1 that1 as these    
surfaces have weight1 any movement of   
them alters the ,,cg of the whole1 so   
that successive readjustments may be    
needed4 ,the adjustment is further      
complicated by another important        
consideration1 namely1 that those parts 
which change their weight during flight 
7like the water and the fuel7 must be   
kept very near the ,,cg4 ,as the water  
and fuel tanks are fixed1 it appears1   
then1 that the center of gravity of the 
whole is practically fixed also1 and    
this consideration makes the adjustment 
a much more difficult problem than it   
would be otherwise4#be  ,illustration3  
,,pl4 #aa  ,,steel ,,frames ,,of        
,,aerodromes ,,nos4 #d1 #e1 #f4 #ahic1  

#ahie ,,and #ahif   p#jec    ,,chapter  
,,vii  ,,history ,,of ,,construction    
,,of ,,frame ,,and ,,engines ,,of       
,,aerodromes  ,during the years #ahib   
and #ahic1 it will be recalled1 four    
aerodromes1 known as ,nos4 #j1 #a1 #b1  
and #c1 had been built1 which were of   
two general types of construction4      
,first1 that represented by ,no4 #j1 in 
which a radically weak hull was made to 
support rods at the front and rear1 to  
which the wings and tail were attached4 
,this aerodrome was abandoned on account
 of the inability to provide it with    
sufficient power1 as well as because of 
its constructional weakness4 ,second1   
that type represented by ,nos4 #a1 #b1  
and #c1 in which a midrod was carried   
through from front to rear1 around which
 the hull supporting the machinery was  
built4 ,these models were much lighter  
than ,no4 #j1 but were all abandoned    
because it was found impossible to      
propel even the lightest of them4 ,while
 all these machines were in the         

strictest sense failures1 inasmuch as   
none of them was ever equipped with     
supporting surfaces1 yet the experience 
gained in the construction of them was  
of the very greatest value in           
determining the points at which strength
 was needed1 and in indicating the mode 
of construction by which strength and   
rigidity could be obtained4#bf    #ahic 
,another aerodrome1 known as ,no4 #d    
7shown in ,plate #aa71 was designed in  
the latter part of #ahib1 and by the end
 of ,march1 #ahic1 its construction was 
well under way4 ,it was of the second   
type1 in that the midrod was continuous1
 but it differed from the preceding     
forms in having the machinery 7boilers1 
burners1 and tanks7 attached directly to
 the midrod1 the hull now taking the    
form of a mere protective sheathing4 ,as
 in ,nos4 #b and #c1 two engines were   
used1 which were mounted on a           
cross-frame of light tubing attached to 
the midrod at right angles4 ,it had1 as 
at first constructed1 no provision for  

the generation of steam1 but only for   
carrying a reservoir of carbonic acid to
 supply gas for the engines4  ,the      
whole1 including wings1 tail1 and       
engines1 but without the carbonic acid  
reservoir1 weighed #ahih grammes 7#d4ah 
lbs474 ,a cylindrical reservoir1        
weighing #eba grammes 7#a4ad lbs47 and  
capable of holding #aejf cu4 cm4 7#ib   
cu4 in47 was constructed for this       
purpose1 and tested for #cj minutes with
 a pressure of #ajj p#jed atmospheres4  
,if the weight of the cylinder1 with its
 contents and adjuncts1 be taken as #hjj
 grammes 7#a4gf lbs471 the total weight 
of the aerodrome was #bfih grammes      
7#e4ie lbs474 ,the wings were plane     
surfaces of silk1 stretched over a very 
light frame1 with no intermediate ribs  
to prevent the wing from being          
completely distorted by the upward      
pressure of the air4 ,even if they had  
been sufficiently strong and stiff1 the 
total surface of both wings and tail was
 but #bfja sq4 cm4 7#b4h sq4 ft47 or    

approximately #j4e sq4 ft4 of supporting
 surface to the pound1 much less than   
was found adequate1 even under the most 
favorable circumstances4 ,the weight was
 much more than had been contemplated   
when the wings were designed1 yet1 if   
all the other features of the aerodrome 
had been satisfactory1 and sufficient   
power had been secured1 the work of     
providing suitable supporting surfaces  
would have been attempted4 ,but as it   
was found that the engines when supplied
 with carbonic-acid gas were unable to  
develop anything like the power         
necessary to propel the aerodrome1 and  
that the construction could be greatly  
improved in many other ways1 this       
aerodrome was entirely rebuilt4 ,the    
work of the engines with carbonic acid  
had been so completely unsatisfactory   
that the idea was entirely abandoned1   
and no further attempts to develop an   
efficient motor other than steam were   
made4  ,it now became realized more     
completely than ever before that the    

primary requisite was to secure         
sufficient power1 and that this could be
 obtained only by the use of steam4     
,this involved a number of problems1 all
 of which would have to be solved before
 any hope of a successful machine could 
be entertained4 ,in the first place1    
engines of sufficient power and         
strength1 but of the lightest possible  
construction1 must be built4 ,second1 a 
boiler must be constructed of the least 
possible weight1 which would develop    
quickly and maintain steadily steam at a
 high enough pressure to drive the      
engines4 ,this demanded some form of    
heating apparatus1 which could work     
under the adverse condition of enclosure
 in a narrow hull1 and steadily supply  
enough heat to develop the relatively   
large quantity of steam required by the 
engines4  ,the first of these problems1 
that of procuring suitable engines1 was 
at least temporarily solved by the      
construction of two engines with brass  
cylinders1 which had a diameter of #b4d 

cm4 7#j4ie in471 and a piston stroke of 
#e cm4 7#a4ig in474 ,the valve was a    
simple slide-valve of the piston type1  
arranged to cut off steam at one-half   
stroke4 ,no packing was used for the    
piston or the valve1 which were turned  
to an accurate fit to the cylinder and  
the steam-chest respectively4 ,in the   
engines built up to this time1 the parts
 had frequently been soldered together1 
and a great deal of trouble and delay   
had arisen from this cause4 ,in these   
new engines1 however1 as strong and     
careful a construction was made as was  
possible within the very narrow limits  
of weight1 with the result that the     
engines1 though by no means as efficient
 as those constructed later1 were used  
in all the experiments of #ahic and also
 during the first part of #ahid4 p#jee  
,as soon as these engines were          
completed1 in ,february1 #ahic1 a test  
was made of one of the cylinders1 steam 
being supplied from the boiler of the   
shop-engine4 ,the experiments were made 

with the ,prony brake1 and showed that  
at a speed of #ajjj revolutions per     
minute1 the power developed from a      
single cylinder was #j4bjh ,h4 ,p41 with
 a mean effective pressure in the       
cylinder of only about #ba pounds per   
square inch of piston area1 allowing a  
loss of #be per cent for the internal   
resistance of the engine4 ,this pressure
 was so much less than should have been 
obtained with the steam pressure used1  
that it now seems evident that the steam
 passages and ports were too small to   
admit and exhaust the steam with        
sufficient rapidity to do the work with 
the same efficiency that is obtained in 
common practice4 ,this1 however1 was not
 immediately recognized4 ,the piston    
speed at #ajjj ,r4 ,p4 ,m4 was #cbh feet
 per minute1 at which speed the steam at
 a pressure of #hj pounds should have   
been able to follow up the piston and   
maintain almost1 if not quite1 full     
boiler pressure to the point of cut-off1
 but it did not do so4  ,the problem of 

generating steam was much more difficult
 and required a long and tedious series 
of experiments1 which consumed the      
greater part of the year before any     
considerable degree of success had been 
attained4 ,in the course of these       
experiments many unexpected difficulties
 were encountered1 which necessitated   
the construction of special forms of    
apparatus1 which will be described at   
the proper point4 ,numerous features of 
construction1 which seemed to be of     
value when first conceived1 but which   
proved useless when rigorously tested1  
will be noted here1 whenever a knowledge
 of their valuelessness may seem to be  
of advantage to the reader4  ,the boiler
 was necessarily developed              
simultaneously with the development of  
the heating apparatus1 and in the       
following pages1 as far as possible1    
they will be treated together2 but often
 for the sake of clearness and to avoid 
repetition1 separate treatment will be  
necessary4  ,at the beginning of these  

experiments1 there was much doubt as to 
whether alcohol or gasoline would be    
found most suitable for the immediate   
purpose4 ,an alcohol burner had been    
used in connection with the earliest    
aerodrome1 ,no4 #j1 but from the results
 obtained with it at that time1 there   
seemed to be little reason to hope for  
success with it4 ,it is to be premised  
that the problem1 which at first seemed 
insoluble1 was no less than to produce  
steam for something like #a ,h4 ,p4 by a
 fire-grate1 which should occupy only a 
few cubic inches 7about the size of a   
clenched hand7 and weigh but a few      
ounces4 ,it had to be attacked1 however1
 and as alcohol offered the great       
advantage of high calorific properties  
with freedom from all danger of         
explosion1 it was at first used4  ,early
 in #ahic1 it occurred to me to modify  
the burner so as to make it essentially 
an aeolipile1 and in ,april of that year
 the first experimental aeolipile model 
shown at ,a 7,plate #ab7 was made4 ,it  

was very small and intended for the     
p#jef demonstration of a principle      
rather than for actual service1 but the 
construction of this small aeolipile was
 an epoch in the history of the         
aerodrome4 ,it furnished immensely more 
heat than anything that had preceded it1
 and weighed so little and worked so    
well that in ,may the aeolipile marked  
,b was made4 ,in this design two pipes  
were led from the upper portion of the  
cylinder1 one to a large ,bunsen burner 
which heated the boiler1 the other to a 
small burner placed under the tank to   
vaporize the alcohol4 ,this was followed
 by the one shown at ,c1 wherein the    
heating burner was smaller and the gas  
pipe1 leading to the main burner1       
larger4  ,figures ,d1 ,e1 ,f1 and ,g    
7,plate #ab7 were really continuations  
and improvements of the same idea4 ,in  
,c there was simply a tube or flue      
through the tank2 in ,f1 however1 this  
tube discharged into a smoke-stack      
fastened to the end of the cylinder1    

while in ,g the flue turned upward      
within the tank itself and discharged   
into the short stack on top4 ,the object
 of these changes was to increase the   
draft and heating power of the small    
flame1 so that the gas would be more    
rapidly generated and a greater quantity
 be thus made available for use under   
the boiler in a unit of time4 ,they     
were1 however1 though improvements in a 
construction which was itself a great   
advance1 still inadequate to give out a 
sufficient amount of heat to meet the   
excessive demands of the required       
quantity of steam4 ,the boilers in      
connection with which these aeolipiles  
were used must now be considered4  ,the 
first boiler ,e 7,plate #ac7 made during
 this year was a double-coil boiler of  
the ,serpollet type1 formed of #ai feet 
of copper tubing having an internal     
diameter of about #a_/h inch4 ,attached 
to the boiler was a small vertical drum1
 from the top of which steam was led to 
the engine1 a pipe from the bottom      

leading to the pump4 ,this boiler was   
tested in ,april with an alcohol heater1
 the pump in this trial being worked by 
hand4 ,this apparatus developed a steam 
pressure varying from #be to #ge pounds1
 which caused the engines to drive a #fj
 cm4 propeller of #a4be pitch-ratio #efe
 revolutions per minute4 ,the greatest  
difficulty was experienced in securing a
 sufficient and uniform circulation in  
the boiler coils4 ,the action in the    
present case was extremely irregular1 as
 the pressure sometimes rose to #aej    
pounds1 driving the engines at a        
dangerous speed and bending the         
eccentric rod1 while at other times it  
would fall so low that the engines      
stopped completely4  ,as the pump used  
in this trial had proved so             
unsatisfactory and unreliable1 it was   
replaced by a reservoir of water having 
an air-chamber charged to #aj           
atmospheres1 the flow from which could  
apparently be regulated with the        
greatest nicety by a needle valve at the

 point of egress2 but for some reason   
its performance was unsatisfactory and  
remained so after weeks of experiment4  
,illustration3 ,,pl4 #ab  ,,burners1    
,,aeolipiles1 ,,and ,,separators        
,illustration3 ,,pl4 #ac  ,,boilers ,,of
 ,,aerodromes  ,there was used in       
connection with this device the         
double-coil boiler shown at ,f 7,plate  
#ac7 which was made of tubes flattened  
so as to be nearly capillary4 ,the idea 
of this was to obtain a larger heating  
surface and a smaller volume of p#jeg   
water1 so that by proper regulation at  
the needle valve1 just that quantity    
would be delivered which could be       
converted into steam in its passage     
through the coils1 and be ready for use 
in the engines as it left the boiler at 
the farther extremity4 ,the results     
obtained from this were an improvement  
over those from the original coil1 and a
 third set of coils 7,g1 in ,plate #ac7 
was made4 ,this boiler consisted of     
three flattened tubes superposed one    

over another4  ,these two boilers were  
tried by placing them in a charcoal fire
 and turning on an alcohol blast1 while 
water from a reservoir under constant   
air pressure was forced through them    
past a pin valve4 ,the result was that  
the two-stranded coil supplied steam at 
from #aj to #dj pounds pressure to run  
the engines at about #djj revolutions   
per minute4 ,the pressure rose steadily 
for about #dj seconds and then suddenly 
fell away1 though the coils were        
red-hot1 and neither the water nor the  
alcohol was exhausted--apparently       
because of the irregularity of the      
supply of water1 due to the time taken  
by it after passing the valve to fill   
the considerable space intervening      
between that point and the boiler4  ,an 
attempt was made to overcome this       
difficulty by putting a stop-cock       
directly in front of the boiler so that 
the water1 while still under the control
 of the needle valve1 could be turned in
 at once2 the alcohol blast was also    

arranged to be turned on or off at      
pleasure1 and provision was made1 by    
taking out the end of the flue inclosing
 the boiler1 to provide for an increased
 air supply4 ,with this arrangement a   
flame eight or nine inches long was     
obtained1 but a test showed that not    
more than #be grammes of water per      
minute passed through the tubes1 which  
was not enough4  ,further tests with    
these boilers were so far satisfactory  
as to show that with the flattened-tube 
,serpollet boiler1 comprising from #fj  
to #hj feet of tubing1 from #hj to #ajj 
pounds pressure of steam could be       
maintained1 but not steadily4 ,as there 
were difficulties in flattening the     
tubes to make a boiler of this sort1 a  
compromise was effected in the          
construction of the one shown at ,h     
7,plate #ac71 which was made of light   
copper tubes #e mm4 in diameter1 laid up
 in three lengths of #f metres each4    
,the ends of these coils were so        
attached to each other that the water   

entering at one end of the smallest coil
 would pass through it and then enter   
the middle coil1 whence it passed       
through the third or outer coil4 ,two   
sets of these coils were made and placed
 in the thin sheathings shown in the    
photograph4 ,repeated experiments with  
these boilers demonstrated that the     
pressure did not rise high enough in    
proportion to the heat applied1 and that
 even the pressures obtained were       
irregular and untrustworthy4 ,the       
principal difficulty still lay in       
maintaining an active and uniform       
circulation through the coils1 and for  
this purpose the water reservoir under  
constant air pressure had proved itself 
inadequate4 ,this pointed to a return to
 the use of the force pump1 the         
construction of which had hitherto      
presented so many special difficulties  
that it had been temporarily abandoned4 
p#jeh  ,a further difficulty experienced
 in the use of these boilers had been   
that of obtaining dry steam for the     

engines1 as during the early experiments
 the steam had been delivered directly  
into the engines from the boiler coils4 
,but in ,august the writer devised a    
chamber1 known as the 8separator10 where
 it had an opportunity to separate from 
the water and issue as dry steam1 or at 
least approximately dry steam4 ,this was
 an arrangement familiar in principle to
 steam engineers under another form1 but
 it was one of the many things which1 in
 the ignorance of steam engineering the 
writer has already freely admitted1 he  
had to reinvent for himself4  ,at about 
the same time1 a new pump was designed  
to drive the water from the bottom of   
the separator1 which served the double  
purpose of steam drum and reservoir1    
into the coils4 ,this pump had a        
diameter of #d4h cm41 and was run at    
#ahj strokes per minute4  ,the result of
 the first experiments with these       
improvements demonstrated that1 within  
certain limits1 the amount of water     
evaporated is proportional to the       

circulation1 and in this boiler the     
circulation was still the thing that was
 at fault4 ,finally1 the results of the 
experiments with the two-stranded1      
triple-coil boiler may be summed up in  
the statement that it was possible to   
maintain a pressure of #hj pounds1 and  
that with it the engines could be made  
to develop from #j4c to #j4d ,h4 ,p4 at 
best4 ,it weighed #fej grammes 7#a4dc   
pounds7 without the asbestos jacket4    
,about this time the writer had the good
 fortune to secure the temporary        
services of ,dr4 ,carl ,barus1 an       
accomplished physicist1 with whose aid a
 great variety of boilers were          
experimented on4  ,the next form of     
boiler tested was that shown at ,n      
7,plate #ac71 made on a system of coils 
in parallel1 of which there were twenty 
complete turns4 ,in the first test it   
generated but #bj pounds of steam1      
because the flame refused to work in the
 colder coils4 ,the work of this boiler 
was very unsatisfactory1 and it was only

 with the greatest difficulty that more 
than ten pounds pressure could be       
maintained4 ,there was trouble1 too1    
with the circulation1 in that when the  
flame was in full play the pump seemed  
to meet an almost solid resistance1 so  
that it could not be made to do its     
work4  ,a new boiler was accordingly    
made1 consisting of three coils of four 
strands each4 ,with this the pump worked
 easily1 but whereas it was expected to 
get #abj pounds pressure1 the best that 
could be obtained was #gj pounds4 ,the  
outer coil was then stripped off1 and a 
trial made in which everything ran      
smoothly and the pressure mounted       
momentarily to #ij pounds4 ,after some  
adjustment1 a mean pressure of #hj      
pounds was obtained1 giving #gcj        
revolutions of the engine per minute1   
with an indicated horse-power of #j4cb4 
,it was shown in this work that1 within 
certain limits1 steam is generated most 
rapidly when it is used most rapidly1 so
 that two engines could be used p#jei   

almost as well as one1 the reason       
apparently being that the rapid         
circulation increased the steam         
generating power of the boiler1 and that
 the engines worked best at about #hj   
pounds4 ,it was also found that a larger
 tubing was better than the small1      
weight for weight1 this fact being due  
to the greater ease with which          
circulation could be maintained1 since  
fewer coils were necessary in order to  
obtain the same external heating        
surface4 ,the pressure in the coils and 
the separator was also much more nearly 
equalized4 ,the result was that the     
boiler temporarily approved was one made
 of tubing #f4ce mm4 7#j4be inch7 in    
diameter1 bent into a two-coil1         
two-stranded boiler1 having sixteen     
complete turns for each strand in each  
coil4 ,the total weight was #efj grammes
 7#a4bc pounds7 with a total heating    
surface of #acjj sq4 cm4 7#a4d sq4 ft474
  ,the separator used in the experiments
 made during ,august and ,september was 

of a form in which the water was forced 
below a series of partitions that       
prevented it from following the steam   
over into the cylinders of the engines4 
,it weighed #daj grammes 7#j4i pound7   
and was most conveniently worked with   
#gjj grammes 7#a4ed pounds7 of water4   
,the boiler and separator together      
weighed #igj grammes 7#b4a pounds74  ,a 
new separator was1 however1 designed1   
which was horizontal instead of         
vertical1 as it was intended that it    
should be placed just below the midrod4 
,another form1 devised for              
constructional reasons1 consisted of a  
cylinder in which a pump was imbedded4  
,heretofore the pump used had been      
single-acting1 but it was now proposed  
to make a double-acting pump4 ,upon     
testing this apparatus1 it was found    
that when using an aeolipile1 it took   
#aej grammes of alcohol to evaporate    
#fjj grammes of water4 ,it was evident  
that the latter was used very           
wastefully1 so that the thermal         

efficiency of the engine was not over   
one per cent2 but it was also evident   
that1 under the necessity of sacrificing
 everything to lightness1 this waste was
 largely inevitable4  ,about the middle 
of ,october1 another boiler 7,o1 ,plate 
#ac7 was made1 which consisted of two   
coils wound in right and left hand      
screw-threads1 one fitting loosely over 
the other1 so as to make a cylindrical  
lattice-work #cb cm4 7#ab4f in47 long4  
,each coil contained two strands of     
copper tube #j4c mm4 thick1 and weighing
 #ed grammes to the metre 7#j4jcf pound 
to the foot74 ,the inner coil had a     
diameter of #e4fc cm4 7#b4bb in471 with 
nine turns of tube to the strand1 the   
two strands making a length of #cai cm4 
7#aj4e feet7 for the coil4 ,the outer   
coil had a mean diameter of #f4hh cm4   
7#b4ga in47 and a length of #chh cm4    
7#ab4g feet7 for the two strands4 ,the  
total length of the two coils was1      
therefore1 #gjg cm4 7#bc4b feet71 with a
 heating surface of about #adae sq4 cm4 

7#a4eb sq4 ft47 and a total weight of   
#chb grammes 7#j4hd pound74  ,the       
results obtained with this boiler were  
so far satisfactory as to show that1    
under the most favorable conditions1    
when air was supplied in unlimited      
quantities and there were no disturbing 
currents to put out or interfere with   
the work p#jfj of the burners1 steam    
could be supplied at a sufficient       
pressure to run the engines4 ,it was    
realized1 however1 that the conditions  
in flight would be very different1 and  
that in order to protect the apparatus  
from the wind1 some sort of protecting  
covering would have to be devised1 which
 would of itself introduce new          
difficulties in providing the burners   
with a proper and uniform draft4        
,illustration3 ,,fig4 #aj4 ,diagram of  
pendulum4  ,the hull1 as at first       
constructed1 consisted of a cylindrical 
sheathing open in front1 through the    
rear end of which the boiler and        
aeolipile projected inward1 so that the 

air taken in at the front would be drawn
 through the boiler and hearth to the   
exclusion of lateral currents4 ,in the  
first tests1 however1 after the hull had
 been applied1 it was impossible to     
secure a proper rate of combustion1     
nearly the whole hull being filled with 
a bluish flame1 while only a very small 
portion of the gases of combustion      
passed into the coils of the boiler4    
,the remedy for this lay in obtaining an
 increased draft1 and a small stack was1
 therefore1 arranged to carry off the   
products of combustion4 ,this proved    
inadequate1 and it was only after       
several weeks of experiment with various
 types of smoke-stack1 and constant     
alteration of the aeolipile1 that it was
 possible to make the apparatus work    
p#jfa efficiently when it was inside the
 hull4 ,finally such a degree of success
 was attained that the burners could be 
kept lighted even when the aerodrome was
 placed in a considerable artificial    
breeze1 created by a blower in the shop4

  ,in connection with these tests of the
 engines and boilers1 some method was   
desired1 in addition to the ,prony brake
 tests1 by which the thrust of the      
propellers when driven by the engines at
 various speeds could be measured       
accurately and in terms which would be  
readily available in judging whether the
 aerodromes were ready to be given an   
actual trial in free flight4 ,such a    
method was found in the use of an       
apparatus known as the 8pendulum10 which
 was introduced near the end of #ahib1  
but was not generally used until the end
 of #ahic4 ,after this time1 however1   
this test was made a condition          
prerequisite to taking any of the       
aerodromes into the field1 and proved of
 the greatest assistance in estimating  
the probable outcome of the trials4     
,the apparatus used1 which is           
diagrammatically shown in ,fig4 #aj1 was
 extremely simple both in theory and    
operation4 ,it consisted primarily of a 
horizontal arm ,,ac carrying the        

knife-edge ,b by which it is pivoted on 
each side on supporting beams not shown4
 ,depending from ,,ac is the light      
vertical arm ,,de1 rigidly joined to it 
and carrying the lower horizontal arm   
,,fg1 all of which are braced together  
so as to maintain the arm ,,de          
constantly perpendicular to ,,ac4 ,to   
this arm ,,fg the model was rigidly     
attached with its center of gravity in  
line with the vertical arm ,,de and its 
weight increased by the addition of     
properly disposed flat weights1 in order
 to make the angle of lift for a given  
thrust of the propellers smaller and    
less likely to interfere with the       
working of the boiler and separator4    
,before the actual test of the 8lift0   
could be made1 it was necessary to know 
the exact distance of the vertical      
center of gravity of the model and the  
extra weights from the knife-edge ,b4   
,this was determined by the following   
method3 ,a known weight was suspended   
from the arm ,,ab at some arbitrarily   

selected distance from the point ,b4    
,this weight caused the perpendicular   
arms ,,ab and ,,de to rotate through an 
angle1 1 which was measured on the scale
 ,,kl4 ,knowing1 then1 the weight on the
 arm ,,ab1 its point of application1 the
 weight of the aerodrome suspended on   
the arm ,,de1 and the angle of rotation1
 it is easy1 by a simple application of 
trigonometric functions1 to determine   
the distance of the center of gravity of
 the model from the point ,b4  ,in a    
test of ,aerodrome ,no4 #f made on      
,september #bc1 #ahih1 the weight       
suspended from ,,ab was #aj1jjj grammes1
 its point of application #ej cm41 the  
model was weighted to #bj1dej grammes1  
and the angle of rotation1 1 was #g #b4 
,letting y equal the distance of the    
,,cg from ,b1 we may equate the balanced
 forces thus3   #aj1jjjej cos #g #b     
#bj1dejy sin #g #b  #aj1jjjej cot #g #b 
#bj1dejy                  y  #aih4b cm4 
,having determined this distance1 the   
weight on ,,ab was removed and the      

aerodrome was allowed to regain its     
former position4 ,the distance of the   
center of thrust from ,b was then       
measured4 ,the engine was next started  
and the number of revolutions of the    
propellers counted by a tachometer4 ,the
 thrust of the propellers1 acting       
perpendicularly to the arm ,,bd1        
produced rotation around the point ,b1  
the angle of which was measured as      
above4  ,in the power test of ,no4 #f1  
the following data were obtained3   ,w  
weight of aerodrome  #bj1dej grammes4   
angle of lift  #ai #cj4  ,distance of   
,,cg from center of rotation  #aih4b cm4
  ,distance of center of thrust from    
center of rotation  #ahf4c cm4  ,as the 
propeller thrust and the weight of the  
model are forces acting in opposite     
directions at known distances from a    
center of rotation1 letting ,l equal the
 8dead lift10 we may express the        
equation thus3   ,w sin #aih4b          
,l#ahf4c1              ,l               
7#aih4b_/ahf4c7sin #ai #cjbj1dej1       

,l  #g1bfc grammes 8dead lift40  ,the   
flying weight of ,aerodrome ,no4 #f was 
#ab1jfd grammes1 and the per cent of    
this weight lifted was1 therefore1      
#g1bfc_/ab1jfd  #fj4c4  ,this was much  
more than was necessary for flight1 but 
in order to insure successful flights   
and avoid delay1 the rule was made in   
#ahie that no aerodrome was to be       
launched until it had previously        
demonstrated its ability to generate    
enough power to maintain for at least   
two minutes a lift of #ej per cent of   
the total flying weight4 ,at the same   
time other important data were obtained1
 such as the steam-pressure1 the time   
required to raise sufficient steam1 the 
total time of the run1 and the general  
working of the boilers and engines4  ,as
 will easily be seen1 these tests       
afforded a most satisfactory basis of   
judging what the aerodromes might be    
expected to do in actual flight if the  
balancing were correct4  ,at this time1 
,october1 #ahic1 the aerodrome 7,old    

,no4 #d7 was practically complete1 and  
the most anxious thought was given to   
lightening it in every way consistent   
with the ever-present demand for more   
power1 which necessitated an increase in
 the weight of both burners and boilers 
to supply the requisite steam4  ,on     
,november #ad1 when the aerodrome was   
prepared to be shipped to ,quantico for 
trial1 its condition was about as       
follows4 ,the steam-generating          
apparatus--the parts of which were of   
substantially the forms last described1 
although some slight improvements had   
been introduced--had been developed to  
p#jfc such a point that a pressure of   
from #gj to #hj pounds of steam could be
 maintained for #gj seconds1 when it was
 tested in the shop4 ,what it would do  
under the unfavorable conditions imposed
 by flight was to be learned only by    
trial4  ,at this pressure1 the engines1 
the efficiency of which had been        
increased by an improvement in packing1 
would develop approximately #j4d        

indicated ,h4 ,p41 while at #aje pounds 
pressure they at times developed as much
 as #j4h ,h4 ,p4 ,when the aerodrome was
 tested on the pendulum1 these engines1 
when making less than #gjj revolutions  
per minute1 lifted over #dj per cent of 
the total flying weight4  ,the          
propellers used at this time were       
accurate helices1 having a diameter of  
#fj cm41 a width of blade of            
approximately #cf degrees1 and a        
pitch-ratio of #a4be4 ,they were formed 
of wood1 and were bushed with brass     
where they were attached to the shafts4 
,,aerodrome ,,old ,,no4 #d ,,as         
,,prepared ,,for ,,flight ,,before      
,,being ,,shipped ,,for  ,,trial ,,on   
,,november #ad1 #ahic                   
----------------------------------------
--------        ,part4                  
,copper4,steel4,brass4,iron4            
----------------------------------------
--------                            gms4
  gms4  gms4  gms4  ,aeolipile          
#bjj    44    #ib    44  ,boiler        

#cej    44    #cg    44  ,separator and 
pumps       #cjj    #cj   #ajj    #bj   
,engine and frame           44   #cej   
#egj    44  ,midrod 7#bjj cm4 long7     
44   #bbj    44    44  ,two smoke-stacks
           #gj    44    44    44        
,asbestos jacketing         44    44    
44    44  ,air chamber                44
    44    44    #hb  ,spider between    
boiler                          and     
burner               #cb    44    44    
44  ,intake valve               44    44
    #ae    44                           
------------------------  ,total        
#ieb   #fjj   #had   #ajb               
------------------------  ,hull         
#ej    44    #ej    44  ,pins for       
starter           44    #ae    44    44 
,two large wings and tail   44    44    
44    44  ,buffer and steerer         44
    44    44    44  ,propellers         
44    44    44    44                    
------------------------  ,total        
#ej    #ae    #ej    44                 
------------------------  ,grand total  

#ajjb   #fae   #hfd   #ajb              
,density                   #h4i   #g4h  
#h4e   #g4e  ,volume 7cu4 cms47         
#aac    #gi   #ajb   #acf  ,alcohol     
44    44    44    44  ,water            
44    44    44    44                    
------------------------  ,total        
44    44    44    44  ,density          
44    44    44    44                    
,volume 7cu4 cm47           44    44    
44    44                                
----------------------------------------
--------                                
----------------------------------------
--------------------------        ,part4
              ,wood ,mica and ,fluid4   
,total and mean                         
and  asbestos4           weights4       
silk4                                   
----------------------------------------
--------------------------              
gms4    gms4  gms4  gms4  ,aeolipile    
44      44    44    #bib  ,boiler       
44      44    44    #chg  ,separator and
 pumps        44      44    44    #dej  

,engine and frame           44      44  
44    #ibj  ,midrod 7#bjj cm4 long7     
44      44    44    #bbj  ,two          
smoke-stacks           44      44    44 
#gj  ,asbestos jacketing         44     
#ej    44     #ej  ,air chamber         
44      44    44     #hb  ,spider       
between boiler                          
and burner               44      44     
44     #cb  ,intake valve               
44      44    44     #ae                
--------------------------  ,total      
44      #ej    44   #beah  #e4ed lbs4   
--------------------------  ,hull       
44      #be    44    #abe  ,pins for    
starter           44      44    44      
#ae  ,two large wings and tail  #ega    
44    44    #ega  ,buffer and steerer   
#ec      44    44     #ec  ,propellers  
#bej      44    44    #bej              
--------------------------  ,total      
#hgd      #be    44   #ajad    #b4cc    
lbs4                                    
--------------------------     ----     
,grand total               #hgd      #ge

    44   #cecb   #g4gg lbs4             
,density                   #j4h     #c4j
    44   #b4dh      ,i4  ,volume 7cu4   
cms47        #ajib      #be    44       
#adbe   #hg cu4 ins4  ,alcohol          
44      44   #ajj    #ajj  ,water       
44      44   #ejj    #ejj               
--------------------------  ,total      
44      44    44   #dacb   #i4a lbs4    
,density                    44      44  
#abe                                    
#ejj  #b4ja    ,,ii4  ,volume 7cu4 cm47 
44      44    44   #bjej                
----------------------------------------
--------------------------  ,permanent  
air spaces3         in midrod1 vol4     
#cee cc4  in engine frame1 vol4  #ajj   
cc4                                     
volume as per ,,ii4   #bjej cc4         
,density  #dacb_/beje  #a4fe ,,iii4     
--------                                
#beje cc4   ,the total flying weight of 
,old ,no4 #d1 including fuel and water1 
was #dacb grammes 7#i4a lbs471 a much   
larger weight than had been contemplated

 when the original designs were made4 ,a
 detailed statement of the weights of   
the various parts of the aerodrome1     
together with some data as to its       
density1 is given on the preceding page4
 ,there were provided in the wings and  
tail approximately #b sq4 ft4 of        
supporting surface to the pound of      
weight1 which would have been barely    
sufficient to sustain the aerodrome1    
even if it had been successfully        
launched and the wings had been built   
much stronger than the flimsy           
construction in use at this time4  ,an  
air chamber1 which served the double    
purpose of floating the aerodrome and of
 providing a moveable weight by which   
the center of gravity could be shifted  
to the proper position relatively to the
 center of pressure1 was constructed of 
the thinnest sheet-iron and attached to 
the midrod4  ,this aerodrome1 the fifth 
in actual construction1 and the first1  
after years of experiment1 to be carried
 into the field1 was transported to     

,quantico1 where the first trial with it
 was made on ,november #bj1 under the   
conditions described in ,chapter ,,ix4  
#ahid  ,the aerodrome1 ,no4 #d1 which   
has just been described1 had not been   
put to the test of an actual flight1 for
 reasons connected with the difficulties
 of launching1 which are more fully     
described elsewhere2 but1 when the      
completed machine was more fully studied
 in connection with the unfavorable     
conditions which it was seen would be   
imposed on it in trials in the open air1
 many possibilities for improvement     
presented themselves4 ,it was seen1 for 
instance1 that a better design might be 
made1 in which the engines1 boiler and  
aeolipile might be placed so that the   
center of gravity of each would lie in  
the same vertical plane as the central  
line of the aerodrome4 ,in order to do  
this the construction of a single       
midrod1 which was the distinguishing    
feature of ,old ,no4 #d1 had to be      
essentially departed from1 the midrod of

 this new one1 ,no4 #e1 being opened out
 into two rods1 so to speak1 which were 
bent out so that the open space between 
them furnished a sufficiently large hull
 space to hold the entire power         
generating apparatus4 ,in arranging the 
machinery within this hull1 it was      
provided that1 as the water and fuel    
were expended1 the center of gravity of 
the aerodrome would shift little1 and1  
if at all1 backward relatively to the   
center of pressure4  ,instead of the two
 small engines1 which it will be        
remembered were mounted on the          
cross-frame in ,no4 #d1 a single engine 
with a larger cylinder1 having a        
diameter of #c4c cm4 7#a4c in47 and a   
stroke of #g cm4 7#b4gf in471 capable of
 developing about #a ,h4 ,p4 was used4  
,this engine was mounted within the hull
 near the forward end and drove the     
propellers by suitable gearing4 p#jfe   
,in addition to these radical changes   
many important improvements were made in
 the different parts4 ,internal         

compartments were built in the          
separator1 so that even if the water was
 displaced by the pitching of the       
aerodrome1 it could still perform its   
functions properly4 ,the pump was       
provided with a ratchet1 so that it     
could be worked by hand after the       
burners were lighted1 and before enough 
steam had been raised to enable the     
engine to run it4 ,an active circulation
 was thus maintained in the coils of the
 boiler as soon as the burner was       
lighted and before the engine was       
started1 which prevented the tubing from
 being burnt out1 as had frequently     
happened previously4 ,the wing          
construction was also improved and many 
other changes were introduced1 which    
will be treated separately4  ,in the    
meantime1 ,no4 #d1 which had been       
damaged in the attempted launching in   
,november1 #ahic1 was strengthened and  
prepared for another trial which took   
place in ,january1 #ahid4  ,by the end  
of the first week in ,february1 the     

engine of ,no4 #e was ready for trial1  
and with a boiler pressure of about #hj 
pounds per square inch1 apparently      
developed #j4ef ,h4 ,p4 on the ,prony   
brake1 when making #hjj revolutions per 
minute4 ,to accomplish this called for  
such good distribution of steam in the  
cylinder1 that it is doubtful if the    
power could be exceeded at that speed   
and pressure4  ,it was1 however1        
apparent that it was desirable to have a
 boiler capable of supplying steam for  
at least one horse-power1 and that in   
order to do this1 there must be an      
improvement in the aeolipiles4 ,the     
problem consisted in arranging to       
evaporate more than #ejj cu4 cm41 and in
 fact as nearly as possible #ajjj cu4   
cm4 7#fa cu4 in47 of water per minute1  
and1 since from #bjj to #cjj cu4 cm4 per
 minute had already been evaporated1    
this was not regarded as impossible of  
accomplishment4 ,the theoretical        
advantages of gasoline had for a long   
time been recognized1 as well as the    

very practical advantage possessed by it
 of keeping lighted in a breeze1 and    
several attempts had been made during   
the latter part of the previous year to 
construct a suitable burner for use with
 it4 ,these had not been very           
successful2 but in view of the          
increasing demand for a flame of greater
 efficiency than that of the alcohol    
aeolipiles1 it was decided to resume the
 experiments with it4  ,accordingly1 a  
gasoline evaporator was tried1          
consisting in the first experiment of a 
gasoline tank with nine flues1 through  
which steam was passed4 ,a flow of steam
 gave a rapid evaporation of gasoline   
when the pressure did not exceed #e     
pounds4 ,the chief difficulty with the  
burner employed was that the supply of  
gasoline gas would rise and fall as the 
steam rose and fell1 conditions just the
 opposite of what was really desired4   
,on the other hand1 it was thought that 
this gasoline tank would form a real    
condenser for the steam1 so that a p#jff

 portion of the exhaust steam would be  
condensed and be available for use in   
the boiler again4 ,the gasoline vapor   
had many advantages over the alcohol2   
but it was at first possible to         
evaporate only #abj cu4 cm4 of gasoline 
in a minute4  ,in the experiments that  
were made at this time 7,march #i7 with 
gasoline1 the main object in view was to
 obtain a smooth blue flame at #aj      
pounds pressure4 ,there had been        
failures to accomplish this1 owing to   
the high boiling point of the liquid1   
and while the work was in progress it   
was still evident that the problem of   
the boiler and the flame which was to   
heat it had not been solved4 ,a ,prony  
brake test gave1 at #acj pounds         
pressure1 #a4a ,h4 ,p4 with about #ajjj 
revolutions of the propellers2 but this 
was with steam supplied from the boiler 
of the stationary shop engine4  ,on     
,april #a1 #ahid1 the following record  
was made of the condition of ,aerodrome 
,no4 #e3   8,the wings1 the tail1 and   

the two #hj cm4 propellers1 as well as  
the  two smaller propellers1 are ready4 
,the cylinders1 gear1 pump1 and  every  
essential of the running gear1 are in   
place4 ,the boilers1  separators1 and   
adjuncts are still under experiment1 but
 may be  hoped to be ready in a few     
days4 ,at present1 the boilers give from
  #dej to #fjj grammes of mixed steam   
and water per minute4 ,with #acj  pounds
 of steam1 the engine has actually      
developed at the brake1  without        
cut-off1 considerably more than #a ,h4  
,p41 so that it may be  confidently     
considered that at #aej pounds1 with    
cut-off1 it will  give at least #j4h ,h4
 ,p41 if it works proportionately well40
  ,the delays incident to the           
accomplishment of the work in hand were 
always greater than anticipated1 as is  
instanced by the fact that it was the   
latter part of ,september before the    
work was actually completed4 ,the       
greater part of this delay was due to   
the necessity for a constant series of  

experiments during the spring and summer
 to determine the power that it was     
possible to obtain with the various     
styles of boilers1 aeolipiles1 and      
gasoline burners4  ,while ,no4 #e was   
thus under construction1 new and        
somewhat larger engines had been built  
for ,no4 #d1 the work on them having    
been begun in ,january4 ,the cylinders  
of these engines1 which are more fully  
described in connection with ,aerodrome 
,no4 #f1 were #b4h cm4 in diameter1 with
 a #e cm4 stroke1 each cylinder thus    
having a capacity of #cj4h cu4 cm41     
which was an increase of #cf per cent   
over that of the old brass cylinder     
engines1 which had previously been used 
on ,no4 #d4 ,on ,april #bh1 under a     
pressure of #gj pounds1 these engines   
drove the two #fj cm4 propellers at a   
rate of #ijj ,r4 ,p4 ,m41 and lifted on 
the pendulum nearly #dj per cent of the 
total flying weight of ,aerodrome ,no4  
#d1 which was now approximately #e      
kilos4 ,a trial was made at ,quantico in

 the latter part of ,may1 which is      
described in ,chapter ,,ix4 ,it is only 
necessary to mention in this connection 
that there was a great deal of trouble  
experienced with the alcohol aeolipile1 
the flame being extinguished in the     
moderate wind to which the p#jfg        
aerodrome was subjected while           
preparations for the launch were being  
made4 ,moreover the flame was so nearly 
invisible in the sunlight that it was   
uncertain whether it was burning in the 
critical instants just before the       
launch1 when doubt might be fatal4      
,these conditions resulted in a final   
decision in favor of gasoline1 on       
account of its greater inflammability1  
and in the provision of such hull       
covering that the fires could be lighted
 and maintained in a breeze4  ,in ,june1
 ,i tried a modification of the burner1 
in which the gasoline was delivered     
under the pressure of air to the        
evaporating coil4 ,in the first trial   
steam was raised to a final pressure of 

about #gj pounds1 and a run of #de      
seconds was secured under a pressure of 
#dj pounds in the gasoline tank1 which  
was thought to be altogether too high2  
for1 at the end of the run1 the whole   
apparatus was enveloped in flames1      
because of the gasoline that was        
projected through the burner-tips4      
,continual experiments with different   
forms of burner1 illustrated in ,plate  
#ab1 occupied the time1 with delays and 
imperfect results1 which were trying to 
the investigator1 but are omitted as of 
little interest to the reader4 ,they    
had1 however1 the incidental result of  
proving the practical superiority of    
gasoline over alcohol1 and culminated in
 the evolution of the burner that was   
finally used successfully4 ,it consisted
 of a tank for the gasoline1 from which 
compressed air delivered the liquid to a
 small coil surrounded by asbestos1 in  
which it was vaporized4 ,at the rear end
 of this coil three pipes were led off1 
one of which was a small 8bleeder10     

which fed the burner for heating the    
gasoline1 the other two leading to the  
main burners4 ,after the generation of  
gas in the small coil had been started1 
the heat from the small burner was      
expected to continue the vaporization1  
so that nothing but gas would be able to
 reach the main burners4 ,a device was  
also introduced1 which had greatly      
increased the amount and uniformity of  
the draft and consequently made the     
burners and boilers more efficient than 
before4 ,this consisted simply in       
passing the exhaust steam from the      
engines into the smoke-stack1 and it is 
remarkable that it was not thought of   
earlier4  ,by the middle of ,september1 
#ahid1 both aerodromes were completed   
and ready for another test4 ,on         
,september #bg the condition of         
,aerodrome ,no4 #d was as follows3 ,the 
general type of construction1 namely1   
that of a single midrod1 to which all   
the steam generating apparatus was      
attached1 and which supported also the  

cross-frame and the wings1 was the same 
as in the construction of #ahic4 ,on    
account of the increased weight of the  
model1 and the substitution of an       
inferior piece of tubing in place of the
 former midrod1 it was found necessary  
to stiffen it by the use of temporary   
trusses4 ,permanent bearing points for  
holding the aerodrome securely to the   
newly devised launching apparatus were  
also attached to this midrod4 p#jfh     
,the engines in use at this time were   
the small steel cylinders described     
above1 which were mounted on the        
cross-frame1 and drove the propellers   
directly4 ,these engines were capable of
 delivering to the propellers1 as had   
been proved by repeated tests1 at least 
#j4ff brake horse-power4  ,the boiler   
consisted of two inner coils and an     
enveloping outer coil1 loosely wound and
 connected in series4 ,the inner coils1 
each of which had about #ag turns of #h 
mm4 diameter1 #j4b mm4 thick tubing1    
developed about #hj per cent of the     

steam2 the outer coil of #h turns1 while
 not exactly useless as a steam         
generator1 afforded an efficient means  
of fastening the smoke-stack and cover  
of the boiler1 and for attaching the    
latter to the midrod4 ,this boiler was  
externally #cj cm4 long1 #af cm4 wide1  
and #aj cm4 deep1 weighing with its     
cover approximately #fej grammes4 ,the  
stack for the burnt gases1 into which   
exhaust steam was led from a central    
jet1 was about #a foot long4 ,at best   
this boiler was capable of developing   
slightly over #ajj pounds of steam4     
,the separator was of the form last     
described1 except that the steam dome   
had been moved toward the front1 to     
prevent the jerk of the launching car in
 starting from causing water to be      
pitched over into the engines4 ,it was  
constructed of sheet aluminum-bronze1   
and weighed1 together with its pump1    
#ehj grammes4 ,the pump1 which was      
double-acting and fitted with ball      
valves1 was capable of discharging #d4e 

grammes of cold water per stroke1 its   
efficiency being only about one-half as 
great with hot water4  ,the gasoline    
burner1 which had been finally adopted  
in place of the alcohol aeolipiles1 had 
now been perfected to the form in which 
it was finally used4 ,two ,bunsen       
burners of special construction were    
provided with gasoline gas by the heat  
of an intermediate accessory burner1    
which played upon a coil to which all   
three burners were connected4 ,gasoline 
was furnished from a tank made of       
aluminum-bronze1 under an air pressure  
of about #bj pounds1 the fluid being    
under the control of a screw stop-cock4 
,this tank1 which was capable of holding
 #ajj to #aej cu4 cm4 of gasoline1      
weighed #ahj grammes1 and the burners   
with an outer sheathing weighed #cjb    
grammes4  ,it was calculated that about 
#ccjj cu4 cm4 7#bja cu4 in47 of air     
space would be required to float the    
aerodrome in water1 and this was        
supplied by an air chamber1 having a    

capacity of #bgjj cu4 cm4 7#afe cu4     
in471 which could be shifted to adjust  
the longitudinal equilibrium of the     
aerodrome1 and about #ijj cu4 cm4 7#ee  
cu4 in47 of space in the gasoline tank  
and the midrod4 ,the reel and float1    
which served to indicate the location of
 the aerodrome1 if for any reason it    
should be submerged1 were in one piece1 
and so moored that there was no danger  
of fouling the propellers4  ,the total  
weight of the aerodrome was about #f    
kilogrammes 7#ac4b lbs471 or1 with a    
maximum quantity of fuel 7#hej cu4 cm4  
of water1 #aej cu4 cm4 of gasoline71    
p#jfi less than #g kilogrammes4 ,from   
#fj to #ij pounds of steam could be     
maintained by the boilers for about #b  
minutes1 at which pressure the engines  
developed about #j4ff brake horse-power1
 driving the #gj cm41 #a4be pitch-ratio 
propellers at #gjj ,r4 ,p4 ,m41 and     
giving a lift of from #b4f to #c4j kilos
 7#e4g to #f4f pounds71 or about #dj per
 cent of the flying weight4  ,the wings 

and tail had a total surface of #b4fb   
sq4 m4 7#bh4b sq4 ft471 giving a ratio  
of #b4g kilos to #a sq4 m4 of wing      
surface 7#a4h sq4 ft4 per pound74 ,if   
the hull resistance be neglected1 the   
soaring speed of this aerodrome was     
about #e4i metres 7#ai feet7 per second1
 or #ac miles per hour4  ,turning now to
 the completed ,no4 #e1 its frame was of
 the 8double midrod0 type described     
above1 the two tubes which formed the   
frame being prolonged at the front and  
rear to afford points of attachment for 
the wings and tail4 ,the range through  
which the wings could be shifted to     
adjust the position of the center of    
pressure was1 however1 very small4 ,the 
hull1 which1 it will be remembered1     
contained all the power generating      
apparatus1 was much stronger and heavier
 than that of ,no4 #d1 and resembled    
somewhat the hull of a ship4 ,it had a  
frame-work of steel tubing brazed to the
 midrod1 to which an outer sheathing of 
sheet aluminum #j4c mm4 thick was       

attached4 ,it was1 however1 excessively 
heavy1 weighing nearly #hjj grammes4    
,the engine1 which was mounted near the 
front of the hull1 was the single       
cylinder1 one horse-power engine1       
described above1 which drove the two    
propellers by suitable gearing4 ,the    
remaining parts of the power plant were 
identical with those already described  
in connection with ,no4 #d1 but the more
 advantageous location of them in ,no4  
#e rendered them somewhat more          
efficient4  ,it had been planned to use 
#hj cm4 propellers of #a4be pitch-ratio 
on ,no4 #e1 but it was found in the shop
 tests of the aerodrome that the        
cross-frame was not strong enough to    
withstand the strains1 and that the     
engine could be made to work much more  
steadily with a smaller propeller4      
,accordingly1 propellers of #gj cm4     
diameter and #a4be pitch-ratio1 similar 
to those used on ,no4 #d1 were finally  
substituted4  ,for floating the         
aerodrome1 when it descended into the   

water1 an air-chamber similar to that of
 ,no4 #d1 but of a larger capacity was  
provided4 ,with this in place on the    
aerodrome1 it was calculated that1 if   
all the parts except this float and the 
gasoline tank were filled with water1   
there would still be a buoyancy of over 
#b kilogrammes4  ,the total weight of   
,no4 #e was #hbjj grammes1 or with its  
full supply of fuel and water #ibjj     
grammes4 ,in this aerodrome the same    
boilers used in ,no4 #d were capable of 
maintaining for at least a minute #aae  
pounds of steam1 so that the engine now 
gave the maximum of one brake           
horse-power for which it was designed1  
and1 driving the #gj cm4 propellers1    
lifted repeatedly nearly #de per cent of
 the flying weight4 p#jgj  ,the wings   
and tail constructed for ,no4 #e were   
identical with those of ,no4 #d1 being  
slightly curved and containing #b4fb sq4
 m4 7#bh4b sq4 ft471 equivalent to #a4d 
sq4 ft4 to the pound1 which with the    
flimsy construction of the wings gave an

 entirely inadequate support to the     
aerodrome4  ,during the summer a        
launching apparatus of a new and        
improved type1 which is described in    
,chapter ,x1 had been perfected1 and    
with it repeated tests were made of both
 aerodromes in ,october1 ,november1 and 
,december1 with the unsatisfactory      
results recorded in ,chapter ,,ix4 ,in  
the course of these experiments1 many   
slight modifications of the burners and 
boilers were made1 but no important     
changes were introduced except that the 
cross-frame of ,no4 #e was enlarged and 
strengthened so as to admit of its      
carrying one metre propellers safely4   
,the results1 however1 which were       
obtained1 did not compensate for the    
increased weight of the larger frame4   
,viewing the work of this year from the 
standpoint of results obtained in the   
numerous attempts at flight1 it would   
seem that very little progress had been 
made1 and that there was small reason to
 expect to achieve final success4       

,however1 if the work be examined more  
particularly1 it will be seen that two  
of the most difficult problems had been 
solved1 one completely as far as the    
models were concerned1 and the other to 
a very satisfactory degree4 ,first1 a   
launching apparatus1 with which it was  
possible to give the aerodrome any      
desired initial velocity1 had been      
devised1 and so far perfected that no   
trouble was ever experienced with it in 
testing the models4 ,second1 as a result
 of the extended and systematic series  
of experiments1 which had been conducted
 under the direction of ,dr4 ,barus1 a  
steam pressure of #aae pounds could be  
maintained steadily in the boilers for  
at least a minute1 and the burners could
 be kept lighted even in a considerable 
breeze4  ,a summary of these            
experiments1 together with some account 
of the difficulties encountered and the 
results finally obtained with the       
apparatus in use at the end of the year1
 is given in the following report1 which

 was prepared by ,dr4 ,barus in         
,december1 #ahid4   8,if water be       
sprayed upon a surface kept in a        
permanent state of  ignition1 any       
quantity of steam might be generated per
 time unit4  ,similarly advantageous    
conditions would be given if threads of 
water could be passed through a flame4  
,in practice this method  would         
encounter two serious difficulties1 the 
importance of which  is accentuated when
 the boiler apparatus is to be kept     
within the  degree of lightness         
essential in aerodromics4 ,these        
difficulties are  7#a7 the danger of    
chilling the flame below the point of   
ignition  or of combustion of the gases1
 and 7#b7 the practical impossibility   
of maintaining threads of water in the  
flame4 ,for it is clear  that the       
threads must be joined in multiple arc1 
so as to allow a  large bulk of water to
 circulate through the boiler1 whereas  
even  when there are but two independent
 passages for the water through  the    

furnace1 it is hard to keep both        
supplied with liquid without  unduly    
straining the pump4 ,if the water be    
even slightly deficient1  circumstances 
will arise in which one of p#jga the    
passages  is better than the other4     
,this conduit will then generate more   
steam and drive the water under force   
through the other passage1  increasing  
the temperature discrepancy between     
them4 ,eventually  the hot passage      
reaches ignition and either bursts or   
melts4 ,this  is what sooner or later   
takes place in boilers adapted for      
flying  machines and consisting of tubes
 joined in multiple arc1 when a  single 
moderately strong circulating pump      
supplies the system4   8,to avoid these 
annoyances1 i4 e41 to increase the      
length of life  of the boiler1 the      
boiler tubes are joined in series to the
 effect  that a single current of water 
may flow successively through all of    
them4 ,it is needful therefore to select
 wide tubes1 such as will  admit of an  

easy circulation in consideration of the
 length of  tubing employed without     
straining the pump and at the same time 
to  allow sufficient room for the efflux
 of steam4 ,other considerations  enter 
here1 the bearing of which will be seen 
presently3 if the  tube be too wide the 
difficulty of coiling it on a mandrel of
  small diameter is increased1 while at 
the same time the tube loses  strength  
7ct4 par47 in virtue of the increased   
width4  ,illustration3 ,,fig4 #aa4      
,diagram #a4 ,diagram #b4   8,it is from
 considerations such as these that1 in  
the course of many  experiments1 copper 
tubing about #h mm4 in diameter has been
 adopted4  ,copper is selected because  
of its freedom from internal corrosion1 
easy coiling1 and because of its        
availability in the market4 ,the        
thinnest tube to be had 7walls only #j4a
 mm4 thick7 will withstand  more        
pressure than can be entrusted to the   
larger steam receivers  in circuit with 
the boiler4 ,the boiler weight is thus a

 negligible  factor1 and it is quite    
feasible to reduce the thickness of     
boiler  tubing1 by the superficial      
application of moderately strong nitric 
acid1 to #bjj-djj grammes per           
horse-power of steam supplied4 ,external
  corrosion due to flames occurs only in
 case of deficient water1 and  if the   
boiler be made of tubing with the walls 
#j4b mm4 thick1 it is  in view of the   
possibility of such accidents4 ,boilers 
may then be  tested to #be atm4 without 
endangering the metal4   8,boilers are  
wound or coiled with regard to the two  
points above  suggested1 viz43 to avoid 
chilling the flame the successive turns 
are spaced on all sides1 and to bring   
the water as nearly into the  flame as  
possible1 the diameter of the coils is  
chosen as small  as expedient4 ,further 
reasons for this will presently be      
adduced4  ,the type of boiler eventually
 adopted is shown in the accompanying   
diagrams1 #a and #b1 ,fig4 #aa4         
8,diagram #a1 is a perspective diagram  

showing the plan of winding  and        
,diagram #b1 an end view4 ,the          
circulation is indicated4 ,there are    
two inner coils p#jgb each containing   
about #ag turns1 wound on a  mandrel #e 
cm4 in diameter4 ,the turns are spaced  
so as to allow about  #a cm4 clear      
between successive turns4 ,the outer    
coil envelopes both1  and in this there 
are about #c cm4 between successive     
turns1 and #h  turns in all4 ,length1   
say1 #cj cm41 breadth #af cm41 thickness
 #aj cm41  give the external dimensions 
of the boiler4 ,the shell space between 
outer and inner layers of tubing must   
nowhere be less than #a cm4  ,when so   
wound1 the inner coils 7here as in other
 boiler forms7 raise  about #hj per cent
 or more of the steam2 the outer or     
enveloping  coil1 while not quite       
useless1 make the most effective frame  
work  for the boiler jacket which has   
been devised4 ,the coils are brazed     
together by blind tubes1 as shown in    
,diagram #b1 to keep the whole in       

shape4 ,weight with couplings and cover 
when complete #ece grammes4   8,the     
cover is preferably of mica1 through    
which the flame within  the boiler may  
be seen1 and in which lightness1        
nonconduction1 and  resistance to the   
disintegrating effects of high          
temperature are  met with in a          
pronounced degree4 ,this jacket is held 
down by copper  bands and the end band  
is continuous with the long smoke-stack1
 as  will be presently shown4   8,the   
wide form of boiler with two coils      
within the envelope is not  absolutely  
essential4 ,the same amount of steam can
 be generated from  one coil in an      
envelope in other respects equal to     
,diagram #a if a  sufficiently hot flame
 be passed axially through the coils4   
,such a  flame1 however1 is unstable1   
and for this reason two milder flames   
with a good air access are to be        
preferred on practical grounds even  if 
the weight is thereby increased4   8,to 
further understand the boiler           

construction it is advisable  to        
consider the action of the flame4       
,inasmuch as wide tubes must  be used1  
the problem of evaporating water as fast
 as possible  is equivalent to getting  
heat into the current 7water and steam  
circulating through the coils7 as fast  
as possible from without4  ,if1         
therefore1 t is the mean temperature of 
the fluids within the  coils1 and ,t the
 effective temperature surrounding the  
tube1 then  the rate at which heat will 
flow into the tubes is proportional to  
,tt4 ,now t the temperature of the steam
 is nearly constant  7#ajj-aej7 whereas 
,t the effective flame temperature may  
vary  from #hjj to1 say1 #afjj4 ,it is  
for this reason that the heat  sponged  
up by the boiler depends almost directly
 on the flame  temperature4   8,what    
conditions1 therefore1 will make the    
flame effectively hot8   87#a7 ,the     
coils must obviously be brought as      
nearly into the flame as  feasible3 for 
this purpose the cylindrical helix is   

better than any  other form4 ,but       
87#b7 ,the turns and coils must not be  
so crowded together as to chill  the    
flame into imperfect combustion in      
various parts of its extent4  ,hence the
 loose form of winding4 ,again   87#c7  
,there must be oxygen enough to allow   
complete combustion1 and   87#d7 ,the   
flame itself must be hot and the        
radiation checked by good  jacketing4   
8,to take up the last points3 the       
effective heat of the flame depends  not
 only on the combustion heat of the fuel
 used2 it depends also1  among other    
things1 on the speed with which this    
combustion takes  place4 ,a flame       
burning from a low pressure of alcohol  
gas will be at  low temperature as      
compared with a flame burning from high 
pressures  of the gas4 ,if the flame be 
burnt from a ,bunsen burner in the usual
  way it is an interesting question to  
know how flame temperature  will vary   
with gas pressure4 ,at present we know  
it merely in steam  pressures incidently

 produced in a given engine 7,no4 #d7 as
 for  instance3   ,flame pressure1 #aj  
lbs41 #bj lbs41 #cj lbs4    ,steam      
pressure1 #dj lbs41 #hj lbs41 #abj lbs4 
in the running engine4                  
8,unfortunately there is a limit set to 
this process of increasing  the steam   
supply1 quite aside from conditions     
inherent in the  method4 ,this is due to
 the fact that a certain speed of efflux
  cannot be exceeded without putting the
 flame out4 ,suppose1 for  instance1 in 
,fig4 #ab1 that a gas generated from a  
liquid is ignited  at the end of the    
,bunsen burner ,f2 then if the velocity 
of efflux  of mixed gas and air in the  
direction ,,ab from the mouth of ,f     
exceeds the velocity of combustion in   
the direction ,,ba1 the flame  will     
obviously be carried away from the mouth
 of the tube and  dissipated4 ,this     
state of things is actually realized at 
pressures  exceeding about #ae lbs41    
depending on the degree of mixture of   
the combustible gases used1 and         

therefore on apparently haphazard       
conditions connected with the jet1 the  
air holes1 the air supply1  etc4        
,illustration3 ,,fig4 #ab4              
,illustration3 ,,fig4 #ac4   8,if1      
however1 the velocity of the jet at the 
point of efflux be  checked by an       
obstruction like a cylinder ,c1 ,fig4   
#ac1 placed  co-axially with the burner 
tube ,f1 the speed of combustion will no
  longer be exceeded 7supposing ,c      
properly chosen7 and flames will  then  
burn from high-pressure gas4 ,in this   
way flames were maintained  generated   
from alcohol gas at even #dj lbs4 and   
above4  ,illustration3 ,,fig4 #ad4      
8,the gas escaping from the ,bunsen     
burner is never sufficiently  arated to 
burn completely4 ,otherwise there would 
7in general7 be  explosions in the tube 
,f4 ,a part of this air is supplied at  
the  mouth of the boiler ,b1 ,fig4 #ad1 
and the amount available here will      
depend on the velocity of the jet ,f4   
,hence it does not follow  that a       

high-pressure burner like that in ,fig4 
#aa will supply a  proportionate amount 
of heat1 since its jet suction is not   
intense  and the combustion within the  
boiler is incomplete4 ,this difficulty  
may be remedied by placing p#jgd air    
holes in the jacket of the  boiler1     
provided the boiler be wrapped loosely  
enough not to chill  the flame below    
ignition4 ,it is with reference to this 
effect that  the boilers1 ,fig4 #aa1    
were wound4 ,a number of rifts aaa1     
,fig4 #ae1  are then left in the jacket 
through which air may enter in virtue of
  the burner flame acting as a jet at   
the mouth of the boiler4   8,when so    
constructed the flame at first enters   
the inner coil only2  but after a little
 while it suddenly spreads out          
throughout the  whole interior space and
 envelops the coils4 ,this sudden       
expansion  is due1 probably1 to the     
assumption of the spheroidal state by   
the  water within the coils1 the current
 now flaring on an enveloping  cushion  

of steam4 ,the pump must work well1 for 
deficient water means  a hot tube and   
deficient steam1 or eventually a rupture
 of the tube4   8,thus far the          
dependence for draft has been on the    
burner jet and  the suction of the      
smoke-stack in virtue of the inertia of 
the  moving gases4 ,but even with this  
ventilated boiler1 this method is       
limited to certain dimensions of the    
boiler4 ,thus a boiler #hj cm4  long    
yielded about the same quantity of steam
 as a boiler half as  long and otherwise
 similar4 ,only the initial parts of the
 boiler  are1 therefore1 relatively     
efficient1 and the reason of this seems 
to be that1 apart from shape1 etc41 the 
flame as a heat-producing  agent is     
practically defunct1 when a certain     
amount of heat has  been taken out of   
it3 in other words1 even with fair      
ventilation  the flame is eventually    
chilled off by the voluminous products  
of combustion continually accumulating  
in the boiler4 ,the same  choking action

 accompanies the presence of unburnt    
gases4 ,if1 for  instance1 the flame be 
burnt in the air1 it is slender and much
  smaller in volume than in the boiler4 
,the flame is also of small  volume and 
burns completely in a wide boiler1 but  
the steam is  always deficient1 because 
of the distance between flame and coils 
7see above74 ,with the above apparatus  
about #a_/b lb4 of dry steam per  minute
 per square foot of heating surface was 
attained4  ,illustration3 ,,fig4 #ae4   
8,this introduces the final condition   
for rapid steam generation4  ,there must
 be artificial suction at the           
smoke-stack4 ,by passing the  exhaust   
steam in the form of a central jet      
through the smoke-stack  the yield of   
steam was increased #bj to #cj per cent4
 ,in fact as the  supply of gas from the
 burner is given1 the artificial suction
 in  question means more air in the     
boiler for the same amount of gas  and  
it means also a more rapid removal of   
the exhaust gases4 ,the  experiments    

with steam suction are yet to be        
completed1 and with  them the boiler    
question is to be finally laid at rest4 
,the chief  points at issue are these3  
8#a4 ,seeing that the jet suction       
increases with the length of the        
smoke-stack1 up to a certain length at  
least1 how long and how wide  must the  
efficient smoke-stack be made8 ,thus a  
smoke-stack #aj cm4  long is all but    
useless4 ,good results are obtained when
 the stack  measures #cj cm4 in length  
beyond the end of the steam jet4 p#jge  
8#b4 ,what is the relative efficiency of
 the initial and final halves  of the   
length of the boiler8 ,this will show in
 how far it is  useful to increase the  
length of the boiler for a given burner 
and  steam jet4 ,it will also show what 
advantage is to be gained from          
triplicate boilers with three burners1  
as compared with duplicate  boilers with
 two burners1 or single boilers with one
 burner1 when  the same weight of tubing
 is used throughout4   8#c4 ,what is the

 effect of pressure on the aeolipile    
tank1 or in  how far does the steam     
generated depend on what may be called  
the  pressure of the flame8 ,this is    
also an important point which remains   
for quantitative solution4 ,it can be   
approached in two ways3 either  by      
finding the steam evaporated in terms of
 the tank pressure1 or by  finding the  
temperature of the flame pyrometrically4
   8#d4 ,what speed of water circulation
 best conduces to steam  generation8 ,a 
good pump is now installed by which the 
circulation  can be varied4 ,if water   
can be put into the boiler just fast    
enough  to come out dry steam at the    
other end1 the efficiency ought to be  a
 maximum1 but it does not follow that it
 will be so1 for one can  imagine a wet 
circulation sponging up more heat than  
one which is  just dry at the end40     
#ahie  ,during ,january and ,february1  
#ahie1 the experiments with boilers and 
burners were continued and even better  
and more uniform results than those     

given above were obtained4 ,the boilers 
of ,aerodrome ,no4 #e were finally      
brought to such a state of efficiency1  
that under favorable conditions a lift  
of nearly sixty per cent of the flying  
weight was secured4 ,this was much more 
than was required for flight1 but it was
 decided to postpone the trials until   
,no4 #d could also be made ready for a  
test and the frame of ,no4 #e could     
itself be strengthened in many weak     
places4  ,upon examining ,no4 #d1 which 
had been put aside since the trials in  
,december1 it was found to have rusted  
so badly throughout and to be so unfit  
in every way for trial1 that a complete 
reconstruction of the whole would be    
necessary4 ,so many advantages had been 
gained in ,no4 #e by the double midrod  
type of construction that it was decided
 to rebuild ,no4 #d on a modification of
 the same plan1 as shown in ,plate #aa1 
retaining1 however1 the same engines    
which had been used before4  ,in this a 
very guarded return was made to the type

 which had proved so unsatisfactory in  
,no4 #j1 that is1 making the hull       
support rods at the front and rear for  
attaching the wings and tail4 ,in this  
case1 however1 the hull was constructed 
very rigidly1 and the tubes at the front
 and rear were firmly attached and      
braced so that they could withstand a   
considerable strain without undue       
distortion4 ,the work on this frame was 
completed in ,march1 but the other parts
 were not in entirely efficient         
condition even in ,may1 when the        
aerodromes were taken to ,quantico for  
trial4 ,moreover1 it was found that the 
weight of this aerodrome had increased  
far beyond the original estimates4 p#jgf
  ,in view of the disasters from trials 
in the field1 due to inability to obtain
 automatic equilibrium in flight and to 
the flexure of the large wings rather   
than to defects of the engines1 the     
conditions at this time1 after three    
years of failure1 seemed so nearly      
hopeless1 that without abandoning the   

work on these steam aerodromes1 ,i again
 had recourse to the early plan of      
constructing smaller models driven by   
,india rubber1 in which the small wings 
employed could be made of the requisite 
stiffness4 ,instead of employing twisted
 rubber1 however1 the defects of which  
had been amply proved in previous       
trials1 these new constructions were    
meant to employ rubber directly         
stretched and pulling4 ,in this         
condition the rubber exercises nearly   
six times the power in proportion to    
weight that it does when twisted1 but on
 the other hand it requires a very      
strong frame and subordinate parts4  ,i 
spent an inordinate amount of time and  
labor during this year in attempting to 
employ this latter form of construction 
and finally got a few useful results    
from it1 but none in proportion to the  
labor expended4  ,during ,march1        
,aerodrome ,no4 #e1 the frame of which  
had proved on test to be radically weak1
 was completely refinished except for   

the wings4 ,the propellers had hitherto 
been made of wood1 but in ,may1 ,i      
commenced a new construction of steel1  
wood and cloth1 on a plan giving a      
figure which1 though not rigorously     
helicoidal1 was practically near enough 
to the theoretical form and was also    
both lighter and more elastic than the  
wooden construction4  ,on ,may #h and   
,june #g ,aerodrome ,no4 #e was again   
tried at ,quantico1 and although the    
tests were unsuccessful1 in that the    
aerodrome failed to fly1 partly because 
of the fact that so much time was spent 
in raising steam that practically the   
entire supply of fuel and water was     
exhausted before the aerodrome was      
actually launched1 yet it had come so   
much nearer flying than any machine had 
previously done1 that it was felt that  
if either the power could be increased  
or the weight decreased even a slight   
amount1 the aerodrome would probably    
fly4 ,in view of the great care that had
 been exercised in keeping down the     

weight1 it seemed almost hopeless to    
attempt to reduce it1 and it also seemed
 equally hopeless to attempt to get more
 power without increasing the weight4   
,however1 something had to be done to   
increase the ratio of power to weight1  
and as it was seen that this would      
involve extensive changes in ,no4 #e1 it
 was decided to entirely rebuild ,no4 #d
 with this idea in view1 though it was  
evident that it involved a plan of      
construction even lighter than the      
dangerously light plan on which ,no4 #d 
had already been constructed4  ,during  
,mr4 ,langley's absence in ,europe in   
the summer1 ,aerodrome ,no4 #d was      
entirely reconstructed and made to      
embody many new characteristics1 the    
changes introduced being so radical that
 this model was henceforth designated as
 8,new ,no4 #d40 ,the new               
characteristics of this model were its  
unprecedentedly p#jgg light frame and   
the elevation of the transverse frame   
#ab centimeters above the midrod1       

whereby the position of the line of     
thrust was raised so that it was #bj    
centimetres from the center of pressure1
 which from theory seemed to be very    
nearly its correct position4 ,the total 
flying weight was but #fdjj grammes 7#ad
 pounds71 with a total supporting       
surface of fifty-four square feet1      
equivalent to very nearly four square   
feet per pound4 ,it was hoped that with 
this extremely light construction the   
8dead lift0 would amount to a large     
percentage of the flying weight1 and as 
much as sixty per cent was actually     
lifted on the pendulum4 ,as1 however1   
the aerodrome approached completion it  
became more and more evident that the   
construction was hopelessly fragile1 the
 frame being scarcely able to support   
itself in the shop4 ,by ,november this  
conclusion became certain1 and this     
aerodrome 7,new ,no4 #d7 was never put  
to an actual test in the field4 ,the    
very expensive set of wings covered with
 gold beater's skin1 which were also    

constructed at this time for this model1
 proved so weak under test that they    
were entirely abandoned4  ,when ,mr4    
,langley returned to ,washington in the 
fall1 many important points1 which had  
been under special consideration during 
the past year1 particularly those       
relating to the disposition of          
sustaining surfaces1 and the provision  
of automatic equilibrium1 were still not
 definitely determined4 ,it was not yet 
decided whether two sets of wings of    
equal area should be used for the       
aerodrome1 or what the efficiency per   
unit of area of the following surfaces  
was in comparison with the leading      
surfaces4 ,to aid in determining these  
and other important points concerning   
the relative position of the center of  
gravity and the center of pressure in   
the horizontal planes1 he had several   
small gliding models made1 which could  
be used with either one or two pairs of 
wings1 and afforded an opportunity for  
testing and comparing several types of  

curved surfaces4  ,these models were    
built so that the center of gravity     
could be adjusted to any desired point1 
and had in addition1 as a means of      
assisting in preserving equilibrium1 a  
small tail-rudder1 shaped somewhat like 
a child's dart1 which was intended to   
support no part of the weight4  ,the    
tests with these models were very       
satisfactory and aided greatly in the   
final development of what is known as   
the 8,langley type40 ,indeed1 in the    
single month of ,november all the       
points1 which had hitherto been more or 
less indefinite1 were finally decided   
upon1 and the tests of the following    
spring proved these decisions correct4  
,two sets of wings of equal area were   
hereafter provided for every aerodrome1 
which not only greatly increased the    
stability1 but also overcame the        
difficulty hitherto experienced in      
bringing the ,,cp over the ,,cg4 ,the   
tail-rudder1 formed of planes           
intersecting at right angles1 was       

adopted as the means of control4 ,in use
 on the aerodromes it was set at a      
negative angle1 and given a certain     
p#jgh degree of elasticity1 which was at
 first provided in the frame of the     
rudder1 but was later given by a flat   
wooden spring1 by which it was attached 
to the aerodrome4 ,the tail in this form
 now became the sole means of           
controlling the equilibrium1 and the    
results obtained with it were so very   
satisfactory that no further attention  
was given either to the gyroscopic      
control built during the previous       
summer1 or to any of the electrical     
forms of control constructed prior to   
that time1 all of which involved more or
 less delicate apparatus4  ,the definite
 form into which these ideas            
crystallized is perhaps best exemplified
 in the letter of instructions issued by
 ,mr4 ,langley on ,november #cj1 #ahie  
to the men employed on the work4 ,the   
text of this letter is given in the     
,appendix1 and the forms referred to in 

it for recording the weights and        
adjustments of the aerodromes are those 
used in the data sheets after this time4
  ,in ,october work was resumed on      
,aerodrome ,no4 #e1 on which nothing had
 been done since its test on ,june #g4  
,the reconstruction of 8,old ,no4 #d0   
into 8,new ,no4 #d0 which had occupied  
the entire summer1 and the final result 
of which was the production of a machine
 so radically weak as to be useless1 had
 been so discouraging that it seemed    
vain to attempt in any way to decrease  
the weight of ,no4 #e4 ,the addition of 
the rear wings in place of the tail had1
 however1 so greatly increased the      
supporting surface that it seemed       
possible that ,no4 #e might now be able 
to fly with no greater engine power than
 it had on ,june #g4 ,some weak places  
in its frame were1 therefore1           
strengthened and the midrod at the front
 was raised five centimetres in order to
 raise the center of pressure farther   
above the center of gravity and give the

 front wings a greater range of         
adjustment4 ,some slight changes were   
also made in the gearing which drove the
 pump1 so as to make it work faster1 and
 new burners1 boilers and a gasoline    
tank were constructed during ,november4 
,later the midrod1 which had formerly   
consisted of two separate pieces        
attached at the front and rear          
respectively of the main frame1 was made
 continuous1 and in order to avoid      
passing it through the smoke-stack1 the 
stack was made to fork at this point4   
,these changes are clearly shown in     
,plates #ad and #ae1 which are          
photographs taken on ,december #c4 ,this
 plan was1 however1 soon changed so that
 the midrod passed through the          
smoke-stack and was rigidly attached to 
the frame at several points1 and a new  
pump and new boilers were substituted   
for those which had been worn out4      
,aside from these changes1 which        
although small1 added very materially to
 the general strength of the frame1 no  

important changes were made in ,no4 #e  
prior to its remarkable flight of ,may  
#f1 #ahif4  ,illustration3 ,,pl4 #ad    
,,aerodrome ,,no4 #e1 ,,december #c1    
#ahie4 ,,plan ,,view4 ,,rudder ,,removed
  ,illustration3 ,,pl4 #ae  ,,aerodrome 
,,no4 #e1 ,,december #c1 #ahie4 ,,side  
,,view  ,while these changes were being 
made in ,no4 #e1 similar ones were also 
being carried out in ,new ,no4 #d1 and  
the addition of the rear wings to ,no4  
#d1 together with other slight changes1 
made it such a distinctively different  
machine from what it had been1 that it  
was now designated as ,no4 #f4 ,after   
making extensive p#jgi repairs to the   
extremely light frame of ,no4 #f        
7formerly ,new ,no4 #d7 it was thought  
to be in suitable condition for flight  
and was accordingly boxed preparatory to
 sending it to ,quantico4  ,the year1   
therefore1 closed with ,no4 #f          
apparently in condition for test1 but it
 was decided not to take it to ,quantico
 until ,no4 #e1 which was still         

undergoing repairs1 could also be got   
ready4    #ahif  ,a few days after the  
beginning of the new year1 while the    
repairs on ,no4 #e were being completed1
 it was decided that the frame of ,no4  
#f which had been boxed ready to be     
carried into the field for trial1 was so
 weak that before putting it to an      
actual test in flight it would be best  
to make some tests on the strength of   
its frame4 ,while testing the frame for 
torsional strength1 it broke under the  
moderate test of a weight of #ejj       
grammes placed at the tips of the wings1
 the angle of deflection just prior to  
its breaking being #ce1 while the frame 
of ,old ,no4 #d in ,march1 #ahie1 had   
shown a deflection of only #aj4e under a
 similar test4 ,this breaking of the    
frame showed very plainly that the worst
 fears in regard to it had been realized
 and that by some means or other the    
frame must be strengthened4 ,this was   
finally accomplished by making the      
midrod continuous through the           

smoke-stack as had already been done in 
,no4 #e1 and at the same time an        
additional improvement was made in the  
means of attaching the ,pnaud tail1     
whereby it was lowered in order to give 
it a greater clearance in passing under 
the launching car in actual test4 ,later
 the boilers proved defective and new   
ones were substituted1 but except for   
some minute details no further changes  
were made in ,aerodrome ,no4 #f prior to
 its test in ,may4  ,on ,may #f1 ,no4 #f
 was unsuccessfully tried at ,quantico  
just prior to the very successful test  
of ,no4 #e4 ,in this test no serious    
damage was done to the frame1 but before
 going to ,europe in the summer1 ,mr4   
,langley ordered that both aerodromes be
 completely overhauled and put in       
condition for further experiments in the
 fall4 ,in this remodelling practically 
no changes were introduced in the frame 
of either ,no4 #e or ,no4 #f1 but the   
engines of ,no4 #f were refitted and a  
new boiler was substituted1 which1 with 

slight improvements in the burner1      
resulted in a somewhat increased power  
in the engines4  ,a complete            
description1 giving all essential       
details of both ,aerodromes ,nos4 #e and
 #f1 will be found in ,chapter ,x4      
p#jhj    ,,chapter ,,viii  ,,history    
,,of ,,construction ,,of ,,sustaining   
,,and ,,guiding ,,surfaces  ,,of        
,,aerodromes #d1 #e ,,and #f            
,,introduction  ,in some early          
experiments in #ahhg with the small     
models without motor power1 which have  
not been particularly described1 two    
pairs of wings1 in the same plane1 were 
employed for reasons connected with     
stability4 ,afterward1 in many of the   
rubber-driven motor models1 which have  
been described in ,chapter ,,ii1 two    
large front wings were employed and the 
following pair were diminished into what
 may properly be called a tail4 ,this   
plan was a retrogression in design1 and 
it was pursued by the writer with a     
pertinacity which was not justified by  

the results obtained1 being used even on
 the early rubber-driven models4  ,in   
this construction1 it will be observed  
that the flat tail was in fact not only 
a guiding but a sustaining surface1     
since it bore its own share of the      
weight4 ,it was not until a much later  
date 7,november1 #ahie7 that the writer 
returned to his earlier construction of 
two pairs of wings in the same plane    
bearing the whole weight of the         
aerodrome1 to which was now added a flat
 tail1 whose function was not to        
support1 but wholly to guide4 ,this was 
developed into the final construction by
 the addition of a vertical rudder or   
rudders4  ,the present chapter is not   
concerned with the history of the       
earlier attempts with small models1 or  
of those numerous constructions of      
sustaining surfaces which were never put
 to actual trial2 nor does it give any  
description of the experiments which    
were made in placing one set of surfaces
 over the other1 according to a method  

suggested in 8,experiments in           
,aerodynamics40#bg  ,the experiments in 
8,aerodynamics10 and the theoretical    
considerations given in ,chapter ,v on  
sustaining surfaces1 would never alone  
have led to the construction which was  
finally reached1 which was largely due  
to the hard lessons taught by incessant 
accident and failure in the field4 ,the 
present chapter1 therefore1 should be   
read in connection not only with the    
pages of 8,aerodynamics10 but with      
,chapters ,v and ,,ix of this book4     
,illustration3 ,,pl4 #af  ,,early       
,,types ,,of ,,wings ,,and ,,systems    
,,of ,,guying  ,it is to be remembered  
that1 while the center of gravity of the
 aerodrome could be determined readily  
and exactly1 the center of pressure     
could be determined only approximately  
in advance of trial in actual flight4   
,the positions p#jha of the supporting  
surfaces given in this chapter are1     
then1 approximations made from rules for
 8balancing10 i4 e41 for obtaining      

equilibrium in actual flight1 rules     
which are in fact tentative1 since they 
are founded on a priori considerations  
with partial correction from the        
empirical knowledge gained by previous  
field trials4 ,for these rules see      
,chapter ,,vi4    #ahic  ,with reference
 to the supporting and guiding surfaces 
of ,aerodromes ,nos4 #d1 #e1 and #f1    
,aerodrome ,no4 #d1 in its earliest     
condition mentioned in the preceding    
chapter1 was taken into the field1 but  
never brought to trial in the air4 ,it  
is sufficient to say that in the largest
 of the three sets of wings constructed1
 each wing was #agea inches1 and        
therefore contained about six square    
feet1 so that with the tail 7which was  
at this time a supporting surface71     
whose area was one-half that of the two 
wings1 the total supporting surface was 
#ah square feet1 or since the flying    
weight was #i4a pounds1 the proportion  
of surface to weight was somewhat less  
than #b square feet to the pound4 ,the  

wings were at this time ribless1 it     
being expected that the silk cover which
 was purposely left loose would take its
 curve from the air filling it1 which   
subsequent experience has shown would   
have led to certain disaster if the     
aerodrome had been launched4 ,it may be 
added that there was a vertical rudder  
of what is now seen to have been a      
wholly inadequate size4 ,these remarks  
may be applied with little modification 
to the attempted flight with ,no4 #d on 
,may #be1 except that the vertical      
rudder had been made larger1 but was    
still much too small4    #ahid  ,from   
the account of the field trials to be   
given in ,chapter ,,ix1 it will be seen 
that in numerous attempts at flight     
prior to ,october #f1 #ahid1 the cause  
of failure can in every instance be     
traced to imperfections more fundamental
 than those of the sustaining surfaces1 
either the launching device or some     
other part failing to work              
satisfactorily4 ,i therefore commence a 

description of the sustaining surfaces  
with those of ,nos4 #d and #e as used on
 that day4  ,the construction of the    
wings of ,no4 #d and ,no4 #e1 which were
 nearly identical1 is shown in ,fig4 ,a 
,plate #af4 ,a rod of hickory1 tapering 
from #a_/b inch in diameter at the      
larger end to #a_/d inch at the smaller1
 was steamed and bent1 as shown in the  
drawing1 to form the main front rib of  
the wing4 ,this was firmly clamped to   
the midrod1 and to the rib in turn were 
attached a number of cross-ribs of      
hickory1 slightly curved1 the inner one 
of which was fastened to the hull at its
 inner extremity1 while the whole was   
covered with silk4 ,the length of each  
wing was #afb cm4 7#fc4ge inches71 and  
the width #ed cm4 7#ba4be inches74 ,the 
tail was plane and equal in area to one 
of the wings1 so that the joint area of 
the wings and tail was #b4fb square     
metres 7#bh4b sq4 ft474 p#jhb  ,each    
wing was attached to the midrod by a    
single clamp1 different forms of which  

are shown at ,f1 ,g1 ,h1 ,i 7,fig4 #af74
 ,the clamp consisted of two short split
 tubes1 into which the main front ribs  
were securely clamped by means of       
screws4 ,they were set at an angle and  
united to a grooved frame1 by which the 
wings could be readily attached to a    
second piece clamped about the midrod4  
,the tail clamp1 like the wing clamp1   
was composed of two pieces1 sliding one 
upon the other1 but as the tail formed a
 single surface1 one part was           
permanently attached to it4 ,clamps ,f1 
,g were fitted to aerodrome ,no4 #d1 and
 ,h1 ,i to ,no4 #e4 ,the wings were set 
at a diedral angle of about #aej1 but as
 they were not guyed in any way1 this   
angle in flight and under the upward    
pressure of the air probably became much
 less4 ,the tail was plane but ribbed   
like the wings4  ,illustration3 ,,fig4  
#af4 ,wing clamps1 #ahib-ahif4  ,in     
preparing the machine for flight1 the   
wings and tail of ,no4 #d were set at a 
very small root angle with the midrod1  

perhaps not exceeding #c1 but while this
 angle might be maintained at the firmly
 held root of the wing1 it was later    
seen to be probable that the extremity  
of the wing was flexed by the upward    
pressure of the air after launching1    
though the full extent and evil effect  
of this flexure was not recognized at   
the time4 ,in the approximative         
calculations for 8balance10 made at this
 time1 the tail was treated as bearing  
#a_/c of the weight of the aerodrome1 as
 it was #a_/c of the supporting area1   
for though it was recognized that its   
position in the 8lee0 of the wings      
rendered it less efficient1 the degree  
of this diminution of efficiency was not
 realized4 ,a vertical rudder #bj cm4#gj
 cm4 7#h in4#bh in471 with an area of   
#j4ad metres 7#a4e sq4 ft47 was used4   
p#jhc  ,the particulars of the launch   
will be found in ,chapter ,,ix4 ,in the 
present connection1 it is sufficient to 
say that though launched with the       
requisite velocity and without accident1

 it fell into the water at a distance of
 about #ae metres 7#di feet7 with the   
midrod nearly horizontal1 the combined  
effect of engines and initial impulse   
having in fact kept it in the air for   
less than two seconds4 ,the true cause  
of this failure not then being          
recognized1 it was attributed to the    
angle of the wings with the midrod      
having been too small4  ,the launch of  
,no4 #e followed almost immediately1 but
 taking warning by the supposed cause of
 failure of ,no4 #d1 its wings were set 
at a root angle of #bj1 and a hurried   
adjustment was made to secure greater   
rigidity1 the tip being partly secured  
against twisting by a light cross-piece1
 and guyed so that the wing as a whole  
was not only at a greater angle1 but    
stiffer than in the case of ,no4 #d4    
,these changes it was hoped would cause 
the aerodrome to advance at a           
considerable initial angle with the     
horizontal1 and it did so1 for instantly
 after the launch1 as the aerodrome     

escaped from its bonds into free air1   
the inclination of the midrod increased 
until it stood at about #fj1 when the   
machine1 after struggling a moment to   
maintain itself1 slid backward into the 
water 7with its engines working at full 
speed7 after advancing about #ab metres 
7#ci feet71 and remaining in the air    
about #c seconds4  ,on the whole1 the   
result of the first actual trial of an  
aerodrome in the field was              
disconcerting1 for unless the result was
 due to the wings being placed in a     
position wholly unfavorable to support1 
there seemed to be no doubt that either 
the engine power or the supporting      
surface was insufficient4 ,now this     
engine power was by computation between 
three and four times what was necessary 
to support the aerodrome in horizontal  
flight at an angle of #bj1 and after    
making every allowance for slip1 there  
should have been still an excess of     
power for the first flight of ,no4 #d1  
whereas actual trial indicated that it  

was insufficient4 ,but on the other     
hand1 the experiment with ,no4 #e1 which
 momentarily held its position in the   
air at an angle of #fj1 seemed to       
indicate that the engine power was      
abundant1 and that the failure must be  
traced to some other cause4  ,as a      
result of these experiments it was      
concluded1 8that it is an all-important 
thing that the angle of the front wing  
shall be correct1 and that this cannot  
be calculated unless it is known how    
much the tip will turn up under pressure
 of the weight40 ,i felt1 then1 that ,i 
had learned something from the failures 
as to the need of greater rigidity of   
the wings1 though how to obtain this    
without adding to their weight was a    
trying problem4 ,it was thus at an early
 stage suspected that the evil to be    
guarded against in wing construction was
 the distortion of the form of the wing 
under pressure1 chiefly by torsion1     
which is specially hard to provide      
against without a construction which is 

p#jhd necessarily heavy4 ,this suspicion
 was a correct one1 though the full     
extent of the evil was not yet surmised4
  ,in the light of subsequent experiment
 it may now be confidently stated that  
the trouble was with the wings1 which at
 the moment after launching were flexed 
wholly out of the shape which they were 
designed to have1 and which they        
retained up to that critical moment4    
,after returning to ,washington1 one of 
the wings was inverted1 and a quantity  
of sand1 equal in weight to the pressure
 upon the wing in flight1 was added1    
under which the yielding at the tip     
amounted to #fe1 or from #bj to #de1    
showing that the wings were entirely too
 weak to sustain the aerodrome4  ,in    
speaking of the efforts to strengthen   
the wings1 it must be constantly        
remembered that this could hardly be    
done in any way which did not involve   
increased weight2 that is1 it could     
hardly be done at all1 since increased  
weight was forbidden4  ,the first       

attempt at systematic guying was made on
 ,october #bg4 ,as shown in ,fig4 ,b1   
,plate #af1 two guy-posts extending     
beneath the midrod were connected by    
guy-wires with the outer extremities of 
the wing1 by means of which it was      
sought to hold the wing in place and    
prevent its extremity from twisting     
upward1 while a third wire connecting   
with the bowsprit prevented its moving  
backward4 ,in addition1 two aluminum    
wires1 stretched across above from wing 
to wing1 kept the lower guys tight4  ,on
 ,october #bg1 ,aerodrome ,no4 #e1      
equipped with large new wings and tail1 
having a combined area of #c4g square   
metres 7#dj sq4 ft471 the wings being   
each #fd cm4#aib cm4 7#be4be in4#ge4ge  
in471 turned sharply and completely     
round1 apparently through some internal 
current of the main wind against which  
it was advancing4 ,owing to this almost 
instantaneous turn1 it lost headway and 
came down4 ,this led to the subsequent  
construction and use of a much larger   

vertical rudder1 intended to prevent in 
future any such sudden pivoting and     
consequent loss of momentum4 ,the wings 
showed a tendency to 8pocket0#bh and    
bag1 which indicated some serious fault 
in their construction4  ,as a result of 
these experiments1 it was decided on    
,october #bi to attempt to make the     
wings stiffer 7though their weight was  
almost prohibitory71 by inserting more  
cross-pieces1 cross-pinning and guying  
them so as to make them more rigid as a 
whole1 and less liable to pocket4  ,at  
this time an automatic device in the    
form of a sliding tail was designed1    
which it was thought would cause the    
center of pressure to move backward when
 the aerodrome reared1 and forward when 
it plunged downward1 but the device1    
though afterward constructed1 was never 
brought to trial in the field4          
,aerodrome ,no4 #e1 equipped with a new 
set of wings similar to those used p#jhe
 on ,october #bg1 and guyed as in the   
previous experiment1 was again launched 

on ,november #ba1 with the results      
recorded in ,chapter ,,ix4 ,the failure 
was attributed to the twisting of the   
wings under pressure to such an extent  
that not only was their effective area  
greatly reduced1 but the outer portions 
were upturned so as to catch the air    
upon the upper surfaces1 the result     
being in part a downward pressure4  ,on 
the following day a pair of the wings   
was inverted and a weight of sand equal 
to the air pressure to which they were  
subjected in flight1 was distributed    
over their surfaces4 ,under the action  
of this1 the twisting of the wing was   
seen to increase from the root1 which   
was held with comparative rigidity1 up  
to the tip1 where in spite of the       
cross-ribs it amounted to #de4 ,the     
resistance to torsion lay chiefly in the
 front rib1 which1 in addition1 could be
 bent easily1 allowing the surface to   
become distorted with great loss of     
lifting power4  ,the experiments of     
#ahid had demonstrated the urgent       

necessity for greater rigidity in the   
sustaining surfaces1 which might1 as it 
seemed1 be obtained either by increasing
 the strength of the framing 7which     
meant additional weight7 or by resorting
 to some new and untried construction1  
or by a proper system of guying4 ,guying
 seemingly offered the most feasible    
solution of the problem2 but although   
the system of wire guying was thoroughly
 tried1 the result was very             
unsatisfactory1 as the wings continued  
to twist and bag in a way that was      
extremely discouraging4    #ahie  ,i    
accordingly had recourse in #ahie to the
 system of wooden guy-sticks shown in   
,fig4 ,d1 ,plate #af1 which necessarily 
added greatly to the weight of the      
sustaining surfaces4 ,each wing was     
separately strengthened by means of a   
light rod of spruce1 in cross-section   
about the size of the main front rib1   
extending across the upper surface of   
the wing1 at a distance of about        
one-third the width of the wing behind  

the front rib4 ,it was tied to each of  
the cross-ribs and to the outer bent    
portion of the front rib1 and at its    
root was fastened to the frame of the   
aerodrome4  ,this effectually prevented 
the bending of the front rib and the    
consequent bagging of the cover1 and to 
that extent marked a decided advance in 
wing construction4 ,but it was faulty1  
in that1 not being supplemented by wire 
guying1 it offered little resistance to 
the twisting of the wing about the main 
front rib1 the rear tip of the wing     
being free to turn up under pressure1 as
 it had done on former occasions4 ,a    
similar guy-stick was stretched across  
the tail4 ,to guard against torsion1    
rods extending diagonally across the    
wings and tail were used1 which1 with   
the aid of the guy-sticks just          
described1 prevented the surfaces from  
twisting greatly4 ,in addition1 a rod   
joining the front ribs and stretching   
across from wing to wing tended to      
maintain a fixed diedral angle4 p#jhf   

,the wings as thus guyed were rigid     
enough1 and in the field-trials of ,no4 
#e on ,may #h and ,june #f1 did not     
yield noticeably under pressure1 and    
there seemed to be no serious default in
 their lifting power1 but the guy-sticks
 were heavy and the system was not again
 employed4 ,the wings used in these     
trials1 shown in ,fig4 ,c1 ,plate #af1  
had a frame of hickory1 consisting of a 
front rib and nine cross-ribs1 over     
which the silk was tightly stretched4   
,the curvature of the wings1 which is   
shown in the cross-sectional drawing1   
had a rise of about one-twelfth the     
width1 the highest point of curvature   
occurring about one-fourth the distance 
from front to rear4 ,each wing was #fd  
cm4#aib cm4 7#be4be in4#ge4ge in471 the 
two with the tail1 in surface equal to a
 single wing1 having an area of #c4g    
square metres 7#dj sq4 ft474 ,the       
combined weight of the wings was #aaej  
grammes 7#b4ec pounds71 and of the tail1
 #ehc grammes 7#a4bh pounds74  ,the     

evolution of a vertical rudder had      
meanwhile been going steadily forward4  
,those first used had been small1       
rectangular1 stiff1 and heavy1 but in   
the experiments of ,may #h a much       
lighter and larger construction1        
consisting of a frame #ib cm4#gf cm4    
7#cf in4#cj in47 covered with paper1 was
 used1 and on ,june #g this was replaced
 by a long1 diamond-shaped rudder1      
having a spruce frame covered with silk1
 very light and seemingly more effective
 than any hitherto used4  ,i had in the 
meantime designed a 8tail-rudder10      
consisting of a horizontal tail and     
vertical rudder combined1 each having an
 area of about #j4f square metres 7#f4e 
sq4 ft47 which1 however1 was not used   
until #ahif4  ,in ,august was begun the 
construction of a deeply curved and     
arched pair of wings for ,no4 #d1 which 
consisted of a light framing of spruce  
elaborately guyed and covered with      
gold-beater's skin drawn tight as a     
drum-head with pyroxelene varnish4 ,in  

their construction a new feature1       
foreshadowed in the method of guying the
 separate wings used in the field-trials
 of ,may and ,june1 was introduced1     
which was adopted in all subsequent     
constructions--the guy-stick1 previously
 described as stretching lengthwise     
across the wing being now made a part of
 the wing itself1 which was thus        
provided with two longitudinal ribs     
instead of one4 ,the additional rib     
occupied a central position1 and like   
the front rib was attached to the midrod
 by means of a strong wing clamp4 ,its  
outer end was united to the front rib1  
which was here bent into a quadrant of a
 circle4 ,this pair of wings had an     
expanse of #dce cm4 7#ad4c feet71 an    
area of #b4e square metres 7#bf4h sq4   
ft471 a weight of #ffj grammes 7#a4de   
pounds71 and a depth of curvature equal 
to one-tenth their width4  ,this        
construction offered a two-fold         
advantage in its resistance to both     
torsion and bagging1 for as the         

pressures upon the wing were nearly     
balanced about the middle rib1 the      
tendency to twist was reduced to a      
minimum1 while the bagging1 which       
results from the bending of the         
framework1 as distinct from p#jhg its   
twisting1 was greatly reduced by the    
manner in which the frame was put       
together1 the whole construction        
permitting a return to the system of    
wire guying at first adopted1 which had 
been found inapplicable to a wing having
 but a single longitudinal rib forming  
its front margin4 ,when completed1 the  
wings were strongly guyed with piano    
wire1 both above and below1 to guy-posts
 attached to the midrod1 and each       
cross-rib was separately guyed with wire
 chords4 ,although these wings had cost 
much in time and labor1 and contained   
many points of improvement1 they were   
eventually found to be too weak to      
support the aerodrome1 and were         
therefore abandoned without a trial in  
the field4  ,for the plane horizontal   

tail hitherto used a pair of curved     
wings was substituted1 similar in all   
respects to those just described1 but   
having only half their area1 and these  
were later replaced by a pair equal in  
size and in every way the counterpart of
 the front wings4 ,the tail as hitherto 
used accordingly disappeared1 and gave  
place to another having a wholly        
different function to perform2 for while
 the old tail1 like the rear pair of    
wings which superseded it1 was intended 
to bear a definite part of the weight of
 the aerodrome1 the new tail which was  
now added behind the rear pair of wings 
was not supposed to bear any part       
whatever of the weight1 but to act      
solely as a guide1 and this new feature1
 first introduced in ,october1 #ahie1   
was continued to the end4  ,this        
arrangement of the surfaces is quite    
different from that adopted by ,pnaud in
 #ahgb1 in which the tail became        
automatic in its action through its     
small angle of elevation as compared    

with that of the wings1 while still     
acting as a supporting surface1 whereas 
in the present arrangement the function 
of the tail was solely one of guidance4 
,this1 ,i believe1 was one of the       
important changes which perhaps as much 
as any other led to final success4      
,during the fall of #ahie a large number
 of experiments were made both in free  
flight with gliding models1 and in      
constrained flight with the             
whirling-table1 to determine the        
relative lifting power of the front and 
rear wings per unit of area1 and from   
these the following new rules were      
deduced for finding the center of       
pressure3  ,if a following wing is the  
size of the leader1 assume that its     
efficiency is #ff per cent per unit of  
surface4  ,if it is half the size of the
 leader1 assume that its efficiency is  
#ej per cent per unit of surface4  ,if  
it is half as large again as the leader1
 assume that its efficiency is #hj per  
cent per unit of surface4  ,for         

intermediate sizes of surface1          
proportionate values per unit of surface
 may be assumed4  ,if we consider the   
area of the front wing to be unity1 and 
that of the rear wing to be n1 and if m 
be the efficiency of the rear wing per  
unit of surface1 p#jhh the above is     
expressed in the following formul1 which
 it will be remembered take account only
 of wings following each other in the   
same or nearly the same plane1 and are  
not applicable where one wing is either 
above or below the plane of the other4  
,in the formul1 ,,cp is the resultant   
center of pressure upon both wings      
expressed in the notation described in  
,chapter ,,ii1 ,,cpfw is the center of  
pressure of the front wings1 and ,,cprw 
the center of pressure of the rear      
wings4  ,if the value of n lie between  
one-half and unity1         n  #a  m    
-------2           #c  while if the     
value of n lie between unity and        
#a-a_/b1          #f  #dn  m  --------- 
4           #ae4  ,in either case       

,,cpfw  mn,,cprw  ,,cp                  
---------------------- 2                
#a  mn  where the leading and following 
wings are equal                         
#c;,,cpfw  #b;,,cprw  n  #a1 m  #b_/c   
and ,,cp  ----------------------- 4     
#e  ,the steady flight of one of the    
gliding models referred to led to the   
construction of a new set of wings for  
,no4 #e1 patterned after those used on  
the gliding model4 ,these wings1 shown  
in ,plate #ag1 were rectangular in      
outline1 #bjj cm4#hj cm4 7#f4ef ft4#b4fb
 ft471 each wing having an area of #a4f 
square metres 7#ag4a sq4 ft47 ,they were
 constructed with spruce framing covered
 with ,china silk1 and were strongly    
guyed with piano wire in much the same  
manner as the light1 skin-covered wings 
already described1 which had preceded   
them4 ,the combined weight of the two   
pair was #aiej grammes 7#d4c pounds74   
,the long central rib was now much the  
larger of the two which1 as in the      
preceding wing1 formed the foundation of

 the structure4 ,it occupied a position 
two-fifths the distance from front to   
rear1 and presumably coincided at all   
points with the center of pressure of   
fore and aft sections of the wings1 so  
that the pressure in front of the rib   
was at all points balanced by the       
pressure in the rear1 and there was     
consequently little tendency in the wing
 to twist under pressure of the wind4   
,the two main ribs were rigidly         
connected by cross-ribs of spruce1 #bj  
cm4 7#h inches7 apart1 steamed and bent 
to the desired form4 ,the curvature of  
these ribs was the same for all1 and in 
depth was one-twelfth the width of the  
wing1 while the highest point of        
curvature was one-sixth of the distance 
from front to rear1 these ratios having 
been chosen as approximating those found
 in the wing of the soaring bird4 ,these
 wings were subsequently used in the    
first successful flights of the         
following year4  ,illustration3 ,,pl4   
#ag  ,,aerodrome ,,no4 #e4 ,,plan ,,of  

,,wings ,,and ,,system ,,of ,,guying    
p#jhi  ,during the year #ahie but two   
field-trials were made with the steam   
aerodromes1 and neither of these was    
successful2 but a great step forward had
 been taken in the construction1 guying 
and arrangement of the sustaining       
surfaces4 ,the wings had been made      
stronger with no increase in weight per 
unit of area4 ,on the contrary1 the     
ratio of weight of sustaining surfaces  
to area had been actually reduced from  
#dc to #bh grammes per square foot1 so  
that the surfaces were both lighter and 
stronger4  ,two longitudinal ribs had   
taken the place of the single one before
 used1 a second wing clamp had been     
added to correspond to the midrib1 the  
difficult problem of torsion had been   
effectually solved1 the system of guying
 greatly improved1 and it appeared that 
in the next trial the wings might be    
expected to bear the weight of the      
aerodrome without serious distortion4   
#ahif  ,in ,january1 #ahif1 two new     

pairs of wings were designed for ,no4   
#f1 and in order to give a greater      
efficiency to the rear wings1 they were 
made larger than the front ones1 the    
area of the latter being #bb square     
feet1 and of the former #bg square feet1
 and whereas the width of each wing had 
formerly been one-third of its length1  
it was now increased to two-fifths to   
correspond to those of ,no4 #e4  ,the   
progress made in construction and guying
 is shown by the fact that when on      
,january #bh one pair of the wings of   
,no4 #e was inverted and sanded1 the    
yielding at the tip was less than #e    
greater than at the root1 whereas at one
 time it had been #fe4 ,a similar test  
applied to a pair of wings of ,no4 #f on
 ,march #d gave even better results1 as 
the yield at the root was but #a #de1   
and at the tip #b #cj4  ,the successive 
stages of the development of the wing   
clamps are shown in ,fig4 #af4 ,in its  
final form the front wing clamp1 or that
 which held the main front rib1 shown at

 ,,ab 7#ahif71 had adjustable sliding   
pieces1 by means of which the wings     
could be set at any desired angle of    
elevation1 the wing as a whole revolving
 about the rear wing clamp1 shown at    
,,cd 7#ahif74  ,the general system of   
guying the wings1 as shown in ,plate    
#ag1 had been greatly improved4 ,in the 
present form a bowsprit and guy-posts   
firmly attached to the midrod furnished 
points of attachment for the piano wires
 with which the wings were guyed and    
held rigidly in place1 other wires being
 stretched across from wing to wing so  
as to maintain them at a constant       
diedral angle of about #aej4 ,the clamps
 by which the guy-posts were attached to
 the midrod1 are shown at ,,ef 7,fig4   
#af74  ,in the successful flights of    
,no4 #e on ,may #f1 the completed wings 
already described weighed together #aiej
 grammes 7#d4bi pounds71 and had a total
 sustaining area of #f4d square metres  
7#fh4h square feet71 the flying weight  
of the p#jij aerodrome was #aa1gge      

grammes 7#bf pounds71 and the sustaining
 surfaces therefore amounted to #b4f    
square feet to the pound1 which1 as the 
event proved1 was amply sufficient4     
,the 8tail-rudder10 shown in ,plate #ag1
 comprised a vertical and horizontal    
surface of silk intersecting in a       
central rod or axis1 having a length of 
#aae cm4 7#c4h feet74 ,the framing was  
of spruce and consisted of two sets of  
four arms1 each radiating from the      
central rod1 the hexagonal outline of   
the surfaces being formed of piano wire1
 over which the silk was drawn and      
sewed4 ,the area of each surface was    
about #j4f square metres 7#f4de square  
feet71 and the total weight was #cga    
grammes 7#j4h pounds74  ,a flat steel   
spring inserted in the forward end      
between the rudder and the midrod gave  
it a certain desirable degree of        
elasticity in a vertical direction4 ,the
 rudder was held in place by a pin      
passing through the midrod1 and was so  
set as to coincide with the line of     

direct flight1 its purpose1 as already  
explained1 being to guide the aerodrome1
 but to take no part in its sustention4 
,in balancing ,aerodrome ,no4 #e on ,may
 #f1 the wings were so adjusted that in 
accordance with the notation given      
above1 p4 #ae3   ,,cpfw  #aege   ,,cprw 
#adae4e2  and as the wings were of equal
 size1 from what has preceded in the    
present                     #c;,,cpfw   
#b;,,cprw  ,,cp#a                       
------------------------------          
#aeja4b4                                
#e  ,the center of gravity was located  
at #adig1 so that there should have been
 a very slight tendency on the part of  
the aerodrome to rise1 as was actually  
the case4 ,the formula was perhaps not  
quite so accurate as the prolonged      
flight of the aerodrome would seem to   
indicate1 as it takes no account of the 
thrust of the propellers1 which in      
action tended to elevate the aerodrome  
in front while their resistance would   
tend to depress it when they had ceased 

to revolve1 which consideration accounts
 for the action of the aerodrome on ,may
 #f1 as described in ,chapter ,,ix4 ,the
 formula may1 however1 be regarded as   
approximately correct4  ,in the final   
successful trial with ,no4 #f on        
,november #bh1 #ahif1 the wings used    
were similar in general construction and
 manner of guying to those of ,no4 #e on
 ,may #f1 but1 as shown in the          
photograph 7,plate #bi;,a1 ,chapter ,x71
 the front rib at its outer extremity   
was bent to a quadrant to connect with  
the midrib1 this construction being     
somewhat stronger than that adopted in  
the wings of ,no4 #e4 ,the curvature was
 but one-eighteenth of the width of the 
wing instead of one-twelfth as in ,no4  
#e4 ,the front and rear pairs were      
similar and equal and had a combined    
area of #e square metres 7#ed sq4 ft471 
and a weight of #baed grammes p#jia     
7#d4gd lbs474 ,the flying weight of the 
aerodrome was #ab1abj grammes 7#bf4g    
lbs471 the sustaining surface thus      

amounting to slightly more than #b      
square feet to the pound4  ,the position
 of the wings1 in accordance with the   
notation adopted1 was   ,,cpfw  #aefc4b1
   ,,cprw  #acgd4  ,since the wings were
 equal in size1                         
#c;,,cpfw  #b;,,cprw  ,,cp#a            
-----------------------------   #adhg4e4
                                      #e
  ,the center of gravity was located at 
#adhd1 which was #c4e cm4 in the rear of
 the center of pressure4 ,the flight was
 approximately horizontal1 and the      
setting seems to have been as accurate  
as could be desired4 ,the angle of      
elevation of the wings at the root was  
#aj #cj1 and so well were they guyed    
that there was no visible yielding at   
any point during the flight4 ,as the    
midrod during flight was approximately  
horizontal the angle of elevation of the
 wings may be taken as #aj #cj2 the     
efficiency of the rear wings was        
two-thirds that of the front wings1 and 
the effective area was therefore        

#bgbgb_/c  #de square feet4  ,the wings 
being very nearly plane we have         
therefore the data for determining the  
soaring speed from the formula of       
8,aerodynamics0 7,chapter ,,vi1 p4 #fj74
   ,w  ,p cos   k,a,v#b;,f77 cos 1  in  
which ,w  #bf4g pounds2 ,a  #de sq4 ft42
 k  #j4jjaff2   #aj #cj2 ,f 77 cos      
#j4cec4 ,by substituting these values in
 the formula we obtain ,v  #cb feet per 
second4  ,the speed actually attained1  
however1 was about #cj miles an hour1 or
 #dd feet per second1 which seems to    
indicate that the angle of elevation    
under pressure was reduced to much less 
than #aj #cj4 ,for a velocity of #dd    
feet per second1 the theoretical value  
of  would be but #f4 ,in this           
calculation1 however1 the hull          
resistance and that of the system of    
guy-wires1 which must have been         
comparatively large1 has been omitted4  
,it would appear1 therefore1 that the   
actual results obtainable in flight are 
much more favorable than calculations   

based on experimental data would        
presuppose4   p#jib    ,,chapter ,,ix   
,,history ,,of ,,launching ,,apparatus  
,,and ,,field-,,trials ,,of             
,,aerodromes #d1 #e ,,and #f            
,,launching ,,apparatus  ,i have        
elsewhere mentioned that the            
difficulties of launching even a very   
small model aerodrome are considerable4 
,early experiments were tried with an   
apparatus something like a gigantic     
cross-bow1 and in later years with      
various forms of pendulum1 all of which 
latter brought out the inherent         
theoretical defect of the movement of   
rotation of the aerodrome1 and were     
otherwise practically inefficient4  ,a  
device1 consisting of two pendulums1 one
 behind the other1 connected by a rigid 
rod1 from which the aerodrome could be  
suspended and cast off without rotation1
 was at one time considered1 but        
abandoned4 ,experiments were also made  
with several forms of railroad1 upon    
which the aerodrome was to run up to the

 moment of release1 before the form of  
launching apparatus1 which finally      
proved successful1 was adopted4  ,all   
these had failed chiefly for two        
reasons2 first1 it was difficult to     
cause the aerodrome to be released just 
at the moment it attained sufficient    
speed to soar2 second1 the extensive    
surface presented to the wind by the    
wings of the aerodrome1 made it         
necessary to provide means for holding  
the machine securely at several points  
up to the moment of release without     
danger of interfering in any way with   
the aerodrome when it was cast into the 
air4 ,this proved a serious problem1    
which can be appreciated only by one who
 has seen such a machine in the open    
air1 where its wings are subject to     
movement and distortion by the slightest
 breeze4 ,the steps by which these      
difficulties were removed and the final 
type of launching apparatus perfected   
are recorded in the following pages in  
connection with the field-trials of the 

model aerodromes4    #ahib  ,as the end 
of the year #ahib approached and with it
 the completion of an aerodrome of large
 size which had to be started upon its  
flight in some way1 the method and place
 of launching it pressed for decision4  
,one thing at least seemed clear4 ,in   
the present stage of experiment1 it was 
desirable that the aerodrome should---if
 it must fall---fall into water where it
 would suffer little injury and be      
readily recovered1 rather than anywhere 
on land1 where it would almost certainly
 be badly damaged4 p#jic  ,the shores of
 the ,potomac on both banks were        
scrutinized for this purpose1 from a    
point about two miles above ,washington 
to below ,chopawamsic ,island1 some     
thirty miles below the city4 ,several   
lofty and secluded positions were found1
 but in all these there was the danger  
that the aerodrome might be wrecked     
before reaching the water1 or1 turning  
in its course1 fly inland2 but more than
 this1 it could be launched only on the 

rare occasions when the exact wind was  
blowing which the local conditions      
demanded4  ,finally1 the idea1 which    
seems obvious enough when stated1       
presented itself of building a kind of  
house-boat1 not to get up initial motion
 by the boat's own velocity1 but to     
furnish an elevated platform1 which     
could be placed in the midst of a       
considerable expanse of water1 if       
desired1 under conditions which admitted
 of turning in the direction of the     
wind1 as it need hardly be repeated that
 it was indispensable to the machine1 as
 it is to the bird1 to rise in the face 
of a wind1 if there be any wind at all4 
,the house-boat in question was nothing 
more than a scow about #cj feet long by 
#ab feet wide1 upon which a small house 
was erected1 to be used for the         
occasional storing of the aerodromes4   
,on account of the accidents which were 
certain to occur in the first attempts1 
it was fitted up with the means of      
making small repairs4 ,on the roof of   

the house there was a platform upon     
which the operator stood when making a  
launch1 and upon which were mounted the 
launching devices hereafter described4  
,this boat1 shown in ,plate #ah1 was    
completed in ,november1 #ahib4    #ahic 
,by the kindness of the ,superintendent 
of the ,coast ,survey1 the house-boat   
was towed in ,may1 #ahic1 down to       
,chopawamsic ,island1 a small island    
near the western bank of the ,potomac   
,river1 not far from the ,quantico      
station of the ,washington and ,richmond
 ,railroad ,company4 ,a map of the      
island and the adjacent land and water  
is shown in ,plate #ai4  ,the house-boat
 was at all times moored somewhere on   
the west side of the island1 in the     
stretch of quiet water between that and 
the west shore of the river4 ,the waters
 shown here are1 with the exception of a
 narrow channel1 very shallow1 and1     
indeed1 partly dry at low tide1 so that 
there was no danger of an aerodrome     
being lost1 unless its flight carried it

 a long distance away and over the land4
    ,,field ,,trials#bi  ,aerodrome ,no4
 #d1 as shown in ,plate #aa1 had a      
single midrod1 a flying weight of #i    
pounds1#cj and supporting surface1      
consisting of wings and tail1 of #ah    
square feet4 p#jid ,its engines1 with   
about #ajj pounds pressure1 developed an
 aggregate of #j4d ,h4 ,p41 and lifted  
#ej per cent of the flying weight4 ,the 
propellers were #fj cm4 7#b feet7 in    
diameter and #a-a_/d pitch ratio4  ,the 
aerodrome was intended to be launched by
 a contrivance called the 8starter10    
which was an inclined rod1 hinged at the
 bottom1 on the top of which the        
aerodrome was supported on a rod which  
was thrown down at the instant of       
flight1 giving the aerodrome a slight   
forward impulse1 with the expectation   
that it would get up sufficient initial 
speed to soar from the action of its    
propellers4  ,on ,november #ah the      
writer 7,l71 with ,dr4 ,barus 7,b7 and  
the two mechanics 7,r and ,m71 went to  

,quantico by an early train1 and        
superintended with interested           
expectation the arrangements for this   
first trial in the open air of the      
mechanism which had now been over two   
years in preparation4  ,we met with an  
unexpected difficulty--that of launching
 the aerodrome at all1 for though the   
wind was only a very gentle breeze1 it  
was only by holding it down with the    
hands that it was possible to keep the  
aerodrome in position for the launch1   
during the few minutes which passed from
 the time it was placed upon the        
apparatus to the time of releasing it4  
,whether the launching device itself    
might be effective or not could not be  
ascertained1 since it was found that    
nothing which could even be called an   
attempt to launch could be made except  
in an absolute calm2 a condition of     
things very difficult for any one to    
understand who has not passed through   
the experience4 ,the writer returned to 
,washington at the close of the day     

without having done anything1 but having
 learned a great deal4  ,november #bj4  
,l1 with ,b and ,m1 came down again1 and
 waited until #d4bj1 when1 the breeze   
having fallen to almost a calm1 the     
aerodrome was maintained in place on the
 launching apparatus with great         
difficulty1 while it was repeatedly set 
on fire by the scattering liquid fuel4  
,finally it was let go1 and fell close  
to the house-boat1 the tail striking the
 edge of the platform4 ,the immediate   
cause of failure was the defective      
launching apparatus1 for the design of  
which the writer felt himself           
responsible4  ,november #bd4 ,l1 with   
,b1 ,m1 and ,r came down again to       
,quantico1 but the very moderate wind   
proved completely prohibitory to any    
attempt at launching1 and all returned  
again to ,washington4  ,november #bg4   
,l1 with ,b and ,m1 came down to try a  
new launching apparatus1 not different  
in principle from the preceding one1 but
 of better construction4 ,the morning   

was exceptionally calm1 but the engines 
were found to be out of order1 and      
precious time was spent in slight       
repairs which should have been made in  
the shop4 ,at #c4cj p4 m41 when the     
engines were at last ready1 the         
exceptional calm gave place to a very   
gentle and almost imperceptible breeze1 
p#jie which1 nevertheless1 again proved 
prohibitory to the launching1 and with  
extreme disappointment the party        
returned to ,washington1 it being at    
last fully recognized that unless some  
ways were found of holding down all the 
extended supporting surfaces upon the   
launching piece1 and at the same time of
 firmly clamping the body of the        
aerodrome until it could be dropped1 as 
well as of releasing all this           
simultaneously at the critical instant1 
no attempt at launching was likely to   
succeed except in such an entire and    
perfect calm as rarely occurs4          
,independent of this launching          
difficulty1 some way of protecting the  

fires from the wind had to be found1    
which was by no means easy1 since an    
efficient protection meant an enclosure 
of them and a diminished influx of air1 
of which it was essential that there    
should be an unlimited supply4          
,december #a4 ,l1 with ,b1 ,r1 and ,m   
proceeded to ,quantico4 ,the same       
conditions presented themselves and the 
party returned1 without effecting       
anything4  ,december #g4 ,l1 ,b1 ,r1 and
 ,m present2 day overcast but perfectly 
calm4 ,taught by experience1 we had     
everything ready1 and a little after one
 o'clock the launch was made4 ,the      
aerodrome fell directly into the boat1  
the rod of the starter having broken4   
,it was little damaged1 but in view of  
the injury and the rising wind1 all     
other attempts were abandoned for the   
day4  ,december #aa4 ,present1 ,l1 with 
,b1 ,r1 and ,m4 ,a new 8starter0 had    
been devised and brought down1 but was  
not yet quite ready for use1 and an     
attempt was made to employ the old one  

with the improvements suggested by      
experience1 but1 after two attempts to  
launch1 the work was abandoned for the  
day1 owing this time not to the         
launching apparatus1 but to troubles in 
the engines and pumps1 due probably to  
injuries received in the fall of the    
#gth1 which were not detected until the 
time of the actual trial4  ,december    
#bj4 ,l1 with ,b1 ,m1 and ,g1 present2  
engine and aerodrome in order and       
everything apparently favorable4 ,what  
seemed to be an almost entire calm came 
toward evening1 yet once more the all   
but imperceptible breeze which prevailed
 was found to defeat all arrangements   
for holding the aerodrome to the        
launching ways before it was let go4    
,trips to ,quantico were also made on   
,november #bd1 and ,december #a and #ba1
 of which no account is given as the    
very moderate wind which prevailed in   
each case precluded any attempt at      
launching the aerodrome4  ,it will be   
seen that eight trips were made to      

,quantico1 and that1 far from any flight
 having been made1 not once even was the
 aerodrome launched at all4 ,the        
principal cause for this lay in the     
unrecognized amount of difficulty       
introduced by the very smallest wind1   
irrespective of the unfitness of the    
launching apparatus to give the desired 
initial speed and direction4  ,in all   
these trials1 the aerodrome rested on   
the launching apparatus1 by which it was
 projected forward by means of a spring 
in such a way as not to interfere with  
the propellers4 p#jif  ,previous tests  
with the rubber-driven models had       
demonstrated the futility of all simple 
pendulum types of 8cast off10 and       
likewise all the trials hitherto of a   
railroad form of launching apparatus1 in
 which the aerodrome was mounted on a   
car1 which had itself to get out of the 
way1 were equally failures1 so that when
 the device referred to above proved to 
be worthless1 it seemed that almost     
every plan had been exhausted4 ,there   

were1 moreover1 other difficulties1 some
 of which have been indicated above1    
such as that of making the burners work 
properly in even a moderate wind during 
the very short time required for        
attaching the wings and so adjusting the
 aerodrome on the launching apparatus4  
,these difficulties1 which1 now that    
they have been overcome1 seem           
difficulties no longer1 but which then  
seemed insuperable1 were all connected  
with the ever-present problem of weight4
 ,it would have been easy to make rigid 
sustaining surfaces which would not bend
 in the wind2 to make fires which would 
not go out2 and easy to overcome all the
 impediments which seem so trivial in   
description and were so formidable in   
practice1 were it not that the mandate  
of absolute necessity forbade this being
 done by any contrivance which would add
 to the weight of an already            
phenomenally light construction4 ,the   
difficulties of the flight as they were 
seen in the workshop were multiplied1   

then1 beyond measure by the actual      
experiments in the field1 and the year  
closed with a most discouraging outlook4
    #ahid  ,the new year began without  
any essential improvement in the means  
already described1 though a new         
launching apparatus had been devised by 
the writer1 which was scarcely so much  
an apparatus for launching1 in the      
ordinary sense of the word1 as one of   
holding the aerodrome out over the      
water1 and simply letting it drop from a
 height of about #be feet1 during which 
fall it was hoped 7exact data being     
unobtainable in advance of experiment7  
that there would be time for the        
propellers to give the aerodrome the    
necessary soaring speed before reaching 
the water4 ,this device consisted of an 
inverted tripod1 which held the         
aerodrome comparatively steady by three 
bearing points1 while a cross-bar of    
wood was added to prevent the wings from
 swaying before the launch4 ,previously1
 the supporting surfaces1 wings and     

tail1 had been put on only at the last  
minute4 ,now it became possible to keep 
them on in a gentle breeze for an       
indefinite time before launching4       
,january #i4 ,the previous day having   
been spent in practicing the steps      
preliminary to launching1 so as to avoid
 delay in assembling and mounting the   
aerodrome1 the writer1 with ,dr4 ,graham
 ,bell1 went to ,quantico4 ,the day was 
calm1 and every condition seemed        
favorable4 ,the aerodrome was dropped   
fairly1 under full steam1 and it fell in
 a nearly horizontal position1 but      
touched the water at a distance of only 
#ej or #fj feet1 evidently before the   
necessary initial speed p#jig could be  
impressed on it by its engines4 ,the    
conclusion should have been that by this
 method nothing but a practically       
unsuitable height would suffice to start
 the aerodrome in a calm1 though it     
might perhaps be done in the face of a  
considerable breeze4  ,may #be4 ,after a
 considerable interval of delay1 due to 

the river being closed by ice and other 
causes1 ,aerodrome ,no4 #d was again    
dropped from the starter under nearly   
the same conditions as in the trial of  
,january #i1 and with a quite similar   
result1 the final conclusion being that 
this method must be abandoned4 ,it may  
be added that a vertical rudder was     
tried on this day4  ,june #ab4 ,no4 #d1 
with an improved blast1 was tried at    
,quantico1 ,mr4 ,goode being present4   
,the day ended in failure from another  
cause1 the improved blast1 which worked 
well in the shelter of the shop1 but    
proved useless in the field1 being      
extinguished by the feeblest wind4 ,at  
this time 7in ,june and ,july7 ,i       
designed a horizontal railroad with     
launching springs and track1 underneath 
which ran a car which held the aerodrome
 firmly until the moment of automatic   
release4 ,this apparatus finally proved 
to be the successful solution of the    
launching problem4 ,the description     
given later1 with the drawing in ,plate 

#ah1 shows the after-improvements1 but  
no specific change from that in use from
 the first4  ,about this time ,i also   
arranged for certain changes in the     
boilers and burners1 having decided that
 ,i would not go into the field without 
some ground for confidence not only that
 the aerodrome could be launched        
successfully1 but that a steady flame   
could be maintained under the boilers4  
,october #f4 ,no4 #d1 as remodelled1    
having a flying weight of about #ad4e   
pounds1 a supporting surface of about   
#bh square feet1 with a total engine    
power of about #j4e ,h4 ,p41 and having 
lifted #dj per cent of its weight on the
 pendulum1 was taken down the river for 
trial with the new railroad launching   
apparatus1 and several days were spent  
in erecting the launching apparatus on  
the house-boat1 and in launching 8dummy0
 aerodromes from it for practice4       
,aerodrome ,no4 #d then being fitted    
under conditions which apparently       
insured a good start 7the center of     

pressure being nearly over the center of
 gravity1 the root angle of the wing    
being zero1 the midrod nearly           
horizontal1 the engine working well1 and
 with apparently ample sustaining       
surface7 was finally successfully       
launched1 but the hopes which were      
reasonably entertained proved to be     
unfounded4 ,the result of this first    
actual trial of a 8flying machine0 in   
free air was most disconcerting1 for the
 aerodrome1 which had in theory many    
times the power required for horizontal 
flight1 plunged into the water with its 
engines working at full speed1 after a  
course hardly longer than that performed
 by the dummy4 ,this result was at first
 inexplicable4  ,no4 #d1 then1 did not  
fly at all1 from some at first          
inscrutable cause1 and it was decided to
 make a trial of ,no4 #e1 though it was 
hard to put the result of so much p#jih 
time1 painstaking and cost to the hazard
 of destruction4 ,with the experience   
just acquired from the trial of ,no4 #d1

 the wing of ,no4 #e was set at an angle
 of about #bj with the midrod1 and the  
tip was secured by a light cross-piece1 
so guyed that the wing as a whole1 while
 set at this considerably greater angle 
with the rod1 was stiffer than before4  
,in addition to this1 the air chamber   
was moved back so that the center of    
gravity was from #f to #aj cm4 behind   
the 7calculated7 center of pressure4    
,these changes were made in order to    
insure that the front should at any rate
 keep up1 and it did4  ,the aerodrome   
was launched successfully with the      
engines working under a pressure of #aaj
 pounds of steam4 ,the head rose        
continually until the mid-rod stood up  
at an angle of about #fj1 checking all  
further advance4 ,it remained in the air
 in a stationary position for nearly a  
second1 and then slid backward into the 
water1 striking on the end of the rudder
 and bending it4 ,the distance flown was
 about #ab metres1 and the time of      
flight #c seconds4 ,one of the          

propellers was broken short off1 and the
 shaft was bent4  ,it thus became       
clearly evident that some cause         
prevented the proper balancing of the   
machine1 which was necessary to secure  
even approximately the theoretically    
simple condition of horizontal flight4  
,it was all-important that the angle of 
the front wing should be correct1 but   
its position could not be accurately    
known in advance of experiment1 and this
 experiment could only be made with the 
machine itself1 and involved the risk of
 wrecking it4  ,these trials gave a very
 vivid object lesson of what had already
 been anticipated1#ca that the          
difficulties of actual flight would     
probably lie even more in obtaining     
exact balance than in the first and more
 obvious difficulty of obtaining the    
mere engine power to sustain a machine  
in the air4 ,the immediate problem was  
to account for the totally different    
behavior of the two aerodromes in the   
two flights1 under not very different   

conditions4  ,observations of the       
movement of the two aerodromes through  
the air1 as seen by the writer from the 
shore1 seemed to show1 however1 that the
 wings did not remain in their original 
form1 but that at the moment of         
launching there was a sudden flexure and
 distortion due to the upward pressure  
of the air4 ,the time of flight was too 
short1 and the speed too great1 to be   
sure of just what did occur1 but it     
seemed probable that the wings flexed   
under the initial pressure of the weight
 which came upon them at the moment of  
launching1 and that they were in fact1  
while in the air1 a wholly different    
thing from what they were an instant    
before1 so that a very slight initial   
difference in the angle at which they   
first met the air might cause the air to
 strike in the one case on the top of   
the wings and throw the head down1 and  
in the other case so as to throw the    
head up4 ,to ascertain the extent and   
character of this flexure1 caused1 it   

will be observed1 by p#jii the weight of
 the aerodrome suddenly thrown on the   
wings1 ,i inverted the aerodrome and    
distributed a weight of dry sand equal  
to that of the whole machine evenly over
 the supporting surfaces4 ,it was found 
that under the weight of the sand the   
extremity of the wings bent to an angle 
of #de downwards 7and consequently must 
have bent to an angle of #de upwards in 
the air71 a condition of affairs worse  
than anything that had been suspected1  
and seeming to demand the entire        
reconstruction of the wings with a      
strength and consequent weight for which
 there was no means of providing4       
,there had been some injuries to the    
machines in the trials of the #eth and  
#fth1 and these were repaired4 ,a new   
float had been made for ,no4 #d1 and a  
new set of larger wings for ,no4 #e4    
,each of these wings had a length of #gf
 inches and a breadth of #be inches1    
making the total surface of the two     
#bf4d sq4 ft41 while that of the tail   

was #ac4b sq4 ft41 or about #dj sq4 ft4 
in all4  ,october #bb4 ,when ,no4 #e was
 finally prepared for another trial1 its
 condition was as follows3  ,flying     
weight                                  
#bb    pounds ,area of supporting       
surfaces 7wings and tail7     #dj    sq4
 ft4 ,sq4 ft4 of surface per pound of   
weight            #a4hcb ,engine power  
with #aae lbs4 steam pressure           
#a4j  ,h4 ,p4#cc ,power necessary to    
soar                           #j4ce ,h4
 ,p4 ,theoretical soaring speed 7plane  
wings at #bj7   #bd    ft4 per sec4     
,previous lift on pendulum              
#dj    per cent of                      
flying weight  ,october #be4 ,the       
aerodromes having been taken to         
,quantico on ,october #bc1 and          
satisfactory experiments made with      
dummies in order to test the launching  
apparatus1 the house-boat was carried   
out into midstream and moored4          
,aerodrome ,no4 #d was launched in the  
face of a wind of about #aajj feet per  

minute4 ,the midrod was at a very small 
inclination with the horizontal1 about  
#c4 ,the angle 77 of the chord of the   
curved wing measured at the rod1 where  
it was rigidly held1 was #ae4 ,the      
adjustment was such as to bring the ,,cg
 immediately under the ,,cp1 without any
 allowance for the fact that the line of
 propeller thrust was below the ,,cp4#cd
 ,the aerodrome under these conditions  
was launched with the head high4 ,it    
made a real1 though brief1 flight of    
about #acj feet in #d-a_/b seconds1 when
 it swung abruptly round through #ij1   
and1 losing headway1 sank continuously1 
finally falling backward into the water4
  ,october #bg4 ,aerodrome ,no4 #d1     
having been repaired and guyed with     
wires from the wings to vertical        
guy-posts beneath1 was launched again1  
but one of the p#ajj guy-wires caught on
 the launching car1 and threw the       
aerodrome immediately into the water    
with but little damage4  ,on the same   
day ,no4 #e was launched4 ,the          

theoretical ,,cp,,cg was nominally #j1  
but1 for the reasons stated in the      
footnote on p4 #ii1 was really something
 positive1 that is to say1 the ,,cp was 
really somewhat in advance of the ,,cg2 
inclination of midrod less than  7#bj74 
,the aerodrome under these              
circumstances1 while keeping its head   
up1 at first fell rapidly1 yet seemed   
about to rise just as it struck the     
water1 conveying the idea that if the   
launching had been made with a greater  
initial velocity it would have risen and
 cleared the water4 ,the wings visibly  
pocketed1 however1 and it was clear that
 some better disposition must still be  
made for them4 ,the flight was #c-a_/b  
seconds4  ,no4 #e was tried again on the
 same day with larger wings1 whose area 
was #dj square feet4 ,these wings1      
though stiffer1 pocketed a little1 #bj  
as before4 ,it flew rapidly1 and at     
first horizontally1 to a distance of    
#ajj feet or more against a five-mile   
breeze4 ,it then turned abruptly round  

through #ahj1 at first falling 7from    
loss of headway71 then distinctly       
rising1 and at the same time throwing   
its head up until it reached an angle of
 nearly #fj with the vertical1 when it  
fell backward after a flight of between 
#f and #g seconds4 ,the wings were      
evidently not yet strong enough to      
resist flexure4  ,november #ba4 ,no4 #e1
 in nearly the same condition as before4
 ,two extra springs had been placed on  
the launching car1 in order to give the 
aerodrome a greater initial velocity    
than before4 ,everything appeared       
favorable1 but as it left the launching 
track a piece flew out of the port      
propeller1 in spite of which the        
aerodrome1 after dropping #e feet1 rose 
bodily at an angle of #de and fell      
backward into the water 7time1 #e       
seconds74  ,another trial was made the  
same day with the same aerodrome1 under 
similar conditions1 except that the     
angle of inclination 77 was reduced to  
#g4 ,it now1 with all the other         

circumstances of launching like those   
immediately before1 behaved entirely    
differently1 plunging head downward into
 the water at a distance of #cj feet4   
,once more it was shown beyond dispute  
that the wings must somehow be made even
 stiffer4  ,december #h4 ,another trial 
was undertaken with ,no4 #e1 the ,,cg   
being #aj cm4 in front of the ,,cp at   
rest4 ,the root angle of the wings was  
#ah1 tip angle #bg1 elevation of midrod 
#a in #bd4 ,the other changes made since
 the previous trial consisted chiefly in
 the increased weight due to the longer 
and stronger frames and shafts that were
 made to carry #ajj cm4 propellers4 ,the
 flight obtained was so short that it   
was as unsatisfactory as before4  ,the  
aerodrome rose in the air after leaving 
the launching apparatus1 and then slid  
back into the water in the plane of its 
own wings4 ,on the first trial1 it      
struck the boat1 and was slightly       
injured2 on the second1 with root angle 
of p#aja wings #aj1 tip angle #bj1 the  

flight partook of the same character1   
but the machine struck the water clear  
of the boat4  ,the fact that with the   
,,cg #aj cm4 in advance of the          
calculated ,,cp the aerodrome steadily  
rose in front1 seems to indicate that   
the rule used at that time for          
calculating the ,,cp 7see ,chapter ,,ii7
 was not very accurate4 ,this rule was  
based upon the assumption that the tail1
 having an area equal to one-third the  
entire sustaining surface1 supported    
one-third the total weight 7expressed by
 the formula ,,cp  7#b;,,cpwm           
,,cptm7_/#c1 where ,,cpwm and ,,cptm    
represent respectively the ,,cp of the  
wings and tail in motion71 and that the 
,,cp of each surface was one-fifth its  
width in front of the center of figure4 
,december #ab4 ,four days later1 the    
tail had been moved back #ba cm41 thus  
carrying the ,,cg back #g cm41 but the  
vertical rudder 7weighing #aje grammes71
 for which there was now no room1 was   
taken off1 which in a measure           

counteracted this change4  ,a trial was 
then made with the wings set at an      
initial angle of #h at the root and #bj 
at the tip4 ,the aerodrome was released 
with the engines working under a steam  
pressure of #ij pounds1 and soared off  
horizontally for some distance1 when    
suddenly it swerved to the right as     
though something on that side had given 
out1 and turning quite through #ahj     
headed toward the boat1 striking the    
water about #gf feet away4 ,the time of 
the flight was #d seconds4  ,it was     
found upon the recovery of the machine  
that one of the propellers had been     
twisted through #ij1 so that the two    
were no longer symmetrical4 ,the turning
 may have been due to this twist or to  
unequal influence of the wind upon the  
two wings2 for when ,i applied the sand 
test to the wings after returning them  
to ,washington1 it was found that they  
deflected so much that the grains would 
not lie upon them1 which1 to a great    
extent1 explains the failure to secure a

 better flight4  ,thus the end of       
another year had been reached1 and what 
might be called a real flight had not   
yet been secured4 ,the only progress    
that seemed to have been made was that  
the aerodromes were not quite so        
unmanageable and erratic in their       
flights as at the beginning of the year1
 and that it had been demonstrated1 at  
least to the writer's satisfaction1 that
 the power was sufficient for the work  
to be done4 ,the launching device had   
been so perfected that it worked        
satisfactorily1 but the problem of      
balancing seemed as far from solution as
 before4    #ahie  ,while1 for          
convenience in narrating the progress of
 the work with the aerodromes1 each year
 has been treated as a unit1 it is1 of  
course1 understood that the work itself 
shows no especial difference between the
 closing of one year and the beginning  
of another4 ,changes which had important
 effects were introduced p#ajb at       
various times1 but were1 of course1 made

 as they suggested themselves without   
any reference to time or season4 ,but   
while it was customary to make1 from    
time to time1 a rsum of the progress of 
the work1 yet at the closing of the     
calendar year it was the custom to make 
a more complete digest of just what had 
been accomplished during the year4      
,upon thus reviewing the progress of the
 work during #ahid1 it was felt that the
 results which had been accomplished for
 such a large expenditure of time seemed
 small1 since no real flight had been   
made by any of the aerodromes1 and no   
definite assurance that a successful    
flight would be obtained within the     
immediate future seemed warranted by    
what had already been accomplished4 ,but
 now that the principal difficulties    
connected with the launching apparatus  
had been overcome1 thus permitting the  
aerodromes themselves to be given a fair
 trial1 the belief was encouraged that  
the continuance of the actual tests of  
the machines1 with slight changes which 

previous tests had shown advisable1     
would finally result in a successful    
flight4  ,the early weeks of #ahie were 
spent in a series of pendulum tests on  
,no4 #e1 and in making such slight      
changes as these tests indicated would  
be advisable4 ,as a result of small     
improvements introduced in the boilers1 
,no4 #e had by the middle of ,march     
shown a repeated lift of considerably   
over #ej per cent1 and in some tests as 
much as #fb per cent of its flying      
weight4 ,certain radical changes        
previously described in ,chapter ,,vii  
were also made in ,aerodrome ,no4 #d1   
and in the pendulum tests of it a lift  
of #dd per cent of its flying weight had
 been obtained4  ,encouraged by the     
better results which the aerodromes had 
shown in the above tests1 it was decided
 to test them again in free flight1 and 
they were accordingly sent down to      
,quantico in charge of the two          
mechanics1 ,r and ,m1 ,mr4 ,langley1    
accompanied by ,dr4 ,graham ,bell1 whom 

he had invited to witness the tests1    
following on ,may #h4 ,on the evening of
 ,may #h ,no4 #e was mounted on the     
launching apparatus in order to drill   
the mechanics so that when favorable    
weather presented itself the aerodrome  
could be got ready for launching with   
the minimum delay4  ,on ,may #i ,mr4    
,langley and ,dr4 ,bell reached the     
house-boat at #e a4 m41 but even with   
the drill of the previous evening the   
mechanics were not able to have ,no4 #e 
ready for trial until #f4ae a4 m4 ,the  
principal conditions of ,no4 #e at this 
time were3   ,total weight #aa1bjj      
grammes 7#bd4f pounds71 including #hjj  
grammes of  fuel and water4 ,previous   
lift on the pendulum #ed per cent1 with 
a  steam pressure of #aej pounds4 ,with 
this steam pressure the engine  made    
about #fjj ,r4 ,p4 ,m4 when driving the 
#ie cm4 propellers1 which  through their
 reduction gearing made about #ejj ,r4  
,p4 ,m4 p#ajc  ,when the aerodrome was  
balanced for flight so as to bring the  

theoretical 8center of pressure in      
motion0 over the center of gravity1 it  
was found that it was not possible to   
carry the center of gravity in front of 
this point1 although it was known by    
experience to be necessary4 ,accordingly
 in the first trial the outer ends of   
the tail were pressed down by the guys  
so that the wind of advance tended to   
lift the tail and throw the head down   
more than if the tail had been flat4    
,furthermore1 the float1 weighing #bjj  
grammes1 instead of being placed in its 
normal position near the base of the    
bowsprit1 was carried out to its        
extremity1 this change in the position  
of the float alone being sufficient to  
carry the center of gravity forward     
three or four centimetres4 ,the curved  
wings were set at an angle of nine      
degrees at the root and eleven degrees  
at the tip4 ,they were well guyed1 and  
in flight appeared to be not materially 
twisted or altered4  ,it was anticipated
 that the pressing down of the outer    

ends of the tail and the shifting of the
 center of gravity would cause the      
aerodrome to point downward in flight1  
and this anticipation was verified in   
the test4 ,at #f4ae a4 m4 the aerodrome 
was launched at a steam pressure of #abj
 pounds4 ,a perfect calm prevailed at   
the time and the machine started        
straight ahead4 ,there was no           
perceptible drop at the moment it was   
released from the launching car1 but a  
smooth and steady descent until it      
struck the water1 nose down1 at a point 
approximately #bjj feet from the boat4  
,dr4 ,bell noted that the length of time
 the aerodrome was in the air was #b4h  
seconds4 ,one of the propellers was     
broken and the other one was found to   
have twisted its shaft one-fourth of a  
turn4  ,at #i4de a4 m41 the wings having
 been dried1 ,no4 #e was again tried4   
,the float was moved back to its normal 
position at the base of the bowsprit1   
and the guys1 by which the outer ends of
 the tail had been depressed in the     

previous trial1 were so adjusted that   
the tail was flat4 ,the machine was1    
therefore1 in the condition of          
theoretical equilibrium for rapid motion
 with a plane wing4 ,all the other      
conditions were precisely as in the     
previous trial1 except that the         
round-end #ajj-;centimetre propellers   
were substituted for the #ie-;centimetre
 ones which had been broken1 and a new  
paper-covered tail was used4 ,the       
mechanic in charge was directed to let  
the steam reach its highest pressure    
consistent with a flight of one-half a  
minute1 before launching the machine1   
but he seemed to have lost all sense of 
the length of time the fuel and water   
would last1 as he let the engines run   
until almost the whole charge was       
exhausted before launching it4 ,the     
aerodrome went off almost horizontally1 
then turned up into the wind and rose to
 an angle of about twenty degrees2 then 
7while moving forward7 slowly sank as   
though the engine power had given out1  

as in fact it doubtless had4 ,the actual
 distance travelled was #abc feet and   
the length of time #g4b seconds4 ,while 
the exhaustion of the fuel and water    
prior to launching the machine had      
prevented what apparently would         
otherwise have been an p#ajd exceedingly
 good flight1 yet the fact that the     
aerodrome rose immediately after being  
launched1 and continued to do so until  
the power gave out1 was in itself very  
encouraging4  ,at #a4dj p4 m4 ,no4 #e   
was again ready for trial 7the third one
 for the day71 and this time ,mr4       
,langley and ,dr4 ,bell witnessed it    
from a greater distance in hopes of     
being able more clearly to study its    
behavior when actually in the air4  ,the
 previous trial having missed success   
through the fuel and water having been  
consumed before the machine was         
launched1 special instructions were     
given to avoid the recurrence of this   
mistake4 ,but the machine was held for  
probably two minutes after the burners  

were lighted1 with very much the same   
result as before4 ,the conditions of the
 aerodrome were the same as in the      
previous trial1 except that the tail was
 a little flatter1 so as to tend to make
 the head slightly lower in flight4 ,it 
was launched at an angle of about thirty
 degrees with the very gentle wind that 
was blowing1 and1 apparently under the  
direction of the rudder1 turned into the
 wind1 the midrod rising to an angle of 
about twenty degrees and 7as noted in   
,mr4 ,langley's record book7 8,the whole
 machine absolutely rising during five  
or six seconds--a fine spectacle6 ,then 
the power visibly gave out1 the         
propellers revolving slower4 ,it settled
 forward and lost nearly all of its     
forward motion at the end of about seven
 seconds1 but did not finally touch the 
water until ten and a quarter seconds40 
,while the length of time that the      
aerodrome had been sustained in the air 
was so short that no actual flight had  
really been achieved1 yet the results   

encouraged the belief that with the     
aerodrome more accurately balanced1 it  
could reasonably be hoped that a        
somewhat longer flight would be         
obtained4 ,it was1 however1 very evident
 that1 although the correct balancing   
which would insure equilibrium for a few
 minutes might soon be attained1 the    
machine1 lacking a human intelligence to
 control it1 must be provided with some 
mechanism which would tend to restore   
the equilibrium1 the conditions of which
 must necessarily change in a machine   
depending on the air for its support4   
,in order to see what could be done in  
this direction1 it was1 therefore1      
decided to return immediately to        
,washington with the machines and make  
some minor changes in them before       
attempting further flights4  ,by the end
 of ,may1 ,nos4 #d and #e were again in 
readiness for a trial1 and the mechanics
 were accordingly sent to ,quantico to  
complete preparations for the tests4    
,during ,may ,mr4 ,a4 ,m4 ,herring1 who 

had been experimenting with model       
machines for several years1 was engaged 
for a few months as an assistant1 and he
 was immediately put in charge of the   
field trials of ,nos4 #d and #e1 which  
were now about to be made4 ,on ,june #f 
,mr4 ,langley1 accompanied by ,mr4      
,herring1 went to ,quantico1 and on     
,june #g1 at #e a4 m41 ,aerodrome ,no4  
#e was ready for trial1 but the wind was
 so high that nothing could be done4    
,the wind later diminished in intensity1
 but the house-boat had become stuck on 
the beach p#aje and it was impossible to
 make the launching apparatus point     
directly into the wind1 which was       
blowing from the rear of the boat4 ,an  
attempt was made to launch the aerodrome
 even with the wind blowing at its rear1
 but it was found impossible to make the
 fires burn and the test was accordingly
 postponed4 ,later in the afternoon the 
house-boat was floated and the          
preparations for a test were immediately
 completed4 ,at #e4db p4 m4 the fires   

were lighted1 but the burners did not   
work properly and the proper steam      
pressure could not be obtained4 ,at     
#f4bj p4 m4 the fires were again        
lighted1 and at #f4bb the aerodrome was 
launched1 its midrod having an upward   
angle of #be degrees1 or more1 with the 
launching track4 ,the aerodrome moved   
off nearly horizontally1 but seemed to  
be very sluggish in its movement and    
fell in the water about seventy feet    
from the boat1 after having been in the 
air only #d4h seconds4 ,the damage      
consisted of a broken propeller and a   
slight strain in the main frame1 the    
extent of which1 however1 was not       
immediately seen4  ,the steam pressure  
at the time of launching was #aaj       
pounds1 which was obviously             
insufficient4 ,the aerodrome had lifted 
fifty per cent of its weight on the     
pendulum1 and its sluggishness of       
movement seemed1 therefore1             
unaccountable even for this pressure4   
,it seemed probable1 however1 that the  

pressure ran down immediately after the 
machine was launched1 on account either 
of the use of the light-weight burners  
in place of the larger and heavier ones1
 or of the diminution of the air        
pressure in the gas tank4  ,at #g4ee the
 aerodrome was again launched1 and this 
time made a still shorter flight than   
before1 being in the air only three     
seconds4 ,a serious leak in the engine  
cylinder was1 however1 discovered just  
as the machine was launched1 and this   
probably accounted for the lack of      
power4  ,not only had the tests which   
have just been described indicated that 
there was a lack of power during flight1
 although previous pendulum tests had   
repeatedly shown lifts greater than     
fifty per cent1 but1 furthermore1 the   
wings themselves1 while appearing       
perfectly capable of supporting the     
aerodrome when viewed with the machine  
stationary1 were seen to flex to such an
 extent in flight that it seemed        
probable that much of the power was     

consumed in merely overcoming the head  
resistance of a large portion of the    
wings which had lost all lifting effect4
  ,during the fall and winter1 as       
recorded in ,chapters ,,vii and ,,viii1 
,aerodrome 8,new ,no4 #d10 which had    
been reconstructed during the summer1   
and which upon test was found radically 
weak1 was almost entirely rebuilt and   
afterwards known as ,no4 #f4 ,important 
changes were also made in ,no4 #e1 which
 greatly increased its strength and     
power4 ,the improvements1 however1 which
 contributed more than anything else to 
the marked success achieved in the next 
trial of the aerodromes1 were those     
which had to do with the nature and     
disposition of the sustaining surfaces  
and the means for securing equilibrium4 
p#ajf  ,it will be recalled that in the 
more recent trials the apparent causes  
of failure had been the inability to    
provide sufficiently rigid wings1 the   
great difficulty of properly adjusting  
the relative positions of the centers of

 pressure and gravity1 and the lack of  
any means of regaining equilibrium when 
the balance of the aerodrome had in any 
way been disturbed4 ,in the fall of     
#ahie1 accordingly1 it was finally      
decided to employ a second pair of wings
 equal in size to the first or leading  
pair4 ,this not only added greatly to   
the stability of the aerodrome1 but also
 made it possible1 without any          
alteration in the plan of the frame1 to 
bring the center of pressure into the   
proper position relative to the center  
of gravity4 ,in addition the plan of    
constructing the wings was modified by  
the introduction of a second main rib1  
which1 placed at approximately the      
center of pressure of the wings1 made   
them much stiffer1 both against bending 
and torsion4 ,the two pairs of wings now
 became the sole means of support1 and  
the tail which had hitherto been made to
 bear part of the weight of the         
aerodrome1 as well as assist in         
preserving the longitudinal equilibrium1

 was now intended to perform only the   
latter function4 ,it was placed in the  
rear of the wings and was combined with 
the vertical rudder4 ,further1 in       
adjusting it on the aerodrome1 it was   
set at a small negative angle and given 
a certain degree of elasticity1 as      
described above4 ,this device proved to 
be a most efficient means of maintaining
 and restoring the equilibrium1 when it 
was disturbed1 and its value was        
apparent in all future tests of the     
models4    #ahif  ,the important changes
 in the steam-driven models which had   
been begun in the previous fall1 and    
which in the case of ,no4 #d had been so
 extensive as to convert it into a new  
aerodrome1 ,no4 #f1 were continued      
during the early spring1 and it was not 
until the last of ,april that the models
 ,nos4 #e and #f were ready for actual  
test in free flight4  ,illustration3    
,,pl4 #ah  ,,house-,,boat ,,with        
,,overhead ,,launching ,,apparatus1     
#ahif  ,the condition of ,no4 #e1 which 

made the first successful flight1 is    
given in the data sheet for ,may #f1    
#ahif1 and its general form at this time
 may be seen in the photograph of ,may  
#aa1 ,plate #bg;,a4 ,although the       
changes described above1 as well as the 
modifications in the boilers and burners
 of both aerodromes had undoubtedly     
effected a great improvement in every   
detail of the machines1 the             
disappointments experienced in the      
preceding years prevented any great     
feeling of confidence that the trials   
which were now to be made would be      
entirely successful4 ,on ,may #d1       
however1 the two mechanics1 ,mr4 ,reed  
and ,mr4 ,maltby1 were sent down to     
,quantico with ,aerodromes ,nos4 #e and 
#f1 and ,mr4 ,langley1 accompanied by   
,dr4 ,graham ,bell1 who had been invited
 to witness the tests1 followed on the  
afternoon of the #eth4 ,on ,may #f the  
wind was so very high all the morning   
that a test was found impracticable4    
,during the forenoon1 however1 the wind 

gradually died down1 and by #a p4 m4 was
 blowing from six to ten miles an hour  
p#ajg from the northeast4 ,at #a4aj p4  
m4 ,aerodrome ,no4 #f was launched1 but 
the guy-wire uniting the wings having   
apparently caught on one of the fixed   
wooden strips which held the wings down1
 the left wing was broken before the    
aerodrome was really launched1 and the  
result was that the machine slowly      
settled down in the water by the boat1  
breaking the propellers and slightly    
injuring the ,pnaud tail4  ,after       
removing ,no4 #f from the water1 ,no4 #e
 was placed on the launching car and    
immediately prepared for a test4 ,at    
#c4je p4 m4 it was launched at a steam  
pressure of #aej pounds and started     
directly ahead into the gentle breeze   
which was then blowing4 ,the height of  
the launching track above the water was 
about twenty feet4 ,immediately after   
leaving the launching track1 the        
aerodrome slowly descended three or four
 feet1 but immediately began to rise1   

its midrod pointing upward at an        
increasing angle until it made about ten
 degrees with the horizon and then      
remained remarkably constant at this    
angle through the flight4 ,shortly after
 leaving the launching track the        
aerodrome began to circle to the right  
and moved around with great steadiness1 
traversing a spiral path1 as shown in   
the diagram 7,plate #ai74 ,from an      
inspection of the diagram it will be    
noticed that the aerodrome made two     
complete turns and started on the third 
one4 ,during the first two turns the    
machine was constantly and steadily     
ascending1 and at the end of the second 
turn it had reached a height variously  
estimated by the different observers at 
from #gj to #ajj feet4 ,when at this    
height1 and after the lapse of one      
minute and twenty seconds1 the          
propellers were seen to be moving       
perceptibly slower and the machine began
 to descend slowly1 at the same time    
moving forward and changing the angle of

 inclination of the midrod until the bow
 pointed slightly downward4 ,it finally 
touched the water to the south of the   
house-boat at the position shown1 the   
time the machine was in the air having  
been one minute and thirty seconds from 
the moment of launching4 ,the distance  
actually traversed1 as estimated by     
plotting its curved path on the         
coast-survey chart and then measuring   
this path1 was approximately #ccjj feet1
 which is the mean of three independent 
estimates4 ,this estimate of the        
distance was checked by noting the      
number of revolutions of the propellers 
as recorded by the revolution counter1  
which was set in motion at the moment   
the machine was launched4 ,on the       
assumption that the slip of the         
propellers was not greater than fifty   
per cent1 the #aaff revolutions as shown
 by the counter would indicate a        
distance travelled of #bdcj feet4 ,as it
 was felt very certain that the slip of 
the propellers could not have amounted  

to as much as fifty per cent1 it seemed 
a conservative estimate to place the    
length of flight at #cjjj feet1 which   
would mean a rate of travel of between  
#bj and #be miles an hour4 ,the circular
 path traversed by the aerodrome was    
accounted for by the fact that the      
guy-wires on one of the wings had not   
been tightened up properly1 thus causing
 a difference in the lifting effect of  
the two sides4 p#ajh  ,the aerodrome was
 immediately recovered from the water   
and preparations made for a second test1
 the machine being launched again at    
#e4aj p4 m4 at a steam pressure of #afj 
pounds4 ,the conditions were the same as
 at the first trial1 except that the    
wind had changed from north to south and
 was perhaps of less velocity than      
before4 ,the path traversed by the      
aerodrome in this second trial was      
almost a duplicate of the previous one1 
except that on account of the change in 
the direction of the wind the machine   
was launched in the opposite direction4 

,in tightening up the guy-wires1 which  
had not been properly adjusted in the   
previous test1 they were probably       
tightened somewhat too much1 since in   
this second test the aerodrome circled  
towards the left1 whereas in the first  
flight it had circled towards the right4
 ,the aerodrome made three complete     
turns1 rising to a height of            
approximately sixty feet with its midrod
 inclined to the horizon at a slightly  
greater angle than before4 ,the         
propellers again ceased turning while   
the machine was high in the air and it  
glided forward and downward and finally 
settled on the water after having been  
in the air one minute and thirty-one    
seconds4 ,the distance travelled was    
estimated as before1 by plotting the    
path on the coast-survey chart1 and was 
found to be #bcjj feet4  ,during these  
flights several photographs were secured
 of the machine while it was actually in
 the air1 some of the pictures being    
taken by ,dr4 ,bell and others by ,mr4  

,f4 ,e4 ,fowle4 ,the clearest of these  
are shown in ,plates #bj1 #ba1 and #bb4 
,just what these flights meant to ,mr4  
,langley can be readily understood4     
,they meant success6 ,for the first time
 in the history of the world a device   
produced by man had actually flown      
through the air1 and had preserved its  
equilibrium without the aid of a guiding
 human intelligence4 ,not only had this 
device flown1 but it had been given a   
second trial and had again flown and had
 demonstrated that the result obtained  
in the first test was no mere accident4 
,shortly after returning to ,washington1
 ,mr4 ,langley left for ,europe1 but    
before doing so he gave instructions to 
the workmen to remedy the small         
weaknesses and defects which had been   
found in ,aerodrome ,no4 #f1 and to have
 both aerodromes ready for trial before 
his return in the fall4  ,illustration3 
,,pl4 #ai  ,,path ,,of ,,aerodrome      
,,flights1 ,,may #f ,,and ,,november    
#bh1 #ahif1 ,,near ,,quantico1 ,,va41   

,,on ,,the ,,potomac ,,river            
,illustration3 ,,pl4 #bj                
,,instantaneous ,,photograph ,,of ,,the 
,,aerodrome ,,at ,,the ,,moment ,,after 
,,launching ,,in ,,its ,,flight ,,at    
,,quantico ,,on ,,the ,,potomac ,,river1
 ,,may #f1 #ahif4 ,,enlarged ,,ten      
,,times  ,illustration3 ,,pl4 #ba       
,,instantaneous ,,photograph ,,of ,,the 
,,aerodrome ,,at ,a ,,distance ,,in     
,,the ,,air ,,during ,,its ,,flight ,,at
 ,,quantico ,,on ,,the ,,potomac        
,,river1 ,,may #f1 #ahif4 ,,enlarged    
,,ten ,,times  ,illustration3 ,,pl4 #bb 
,,instantaneous ,,photograph ,,of ,,the 
,,aerodrome ,,at ,a ,,distance ,,in     
,,the ,,air ,,during ,,its ,,flight ,,at
 ,,quantico ,,on ,,the ,,potomac        
,,river1 ,,may #f1 #ahif4 ,,enlarged    
,,ten ,,times  ,illustration3 ,,pl4 #bc 
,,overhead ,,launching ,,apparatus      
,illustration3 ,,pl4 #bd  ,,overhead    
,,launching ,,apparatus  ,after         
returning in the fall1 ,mr4 ,langley    
again had ,aerodromes ,nos4 #e and #f   

taken down to ,quantico for trial1 and  
this time had as his invited guest ,mr4 
,frank ,g4 ,carpenter4 ,on ,november #bg
 a test was made of ,aerodrome ,no4 #f1 
the general disposition of which at this
 time may be learned from the           
description in ,chapter ,x1 and the     
photographs in ,plates #bi;,a1 #bi;,b4  
,the model was launched at #d4be p4 m4  
with a steam pressure of #abe pounds4   
,the aerodrome went nearly horizontally 
against the wind1 and descended into the
 water in six and a quarter seconds at a
 distance of perhaps #ajj yards4 ,after 
the machine had been recovered from the 
water1 it was found that a pin had      
broken in the synchronizing rod which   
connects the two propeller shafts       
together1 and that the counter1 which   
showed #die revolutions of the          
propellers1 had been caused to register 
p#aji inaccurately on this account4 ,the
 balancing of ,aerodrome ,no4 #f had    
been made the same as that of ,no4 #e1  
but in ,no4 #f the line of thrust was   

twelve centimetres higher1 and this     
fact1 which had not been taken into     
account in determining the proper       
balancing for ,no4 #f1 seemed to be     
sufficient cause for the aerodrome      
coming down into the water so soon after
 being launched4 ,darkness had descended
 before the aerodrome could be recovered
 and prepared for a second trial4 ,on   
the next day1 ,november #bh1 a high wind
 prevailed in the morning1 but in the   
afternoon it became comparatively calm1 
and ,no4 #f was launched at #d4bj p4 m4 
under the same conditions as on the     
preceding day1 except that the float1   
which weighed #bge grammes1 was moved   
back from the bowsprit eighty           
centimetres in order to make the machine
 lighter in front4 ,the aerodrome was   
launched at a steam pressure of not much
 over #ajj pounds1 the air draft for the
 burners being temporarily bad4 ,the    
midrod made an angle of approximately   
three degrees with the horizontal4 ,on  
account of a slight rain1 which had     

occurred just before the machine was    
launched1 the wings were wet and the    
weight of the entire aerodrome was      
doubtless as much as twelve kilos4      
,immediately on being launched the      
aerodrome started directly ahead in a   
gentle south wind1 moving horizontally  
and slowly turning to the right and     
appearing to approach dangerously near  
to some thick woods on the west shore4  
,however1 it fortunately continued      
turning until it pointed directly up the
 beach with the wind in the rear4 ,it   
then moved more rapidly forward1 dipped 
and rose but once1 and this very        
slightly1 and continued its remarkable  
horizontal flight1 varying not more than
 two yards out of a horizontal course1  
and this only for a moment1 until it    
finally descended into the bay at a     
point nearly in a line between the      
house-boat and the railroad station at  
,quantico4 ,upon being recovered1 it was
 found to be absolutely uninjured1 and  
another flight would have been made with

 it immediately but darkness had        
descended4 ,the time of flight1 as      
determined independently by two         
stop-watches1 was one minute and        
forty-five seconds4 ,the number of      
revolutions of the propellers was #bhja1
 or at the rate of #afjj ,r4 ,p4 ,m41   
which1 with an allowance of fifty per   
cent slip1 should have carried the      
aerodrome a distance of #dfjj feet in   
one and three-quarter minutes4 ,while   
the distance from the house-boat in a   
straight line to the point at which the 
aerodrome descended was only about #afjj
 feet1 yet it was estimated by those    
present that this straight-line distance
 was certainly not greater than         
one-third the total length of the path  
traversed1 which would mean a distance  
of something like #dhjj feet4 ,the      
length of the course1 as plotted on the 
coast-survey map and afterwards         
measured1 was #dbjj feet1 and it1       
therefore1 seemed safe to say that the  
total distance travelled was about      

three-quarters of a mile1 and the speed 
was1 therefore1 about thirty miles an   
hour4   p#aaj    ,,chapter ,x           
,,description ,,of ,,the ,,launching    
,,apparatus ,,and ,,of  ,,aerodromes    
,nos4 #e ,,and #f  ,reference has       
already been made to the development of 
the 8cast-off0 apparatus that was used  
at ,quantico for launching the          
aerodrome4 ,an initial velocity is      
indispensable1 and after long experiment
 with other forms which proved failures1
 an apparatus was designed by me1 which 
gave a sufficient linear velocity in any
 direction4 ,it had1 moreover1 been     
found that1 when the aerodrome was      
attached to any apparatus upon the roof 
of the house-boat1 such slight changes  
in the direction and intensity of the   
wind as would ordinarily pass           
unperceived1 would tend to distort or   
loosen it from its support1 so that only
 the most rigid of fastenings at three  
independent bearing points were of any  
use in holding it1 while the wings must 

be separately fastened down1 lest they  
should be torn from their sockets4 ,it  
was1 then1 necessary to be able to      
fasten the aerodrome very firmly to the 
cast-off apparatus1 to start it upon its
 journey in any direction with an       
initial linear velocity that should     
equal its soaring speed1 and to release 
it simultaneously at all points at the  
very same instant1 while at the same    
time the points of contact of the       
launching device1 to which it had just  
been fastened1 were themselves drawn up 
out of the way of the passing propellers
 and guys4  ,all these requirements and 
others were met by the apparatus finally
 adopted1 which is shown in ,plates #bc 
and #bd4 ,it consists of a strong timber
 frame-work1 carrying a track1          
consisting of two flat iron rails set on
 edge1 upon which runs the launching    
car1 suspended from two small wheels on 
each side4 ,at the front end of the     
frame there are two cylindrical air     
buffers to receive the buffing pistons  

and thus stop the car after the         
aerodrome has been released4 ,the car is
 drawn to the rear end of the track and 
held by the bell-crank lever ,a 7,plate 
#bc74 ,the contact points ,,bb and ,c   
are turned down and the clutch-hook ,d  
set over the clutch-post ,k4 ,the       
aerodrome is thus held firmly up against
 the three points ,,bb and ,c by the    
clutch ,d1 and a distortion from its    
proper position rendered impossible4    
,all these points are thrown up out of  
the way of the projecting portions of   
the aerodrome at the instant of release4
 ,this result is accomplished as        
follows3 when the car has reached the   
proper point in its forward course1 the 
cam ,e1 which is hinged at #a1 is       
depressed by a roller fixed to the      
framework of the device4 ,in this motion
 it pushes down the adjustable          
connections ,,ff1 which are attached at 
their lower ends to the bell-crank arms 
,,gg1 which turn about a central pivot  
at #b4 ,thus the downward movement of   

the connections ,,ff opens the jaws of  
the p#aaa clutch ,d4 ,while the clutch  
,d is rigidly attached to ,g to prevent 
transverse movement1 it is hinged to the
 latter at #c so that it can fold in a  
longitudinal direction4 ,screwed to the 
clutch ,d is a narrow plate #d1 which1  
when the clutch is closed1 is behind the
 lug #e1 thus preventing any turning    
about the hinge #c4  ,but when the arms 
of ,g and the jaws of the clamp are     
thrown out by the depression of ,f1 the 
plate #d is moved out from behind the   
lug #e and the clamp is free to fold to 
the front4 ,the strut1 hinged at #f1 is 
under a constant tension from the spring
 #g to fold up1 and is prevented from   
doing so only by the connections #h1 by 
which it is held down until the release 
of the plate #d from behind the lug #e1 
when the spring snaps them instantly up 
and out of the way4  ,as the struts ,,bb
 have no fixed connection with the      
aerodrome1 they are released by the     
relaxation in the rigidity of the other 

connections and are thrown up by their  
spring #i and held in that position by  
the clip #aj catching beneath the upper 
cross-piece4  ,the power for the        
propulsion of the car is obtained by    
means of from one to nine helical       
springs working under tension1 and      
multiplying their own motion four times 
by means of a movable two-sheave pulley1
 as shown in the drawing4               
,,description ,,of ,,aerodrome ,,no4 #e 
,when the details of the aerodrome1     
whose description is to follow1 are     
considered from the standpoint of the   
engineer accustomed to make every       
provision against breakage and accident 
and to allow an ample factor of safety  
in every part1 they will be found far   
too weak to stand the stresses that were
 put upon them4 ,but it must be         
remembered that in designing this       
machine1 all precedent had to be laid   
aside and new rules1 adapted to the new 
conditions1 applied4 ,it was absolutely 
necessary1 in order to insure success1  

that the weight should be cut down to   
the lowest possible point1 and when this
 was reached it was found that the      
factor of safety had been almost        
entirely done away with1 and that the   
stresses applied and the strength of    
material were almost equal4  ,the same  
observation holds true of the boilers1  
aeolipile1 and engines1 when regarded   
from the point of view of the economical
 generation and use of steam4 ,it was   
fully recognized that the waste of heat 
in the coil boilers was excessive1 but  
as it was necessary that there should be
 an exceedingly rapid generation of     
steam with a small heating surface1 this
 was regarded as inevitable4  ,in the   
engine the three points aimed at in the 
design were lightness1 strength and     
power1 but lightness above all1 and     
necessarily in a degree which long      
seemed incompatible with strength4 ,no  
attempt was made to secure the          
requirements of modern steam-engine     
construction1 either in the distribution

 of the steam or the protection of the  
cylinder against the radiation of heat  
by a suitable jacketing4 ,the very      
narrow limits of weight permissible     
required that the p#aab barrel of the   
cylinder should be as thin as possible1 
that no protective jacketing should be  
used1 and that the valve motion should  
be of the simplest description4 ,to     
obtaining the greatest lightness        
consistent with indispensable power1    
everything else was subordinated2 and   
hence1 all expectation of ordinary      
economical efficiency had to be         
abandoned at the outset4  ,it was only  
after long trials in other directions   
that ,mr4 ,langley introduced the       
aeolipile device1 which for the first   
time provided sufficient heat4 ,even in 
the aeolipile1 however1 is was apparent 
that nothing short of the most complete 
combustion accompanied by the highest   
possible temperature of the flame would 
be sufficient for the extreme demand4   
,to secure this result under all        

conditions of wind and weather1 with the
 aerodrome at rest and in motion1       
required the long series of experiments 
that are given in another chapter4 ,in  
respect to the generation of heat1 then1
 it is probable that it would be        
difficult to exceed the performance of  
the final type of burner in practical   
work1 but in the utilization of this    
heat in the boiler1 as well as in the   
utilization of the steam there          
generated1 the waste was so great as to 
be prohibitive under ordinary           
conditions4 ,but this was not ordinary  
work1 and the simplest protection       
against radiation from boiler1          
separator1 and engine could not well be 
used4  ,the framework of the aerodrome  
is made of thin steel tubes1 the main or
 midrod extending the whole length of   
the machine and carrying the attachments
 to which the wings are fastened4       
,suspended from this midrod by rigid    
connections is a skeleton hull of steel 
tubing1 shaped somewhat like the        

framework of a boat1 from which1        
directly abeam of the engines1 arms are 
run out like the outriggers of a rowboat
 for carrying the propellers4 ,within   
this central hull are placed the        
aeolipile1 the boiler1 and the engine1  
which with their auxiliary parts1 the   
pump and the separator1 constitute the  
entire power-generating apparatus4  ,the
 aeolipile consists of four essential   
parts3 the spherical air chamber        
containing the supply of compressed air 
by which the gasoline in the reservoir  
tank is forced into the burner2 the     
reservoir tank containing the gasoline  
that is to be used as a fuel2 the gas   
generator wherein the liquid gasoline is
 heated and converted into gas2 and the 
burners where it is finally utilized to 
heat the boilers4  ,the air chamber ,d1 
,plate #be1 is a spherical vessel #abj  
mm4 in diameter1 located at the extreme 
front end of the hull4 ,it is made of   
copper #j4be mm4 thick and has two      
openings4 ,the front opening has a      

copper pipe #a cm4 outside diameter1 to 
which the air pump for charging the     
chamber is connected4 ,from the back a  
copper pipe #e mm4 outside diameter     
extends to the top of the gasoline      
reservoir4  ,illustration3 ,,pl4 #be    
,,sideview ,,of ,,steel ,,frame ,,of    
,,aerodrome ,,no4 #e ,,suspended ,,from 
,,launching-,,car1 ,,october #bd1 #ahif 
,this reservoir1 shown at ,i1 ,plate    
#be1 is also a light1 hollow sphere #abj
 mm4 in diameter2 both this and the air 
chamber being made by soldering         
hemispheres p#aac of copper together at 
their circumferences4 ,there are three  
openings in the reservoir tank2 two at  
the top and one at the bottom4 ,one of  
those at the top serves for the         
admission of the #e-mm4 pipe bringing   
compressed air from the air chamber2 the
 other is connected with a pipe #a cm4  
in diameter1 through which gasoline is  
supplied to the tank1 and which is      
closed by a simple plug at the top4 ,the
 hole in the bottom serves as the outlet

 for the gasoline to the burners4 ,close
 to the bottom of the tank there is     
placed a small needle valve1 which      
serves to regulate the flow of oil1 for1
 were the pipe left open1 the compressed
 air would force the oil out with such  
rapidity that the burners would be      
flooded and the intensity of the flame  
impaired4 ,the construction of this     
valve is clearly shown in ,plate #bf;,a4
 ,it consists of a brass shell having   
one end 7a7 soldered to the bottom of   
the tank4 ,the needle enters through a  
stuffing box whose gland is held by two 
small screws4 ,the stem of the needle is
 threaded and engages in a thread cut in
 the body of the casting and is operated
 by a fine wire on the outside4 ,it will
 readily be seen that this device       
affords a means of making a very        
accurate adjustment of the flow of the  
liquid to the burners4  ,after leaving  
the needle valve the gasoline flows     
along the pipe ,s1 ,plate #be1 until it 
reaches the evaporating coil1 ,n4 ,in   

order to subject the oil to as large a  
heating surface as possible1 in         
comparison with the sectional area      
through which it is flowing1 the pipe1  
which left the needle valve with a      
diameter of #f mm4 soon contracted to #e
 mm41 is here flattened to a width of #g
 mm4 and a thickness of #b mm4 ,there   
are seven complete turns of this        
flattened tubing coiled to an outside   
diameter of #cj mm4 ,at the end of the  
seventh coil the pipe is enlarged to a  
diameter of #a cm4 and two coils of this
 size are added1 the inside diameter    
being the same as that of the flattened 
coil4 ,this enlarged portion serves as a
 sort of expansion chamber for the      
complete gasification of the gasoline1  
which is then led back through a turn of
 the enlarged pipe1 beneath the coils   
and to the front4 ,at the front end of  
the coil a small branch is led off1     
forming a 8bleeder10 which takes        
sufficient gas to supply the burner by  
which the coil is heated1 the products  

of whose combustion pass into and       
between the coils of the boiler like    
those of the regular heating burners4   
,the gas pipe rises in front of the coil
 and by a ,t connection branches to the 
two burners that are placed in front of 
the coils of the boiler4 ,these burner  
pipes are #e mm4 in diameter and enter  
sheet-iron hoods forming regular burners
 of the ,bunsen type1 which are fully   
shown in all their details in the       
accompanying engraving1 ,plate #bf4 ,the
 pipe is plugged at the end1 and a hole 
#j4i mm4 in diameter drilled for the    
nipple of the burner in front of the    
coil where the water first enters from  
the separator1 and #j4he mm4 for the one
 in front of the return coil4 ,the face 
of the burner shell stands exactly      
central with and #da mm4 in front of the
 coils4#ce p#aad  ,this constitutes the 
heat-generating portion of the machine1 
and with it it is probable that a flame 
of as high a temperature is produced as 
can be reached1 with the fuel used1 by  

any practical device4  ,the boiler or   
steam-generating apparatus may be said  
to consist of three parts3 the          
separator1 the circulating pumps1 and   
the generating coils4  ,the separator   
7,m in ,plate #be7 is a device which has
 attained its present form after a long 
course of development4 ,as at present   
constructed1 it is formed of a hollow   
sphere #aij mm4 in diameter and is      
located as nearly as possible over the  
center of gravity of the whole          
apparatus4 ,it serves the double purpose
 of water reservoir and steam drum1 and 
is called a 8separator0 on account of   
the function which it performs of       
separating the water from the steam as  
it enters from the coils4 ,there is a   
straight vertical pipe #aj mm4 in       
diameter rising from the top of the     
sphere and fastened to the right-hand   
side of the midrod4 ,this is used for   
filling the separator with water4 ,upon 
the other side of the midrod there is a 
small steam dome #db mm4 in diameter    

with a semi-spherical top rising to a   
height of #gj mm4 above the top of the  
sphere4 ,from this dome two steam pipes 
are led off1 one to the engine and the  
other to the steam gauge4  ,as already  
stated elsewhere1 it was found in the   
experiments with the coil boiler that an
 artificial forcing of the circulation  
of the water was a necessity1 as the    
natural circulation was too slow to be  
of any service4 ,accordingly1 but only  
after numerous devices involving less   
weight had failed1 a pump driven from   
the engine shaft was designed and used4 
,in the early experiments various types 
of pumps were tried in which the valves 
were opened and closed automatically by 
the pressure of the water4 ,it was      
found1 however1 that with the mixture of
 steam and water to be handled1 the     
valves could not be depended upon to    
open and close properly at the high     
speeds at which is was necessary to run 
the engine4 ,in ,aerodrome ,no4 #e1     
therefore1 a double-acting pump with a  

mechanically operated valve was used4   
,the pump1 shown in detail in ,plate    
#bf;,a1 is driven from a shaft connected
 with the main engine shaft by a spur   
gear and pinion1 which rotates at half  
the speed of the engine shaft4 ,the pump
 itself consists of two barrels1 the    
main barrel having a diameter of #bc mm4
 with a piston stroke of #bj mm4 ,the   
outer shell of the barrel is made of    
aluminum bronze and is lined with a     
cast-iron bushing #a4be mm4 in          
thickness4 ,the piston has a length of  
#ad mm4 and is formed of an aluminum    
disc and center1 having a follower plate
 of the same material with two cast-iron
 split rings sprung in4 ,the water is   
received into and delivered from the    
valve cylinder1 which is #ah mm4 in     
diameter and also lined with a cast-iron
 bushing #a4be mm4 thick4 ,the aluminum 
bronze shells of both cylinders are     
#j4ge mm4 in thickness4 ,the valve is a 
simple piston valve #ce mm4 long with   
bearing faces #d mm4 long at each end4  

,the water is taken from the bottom of  
the separator and led to the center of  
the valve chest of the pump by a copper 
pipe #a cm4 outside diameter4 ,the ports
 p#aae leading from the valve to the    
main cylinder are #c mm4 wide and #cd   
mm4 apart over their openings4 ,it will 
thus be seen that when the valve is in  
its central position1 as it should be at
 the beginning of the piston stroke1    
both ports are covered with a lap of    
#j4e mm4 inside and out1 so that the    
valve has to move #j4e mm4 before       
suction or discharge can take place4 ,as
 the valve is moving most rapidly at    
this point1 it opens and both functions 
begin before the piston has advanced    
perceptibly4 ,the delivery is made at   
the ends of the valve cylinder through  
two copper pipes of #a cm4 diameter that
 unite into a single pipe before        
reaching the boiler4 ,the throw of the  
valve is #ad mm4 so that the ports are  
uncovered and held wide open for the    
greater portion of the stroke of the    

piston1 and begin to close only when the
 latter approaches the end of its       
stroke4 ,in this way perfect freedom is 
given to the flow of the water and all  
choking is avoided4 ,as the engine has  
been run at a speed of more than #fhh   
revolutions per minute1 the pump must   
have made at least #cdd strokes in the  
same time1 thus displacing #aff4b cc4 of
 water4 ,the diameter of the piston rod 
and valve stem is #c mm4 and they pass  
through stuffing boxes with glands of   
the ordinary type for packing4 ,this    
pump served its purpose admirably1 and  
with it it was possible to maintain a   
continuous circulation of water through 
the two coils of the boiler4  ,the third
 element in the steam-generating system 
is the boiler proper#cf 7,plates #be and
 #bf;,a71 which consists of two coils of
 copper pipe1 having an outside diameter
 of #aj mm41 each coil being formed of  
#ba turns each #ge mm4 in diameter upon 
the outside and spaced #g4e mm4 apart1  
so that the total axial length of each  

coil is #cf cm4  ,the water is delivered
 to the front end of the right-hand     
coil1 and1 first passing through this1  
crosses over at the rear of the boiler  
to the left-hand coil1 returning through
 it to the front whence it is led to and
 delivered into the top of the          
separator4 ,here the steam and water are
 separated1 the former going through the
 separator and thence to the engine1    
while the unevaporated water falls to   
the bottom to be again taken into the   
pumps and sent through the coils4  ,in  
order that the draft of the burner and  
the gases of combustion might not be    
dissipated1 it was necessary to sheathe 
the boiler4 ,the method of doing this is
 shown in ,plate #be4 ,it will be seen  
that the front half of the boiler is    
wrapped in a sheet of mica through which
 the coils can be faintly seen4 ,this1  
in turn1 is held at the extreme front   
end by a strip of thin sheet-iron1 ,o4  
,over the back end the stack ,q1 made of
 very thin sheet-iron1 is slipped4 ,this

 has an oblong cross-section at the     
lower end where it goes over the boiler2
 it is provided with a hole through     
which the midrod passes1 and terminates 
in a circular opening of about #aj cm4  
diameter4 p#aaf  ,the engine1 which is  
clearly shown in the dimensional        
drawing1 ,plate #bf;,b1 is of the plain 
slide-valve type1 using a piston valve  
and solid piston1 without packing rings4
 ,the cylinder is formed of a piece of  
steel tubing #ce mm4 outside diameter1  
with flanges #dg mm4 in diameter and    
#b4be mm4 thick brazed to each end1 to  
which the cylinder heads are attached by
 small machine screws4 ,inside this     
cylinder is a thin cast-iron bushing in 
order to obtain a better rubbing surface
 for the piston4 ,the cross-head is a   
small piece of aluminum bronze1 running 
on round guides that also serve as      
cylinder braces4 ,there are also four   
hollow braces1 #e mm4 in diameter1      
running from the back cylinder head to a
 corrugated steel bed-plate1 that stands

 vertically and reaches from one side   
rod of the frame of the hull to the     
other1 and to which are bolted the      
bearings of the main shaft4 ,the        
connecting rod has the cross-section of 
a four-rayed star and drives a crank in 
the center of the shaft4 ,the following 
are some of the principal dimensions of 
the engine3                             
millimetres4 ,inside diameter of        
cylinder                                
#cc ,stroke of piston                   
#gj ,length of cylinder inside          
#hh ,length of piston                   
#aa ,clearance at each end              
#j4e ,diameter of piston rod            
#e ,length of cross-head                
#ag4e ,diameter of guides               
#d4e ,distance from center to center of 
guides                  #bf ,length of  
guides                                  
#aaj ,length of wrist-pin bearing       
#h4e ,length of connecting rod          
#aej ,ratio of connecting rod to stroke 
#b-a_/g to #a ,length of crank pin      

#aj ,diameter of main shaft             
#h ,length of main bearings             
#be ,distance from center of cylinder to
 center of valve stem  #ce ,length of   
valve                                   
#gb ,width of ports                     
#b ,outside lap of valve                
#d ,inside lap of valve                 
#c ,lead of valve                       
#j ,travel of valve                     
#ac ,cut-off from beginning of stroke   
#eg ,exhaust opens                      
,end of stroke ,exhaust closes on return
 stroke                           #dh   
,diameter of valve stem                 
#d4e ,diameter of eccentric             
#cf ,width of eccentric                 
#d ,width of crank arm                  
#d  ,the weights were nearly as follows3
                                        
grammes4 ,engine                        
#dfd ,pump and pump shafts              
#bca ,gasoline tank and valves          
#agh ,burners                           
#cfj ,boilers1 frames holding boilers1  

and mica covers over boilers  #fea      
,separator1 steam gauge and pipe for    
engine                     #edj ,exhaust
 pipe                                   
#adc ,smoke stack                       
#cdb               ,in all1 #biji       
grammes1 or #f4d pounds4  ,illustration3
 ,,pl4 #bf;,a  ,,dimensioned ,,drawing  
,,of ,,boiler ,,coils1 ,,burners1       
,,pump1 ,,needle ,,valve ,,and ,,thrust 
,,bearing  ,illustration3 ,,pl4 #bf;,b  
,,dimensioned ,,drawing ,,of ,,engine   
,,no4 #e  ,illustration3 ,,pl4 #bg;,a   
,,side ,,and ,,end ,,elevations ,,of    
,,aerodrome ,,no4 #e1 ,,may #aa1 #ahif  
,illustration3 ,,pl4 #bg;,b  ,,aerodrome
 ,,no4 #e ,,plan ,,view4 ,,october #bd1 
#ahif   p#aag  ,these weights are those 
determined in ,december1 #ahif1 when    
some slight changes had been made from  
the conditions existing at the time of  
the flight by this aerodrome on ,may #f4
 ,previous to that time1 with a pressure
 of #acj pounds1 between #a4a and #a4be 
horse-power was given on the ,prony     

brake4 ,at the actual time of flight the
 pressure was about #aae pounds1 and the
 actual power very near #a horse-power4 
,the valve stem was pivoted to the      
center of the valve partly because this 
was the lightest connection that could  
be made1 and partly to allow the valve  
perfect freedom of adjustment upon the  
seat4 ,many parts1 such as guides1      
braces1 crank-pins1 wrist-pin and shafts
 are hollow4 ,the steam is taken in at  
the front end of the steam chest1 and   
the exhaust taken out of the center1    
whence it is led back to the stack and  
by means of a forked exhaust pipe       
discharged in such a way as to assist   
the draught of each coil of the boilers4
 ,like the cylinder the steam chest is  
made of a piece of steel tubing1 #bj mm4
 diameter on the outside1 with an inside
 diameter of #ai mm41 and is fitted with
 a cast-iron bushing #j4e mm4 thick1    
making the inside diameter of the steam 
chest #ah mm4 ,it1 too1 has flanges     
brazed to the ends1 to which the heads  

are held by small machine screws4  ,the 
shaft for conveying the power to the    
propeller shafts extends across the     
machine from side to side2 it is hollow1
 being #h mm4 outside diameter1 with a  
hole #e mm4 diameter through the center4
  ,it is formed of five sections3 the   
middle section1 containing the crank1   
has a length of #aaj mm4 and is         
connected at either end1 by flanged     
couplings1 to lengths #cbj mm4 long1    
which are in turn extended by the end   
sections having a length of #bcj mm4 ,in
 addition to the four main bearings that
 are bolted to the pressed-steel        
bed-plate already mentioned1 there are  
two bearings on the outer framework on  
each side4 ,at the outer end of each    
shaft there is keyed thereto a bevel    
gear with an outside diameter of #bg mm4
 and having #bh teeth4 ,this gear meshes
 with one of #ce teeth upon a shaft at  
right angles to the main shaft and      
parallel to the axis of the aerodrome4  
,these two shafts1 one on either arm1   

serve to carry and transmit the power to
 the propellers4 ,they are #aib mm4     
long1 #h mm4 in diameter1 and are       
provided with three bearings that are   
brazed to a corrugated steel plate      
forming the end of the outrigger portion
 of the frame4 ,these shafts are also   
hollow1 having an axial hole #d mm4 in  
diameter drilled through them4 ,the     
propeller seat has a length of #dc mm4  
and the propeller is held in position by
 a collar #be mm4 in diameter at the    
front end1 from which there project two 
dowel-pins that fit into corresponding  
holes in the hubs of the propellers1    
which are held up against the collar by 
a smaller one screwed into the back end 
of the shaft4 ,the thrust of the collar 
is taken up by a pin screwed into the   
end of the forward box and acting as a  
step against which the shaft bears1 the 
arrangement being clearly shown by the  
accompanying drawing1 ,plate #bf;,a4    
p#aah  ,this1 then1 comprises the motive
 power equipment of the aerodrome1 and1 

to recapitulate1 it includes the        
storage1 automatic feeding and          
regulation of the fuel2 the storage1    
circulation and evaporation of the      
water2 the engine to convert the        
expansive power of the steam into       
mechanical work2 and the shafting for   
the transmission of the energy developed
 by the engine to the propellers4  ,the 
propellers were made with the greatest  
care4 ,those used in the successful     
trials were #a metre in diameter1 with  
an actual axial pitch of #a4be metres4  
,they were made of white pine1 glued    
together in strips #g mm4 thick4 ,the   
hub had a length of #de mm4 and a       
thickness or diameter of #be mm4 ,at the
 outer edge the blade had a width of    
#cae mm4 and a thickness of #b mm4      
,these propellers were most accurately  
balanced and tested in every particular2
 each propeller blade was balanced in   
weight with its mate and the pitch      
measured at every point along the radius
 to insure its constancy2 finally the   

two propellers of the pair to be used   
together were balanced with each other  
so that there would be no disturbance in
 the equilibrium of the machine4 ,as    
will be noted from the foregoing        
description of the machinery1 the       
propellers ran in opposite directions1  
as they were made right- and left-hand  
screws4 ,the weight of each propeller   
was #cfb grammes4  ,we now turn again to
 take up the details of the construction
 of the framework by which this         
propelling machinery is carried4 ,the   
whole aerodrome1 as clearly shown in the
 photographs1 ,plates #bg;,a and #bg;,b1
 is built about and dependent from one  
main backbone or midrod1 which extends  
well forward of all of the machinery and
 aft beyond all other parts4 ,this rod1 
as well as all other portions of the    
framework1 is of steel tubing4 ,the     
midrod1 being largest1 is #bj mm outside
 diameter1 with a thickness of #j4e mm4 
,it is to this midrod that the wings are
 directly attached1 and from it the hull

 containing the machinery is suspended4 
,the plan outline of the hull skeleton  
is similar to that of the deck of a     
vessel4 ,the steel tubing1 #j4e mm4     
thick1 of which it is formed1 has an    
outside diameter of #ae mm4 from the    
front end to the cross-framing used to  
carry the propellers1 back of which the 
diameter is decreased to #aj mm4  ,the  
midrod makes a slight angle with this   
frame1 the vertical distance between the
 centers of the tubing being #gc mm4 at 
the front and #fg mm4 at the back4 ,the 
tube1 corresponding to the keel of a    
vessel1 is braced to the upper tubes by 
light ,u-shaped ribs and by two #h-mm4  
tubes forming a ,v brace on a line with 
the back end of the guides of the       
engine4 ,at the extreme front and back  
there is a direct vertical connection to
 the midrod4  ,the propeller shafts are 
#a4bc m4 from center to center1 and are 
carried on a special cross-framing1     
partaking1 as already stated1 of the    
character of an outrigger on a row-boat4

 7,see ,plate #bg;,b47 ,the rear rods1  
which are of #aj mm4 steel tubing1 start
 from the front end of the rear bearings
 of the propeller shaft and p#aai extend
 across from side to side4 ,the top rod 
is brazed to the side pieces of the hull
 and the bottom rod to the keel4 ,they  
are connected by a vertical strut of    
#h-mm4 tubing at a distance of #bfe mm4 
inside of each propeller shaft4 ,at the 
front end of the propeller shaft two    
more rods run across the frame4 ,the    
lower is similar and parallel to the    
back rod already described1 while the   
upper is bowed to the front1 as shown in
 the plan view of the frame 7,plate     
#cj74 ,in order to take the forward     
thrust of the propeller a second        
cross-brace is inserted1 which runs from
 the rear bearing of the propeller shaft
 to a point just in advance of the front
 head of the cylinder1 and is brazed to 
the two upper tubes of the cross-frame  
as well as to the upper tubes of the    
main framing of the hull4 ,the outer    

ends of the tubes of the cross-framing  
are brazed to a thin1 stamped steel     
plate which firmly binds them together1 
while at the same time it forms a base  
for attaching the bearings of the       
propeller shaft4 ,this end plate has a  
thickness of one millimetre4  ,in       
addition to the framing proper there are
 two guy-posts which fit into the       
sockets ,,cc1 and over which truss wires
 are drawn1 as shown in the side view in
 ,plate #bg;,a4 ,these posts have a     
length of #gcj mm4 from the lower edge  
of the socket1 and are capped at their  
lower extremity by a light steel ferrule
 whose outside diameter is #aj mm4      
,from the drawing of the wings of ,no4  
#e1 shown in ,plate #ag1 it will be seen
 that they are formed of two pine rods  
#ae mm4 in diameter at the inner ends1  
tapering to a half circle of the same   
diameter at the tips4 ,these rods are   
connected by eleven spruce ribs         
measuring #h mm4#c mm41 and curved1 as  
shown in the side elevation1 these1 in  

turn1 being covered by a light white    
silk drawn so tightly as to present a   
smooth1 even surface4 ,the total length 
of the wing is #b metres1 and the width 
over all is #hje mm4 ,vertical stiffness
 is obtained in the wings by a series of
 guy-wires1 which pass over light struts
 resting upon the main rods4 ,these main
 rods are inserted and held in the wing 
clamps ,a and ,b1 ,fig4 #af1 and make an
 angle of #aej with each other4 ,as is  
the case with all other essential       
details of the aerodrome1 a great deal  
of time and attention was given to the  
designing of the wing clamps before a   
satisfactory arrangement was secured4   
,to enable it to control the aerodrome  
in both directions1 the tail-rudder1    
,plate #bg;,a1 has both a horizontal and
 a vertical surface1 the approximate    
dimensions of which are1 length #aae cm4
 7#c4h feet71 maximum width #fd cm4     
7#b4a feet71 giving each quarter section
 an area of about #j4fd sq4 m4 7#f4i sq4
 ft474 ,it is given the proper angle and

 degree of elasticity in a vertical     
direction by the flat hickory spring1   
which fits into the clamp ,n1 and       
attaches the rudder to the frame4  ,the 
only other attachments of the aerodrome 
are the reel1 float1 and counter4 ,they 
have nothing whatever to do with the    
flying of the machine1 and are p#abj    
merely safety appliances to insure its  
recovery from the water4 ,the reel      
consists of a light spool on which a    
fine cord is wound1 one end of which is 
attached to a light float that detaches 
itself and lies upon the surface of the 
water when the machine sinks1 while the 
other end is fastened to the spool that 
goes down with the aerodrome4 ,the      
8float0 is a light copper vessel with   
conical ends which is firmly fastened to
 the midrod1 and which is intended to so
 lower the specific gravity of the whole
 machine that it will not sink4 ,the    
cylindrical portion of this float has a 
length of #bej mm4 and a diameter of    
#agj mm41 one cone having a length of   

#fe mm4 and the other and front one a   
length of #adj mm41 which makes the     
total length of the float #cge mm4 ,it  
is made of very thin copper1 and served 
in the successful trials not only as a  
float to sustain the machine on the     
surface of the water1 but also as a     
weight by which the center of gravity   
was so adjusted that flight was         
possible4  ,the counter records the     
number of revolutions of the propellers 
after launching4 ,it is a small dial    
counter1 reading to #aj1jjj1 with a     
special attachment which prevents any   
record being made of the revolutions of 
the propellers1 until the actual moment 
of launching1 when a piece on the       
launching apparatus throws the counter  
in gear at the instant that the         
aerodrome leaps into the air4           
,,description ,,of ,,aerodrome ,,no4 #f 
,aerodrome ,no4 #f1 it will be          
remembered1 was the outgrowth of a      
number of changes made in ,no4 #d during
 the fall of #ahie and the early part of

 #ahif4 ,in this reconstruction the aim 
was to lighten the whole machine on     
account of the smaller engines in either
 ,no4 #d or ,no4 #e4 ,the modifications 
from ,no4 #d were so radical and the    
differences that exist between ,nos4 #e 
and #f are so considerable as to demand 
careful attention4  ,as regards general 
appearance the frame of ,aerodrome ,no4 
#f resembles that of ,no4 #e in         
consisting of a single continuous midrod
 of steel tubing1 #bj mm4 in diameter1  
#j4e mm4 thick1 immediately beneath     
which the hull containing the machinery 
is situated4 ,in reconstructing the     
framework after the tests in ,january1  
#ahif1 had shown it to be dangerously   
weak1 especially against torsion1 it was
 decided to make the hull only strong   
enough to carry its contents and to     
attach it to the stronger midrod in such
 a way that all torsional strains would 
be taken up by it1 whereas in ,no4 #e   
the hull structure must bear a large    
proportion of such strains4 ,it was     

therefore built throughout of #h-mm4    
tubing1 #j4c mm4 thick1 and was rigidly 
attached to the midrod by braces at the 
front and rear1 and also at the         
cross-frame4 ,the hull was also made    
narrower 7except at the rear1 where it  
was widened to contain the boiler7 and  
shorter than the hull of ,no4 #e--;an   
advantageous change made possible by the
 fact that the engines were not         
contained in the hull1 but mounted on   
the transverse frame4  ,illustration3   
,,pl4 #bh  ,,steel ,,frame ,,of         
,,aerodrome ,,no4 #f1 ,,on ,,launching  
,,car   p#aba  ,in ,no4 #e1 as described
 above1 a single engine mounted at the  
front end of the hull communicated its  
power through transmission shafts and   
gearing to the propellers1 which were   
necessarily in the same plane4 ,this    
brought the line of thrust very nearly  
in the same plane as the center of      
gravity of the aerodrome1 a condition   
tending to promote instability of       
longitudinal equilibrium4 ,in ,no4 #f1  

however1 the use of two engines situated
 on the transverse frame and            
communicating their power directly to   
the propellers1 made it possible to     
raise the transverse frame #ab cm4 above
 the hull1 and thus raise the line of   
thrust to a position intermediate       
between the center of pressure and the  
center of gravity1 without materially   
affecting the latter4 ,as a result of   
this change ,aerodrome ,no4 #f was      
rendered much more stable and made      
steadier flights with fewer undulations 
than ,no4 #e4  ,the engines in use on   
,no4 #f were the small engines described
 above in connection with ,no4 #d4 ,the 
cylinders were of steel tubing #b4h cm4 
in diameter1 with a #e-;cm4 stroke1 each
 cylinder thus having a capacity of     
#cj4h cc4 ,they were lined with a thin  
cast-iron bushing and cast-iron rings   
were sprung in the piston head so as to 
give as smooth a rubbing surface and as 
perfect action as possible4 ,as in the  
engine of ,no4 #e a plain sliding valve 

of the piston type was used1 cut-off    
being approximately at one-half1 though 
the ports were so small that it was     
difficult to determine it with any great
 accuracy4 ,no packing was used1 but the
 parts were carefully ground so as to   
give a perfect fit4  ,these engines1 as 
is most clearly shown in ,plate #cj1    
were mounted symmetrically on either    
side of the cross-frame and were        
connected directly to the propeller     
shafts4 ,in order to insure that the    
propellers would run at the same rate1  
there was provided a synchronizing      
shaft1 ,t1 in ,plate #cj1 having on each
 end a bevel gear1 which intermeshed    
with similar gears on the propeller     
shafts4 ,steam for the cylinders was    
conveyed from the separator through the 
pipes ,,ll4  ,the steam-generating      
apparatus for ,no4 #f was exactly like  
that already described in connection    
with ,no4 #e1 the only difference being 
in the more compact arrangement in the  
case of ,no4 #f4 ,the relative location 

of the apparatus in the two models is   
clearly shown in ,plates #bh1 #bi;,b1   
and #cj1 the corresponding parts being  
similarly labeled1 so that a separate   
description for ,no4 #f is superfluous4 
,the wings used on ,no4 #f were somewhat
 smaller than those of ,no4 #e1 and     
differed from them in having the front  
mainrib bent to a quadrant at its outer 
extremity and continued as the outer rib
 of the wing4 ,the degree of curvature  
of the wings was also somewhat less1    
being one-eighteenth for ,no4 #f and    
one-twelfth for ,no4 #e4 ,the four wings
 were of the same size and had a total  
area of #ed sq4 ft4 ,on account of the  
shortened hull of ,no4 #f they were     
allowed a much greater range of         
adjustment1 which rendered it much      
easier to bring the ,,cp into the proper
 relative position to the ,,cg than was 
the ease with ,no4 #e4 p#abb  ,the      
,pnaud rudder for ,no4 #f was similar to
 that for ,no4 #e1 the two in fact being
 interchangeable1 and was similarly     

attached to the frame4 ,the reel1 float1
 counter1 and all other accessories were
 identical for the two machines4  ,to   
sum up the comparative features of these
 two successful steam-driven models3    
,aerodrome ,no4 #f was both lighter and 
frailer than ,no4 #e1 and required much 
more delicate adjustment1 but when the  
correct adjustments had been made its   
flying qualities were superior1 as      
regards both speed and stability4       
,illustration3 ,,pl4 #bi;,a  ,,plan     
,,view ,,of ,,aerodrome ,,no4 #f4       
,,october #bc1 #ahif  ,illustration3    
,,pl4 #bi;,b  ,,side ,,elevation ,,of   
,,aerodrome ,,no4 #f4 ,,october #bc1    
#ahif4  ,illustration3 ,,pl4 #cj  ,,plan
 ,,view ,,of ,,steel ,,frames ,,and     
,,power ,,plants ,,of ,,aerodromes      
,,nos4 #e1 #f  ,illustration3 ,,pl4 #ca 
,,details ,,of ,,aerodrome ,,no4 #e     
,,footnotes4  #b 8,experiments in       
,aerodynamics10 ,smithsonian            
,contributions to ,knowledge1 ,vol4 #bg1
 #ahia4  #c ,this chapter was written   

almost entirely by ,mr4 ,langley in     
#ahig4  #d #ahig4  #e ,in this          
statement1 of course1 no account is     
taken of the 8internal work of the      
wind40  #f ,ten years prior to #ahig4   
#g ,communication to the ,french        
,academy4 ,extract from the ,comptes    
,rendus of the ,sessions of the ,academy
 of ,sciences1 ,vol4 #abb1 ,session of  
,may #bf1 #ahif4   7,translation47   ,a 
,description of ,mechanical ,flight4 ,by
 ,s4 ,p4 ,langley4   ,in a communication
 which ,i addressed to the ,academy in  
,july1 #ahia1 ,i remarked that the      
results of experimental  investigation  
had shown the possibility of            
constructing  machines which could give 
such a horizontal velocity to  bodies   
resembling in shape inclined planes1 and
 more than  a thousand times heavier    
than air1 that these could be  sustained
 on this element4   ,while ,i have      
elsewhere remarked that surfaces other  
than  planes might give better results1 
and that absolutely  horizontal flight1 

which is so desirable in theory1 is     
hardly realizable in practice1 so far as
 ,i know there  has never been          
constructed1 up to the present time1 any
  heavy aerodrome1 or so-called         
flying-machine1 which can  keep itself  
freely in the air by its own force more 
than  a few seconds1 the difficulties   
encountered in absolutely  free flight  
being1 for many reasons1 immeasurably   
greater  than those experienced when the
 flight is controlled  by the body's    
pressing upward against a horizontal    
track1 or whirling-arm4 ,no one is      
unaware that many  experimenters have   
been engaged in trying to execute free  
mechanical flight1 and although the     
demonstration which ,i  furnished in    
#ahia 8,experiments in ,aerodynamics10  
#ahia  of its theoretical possibility   
with means then at our  disposition1    
seemed conclusive1 so long a time has   
elapsed  without practical results1 that
 it might be doubted  whether these     
theoretical conditions are to be        

realized4  ,i have thought it well1     
then1 to occupy myself with the         
construction of an aerodrome with which 
,i might put my  previous conclusions to
 the test of experiment4   ,the ,academy
 will1 perhaps1 find it interesting to  
read the  narrative given here by an    
eye-witness1 who is well known  to it4  
,i am led to present it not only by the 
request  with which he honors me1 but by
 the apprehension that my               
administrative duties may put a stop to 
these researches1  so that it seems to  
me advisable to announce the degree in  
which ,i have already succeeded1        
although this success be  not as        
complete as ,i should like to make it4  
,the experiments took place on a bay of 
the ,potomac ,river1  some distance     
below ,washington4 ,the aerodrome was   
built  chiefly of steel1 though lighter 
material entered into the  construction1
 so that its density as a whole was a   
little  below unity4 ,no gas whatever   
entered into the construction  of the   

machine1 and the absolute weight1       
independent  of fuel and water1 was     
about #aa kilos 7#bd pounds74 ,the      
width of the supporting surfaces was    
about #d metres 7#ac  feet71 and the    
power was furnished by an extremely     
light  engine of approximately one      
horse-power4 ,there was no  one to      
direct it on board1 and the means for   
keeping it  automatically in horizontal 
flight were not complete4 ,it  is       
important to remark that the small      
dimensions of the  machine did not allow
 it to include any apparatus for        
condensing the steam1 so that it could  
only carry water  enough for a very     
brief course--a drawback which would not
  be encountered in one of a larger     
construction4   ,it is also to be noted 
that the speed estimated by  ,mr4 ,bell 
was that obtained in a continuous       
ascending  flight1 and much less than   
would have been attained in a           
horizontal course4   ,on ,mechanical    
,flight4 ,letter of ,mr4 ,alexander     

,graham ,bell  to ,mr4 ,langley4        
,washington1 ,may #f1 #ahif4   ,i am    
quite aware that you are not desirous of
 publication  until you have attained   
more complete success in obtaining      
horizontal flight under an automatic    
direction1 but it  seems that what ,i   
have been privileged to see to-day marks
  such a great progress on everything   
ever before done in  this way1 that the 
news of it should be made public1 and   
,i am happy to give my own testimony on 
the results of two  trials which ,i have
 witnessed to-day by your invitation1   
hoping that you will kindly consent to  
making it known4   ,for the first trial1
 the apparatus1 chiefly constructed  of 
steel and driven by a steam engine1 was 
launched from  a boat at a height of    
about #bj feet from the water4 ,under   
the impulse of its engines alone1 it    
advanced against the  wind and while    
drifting little1 and slowly ascending   
with  a remarkably uniform motion1 it   
described curves of about  #ajj metres  

in diameter2 till at a height in the air
 which  ,i estimate at about #be metres 
7#hb feet71 the revolutions  of the     
screws ceased for want of steam1 as ,i  
understood1  and the apparatus descended
 gently and sank into the  water1 which 
it reached in a minute and a half from  
the  start4 ,it was not damaged1 and was
 immediately ready for  another flight4 
,in the second trial it repeated in     
nearly every respect  the action of the 
first1 and with an identical result4    
,it rose smoothly in great curves until 
it approached a  prominent wooded       
promontory1 which it crossed at a height
  of #h to #aj metres above the tops of 
the highest trees1  upon the exhaustion 
of the steam descending slowly into  the
 bay1 where it settled in a minute and  
thirty-one  seconds from the start4 ,you
 have an instantaneous  photograph of   
it1 which ,i took just after the launch4
 ,see  plates #bj1 #ba1 and #bb of      
present work4   ,from the extent of the 
curves which it described1 which  ,i    

estimated with other persons1 from      
measurements which  ,i took1 and from   
the number of revolutions of the        
propellers1 as recorded by the automatic
 counter which ,i  consulted1 ,i        
estimate the absolute length of each    
course  to be over half an ,english     
mile1 or1 more exactly a little  over   
#ijj metres 7#biec feet74   ,the        
duration of flight during the second    
trial was one  minute and thirty-one    
seconds1 and the average velocity       
between twenty and twenty-five miles an 
hour1 or1 let us  say #aj metres a      
second1 in a course which was constantly
  ascending4 ,i was extremely impressed 
by the easy regular  course of each     
trial1 and by the fact that the         
apparatus  descended each time with such
 smoothness and gentleness as  to render
 any jar or danger out of the question4 
,it seemed to me that no one could have 
witnessed these  experiments without    
being convinced that the possibility  of
 mechanical flight had been             

demonstrated4  #h ,it is desirable that 
the reader should be acquainted with the
 contents of this treatise1 and of      
another by me1 entitled 8,the ,internal 
,work of the ,wind10 both published by  
the ,smithsonian ,institution4 ,a       
knowledge of these works is not         
absolutely necessary1 but of advantage  
in connection with what follows4  #i    
8,experiments in ,aerodynamics10 p4     
#ajg4  #aj ,chapter ,,viii4  #aa ,his   
device for obtaining automatic          
equilibrium is found in connection with 
the description of his 8,aeroplane ,auto
 ,moteur10 in 8,l',aeronaute0 for       
,january1 #ahgb4  #ab ,i have never     
obtained so good a result as this with  
any rubber motor4 ,s4 ,p4 ,langley4  #ac
 ,one pound of twisted rubber appears1  
from my experiments1 to be capable of   
momentarily yielding nearly #fjj        
foot-pounds of energy1 but this effect  
is attained only by twisting it too far4
 ,it will be safer to take at most #cjj 
foot-pounds1 and as the strain must be  

taken up by a tube or frame weighing at 
least as much as the rubber1 we have    
approximately #j4jjia as the horse-power
 for one minute1 or #j4jia horse-power  
for six seconds as the maximum effect1  
in continuous work1 of a pound of       
twisted rubber strands4 ,the            
longitudinal pull of the rubber is much 
greater1 but it is difficult to employ  
it in this way for models1 owing to the 
great relative weight of the tube or    
frame needed to bear the bending strain4
 ,in either form1 rubber is far more    
effective for the weight than any steel 
spring 7see later chapter on ,available 
,motors74  #ad ,the aerodrome is        
sustained by the upward pressure of the 
air1 which must be replaceable by the   
resultant pressure at some particular   
point1 designated by ,,cp4  #ae ,see    
,century ,magazine1 ,october1 #ahia4    
#af ,subsequent observations indicate   
that the maximum velocity of horizontal 
flight must have been about #aj metres  
per second4  #ag ,observers following de

 ,lucy have long since called attention 
to the fact that as the scale of        
,nature's flying things increases1 the  
size of the sustaining surfaces         
diminishes relatively to the weight     
sustained4 ,m4 ,harting 7,aeronautical  
,society1 #ahgj7 has shown that the     
relation area_/weight is surprisingly   
constant when bats varying in weight as 
much as #bej times are the subject of   
the experiment1 and later observations  
by ,marey have not materially affected  
the statement4 ,as to the muscular power
 which ,nature has imparted with the    
greater or lesser weight1 this varies1  
decreasing very rapidly as the weight   
increases4 ,the same remark may be made 
apparently with at least approximate    
truth1 with regard to the soaring bird1 
and the important inference is that if  
there be any analogy between the bird   
and the aerodrome1 as the scale of the  
construction of the latter increases1 it
 may be reasonably anticipated that the 
size of the sustaining surfaces will    

relatively diminish rather than         
increase4 ,we may conveniently use ,m4  
,harting's formula in the form a        
n#bw#b_/c  l#b_/m#b where a  area in sq4
 cm41 w the weight in grammes1 l the    
length of the wing in cm41 n and m      
constants derived from observation4  #ah
 ,a singular fact connected with the    
stretching of rubber is that the        
extension is not only not directly      
proportional to the power producing it1 
but that up to a certain limit it       
increases more rapidly than the power1  
and after this the relation becomes for 
a time more nearly constant1 and after  
this again the extension becomes less   
and less in proportion4  ,in other      
words1 if a curve be constructed whose  
abscissae represent extensions1 and     
ordinates the corresponding weights1 it 
will show a reverse curvature1 one      
portion being concave toward the axis of
 abscissae1 the other convex4  #ai ,the 
following table taken from 8,experiments
 in ,aerodynamics10 p4 #ajg1 gives the  

data for soaring of #cjd4h inch planes1 
weight #ejj grammes4                    
----------------------------------------
---------------------------             
,weight with planes            ,soaring 
speed        ,work expended    of like  
form that    ,angle         ,v4         
per minute4     #a horse-power will     
with                                    
drive through the    horizon            
air at velocity ,v4   4                 
----------------------------------------
-----------------         ,metres       
,feet     ,kilogram- ,foot-   ,kilo-    
,pounds4         per second4per second4 
metres4 pounds4 grammes4                
----------------------------------------
------------------------    #de    #aa4b
       #cf4g       #ccf    #b1dcd       
#f4h        #ae       #cj     #aj4f     
#cd4h       #age    #a1bfh   #ac4j      
#bi       #ae     #aa4b       #cf4g     
#hf      #fbc   #bf4e        #eh        
#aj     #ab4d       #dj4g        #fe    
#dgd   #cd4h        #gg        #e       

#ae4b       #di4h        #da      #big  
#ee4e       #abb        #b     #bj4j    
#fe4f        #bd      #agd   #ie4j      
#bji                                    
----------------------------------------
------------------------  ,the relations
 shown in the above table hold true only
 in case of planes supporting about #a4a
 pounds to each square foot of          
sustaining area4 ,for a different       
proportion of area to weight1 other     
conditions would obtain4  #bj ,this     
pressure per unit of area varies with   
the area itself1 but in a degree which  
is negligible for our immediate purpose4
  #ba ,see 8,internal ,work of the      
,wind02 also ,revue de ,l',aeronautique1
 #c;e ,livraison1 #ahic4  #bb ,more     
recent experiments under my direction by
 ,mr4 ,huffaker give similar results1   
but confirm my earlier and cruder       
observations that the curve1 used alone1
 for small angles1 is much more unstable
 than the plane4  #bc ,as stated in the 
,preface1 ,part ,,iii has not yet been  

prepared for publication4  #bd          
,according to ,wellner 78,zeitschrift fr
 ,luftschiffahrt10 ,beilage1 #ahic71 in 
a curved surface with #a_/ab rise1 if   
the angle of inclination of the chord of
 the surface be 1 and the angle between 
the direction of resultant air pressure 
and the normal to the direction of      
motion be 1 then  and the soaring speed 
is  ,v  7,p_/,k7#a_/7;,f77cos 777  while
 the efficiency is  ,w_/,r              
,weight_/,resistance  tan   ,the        
following were derived from experiments 
in the wind3            #c     #j     #c
     #f     #i     #ab  ,f77     #j4bj  
#j4hj    #j4ge   #j4ij   #a4jj    #a4je 
,tan       #j4ja   #j4jb    #j4jc       
#j4jd   #j4aj    #j4ag  so that         
according to him1 a curved surface shows
 finite soaring speeds when the angle of
 inclination is #j or even slightly     
negative4  #be ,the following formul    
proposed by ,mr4 ,chas4 ,m4 ,manly show 
how the center of pressure may be moved 
any desired distance either forward or  

backward without in any way affecting   
the center of gravity1 and by merely    
moving the front and rear wings the same
 amounts but in opposite directions1 the
 total movement of each wing being in   
either case five times the amount that  
is desired to move the mean ,,cp#a1 and 
the direction of movement of the front  
wing determining the direction of       
movement of ,,cp#a4  ,in ,figure #g1    
,,cpfw and ,,cprw are the centers of    
pressure of the front and rear wings    
respectively2 the weights of the wings1 
which are assumed to be equal and       
concentrated at their centers of figure1
 are represented by w1 w1 and a is the  
distance of the center of pressure in   
either wing from its center of figure4  
,the original mean center of pressure of
 the aerodrome is ,,cp#a1 ,w is the     
weight of the aerodrome1 supposed to be 
concentrated at ,,cg#a1 while m is the  
distance from ,,cprw to ,,cg#a4  ,now1  
if we have assumed that the rear wing1  
being of the same size as the front one1

 has a lifting effect of only #j4ff1 and
 on this assumption is calculated the   
proper relative positions of the front  
and rear wings to cause the ,,cp#a to   
come directly over the ,,cg#a1 and upon 
testing the aerodrome find that it is   
too heavy in front and1 therefore1 wish 
to move the center of pressure forward  
an amount1 say b1 without affecting the 
center of gravity1 we can calculate the 
proper relative positions of the front  
and rear wings in the following manner4 
,while the aerodrome as a whole is      
balanced at the point ,,cg#a1 the weight
 of the wings is not balanced around    
this point1 for the rear wing1 owing to 
its decreased lifting effect1 is        
proportionately farther from ,,cp#a than
 the front wing4 ,in order1 therefore1  
to avoid moving the center of gravity of
 the machine as a whole1 any movement of
 the wings must be made in such a way as
 to cause the difference between the    
weight of the rear wing multiplied by   
its distance from ,,cg#a and the weight 

of the front multiplied by its distance 
from ,,cg#a to equal a constant3 that   
is1   w7m  a7w7#j4ffma7  constant1  and 
#j4ccwm  #bwa  constant4  ,illustration3
 ,,fig4 #g4  ,illustration3 ,,fig4 #h4  
,illustration3 ,,fig4 #i4  ,,figs4 #g-i4
 ,diagrams ,illustrating formul for     
moving ,c4 ,p4 without disturbing ,c4   
,g4  ,if now the wings be moved so that 
,,cp#a is moved forward a distance b1 we
 may indicate the distance from ,,cg#a  
to the new ,,cprw by z1 and equating the
 difference between the weight of the   
rear wing multiplied by its new distance
 from ,,cg#a and the weight of the front
 wing multiplied by its new distance    
from ,,cg#a and making this difference  
equal to the constant difference1 we can
 calculate z in terms of m and b1 as    
follows3  ,fig4 #h1   w7a  z7w7#j4ff7z  
b7  ba7   #j4ccwm  #bwa1    z  m  #e;b4 
,knowing z1 we readily find that the new
 distance from ,,cpfw to ,,cg#a equals3 
#j4ff7z  b7  b  #j4ffm  #e;b4  ,in a    
similar manner we may calculate the     

proper relative positions of the front  
and rear wings when we wish to move the 
center of pressure backward a distance1 
b1 from the original ,,cp#a without     
changing the position of ,,cg#a4 ,from  
,fig4 #g1 we have as before3   w7m      
a7w7#j4ffma7  constant1                 
#j4ccwm  #bwa  constant4  ,fig4 #i1     
w7z#a  a7w7#j4ff7z#a;b7ba7   #j4ccwm    
#bwa4    z#a  m#e;b4  ,similarly we have
 for the new distance from ,,cpfw to    
,,cg#a3   #j4ff7z#a;b7b  #j4ffm#e;b4    
#bf ,it is to be remembered that these  
aerodromes were under incessant         
modifications1 ,no4 #d for instance1    
presenting successive changes which made
 of it in reality a number of different 
machines1 one merging by constant       
alterations into the other1 though it   
still went under the same name4 ,after  
#ahie the type of the models remained   
relatively constant1 but during the     
first five years of the work1           
constructions equal to the original     
building of at least eight or ten       

independent aerodromes were made4  #bg  
,chapter ,v4  #bh 8,pocketing0 is a form
 of distortion in which the canvas or   
silk bags locally in numerous places    
between the cross-ribs4  #bi ,the site  
of these experiments1 which was #cj     
miles below ,washington1 has been       
described4 ,the writer is designated by 
the initial 8,l02 ,dr4 ,barus1 who      
several times assisted1 by the letter   
8,b02 ,mr ,reed1 carpenter1 by 8,r02 ,mr
 ,maltby1 machinist1 by 8,m02 and ,mr4  
,gaertner1 instrument maker1 by 8,g40   
#cj ,weights and dimensions are here    
given in approximate pounds and feet4   
#ca 8,experiments in ,aerodynamics40    
#cb ,on the data of 8,aerodynamics10 a  
plane having #a4h sq4 ft4 of surface per
 pound1 and advancing at an angle of    
#bj1 would soar at a speed of #bd4a ft4 
per second4  #cc ,it will be remembered 
that the purely theoretical conclusions 
just cited apply to the power delivered 
in direct thrust1 but that of the above 
actual ,h4 ,p4 an indefinite amount was 

lost in friction and slip of propellers4
  #cd ,it may be observed that at this  
time the position of the ,,cp was       
calculated on the assumption that the   
pressure for flight surfaces was        
proportional to the areas1 without also 
allowing for the fact that the following
 surfaces1 like the tail1 were under the
 8lee0 of the wind and so far less      
efficient4 ,it follows1 then1 that the  
value ,,cp,,cg was not really #j1 as was
 assumed1 but something considerable4   
#ce ,very exact accuracy in these minute
 details is indispensable to the        
efficient working of the engines4  #cf  
,the reader who may care to note the    
evolution of this boiler1 by trial and  
error1 will find a portion of the many  
discarded types shown in ,plate #ac4    
p#abc      ,,part ,,ii4  #ahig ,,to     
#aijc  ,,by ,,charles ,m4 ,,manly       
,assistant in ,charge of ,experiments   
,,chapter ,i  ,,introductory  ,although 
in #ahif ,mr4 ,langley had made the firm
 resolution not to undertake the        

construction of a large man-carrying    
machine1 as he realized that his        
multitudinous administrative duties left
 him practically no time available for  
original research1 yet the longing to   
take the final great step of actually   
transporting a human being through the  
air1 which the successful flights of the
 models had now for the first time in   
the history of the world actually proved
 to be possible1 soon became            
irresistible4  ,ten years of almost     
disheartening difficulties1 a full      
appreciation of which can hardly be     
gained from the preceding description1  
had already been spent in demonstrating 
that mechanical flight was practicable1 
and ,mr4 ,langley thoroughly realized   
that the construction of a large        
aerodrome would involve as great1 if not
 even greater difficulties4             
,nevertheless1 his indomitable will1    
which balked at no obstacle1 however    
great it might seem1 prevailed against  
the advice of his close friends and     

associates1 and even that of his        
physician1 who had counselled him that a
 resumption of concentrated thought and 
vigorous endeavor would materially      
shorten his life1 which had already     
passed three score years4 ,only a few   
were privileged to come into close      
contact with him in his daily work1 and 
thereby catch the inspiration of his    
unwavering persistence1 his ceaseless   
perseverance1 his plain inability to    
submit to defeat2 but no one who has    
read the record of his astronomical     
expedition to ,mt4 ,whitney1 or the     
story of his development of the         
,bolometer1 or the preceding chapters of
 this history of his years of patient   
work in the development of the flying   
machine1 can have failed to obtain some 
appreciation of this most striking      
feature of his character4 ,having once  
determined on the accomplishment of a   
definite object1 no amount of difficulty
 that might arise deterred him from     
pushing on until in some way and by some

 means he had succeeded2 and no one     
appreciated better than he that if the  
thin edge of the right wedge can be     
inserted under an obstacle1 that        
obstacle can be removed1 no matter how  
formidable it may seem4  ,the           
undertaking of the construction of a    
large aerodrome was very largely        
influenced by ,president ,mc,kinley1 who
 had become impressed with the great    
p#abd possibilities of a flying machine 
as an engine of war4 ,when he found that
 ,mr4 ,langley was willing to devote his
 own time to the development of a       
machine1 provided the ,government would 
furnish the funds for the actual        
construction and tests of it1 he        
appointed a joint board1 consisting of  
,army and ,navy officers1 to investigate
 and report on the plans with which ,mr4
 ,langley had achieved success with the 
models4 ,the report of this joint board 
of ,army and ,navy officers being       
favorable1 the ,board of ,ordnance and  
,fortification of the ,war ,department1 

at the direction of ,president          
,mc,kinley1 requested ,mr4 ,langley to  
undertake the construction and test of a
 machine1 which1 while not expected to  
be a practical war machine1 might       
finally lead to the development of such 
an engine of war4 ,in this connection it
 is interesting to read a letter which  
,mr4 ,langley addressed to the ,board of
 ,ordnance and ,fortification at the    
time he undertook this work4            
,,smithsonian ,,institution1 ,december  
#ab1 #ahih4   ,the ,board of ,ordnance  
and ,fortification1 ,war ,department4   
,,gentlemen3 ,in response to your       
invitation1 ,i repeat what ,i had the   
honor to say to the ,board--that ,i am  
willing1 with the consent of  the       
,regents of this ,institution1 to       
undertake for the ,government the       
further investigation of the subject of 
the construction of a flying  machine on
 a scale capable of carrying a man1 the 
investigation to  include the           
construction1 development and test of   

such a machine  under conditions left as
 far as practicable in my discretion1 it
  being understood that my services are 
given to the ,government in  such time  
as may not be occupied by the business  
of the ,institution1  and without       
charge4   ,i have reason to believe that
 the cost of the construction will come 
within the sum of #ej1jjj4jj1 and that  
not more than one-half of  that will be 
called for in the coming year4   ,i     
entirely agree with what ,i understand  
to be the wish of the ,board  that      
privacy be observed with regard to the  
work1 and only when it  reaches a       
successful completion shall ,i wish to  
make public the fact  of its success4   
,i attach to this a memorandum of my    
understanding of some points of  detail 
in order to be sure that it is also the 
understanding of the  ,board1 and ,i am1
 gentlemen1   ,with much respect1  ,your
 obedient servant1  ,s4 ,p4 ,,langley4  
,,memorandum   ,,attached ,,to ,,my     
,,letter ,,of ,,this ,,date ,,to ,,the  

,,board ,,of ,,ordnance ,,and           
,,fortification   ,while stating that ,i
 have1 so far as ,i know1 an exclusive  
right of  property in the results of the
 experiments in aerodromics which  ,i   
have conducted heretofore and am now    
conducting1 and while  understanding    
that this property and all rights       
connected with it1  whether patentable  
or otherwise1 will remain mine          
unqualifiedly1 ,i  am glad to place     
these results1 without charge1 at the   
service of  the ,board of ,ordnance and 
,fortification for the special          
construction  at present proposed1 which
 seems to me to be of ,national utility4
  p#abe   ,i assume that no public      
statement will be made by the permission
  of the ,board until the work is       
terminated1 but that ,i may publish     
ultimately at my discretion a statement 
of any scientific work done  in this    
connection4   ,i understand that the    
exercise of this discretion includes the
  ordering and purchase of all material 

by contract or in open market1  and the 
employment of any necessary help1       
without restriction1 and  that1 while ,i
 desire that no money shall pass through
 my hands1  itemized bills for each     
expenditure1 made in proper form and    
approved by me1 will be paid by the     
,chief ,signal ,officer4   ,much has    
already been spent at the ,smithsonian  
,institution for the  purpose in        
question1 in special apparatus1 tools   
and experiments1  and in recent         
constructions now actually going on1    
which have  involved still more time    
than money1 and which are essential for 
experimental use in building the        
proposed machine2 and since to          
re-create all this independently would  
greatly defer progress1 ,i  assume that 
my discretion includes the decision as  
to how far this  shall be used and paid 
for at the cost of this allotment 7it   
being  understood that ,i have no       
personal property in any of the material
  which might be transferred for the    

purpose of the work72 and ,i also       
assume that my discretion includes the  
decision as to where the work  shall be 
conducted--that is1 whether in shops    
already constructed1  or in others to be
 elsewhere erected or rented1 with the  
necessary  adjuncts1 whether on land or 
water1 and generally whatever is        
necessary to the earliest attainment of 
the object desired by the  ,board4   ,s4
 ,p4 ,,langley4  ,,smithsonian          
,,institution1 ,,washington1 ,d4 ,c41   
,december #ab1 #ahih4   ,as is always   
the case in experimental work1          
especially in a field so very new as was
 the field of aerodromics at the time   
that this larger construction was       
undertaken1 the 8plant10 or shops and   
laboratories required for the           
constructional and testing work1 grew to
 a size far beyond what seemed even     
remotely possible at the beginning of   
the work2 and even the mere             
administration involved in the carrying 
on of this work proved to be no         

inconsiderable matter before it had     
progressed very far4  ,the years of     
experiment with the models had          
demonstrated clearly that the greatest  
difficulty in the development of the    
aerodrome was the construction of a     
suitable power generator1 which should  
combine the elements of extreme         
lightness and unusual power with a fair 
degree of durability4 ,although         
remarkably good results had been secured
 in the case of the models through the  
use of steam1 it was realized from the  
first that not only would the           
development of a steam-power plant for a
 large man-carrying aerodrome present   
difficulties of a constructional nature1
 but that such a steam plant would      
necessarily be so fragile and delicate  
as to make it a constant menace to the  
machine which it was to propel4 ,the    
solution of the difficulty1 it was      
believed1 was to be found in the use of 
an internal combustion engine2 but ,mr4 
,langley had had very little experience 

with such engines1 and was averse       
therefore to undertaking the            
construction of a large aerodrome until 
he had assurance that a suitable        
gasoline engine could be secured4       
,before making an agreement to attempt  
the work for the ,war p#abf ,department1
 he had1 therefore1 made a search for a 
reliable builder who would undertake to 
construct a gasoline engine of not less 
than #ab horse-power to weigh not       
exceeding #ajj pounds1 and what then    
seemed a safe contract had been entered 
into with such a builder to supply one  
engine which would meet these           
requirements4  ,almost immediately      
before the ,board of ,ordnance and      
,fortification had officially placed the
 work in ,mr4 ,langley's hands and had  
made an allotment of fifty thousand     
dollars to meet the expenses thereof1 it
 was found that the engine builder could
 not be depended on1 and that it would1 
therefore1 be necessary to find one who 
was more reliable and more experienced  

in the construction of light engines4   
,after a most extended search for the   
best builder to undertake this work1 a  
contract was entered into on ,december  
#ab1 #ahih1 with ,mr4 ,s4 ,m4 ,balzer1  
an engine builder in ,new ,york ,city4  
,he was to furnish a twelve-horse-power 
engine to weigh not more then #ajj      
pounds1 and delivery of it was to be    
made on or before ,february #bh1 #ahii4 
,with this great problem of the engine  
apparently provided for1 every facility 
of the ,institution shops was pressed to
 the utmost limit in order to have the  
frame1 supporting surfaces1 launching   
apparatus1 and other accessories ready  
as soon as possible after the delivery  
of the engine4 ,it was expected from the
 first that more power would be         
necessary than this one engine would    
furnish1 and provision had been made in 
the contract that a duplicate engine    
should be constructed immediately after 
the completion of this first one4 ,from 
past experience1 however1 it was not    

likely that the correct balancing of the
 aerodrome could be determined from a   
priori calculation based on the results 
obtained with the models1 and it was1   
therefore1 expected that the aerodrome  
would have to be launched several times 
before a successful flight could be     
obtained4 ,in view of this it was       
planned to make a test of the machine as
 soon as the first engine was ready1    
with the expectation that1 while the    
aerodrome would not have sufficient     
power to fly1 yet the test would furnish
 definite data on the all-important     
question of balancing1 and also         
determine whether or not the launching  
apparatus would require modification4   
,in fact1 ,mr4 ,langley felt so         
apprehensive that the first1 and        
possibly the second test1 would be      
unsuccessful that1 in order to avoid the
 possibility of a fatal accident1 it was
 planned that a dummy should be used to 
represent the weight of the man in these
 preliminary tests4  ,this plan1        

however1 was not carried out4 ,in #aijc1
 when the large aerodrome was finally   
completed1 so much time had been lost   
that the writer proposed to assume the  
risks of such an accident and to guide  
the machine in its first test1 in the   
hope of avoiding a disaster1 with the   
consequent delay of months for repairs1 
which the presence of a controlling hand
 capable of correcting any inaccuracies 
of balancing rendered far less likely to
 occur4 ,to this proposal ,mr4 ,langley 
assented with great reluctance1 as he   
fully realized the danger involved4     
p#abg  ,particular attention is called  
to the above facts1 which clearly show  
that while a certain degree of success  
in the initial tests was later hoped    
for1 yet from the beginning it had been 
felt rather certain that several tests  
would have to be made before final      
success would be achieved4  ,to those   
experienced in scientific experiments   
this realization of the probability of  
several tests being necessary before    

success could reasonably be expected    
does not seem strange1 for the record of
 past experience contains very few      
examples of epoch-making inventions     
springing full fledged from the hand of 
their maker and proving a success on the
 first test4  ,the two experiments made 
in the fall of #aijc1 in which the      
aerodrome was each time so damaged in   
the process of launching that its       
ability to fly was never really tested1 
should therefore be considered merely as
 the first of a series which it had been
 expected would need to be made before  
success would be achieved4 ,further     
tests were made impossible at the time  
on account of the lack of funds1 the    
expense of such work being unusually    
heavy4  ,while the lack of funds1       
therefore1 was the real cause of the    
temporary suspension of the work1 yet an
 influence which does not often enter   
into scientific work--the unjust        
criticism of a hostile press--was       
directly responsible for the lack of    

funds4 ,it seems very certain that had  
it not been for this criticism of the   
press the funds would have been readily 
forthcoming for continuing the work to  
the point of success4   p#abh           
,,chapter ,,ii  ,,general               
,,considerations  ,in the development of
 man-carrying flying machines two       
well-defined paths are open4 ,first3    
,starting with gliding machines1 in     
which gravity furnishes the motive      
power1 the operator may by practice     
acquire sufficient skill in controlling 
them to warrant the addition of         
propelling mechanism1 and individual    
skill in control may be gradually       
replaced by automatic controlling       
mechanism4 ,second3 ,from self-propelled
 models1 possessing                     
automatic-equilibrium controlling       
mechanism1 and of a sufficient size to  
furnish determinative data1 one may1 by 
proper modification in size and         
construction1 progress to an            
automatically controlled man-carrying   

machine in which1 for ideal conditions1 
no especial skill on the part of the    
operator is required4 ,each method has  
its advantages4  ,after concluding his  
earlier and purely physical researches1 
the results of which were embodied in   
8,experiments in ,aerodynamics10 ,mr4   
,langley was so firmly convinced of the 
practicability of mechanical flight that
 he undertook the construction of the   
model aerodromes in order to demonstrate
 it4 ,it is very doubtful if at any     
time1 prior to the successful flights of
 the models in #ahif1 he seriously      
contemplated the construction of        
man-carrying machines4 ,his object in   
developing the models was not1          
therefore1 to furnish a prototype for a 
large machine1 but merely to demonstrate
 the feasibility of mechanical flight2  
and this he did4 ,this is shown very    
clearly by the closing remark of the    
article he published in #ahig1          
describing the flights of the models4   
8,i have now brought to a close the     

portion of the work which seemed to be  
specially mine--the demonstration of the
 practicability of mechanical           
flight---and for the next stage1 which  
is the commercial and practical         
development of the idea1 it is probable 
that the world may look to others40#cg  
,when he later undertook the            
construction of the large machine for   
the ,war ,department it was natural     
that1 with the inspiring sight of the   
models in flight still fresh in his     
mind1 he determined to use as a         
prototype these successful machines1    
which were the only things of human     
construction that had ever really flown 
for any considerable distance4  ,not    
being an engineer1 and realizing that to
 pass from the construction of models to
 that of man-carrying machines involved 
the solution of many engineering        
problems1 ,mr4 ,langley1 in the spring  
of #ahih1 sought the advice of ,dr4 ,r4 
,h4 ,thurston1 who had from the first   
manifested the deepest interest in his  

p#abi work in aerodromics4 ,on the      
recommendation of ,dr4 ,thurston he     
engaged the services of the writer1 who 
assumed charge of the work in ,june1    
#ahih4  ,while the method of 8cut and   
try0 had brought success in the models1 
and was perhaps the only method by which
 they could have been successfully      
developed1 it was thought that1 with    
these models as a basis of design1 much 
time would be saved by making an        
analytical study of them as engineering 
structures1 and from the data thus      
obtained the proper proportions for the 
parts of the larger machine could be    
calculated4  ,such an analytical study1 
however1 revealed very little from which
 to make calculations as to the strength
 necessary for the various parts of the 
large machine1 but it did show very     
clearly that most of the parts were     
working under stresses generally far    
above the elastic limit of the          
materials1 and in many cases the        
ultimate breaking strength was closely  

approached4 ,such a condition was the   
natural outcome of the method by which  
these models had been developed--all the
 various parts having been built at     
first of the least possible weight and1 
when they proved too weak1 strengthened 
until they would withstand the stresses 
imposed on them4 ,it is extremely       
doubtful if previous calculations as to 
the strength necessary would have been  
of any assistance1 in fact it is        
probable that it would have been a      
distinct disadvantage and would have    
resulted in the machines being entirely 
too heavy for flight4  ,the exact       
strength which had been incorporated in 
the frames of the models was as unknown 
as was the exact amount of the stresses 
which they has been made to withstand4  
,their static strength was easily       
determined by calculation1 but the      
stresses due to the live loads were     
incapable of exact determination from   
the available data1 for stresses produce
 strains1 which in turn generally cause 

distortions accompanied by greatly      
increased stresses4 ,while exact data   
were1 therefore1 lacking as to stresses 
and strengths in many of the important  
parts1 yet the models furnished most    
important illustrations of unusual      
strength for minimum weight1 and a      
careful study of them showed many ways  
in which increased strength could be    
obtained with decreased weight which    
could hardly have been devised without  
these concrete examples4  ,it was1      
however1 by no means possible to build  
the large aerodrome within the          
permissible limits of weight by simply  
increasing the various parts of the     
models according to some predetermined  
function of the size of the whole4  ,the
 fundamental difficulty is that         
inevitably1 by the laws of geometry1    
which are mere expressions of the       
properties of space1 if a solid of any  
form is magnified1 the weight increases 
as the cube1 while the surface increases
 only as the square1 of the linear      

dimensions4 ,successive generations of  
physicists and mathematicians pointed   
out that while this 8law of the cube0 is
 of advantage in the construction of    
balloons1 yet it is a stumbling block   
that will prevent man p#acj from ever   
building a dynamic flying machine       
sufficiently large to carry even one    
human being4#ch  ,however1 since        
strength is a function of material and  
form rather than weight1 it is possible 
by selecting proper materials and       
adopting suitable structural forms to   
evade to a certain extent this 8law of  
the cube40 ,the whole history of        
structural science has therefore been a 
series of attempts to find stronger and 
lighter material and to discover methods
 of so modifying form as to dispense    
with all parts of a structure that do   
not contribute to its strength4 ,so in  
aerodromics the structural problem has  
been that of finding materials and forms
 best suited to the purpose for which   
they are required1 for it does not      

always follow that either the form or   
the material best suited for one scale  
of construction is the most advantageous
 to employ on a different scale4 ,nor is
 even the form or material which gives  
the greatest strength for the least     
weight necessarily the best to employ4  
,for the structural problem must        
necessarily be co-ordinated with those  
of balancing1 propelling1 and           
transporting1 and each must1 therefore1 
have its proper attention in the design 
of the whole machine4  ,many of the     
general considerations of the design of 
an aerodrome sufficiently large to      
transport a man were determined during  
the spring and summer of #ahih1 when the
 first actual drawings 7,plate #cb1     
,figs4 #a1 #b and #c7 of the proposed   
machine were made4 ,starting with the   
assumption that the ,models ,nos4 #e and
 #f were capable of transporting a load 
of approximately ten pounds more than   
their weight1 it was seen that1 since   
the supporting surface of any aerodrome 

would increase approximately as the     
square of the linear dimensions1 in     
order to carry a man the aerodrome would
 need to be approximately four times the
 linear dimensions of these models4     
,calculations based on the results      
accomplished in the construction of the 
models indicated that such an aerodrome 
would need to be equipped with engines  
developing #bd horse-power4 ,the best   
that could reasonably be hoped for was  
that these engines would not weigh over 
#bjj pounds1 and1 therefore1 allowing   
#dj pounds for fuel and fuel tanks1 it  
became necessary to bring the weight of 
frame1 supporting surfaces1 tail1       
rudder1 propellers and every other      
accessory within #bej pounds1 if the    
total weight of the machine1 including  
#aej pounds for the aeronaut1 was not to
 exceed #fdj pounds1 or #af times the   
combined weight of the model and its    
load of #aj pounds4 ,although the       
problem of constructing the frame1 wings
 and all other parts within the limit of

 #bej pounds seemed indeed formidable1  
it was believed that the greatest       
obstacle in the production of such a    
machine would be that of securing a     
sufficiently light and powerful engine  
to propel it4  ,illustration3 ,,pl4 #cb 
,,drawings ,,of ,,proposed              
,,man-,,carrying ,,aerodrome1 #ahih     
p#aca  ,a brief account has already been
 given of the attempts made by ,mr4     
,langley to secure a suitable gasoline  
engine for the large aerodrome1 but the 
difficulties encountered in the search  
have not perhaps been sufficiently      
emphasized4 ,at this time 7#ahih7 the   
automobile industry1 through which has  
come the development of the gasoline    
engine1 was in its infancy1 and there   
were few builders either in the ,united 
,states or ,europe who were attempting  
anything but rough and heavy            
construction4 ,many of them were        
enthusiastic over the possibilities of  
the internal combustion engine1 and were
 ready to talk of devising such an      

engine as the aerodrome would require1  
but few were willing to guarantee any   
such definite results as were demanded4 
,however1 the prospects of securing a   
suitable gasoline engine from a reliable
 builder within a reasonable time seemed
 so strong that it was decided early in 
#ahih to begin the construction of the  
frame on the general plan which would   
probably be best adapted for use with a 
gasoline engine1 and in case it finally 
proved impossible to secure such an     
engine1 to construct later a steam plant
 which could be adapted to this         
particular frame4  ,some tentative work 
on the construction of the frame was    
accordingly begun in the summer of      
#ahih1 some months before an engine     
builder was found who seemed likely to  
be successful in furnishing the engines4
 ,an extensive series of tests on       
propellers was also made at this time   
for the immediate purpose of determining
 what form and size would be best1 since
 the dimensions of the transverse frame 

could not be definitely settled until it
 was known how large the propellers     
would need to be4  ,preliminary designs 
were also begun for the wings1 rudders1 
and launching apparatus1 but when the   
point was reached of actually making the
 working drawings for these1 it was seen
 that the change in the scale of the    
work required many important            
modifications in constructional details4
 ,as the models had flown successfully  
only three times1 and in each case under
 practically the same conditions1 it was
 felt that it would be unwise to make   
changes in important details without    
first making a series of tests of the   
models in flight to determine the effect
 of such changes4 ,it was therefore     
decided to completely overhaul ,models  
,nos4 #e and #f1 strengthening them in  
many important parts and 8tuning up0    
their power plants1 which had slightly  
deteriorated since they were last used  
in ,november1 #ahif4 ,when the work of  
preparing these models for further      

experiments was begun it was thought    
that it would require at most only a few
 weeks1 but as it progressed it was     
found that certain parts of the         
mechanical work on the engines had been 
so poorly executed originally that it   
would be necessary to practically       
rebuild the engines4 ,the final result  
was that the power plants of both       
aerodromes were entirely rebuilt1 and   
they were not ready for actual test in  
flight until the spring of #ahii4 p#acb 
,much of the preliminary work necessary 
for the determination of actual working 
plans was therefore completed in the    
summer and fall of #ahih1 and when on   
,december #ab a seemingly satisfactory  
contract for the engines for the large  
aerodrome had been made it was thought  
that rapid progress could be made on the
 constructional work after ,january #a1 
#ahii1 when the allotment from the ,war 
,department would become available4     
p#acc    ,,chapter ,,iii  ,,experiments 
,,with ,,models  ,immediately after the 

contract for the engine had been placed 
and the actual work had been begun1     
attention was given to the problem of   
providing means for properly launching  
the aerodrome4 ,on the theory that the  
plan of launching the small aerodromes1 
which had finally been adopted after    
many years of painstaking experiment1   
would be the best to employ for the     
large aerodrome1 ,mr4 ,langley decided  
to have constructed a large house-boat  
with the launching track arranged on it 
in a way similar to that used for the   
small machines4 ,while the general plans
 for this boat had been under           
consideration for some time1 the actual 
working drawings were completed in      
,january1 #ahii1 and so great seemed the
 need for expediting its construction1  
in order to have it ready at the time   
when the engine was expected1 that the  
contract which was made for its         
construction specifically provided for  
its being completed promptly1 there     
being a large forfeit to cover any delay

 on the part of the contractor4  ,while 
the boat itself was being constructed1  
the working drawings were completed for 
the house to be built on it1 and a      
contract was made for the construction  
of this house within a given period1    
there being also a time forfeit in this 
contract4  ,when the end of ,february   
arrived1 it was found that1 although the
 engine builder had succeeded in        
constructing an engine which weighed one
 hundred pounds1 and which theoretically
 should have given something over twelve
 horse-power1 yet he was unable to make 
it work properly4 ,and then began a     
protracted period of most exasperating  
delays1 the engine builder promising    
from week to week that certainly within 
the succeeding ten days he would be able
 to make delivery of the engine         
developing the full horse-power for     
which the contract called4 ,after this  
delay on the engine had continued for   
some months--a delay which necessitated 
the cessation of the work on the main   

steel frame of the aerodrome1 as it was 
deemed best to make certain tests of the
 engine running while supported by a    
portion of the frame to determine       
whether or not it was strong enough     
before completing the rest of it---,mr4 
,langley decided to employ part of the  
time in the construction of a model of  
one-eighth the linear dimensions of the 
large aerodrome1 which was to be used in
 testing a model of the newly designed  
launching apparatus described later1 and
 which might also be flown as a kite in 
making check measurements on the proper 
balancing which should be employed for  
the large aerodrome4 p#acd  ,the        
perfected launching apparatus which had 
been used for the steam-driven models   
,nos4 #e and #f 7described in ,part ,i1 
,chapter ,x7 had proved most            
satisfactory and reliable1 but when the 
designs were made for a launching       
apparatus for the large machine it was  
found that an exact duplication of the  
plan of the small one involved serious  

difficulties in connection with the     
construction of the house-boat1 owing to
 the very considerable weight and size  
of the turn-table necessary to permit   
the aerodrome to be launched in any     
desired direction1 regardless of the    
direction in which the houseboat might  
be pointing under the influence of the  
wind and tide4 ,a new design was        
accordingly made for a launching        
apparatus in which the launching car was
 to run on a track mounted directly on  
the turn-table1 the launching car       
supporting the aerodrome from           
underneath1 instead of being mounted in 
an inverted position on an overhead     
track with the aerodrome depending from 
it4  ,from the previous description of  
the launching apparatus1 it will be     
recalled that1 in order to provide that 
the aerodrome should drop slightly at   
the moment of its release from the car1 
and thereby avoid all danger of         
entanglement1 the speed of the launching
 car at the point at which the aerodrome

 was released was purposely made less   
than the 8soaring speed0 of the         
aerodrome4 ,having this feature in mind1
 when designing the 8underneath0        
launching apparatus1 it was recognized  
that the danger of the aerodrome        
becoming entangled with this form of    
apparatus could be avoided by making the
 launching speed greater than the       
velocity which it would be necessary for
 the aerodrome to have in order to soar1
 provided the balancing was correct and 
the aerodrome did soar4 ,nevertheless1  
it was deemed unwise to put too much    
dependence on the empirical calculations
 from which the balancing of the large  
aerodrome would necessarily be          
determined1 and1 therefore1 some means  
seemed necessary for causing the        
launching car to drop out of the way    
immediately upon releasing the          
aerodrome4 ,in the new design1 more     
completely described below1 in ,chapter 
,,iv1 this was accomplished by so       
arranging a portion of the front end of 

the track that1 at the moment the       
launching car released the aerodrome1 it
 dropped like a disappearing gun        
carriage1 leaving the aerodrome free in 
the air with no possibility of becoming 
entangled1 provided the aerodrome itself
 did not drop more rapidly than an angle
 of #ae degrees4  ,a small working model
 of this launching apparatus1 one-eighth
 the linear dimensions of that which    
would be necessary for the large        
aerodrome1 was first designed and       
constructed in the shop1 the small      
one-eighth-size model of the large      
aerodrome being launched from it into a 
sheet stretched in front of it to act as
 a buffer4 ,when it was found to work   
very satisfactorily1 a large one1 twice 
this size1 was immediately built for use
 with the steam-driven models ,nos4 #e  
and #f4 p#ace  ,these models1 ,nos4 #e  
and #f1 which had flown so successfully 
in #ahif1 had1 during the preceding     
twelve months1 been completely          
overhauled and thoroughly tested in     

preparing them for trials in actual     
flight4 ,many pendulum tests were made  
on both aerodromes1 and it was found    
after repeated trial that each could be 
depended on to show a lift of sixty per 
cent of its flying weight4  ,this was   
more than sufficient for flight1 but in 
order to insure successful trials and   
avoid delay no aerodrome was launched   
until it had shown previously its       
ability to generate enough power to     
maintain for at least two minutes a lift
 of at least fifty per cent of the total
 flying weight4  ,models ,nos4 #e and   
#f1 having thus proved their readiness  
for trial in flight1 were accordingly1  
in ,april1 #ahii1 taken to ,chopawamsic 
,island1 together with the old          
8overhead0 launching apparatus and the  
new one above described1 and placed on a
 small house-boat similar to the one    
which had been used in #ahif4 ,two men  
were detailed for this special work1 and
 were first employed in mounting the old
 launching apparatus for a few          

preliminary tests with it1 in order to  
make sure that the aerodromes were in   
proper working order before trying them 
on the new 8underneath0 one4 ,after     
considerable delay1 due to various      
causes1 this apparatus and the          
aerodromes were got into proper working 
condition1 and during ,june1 ,july and  
,august the following flights were made 
with these machines1 the record being   
condensed from the reports made by the  
writer to ,mr4 ,langley while he was    
abroad4    ,,condensed ,,record ,,of    
,,flights ,,of ,,aerodromes ,,nos4 #e   
,,and #f  ,,from ,,june #g ,,to ,,august
 #c1 #ahii   ,,june #g--;,,aerodrome    
,,no4 #f  ,after making a preliminary   
test of the engines and boiler1 with the
 aerodrome mounted on benches inside the
 house-boat1 to insure that everything  
connected with the power plant was in   
proper working order1 the aerodrome was 
mounted on the launching apparatus on   
top of the house1 the various parts were
 assembled and everything made ready for

 a flight4 ,as it was calculated that   
this aerodrome would require a soaring  
speed of something like twenty-five feet
 a second1 the springs which furnished  
the motive power for the initial        
acceleration of the car were adjusted to
 the proper tension to cause it to reach
 a speed of approximately twenty-three  
feet a second at the moment of          
launching4 ,everything being in         
readiness the burners were lighted but  
worked somewhat sluggishly at first1 so 
that two minutes were consumed in       
raising a steam pressure of #aaj pounds4
 ,although this pressure should have    
been reached within one minute after    
lighting the burners1 and the extra     
minute which had been consumed had made 
a drain on the supply of fuel and water 
which should have p#acf been left for   
consumption during flight1 yet it was   
thought best to launch the aerodrome1 so
 at #ab4cg p4 m4 the car was released   
and the aerodrome launched4 ,the        
launching apparatus worked perfectly2   

the aerodrome started off smoothly1 and 
immediately after being released from   
the car it dropped slightly and began to
 turn to the right4 ,it had been        
impossible to move the house-boat out   
into the stream so as to point the      
launching apparatus directly into the   
wind1 as one end had settled slightly on
 the muddy beach in consequence of the  
existing low tide4 ,for this reason it  
was necessary to launch the aerodrome   
due south1 while the wind1 which was    
very light1 was from the                
north-northeast1 and1 therefore1 blowing
 on its port quarter4 ,the effect of the
 aerodrome turning to the right         
immediately after being launched was    
that it caused the wind to strike it to 
an increasing extent on the port side   
until1 finally1 it was going directly   
with the wind4 ,it did not1 however1    
continue in this direction1 but kept    
turning to the right in a circle until  
it headed directly into the wind1 which1
 now striking the under instead of the  

upper surface of the wings1 immediately 
caused the aerodrome to rise4 ,it       
continued circling1 making three        
complete circles of approximately #bjj  
feet diameter1 dropping slightly when   
moving with the wind1 but rising when   
moving against it1 until1 at the        
completion of the third circle1 it had  
altered its path to such an extent that 
the left front wing touched a tree and  
caused the front of the machine to dip a
 little4 ,it1 however1 kept up its      
flight1 but the contact with the tree   
had so lowered its bow1 and apparently  
also caused the wings to be twisted to  
such an extent1 that it seemed unable to
 rise again1 and after making another   
quarter circle it descended4 ,although  
the propellers were still turning when  
it struck the water1 they had very      
greatly decreased their speed1 making it
 apparent that the power had been very  
greatly reduced through the exhaustion  
of the fuel and water supply4 ,the      
aerodrome did not sink1 but slowly      

drifted with the current of the creek   
and was recovered in about five minutes 
and brought to the house-boat1 where the
 wings were dismounted and dried1 and   
the metal parts were carefully wiped off
 to prevent them from rusting4 ,the path
 of this flight is plotted on a portion 
of a coast-survey chart and is shown in 
,plate #cc4  ,illustration3 ,,pl4 #cc   
,,paths ,,of ,,flight ,,of ,,aerodrome  
,,no4 #f1 ,,june #g1 #ahii  ,this       
erratic circling at first seemed        
unaccountable1 but on closer            
examination1 after the aerodrome had    
been brought into the house-boat1 it was
 found that the pin which connects the  
synchronizing gear to the port propeller
 shaft had been sheared off4 ,this had  
evidently happened while the aerodrome  
was still on the launching apparatus4   
,the effect of this was to throw the    
total work of the water-circulating pump
 on the starboard engine1 thus giving   
the port engine less work to do1 and    
consequently making the port propeller  

run much faster than the starboard one1 
and thereby causing the peculiar and    
erratic circling of the aerodrome4 ,it  
is evident that the undulatory motion of
 the p#acg aerodrome was due to the fact
 that1 when it was moving against the   
wind1 the speed relative to the air was 
greater than when it circled so as to go
 with the wind1 and that this greater   
relative velocity increased the lifting 
power of the aerodrome4  ,the total time
 of the flight was #eg seconds1 and the 
distance covered was between #bjjj and  
#bejj feet1 thus giving a speed of a    
little less than #cj miles an hour4     
,comparing this flight with that of     
,november #bh1 #ahif1 made by the same  
machine1 it will be noted that in the   
earlier flight the velocity was         
practically the same1 but that the time 
of flight and the distance traversed    
then were nearly twice as great as in   
the present case4  ,a complete record of
 the details1 not only of weight1 but   
also of the position of the wings1 the  

center of gravity1 etc41 which show the 
exact condition of the aerodrome when it
 made this flight1 will be found in the 
appendix 7,data ,sheet1 ,no4 #c74       
,,june #ac--;,,aerodrome ,,no4 #f  ,in  
the flight of ,june #g there was a      
slight trembling of the aerodrome while 
it was in the air1 and although this was
 probably due to the fact that the      
synchronizing gear was out of operation 
on account of the shearing off of one of
 the pins which held it1 allowing the   
port engine to run faster than the      
starboard one1 it was thought possible  
that some of the trembling might be due 
to the 8wind-vane0 rudder1 which had    
been added to represent the equivalent  
of a steering device by which the       
operator would control the direction of 
the large machine4 ,it was decided1     
therefore1 to omit the 8wind-vane0      
rudder in the present test1 but to test 
the aerodrome with the same equipment of
 single-tier wings and ,pnaud tail that 
had been used in the previous flight1   

the reel and float being moved to bring 
the ,,cg the same as on ,june #g4       
,everything being in readiness1 with the
 launching track pointed south1 and the 
wind blowing only about #e-a_/b miles an
 hour from the southwest1 the burners   
were lighted and #fc seconds were       
consumed before the steam pressure rose 
to #ajj pounds4 ,although the valve     
which controlled the burner was open to 
its full extent the pressure showed no  
tendency to rise above #ajj pounds1     
which was not considered quite high     
enough to furnish sufficient power for a
 successful flight1 but as it was       
desired to determine at once at how low 
a steam pressure the aerodrome would fly
 successfully1 it was decided to launch 
it even at this pressure4 ,the launching
 apparatus was accordingly released and 
the aerodrome started off1 gliding down 
about three feet immediately after being
 released1 and then rising again1       
turning slightly to the right and then  
heading directly for the ,virginia      

shore1 where it seemed that it would    
smash itself in the heavy growth of     
timber1 but when it was about #bej feet 
from the shore it turned towards the    
right and started back towards the      
island4 ,the wind1 however1 which was   
blowing from its rear1 evidently got    
down the smoke-stack and put out the    
fire1 p#ach for the aerodrome commenced 
to descend as soon as it turned its back
 to the wind1 and came down in the      
channel of the creek4 ,the path of this 
flight is shown by the solid line in    
,plate #cd4  ,the total distance        
covered1 as measured by plotting the    
course of its flight on the coast-survey
 chart1 was about #ahjj feet1 and the   
length of time of flight was #dj        
seconds4 ,the aerodrome was immediately 
recovered and brought into the          
house-boat1 where it was found that     
there were still about #ajjj grammes of 
water and #ajj grammes of fuel unused in
 it1 showing conclusively that the fire 
had been put out by the wind4  ,upon    

inspection it was found that the        
aerodrome was uninjured1 and although   
the burner had not worked at all        
satisfactorily1 yet as the weather was  
exceedingly favorable it was decided to 
make another trial with it immediately1 
using the superposed wings4#ci          
,everything being in readiness the      
burners were lighted1 and #gj seconds   
were consumed before the pressure rose  
to #ij pounds1 beyond which it was      
impossible to make it rise4 ,although it
 was felt certain that #ij pounds was   
not sufficient pressure to furnish the  
power necessary1 yet as a storm was     
approaching in the distance1 it was     
decided to launch the aerodrome1 as it  
could at least be determined whether it 
was properly balanced for the superposed
 wings4 ,when a total of #ge seconds had
 been consumed the car was released and 
the aerodrome was launched4 ,the wooden 
arrangement for pressing down on the top
 of the wings to keep the aerodrome from
 being injured by the wind while it was 

on the car had been raised to the proper
 height for the superposed wings1 but it
 had not been noticed that the sticks   
which support this arrangement had been 
elevated so much that they would come in
 contact with the beam extending across 
the boat1 and from which the launching  
track was supported4 ,just as these     
sticks reached the cross-beam1 however1 
it was noticed that they projected about
 three inches above the lower side of   
it2 but the next moment they struck it1 
and although the force with which the   
car was running broke all four of them1 
the blow was sufficient to slow down the
 car1 and thereby cause the aerodrome to
 be launched at a very greatly reduced  
speed2 not over one-fifth of what it    
should have been4 ,the shock of breaking
 these sticks evidently jarred the      
burners so that the fire was            
extinguished1 for the aerodrome shot    
forward for about #be feet and settled  
with everything intact1 and with its    
midrod perfectly horizontal4 ,the       

aerodrome itself sustained absolutely no
 injury1 coming down as easily as though
 it had been lowered by a rope1 and     
would have been given another trial     
immediately but for the fact that it was
 very late in the afternoon and darkness
 was rapidly approaching4 ,the data on  
setting of wings1 tail1 etc41 are shown 
on ,data ,sheet ,no4 #d 7,appendix74    
p#aci    ,,june #bb--;,,aerodrome ,,no4 
#f  ,after several days' delay1 due to  
numerous small but exceedingly annoying 
troubles1--such as the leaking of       
boilers because of defects in the copper
 tubing1 and the bursting of the air    
tank1 due to its being pumped up to an  
excessive pressure1 which a defective   
pressure gauge had failed to            
indicate1---,aerodrome ,no4 #f was made 
ready for another trial1 and it was     
decided to test it again with the       
superposed wings which had been used in 
the second experiment of ,june #ac4 ,the
 aerodrome was mounted on the 8overhead0
 launching apparatus1 which it will be  

remembered had been used in all the     
previous tests1 and after #ij seconds   
had been consumed in raising a steam    
pressure of #aaj pounds1 it was launched
 directly into the wind1 which was due  
south4 ,after leaving the launching car1
 the aerodrome flew straight ahead for  
about #ge feet1 when it suddenly turned 
its bow up into the air at an angle of  
about #ae degrees1 and it seemed that   
the machine would be blown back onto the
 house-boat4 ,however1 when the rear end
 of the tail was within about #aj feet  
of the boat1 and only about #aj feet    
above the water1 it suddenly regained   
its equilibrium and went straight ahead 
again in the face of the wind with the  
guy-posts only about #d feet above the  
surface of the water1 flying almost     
exactly horizontally for a distance of  
about #ajj feet1 when the bow again     
suddenly became elevated4 ,as the       
aerodrome was so close to the water1 the
 wind forced it down until the burners  
were extinguished by coming in contact  

with the water4 ,this brought the       
aerodrome to a standstill absolutely    
uninjured1 the propellers being several 
inches above the water when they quit   
turning4 ,the aerodrome was brought into
 the house-boat and thoroughly dried    
out1 and another trial would have been  
made with it immediately but the wind   
which had been steadily increasing was  
now blowing something more than #ab     
miles an hour1 and it was considered    
best not to attempt experiments in so   
strong and gusty a wind1 for fear of the
 wings being broken by the wind suddenly
 veering and striking them on the side  
or rear while the aerodrome was still on
 the launching apparatus4 ,the peculiar 
action of the aerodrome in the air      
appeared to be due to the fact that the 
propellers interfered more with the     
lifting power of the rear superposed    
wings1 as they were then constructed1   
than they did with the 8single-tier0    
ones4 ,the data on the setting of the   
wings1 tail1 etc41 are shown on ,data   

,sheet ,no4 #e 7,appendix74  ,it was    
also found after the experiment that one
 of the workmen1 in assembling the      
machine on the launching car1 had       
secretly increased the stiffness of the 
spring which controls the elasticity of 
the ,pnaud tail4 ,the effect of this    
increase in the stiffness of the ,pnaud 
tail might at first thought appear to be
 similar to that of moving the center of
 pressure forward4 ,upon a closer       
analysis1 however1 it will be seen that 
the effect is very much greater1 as     
excessive stiffness of the ,pnaud tail  
not only causes the aerodrome to elevate
 its bow1 p#adj but requires the        
overcoming of a strong downward force at
 the rear1 even more serious than would 
be caused by placing an extra load at   
the rear of the machine without regard  
to its effect on the balancing4 ,in     
experiments of this kind1 however1 the  
workmen get certain ideas of their own  
as to how the work should be conducted1 
and it is almost impossible in          

assembling the aerodrome to prevent them
 from making adjustments which are quite
 different from those which they have   
been directed to make1 and which have   
been definitely planned with a view to  
determining the effect of slight changes
 which it is desired shall not be masked
 by changes of any kind in other        
details4    ,,june #bc--;,,aerodrome    
,,no4 #f  ,the wind1 which had been     
blowing half a gale all day1 gradually  
quieted down towards sunset and at five 
o'clock was very light1 blowing only two
 miles an hour from the east-southeast4 
,as one of the rear superposed wings had
 been injured on the previous day in    
carrying the aerodrome into the         
house-boat after its short and erratic  
flight1 it was decided to use the       
8single-tier0 wings in this experiment1 
and also to continue using the          
8overhead0 launching apparatus for a few
 more flights4 ,everything being in     
readiness1 the burners were lighted and 
#gj seconds were consumed in raising a  

steam pressure of #abj pounds1 at which 
pressure the aerodrome was launched4 ,it
 started straight ahead1 dropping not   
more than a foot1 and flying on an      
absolutely even keel for about #hjj     
feet1 when it suddenly turned to the    
left and made a short half circle of    
about #ajj feet diameter1 heading for a 
point about #aej feet east of the       
house-boat4 ,when it was about #bjj feet
 from the shore1 a sudden gust of wind  
caught under the ,pnaud tail1 raising   
the rear portion of the aerodrome and   
causing the bow to point down at an     
angle of about #cj degrees4 ,the        
aerodrome kept this angle and struck the
 shallow water only about #bj feet from 
the shore4 ,the aerodrome was           
comparatively uninjured1 and another    
flight would have been made immediately 
but for the fact that by the time the   
aerodrome had been properly inspected it
 was quite late1 and entirely too dark1 
and there would have been danger of     
losing it in the adjacent marshes1 which

 are difficult to traverse even under   
the best conditions of tide and light4  
,the path of this flight is shown by the
 dotted line in ,plate #cd4    ,,june   
#bg--;,,aerodrome ,,no4 #e  ,while the  
preceding tests had been going on with  
,aerodrome ,no4 #f1 such time as could  
be spared for it was spent in getting   
,aerodrome ,no4 #e into proper          
condition4 ,the copper tubing from which
 the boilers for both aerodromes were   
made was greatly inferior to that which 
had been used in previous years1 and as 
this tubing could be procured only by   
having it specially drawn to order in   
,france1 and as it required several     
months after placing an order before the
 p#ada tubing could be delivered1 it was
 necessary to make the best of what was 
already on hand4 ,the copper tubing for 
the boilers which had been used in      
#ahif1 after being carefully annealed   
and filled with fine sand1 could be     
wound into a perfectly smooth helix1    
free from all wrinkles1 indentations1   

and so forth1 on the inner side of the  
coil4 ,but no amount of care1 both in   
annealing and in winding this present   
lot of tubing1 would produce a smooth   
helix1 the tubing being badly wrinkled  
on the inner side of the coil in spite  
of every precaution4 ,these wrinkles1   
however1 were not so much the cause of  
serious trouble as was the fact that the
 tubing was not uniform in quality1 each
 length of it having numerous rotten    
spots which did not always show up in   
the winding1 but which gave way after   
the boiler had been completed and one or
 two preliminary runs in the shop had   
been made with it4 ,while the effect of 
such small things cannot be appreciated 
from merely reading about them1 yet they
 were the cause of the most exasperating
 annoyance and delay1 as no sooner had  
the aerodrome been gotten into what     
appeared to be perfect working order    
than the boiler would break at one or   
more points1 thus causing a delay which 
at the moment would seem to involve not 

more than a few hours1 but before       
everything was again in working order   
would amount to several days4           
,illustration3 ,,pl4 #cd  ,,paths ,,of  
,,flight ,,of ,,aerodrome ,,no4 #f1     
,,june #ac ,,and #bc1 #ahii  ,however1  
after much perseverance1 ,aerodrome ,no4
 #e was put in satisfactory working     
condition1 and on ,june #bg was launched
 with its 8single-tier0 wings and ,pnaud
 tail4 ,the data on settings of wings1  
tail1 etc41 are given on ,data ,sheet   
,no4 #f4 ,after lighting the burners1   
#gj seconds were consumed in raising a  
steam pressure of #abj pounds4          
,immediately upon leaving the launching 
car the aerodrome started to rise with  
its bow elevated to an angle of about   
#ae degrees4 ,it flew straight ahead    
about #hj feet1 when it came backward   
and downward and touched the water about
 #dj feet from the boat4 ,the failure of
 the aerodrome to fly properly was      
evidently due to its not being in proper
 balance4 ,the cause of this lack of    

proper balance was not immediately      
apparent1 but was very soon detected and
 will be discussed later on4    ,,june  
#cj--;,,aerodrome ,,no4 #e  ,after      
several days of incessant rain and      
strong winds1 which prevented an        
experiment1 the weather became brighter 
and the wind quieted down and the       
afternoon of ,june #cj was almost ideal 
for an experiment4 ,at five o'clock     
,aerodrome ,no4 #e1 with 8single-tier0  
wings and ,pnaud tail1 was placed on the
 launching apparatus1 a few minutes     
later the burners were lighted1 and just
 as the propellers started to turn a    
racking noise was heard4 ,upon          
investigation it was found that the     
circulating pump had broken4 ,the break 
was a very small matter and could have  
been repaired in an hour1 but it was    
then too late to repair the damage and  
get a flight before dark1 so the        
aerodrome was reluctantly dismounted and
 the men put to work repairing the      
broken pump4 p#adb    ,,july #a ,,to    

,,july #h  ,the great disadvantage of   
conducting the experiments at a point   
forty miles from the city and the shops 
was felt at all times4 ,workmen1 even of
 the very best class1 cannot be kept    
contentedly at work at a point so far   
removed from their homes1 even by       
bringing them to the city on ,saturday  
afternoon and carrying them back to the 
experimental grounds the following      
,monday4 ,moreover1 it is worse than    
useless to try to get even as much as   
one-third the ordinary amount of work   
done if there is the slightest excuse   
for tightening anchor ropes1 watching   
passing boats1 or wasting time on any of
 the multitudinous small variations from
 their usual routine of life4  ,on ,july
 #g1 ,aerodrome ,no4 #e1 equipped with  
8single-tier0 wings and ,pnaud tail1 was
 made ready for a flight in the         
afternoon4 ,the settings of the wings1  
tail1 etc41 are given on ,data ,sheet   
#f4 ,using the 8overhead0 launching     
apparatus1 the aerodrome was launched   

with a steam pressure of #aae pounds4   
,immediately upon being launched its bow
 rose to an angle of about fifteen      
degrees or more1 and the aerodrome came 
backward and downward and touched the   
water about three or four feet from the 
house-boat4  ,it may be well to recall  
from what has been said in ,part ,i1    
,chapter ,,ix1 that ,aerodrome ,no4 #e  
is the one with the very low thrust     
line1 and in #ahif had its 8separator0  
several centimetres in front of its     
center of gravity4 ,when this aerodrome 
was overhauled just previous to these   
experiments1 the separator was moved    
back to the same relative position as   
that in ,aerodrome ,no4 #f1 so that the 
gradual depletion of the water supply   
during flight would not cause it to     
become light in front of the center of  
gravity4  ,in the launching of          
,aerodrome ,no4 #e1 above described1 it 
showed no tendency to drop immediately  
upon leaving the launching ways1 but on 
the contrary its bow in every case rose 

almost immediately until it was at an   
angle of about fifteen degrees or more4 
,from the photograph 7,plate #ce7 it    
will be noticed that the wings of the   
aerodrome are held down by the          
longitudinal strips1 ,a1 fastened to    
cross-beams attached to the launching   
car4 ,if1 now1 the launching speed is   
too great and the aerodrome tries to    
rise immediately upon being released1   
the front end1 which passes from under  
the launching car before the rear does1 
and is thus free to rise1 will          
immediately rise1 while the rear cannot 
rise until it has passed entirely in    
front of the car1 which being a distance
 of several feet requires an appreciable
 fraction of a second1 during which time
 the bow of the machine has been able to
 rise to quite a steep angle4 ,this has 
the effect of slowing down the aerodrome
 so that it does not get quite the      
proper chance to start on its flight    
with a minimum head resistance4  ,in    
view of the above facts1 it was decided 

to decrease the speed of the launching  
car slightly when using ,aerodrome ,no4 
#e1 so that this matter could be        
thoroughly tested out4  ,illustration3  
,,pl4 #ce  ,,aerodrome ,,no4 #e ,,on    
,,launching-,,ways   p#adc    ,,july #aa
 ,,to ,,july #ad--;,,aerodrome ,,no4 #e 
,the very early morning preceding actual
 sunrise on ,july #aa was undoubtedly as
 calm as it is possible to find2 there  
was absolutely no breeze stirring and   
the water in the river was as smooth as 
glass as far as one could see4 ,the     
anemometer cups were stationary1 the    
wind vane stood absolutely parallel to  
the launching apparatus and everything  
promised a most successful experiment4  
,after mounting the aerodrome on the    
8overhead0 launching apparatus the      
burner was lighted1 and while the steam 
pressure was still rising and the       
propellers were revolving faster and    
faster all the time1 there was a snap   
and they ceased to turn4 ,the fire1     
which was burning fiercely1 ran the     

pressure immediately to #aej pounds4 ,an
 attempt was at once made to start the  
propellers again by giving them an      
initial turn by hand1 it being thought  
possible that a sudden gush of water had
 taken place and1 accumulating in one   
end of the engine cylinder1 had blocked 
the engine4 ,however1 as the engine     
refused to keep the propellers going    
after they were started1 and as the     
pressure was still rising very rapidly1 
the burner was shut off and an          
investigation made4 ,upon removing the  
hull covering1 it was found that the    
connecting rod bearing had broken off   
short near the crank pin of the engine1 
and that it would be necessary to take  
the part to ,washington in order to     
repair it1 as there were no machine     
tools on the house-boat4  ,after several
 days of exceedingly bad weather1 the   
conditions grew more favorable4 ,late in
 the afternoon of ,july #ad1 ,aerodrome 
,no4 #e was again placed on the         
8overhead0 launching apparatus and      

prepared for a trial4 ,after lighting   
the burners1 #ie seconds were required  
to raise a steam pressure of #abj       
pounds4 ,upon leaving the launching     
apparatus the aerodrome went directly   
ahead for a few feet1 but immediately   
commenced to rise1 elevating its bow to 
an angle of #bj degrees by the time it  
had travelled #dj feet4 ,with its bow in
 this position1 it was blown back       
towards the house-boat and a little to  
the right of it1 and1 when within about 
#e feet of the water1 suddenly righted  
itself and started ahead again1 rising  
all the time and reaching a height of   
about #bj feet by the time it had       
travelled #ajj feet4 ,in the meantime   
the bow had again become elevated to an 
angle of about #ae degrees and the      
aerodrome was blown backwards and       
downwards again4 ,just before reaching  
the water it started to right itself1   
but it had descended so that the front  
guy-post was in the water1 thus         
destroying its equilibrium and causing  

it to settle into the water4 ,the path  
of this flight is shown by the peculiar 
,s-shaped line in ,plate #cd4  ,in the  
adjustments preliminary to the above    
trial the ,pnaud tail was elevated to an
 angle of #g-a_/b degrees when the      
aerodrome was stationary in the shop4   
,this excessive elevation1 coupled with 
the fact that the center of gravity was 
also probably a little too far forward1 
no doubt accounts for the erratic       
flight4 ,the data on setting of wings1  
tail1 etc41 are given on ,data ,sheet   
,no4 #g 7,appendix74 p#add    ,,july    
#ai--;,,aerodrome ,,no4 #e  ,after      
several days of exceedingly bad weather 
the conditions were more favorable on   
,july #ai4 ,since the last experiment on
 ,july #ad the coefficient of elasticity
 of the ,pnaud tail had been decreased1 
the rear wings moved back #e            
centimetres1 and the 8float0 so placed  
that the center of gravity of the       
machine was brought to the same position
 it had had on that day1 that is1 #b    

centimetres back of the line of thrust4 
,with this arrangement1 assuming that   
the ,,cp is over the ,,cg1 we should    
have an apparent efficiency of the rear 
wings of #fc4f per cent1 since the      
distance between ,,cpfw1 and ,,cg is    
#gi4g centimetres1 and the distance     
between ,,cprw and ,,cg is #abe4c       
centimetres4 ,with the adjustment of    
,july #ad1 the distance between ,,cpfw  
and ,,cg was #gi4g centimetres1 and the 
distance between ,,cprw and ,,cg was    
#aah4c centimetres1 thus allowing for an
 apparent efficiency of #fg4cg per cent 
for the rear wings4 ,it will be recalled
 that in the unsuccessful flight of     
,july #ad the midrod of the aerodrome   
was inclined at an angle of about #bj   
degrees during most of the time that it 
was in the air1 thus indicating that the
 front wings were lifting               
proportionately more than they should4  
,on ,july #ad the ,pnaud tail had a     
negative elevation of #g #cj1 and it    
required #abdj grammes placed at its    

center to bring it to the horizontal4   
,on ,july #ai the elevation of the tail 
was changed to #e and a weaker spring   
for controlling the elasticity was      
substituted1 so that it required only   
#bjj grammes placed at the center of the
 tail to bring it to the horizontal4 ,a 
rubber band1 of about one-half the      
strength of the upper spring1 was       
attached by means of a cord to the lower
 guy-post and the lower vertical ribs of
 the tail1 so that the tail would be    
elastic both ways4 ,this rubber band was
 in place and acting to help draw the   
tail down when the above measurement of 
the coefficient of elasticity was made4 
,a rubber band connected to the lower   
side of the tail was also used in the   
flight of ,july #ad1 but it was so very 
weak1 compared to the upper spring1 that
 its effect was negligible4  ,the effect
 of this change in the balancing of the 
aerodrome1 and also the more            
considerable effect which the           
coefficient of elasticity of the tail   

has on the balancing1 will be           
immediately noticed from the description
 of the next flight4 ,the data on       
setting of wings1 tail1 etc4 are given  
on ,data ,sheet ,no4 #h4  ,at #c p4 m41 
the wind having died down1 ,aerodrome   
,no4 #e1 equipped with its 8single-tier0
 wings and ,pnaud tail adjusted as      
above1 was placed on the 8overhead0     
launching apparatus4 ,after lighting the
 burners1 one minute and thirty seconds 
were required to raise a steam pressure 
of #abj pounds4 ,immediately upon       
leaving the launching apparatus1 the    
aerodrome started straight ahead1       
dropping about #c feet by the time it   
had gone #ajj feet2 it then rose with   
its midrod at an angle of about #f or #h
 degrees1 regaining its level very      
quickly1 however1 and making three of   
these undulations by the time it had    
gone p#ade #cjj feet4 ,it continued     
straight ahead for another #cjj feet and
 began to circle to the left1 the       
diameter of the first circle being about

 #bjj feet4 ,as soon as it started to   
circle1 it rose with its midrod at an   
angle of about #ae degrees1 and by the  
time it had made its first half turn it 
started to descend1 coming down to      
within #ae feet of the water4 ,as soon1 
however1 as it had completed this first 
turn1 it again rose1 making another half
 circle1 then1 upon the completion of   
this half turn of the second circle1    
descended1 this time to within #aj feet 
of the water1 rising again for the third
 half turn1 but again descending to     
within #b feet of the water at the      
completion of this third circle1 and    
then rising and completing the first    
half turn of the fourth circle4 ,by this
 time1 however1 it had sunk so near to  
the water that the guy-posts caught in  
the tall grass while it was descending  
just before the completion of the fourth
 circle1 thus pulling the aerodrome down
 into the water with the propellers     
still running4 ,the total time the      
aerodrome was in the air was #df        

seconds4 ,the total number of           
revolutions of the propellers was #dhh1 
or at the mean rate of #fcg ,r4 ,p4 ,m4 
,upon examining the aerodrome1 after it 
was recovered1 it was found that there  
were #ibe grammes of water left in the  
separator1 the fire having been put out 
by the aerodrome coming down into the   
water4  ,when the aerodrome first       
commenced to circle during its flight1  
it was noticed that the front wing      
clamps had twisted on the midrod1 the   
left wing being dipped downwards1 and   
the right one1 of course1 being         
elevated1 and the peculiar circling of  
the aerodrome was undoubtedly due to    
this fact4 ,the cause of the wing clamp 
twisting on the midrod was that one of  
the workmen forgot to tighten one of the
 screws of the wing clamp when the wings
 were being adjusted on the aerodrome4  
,but for this unfortunate twisting of   
the wings1 it is probable that the      
flight would have been perfectly        
straight and the distance covered would 

have been considerably greater than it  
was1 the total path traversed being     
about #bfjj to #bhjj feet1 found by     
plotting the path on the coast-survey   
chart and measuring it4    ,,july       
#bg--;,,aerodrome ,,no4 #f  ,as the     
proper balancing of both ,aerodrome ,no4
 #e and ,no4 #f had now been determined 
with reasonable accuracy1 and as much   
more time had already been given to the 
experiments than had been intended1 it  
was decided to dismount the 8overhead0  
launching apparatus at once and         
substitute the 8underneath0 one1 so that
 it could be immediately determined     
whether this newer plan for launching   
the aerodrome by a car supporting it    
from underneath would be suitable for   
use with the large machine4 ,after a    
considerable period of exceedingly bad  
weather1 during which time the change   
was made in the launching apparatus1 the
 weather conditions became more         
favorable on ,july #bg4 ,aerodrome ,no4 
#f1 equipped with 8single-tier0 wings   

and ,pnaud tail1 was mounted on the     
p#adf 8underneath0 launching apparatus1 
and everything was got ready for a      
flight4 ,on lighting the burners1 they  
failed to work properly1 and1 upon      
investigation1 it was found that the air
 valve controlling the air pressure on  
the gasoline tank1 was out of order4    
,while this was being repaired1 the wind
 rapidly increased in velocity and      
became very gusty1 thus endangering the 
aerodrome1 as the wings were very liable
 to be broken by the wind suddenly      
veering more rapidly than the house-boat
 could turn or the turn-table could be  
moved1 and thus striking the wings from 
the side and putting an enormous upward 
pressure on them1 owing to the fact that
 the diedral angle between them gave to 
each wing an elevation of #g-a_/b       
degrees from the horizontal4 ,the       
aerodrome was accordingly dismounted and
 everything kept in readiness for a     
trial1 with the hope that the wind would
 die down1 or at least become steady1   

but it did not do so until after dark4  
,,july #bh--;,,aerodrome ,,no4 #f       
,aerodrome ,no4 #f1 equipped with       
8single-tier0 wings and ,pnaud tail1 was
 launched from the 8underneath0         
launching apparatus4 ,there was a dead  
calm1 the river not showing a ripple2   
the wind vane pointed to the northeast1 
but as the tide was low and the boat was
 aground1 the launching track was       
pointing due south4 ,at #g a4 m4 the    
burners were lighted1 and #hj seconds   
were consumed in raising a steam        
pressure of #abj pounds4 ,everything    
worked perfectly2 the uprights on the   
car1 which initially support the        
aerodrome and upon its being released   
are instantaneously pulled down by      
rubber springs1 as well as the          
disappearing part of the track1 acted   
without the slightest hitch4            
,immediately upon leaving the launching 
apparatus1 the aerodrome depressed its  
bow to an angle of between #c and #d    
degrees and made a direct line for the  

water4 ,at this angle it struck just on 
the opposite side of the channel1 about 
#cjj feet from the house-boat1 and while
 several minor parts1 such as guy-posts1
 were injured no damage of importance   
was done4 ,owing to the difficulty of   
getting through the marsh and recovering
 ,aerodrome ,no4 #f1 it was found       
impossible to make another trial with   
,no4 #e before the wind had increased to
 a prohibitive velocity4 ,the path of   
this flight is shown by the dotted line 
in ,plate #cf4 ,the data on setting of  
wings1 tail1 etc41 are given on ,data   
,sheet ,no4 #i4  ,the last previous     
trial of ,aerodrome ,no4 #f was made on 
,june #bc1 and the balancing at that    
time was evidently correct for the      
settings of the tail which were then    
used4 ,the ,pnaud tail then had an      
elevation of #g-a_/b degrees1 and the   
coefficient of elasticity was such that 
#abdj grammes were required at the      
center of the tail to deflect it to the 
horizontal4 ,in the trial above         

recorded1 on ,july #bh1 the adjustments 
of the wings were practically what they 
were on ,june #bc1 the ,,cg being moved 
forward #a centimetre1 but the ,pnaud   
tail had an elevation of something less 
than #e degrees1 and the coefficient of 
elasticity was such that p#adg #bjj     
grammes placed at the center were       
required to deflect the tail to a       
horizontal4 ,it was not intended that   
the angle of the tail should have been  
less than #e degrees1 but it was found  
that one of the workmen had improperly  
attached the fastening wire1 and had    
considerably decreased the angle4 ,this 
last adjustment of the ,pnaud tail      
should have been the same as that used  
on ,aerodrome ,no4 #e in its flight of  
,july #ai4 ,the ,,cg had purposely been 
moved forward slightly1 but the effect  
of moving the ,,cg forward and at the   
same time decreasing the stiffness and  
angle of the tail was shown by this     
flight4  ,the above trial not only very 
clearly emphasizes the importance of    

carefully determining what the          
elasticity of the ,pnaud tail should be1
 but also emphasizes the fact that even 
the best workmen1 who have had several  
years of experience1 cannot be relied on
 in anything which requires that        
everything be done exactly right and not
 nearly right4    ,,july                
#bi--;,,aerodrome ,,no4 #e  ,the        
aerodrome equipped with 8single-tier0   
wings and ,pnaud tail was launched from 
the 8underneath0 launching apparatus at 
#i a4 m41 #a minute and #cj seconds     
having been required to raise #abj      
pounds steam pressure4 ,the wind was    
from the southeast1 with a velocity of  
#c miles an hour1 and the launching     
track was pointed directly into it4     
,the launching apparatus1 with the      
disappearing track1 worked perfectly1   
and the aerodrome started straight      
ahead1 dropping slightly at first1 but  
immediately regaining its level and     
going ahead1 gradually raising its bow  
to an angle of about #h or #aj degrees1 

and slightly slacking up its speed by   
the time it had gone about #cjj feet4   
,it then made a circle to the left of a 
radius of about #ge feet and started    
back4 ,as soon as it had made this turn 
it regained its level and directly      
regained its speed4 ,but as soon as it  
had speeded up again it elevated its    
bow1 which slackened its speed as       
before4 ,it then again righted itself1  
still going in the same direction and   
crossing the sand-bar on the point of   
the island at a height of about #dj     
feet4 ,as soon as it had crossed the    
sand-bar1 it again made a circle to the 
left with a radius of about #ge feet1   
heading directly for the house-boat1 but
 when it had got back above the sand-bar
 it again circled to the left1 passing  
directly between two tall trees1 and    
barely missing them1 and still circling 
to the left1 when it again reached the  
opposite side of the sand-bar4 ,it1     
however1 kept on circling to the left   
and once more started back towards the  

house-boat1 this time passing to the    
left of the trees and again barely      
missing them1 and completing this1 its  
second1 circle over the sand-bar4 ,it   
then started due north1 heading directly
 for ,quantico1 but by this time        
something had evidently happened to the 
burners as the fire went out1 and the   
propellers gradually slowed up4         
,however1 it kept on towards ,quantico1 
gradually descending on an even keel1   
and came down in the water at a point   
about #ejj feet p#adh from the sand-bar 
and about #ajjj feet from the           
house-boat4 ,the propellers had almost  
ceased turning when the aerodrome came  
down into the water1 and it settled     
almost as quietly as though it had been 
picked up and placed there1 so that no  
damage was done to it4  ,the total time 
that the aerodrome was in the air was   
#fc seconds1 and the total length of    
flight was about #bejj feet4 ,the path  
of this flight is shown by the dotted   
line with the double circle in ,plate   

#cf4 ,the data on settings of wings1    
tail1 etc41 are given on ,data ,sheet   
,no4 #aj4  ,as soon as the workmen had  
had their breakfast1 ,aerodrome ,no4 #e 
was again placed on the launching       
apparatus1 equipped this time with the  
superposed wings and ,pnaud tail4 ,upon 
lighting the burners1 it was found that 
they did not work properly1 a small     
piece of soot having clogged up the tip 
of the vaporizing coil4 ,while this     
trouble with the burners was being      
remedied1 the wind increased to such an 
extent that it was found necessary to   
remove the aerodrome from the launching 
apparatus to prevent its being injured  
by side gusts4 ,as it was ,saturday and 
the wind showed no signs of quieting    
down1 the experiments were discontinued 
until the next week4    ,,august        
#a--;,,aerodrome ,,no4 #e  ,after       
placing the aerodrome on the launching  
apparatus and getting everything in     
readiness for a flight1 upon lighting   
the burners a sudden sheet of flame shot

 out of the smoke-stack and so seriously
 charred three panels of each of the    
rear wings that they had to be removed  
for repairs4 ,the silk covering of the  
wings had been coated with a special    
fire-proofing preparation1 but the      
intensely hot flame1 of course1 charred 
all the silk that it came in contact    
with4  ,by the time that the wings had  
been repaired1 and the defect in the    
burner which caused the accident had    
been remedied1 a severe storm had       
arisen1 making it necessary to remove   
everything to the interior of the boat4 
,while waiting for the weather to become
 more suitable1 a test of the engine of 
,aerodrome ,no4 #e was made inside of   
the house-boat4 ,in this test a steam   
pressure of #adj pounds was obtained1   
giving #fej ,r4 ,p4 ,m4 of the          
round-end1 #ajj-;centimetre propellers1 
which previous tests had shown to mean a
 thrust of #gdhj grammes4 ,as the flying
 weight of the aerodrome was now #ad1ajd
 grammes1 the thrust obtained would     

correspond to a lift of #ec per cent of 
the flying weight1 which was maintained 
in this test for #ij seconds4  ,as the  
,,cg of ,aerodrome ,no4 #e seemed to be 
a little too far forward in the flight  
of ,july #bh1 it was decided to change  
it slightly1 and it was moved back #d   
millimetres4  ,illustration3 ,,pl4 #cf  
,,paths ,,of ,,flight ,,of ,,aerodrome  
,,no4 #e1 ,,july #bi1 #ahii  ,a trial   
run in the house-boat was also made on  
,aerodrome ,no4 #f1 while waiting for   
the weather to become more suitable1    
but1 unfortunately1 the result of this  
test was disastrous4 ,the aerodrome had 
been placed on trestles and p#adi held  
down to the floor by wires fastened to  
the cross-frame4 ,in the midst of the   
test one of the wires slipped1 allowing 
the aerodrome to push forward and thus  
permitting the propellers to come in    
contact with the wires which held it to 
the floor4 ,both propellers were        
entirely demolished and the cross-frame 
was broken off short just at the        

right-hand engine4 ,the disaster was    
entirely due to the carelessness of one 
of the workmen in tightening one of     
these wires1 a further example of the   
extreme heedlessness of workmen1 even in
 the most important details1 which      
concern the very existence of the       
machine4    ,,august #c--;,,aerodrome   
,,no4 #e  ,after the very satisfactory  
trial of ,aerodrome ,no4 #e in the shop 
two days previous1 it was hoped1 now    
that the weather had become suitable1   
that a good flight with the superposed  
wings would be obtained4 ,the aerodrome1
 equipped with these wings1 was         
accordingly placed on the launching     
apparatus and the burners were lighted1 
but they refused to work properly1 a    
steam pressure of only #hj pounds being 
obtained4 ,after much delay the burners 
were finally got to work properly1 but  
the wind had increased in velocity to   
such an extent that it was necessary to 
remove the aerodrome to the interior of 
the house-boat4 ,as the wind continued  

to increase in velocity it was decided  
to make another trial of the aerodrome  
inside of the house-boat4 ,upon doing   
this it was very soon found that there  
was a small leak in the front turn of   
one of the coils of the boiler1 and the 
steam from this played directly against 
the burner1 causing it to work          
intermittently4 ,a new coil was         
substituted1 and after some adjustment a
 very excellent run was obtained1 the   
steam pressure reaching #acj pounds and 
the propellers making #fed ,r4 ,p4 ,m4  
,in the afternoon the wind quieted down 
and the aerodrome1 equipped with        
superposed wings1 was again placed on   
the launching apparatus4 ,the burners   
were lighted but again refused to work  
properly1 the vaporizing tip being      
stopped up with soot4 ,this caused the  
burner to 8flood10 which sent a sheet of
 flame through the stack and burned the 
rear right wing4  ,a new wing was       
substituted1 the burner tip was cleaned 
out and everything was again put in     

readiness for a flight4 ,upon lighting  
the burners1 #a minute and #eh seconds  
were required to raise #abj pounds steam
 pressure4 ,the underneath launching    
apparatus1 with the disappearing track1 
worked perfectly1 the aerodrome dropping
 slightly1 but going straight ahead4    
,it1 however1 continued to descend for a
 distance of about #ajj feet1 the bow   
being elevated about #e degrees4 ,the   
bow then became horizontal1 the         
aerodrome rising slightly at the same   
time1 but going only about #ej feet     
farther1 when it again started to       
descend slightly1 and finally settled   
gently on the water between #cjj and    
#ejj feet from the house-boat1 with its 
bow elevated about #c degrees4 ,there   
was a hiss as the hull touched the      
water1 showing that the fire was still  
burning and making it p#aej improbable  
that the failure of the flight was due  
to lack of power4 ,the data on settings 
of wings1 tail1 etc41 are given on ,data
 ,sheet ,no4 #aa4  ,the speed of the    

launching car1 one foot in front of the 
point at which the aerodrome was        
released1 was twenty feet a second1 as  
shown by the carbon record sheet carried
 by the launching car and moved in front
 of a tuning fork which had been set in 
vibration4  ,the aerodrome1 being       
uninjured in the previous flight1 was   
again placed on the 8underneath0        
launching apparatus1 and before         
attaching the wings a short run was made
 in order to see that everything was in 
proper working condition4 ,as everything
 seemed to be all right1 the wings and  
tail were immediately adjusted for      
another trial4 ,as the bow was slightly 
elevated in the previous trial1 it was  
thought best to bring the ,,cg a little 
farther forward1 and this was           
accordingly done4 ,as the aerodrome also
 seemed to drop slightly in leaving the 
launching car in the above trial1 the   
tension of the launching springs was    
slightly increased so as to increase the
 velocity at the moment of release4     

,just as the sun was setting the        
aerodrome was again launched1 #a minute 
and #cj seconds having been required to 
raise #abj pounds steam pressure1 but   
the pressure was rising very rapidly at 
the moment of launching4 ,there was an  
absolutely dead calm prevailing1 the    
river being as smooth as glass4 ,the    
launching apparatus1 with the           
disappearing track1 worked perfectly4   
,immediately upon being released the    
aerodrome went straight ahead1 with its 
midrod horizontal1 but gradually glided 
downward as though the wings had very   
little lifting power1 and settled in the
 water about #bjj feet from the         
house-boat4 ,the velocity of the        
launching car1 #a foot before the       
aerodrome was released1 was #bb feet a  
second1 as shown by the carbon record   
sheet4  ,in the above trials of the     
superposed wings1 the conditions of the 
wind and of the aerodrome were certainly
 as favorable as could be expected4     
,there was as much power being furnished

 by the engine as had been furnished in 
the previous flights with the           
8single-tier0 wings1 and the balancing  
of the aerodrome was exceedingly good4  
,the superposed wings1 unquestionably1  
had a fair trial and proved inferior to 
the 8single-tier0 ones1 for they had a  
supporting surface of #b4ge square feet 
to the pound1 whereas with the          
8single-tier0 wings there was           
approximately #b square feet to the     
pound4 ,the decreased lifting power of  
the superposed wings seems to be another
 confirmation of the results of the     
,allegheny experiments with the         
8plane-dropper40#dj  ,as more time had  
already been given to these tests than  
it seemed well to p#aea spend on them at
 that time1 owing to the pressure of the
 work of construction for the large     
machine1 it was deemed best to          
discontinue them for the time being1 and
 as soon as time could be found for it1 
to construct a set of wings with        
superposed surfaces1 using only two     

surfaces and making their distance apart
 at least equal to or greater than their
 width4  ,it will be remembered that the
 prime object in making these tests was 
to obtain data for use in the balancing 
of the large aerodrome and in           
constructing a launching apparatus for  
it4 ,the chief deductions drawn from    
them were3 ,first3 ,that it would be    
best to construct the first set of wings
 for the large machine on the           
8single-tier0 plan1 and later to make a 
set of superposed ones1 should further  
experiments with new designs develop a  
type of superposed surfaces which gave  
as good lifting power as the            
8single-tier0 ones4 ,second3 ,that the  
proportioning of the coefficient of     
elasticity of the ,pnaud tail should be 
given as careful attention as the       
setting of the wings4 ,third3 ,that the 
8underneath0 launching apparatus was    
equally as good as the 8overhead0 one1  
and that both worked as well as could be
 desired2 and1 fourth1 that while short 

periods of calm weather might be        
expected during some part of the day on 
a portion of the days of each month1 yet
 the most favorable conditions were more
 apt to be met with between the first   
break of day and the actual rising of   
the sun1 or from an hour preceding      
sunset until darkness actually came4    
,it will be noted that while            
considerable delay was experienced in   
making these tests1 nearly all of it was
 due to the very delicate adjustments   
required in the power-generating        
apparatus of the aerodrome1 but it      
should also be noted that when these    
adjustments were accurately made the    
models operated exceedingly well1 and   
could be depended upon to give good     
flights of sufficient duration to permit
 a careful study of their action while  
in the air4  ,in the experiments of     
,june #bg and ,july #g1 above described1
 the aerodrome immediately after leaving
 the launching apparatus began to rise  
with its midrod pointed upward at an    

angle of about #ae degrees4 ,from ,data 
,sheet ,no4 #f1 which gives in detail   
the important data as to the settings of
 the wings1 the elasticity of the ,pnaud
 tail1#da etc41 we note that the tail   
had a negative angle of #g-a_/b degrees1
 and that the spring which held it at   
this angle was of such a stiffness that 
it required #abdj grammes placed at its 
center of figure to depress it to the   
horizontal4 ,it will also be noticed    
that the position of the front and rear 
p#aeb wings relative to the center of   
gravity of the machine was not the same 
as that which existed at the time of the
 very successful flights of #ahif1 as   
shown by ,data ,sheet ,no4 #a of ,no4   
#e1 ,may #f1 #ahif4 ,when the elasticity
 of the tail was adjusted before making 
this test it was thought that it was    
made the same as in the experiments of  
#ahif1 though accurate data as to the   
exact amount of this elasticity had1    
unfortunately1 not been kept4  ,a slight
 change had also been made in the method

 employed of attaching the ,pnaud tail  
to the machine4 ,in #ahif the tail was  
attached to the machine by means of a   
flat piece of wood 7hickory7 which had  
been steamed and bent to the proper     
extent to cause the rudder to have a    
negative angle of about #e degrees1 but 
no accurate note was made of its angle  
or stiffness1 so that in #ahii no data  
were available as to exactly what the   
angle had been or how stiff the spring  
was4 ,owing to the fact that wood not   
only warps and twists1 but also that any
 piece which has been steamed and bent  
gradually loses a certain amount of its 
curvature1 it was decided in #ahih to   
change this method of attaching the     
tail1 the wooden spring being replaced  
by a coiled steel spring attached to an 
upper guy-post and connected to the tail
 by a bridle wire fastened to the center
 of figure of the tail4  ,after the     
experiment of ,july #g1 #ahii1 a lower  
spring1 consisting of small rubber      
bands1 was connected by a wire to the   

lower part of the rudder and fastened to
 the guy-post1 thereby more nearly      
reproducing the conditions obtained when
 using a wooden spring1 which1 of       
course1 tends to return the rudder to   
its normal position when it is displaced
 in either direction4 ,after attaching  
this lower spring to the rudder1 the    
experiment of ,july #ad was made1 and it
 was found that the aerodrome still flew
 with its midrod pointed upward at a    
very steep angle4 ,it was1 therefore1   
felt certain that the upper spring on   
the rudder was too stiff1 and that it   
should not require so much as #abdj     
grammes to bring it to the horizontal4  
,this spring was1 therefore1 replaced by
 a weaker one1 and the angle of the     
rudder was also decreased until it had a
 negative angle of only #e degrees and  
required only #bjj grammes placed at its
 center of figure to bring it to the    
horizontal4 ,from the description of the
 flight of ,july #ai1 it will be seen   
that these changes immediately corrected

 the tendency of the aerodrome to point 
its nose upward at such a sharp angle1  
and it will be later seen that after a  
further slight adjustment the flight of 
,july #bi was made1 in which the proper 
balancing was obtained and the aerodrome
 made a good horizontal flight4  ,after 
these preliminary tests with the        
8overhead0 launching apparatus1 it was  
dismounted and the 8underneath0 one     
substituted and the experiments of ,july
 #bh1 #bi and ,august #c were made4     
,everything connected with this         
8underneath0 launching apparatus worked 
perfectly from the start and four       
flights of the aerodromes were made     
using it4   ,illustration3 ,,pl4 #cg    
,,experimental ,,forms ,,of ,,superposed
 ,,surfaces1 #ahih1 #ahii 7,,see ,,also 
,,plates #fd ,,and #fe7   p#aec  ,it    
will be recalled that in 8,experiments  
in ,aerodynamics0 ,mr4 ,langley made    
tests of the soaring speed1 etc41 of    
surfaces when superposed4 ,in many of   
his experiments with rubber-driven      

models1 he also employed superposed     
surfaces4 ,during the summer of #ahih   
several forms of superposed surfaces1 of
 a proper size for use on the           
steam-driven models ,nos4 #e and #f1    
were constructed and were tested under  
as nearly as possible the same          
conditions as would exist when used on  
the aerodrome1 by mounting the surfaces 
on the whirling-table and measuring     
their soaring speed1 lift1 drift1 etc41 
to determine just what arrangement of   
surfaces gave the greatest lifting      
effect with the least resistance4 ,two  
of the forms which were tested are shown
 in ,plate #cg1 ,figs4 #a and #b1 and   
,plates #fd and #fe4 ,at the conclusion 
of these tests1 it was decided to       
construct a set of surfaces on the plan 
shown in ,plates #fd and #fe1 and to    
have them ready for use on either of the
 models ,nos4 #e and #f4 ,these surfaces
 were taken to ,chopawamsic ,island in  
,april1 #ahii1 when all of the other    
aerodromic material was first carried   

there4 ,it was planned to make some     
tests with them to determine whether or 
not it would be best to use superposed  
surfaces on the large aerodrome or to   
follow the plan of 8single-tier0 ones1  
which had the great advantage of having 
already proved their worth in the       
successful flights of the models4 ,on   
,august #c1 ,aerodrome ,no4 #e1 equipped
 with these superposed surfaces1 was    
launched4 ,it will be noted from ,data  
,sheet ,no4 #aa that the superficial    
area of the superposed surfaces was     
considerably greater than that provided 
by the 8single-tier0 ones1 and on the   
assumption of the same efficiency per   
unit of surface in both cases1 the      
aerodrome should have soared at a less  
speed and required less power when using
 the superposed surfaces4 ,the results  
obtained1 however1 were just the        
reverse1 the aerodrome being unable to  
sustain itself when using the superposed
 surfaces1 whereas with the             
8single-tier0 ones it was evident that a

 slight excess weight might easily have 
been carried without preventing the     
aerodrome from soaring properly4 ,while 
it was felt that these tests were not   
entirely conclusive as to the superior  
lifting power of the 8single-tier0      
surfaces1 yet as the engine builder was 
constantly promising1 each time with    
increased emphasis1 that he would within
 less than a fortnight deliver the      
engine for the large aerodrome1 and that
 it would develop even more power than  
the specifications called for1 it was   
deemed best to cease the experiments    
with the models and concentrate all     
effort on the completion of the large   
aerodrome frame and the construction of 
a set of 8single-tier0 supporting       
surfaces for it4 ,it was recognized from
 the first that the 8single-tier0       
supporting surfaces lacked the rigidity 
which could be secured by the truss     
construction afforded by the superposed 
plan1 yet these models1 which were the  
only machines in the history of the     

world that had ever flown successfully1 
had been equipped with 8single-tier0    
surfaces2 and the experience so dearly  
bought during the long p#aed years of   
development of these models had taught  
the very valuable lesson that in work of
 this kind where we have no margin on   
anything1 but everything has to be      
calculated on the 8knife-edge0 basis1 it
 is an exceedingly unwise thing to      
introduce any modification from what has
 been proved to be satisfactory1 unless 
such modification is absolutely         
necessary4  ,the principal object in    
building the one-eighth size model of   
the large aerodrome1 as mentioned in the
 first part of this chapter1 was to     
determine by actual experiment whether  
the new form of 8underneath0 launching  
apparatus1 which had just been designed1
 was likely to prove as satisfactory as 
the original 8overhead0 type1 which had 
been used in the successful flights of  
the models in #ahif4 ,yet after it was  
completed this aerodrome was found so   

very strong and stiff1 even though      
roughly constructed by merely tying the 
joints of the tubing together with wires
 and soldering over the joints1 that it 
was decided to equip it with power1 if a
 suitable form of power could be found  
which could be easily applied4 ,just at 
this time liquid air as a motive power  
was attracting considerable attention   
all over the country1 and attempts were 
made to procure a small power plant for 
operation by liquid air4 ,after devoting
 considerable time to the matter it was 
found impossible to do anything with it 
just at that time1 as the liquified air 
could not be obtained in ,washington1   
and one of the chief experimenters in   
,new ,york1 who had been given a        
commission to make certain experiments  
at his plant1 so continuously delayed   
beginning them that it was found        
necessary to give up the idea4          
,however1 after the completion of the   
tests of the launching apparatus some   
experiments were made in flying the     

model as a kite4 ,for this purpose a    
mast twenty feet high was constructed   
and so arranged that it could be mounted
 at the center of a small power launch4 
,the model aerodrome was flown by a cord
 connected to it by a bridle1 the cord  
passing over a swivel pulley on top of  
the mast and down into the boat1 whence 
it could be played out or hauled in as  
occasion required4 ,by heading the      
launch into the wind it was possible to 
secure sufficient relative velocity to  
cause the model to support itself and a 
number of tests were made in this way4  
,it was found that when the bridle was  
attached at the point at which the      
propellers would deliver their thrust1  
had they been in use and driven by      
power1 the model flew exceedingly well1 
maintaining its equilibrium even during 
very strong gusts4 ,owing to the rolling
 produced by waves from the large boats 
which were continually passing in the   
part of the river where these tests were
 made1 the power launch was often in    

danger of being upset by its tall mast2 
and finally1 when the tests were just   
reaching the point where accurate       
information was being obtained on the   
balancing of the model1 a sudden rolling
 of the boat caused the mast to snap off
 while the model was in the air4 ,before
 it could be picked up from the water a 
passing boat had swamped it and it was  
lost in the river4 p#aee  ,although the 
model was1 as has been said1 rudely     
constructed and1 therefore1 did not     
represent a serious loss1 yet the       
pressure of the more important          
construction work for the large machine 
prohibited the construction of another  
rough model for continuing these kite   
experiments1 which it was felt could not
 at best be more than approximate       
indications of the general stability of 
the machine under practical conditions4 
p#aef    ,,chapter ,,iv  ,,house-,,boat 
,,and ,,launching ,,apparatus  ,the use 
of a house-boat seemed to ,mr4 ,langley 
so indispensable in former years in     

making open-air tests of the models that
 he decided from the outset1 though     
advised by the writer against doing so1 
to use the same plan on a much larger   
scale in connection with the large      
aerodrome4 ,aside from its supposed     
utility as a convenient and apparently  
safe place from which to launch the     
aerodrome1 the house-boat was valuable  
as a portable workshop for making       
necessary repairs and as a temporary    
storehouse for the apparatus1 thereby   
saving much packing and unpacking4 ,it  
also provided sleeping quarters for the 
workmen4  ,it was early seen that this  
plan would require a boat at least #fj  
by #dj feet1 which could be built only  
at a large initial cost4 ,but as the    
experience with models had so firmly    
convinced ,mr4 ,langley that it was     
necessary not only that the aerodrome be
 launched over the water1 but also at a 
considerable height above it1 and from a
 station that commanded all points of   
the compass1 he decided to adopt this   

plan for the large aerodrome1 and       
designs for such a boat were accordingly
 made in the latter part of #ahih4  ,in 
order to insure the completion of this  
house-boat by the time the aerodrome was
 expected to be ready for trial1 it was 
built under contract4 ,immediately after
 its delivery in ,may1 #ahii1 work was  
begun on the superstructure which       
carried the launching track4 ,this      
superstructure was a considerable       
undertaking1 involving a turn-table     
weighing about #ae tons1 supported on a 
double circular track1 and this track in
 turn was supported entirely from the   
side walls of the house to avoid having 
columns in the middle of the floor4     
,from the photographs1 ,plate #ch1      
,figs4 #a1 #b and #c1 it will be seen   
that the entire superstructure was      
supported by three trussed girders      
extending across the boat above the roof
 and carried by vertical posts built    
into the side walls of the house4 ,the  
turn-table was #dh feet square and the  

launching track carried by it was #e    
feet gauge by #hj feet long4            
,illustration3 ,,pl4 #ch  ,,fig4 #a4    
,,fig4 #b4  ,,fig4 #c4  ,,house-,,boat  
,,and ,,launching ,,apparatus1 #ahii    
,in making tests of the models1 it had  
been the practice to carry the main body
 of the aerodrome up a ladder to the    
upper works of the boat1 the wings being
 also carried up in the same manner4 ,as
 the large aerodrome was expected to    
weigh at least #fdj pounds1 of which    
#cej pounds would be the steel frame    
with its undetachable parts1 such as the
 engine and its appurtenances1 it was   
seen that something more effective than 
a ladder would need to be provided for  
getting the aerodrome from the interior 
of the boat to the launching track p#aeg
 above4 ,it was therefore decided to    
place the upper works of the boat rather
 nearer the rear end than the front1    
thus leaving a space over the front end 
of the house through which a large      
trap-door might be cut in the roof1 and 

it was thought that in this way the     
aerodrome might be passed up to the     
launching track by the use of suitable  
ropes and pulleys4 ,the upper works were
 so arranged1 and a sliding trap-door   
was provided in the roof1 but more      
intimate knowledge of the difficulties  
of handling so large and heavy a frame  
made it certain1 even before the        
aerodrome was ever placed upon the      
house-boat1 that it would be impossible 
to transport it to the upper works by   
passing it through the trap-door4 ,a    
different plan was then resorted to4 ,a 
very large door was constructed at the  
rear end of the house1 through which the
 completely assembled frame could be    
carried in a level position and placed  
upon a large raft1 consisting of a      
lattice flooring over pontoons1 moored  
at the rear end of the boat1 as clearly 
seen in ,plate #ch4 ,in order to raise  
the aerodrome frame from the raft to the
 upper works1 a large1 but light1 mast  
and boom1 with suitable stays were      

provided4 ,as the wings1 when mounted in
 their proper position on the aerodrome1
 would be interfered with by such a     
mast1 the mast and boom were so devised 
as to be capable of rapid erection and  
dismounting1 only five minutes being    
necessary for either operation4 ,in     
,plate #ch the mast and boom are seen in
 position in ,fig4 #c1 while in ,figs4  
#a and #b they have been dismounted4    
,the construction of the launching track
 and car was begun in ,november1 #ahii1 
but their completion was long delayed1  
as they were frequently put aside for   
the more immediately important parts of 
the work4 ,moreover1 the arrangement of 
the struts and clutch of the launching  
car depended entirely on the form and   
dimensions of the frame of the          
aerodrome1 which could not be entirely  
decided until a proper engine had been  
secured and tested in the frame to      
determine what modifications of it were 
necessary4 ,in the spring of #aijb1     
however1 the launching car was entirely 

finished and a number of tests of the   
large engine were made in the shop with 
the frame mounted in position on the    
car4  ,from the description of the      
8overhead0 launching apparatus 7,part   
,i1 ,chapter ,x7 which had proved so    
successful in the tests of the models1  
both in #ahif and in the later          
experiments of #ahii1 it will be        
recalled that the essential features of 
it were a track and a light car with    
three hinged struts which extended below
 the body of the car1 and against which 
suitable co-acting bearing points       
attached to the frame of the aerodrome  
were tightly drawn by means of a clutch 
which gripped a special fitting fastened
 to the aerodrome frame near the central
 point of its length4 ,after the engine 
of the aerodrome had been started and   
got to running at full speed1 the car   
was released and moved forward along its
 track by the combined force of the     
thrust of the propellers and the pull of
 the coiled launching springs4 ,just    

before the car reached the forward end  
of the track1 a cam at this point caused
 the clutch to open and release p#aeh   
the aerodrome1 which immediately dropped
 slightly1 as it had purposely not quite
 reached a speed sufficient to cause it 
to soar4 ,this slight drop of the       
aerodrome1 even if it were only a       
fraction of an inch1 made it possible   
for the hinged struts1 against which it 
had been held by the clutch1 to be      
folded up by their special springs      
against the floor of the car1 thus      
leaving the aerodrome free in the air   
without danger of entanglement4  ,the   
struts referred to above were three in  
number1 two being placed near the rear  
and one at the center of the front of   
the car4 ,the use of three points of    
support had the advantage of furnishing 
a rather rigid foundation against which 
the frame could be tightly drawn by     
means of the clutch-hook without risk of
 straining it4 ,in designing the        
8underneath0 launching apparatus1 which 

was very thoroughly tested in the       
experiments with the models in the      
summer of #ahii1 the plan of having     
three struts with the aerodrome drawn   
tightly against them by means of a      
central clutch-hook was continued with  
most satisfactory results4  ,when the   
position of the struts on this launching
 apparatus had been changed so as to    
permit it to be used for the            
quarter-size model1 it was found1 in    
making shop tests of the engine with the
 aerodrome mounted on the launching car1
 that1 owing to the greater vibration   
produced by the gasoline engine1 the    
three points of suspension did not hold 
the model in a sufficiently rigid       
manner4 ,it became necessary1 therefore1
 to use four struts1 the two rear ones  
being left as before1 and the single one
 in front being replaced by two         
interconnected ones arranged similarly  
to those in the rear4 ,after making this
 change no difficulty was found in      
holding the aerodrome rigidly against   

the struts1 and this modification was   
therefore immediately introduced in the 
designs for the large launching car     
which was already under construction4   
,illustration3 ,,pl4 #ci  ,,method ,,of 
,,attaching ,,guy-,,wires ,,to          
,,guy-,,posts ,,to ,,relieve ,,torsional
 ,,strain  ,experience1 both with models
 #e and #f1 and with the quarter-size   
model1 had also demonstrated the        
necessity of providing some means       
whereby the aerodrome frame would be    
relieved of the torsional strains       
produced upon it by a side wind striking
 the under surface of the wings when the
 aerodrome was mounted on the car       
preparatory to a test4 ,the means for   
preventing these torsional strains in   
the case of the models1 when 8overhead0 
type of launching car was used1 has been
 described in ,chapter ,x of ,part ,i4  
,however1 with the 8underneath0 type of 
launching car1 a different means was    
necessary4 ,a plan1 in which outriggers 
projected from the body of the car and  

wires running from these outriggers up  
to the main ribs of the wings1 with     
means for releasing the wires just      
before the car reached the end of the   
track1 was used with the 8underneath0   
car in the tests of models #e and #f in 
the summer of #ahii1 but the outriggers 
were frequently deranged by the sudden  
stopping of the car at the end of the   
run and they were replaced by a simpler 
arrangement4 ,in this plan the torsional
 strains were relieved by providing1 at 
the forward and rear ends p#aei of the  
car1 smaller hinged uprights furnished  
in their upper part with a small slot   
into which a pin projected from the     
bottom of the forward and rear          
guy-posts1 respectively4 ,the guy-wires 
from wings being connected to the lower 
ends of the guy-posts the torsional     
strain produced by a side wind was      
immediately transmitted from the wings  
through the guy-wires to the guy-post1  
whence it was transmitted to the car    
itself1 and thus prevented from acting  

on the metal frame of the aerodrome1 as 
shown in ,plate #ci4 ,these additional  
short struts for taking up the torsional
 strain were first added to the small   
launching car in #aija1 and in the      
succeeding tests made with the          
quarter-size model no trouble of any    
kind was indicated as likely to be      
caused by them4 ,as it was these extra  
struts which were directly responsible  
for the accident in the launching of the
 large aerodrome ,october #g1 #aijc1 at 
the time of its first trial1 and        
possibly also for that on ,december #h1 
#aijc1 at the time of the second trial1 
special attention is here called to     
them4  ,the length of travel which could
 be provided for the launching car in   
the case of the large aerodrome1 as well
 as in that of the models was           
necessarily very limited1 owing to the  
fact that the track had to be           
constructed on the top of the house of  
the boat4 ,it was therefore necessary1  
in order that the aerodrome might attain

 a speed sufficient for soaring before  
being launched1 to keep the weight of   
the launching car as small as possible1 
a given spring tension being capable of 
accelerating a given mass a definite    
amount in a given length of travel4     
,with a heavier launching car the spring
 tension would have to be increased4    
,moreover1 since the blow which would be
 struck when the car was suddenly       
stopped at the end of the track1 would  
depend on its mass as well as its       
velocity1 there was an additional reason
 for trying to keep the weight of the   
car as small as possible4  ,while it was
 found perfectly feasible to keep the   
weight of the launching car for the     
model low enough for practical purposes1
 in designing the launching car for the 
large aerodrome it was only by          
eliminating all flooring of the car and 
providing merely a box frame with       
necessary cross-braces1 that its weight 
was kept within what appeared reasonable
 limits4 ,even then the blow which it   

would strike when it reached the end of 
the track was found by calculation to be
 exceedingly formidable4  ,referring to 
the drawings of ,plate #dj1 ,figs4 #a1  
#b and #c1 it will be seen that the     
large launching car consisted           
essentially of two parallel longitudinal
 side members #f inches deep by #a4e    
inches thick by #ai feet long1 connected
 by three main sets of cross-members3   
one set near the rear1 at the point at  
which the rear struts for supporting the
 aerodrome were mounted2 a second rather
 heavier set about the middle of its    
length1 at the point where the strut    
which carried the clutch-hook was       
mounted2 and a third near the front1 at 
the point where the front struts were   
mounted4 ,projecting from the forward   
end of each of the p#afj longitudinal   
side members were piston rods1 on which 
were mounted leather-cup pistons1 which 
co-acted with buffer cylinders fixed at 
the extreme front of the track to absorb
 the blow when the car reached them at  

the end of its travel4 ,the car was     
supported on each side by means of four 
hangers 7,figs4 #d and #e7 which carried
 grooved wheels having ball-bearings and
 running on a steel track consisting of 
flat plates fastened on the side of the 
timbers of the launching track4 ,on the 
extreme lower point of these hangers    
were small guide pulleys1 so placed as  
to be just below and out of contact with
 a guard rail on the side of the        
launching track1 thus preventing any    
possibility of the launching car being  
raised from the track either during its 
forward motion or by a side wind        
striking underneath the wings4          
,illustration3 ,,pl4 #dj   ,aerodrome   
8,a40  ,general ,plan  ,details of      
,launching ,car4  7,details #a_/c ,full 
,size7  ,,general ,,plan ,,and ,,details
 ,,of ,,launching-,,car  ,illustration3 
,,pl4 #da  ,,fig4 #a4  ,,fig4 #b4       
,,fig4 #c4  ,,aerodrome ,,on            
,,launching-,,car  ,illustration3 ,,pl4 
#db   ,aerodrome 8,a0  ,details of      

,clutch ,post for ,launching ,car4      
,scale #a_/c ,full ,size  ,,details ,,of
 ,,clutch ,,post ,,for ,,launching-,,car
  ,illustration3 ,,pl4 #dc  ,,front     
,,end ,,of ,,track ,,just ,,preparatory 
,,to ,,launching ,,aerodrome  ,on the   
large launching car the arrangement of  
the struts against which the bearing    
points of the frame were tightly drawn  
by the clutch was similar in all        
respects to that used on the model car1 
there being only slight differences in  
details4 ,the details of the uprights on
 which the bearing points of the        
aerodrome frame rested are clearly shown
 in ,figs4 #f1 #g1 #h1 and #i of ,plate 
#dj4 ,from the photographs 7,plate #da1 
,figs4 #a1 #b1 and #c7 which show the   
large frame mounted on the launching    
car1 the general arrangement of the     
struts and the clutch-hook can be       
readily seen2 and from ,plate #db1      
,figs4 #a1 #b1 and #c1 which show in    
detail most of the important features of
 the clutch-post and its clutch1 a very 

good idea of the size of the different  
parts may be had by observing that the  
distance from the fulcrum of each half  
of the hook to the pin by which it was  
connected through the universal joint to
 the vertical rods is five inches4 ,as  
previously stated1 this clutch-hook     
gripped the lower pyramid and pulled the
 bearing points of the frame firmly     
against the forward and rear struts of  
the launching car1 and in launching the 
aerodrome the triggers arranged on the  
bottom of the car1 which at the proper  
time pull on the vertical rods and      
thereby force the two halves of the     
clutch-hook apart1 are so arranged that 
they strike a cross-beam at the front   
end of the track one inch before the    
triggers1 which keep the struts from    
being pulled down by their springs1     
which tend to fold them up and force    
them down against the car4 ,the         
triggers1 which prevent the struts from 
being folded down1 strike a cross-beam  
in the track one foot before the buffer 

pistons on the end of the car begin to  
enter the buffer cylinders at the end of
 the track1 and1 consequently1 one foot 
before the folding prop1 which supports 
the front end of the track1 is knocked  
out by the car striking a special       
trigger which allows this folding prop  
to swing forward when the front end of  
the track folds down to insure that the 
aerodrome will not become entangled with
 the car1 even though the aerodrome be  
not quite up to soaring speed at the    
moment of launching4 ,the manner in     
which this front end of the track folds 
down can be very readily seen by        
comparing ,plate #dc with ,plate #ie of 
,chapter ,,xii1 the former showing the  
front end of the track in horizontal    
position1 with p#afa the aerodrome at   
the extreme rear end just preparatory to
 launching1 and the latter showing the  
front end of the track folded down with 
the hinged prop standing outward in its 
downward path and the aerodrome just    
launched4 ,these photographs will be    

more particularly referred to later1 but
 attention is here called to them so    
that the description immediately        
following may be more easily understood4
  ,although this method of launching the
 aerodrome seemed to ,mr4 ,langley1 both
 theoretically and from the experience  
with the models1 to be a satisfactory   
and feasible plan1 there were two very  
important respects in which it seemed   
from the very first open to objection4  
,in the first place1 it was necessary   
that the aerodrome should be launched as
 nearly at its soaring speed as         
possible1 because either an excess or   
deficiency of speed interfered to some  
extent with the equilibrium of the      
machine4 ,so many factors were involved 
in the determination of what this final 
velocity should be that it seemed almost
 impossible to be sure of the results   
until at least one test of the aerodrome
 had been made4 ,in the second place it 
was not known whether the rapid         
acceleration of the car would seriously 

interfere with the equilibrium of the   
aviator4  ,in reference to the first    
question it was1 of course1 known that a
 freely falling body acquires a speed of
 #cb feet per second at the end of the  
first second after having fallen a      
distance of #af feet4 ,it was proposed  
to launch the aerodrome at approximately
 #ce feet per second2 and1 since the    
distance over which the car would pass  
in acquiring this speed was             
approximately #fj feet1 the rate of     
acceleration would1 of course1 be less  
than that for a freely falling body4    
,the conditions in the two cases1       
however1 are quite different4 ,in the   
case of the freely falling body there is
 the constant force of gravity which    
causes the acceleration4 ,in the case of
 the aerodrome the car is initially     
standing still but ready to be acted    
upon by the combined force of the thrust
 of the propellers and the tension of   
the springs4 ,the propeller thrust is   
approximately #dej pounds at the moment 

of releasing the car1 while the spring  
tension adds approximately #djj pounds  
more pull1 giving a total pull of #hej  
pounds acting on the car at the start4  
,the weight of the aerodrome including  
the aeronaut being approximately #hej   
pounds1 and the weight of the car being 
approximately #dej pounds1 the total    
weight to be accelerated is #acjj       
pounds4 ,the resistance of the car and  
the aerodrome is zero at the moment the 
car is released1 and increases          
approximately as the square of the      
velocity until it reaches approximately 
#cjj pounds at the soaring speed of the 
aerodrome2 while on the other hand the  
spring tension decreases uniformly from 
#djj pounds at the start to             
approximately #gf pounds at the end of  
the track1 and the thrust due to the    
propellers decreases from #dej pounds at
 the start to approximately #bej pounds 
at the moment of launching4             
,consequently1 it is in a general way   
clear that the rate of acceleration of  

the aerodrome and car decrease1 probably
 in a geometric ratio1 the rate of      
acceleration p#afb at the moment of     
launching the aerodrome being much less 
than that of a freely falling body4     
,since so many factors enter into the   
problem no confidence was felt in       
calculations as to what the rate of     
acceleration would be4 ,it was1         
therefore1 decided to determine it      
experimentally at the same time that    
tests were made on the car to determine 
what spring tension would be necessary  
to enable the aerodrome and car to      
acquire soaring speed by the time they  
reached the end of the track4  ,it was  
obviously impossible to make this       
initial test with the aerodrome mounted 
on the launching car1 as the aerodrome  
would certainly wreck both itself and   
the car were it allowed to remain       
fastened when the car was stopped at the
 end of the track4 ,it was1 therefore1  
decided to make the tests by mounting on
 the car boards which would have a head 

resistance equal to that of the         
aerodrome4 ,in order to minimize as much
 as possible the blow due to the car    
striking the buffers at the end of the  
track1 the car had been made as light as
 possible4 ,on this account it was felt 
to be unwise to risk adding to it a     
weight of #hej pounds to represent the  
aerodrome1 and supplying an additional  
spring tension to represent the thrust  
of the propellers1 as the total effect  
of the added weight and the added pull  
would certainly completely demolish the 
car4 ,by calculation it was found that  
the omission of the #hej pounds weight  
of the aerodrome and the spring tension 
to represent the thrust of the          
propellers would practically            
counterbalance each other2 and that if  
sufficient spring tension were provided 
to cause the car1 with the light boards 
representing the head resistance of the 
aerodrome1 to reach the soaring speed by
 the time it arrived at the end of the  
track1 it would be safe to assume that  

this spring tension would be sufficient 
for use in launching the aerodrome4     
,the method of measuring the final speed
 of the launching car for the models    
consisted in fastening a strip of smoked
 paper to the launching car in such a   
position that it was drawn past a stylus
 fastened to the end of a vibrating     
tuning fork placed at the end of the    
track4 ,this had proved perfectly       
successful1 but it gave a record merely 
of the final speed attained by the car  
at the moment of launching the          
aerodrome4 ,in the case of the large    
aerodrome it was desirable to have a    
record of the speed of the car during   
the first few feet1 and also at several 
other points in its travel down the     
launching track1 and the more numerous  
these points the better4 ,short strips  
of copper were accordingly placed every 
twelve inches along the length of the   
track1 and these were connected by a    
wire to one terminal of a small electric
 battery4 ,mounted on the car1 in such a

 way that it would be drawn across these
 contact strips1 was a copper brush     
arranged to make continuous contact with
 another wire stretched along the track1
 this second wire being connected to the
 other terminal of the electric battery 
and having in its circuit the magnet    
which actuated a pen on a chronograph4  
,since the rate of revolution of the    
chronograph barrel was known1 the p#afc 
distance between the marks which the    
magnet would cause the pen to make when 
its circuit was closed by the brush on  
the car passing across the contact      
strips on the track would give correct  
measures of the time consumed by the car
 in passing over each twelve inches of  
its travel4 ,upon test1 however1 it was 
found impossible to get the chronograph 
magnets to work rapidly enough to       
respond to the very rapid opening and   
closing of the circuit after the car had
 passed over the first one-quarter of   
its length of travel4 ,as a large part  
of the slowness of action seemed to be  

due to the weight of the fountain pens1 
they were replaced by small glass tubes 
drawn out to a fine point and containing
 a small amount of ink4 ,these seemed1  
however1 to be still too heavy to       
respond to the rapid closing of the     
circuit unless the contacts were made   
unduly long4 ,the contacts were finally 
made three inches long and placed only  
every three feet along the track1 but   
just as these contacts were completed   
and placed in position the clock-work of
 the chronograph itself became deranged4
 ,before it could be repaired1 the tests
 were discontinued1 as everything was in
 readiness for the boat to proceed down 
the river where the actual tests in free
 flight were to be made4 ,tests of the  
final speed of the car were1 however1   
made by the tuning-fork method1 and the 
springs were adjusted until their       
tension was sufficient to cause the car 
to attain a speed of thirty-five feet a 
second at a point three inches in front 
of the point at which the aerodrome     

would be released from the car4   p#afd 
,,chapter ,v  ,,construction ,,of       
,,frame ,,of ,,large ,,aerodrome  ,the  
general plan for the large aerodrome was
 never a matter of uncertainty4 ,at the 
time when the first general designs were
 made there had been in the history of  
mankind only one type of machine1 that  
of the steam-driven ,langley models1    
which had proved capable of flight for  
any considerable distance4 ,furthermore1
 the selection of this type had been the
 result not of sudden fancy or of purely
 theoretical consideration1 but of years
 of the most careful experimentation1 in
 the course of which nearly every       
conceivable style of machine had been   
tested with some form of power4 ,it     
would have been worse than folly1       
therefore1 if the one clear path had    
been left to seek some unknown way4  ,it
 was fully realized from the first1     
however1 that the increase in size alone
 would make necessary in the design for 
the large aerodrome a great many        

modifications from the designs of the   
steam-driven models4 ,it was not        
possible here1 as in nearly every other 
kind of structure1 simply to magnify    
uniformly the parts and proportions of  
the small machine in order to obtain a  
successful large one4 ,this is          
particularly true in the case of the    
aerodrome1 because the rapid increase of
 weight in the larger structure is out  
of all proportion to the increase in    
strength1 while it is very desirable    
that the more expensive machine which is
 designed to carry a human being shall  
be relatively even stronger than the    
easily replaced model4 ,this problem of 
increasing size without sacrificing     
strength and stability1 it was known    
from the beginning1 would be encountered
 in a particularly difficult form in    
designing the frame of the large        
machine1 and was to be solved not by the
 discovery of some new and wonderfully  
strong material1 but by improvements    
both in the general plan and the details

 of the machine4 ,here1 as is often the 
case1 it was not the large changes in   
the design but the improvements in small
 and sometimes seemingly unimportant    
details which demanded the most careful 
consideration and1 as a whole1          
contributed most to the final result4   
,for this reason1 as well as because the
 large changes1 when pointed out1 are   
usually easily understood1 the present  
chapter is for the most part a          
description of the improvement of       
details4  ,from the experience gained in
 the construction of the frames of the  
several steam-driven models1 it was     
decided that the frame for the large    
aerodrome must consist essentially of   
two principal parts4 ,first1 a rigid    
backbone was required1 extending from   
the point of attachment of the front    
wings to the point of attachment of the 
rear wings2 and this backbone1 for      
convenience designated p#afe the 8main  
frame10 must support the second         
principal part1 the 8transverse frame10 

which formed a cross with the main      
frame1 and at the ends of which the     
propellers were mounted4 ,while it was  
necessary that this transverse frame    
should have considerable rigidity and   
strength in a vertical direction1 yet   
its main strength and stiffness was     
required in the horizontal plane for    
withstanding the thrust of the          
propellers4 ,it had been possible to    
construct the frames of the later       
steam-driven models stiff enough1 and at
 the same time light enough1 by the use 
of properly proportioned steel tubing1  
but calculation very soon showed that in
 order to secure sufficient rigidity for
 the frame of the large aerodrome and at
 the same time keep the weight within   
the permissible limit1 it would be      
necessary to depend very largely on     
guy-wires and to use tubing only for    
forming the struts against which the    
guy-wires should act4 ,but this         
obviously introduced a new series of    
problems4 ,the extensive system of      

guy-wires necessary would add materially
 to the head resistance of the          
aerodrome1 and this might conceivably be
 so great as to require more propulsive 
power than would be required for a frame
 heavier but unincumbered by the head   
resistance of the wires4 ,it became     
necessary to consider these problems1   
but no data were accessible from which  
the head resistance could be computed   
with any confidence4 ,the coefficient of
 resistance for a cylindrical body      
moving through the air in a direction   
perpendicular to its length may in      
general be taken as one-half that of a  
flat body of the same cross-section2 but
 it was thought very certain that1 owing
 to the fact that tightly stretched     
wires are in constant vibration when the
 aerodrome is in the air1 the resistance
 of the wires must be considerably      
greater than would be calculated from   
treating them as cylinders having a     
coefficient of #j4e4 ,unfortunately1 no 
data on the resistance of vibrating     

wires were at hand4 ,before proceeding  
with the designs for the guying of the  
frame1 therefore1 the following brief   
series of tests was made in ,november1  
#ahih1 on the whirling table1 in order  
to learn approximately the resistance   
that the proposed system of guy-wires   
for the large aerodrome would offer3    
,,measurements ,,of ,,the ,,resistance  
,,of ,,guy-,,wires1 ,,using ,,frame     
,,attached ,,to  8,,balance40           
,,resistance ,,of ,,frame ,,without     
,,wires4   ,frame consists of3 #d tubes1
 #a cm4 diameter1 #ad4e cm long2 #b     
tubes1 #a  cm4 diameter1 #da cm4 long2  
#b tubes1 #a cm4 diameter1 #aja cm4     
long4   ,revolutions of   ,velocity of  
,resistance4   ,calculated resistance   
turn-table per   frame4 ,feet           
,grammes4         of frame4    minute4  
per minute4      r4           ,grammes4 
#f4ge            #fjh          #aa4e    
#ad4b       #i4ge            #hgg       
#cd4j             #bi4f      #ab4j      
#ajhj          #ea4h             #dd4h  

#af4ce           #adge          #ig4j   
#hc4h      #ai4ge           #agge       
#acd4j            #aba4c      #bb4g     
#bjde         #afh4j            #afa4b  
#be4e            #bbij         #bje4j   
#bjb4j    ,,resistance ,,of ,,frame     
,,with #a,,st ,,set ,,of ,,wires4       
,first set of wires3 #af wires1 #j4f mm4
 diameter1 #ajb cm4 long2 #f  wires1    
#j4f mm4 diameter1 #db cm4 long4        
,revolutions    ,velocity of            
,resistance   ,resistance    ,calculated
  of turn-table  wires4 ,feet   of frame
    of wires4     resistance  per       
minute4    per minute4  and wires4      
,r#arr#a4     of wires4                 
,grammes4                   ,grammes4   
,r#a4      #i4ge           #hgg         
#dg4e         #ac4e          #h4hh      
#ab4j           #ajhj         #gc4e     
#ba4g         #ac4dg     #ac4ge         
#abcg         #ic4e         #be4e       
#ag4fe     #ag4be          #aeej        
#add4j         #cg4j         #bg4g      
#bj4be          #ahbb        #ahg4j     

#de4e         #ch4d     #bb4ej          
#bjbe        #baf4j         #dg4e       
#dg4d     #bb4hge         #bjfj         
#bbe4j         #eb4j         #di4j      
#bd4ef          #bbae        #bej4j     
#ef4e         #ef4g    ,,resistance ,,of
 ,,frame ,,with #b;,d ,,set ,,of        
,,wires4  ,second set of wires3 #ae     
wires1 #a4b mm4 diameter1 #ajb cm4 long2
 #b wires1 #a4b mm4 diameter1 #db cm4   
long4    ,revolutions   ,velocity of    
,resistance   ,resistance    ,calculated
  of turn-table  wires4 ,feet   of frame
     of wires4    resistance   per      
minute4   per minute4  and wires4       
,r#brr#b4    of wires4                  
,grammes4                   ,grammes4   
,r#b4      #i4be          #hcc          
#ed4j         #bf4e         #ae4ce      
#i4ce          #hda         #ee4j       
#bg4j         #ae4d     #aa4c           
#ajah         #hb4j          #cf4ge     
#bb4fe     #aa4e          #ajce         
#hb4j          #ce4be        #bc4d      
#ac4j          #aagj        #ajd4e      

#dc4j         #bi4i     #ac4ae          
#aahe        #aje4j          #db4e      
#cj4fj     #af4g          #aeje         
#afj4j          #ei4j         #di4e     
#af4ge         #aeaj        #afj4j      
#eh4j         #di4i     #ai4e           
#agee        #aif4j          #fd4j      
#fg4d     #ai4g          #aggj          
#bjc4j          #fi4e         #fh4e     
#ba4fj         #aide        #bcf4j      
#gg4j         #hb4f     #ba4fe          
#aiej        #bcg4j          #gg4ge     
#hc4b     #ba4ge         #aieg          
#bce4j          #ge4e         #hc4g     
,,resistance ,,of ,,frame ,,with #c;,d  
,,set ,,of ,,wires4   ,third set of     
wires3 #ae wires1 #b mm4 diameter1 #ajb 
cm4 long2 #b wires1  #b mm4 diameter1   
#db cm4 long4    ,revolutions           
,velocity of  ,resistance  ,resistance  
,calculated  of turn-table  wires4 ,feet
   of frame    of wires4     resistance 
per minute4   per minute4  and wires4   
,r#crr#c4    of wires4                  
,grammes4                    ,grammes4  

,r#c4      #i4be          #hcc          
#fe         #cg4e            #be4b      
#aa4ee         #ajdj            #ia     
#dc4e            #ci4ce    #aa4ee       
#ajdj           #aja         #ec4e      
#ci4ce    #ae4be         #acge          
#afj         #ge4j            #fh4g     
#ah4a          #afcj           #bjc     
#hf4e            #if4f    #ai4be        
#agce           #bba         #ib4j      
#aji4e    #ai4be         #agce          
#baf         #hg4j           #aji4e     
#bj4fc         #ahfj           #bcg     
#ij4e           #abe4h  ,the last column
 of these tables is calculated for a    
coefficient of form equal to #j4e1 which
 has been found to be approximately     
correct for a rigid cylindrical body4   
,these tables are not sufficiently      
extensive to determine accurately the   
exact resistance that wires of various  
sizes will offer at given velocities1 or
 to serve as the basis for the deduction
 of formul1 and were not made for that  
purpose4 ,however1 from the above data1 

and the curves plotted in ,plate #dd1 it
 will be seen that some unexpected      
results were obtained4  ,illustration3  
,,pl4 #dd  ,,resistance ,,of ,,wires    
,,at ,,given ,,velocities   p#afg       
,these results are fairly well          
summarized in the following general     
statements3 ,first1 that the coefficient
 of resistance increases to some degree 
as the size of the wire is decreased2   
second1 that in the case of wires of the
 size which it was expected to use1 and 
at approximately the soaring speed of   
the aerodrome1 the resistance is        
certainly not greater than #ge per cent1
 and more probably less than #ej per    
cent of the resistance encountered by a 
flat surface of the same projected area2
 third1 that the coefficient of         
resistance did not seem to be increased 
by the vibration of the wires4 ,on the  
contrary1 it was noted during the       
experiments that when they reached a    
speed which just caused them to 8sing10 
there was a marked diminution in the    

resistance4 ,this statement is made1    
however1 with some reserve1 for it is   
probable that the singing of the wires  
was due to vibration in the horizontal  
plane1 and it is not definitely known   
what the effect would be of vibration in
 the vertical plane4  ,to make the very 
extensive experiments necessary to      
determine these propositions            
conclusively would have required much   
more time than could at this period be  
spared from the actual constructional   
work on the aerodrome4 ,nevertheless1   
the data did seem to indicate that it   
was at least not unwise to employ the   
extensive system of guying which had    
been planned in order to give the       
necessary strength to the frame of the  
large aerodrome4 ,this plan of          
construction was1 therefore1 definitely 
adopted1 and as a result of later       
experience the system of guying was     
still further extended4  ,as the        
transverse frame had to be made         
comparatively rigid in order to prevent 

undue binding of the bearings of the    
transmission and propeller shafts1 it   
was necessary to make it intrinsically  
stronger and1 therefore1 heavier in     
proportion to its size than the main    
frame4 ,the main frame1 although        
requiring great strength to enable it to
 withstand the strains1 both torsional  
and direct1 which were imposed upon it  
by the weights which it supported1 did  
not need excessive rigidity1 and could1 
indeed1 be distorted an appreciable     
amount without danger of any serious    
effect on the action of the wings or    
rudder2 but even a small amount of      
distortion in the transverse frame might
 easily cause such friction at the      
bearings of the shafts as to absorb     
fifty per cent or more of the engine    
power4  ,in the photographs1 ,plates #de
 to #dh1 which show the actual condition
 of the frame on ,january #ca and       
,february #a1 #aijj1 the letters ,a1 ,b1
 ,c1 ,d1 ,e1 ,f1 ,g1 ,h and ,i designate
 parts of the main frame1 ,a and ,h     

being the rear and front midrods1       
respectively1 to which the wings were to
 be attached4 ,b and ,i are curved      
extensions of the starboard main tube1  
the port main tube being exactly        
similar1 and ,c1 ,d1 ,e1 ,f and ,g are  
cross-tubes which connect the midrods to
 the port and starboard tubes4 ,r is the
 front main tube of the transverse      
frame1 the rear main tube being exactly 
similar1 and both being connected to the
 main tubes of the main frame where they
 cross them4 ,the ends of the main tubes
 of the p#afh transverse frame are      
joined together by the 8bed plates0 ,l1 
which are of ,i-beam section1 and have  
mounted on their outer faces the        
bearings which support the propeller    
shafts4 ,at ,v are bevel gears mounted  
on the propeller shafts1 which are      
driven by co-acting bevel gears1 ,m1    
mounted on the outer ends of the        
transmission shafts1 ,o1 the latter     
being at this point firmly supported in 
bearings mounted on the inner faces of  

the bed plates and steadied by the      
intermediate bearings1 ,n4 ,the two     
transmission shafts are seen to be not  
in line1 the rotary cylinder engine that
 was then under construction requiring  
this arrangement4 ,the bed plates1 ,l1  
are further stiffened by the brace      
tubes1 ,k1 and the transverse frame is  
braced against the thrust of the        
propellers by the tubes ,j4 ,the four   
tubes1 ,p1 unite at their upper ends to 
form what was designated as the upper   
8pyramid10 and the wires1 ,s and ,t1    
radiate from its apex to the rear and   
front1 respectively1 of the main frame4 
,the lower 8pyramid10 on the under side 
of the frame1 also has similar wires    
running fore and aft4 ,the main portions
 of both frames are further strengthened
 by their sub-frames1 which merge       
together1 and the main tubes of the main
 frame are individually stiffened in the
 vertical plane by a minor system of    
guying4 ,the scales shown in the        
photographs are calibrated in metres4   

,it is to be particularly noted that the
 midrod1 which had heretofore formed the
 backbone of the main frame1 was now    
made to act merely as a means of        
attaching the wings to the frame1 the   
main strength of the frame being        
furnished by the two parallel fifty     
millimetre tubes which extended the     
entire length of the frame and which1   
reinforced by the guy-wires1 formed a   
truss not only more rigid transversely1 
but also many times stronger in its     
ability to resist torsional strains than
 could be secured by a single tube of   
equal weight4 ,in this plan of          
constructing the main frame1 the        
pyramids constituted a very important   
element1 for with the guy-wires arranged
 as they were it was impossible for any 
portion of the frame to experience a    
stress which was not transmitted in some
 way to the pyramids4 ,in the frame1 as 
here shown1 these pyramids were formed  
of tubes #ae mm4 in diameter1 #j4e mm4  
thick1 stiffened against buckling under 

the end pressure by means of the        
cross-braces1 which united them near    
their midpoints4 ,while the sole        
function of the upper pyramid was to    
serve in the system of guying the frame1
 the lower pyramid not only served a    
similar purpose1 but also provided a    
means for holding the aerodrome to the  
launching car in the process of         
launching it1 the clutch-hooks gripping 
around the short horizontal tube at the 
apex of the pyramid and thus drawing the
 8bearing points0 of the machine firmly 
against the uprights on the car4 ,in    
fact1 the particular arrangement of     
these pyramids was largely determined by
 this necessity for providing means for 
holding the aerodrome to the launching  
car1 and the form which seemed best     
suited to the purpose was duplicated on 
the upper side of the frame4            
,illustration3 ,,pl4 #de  ,,frame ,,of  
,,aerodrome ,a1 ,,january #ca1 #aijj    
,illustration3 ,,pl4 #df  ,,frame ,,of  
,,aerodrome ,a1 ,,january #ca1 #aijj    

,illustration3 ,,pl4 #dg  ,,frame ,,of  
,,aerodrome ,a1 ,,february #a1 #aijj    
,illustration3 ,,pl4 #dh  ,,frame ,,of  
,,aerodrome ,a1 ,,february #a1 #aijj    
p#afi  ,the 8bearing points0 were not   
attached to the frame at the time these 
photographs were taken1 but are seen    
leaning against the scales in the       
foreground of ,plate #df4 ,their        
position on the frame will be more      
clearly seen in later photographs1 where
 it will be noted that they were made   
use of in the more elaborate system of  
guying which was adopted4  ,while1 in   
general1 the frame at this time seemed  
to be reasonably stiff and strong1 yet  
it was subjected to a very thorough test
 by supporting it at different points   
and suspending from it weights to       
represent the various parts1 such as    
engine1 aviator1 wings1 rudder and so   
forth1 the deflections which were       
produced by these weights being         
carefully noted4 ,it was further tested 
by subjecting it to vibratory strains1  

such as it would be likely to meet in   
actual use4 ,after this the whole frame 
was tested against torsional strains1   
such as would be caused by the wind     
twisting one set of wings more than the 
other4 ,as a result of these tests it   
was decided that the frame should be    
strengthened as far as it was possible  
to do so without greatly increasing the 
weight1 which even now was found to be  
rapidly increasing beyond what had been 
calculated as permissible4 ,the main    
guy-wires were replaced by heavier and  
stronger ones1 and while these were     
found to add somewhat to the stiffness  
of the frame1 yet something more seemed 
necessary to insure safety4  ,the delay 
in securing the engine1 which had been  
contracted for with a guarantee that it 
would be delivered in ,february1 #ahii1 
had become so serious and had delayed   
the completion of the frame to such an  
extent that the question of building an 
exact duplicate of the large machine1   
but of one-quarter its linear dimensions

 was being carefully considered at this 
time1 and it was decided to make no     
further changes in the guying of the    
large frame until after the small one   
was built4 ,on account of its smaller   
size changes could be more readily and  
cheaply made on it1 and the advantages  
of different methods of guying could be 
just as well studied4 ,later1 when this 
was completed1 it was found that1 with  
the same system of guying that had been 
used in the larger frame1 the model was 
so very stiff that it did not require   
any further strengthening1 the smaller  
scale1 of course1 accounting for the    
difference4 ,what was thought to be the 
best system to follow in strengthening  
the frame of the large machine was1     
however1 first tried on the smaller one1
 and it was found that for a very slight
 increase in weight a very great        
increase in strength could be obtained4 
,this change in the system of guying    
consisted essentially of building a     
8trestle0 of tubing at a point on the   

upper side1 midway between the pyramid  
and the rear end of the frame4 ,one of  
the former sets of guy-wires which      
passed to the rear of the frame was then
 replaced by a set which started at the 
foot of the rear tubes of the upper     
pyramid1 passed over and was fastened to
 the trestle1 and from there passed to  
the rear end of the frame at the points 
where the longer guy-wires from the     
pyramid had formerly been attached4 ,the
 p#agj guy-wires on the lower side of   
the frame1 at the rear1 were            
correspondingly changed so that the     
upper and lower systems should be       
similar1 the wires which started from   
the main tubes at the foot of the       
pyramid passing to the bearing points1  
and from there to the rear end of the   
frame4  ,in order to keep the main frame
 of the large aerodrome as short as     
possible1 it had originally been planned
 to make the distance between the center
 of pressure of the front wings and the 
center of pressure of the rear equal to 

five metres4 ,when these same           
proportions were followed in the        
quarter-size model1 it was found that it
 brought the rear wings so close to the 
propellers that their lifting effect was
 certain to be interfered with by the   
blast of air created by the slip of the 
propellers4 ,it was therefore decided   
that all things considered it would be  
best to increase this distance between  
the wings1 even though this involved an 
increase in weight1 partly on account of
 the increased amount of tubing1 and    
still more on account of the guy-wires  
which it would be necessary to add in   
order to make up for the weakness due to
 increased length4 ,the large aerodrome 
frame was accordingly lengthened #b4e   
feet 7#gf4b cm471 and the guy-wire      
system was changed to that clearly shown
 by the photographs of ,july #aj1 #aijb1
 ,plates #di1 #ej and #ea1 the black    
cross-lines on the background being #ej 
centimetres apart4 ,from an inspection  
of these photographs it will be seen    

that two sets of guy-wires were carried 
from the upper and lower pyramids1      
respectively1 towards the rear of the   
frame1 the first set being carried to   
the main tubes at the foot of the       
8trestle0 and the bearing points1 and   
the second set to these same main tubes 
at the second cross-tube4 ,the sets of  
wires which started from the feet of the
 pyramids were carried over the         
8trestle0 on the upper side and the     
bearing points on the lower side1 and   
both joined to the main tubes at the    
rear cross-tube4 ,additional            
cross-guy-wires for stiffening the frame
 sideways were added in each of the     
squares formed by the junction of the   
cross-tubes with the main tubes4 ,a     
secondary system of truss guy-wires     
running over short guy-posts attached to
 the tubes of the main frame also       
contributed to the strength and rigidity
 of the whole4  ,although the pyramids  
had shown no signs of weakness1         
nevertheless1 because of increased      

strains due to the lengthening of the   
main frame1 it was thought advisable to 
make them stronger4 ,instead of the     
#ae-mm4 tubing1 which had formerly been 
used1 #be-mm4 tubing of the same        
thickness was therefore substituted1 and
 additional cross-braces were added1 as 
will be seen from the photographs1 and  
from the scale drawings in ,plates #eb1 
#ec and #ed1 which show the aerodrome as
 it was when completed4 ,the numerals   
attached to these drawings refer to the 
detail drawings shown in later plates4  
,illustration3 ,,pl4 #di  ,,guy-,,wire  
,,system1 ,,july #aj1 #aijb             
,illustration3 ,,pl4 #ej  ,,guy-,,wire  
,,system1 ,,july #aj1 #aijb             
,illustration3 ,,pl4 #ea  ,,guy-,,wire  
,,system1 ,,july #aj1 #aijb             
,illustration3 ,,pl4 #eb  ,,scale       
,,drawing ,,of ,,aerodrome ,a1 ,,end    
,,elevation  ,illustration3 ,,pl4 #ec   
,,scale ,,drawing ,,of ,,aerodrome ,a1  
,,side ,,elevation  ,illustration3 ,,pl4
 #ed  ,,scale ,,drawing ,,of ,,aerodrome

 ,a1 ,,plan  ,in order to secure the    
proper adjustment of the guy-wires1 not 
only of the frame but of many other     
parts1 notably the wings1 propellers and
 rudder1 it was necessary to use a large
 number of turn-buckles4 ,as almost     
every wire p#aga required at least one1 
and in some cases two turn-buckles1 the 
weight represented by this single item  
rapidly became so formidable as to      
require serious attention4 ,in the      
construction of the models1 it had been 
necessary to employ some special        
turn-buckles in connecting the guy-wires
 of the wings to their guy-posts in     
order to secure the minute adjustment of
 the wires necessary to prevent the     
wings from being warped and distorted by
 unequal and improper adjustment4 ,these
 turn-buckles had been made in the      
,institution shops1 as the very lightest
 ones which could be secured in the     
market were from ten to twenty times as 
heavy as it was necessary for them to be
 to provide ample strength4 ,in the     

construction of the large aerodrome1    
however1 the large number required1 and 
the desire to complete the machine at   
the earliest moment1 made it advisable  
to procure the turn-buckles1 if         
possible1 from outside sources1 and a   
very careful search was accordingly made
 among the various dealers4 ,after much 
delay some bronze turn-buckles were     
secured which were very much stronger   
for their weight than any others on the 
market1 but upon testing them it was    
found that while they weighed #de       
grammes1 their average breaking strength
 was only #eic pounds4 ,previous        
experience had shown that turn-buckles  
which would not break under a less load 
than #gej pounds could certainly be made
 to weigh not more than #ah grammes4 ,as
 even at this time it was realized that 
at least #ajj turn-buckles would be     
necessary for the entire machine1 the   
excess weight which the heavy           
turn-buckles would add was felt to be   
absolutely prohibitory1 and the         

construction of steel turn-buckles was  
immediately begun in the ,institution   
shops4 ,these turn-buckles were at first
 made in several sizes1 and while some  
few were at first made 8double ended10  
most of them were threaded at only one  
end1 the other end being provided with a
 swivel-hook1 or eye4 ,they were at     
first made of mild steel1 the           
swivel-hooks1 in fact1 being made of    
wire nails in order to utilize the head 
of the nail as a shoulder without the   
expense of machining rod steel of a size
 large enough to form the shoulder4 ,it 
was found1 however1 that the weak point 
of this type of turn-buckle was the     
swivel end1 and most of those which were
 then on hand were made double ended by 
removing the hook1 tapping a left-hand  
thread into this end of the shank1 and  
fitting a threaded eye-socket in it4    
,the guy-wires themselves were attached 
to the eyes of the turn-buckles and to  
the fittings on the frame by twisting   
loops at the ends of the wires1 and     

although the very greatest difference in
 the strength of a completed guy-wire   
may result from the way in which the    
loops are twisted1 yet1 after much      
training1 the workmen were taught to    
twist these very uniformly1 following   
the plan which can be best understood by
 an inspection of the drawings in ,plate
 #ee which show the loops more clearly  
than they can be described4 ,after the  
loops had been properly twisted1 soft   
solder was run all through the twist in 
order to unite firmly the twists of the 
wire4 ,although special grades of wire  
were found which showed very high       
tensile strength when the wire was p#agb
 tested without having loops formed in  
its ends1 yet it appeared that the      
twisting of these high-grade wires so   
seriously affected them that in the case
 of guy-wires with loops at the ends1   
better final results could be obtained  
by using softer grades of steel4 ,the   
wire which was actually found best1     
after much experiment1 was a good grade 

of ,bessemer steel of a medium hardness1
 which had been 8coppered0 to prevent   
rusting4 ,however1 even with the softer 
grades of steel wire1 it was found that 
there were sometimes hard spots in the  
wire which revealed themselves only upon
 test1 and that when a hard spot        
occurred in the twisted portion where   
the loop was formed1 the final strength 
of the completed guy-wire was sometimes 
only twenty-five per cent of what it    
should be4 ,the precaution was then     
taken to subject each of the completed  
guys to a test strain at least          
twenty-five per cent greater than it was
 calculated the wire would have to stand
 in actual use1 so that no accident from
 defective wires would be likely to     
occur4  ,later on1 however1 much trouble
 was caused by the loops in the ends of 
some of the guy-wires slipping1 owing to
 the giving way of the solder which had 
been run through the joint1 the amount  
of slipping1 while small1 being         
sufficient to alter completely the      

relative stresses on the various wires1 
thus causing distortion of the framework
 itself4 ,in order to avoid this        
difficulty a new method was devised of  
attaching the guy-wires to the          
turn-buckles and to the fittings by     
which they were carried to the frame4   
,this method consisted in threading the 
ends of the guy-wires so that they could
 be inserted directly in the threaded   
ends of the turn-buckles4 ,the wires    
when connected in this way to the       
turn-buckles showed absolutely no slip1 
and the entire system gained greatly in 
strength thereby4 ,the only disadvantage
 which was found in this new method of  
attaching the guy-wires to their        
fittings1 was that if the wire was bent 
very close to the fitting1 it would     
break in the screw thread very easily4  
,but since most of the guy-wires when   
once attached to the machine are always 
tight1 and in fact1 under more or less  
strain1 there was in most cases no      
likelihood of the wires being endangered

 by being bent close to the fittings4   
,since the screw threads1 which it was  
necessary to adopt in this new plan of  
connecting the guy-wires1 had to be very
 much finer than the threads which had  
been used in the turn-buckles previously
 constructed1 it was necessary to make  
new turn-buckles1 the others being too  
thin to permit of their being bored out1
 bushed and re-threaded4 ,the new       
turn-buckles were made of a much higher 
grade of steel1 and probably represent  
very nearly the maximum of strength for 
the minimum of weight possible without  
the use of some of the very much        
higher-grade steels which have recently 
come on the market1 but which are       
exceedingly expensive to work4 ,by means
 of this improved plan of attaching the 
wires1#db it p#agc was found possible to
 gain practically fifty per cent in the 
strength of the entire system of        
guy-wires used on the frame4  ,many     
small changes were from time to time    
made in the various small fittings by   

which the guy-wires were attached to the
 frame1 nearly all of these fittings    
having been originally made of a very   
mild grade of steel owing to the fact   
that it was so very much easier to work4
 ,at the time these fittings were made  
it was constantly expected that a trial 
of the aerodrome would be possible very 
soon1 and it seemed necessary to        
expedite the work as much as possible   
and avoid the delay involved in using   
grades of steel that would have been    
materially harder to work4 ,as is always
 the case in work of this kind1         
retrospect shows many instances where   
what was supposed to be a short cut to  
results actually proved to be the       
longest path1 but the work as a whole   
was remarkably free from imperfect parts
 which necessitated reconstruction4  ,in
 the construction of the frames of the  
models it had been customary to fit the 
tubing accurately at the joints and to  
join it permanently together by brazing1
 as this was not only the lightest form 

of joint that could be made1 but also   
the most expeditious method consistent  
with securing a strength of the joint   
comparable with that of the tubing      
itself4 ,the construction of the frame  
by this method of brazing the joints    
together permanently1 offered1 however1 
several serious drawbacks3 among them1  
that when a tube got injured it was a   
considerable task to replace it1 while  
the brazing of the new tube in place    
required extreme care to prevent the    
frame from being warped when completed1 
as the tube became longer while very hot
 and contracted after the joint had set4
 ,furthermore1 the great heat required  
destroyed to a considerable degree the  
desirable qualities due to the tube     
being 8cold drawn10 a reduction of      
strength of something like #be per cent 
being almost inevitable1 even when the  
brazing was most carefully done4 ,it    
was1 therefore1 decided that in the     
construction of the large machine all of
 the main joints should be made by a    

system of 8thimbles10 and it was planned
 at first to make these thimbles by     
brazing short pieces of steel tubing    
into the proper shapes and angles so    
that they would accurately fit the tubes
 which were to be joined4 ,the          
construction of the thimbles in this    
manner1 however1 seemed to involve an   
excessive amount of work2 and1 as it was
 found that very thin castings of       
aluminum-bronze could be obtained1 which
 would show a tensile strength very     
nearly as great as steel1 it was decided
 to make up patterns for the thimbles   
and cast them of aluminum-bronze4  ,the 
aluminum-bronze castings were obtained  
and properly machined to fit the tubes1 
but when it was attempted to 8tin0 the  
interior walls of the thimbles it was   
found that the solder could not be made 
to stick to the bronze4 ,as a           
considerable amount of work had been    
expended on the machine work of these   
thimbles much time and effort was spent 
in attempting to devise 8fluxes0 p#agd  

and solders which could be made to work 
with the aluminum-bronze1 but the final 
result was that the aluminum-bronze     
thimbles had to be abandoned4 ,they were
 replaced by similar castings of        
gun-metal of a slightly heavier section1
 which at the time were thought to be   
very suitable for the purpose4  ,but1 in
 finally assembling the frame after the 
changes described above had been made1  
steel thimbles1 built up of short pieces
 of tubing1 as had originally been      
planned1 were substituted for the       
gun-metal thimbles4 ,this change was    
made not only because of the great      
increase in strength1 but more          
particularly because many of the        
gun-metal fittings had been imperfectly 
constructed1 so that it was extremely   
difficult to align the frame4 ,the steel
 thimbles1 which were made in the       
,institution shops proved thoroughly    
satisfactory and gave no trouble of any 
kind4 ,many of these thimbles and the   
method of attaching the guy-wire        

fittings to them are shown in ,plates   
#ef and #eg1 as well as in ,plate #ee4  
,,transverse ,,frame  ,it will be       
recalled from the description of the    
models ,nos4 #e and #f1 in ,part ,i1    
that the position of the line of thrust1
 with respect to the positions of the   
center of pressure and center of gravity
 in the vertical plane was1             
theoretically1 very much better in ,no4 
#f than in ,no4 #e4 ,in designing the   
large aerodrome1 it was desired to      
reproduce as nearly as possible the     
relative position of the line of thrust 
with reference to the center of pressure
 and center of gravity which existed in 
,no4 #f1 but for constructional reasons 
it was found impossible to do so4 ,in   
fact it appeared that without seriously 
complicating the construction of the    
frame it was impossible to raise the    
line of thrust with respect to the      
center of gravity materially higher than
 it was in ,no4 #e4 ,in ,no4 #f the line
 of thrust was #ab centimetres above the

 midrod1 this being effected by placing 
the engines some distance from the      
boiler1 and at the extreme ends of the  
transverse frame where they were        
connected directly to the propellers4   
,in the case of the steam engine the    
weight of the engine proper is a        
relatively small portion of the entire  
weight of the power plant1 and it is1   
therefore1 possible to put the engine   
almost anywhere without materially      
affecting the center of gravity4 ,but   
where a gas engine is used the engine   
itself constitutes the greater part of  
the weight of the power plant1 and any  
raising of the engine1 therefore1       
materially raises the center of gravity 
of the whole machine4 ,the line of      
thrust in the large aerodrome was1      
therefore1 practically in the plane of  
the main frame1 and consequently very   
little higher than the center of        
gravity4  ,illustration3 ,,pl4 #ee      
,,frame ,,fittings ,,and ,,guy-,,wire   
,,attachments1 ,,etc4  ,illustration3   

,,pl4 #ef  ,,frame ,,fittings ,,and     
,,guy-,,wire ,,attachments1 ,,etc4      
,illustration3 ,,pl4 #eg  ,,frame       
,,fittings ,,and ,,guy-,,wire           
,,attachments1 ,,etc4  ,the use of one  
engine to drive two propellers mounted  
at opposite ends of the transverse      
frame1 and in a direction perpendicular 
to the crank shaft of the engine1       
necessitates the use of a pair of bevel 
gears between each of the propeller     
shafts and the shafts by which the power
 is conveyed to them from p#age the     
engine shaft4 ,since the efficient      
transmission of power through bevel     
gears requires that they be very        
accurately placed with reference to each
 other1 and maintained very accurately  
in this position while they are at work1
 it was necessary to make the transverse
 frame very rigid1 especially at its    
extreme ends4 ,this was accomplished by 
the use of what were called             
8propeller-shaft bed plates40 ,they are 
designated by the numeral #bg in ,plate 

#ed1 and are shown in detail in ,plate  
#eh as of a very deep ,i-beam section1  
having very narrow flanges top and      
bottom1 the web of the ,i-beam          
furnishing the strength in a vertical   
direction1 while sufficient stiffness   
laterally was obtained from the flanges1
 assisted by the brace tubes1 which     
acted as struts between the bed plates  
and the main tubes of the transverse    
frame4 ,these struts1 while very light1 
added enormously not only to the lateral
 stiffness of the propeller bed plates1 
but furnished for a minimum weight a    
maximum prevention against twisting of  
the plates4 ,the propeller-shaft bed    
plates were originally planned to be    
made of sheet metal with the flanges    
brazed to the web4 ,but at the time that
 they were constructed the pressure of  
the work was so great in the            
,institution shops that it was found    
necessary to have some of the work done 
outside1 and the parties who undertook  
the construction of these bed plates    

were unwilling to attempt to braze them 
up1 and accordingly worked them from    
steel forgings made for the purpose4    
,the expense of this plan of            
construction proved large and           
unnecessary1 as both previous and later 
experience proved that it was not only  
practicable to braze up bed plates more 
complicated in their design than these1 
but that equal strength for equal weight
 could thus be obtained for less than   
one-quarter the cost of constructing    
them from solid forgings4 ,furthermore1 
where such parts are made from the      
solid1 changes which later tests prove  
advisable can frequently not be carried 
out without very serious cost and delay1
 while with the bed plates formed by    
brazing less hesitancy is felt in       
removing parts which are brazed thereto 
and substituting new parts1 or even     
discarding the bed plates altogether and
 substituting new ones4 ,particular     
emphasis is laid on this point for the  
reason that much expense and delay would

 have been avoided had these very       
expensive propeller-shaft bed plates    
been discarded as early as #aija and    
replaced by others which would have     
permitted a considerable strengthening  
of the ball-bearings1 which1 while      
strong enough to stand even more power  
than they were originally designed for1 
were far too weak to be safe when       
working under the greatly increased     
stress due to the very much higher      
engine power which was later used4      
,instead of discarding these bed plates 
then for new ones1 they were            
strengthened by brazing to them         
crescent-shaped pieces1 as shown in the 
drawings and photographs4 ,this         
strengthening was made necessary by the 
larger hole cut in the bed plates for   
the larger bevel gears4 ,the bed plates 
for the engine1 which are later         
described1 besides other bed plates     
which were made for other purposes1 were
 all p#agf formed by the use of sheet   
metal and tubing properly brazed        

together1 and none of them ever gave any
 trouble4  ,in the early photographs of 
the aerodrome frame1 especially that of 
,january #ca1 #aijj1 ,plate #de1 it will
 be noted that the two transmission     
shafts1 which extend from the           
propeller-shaft bed plates towards the  
center1 are not in line1 the port       
transmission shaft being at the center  
of the transverse frame1 while the      
starboard shaft is three inches to one  
side4 ,this arrangement was necessary in
 order to connect the shafts to the     
rotary cylinder engine which was being  
constructed under contract1 and which   
was almost momentarily expected for more
 than a year after its original promise 
of delivery on ,february #bh1 #ahii4    
,later1 when this engine was finally    
found to be a failure1 and the writer   
constructed the engine in the           
,institution shops1 the starboard       
transmission shaft was moved over to the
 center line and the crank shaft of the 
engine1 which was carried through on the

 center line of the transverse frame1   
was then connected directly to the inner
 ends of the transmission shafts4       
,these shafts1 as well as the propeller 
shafts1 were originally constructed of  
steel tubing #a4e inches in diameter and
 #a_/af of an inch thick1 but on account
 of the increased power of the large    
engine it was found necessary to        
increase the thickness of the shafts to 
#a_/h of an inch4 ,difficulty was also  
found with the tubing of which the      
shafts were made4 ,this1 though not     
exactly straight when received from the 
factory1 could be pretty accurately     
straightened in the lathe by exercising 
proper care1 but the moment any real    
strain was put upon it in the           
transmission of power1 it again went out
 of shape and caused serious damage to  
the bearings by whirling1 buckling1 and 
so forth4 ,as the skin of the tubing is 
really the strongest part1 owing to the 
cold-drawing process to which it has    
been subjected1 great care was taken to 

secure shafts which were sufficiently   
straight for use without machining1 but 
it was finally found impossible to rely 
on the unmachined shafts1 and all the   
later shafts for the aerodrome were made
 by getting tubing a sixty-fourth of an 
inch thicker than was calculated to be  
necessary and turning off this extra    
metal in a lathe4  ,illustration3 ,,pl4 
#eh  ,,bedplate1 ,,gears1 ,,etc4        
,suitable flanges and collars were      
brazed to the propeller shafts2 but1 for
 convenience in assembling1 the flanges 
by which the main transmission shafts   
were connected to the crank shaft of the
 engine were at first fastened to the   
shafts by screw-threads1 the threads    
being in the proper direction to cause  
the flanges to jam against the shoulders
 of the shafts when the engine turned in
 its normal direction4 ,this method of  
fastening1 however1 caused serious      
trouble1 owing to the flanges jamming so
 tight that it became impossible to     
unscrew them after they had once been   

used in driving the propellers4 ,the    
usual provisions of keys and key-ways   
adopted in general engineering practice1
 where solid shafts are employed1 were1 
of course1 out of the question1 since   
the shaft would have to be greatly      
increased in thickness throughout its   
entire length p#agg merely to provide   
the extra metal at the small place in   
which the key-ways were formed4 ,taper  
pins either sheared off or very soon    
stretched the holes so badly as to leave
 the parts loose1 and were otherwise    
very unsatisfactory4 ,the method finally
 adopted1 which proved very successful1 
was that of forming integral with the   
couplings shallow internal tongues and  
grooves which fitted corresponding      
tongues and grooves either in the       
exterior surface of the shafts or in    
collars brazed to them at the proper    
point4 ,the form of flange coupling1 in 
which bolts draw the two flanges tightly
 together1 was also a source of         
considerable trouble and delay1 which   

was finally overcome by forming shallow 
tongues and grooves in the faces of the 
flanges1 the tongues taking up the      
torsion and relieving the bolts which   
held the flanges together of all strain 
except one of slight tension4 ,the same 
difficulties experienced in mounting the
 couplings on the shafts were met with  
in connection with the gears1 both on   
the propeller and transmission shafts1  
and were finally obviated in a manner   
similar to that described above4  ,the  
bevel gears originally constructed for  
transmitting the power from the         
transmission shafts to the propeller    
shafts1 were made of case-hardened steel
 and were eight-pitch1 twenty-five      
teeth1 with three-quarter inch width of 
face4 ,the gears were very accurately   
planed to give as perfect a form of     
tooth as possible1 in order to avoid    
loss of power in transmission1 and      
although the manufacturer who cut the   
teeth on them asserted at the time they 
were made that they would not be capable

 of transmitting more than five         
horse-power1 yet they actually did      
transmit considerably more than twelve  
horse-power on each set2 but they were  
not strong enough to transmit the full  
power of the large engine which was     
finally used4 ,the gears that were      
finally used were similarly constructed 
of mild steel which was case hardened   
#a_/fd of an inch deep after they were  
finished1 there being thirty-one teeth  
in the gear on the transmission shaft   
and forty teeth in the one on the       
propeller shaft1 the teeth being        
eight-pitch1 three-quarters of an inch  
face4 ,these light gears proved amply   
strong1 and several times stood the     
strain which they accidentally received 
when one of the propellers broke while  
the engine was under full power1 and    
thus threw the entire fifty horse-power 
over on the other propeller1 which was  
consequently driven at a greatly        
increased speed4  ,plain bronze bearings
 had been used throughout on the model  

aerodromes1 but in the construction of  
the large aerodrome ball-bearings were  
used on all of the propeller and        
transmission shafts1 not only on account
 of the decreased loss through friction1
 but also because ball-bearings can be  
built much lighter than solid bronze    
ones1 and1 furthermore1 do not present  
such great difficulties in lubrication4 
,however1 owing to the limited size     
which it was possible to secure for     
these bearings1 because of their having 
been originally designed for only       
twenty-four horse-power1 and without any
 margin for a later increase of the     
p#agh space in which they had to be     
applied1 they were never really large   
enough for the work they had to do when 
transmitting the full power of the large
 engine4 ,they gave continual trouble1  
and were the source of delay which1     
while it cannot be accurately measured1 
since there were often other causes1 yet
 might be conservatively estimated at   
not less than three or four months4     

,such a delay1 when reckoned in         
retrospect1 can easily be seen to have  
caused an expense which would have      
sufficed for almost any change in the   
bearings1 bed plates1 etc41 had the     
change been made immediately after the  
bearings were found to give trouble4    
,with the better steel which it is now  
possible to obtain for the races of the 
bearings1 and with the high-grade balls 
now obtainable1 the bearings could be   
readily replaced without changing any   
other parts and still be amply strong   
for the work4    ,,propellers  ,both the
 tests on the whirling-table and the    
actual results with the models had shown
 that propellers which were true helices
 formed out of wood were rather more    
efficient than those constructed by the 
use of a hub in which were inserted     
wooden arms1 forming a framing over     
which cloth was tightly drawn4 ,but the 
very great difference in the cost of    
construction and the facility with which
 the latter type could be repaired in   

case of damage--the wooden ones were    
practically of no use if once they were 
much injured---made it seem advisable to
 construct all the propellers for the   
large aerodrome in the manner just      
explained4 ,several pair of small       
propellers had been built on this plan1 
some as early as #ahie1 and one very    
important advantage had been found to be
 possessed by this type besides         
cheapness and facility of repair4       
,wooden propellers of even so small a   
diameter as one metre had been found to 
suffer a quite appreciable bending of   
the blades1 due to the thrust produced  
by them1 even though the blades had been
 made of considerable thickness4 ,in    
planning a propeller #b4e metres in     
diameter for the large aerodrome it was 
seen that in order to make the blade    
sufficiently strong to withstand its own
 thrust it would be necessary to make it
 inordinately thick1 which1 of course1  
would mean a considerable increase in   
weight4 ,in fact1 it was seen that the  

weight of the larger propellers would   
increase practically as the cube of the 
diameter2 which1 for the #b4e-metre     
propeller1 would involve a weight of    
something over fifteen times the weight 
of those one metre in diameter4 ,the    
other type1 which for convenience we    
will call 8canvas covered10 permitted   
the bending moment produced on the blade
 by the thrust to be taken up by        
guy-wires running from the corners of   
the blades to a central post projecting 
from the hub of the propeller1 and it   
was found that in this way a            
considerable saving in weight could be  
effected4 p#agi  ,in ,november1 #ahig1  
in order to obtain by actual test some  
data on propellers1 such as it was      
planned to use on the large aerodrome in
 case it was later built1 it was decided
 to construct one propeller #b4e metres 
in diameter and #a4be-pitch ratio with  
two blades1 each covering the sector of 
#cf degrees on the projected circle4    
,about this same time an engine builder1

 who some years before had made some    
experimental model engines in the       
,institution shops1 proposed to         
construct a gasoline engine for the     
proposed large aerodrome4 ,as past      
experience1 not only with such engines  
but with all other forms of explosive   
motors1 had not been very reassuring it 
was thought best to make brake tests of 
one of the heavier engines which he was 
at this time building1 and at the same  
time make tests with one of these large 
propellers4 ,a first series of tests was
 made at several different speeds1 and  
then a second series was made with the  
engine driving the propeller at the same
 speeds4 ,the engine varied so much1    
however1 in the power developed at any  
speed that the data obtained were of    
little value4 ,as it was also desired to
 learn just how much thrust could be    
obtained from these propellers1 when    
driven by a given horse-power1 a special
 hand car was fitted up to carry the    
engine1 which was connected to a shaft  

on which the propeller was mounted4 ,the
 propeller was raised above the floor of
 the car and projected over the rear end
 of it so as to be as little disturbed  
as possible by the deflection of the air
 currents caused by the car4 ,this car1 
with the engine and propeller1 was      
tested on a track near ,mount ,holly1   
,n4 ,j41 in ,november1 #ahig1 but the   
results were very unsatisfactory4 ,in   
the first place1 the car with the engine
 mounted on it was so very heavy and    
offered such a strong tractive          
resistance that very little speed of    
propulsion could be obtained4 ,in the   
second place1 the engine1 which was said
 to have furnished over six horse-power 
on ,prony-brake tests1 evidently did not
 furnish anything like this amount of   
power at this time4 ,and in the third   
place1 the propeller was evidently far  
too large to permit the engine to run at
 the speed at which it would develop a  
reasonable amount of power unless some  
reduction gearing were interposed       

between it and the propeller4 ,as the   
tests1 for various reasons1 had to be   
made at a great distance from           
,washington1 and the supervision of them
 had to be entrusted by ,mr4 ,langley to
 others1 who either did not understand  
or appreciate the value of obtaining    
accurate data1 it was found             
impracticable to continue them4  ,the   
large propeller used in these tests was 
built without special regard to weight1 
since it was expected that it would be  
subjected to rather rough usage under   
the very sudden strains produced by the 
irregular working of the gas engine4    
,its hub was made of brass tubing1 the  
horns being brazed to rings which were  
slid over a central tube1 the rings     
being finally soldered to the tube after
 the arms had been adjusted to the      
positions which would give the blade the
 correct shape and dimensions4 ,the     
wooden arms were #a4e inches in p#ahj   
diameter at the hub end1 tapering to    
#a4be inches at the end of the blade4   

,the blade was exceedingly stiff as     
regards pressure produced by thrust1 but
 it was found to be considerably        
strengthened and made very much safer   
when guy-wires were added1 in the manner
 explained above4 ,this general type of 
construction was adhered to in all the  
future propellers for the aerodrome1    
though slight modifications1 both as to 
the size of the arms and the number and 
position of the cross-pieces which      
formed the framing of the blade1 were   
adopted from time to time4 ,a pair of   
heavy propellers1 #b4e metre1           
#a4be-pitch ratio1 #cf-;degree blade1   
the hubs of which were formed of brass  
castings1 was1 however1 constructed for 
experimental purposes1 where weight was 
not an important factor4  ,when these   
propellers were designed1 the           
calculations as to their size and the   
horse-power which would be required to  
drive them at a certain speed were based
 on the very incomplete data obtained   
from the various propeller tests        

conducted during the preceding years4   
,when later calculations were made for  
them1 on the data obtained in the more  
accurate tests made in the summer of    
#ahih1 it was found that the power of   
the engines with which it was proposed  
to equip the aerodrome would not be     
sufficient to drive the propellers at   
anything like the speed which the former
 calculations had shown would be        
possible2 and that1 therefore1 either   
the ratio of the gearing between the    
propellers and the engine would have to 
be changed so as to permit the engine to
 run at a very much higher speed than   
the propellers1 or that propellers1     
having either less pitch or a smaller   
diameter1 and possibly both1 would have 
to be substituted for these larger ones4
  ,since it was easier to change the    
propellers then to change the gearing1 a
 new set of propellers was designed     
which were of #b metres diameter1 with a
 pitch ratio of unity1 and with a width 
of blade of only #cj degrees4 ,it was   

calculated that #bj horse-power would   
drive these two propellers at a speed of
 #fdj ,r4 ,p4 ,m41 when the aerodrome   
was flying at a speed of #ce feet per   
second and the propellers were slipping 
about #ej per cent1 this being found to 
be about the speed at which the engines 
might be expected to develop their      
maximum power4 ,as the larger propellers
 having the brass hubs were thought to  
be excessively heavy1 the hubs weighing 
#aj4be pounds each1 and as any change   
either in size1 pitch1 or width of blade
 necessitated a new set of patterns in  
case the hubs were cast1 it was decided 
to construct the new hubs of steel      
tubing4 ,the weight was further reduced 
by decreasing the size of the wooden    
arms to #a-a_/d inch in diameter at the 
hub1 tapering to #a inch at the end of  
the blade4  ,after the engine builder in
 ,new ,york had been unable to fulfil   
his contract on the engine1 and it had  
been condemned1 propeller tests were    
made with the experimental engine built 

in the ,institution shops4 ,these tests 
showed3 ,first1 that the results which  
might be expected from larger propellers
 could be very safely predicted by      
extrapolation from the results of the   
propeller tests of #ahih2 p#aha and1    
second1 that in order to get a thrust   
which would equal fifty per cent of the 
flying weight of the aerodrome it would 
be necessary to use propellers larger   
than two metres in diameter unless a    
very large surplus of power were        
provided4 ,it was accordingly decided to
 make a set of propellers intermediate  
between the two-metre1 unit-pitch ratio1
 thirty-degree blade ones1 and the      
original ones which were two and        
one-half metres1 one and                
one-quarter-pitch ratio1                
thirty-six-degree blade4 ,a set was1    
therefore1 designed two and one-half    
metres in diameter1 unit-pitch ratio1   
and thirty-degree width of blade1 the   
hubs being made of steel tubing brazed  
up in the same manner as the two-metre  

ones1 and the wooden arms of the blades 
being one and three-eighths inches in   
diameter at the hub end1 and tapering to
 one inch at the end of the blade4      
,later1 when the larger engine was      
actually tested in the frame1 the       
inability of the original transmission  
and propeller shafts to stand the extra 
strain caused by the engine starting up 
very suddenly at times1 together with   
the unsatisfactoriness of the           
screw-thread method of fastening the    
gears and couplings to the shafts made  
it necessary to provide new shafts1     
gears1 couplings1 etc4 ,it was then     
decided to change the ratio of gearing  
between the engine and the propellers1  
which had been one to one1 so that the  
engine might run faster and1 therefore1 
permit the use of larger propellers4    
,for constructional reasons the ratio   
chosen was thirty-one to forty1 thus    
making the engine run approximately     
one-third faster than the propellers4   
,in the various tests made of the engine

 working in the frame there were two or 
three instances in which the propellers 
were damaged either by the sudden       
starting of the engine or by their not  
being able to stand the strain to which 
they were subjected by the power        
absorbed1 but in every case such        
breakages were found to be due to       
imperfections of the brazing in the     
joints4 ,while1 therefore1 it would have
 been desirable to make the propellers  
somewhat heavier1 yet since the total   
weight of the aerodrome had been growing
 so very rapidly1 it was felt that this 
need not be done1 as a pair of          
propellers which had stood quite severe 
service in shop tests might reasonably  
be expected to stand the strain of      
actually propelling the aerodrome       
through the air4  ,nevertheless1 when in
 the summer of #aijc the actual trials  
of the large aerodrome were started1 it 
was found that the very important       
difference between a propeller working  
in a closed room and one working in the 

open air had not been given due         
consideration4 ,several sets of         
propellers1 #b4e metres in diameter1    
unit-pitch ratio1 #cj-;degree blade had 
been constructed and were on hand1 in   
order that no delays might be caused    
through a lack of such extra parts4 ,on 
,september #i1 #aijc1 when the aerodrome
 frame without the wings was mounted on 
the launching car on top of the boat for
 some trial runs with the engine to make
 sure that everything was again in      
readiness1 before the engine had made   
#ejj revolutions1 the port propeller    
broke2 and a few minutes p#ahb later1   
when a new propeller had been           
substituted for this and the engine was 
again started up1 the starboard         
propeller also broke4 ,when1 upon       
further trials and replacements of      
propellers1 all had been so thoroughly  
demolished that there was not a complete
 set remaining1 it was seen very clearly
 that the strains produced on a         
propeller working in the open air are   

very much greater than those produced in
 shop tests1 where the air is           
necessarily quiet4 ,these open-air tests
 of the propellers had demonstrated that
 their weakest point was where the steel
 tubes which received the wooden arms of
 the blade terminated1 and that another1
 though not so serious1 point of        
weakness was where the steel arms were  
brazed to the central hub1 the thin     
metal tending to tear loose even before 
the brazed joint would give way4 ,it    
was1 therefore1 decided to construct    
immediately a new set of propellers in  
which the steel arms should be made of  
much heavier tubing1 that is1 a         
sixteenth of an inch thick at the end   
where it was brazed to the central hub1 
and tapering in thickness to            
one-thirty-second of an inch at the     
other end4 ,these arms were further made
 twelve inches long in place of being   
only three inches long as before4 ,this 
added length carried the steel out      
beyond the point where the first section

 brace joined the three arms together1  
and where they were further strengthened
 by having the cloth covering tightly   
stretched around them4 ,in order to     
utilize such of the hubs of the former  
propellers as had not been seriously    
damaged when the propellers broke1 it   
was also decided to try the effect of   
merely adding an extra length of tube to
 the short arms by means of a thimble   
slipped over and brazed to the two      
parts1 which would make these arms      
twelve inches long4 ,the construction of
 these propellers was pushed as rapidly 
as possible2 and after their completion 
no further trouble was at any later time
 caused by insufficient strength of the 
propellers4 ,even in the test of        
,october #g1 #aijc1 when the aerodrome  
came down in the water at a speed of    
something like fifty miles an hour1 and 
at an angle of approximately forty-five 
degrees1 no break occurred in either    
propeller until1 when the aerodrome was 
plunging through the water1 a blade of  

one propeller was broken by the terrific
 blow which it received when it struck  
the water under the impulse of the      
engine driving it at full speed4 ,the   
severity of this blow is attested by the
 fact that the shaft1 which was of steel
 tubing one-eighth inch thick1 was      
twisted about ninety degrees4  ,this    
experience with propellers very strongly
 emphasizes the fact that on any flying 
machine the strains which are apt to be 
met with in the open air must be allowed
 for in the proportioning of the parts  
of the machine4 ,but since an           
indiscriminate increase of strength in  
all the various parts of the machine    
would entail a prohibitory weight1 very 
careful judgment1 based on experience1  
will have to be exercised in deciding   
just where added strength must be       
employed1 and also where the 8live      
strains0 are not apt to exceed very     
appreciably the calculation for statical
 conditions4  ,illustration3 ,,pl4 #ei  
,,wing ,,clamps   p#ahc  ,owing to ,mr4 

,langley's belief that the tests of the 
man-carrying aerodrome must not only be 
made over the water1 but that it was    
necessary that the machine be launched  
from a car running on a track at a      
considerable elevation in order to      
permit the machine to drop a short      
distance after being launched in case it
 was not quite up to soaring speed when 
launched1 it was necessary that the     
aerodrome be so constructed that it     
could be readily transported to the     
launching track from the interior of the
 house-boat where it was stored4 ,this  
plan of storing the main body of the    
machine in the interior of the boat and 
hoisting it to the launching track just 
before attempting a flight 7some of the 
difficulties of which may be more       
clearly appreciated by an inspection of 
,plate #fj71 made it necessary that the 
wings1 tail and guy-posts be so         
constructed as to be readily attachable 
to and detachable from the main frame1  
and since the weather conditions are    

seldom suitable for a test for more than
 a couple of hours at a time1 it was    
necessary that the mechanism employed   
for attaching these parts be so arranged
 that the proper settings of the        
different parts could be quickly        
obtained1 and without requiring the     
exercise of judgment which past         
experience had shown did not often      
manifest itself during the hurry of the 
preparations for a test4 ,while the     
wings1 therefore1 were made removable1  
yet all of the sockets1 guy-wires1 etc41
 which were loosened in removing them1  
were made with positive stops on them so
 that each fitting that was to be       
tightened up in assembling could be     
adjusted to its definitely determined   
position4  ,as all of the models had    
been constructed with these same parts  
removable in order to permit them to be 
readily shipped back and forth in the   
many trips which had been made with them
 from ,washington to ,chopawamsic       
,island1 the same details of arrangement

 were used for attaching these parts on 
the large aerodrome1 though the actual  
fittings by which the parts were        
attached in the latter case became more 
elaborate4  ,in the drawings1 ,plates   
#eb1 #ec and #ed1 the method of         
attaching the wings to the frame is     
clearly shown4 ,each of the two main    
ribs of each wing was secured to the    
midrod of the frame by a wing clamp1    
shown in detail in ,figs4 #a1 #b1 #e1 #f
 and #g of ,plate #ei4 ,figs4 #a and #b 
show the clamp for the middle main rib  
of each pair of wings1 and ,figs4 #e and
 #f show the clamp for the main front   
rib1 the latter being so constructed    
that the wings could be rocked on the   
midrib clamp as a pivot and secured at  
any angle of lift desired from #f-a_/b  
degrees to #ae degrees4 ,the horns on   
each clamp merely acted as receiving    
sockets for the ends of the ribs1 and   
were not in any way intended to do      
anything more than merely hold the ends 
of the ribs in their correct positions4 

,the wings were fastened to the frame by
 the guy-wires which ran from two points
 on each main rib to an upper and a     
lower guy-post mounted on the midrod4   
,the system of guy-wires for the wings  
is clearly shown in ,plates #eb1 #ec and
 #ed1 and p#ahd in ,plate #fa1 which    
shows the aerodrome mounted on its      
launching car at the rear end of the    
track1 and with the front pair of wings 
in place and all the guy-wires adjusted4
 ,the details of the guy-posts are shown
 in ,plate #fb1 where it will be noted  
that the lower guy-post was of wood1    
with metal fittings1 and was #b metres  
long from the center of the midrod to   
the bottom1 while the upper guy-post was
 a steel tube #aji centimetres long from
 the center of the midrod to its top4   
,the guy-wires from the middle rib of   
each of the pair of wings were fastened 
to the fittings at the bottom of the    
lower guy-post1 while the wires from the
 front main rib were fastened to the    
fittings which were brazed and riveted  

to the slidable collar1 which was       
mounted on the steel tube forming the   
cap on this guy-post4 ,this collar was  
made slidable to permit the angle of    
lift of the wings to be readily changed 
without affecting the length of the     
guy-wires4 ,this collar1 when once set  
for any particular angle of the wing1   
was prevented from sliding by a taper   
pin 7not shown7 which passed through it 
and the guy-post4 ,in order to secure   
the wings more rigidly to the main frame
 and thereby throw on it all torsional  
strains from the wings1 which it was    
specially designed to take1 each of the 
middle main ribs was secured to one of  
the main tubes of the main frame by an  
auxiliary clamp at the point where this 
rib crossed the main tube4 ,these       
auxiliary clamps are clearly shown in   
,figs4 #c and #d of ,plate #ei4         
,projecting from the lower end of each  
of the lower guy-posts was a            
five-sixteenth-inch steel rod about one 
inch long1 as clearly seen in ,plate    

#fb4 ,brazed to the side of this rod1 in
 such a position that it would project  
towards the rear of the aerodrome when  
the guy-post was in position1 was a     
small arm or bracket4 ,when the guy-post
 was in place with the aerodrome on the 
launching car1 this pin was in a slot   
formed in a metal cap on the top of the 
small folding upright at the front or   
rear of the car1 as seen in ,fig4 #a1   
,plate #fc1 while ,fig4 #b of ,plate #fc
 shows the pin just being inserted into 
this slot as the guy-wires of the       
guy-post are being fastened4 ,this small
 arm or bracket on this rod projected   
under the cap to prevent the rod of the 
guy-post from being lifted out of the   
slot in the folding upright1 when the   
wind acting under the wings tended to   
lift the aerodrome from the car4        
,particular attention is here called to 
this apparently insignificant detail1   
for it was this arm or bracket on this  
small rod of the front guy-post which1  
hanging in the cap on top of the folding

 upright1 caused the accident in the    
launching of the aerodrome on ,october  
#g1 #aijc4 ,certain it is that but for  
the accident due to this apparently     
insignificant detail1 success would have
 crowned the efforts of ,mr4 ,langley1  
who above all men deserved success in   
this field of work1 which his labors had
 so greatly enriched4  ,illustration3   
,,pl4 #fj  ,,fig4 #a  ,,fig4 #b  ,,fig4 
#c  ,,hoisting ,,aerodrome ,,to         
,,launching-,,track  ,illustration3     
,,pl4 #fa  ,,aerodrome ,,on             
,,launching-,,car2 ,,front ,,wings ,,in 
,,place1 ,,guy-,,wires ,,adjusted       
,illustration3 ,,pl4 #fb  ,,details ,,of
 ,,guy-,,posts  ,illustration3 ,,pl4 #fc
  ,,fig4 #a4  ,,fig4 #b4  ,,guy-,,post  
,,and ,,pin ,,on ,,launching ,,car      
p#ahe    ,,aviator',s ,,car  ,in        
determining on a suitable car for the   
aviator various designs were made1      
differing all the way from that in which
 the aviator occupied a sitting position
 facing directly ahead and with         

practically no freedom of movement1 but 
was even strapped to the machine to     
avoid the possibility of being thrown   
out1 to the one finally adopted1 in     
which he was provided with the greatest 
freedom of movement1 could either stand 
or sit1 as the occasion seemed to       
demand1 and could face in any direction 
for giving proper attention to any of   
the multitudinous things which might at 
any time require his attention1 and     
could1 if agile1 even climb from the    
extreme front of the machine to the     
rear4 ,the wisdom of giving the aviator 
complete freedom without hampering him  
in any way by provisions for preventing 
his being thrown out of the machine was 
amply justified1 as will later be seen  
in the description of the tests of the  
machine1 where freedom of movement and  
agility prevented a fatal accident4     
,the aviator's car was therefore        
designed to occupy the entire available 
space between the engine and the front  
bearing points1 and between the two main

 tubes of the main frame1 thus allowing 
him a space of something like three feet
 by five feet4 ,the car itself was      
shaped like a flat-bottomed boat1 the   
bottom being approximately level with   
the bottom of the lower pyramid4 ,it had
 a guard rail of steel tubing eighteen  
inches above the floor1 with a cloth    
covering drawn over the frame to        
decrease the head resistance of the     
appurtenances of the engine which were  
placed at the rear end of the car4 ,the 
car was supported by vertical wires     
passing from its bottom up to the main  
frame1 and was prevented from           
longitudinal or side motion by being    
fastened at the front to the cross-rod  
connecting the front bearing points1 and
 at the rear to the lower pyramid4 ,a   
light wooden seat extended fore and aft 
of the car at a height of about two feet
 from the floor1 this seat resting on   
blocks of sponge rubber to absorb some  
of the tremor which existed in the whole
 aerodrome when the engine and          

propellers were working at high speed4  
,the aviator was thus free to stand1 to 
sit sidewise or to straddle the seat1   
and while the network of wires          
surrounding him prevented any great     
possibility of his being thrown out1 yet
 there was a comparatively large opening
 between the guy-wires passing overhead 
which permitted him to climb out of the 
machine4  ,in order to enable the       
aviator to know exactly how the engine  
was operating1 a tachometer1 giving     
instantaneous readings of the number of 
revolutions1 was connected by a suitable
 gear to one of the transmission shafts 
and placed where it could readily be    
seen4  ,during #ahih and #ahii          
considerable time and attention had been
 given to designing an instrument to be 
carried by the aerodrome which would    
automatically record the number of      
revolutions of the engine1 the velocity 
and direction p#ahf of the wind relative
 to the machine1 the height of the      
aerodrome as shown by a specially       

sensitive aneroid barometer1 and the    
angle of the machine with the horizontal
 plane of the earth4 ,the construction  
of this instrument was undertaken by a  
noted firm of instrument makers1 but    
after many months of delay1 during which
 it was several times delivered as being
 complete1 only to be returned for      
further work1 it was finally condemned  
as unsatisfactory1 and it was decided   
not to encumber the machine with such a 
delicate apparatus1 which1 even if      
perfectly made1 could not be depended on
 to work properly when mounted on the   
aerodrome frame1 in which there was a   
constant1 though minute1 tremor due to  
the high speed and power of the engine4 
,the completed frame1 which is perhaps  
best shown in ,plates #di1 #ej and #ea1 
and ,plate #fj1 ,figs4 #a1 #b and #c1 in
 spite of its size gave an appearance of
 grace and strength which is            
inadequately represented in the         
photographs4 ,in making the designs for 
the large aerodrome no data were        

available for use in calculating the    
strains that would come on the different
 parts of the frame while in the air1   
and the size and thickness of the tubes 
and the strength of the guy-wires were  
consequently determined almost entirely 
by 8rule of thumb10 backed by experience
 with the models4 ,although the         
dimensions1 shape1 and arrangement of   
most of the auxiliary parts of the      
machine were considerably changed during
 the course of construction in          
accordance with the indications of the  
exhaustive series of shop tests1 the    
fundamental features of the construction
 were practically unaltered1 but the    
changes in the guy-wire system and in   
the fittings by which they were         
attached1 made the frame as a whole     
several times as strong as it was       
originally1 and it was felt that the    
direction of further improvements in it 
would be shown only by actual test of it
 in flight where any weaknesses would be
 certain to manifest themselves4  ,it   

may be well to remark here that even    
with the data which were later obtained1
 judgment based on experience proved    
after all to be the safest guide for    
proportioning the strength of the       
various parts4 ,it can be assumed that a
 live stress will produce a strain ten  
times as great as that due to a static  
stress on the part when the machine is  
stationary4 ,for greater safety1 it     
would be still better to assume a strain
 twenty times as great4 ,if one is      
building bridges1 houses1 and similar   
structures1 where weight is not a prime 
consideration1 it would be criminal     
negligence to fail to provide a         
sufficient 8factor of safety10 or what  
in many instances may be more properly  
termed a 8factor of ignorance10 while at
 the present time the insistence on     
large factors of safety in machines     
intended to fly would so enormously     
increase the weight that1 before        
one-half the necessary parts were       
provided1 the weight would be many times

 what could possibly be supported in the
 air4 ,later1 no doubt1 as experience is
 gained in properly handling the machine
 in the air1 increased strength         
entailing p#ahg increased weight may be 
added in proportion to the skill        
acquired2 and there is no doubt that man
 will acquire this skill with marvelous 
rapidity1 approaching1 if not equaling1 
that exhibited by him in the use of the 
bicycle1 which1 when first ridden1      
requires not only all of the rider's    
skill but that of a couple of           
assistants1 but when once mastered      
requires hardly more thought for its    
proper manipulation than even the act of
 walking involves1 the balancing and    
guiding being done intuitively merely by
 the motion of the body and with        
practically no exertion4   p#ahh        
,,chapter ,,vi  ,,construction ,,of     
,,supporting ,,surfaces  ,an examination
 of the wings of birds1 whether those of
 soarers or of any other type1 impresses
 one not only with the general strength 

of the wing1 but also with the fact     
that1 while it possesses considerable   
stiffness1 there is also a graduated    
pliability1 not only of the whole wing1 
including the bones1 but more especially
 in the feathers1 the rear tips being   
exceedingly pliable so that1 when the   
wing is held in a stiff breeze1 they are
 seen to be easily deflected in a gentle
 curve towards the rear and upper side4 
,this lack of rigidity has several      
advantages1 among the more notable of   
which is the lessening of the strains on
 the wing caused by sudden wind gusts4  
,of great importance is the further fact
 that a supporting surface having a     
graduated pliability1 such as is        
possessed by a bird's wing1 does not    
experience a shifting of the center of  
pressure to the same extent as a rigid  
surface of similar form4 ,furthermore1  
since any bird1 even the best soarer1   
must use its wings not only for soaring1
 but1 when starting to fly from a state 
of rest1 for flapping1 a rigid surface  

would not furnish anything like the same
 universally available sustaining and   
propelling means that the bird's wing   
does4  ,in an inspection of the various 
wings or supporting surfaces which ,mr4 
,langley built1 from the very earliest  
rubber-pull models up to the successful 
steam machines ,nos4 #e and #f1 the     
point which is most impressed upon the  
observer is the increasing strength and 
rigidity embodied in these wings4 ,while
 the success with the later models was  
due to many things1 including the       
development of a strong frame and a     
suitable power plant giving sufficient  
power for the permissible weight1       
besides the very important development  
of effective equilibrium mechanism1 yet 
it is safe to say that even with the    
development of all these other things to
 the state to which they had been       
brought in #ahif1 success would not have
 been achieved had not the wings        
themselves been simultaneously changed  
from the very flimsy construction which 

was at first used to the later type1    
using a very strong and rigid wooden    
frame over which the cloth covering was 
tightly stretched1 and which possessed  
only a small amount of pliability at the
 extreme rear ends of the cross-ribs4   
,the development of this successful type
 of wing for the models1 it will be     
remembered1 had been achieved only after
 an extensive series of experiments2 and
 it was realized that the construction  
of suitable wings for the large         
aerodrome1 even with the knowledge      
gained in the early work1 would be still
 more p#ahi difficult4 ,the problem was 
that of constructing for a very little  
greater weight per square foot1 wings   
containing approximately sixteen times  
the area of the model wings4  ,it will  
be recalled from the previous           
description of model ,aerodrome ,no4 #e1
 that its four wings had a combined area
 of #fh square feet and weighed         
approximately #bejj grammes1 or #cg     
grammes per square foot4 ,it was not    

expected that the large wings would be  
of so light a weight per square foot1   
which would have meant only about       
#ce1ejj grammes 7approximately #gh      
pounds7 weight for the #ifj square feet 
originally planned4 ,it was hoped1      
however1 that the increase in weight per
 square foot for the large wings would  
be less than the square root of the     
increased linear dimensions4 ,in this   
case1 the increase in linear dimensions 
being approximately four1 it was1       
therefore1 hoped that the larger wings  
would not have quite twice the weight   
per square foot of the smaller ones2 the
 computed weight permissible for the    
large wings was therefore placed at #abj
 pounds4  ,to obtain the required area  
within the permissible limits of weight 
two well-defined paths of procedure were
 open3 ,first1 it was possible to so    
modify the structural form of the wing  
as to obtain the advantage of the       
increased strength of trussed           
structures1 that is1 by superposing the 

wings4 ,or1 second1 the 8single-tier0   
type of wing1 the efficiency of which   
had been fairly well determined1 could  
be retained1 and strength gained without
 increase of weight by improving the    
method of constructing the wooden       
framework and by extending the system of
 guy-wires4  ,some knowledge of the     
superposed type of supporting surfaces  
had already been gained by the          
experiments at ,allegheny and the tests 
of the rubber-driven models1 in which   
superposed wings had frequently been    
used2 but it was felt that this         
knowledge was altogether inadequate to  
aid in determining either whether the   
superposed type of construction         
possessed in practice the advantages    
which theory would indicate1 or how and 
at what distance apart the surfaces     
should be superposed to obtain the best 
results4 ,in order to obtain the desired
 information1 a series of tests on the  
whirling-table of complete wings        
suitable for use on the models was made4

 ,these experiments were supplemented by
 the practical tests with the models1   
which have already been described in    
,chapter ,,iii1 in order to give the    
wings a trial under the conditions of   
flight1 where they would be subjected to
 the action of the propellers and the   
uneven character of the wind4  ,in      
addition to determining what type of    
construction and what form of surface   
would give the greatest 8lift0 with the 
smallest 8drift10 these whirling-table  
tests supplied data as to how much      
greater the actual resistance of the    
wing with its necessary guy-posts and   
guy-wires was than the theoretical      
resistance1 found by extrapolation from 
the results obtained in the tests of    
rigid p#aij curved surfaces formed of   
wood4 ,the first of this series of      
tests1 the results of which are given   
below1 was made ,november #cj1 #ahih1 on
 the superposed wing shown in ,plate    
#cg1 ,figs4 #a and #b4 ,it should be    
noted1 however1 that when this test was 

made the wing was not provided with the 
stiffening strips or the vertical       
partitions4   ,weight of wing  #ajjj    
grammes2 weight of guy-posts1 etc41     
#dge  grammes2 distance of mean center  
of gravity of guy-posts1 etc41 from     
pivots of balance arm  one-half distance
 of ,,cp of wing from pivots  of balance
 arm2 the wing1 therefore1 had a lever  
arm of two to one  with reference to    
weight of guy-posts1 etc41 so that the  
equivalent  weight of guy-posts1 etc41  
#bcg grammes4 ,this gives #abcg grammes 
of equivalent load on the wing  #b4gc   
pounds4 ,area of wing  #ba4he  square   
feet4 ,therefore load on wing  #j4abe   
pounds per square foot4   ,angle        
,revolutions   ,velocity of   ,velocity 
,drift   of       of turn-      center  
of    7ft4 per   7grammes74  chord4     
table4       wing 7ft4     second74     
per min47  #b4j       #aj4ge            
#ajhf           #ah4a         #bee  #c4j
       #aj4j         #ajaj              
#af4he        #bee  #e4j        #i4e    

#ifj           #af4j         #bee  #aj4j
       #g4ge         #ghc               
#ac4j         #bee   ,angle    ,drift   
,foot-pounds      ,calculated   of      
7pounds74    per sec4       soaring     
speed  chord4                  ,,rv4    
carrying #j4e                           
pounds per sq4 ft4                      
7ft4 per sec474  #b4j      #j4efa       
#aj4ae            #cf4b  #c4j           
#j4efa         #i4dg            #cc4g   
#e4j      #j4efa         #h4ih          
#cb4j  #aj4j     #j4efa         #g4c    
#bf4j  ,the very interesting phenomenon 
was noted in this test that the 8drift0 
or resistance of the wing seemed to     
remain unchanged at soaring speed at    
different angles of elevation4 ,it is   
hardly probable that this result is     
accurate1 for the 8balance arm0         
undoubtedly twisted under the action of 
the wing1 and this caused it to strain  
on its pivots1 and thus1 to a certain   
extent1 falsify the record as to drift4 
,a test of a single-tier wing at        

different angles of elevation was made  
on ,december #f1 #ahih4 ,this wing was  
nearly the same as those used in actual 
flights of ,aerodromes ,nos4 #e and #f  
in ,may and ,november1 #ahif1 the wing  
being of the same width fore and aft1   
but somewhat shorter4 ,the actual wing  
was a little too long to permit its     
being used on the whirling-table in the 
limited space of the shop4   ,weight of 
wing  #dbj grammes2 weight of guy-posts1
 etc41  #cbj  grammes2 equivalent weight
 of guy-posts1 etc41  #aej grammes      
applied  on the wing4 ,therefore1 total 
load on wing  #egj grammes4 ,area of    
wing  #aa4b square feet2 equivalent load
 on wing  #j4aab pounds per  square     
foot4   ,angle    ,revolutions          
,velocity of     ,velocity     ,drift   
of       of turn-        center         
7ft4 per   7grammes74  chord4     table4
        of wing       second74          
7ft4 per min47  #b4j       #aa4f        
#aaie           #ai4i        #baj  #c4j 
#i4ge          #ajje           #af4g    

#aeg  #e4j        #h4be           #hej  
#ad4b        #acc  #aj4j       #f4ge    
#fie           #aa4f        #abi  #ab4e 
#f4j            #fah           #aj4c    
#abi   ,angle    ,drift                 
,foot-pounds      ,calculated   of      
7pounds74    per sec4       soaring     
speed  chord4                  ,,rv4    
carrying #j4e                           
pounds per sq4 ft4                      
7ft4 per sec474  #b4j      #j4dfb       
#i4b              #db4a  #c4j           
#j4cde         #e4gg             #ce4c  
#e4j      #j4bic         #d4af          
#cj4j  #aj4j     #j4bhd         #c4bi   
#bd4e  #ab4e     #j4bhd         #b4ib   
#ba4h  ,in this test it is to be noted  
that the 8drift10 or resistance1 while  
considerably greater at soaring speed   
for #b degrees than for #e degrees1     
remains practically the same between #e 
degrees and #ab-a_/b degrees4 ,comparing
 it with the preceding test with the    
superposed wing1 it is seen that at     
soaring speed at an angle of #aj        

degrees1 the single-tier wing having a  
load of #j4aab pounds per p#aia square  
foot1 has only #abi grammes drift1 while
 the superposed one1 while supporting   
#j4abe pounds per square foot1 has #bee 
grammes drift4 ,moreover1 the soaring   
speed of the single-tier wing is only   
#aa4f feet per second1 while the        
superposed one requires a speed of #ac  
feet per second4  ,as the superposed    
wing tested on ,november #cj was so weak
 structurally that it could not be made 
to keep its proper shape without adding 
an excessive number of guy-wires1 it was
 decided that it was not adapted for use
 on the aerodrome1 but before abandoning
 it the partitions and strips were added
 and it was again tested on the         
whirling-table on ,march #a1 #ahii1 with
 the following results3   ,weight of    
wing  #ije grammes2 weight of guy-posts1
 etc41  #cbj  grammes2 equivalent weight
 of guy-posts1 etc41  #aej grammes      
applied  at ,,cp of the wing2 equivalent
 load on the wing  #ajee grammes        

#b4cba pounds2 area of wing  #ba4he     
square feet2 equivalent load on  wing   
#j4ajfb pounds per square foot4   ,angle
    ,revolutions   ,velocity of         
,velocity     ,drift   of       of turn-
        center       7ft4 per           
7grammes74  chord4     table4        of 
wing       second74                     
7ft4 per min47   #e4j     #aj4hge       
#aajj            #ah4ce       #bej      
#e4j     #aj4ge          #ajhe          
#ah4jg       #bej   #e4j     #aj4ge     
#ajhe            #ah4jg       #bej      
#aj4j      #h4j            #hjh         
#ac4dg       #bej  #aj4j      #h4j      
#hjh            #ac4dg       #bej  #aj4e
      #g4hge          #gig              
#ac4c        #bej  #aj4e      #g4hge    
#gig            #ac4c        #bej  #ac4j
      #g4j            #gjg              
#aa4gh       #bej   ,angle    ,drift    
,foot-pounds      ,calculated   of      
7pounds74    per sec4       soaring     
speed  chord4                  ,,rv4    
carrying #j4e                           

pounds per sq4 ft4                      
7ft4 per sec474   #e4j     #j4ee        
#aj4a             #ci4ha   #e4j         
#j4ee          #i4id            #ci4ai  
#e4j     #j4ee          #i4id           
#ci4ai  #aj4j     #j4ee          #g4d   
#bi4bbf  #aj4j     #j4ee          #g4d  
#bi4bbf  #aj4e     #j4ee          #g4cb 
#bh4hf  #aj4e     #j4ee          #g4cb  
#bh4hf  #ac4j     #j4ee          #f4dh  
#be4eec  ,an examination of the data    
obtained in this test shows the wing to 
be of slightly less efficiency than when
 first tested4 ,while it was            
considerably stronger it was still too  
weak for use on the aerodromes4  ,a     
second type of superposed wing1 ,plates 
#fd and #fe1 was therefore constructed  
and tested on the whirling-table on     
,march #b1 #ahii1 with the following    
results3   ,weight of wing  #ajbe       
grammes2 weight of guy-posts1 etc41     
#cbj  grammes2 equivalent weight of     
guy-posts1 etc41  #aej grammes applied  
at ,,cp of the wing2 equivalent load on 

the wing  #aage grammes   #b4ehe pounds2
 area of wing  #ba4he square feet2      
equivalent load on  wing  4#aahc pounds 
per square foot4   ,angle               
,revolutions   ,velocity of             
,velocity     ,drift   of       of turn-
        center       7ft4 per           
7grammes74  chord4     table4        of 
wing       second74                     
7ft4 per min47   #e4j      #aa4fbe      
#aagj           #ai4e        #bej   #e4j
      #aa4fbe         #aagj             
#ai4e        #bej   #h4j      #aj4e     
#ajfj           #ag4g        #bej  #aj4j
       #i4abe          #iai             
#ae4c        #bej  #aj4j       #i4abe   
#iai           #ae4c        #bej        
,angle    ,drift       ,foot-pounds     
,calculated   of      7pounds74    per  
sec4       soaring speed  chord4        
,,rv4           carrying #j4e           
pounds per sq4 ft4                      
7ft4 per sec474   #e4j      #j4ee       
#aj4gb             #dj4jhg   #e4j       
#j4ee        #aj4gb             #dj4jhg 

#h4j      #j4ee         #i4ge           
#cf4cg  #aj4j      #j4ee         #h4dc  
#ca4d  #aj4j      #j4ee         #h4dc   
#ca4d  ,during the tests on the         
whirling-table this type of construction
 seemed to be exceedingly strong and    
stiff1 and to be easily maintained in   
whatever position it was placed4 ,it was
 therefore thought that it would prove  
strong enough for the aerodrome1 and it 
was accordingly inverted and given a    
8sanding test0 p#aib by sprinkling sand 
uniformly over it to such a thickness as
 to cause it to have a load of #j4ge    
pounds per square foot4 ,as it showed no
 serious deflection or change of form   
under the sanding test1 it was decided  
that it was strong enough for use in    
tests of the model aerodromes in actual 
flight4  ,upon the completion of these  
whirling-table tests1 the cloth covering
 of this wing was painted with collodion
 varnish1 which increased the weight of 
the wing only #ej grammes4 ,in order to 
make the results of its tests more      

easily comparable with those obtained   
before varnishing1 the cross guy-wires  
on the wing were changed to a slightly  
smaller size in order to make the weight
 of the wing the same as before4 ,it was
 tested on ,march #c1 and the following 
results were obtained3   ,weight of wing
  #ajbe grammes2 weight of guy posts1   
etc41  #cbj  grammes2 equivalent weight 
of guy-posts1 etc41  #aej grammes       
applied  at ,,cp of the wing2 equivalent
 load on wing  #aage grammes  #b4ehe    
pounds2 area of wing  #ba4he square     
feet2 equivalent load on wing   4#aahc  
pounds per square foot4   ,angle        
,revolutions   ,velocity of             
,velocity     ,drift   of       of turn-
        center       7ft4 per           
7grammes74  chord4     table4        of 
wing       second74                     
7ft4 per min47   #e4j      #aj4e        
#ajfj           #ag4g        #bej   #e4j
      #aj4e           #ajfj             
#ag4g        #bej  #aj4j       #h4e     
#hei           #ad4c        #bej  #aj4j 

#h4e            #hei           #ad4c    
#bej    ,angle    ,drift                
,foot-pounds      ,calculated   of      
7pounds74    per sec4       soaring     
speed  chord4                  ,,rv4    
carrying #j4e                           
pounds per sq4 ft4                      
7ft4 per sec474   #e4j      #j4ee       
#i4ge             #cf4cg   #e4j         
#j4ee         #i4ge             #cf4cg  
#aj4j      #j4ee         #g4hh          
#bi4d  #aj4j      #j4ee         #g4hh   
#bi4d  ,although the varnishing of the  
wing seemed to have no effect on the    
8drift10 the soaring speed was slightly 
decreased4  ,as a result of these tests 
it was decided to construct three more  
wings like this second type1 the four   
forming a complete set for use on the   
steam-driven models ,nos4 #e and #f4    
,although the tests on the              
whirling-table indicated a superior     
efficiency for the 8single-tier0 wings1 
and it was not expected that in actual  
use on the aerodrome the result would be

 different1 yet it was felt that as the 
conditions of actual use are so very    
different from those of a whirling-table
 experiment it would not be safe to     
decide too definitely against the       
superposed wings without first giving   
them a test under actual conditions4    
,aside from the decreased lifting effect
 shown by the superposed wing when      
compared with the 8single-tier0 one1 it 
was also thought that under the actual  
conditions of use on the machine the    
superposed wing would show up still     
worse4 ,the deflection of the air by the
 front wings diminishes the lift of the 
rear ones even for the 8single-tier0    
type1 and this1 it seemed certain1 would
 be greatly aggravated in the case of   
the superposed type4  ,in order to      
emphasize more fully the results of     
these tests the following table is      
added1 which gives the data for the     
8single-tier0 wing and this second type 
of superposed one1 when each was tested 
at ten degrees angle of elevation3      

,illustration3 ,,pl4 #fd  ,,experimental
 ,,type ,,of ,,superposed ,,wings1      
,,march #b1 #ahii  ,illustration3 ,,pl4 
#fe  ,,experimental ,,type ,,of         
,,superposed ,,wings1 ,,march #b1 #ahii 
p#aic                                   
,wing                                   
8,single-tier0   ,superposed4           
,type ,no4 #b  ,length 7feet74          
#d4bg           #d4bg  ,area 7sq4 ft474 
#aa4b           #ba4i  ,weight 7pounds74
                #a4bf           #b4ei   
,angle of chord4 77            #aj      
#aj  ,soaringspeed1 7ft4 per    sec474  
#aa4f           #ad4c  ,weight 7lbs4 per
 sq4    ft474                           
4#aab           4#aah  ,drift 7lbs4 per 
sq4    ft474                            
4#jbe           4#jbf  ,calculated      
soaring    speed1 carrying #j4e    lbs4 
per sq4 ft4    7ft4 per sec474          
#bd4e           #bi4d   ,the            
8single-tier0 wings actually used on    
,aerodrome ,no4 #f were #e4cc feet long1
 while the wing tested above was only   

#d4bg feet long4 ,in order to bring out 
more fully what might be expected of    
,aerodrome ,no4 #f1 when using the two  
different types of wings1 the following 
table1 calculated from the preceding    
one1 is given4 ,this shows the results  
which might be expected from the        
aerodrome when the resistance of the    
machine itself was included3  ,aerodrome
 ,no4 #f without wings weighs #bb       
pounds4                                 
8,single-tier0   8,single-tier0         
,superposed4                            
7short7      7full-length7   ,type ,no4 
#b  ,length 7feet74                     
#d4bg             #e4cj          #d4bg  
,area of two pair of    wings 7sq4      
feet74            #dd4h                 
#ed4j          #hg4f  ,weight of two    
pair of    wings 7pounds74              
#e4jd             #e4e          #aj4cf  
,weight of aerodrome with    two pair of
 wings 7lbs474    #bg4jd                
#bg4e          #cb4cf  ,total weight to 
be    supported 7lbs4 per sq4    ft474  

#j4fjc            #j4ea          #j4cfi 
,drift of wings 7lbs474          #f4jf  
#f4ac          #f4i  ,assumed drift of  
aerodrome body 7lbs474        #a4j      
#a4j           #a4j  ,total drift       
7pounds74           #g4jf               
#g4ac          #g4i  ,soaring speed 7ft4
 per    sec474                          
#bg4j             #bd4g          #be4c  
,thrust horse-power    expended4        
#j4ce             #j4cb          #j4cfd 
,brake horse-power    expended4         
#j4gj             #j4fd          #j4gc  
,the first line shows the calculations  
for the aerodrome when equipped with the
 short 8single-tier0 wings2 the second  
line1 when equipped with the            
8single-tier0 wings of the full length  
used in the flights of #ahif2 and the   
third line1 when equipped with          
superposed wings1 ,type ,no4 #b4  ,it   
will be seen that1 on the whole1 the    
result of the comparison of the         
full-length 8single-tier0 wing and the  
superposed one is less in favor of the  

latter than was to be expected1 as1     
aside from its greater structural       
strength1 it seems to have no real point
 of superiority1 except that it is      
shorter2 and1 as already pointed out1   
one point of presumable inferiority1    
though not exhibited in the table1 is   
the fact that the rear set of wings     
would suffer relatively more from being 
in the lee of the front ones1 in the    
case of the superposed wings1 than in   
the case of the 8single-tier0 ones4     
,besides these 8conventional0 forms of  
wings1 various other types were tested  
on the whirling-table4 ,the data of     
these tests are not given1 as in the    
rough preliminary tests the results were
 so entirely negative in character that 
accurate quantitative tests were never  
made4 ,however1 since in work of this   
kind the greatest delay is experienced  
in learning what not to do1 and in      
ridding one's self of freak notions     
which are continually suggesting        
themselves1 it may be well here to      

describe sufficiently at least one of   
these types of wing to enable others to 
avoid any loss of time in experiments   
with it4 ,since the principal           
disadvantages of a wing possessing      
considerable width in the fore and aft  
direction are due to the great extent   
through which the center of pressure    
p#aid shifts when the velocity of       
advance or angle of incidence is        
changed1 and to the further fact that a 
wide surface does not support           
proportionately as much per square foot 
as a long and narrow one1 it was thought
 that some advantage might be gained by 
making the covering of the wing in the  
form of strips1 the edges of which would
 be perpendicular to the direction of   
motion1 or by making this covering in   
more or less slat-like form1 which would
 permit the air which had already been  
acted upon by the leading slat to slip  
through between the rear edge of the    
first slat and the leading edge of the  
succeeding one4 ,in the tests on the    

whirling-table1 however1 it was found   
that this type of construction not only 
did not possess any advantages1 but was 
even less effective than a similar one  
in which the covering was continuous4   
,the difference was probably due to the 
fact that the air which passed between  
the slats reduced the suction on the    
upper side of the following slat1 and   
also to the fact that the distance      
between the slats was not sufficient to 
gain the effect of having each slat act 
on air which had not already been       
partially deflected by the preceding    
one4  ,in view of the results of these  
tests on various types of wings1 it was 
decided that in constructing the first  
set of wings for the large aerodrome it 
would be best to employ the             
8single-tier0 type1 which had proved    
successful with the models1 and that    
after getting a successful flight with  
these the superposed wings would be     
tried in order to get1 if possible1 the 
advantage which they possessed of being 

structurally stronger and more compact4 
,it was therefore clear that any gain in
 the strength and rigidity of the first 
set of wings1 as a whole1 would have to 
be obtained by improvements in the      
construction of its integral parts1 that
 is1 in the main and cross-ribs which   
made up its framework4  ,before         
attempting to proportion the parts of   
the necessary wooden wing frame1 which  
it was expected would probably undergo  
many changes before a final design was  
secured which would embody maximum      
strength for minimum weight1 various    
tests were made to determine just how   
light a cloth covering could be obtained
 which would be strong enough and       
sufficiently impervious to the air4 ,in 
the construction of the wings for the   
models a good grade of ,china silk had  
been employed1 but on account of the    
greatly increased quantity of cloth     
required for the large wings1 it was    
hoped that something approximately as   
good as the silk could be secured at a  

much less cost1 and various grades of   
percaline were therefore tested4 ,the   
weight of the various grades of         
percaline ranged from three grammes to  
ten grammes per square foot1 the lighter
 samples being of a rather coarse mesh1 
while the heaviest ones were not only   
close mesh but some specimens contained 
a large amount of 8sizing40 ,the        
particular grade which was finally      
adopted weighed seven grammes per square
 foot4 ,this material was practically   
impervious to air at a pressure of one  
pound per square foot1 which1 of course1
 was considerably p#aie more than it    
would be subjected to in flight4 ,this  
grade of percaline weighed approximately
 one and a half times as much as a grade
 of silk1 which on test was found to    
have a slightly greater tensile strength
 than the percaline1 though the latter  
did not 8flute0 or 8pocket0 nearly as   
much as the silk4 ,moreover1 the cost of
 the percaline was only about one-third 
that of the silk1 and it was chiefly for

 this reason that percaline was adopted 
in place of silk4 ,allowing for         
necessary seams and extra material to be
 turned over at the front and rear edges
 of the wings1 the percaline covering1  
which under the original plans comprised
 approximately #ajjj square feet1 was   
therefore calculated to weigh           
approximately #gjjj grammes1 exclusive  
of the necessary cords for lacing the   
coverings to the wooden frames of the   
wings4  ,as the one hundred and twenty  
pounds allowed for the four wings       
permitted only thirty pounds per wing1  
and as the cloth covering1 lacing cords1
 etc41 were found to weigh something    
over four pounds1 there remained only   
about #be pounds as the permissible     
weight of the wooden framing1 including 
the necessary metal clips1 secondary    
guy-wires1 etc41 for each wing4 ,with   
the relative proportions of the various 
parts of the wooden framing of the wings
 of the models as a basis1 it was       
decided to make the main ribs of the    

large wings #a4e inches in diameter for 
one-half their length1 and have them    
taper from this size to one inch in     
diameter at the extreme point4 ,after   
making allowance for the weight of these
 ribs1 it was found that1 if the        
cross-ribs were to be spaced no farther 
than ten inches apart1 and the two end  
ones were to be made at least as wide as
 #a4e inches in order to resist the end 
strain due to the stress of the cloth1  
the twenty-six intermediate cross-ribs  
could be only seven-sixteenths of an    
inch in diameter at the point where they
 crossed the main rib1 and that they    
must be tapered to three-eighths of an  
inch in diameter at the front end and to
 one-fourth of an inch in diameter at   
the rear tip4  ,a trial wing1 whose     
total weight was #cj pounds #b ounces1  
was made up with the various parts of   
its frame of the above dimensions4 ,even
 upon inspection it appeared to be too  
flimsy to withstand the sudden gusts of 
wind which were certain to be met in    

actual practice4 ,in order1 however1 to 
get some definite data as a guide1 the  
wing was inverted and guyed in the same 
way that it was proposed to guy it on   
the aerodrome1 and a uniform thickness  
of sand was then sprinkled over it to   
such a depth as to give it a load of    
#j4g pounds per square foot4 ,even      
before one-quarter of the sand was      
sprinkled over it1 it was seen that the 
wing was rapidly going out of shape1 and
 it was feared that the full amount of  
sand would not only seriously distort   
it1 but would even break it4 ,the full  
quantity of sand1 however1 did not break
 it1 but distorted it to such an extent 
that1 had the pressure been due to its  
being propelled through the air1 its    
serious change in form would have       
rendered it worse than useless4 p#aif   
,while the main ribs had shown a certain
 amount of deflection under the sanding 
test1 the more serious distortion had   
been in the cross-ribs1 the small       
guy-wires1 which had been fastened to   

each cross-rib1 becoming loose instead  
of tight1 as had been expected1 since   
the rib tended to increase its curvature
 instead of straightening out4 ,this    
increase in the curvature of the        
cross-ribs was partly overcome by tying 
the guy-wire flat against the cross-rib 
for a distance of about #b feet from the
 rear tip4 ,but while this caused the   
guy-wire to tighten the general contour 
of the wing showed very little          
improvement1 as the ribs now assumed a  
curve more or less like the letter ,s1  
the rear tip now being bent downward to 
form the tail of the elongated ,s4      
,from this sanding test it was seen that
 the cross-ribs must be materially      
stiffer1 and a new set was accordingly  
made one-sixteenth of an inch larger in 
diameter at the various points of       
measurement4 ,upon giving the wing1     
equipped with these larger ribs1 a      
sanding test it was found that1 while   
there had been some improvement1 it was 
entirely too flimsy1 even when it been  

double-guyed by running a second wire on
 each cross-rib from the middle of the  
portion in front of the mid-rib to the  
middle of the portion behind the        
mid-rib4 ,as the weight of the wing with
 these larger solid cross-ribs had now  
increased to more than #cc pounds1 and  
the wing had proved itself altogether   
too weak for use on the aerodrome1 it   
was evident that some other plan of     
constructing the ribs which would give  
greater strength for the same weight    
must be found4 ,at first sight it might 
appear that the obvious way of          
increasing the stiffness of the         
cross-ribs was to employ a cross-section
 other than a round one1 since material 
added to the depth of the rib is very   
much more effective than if added to the
 width4 ,it must1 however1 be remembered
 that these cross-ribs were #aa feet    
long1 and that1 as the main mid-rib was 
#f feet in front of the rear tips of the
 cross-ribs1 with no intermediate       
bracing1 except the light threads by    

which the cloth cover was attached1 it  
was inevitable that1 should the depth be
 made materially greater than the width1
 the rib would buckle sideways4 ,test   
ribs of ,i-beam form1 which are later   
described1 were constructed1 but1       
although they proved exceedingly stiff1 
had to be discarded4  ,in view of these 
facts the obvious remedy appeared to be 
to make the rib hollow1 and one         
cross-rib1 #c_/d of an inch in diameter 
at the point where it crossed the main  
rib1 tapering to #e_/h of an inch at the
 front and #c_/h of an inch at the rear 
tip1 was accordingly constructed4 ,tests
 showed that this form of rib1 which was
 about #aj grammes lighter than the     
#a_/b-;inch solid ribs1 was much stiffer
 than anything yet constructed4 ,but    
when a wing1 with cross-ribs of this    
size placed #bj inches apart1 was sanded
 it was found that1 although a great    
advance in construction had been made1  
still further improvement was necessary 
before a suitable wing for the large    

aerodrome could be procured4 p#aig      
,before proceeding with the construction
 of any more complete wings1 an extended
 series of experiments was made in order
 to secure ribs of proper lightness and 
strength4 ,various forms of metal tubes 
were tested2 but1 although aluminum     
seemed at one time to promise good      
results1 it was found that hollow ribs  
could be constructed of spruce which    
were much stronger than aluminum tubes  
of the same weight4 ,in order to        
determine more accurately what mode of  
construction would give the greatest    
stiffness and strength for a minimum    
weight1 it was decided to make up some  
test pieces of different forms before   
making up complete ribs4 ,for           
convenience in construction1 these test 
pieces were made straight and shorter   
than the large cross-ribs4 ,each piece  
was tested by fastening it in the       
testing clamp with #a metre of its      
length projecting horizontally1 and     
attaching at its end a weight of #a     

kilogramme4 ,the deflection from the    
horizontal gave an index of the         
stiffness of the piece under            
examination4  ,the first test piece was 
a hollow square1 #ag mm4 length of side 
on the exterior1 and #aa mm4 length of  
side on the interior1 the walls thus    
being #c mm4 thick4 ,this weighed #gc   
grammes per metre and had small internal
 stiffening pieces1 like the partitions 
in bamboo1 glued into it #d inches      
apart4 ,a weight of #a kilogramme at the
 distance of #a metre gave a deflection 
of #ef mm4 ,the second test piece was a 
duplicate of the first one1 except that 
it had no internal stiffening pieces1   
and the weight per metre was made the   
same1 #gc grammes1 as formerly1 by      
leaving the walls a fraction thicker4   
,the deflection in this case was1 as    
would be expected1 exactly the same as  
in the first one4 ,the first test piece1
 however1 was superior to the second one
 in that it was stiffer against being   
crushed in by accident4 ,the third test 

piece was a hollow cylinder1 #bb mm4    
outside diameter and #ag mm4 inside     
diameter1 the walls thus being #b4e mm4 
thick4 ,the weight per metre was #ia    
grammes1 and the deflection was #df mm4 
,the fourth test was made by taking two 
of the original solid cross-ribs1 #ab   
mm4 in diameter1 and fastening them in  
the clamp side by side1 with a length of
 #a metre projecting4 ,the weight per   
metre for the two ribs was #aje grammes1
 and the deflection produced on the two 
by #a kilogramme at #a metre distance   
was #aae mm4 ,the fifth test piece was  
an ,i-beam of spruce1 having a depth of 
#be mm41 with the flanges #ab4e mm4 wide
 and the web #c mm4 thick4 ,the weight  
per metre was #fe grammes1 and the      
deflection was #bf mm4 ,all of these    
test pieces were made of carefully      
selected straight-grained spruce4  ,it  
is readily seen that the test piece     
having the ,i-beam section weighed less 
than the hollow square in the first and 
second tests1 and had a deflection of   

less than half4 ,this ,i-beam section1  
however1 did not show up so well when a 
longer piece was tested1 for as soon as 
the length was made appreciably greater 
than a metre it began to twist1 the     
twisting becoming more and more serious 
the p#aih greater the length1 until with
 a piece #aa feet long1 the full length 
of a cross-rib1 the twisting was so     
serious as to make the rib practically  
useless4 ,it was at first thought that  
this twisting might be overcome by      
making the webs slightly wider1 and it  
would to a certain extent1 but in       
looking ahead and planning how the      
cross-ribs were to be fastened to the   
main ribs1 the ,i-beam section was seen 
to present so many difficulties that it 
was thought hardly worth while to spend 
time on further experiments with it4    
,this decision was made all the more    
imperative by foreseeing the difficulty 
of bending the ,i-beam section to the   
curve which the cross-ribs were to have4
 ,in fact it had been found by          

experience that while many different    
forms of ribs could be bent to the      
proper curve by steaming and clamping   
them over a form and then drying them   
out while still clamped to the form1 yet
 the grain of the wood varied so in     
different ribs1 that of a dozen steamed 
and bent over the same form it was      
seldom that as many as three would have 
approximately the same amount of        
curvature when removed from the form    
after drying4 ,if1 however1 the curve   
was formed in the ribs by making them in
 two parts1 which were glued together   
and clamped up on the form while the    
glue dried1 practically any number could
 be made which would have the same      
curvature when thinned down to the      
proper thickness of wall4  ,it was      
recognized at all times that the gluing 
together of the ribs not only entailed  
extra work1 but introduced an element of
 uncertainty unless some kind of a      
varnish for the ribs could be found     
which would prevent any possibility of  

the glue becoming soft from moisture in 
the atmosphere or from the wings        
actually coming down into the water when
 the aerodrome was tried in flight4 ,a  
search was therefore made for a varnish 
that was water-proof4 ,a large number of
 different varnishes were tried1 and one
 was finally found which1 after repeated
 tests1 seemed to be thoroughly good4   
,several test ribs were given three     
coats of this varnish1 and were then    
kept immersed in water for #bd hours    
without the glue showing any signs of   
softening4 ,it was therefore decided to 
follow the plan of gluing the ribs      
together and protecting them with three 
coats of this varnish1 which seemed to  
possess the remarkable properties of    
being not only impervious to water1 but 
also unaffected by the application of   
concentrated ammonia or of gasoline1    
either of which produces immediate      
softening when applied to ordinary      
varnishes4  ,following the indication of
 these tests that the hollow1 round     

section1 #bb mm4 outside diameter by #ag
 mm4 inside diameter1 would probably    
give the best cross-rib for the weight  
that it seemed possible to allow1 a set 
of cross-ribs of this form was          
constructed and put in place in the     
large experimental wing1 in which the   
former solid ribs had been tested4 ,the 
wing was inverted and fastened into two 
posts at the angle it would have in     
flight1 the guy-wires from the p#aii    
lower guy-posts of the aerodrome being  
represented by wires stretched from the 
posts4 ,in actual use on the aerodrome  
it was proposed to have three main      
guy-wires running from each of the main 
cross-ribs to the lower guy-post1 but in
 the test1 which is now to be described1
 the wires which would have come nearest
 the body of the machine were left off  
to see what effect their removal would  
have on the wing4  ,the weight and      
dimensions of the wing1 as set up1 were 
as follows3 ,length of the main ribs1   
#bd feet2 length of the cloth covering1 

#bb feet2 width of the cloth covering1  
#aa feet2 total weight1 #bi pounds4 ,the
 two main ribs 7front rib and mid-rib7  
were solid1 #c4e cm4 in diameter at     
butt1 #b4e cm4 in diameter at tip1 and  
tapering from the middle to the tip4    
,there were twelve regular cross-ribs   
set #ej4h cm4 7#bj inches7 apart1 each  
rib being as above described1 #aa feet  
long1 #bb mm4 outside diameter by #ag   
mm4 inside diameter at the butt1 and    
tapering from where they were attached  
to the mid-rib to the tip1 and each     
weighing #cjj grammes4 ,there were two  
extra cross-ribs1 one at the inner end  
next to the body of the machine and the 
other at the outer end4 ,these were     
solid strips of wood #c4h cm4 wide by   
#a4b cm4 thick1 made extra wide and     
stiff in order to withstand the strain  
of stretching the cloth covering4 ,there
 was also a thin1 flat strip at the rear
 edge1 which connected together all the 
tips of the cross-ribs1 holding them a  
uniform distance apart1 and also serving

 to fasten the cloth4 ,the main mid-rib 
was stiffened in a vertical direction by
 a system of small guy-wires drawn over 
short guy-posts about #f inches high4   
,with the wing inverted and fastened in 
the way above described1 a weight of #b 
kilogrammes placed at the inner rear    
corner produced a deflection of #bf4g   
cm4 ,when the inner rear corner was     
pulled up by a spring balance until the 
balance registered #b kilogrammes1 there
 was an upward deflection of #da4c cm4  
,when the main mid-rib was held at the  
inner end1 the pull of #b kilogrammes1  
applied to the inner corner as before1  
caused an upward deflection of #be4d cm4
 instead of #da4c cm4 ,this wing was    
afterwards given a sanding test under a 
weight of #j4g pound per square foot4   
,with fine guy-wires fastened from the  
front of the cross-ribs to the tip and  
drawn just taut1 the ribs showed an     
average deflection of #i inches at the  
tip under the above weight4 ,when a     
small wooden guy-post was added under   

each of these small guy-wires1 the same 
weight produced an average deflection of
 #e inches at the tip of each rib under 
the same load4 ,in a previous test of   
the wing1 using hollow cross-ribs #af   
mm4 outside diameter by #aj mm4 inside  
diameter at the butt1 and only half as  
far apart as the later ones1 a load of  
#a pound per square foot on the wing    
produced an average deflection of #i    
inches at the tip of each rib when the  
cross guy-wires on each rib were held up
 by short guy-posts1 but when these     
short guy-posts were removed1 the same  
load produced a deflection of nearly #be
 inches at the tip of each rib4 p#bjj   
,although this wing was a great         
improvement in every way over any of the
 previous constructions1 it was felt    
that it was too weak for the large      
aerodrome4 ,further experiments were    
therefore made in order to secure a form
 of cross-rib which would meet the      
rigorous requirements imposed4 ,an      
inordinate amount of time was spent in  

the construction and tests of various   
forms of rib1 but as a result a         
satisfactory cross-rib was at last      
constructed of the form shown in ,plate 
#ff1 ,figs4 #d-h1 the dimensions at the 
three principal points1 viz41 first1    
where the cross-ribs join the front rib2
 second1 where they cross the mid-rib2  
and third1 at the rear tip1 being given 
both for the intermediate cross-ribs and
 the end cross-ribs4  ,following the    
plan employed by ,nature in the         
construction of the bamboo pole1 small  
partitions1 approximately one millimetre
 thick1 were placed every three inches  
in the thin1 hollow rib to keep it from 
being crushed4 ,the partitions were     
glued in place when the hollow rib was  
glued together on the form around which 
it was bent and clamped until the glue  
dried4 ,longer blocks were also inserted
 in each of the intermediate ribs at the
 point where it crossed the main rib and
 also at the front end where it was     
attached to the front rib4 ,in the end  

ribs blocks were also inserted at the   
points where the cross-braces were      
fastened to them for resisting the end  
stress due to the cloth covering4  ,upon
 making up one of these ribs and testing
 it1 it was found to possess remarkable 
stiffness1 so much so that it was       
thought probable that it was as stiff in
 proportion to its size as the best     
thing that ,nature had produced in the  
bird's wing4 ,a large quill from the    
wing of a harpy eagle was therefore     
stripped and the large end clamped in a 
special holder1 and measurements were   
made of the deflection produced by      
weights at various distances from the   
clamp4 ,as the main mid-rib of the wing 
of the aerodrome is placed approximately
 at the point of the center of pressure1
 the bending action on the cross-ribs   
may be assumed to act on a lever arm    
from the mid-rib towards the front1 and 
from the mid-rib towards the rear in the
 cases of the pressure on the front and 
rear portions of the wing1 respectively4

 ,in testing these cross-ribs1          
therefore1 against the quill1 the rib   
was clamped at the point where it       
crosses the mid-rib of the wing1 and    
measurements were made of the deflection
 produced by weights placed at various  
distances from the point of clamping    
both front and rear4  ,illustration3    
,,pl4 #ff  ,,details ,,of ,,ribs ,,and  
,,fittings ,,for ,,wings  ,illustration3
 ,,pl4 #fg  ,,cross ,,section ,,of      
,,ribs  ,the quill on which the         
measurements were made was #ai4e inches 
long and had a gradual curve1 the       
highest point of the curve being about  
the center of the length of the quill1  
and the depth of curvature being about  
#b inches4 ,when the butt of this quill 
was placed in the clamp the tip stood   
#ag cm4 above the horizontal4 ,the      
hollow spruce rib1 when clamped at a    
point #e feet from the tip 7the point   
from which it tapers in both directions7
 had its tip #b4b cm4 above the         
horizontal1 there being very little     

curve in that portion of the rib4 ,the  
quill weighed #d grammes when stripped  
and #ah inches of it projected from the 
p#bja clamp which held it during the    
tests4 ,the rear portion of the spruce  
rib projected #e feet from the clamp1   
being thus #c4c times as long as the    
quill1 and it weighed #abj grammes1 the 
weight for the larger size having1      
therefore1 increased slightly less than 
the cube of the length4  ,the results of
 the tests of both the quill and the rib
 are given in the following table4 ,the 
approximate cross-section of the quill  
at the point of clamping1 the middle and
 the tip are shown in diagrams ,a1 ,b   
and ,c1 respectively1 of ,plate #fg4    
,the cross-sections of the rib at the   
corresponding points are shown in       
diagrams ,d1 ,e and ,f4 ,the            
cross-sections of the quill1 enlarged   
five times1 are shown in diagrams ,a1   
,b1 and ,c4   ,,quill ,,from ,,the      
,,remiges ,,of ,,harpy ,,eagle4         
,weight1 #d grammes2 length1 #de cm42   

tip1 #ag cm4 above butt when the  latter
 is horizontal4    ,point of            
,weight  application   ,absolute     in 
terms   ,deflection  of weight          
weight in       of       in terms  in   
terms of    grammes4    greatest   of   
length4    length4                      
weight4    #j4ci           #ajej        
#a4j         4#ch    #j4dde             
#fje         #j4eh        4#ch    #j4ef 
#dje         #j4ci        4#ch    #j4ge 
#baj         #j4bj        4#ch    #j4ie 
#gg         #j4jge       4#ch   ,,hollow
 ,,spruce ,,rib4   ,weight1 #abj        
grammes2 length #aec cm42 section1      
rectangular2 tip1 #ag  cm4 above butt4  
,point of                    ,weight    
application   ,absolute     in terms    
,deflection  of weight     weight in    
of       in terms  in terms of          
grammes4    greatest   of length4       
length4                    weight4      
#j4ci        #ae1jjj         #a4j       
4#aa    #j4dde       #aa1djj            
#j4gf        4#aa    #j4ef              

#g1ijj         #j4ec        4#aa        
#j4ge         #d1jjj         #j4bg      
4#aa    #j4ie         #b1jjj            
#j4ace       4#aa  ,in each case the    
unit of length was the portion extending
 beyond the clamp2 the unit of weight1  
the greatest weight employed to produce 
the deflection4 ,it should be noted1    
however1 that the relative deflection   
was quite different in the two          
comparisons4 ,in the case of the quill  
the deflection was #ag cm4 in #de cm41  
or #ch per cent2 in the case of the rib 
it was #ag cm4 in #aec cm41 or #aa per  
cent4 ,in the case of the rib at the    
point #j4ci the absolute weight was     
#ae1jjj grammes1 the relative weight    
unity and the deflection in terms of    
length #j4aa4 ,while no rigorous        
comparison can be instituted1 since the 
rib was not deflected nearly as much    
proportionately as the quill1 yet the   
general inference is that while the rib 
was not intended to be1 and was not as  
elastic proportionately as the quill1 it

 was probably at least as strong in     
proportion to its weight4 ,briefly      
summarizing these results it will be    
noted that the spruce rib was about #c4c
 times the length and #cj times as      
heavy1 while it was #ae times as stiff  
near the butt and #bf times as stiff at 
the tip1 as the quill4  ,as this test on
 the rib for the large wings had        
apparently shown that the plan of       
constructing the ribs in the form of a  
hollow square secured maximum strength  
for minimum weight1 it was decided to   
construct a few sample ribs after the   
same plan for the wings of the new      
quarter-size model of the large         
aerodrome1 and to test1 these ribs in a 
similar manner4 ,the following table    
shows the results of the test on one of 
these ribs3   ,total length of rib  #hj 
cm4 ,curve  #a in #ah4 ,highest point of
  curvature  #j4be from front4 ,section 
of rib  #aj mm  #ad mm4 at the  point of
 attachment to mid-rib1 tapering to #h  
mm4  #ab mm4 at the  front point and to 

#g mm4  #b mm4 at the tip4 ,the rib was 
clamped  with the tip projecting p#bjb  
#df cm4 and was weighted at different   
percentages of its length to such an    
extent that it was deflected  #aa per   
cent of its length1 or #e cm4 ,the      
weight of the #df cm4 length  of rib    
which projected from the clamp was #aa  
grammes1 the whole rib  weighing #bb    
grammes and balancing on a knife edge   
placed at the  point where it was       
clamped4   ,point of         ,absolute  
,weight in      ,deflection  application
      weight        terms of       in   
terms  of weight        in              
greatest       of  in terms of          
grammes4      weight4        length4    
length4   #j4ci              #gfhj      
#a4j            #j4aa  #j4dde           
#eihj           #j4gh           #j4aa   
#j4ef              #cfhj           #j4dh
           #j4aa  #j4ge                 
#bcjj           #j4cj           #j4aa   
#j4ie              #aajj                
#j4adc          #j4aa  #a4jj            

#icj           #j4aba          #j4aa  ,a
 lighter rib than the above1 which was  
constructed at the same time1 was also  
tested with the results shown in the    
following table4 ,this rib was also #hj 
cm4 long1 but was only one-half the     
linear dimensions in section of the rib 
previously tested4 ,the rear portion of 
it projected #df cm4 from the clamp4    
,the total weight of the rib was #aa    
grammes1 or #e4e grammes for the #df cm4
 on which the measurements were made4   
,point of         ,absolute             
,weight in     ,deflection  application 
weight in      terms of      in terms   
of weight        grammes4       greatest
      of  in terms of                   
weight4       length4  length4   #j4ci  
#adjj            #a4j           #j4aa   
#j4dde             #aajj                
#j4ghe         #j4aa  #j4ef             
#gjj            #j4ej          #j4aa    
#j4ge               #djj                
#j4bge         #j4aa  #j4ie             
#bej            #j4agh         #j4aa    

#a4jj               #bbj                
#j4aeg         #j4aa  ,a still lighter  
rib of the same length1 weighing #i     
grammes1 suitable for use in the wings  
of the quarter-size model1 was          
constructed and a set of tests was made 
on it with the following results4 ,as in
 the above test1 #df cm4 of the rear    
portion of it projected from the clamp  
which held it4   ,point of              
,absolute       ,weight in              
,deflection  application      weight in 
terms of      in terms  of weight       
grammes4       greatest      of  in     
terms of                     weight4    
length4  length4   #j4ci                
#adej            #a4j           #j4aa   
#j4dde             #aaej                
#j4gie         #j4aa  #j4ef             
#gdj            #j4ea          #j4aa    
#j4ge               #chj                
#j4bfb         #j4aa  #j4ie             
#baj            #j4ade         #j4aa    
#a4jj               #ahj                
#j4abd         #j4aa  ,among quite a    

number of different forms of cross-ribs 
which were constructed of a size        
suitable for use in the model aerodrome1
 but made primarily for use in tests to 
determine the best form to employ1 may  
be mentioned the following1 in which    
both ribs were seven-sixteenths of an   
inch outside diameter and               
five-sixteenths of an inch inside       
diameter4 ,one was filled with elder    
pith1 formed up into a round rod that   
just fit the interior of the hollow rib1
 and was glued into it when the rib was 
glued up4 ,the other rib was left       
hollow4 ,upon testing these by          
suspending weights at different points1 
the rib without p#bjc the pith showed a 
slightly less deflection than the one   
with it1 it happening probably that the 
wood in one case was a little stiffer   
than in the other1 although they were   
carefully selected to be as nearly alike
 as possible4 ,the rib with the pith in 
it weighed #cd grammes and the one      
without it weighed #cj grammes4 ,it was 

inferred from this test that the placing
 of a light pithy material in the       
interior of the ribs would have no good 
effect1 and would not only add weight1  
but also complicate the construction4   
,the reason for making this test with   
pith in one of the ribs was that it was 
thought probable that the rib flattened 
out somewhat when it was deflected under
 a load1 and that the pith stiffened    
with the glue with which it was fastened
 in1 might lessen this4  ,as the        
cross-rib described above1 which was    
tested on ,october #bc1 #ahii1 seemed in
 every way suited for use in the wings  
of the large aerodrome1 a complete wing 
equipped with similar ribs but of       
slightly changed dimensions1 as shown in
 ,plate #ff1 ,fig4 #e1 was immediately  
constructed4 ,as previous tests had     
shown that the wing covering did not    
8flute0 or 8pocket0 to any considerable 
extent even when the ribs were as much  
as thirty inches apart1 only ten        
cross-ribs were used in this wing4 ,the 

eight intermediate cross-ribs were of   
the form described above1 but the ribs  
at either end of the wing were made of a
 larger cross-section and otherwise     
stiffened in order to resist the strain 
of the tightly stretched cloth covering4
  ,on ,april #ac1 #aijj1 a final sanding
 test was made on this wing1 guyed in a 
manner similar to that used in the      
aerodrome1 in which the following       
results were obtained3   ,,sanding      
,,test ,,of ,,large ,,wing4   ,area1    
#bfj sq4 ft42 weight of wing1 #bi       
pounds2 weight of sand on  wing1 #bca   
pounds2 total weight supported by wing1 
#bfj pounds1 or one  pound per square   
foot4   ,deflection of cross-rib1       
numbering from inner edge to extreme    
outer  edge of wing--      ,number of   
rib4   ,deflection4                     
,inches4   #a 7,heavy end rib7      #e4e
   #b                      #i4e   #c    
#aa4ge   #d                     #ab4be  
#e                     #ab4e   #f       
#ab4ge   #g                     #ab4i   

#h                     #ac4j   #i       
#ab4j  #aj 7,heavy end rib7     #i4ge   
,the weight of sand put on the wing in  
this test was #a4e times as great as the
 pressure which at this time it was     
expected would be imposed upon it in    
flight1 and was in fact #a4b times as   
great as the normal pressure when       
supporting the aerodrome as finally     
constructed4 ,even under this weight the
 greatest deflection noted in terms of  
the total length of the rib was less    
than #j4aj1 showing that the elastic    
limit of the rib was far from being     
reached4 p#bjd  ,as this test seemed to 
indicate that the wings constructed in  
this manner were certainly strong and   
rigid enough for use on the aerodrome1  
and that immediate further improvement  
could hardly be made1 three similar     
wings were at once constructed to       
complete the set4 ,somewhat later two   
additional wings were provided1 so that 
when the large aerodrome was taken to   
,widewater on the ,potomac in #aijc one 

and a half complete sets of wings were  
on hand1 which seemed to be ample to    
provide for any emergencies that might  
arise4  ,each of these wings had1 as is 
clearly shown in the drawings1 ,plates  
#ec and #ed1 two main ribs1 which formed
 the main strength of the framework and 
gave the wing longitudinal rigidity4 ,to
 the main front rib were attached the   
cross-ribs and the pieces for the curved
 extension later described4 ,the mid-rib
 extended across the cross-ribs1        
parallel to and about #e feet behind the
 front rib1 this being approximately the
 line in which lay the center of        
pressure of the wing4 ,it was upon this 
rib1 therefore1 that the greatest strain
 would fall4  ,the mid-rib1 ,plate #ff1 
,fig4 #b1 was #gca4e cm4 7#bd ft47 long1
 having at the butt an outer diameter of
 #ch mm4 7#a4e in47 and an inner        
diameter of #be mm4 7#a in471 the walls 
being1 therefore1 approximately #f4e mm4
 7#j4be in47 thick4 ,from the butt to   
the middle point the section was        

uniform1 but from this point it had a   
taper of one-twenty-fourth of an inch to
 the foot1 so that at the tip it had an 
outer diameter of #be mm4 7#a in471 the 
thickness of the wall being unchanged4  
,at the butt end a wooden block #h      
inches long was glued inside the rib1   
and at uniform distances of #ge mm4 7#cj
 in47 #aj smaller blocks were glued in  
where the cross-ribs were attached4 ,the
 main front rib was of the same form and
 size1 except that it was some #b inches
 shorter and had no blocks1 except the  
long one at the butt1 glued in it4  ,to 
these main ribs were attached1 in the   
manner later described1 the #aj         
cross-ribs1 to which the cloth cover was
 attached4 ,the #h intermediate         
cross-ribs have already been described  
in connection with the tests4 ,the      
cross-ribs at the end of the wings1 upon
 which greater lateral strains would    
come from the stretching of the cloth1  
were made of the larger cross-section   
shown in ,fig4 #h of ,plate #ff4        

,additional longitudinal stiffness was  
provided by gluing a strip #b mm4 thick 
between the upper and lower halves1 as  
shown in the section4 ,these end ribs1  
as well as those next to the ends1 had  
small blocks glued into them where they 
were crossed by the diagonal braces1 in 
addition to the small partitions #a mm4 
thick1 which were glued into the ribs   
every #c inches to prevent crushing1 and
 the blocks #b4e and #c inches long     
respectively1 where they were attached  
to the front rib and to the mid-rib4 ,at
 the extreme rear edge of the wing the  
cross-ribs were attached to the small   
8,d0-rib1 which served to hold the ribs 
at equal distances and to keep the cloth
 cover stretched tight4 ,this 8,d0-rib1 
as shown in ,plate #ff1 ,fig4 #c1 had   
semi-circular walls #d mm4 thick1 #ba   
mm4 in diameter1 to the edge of which   
was glued a flat strip #c mm4 thick4    
p#bje  ,as originally designed the wings
 had a curve of only #a in #ah1 the main
 front rib forming the leading edge of  

the wing4 ,later1 however1 it seemed    
desirable to 8quicken0 the curve and at 
the same time give the wing a sharper   
leading edge4 ,this was accomplished by 
attaching to the front rib1 at the      
points where the cross-ribs joined it1  
properly curved wooden pieces of the    
form shown in ,plate #ff1 ,fig4 #aj1    
over which the cloth cover of the wing  
was stretched4 ,the curve of the wing   
after the addition of this extension is 
shown in ,plate #ff1 ,fig4 #d1 and was a
 curve having a rise of approximately #a
 in #ab1 with the highest point 4#be    
from the front end4  ,on account of the 
large size of these wings and the       
consequent difficulty in handling them  
it was necessary to construct them in   
such a manner that they could be easily 
taken apart1 rolled up1 transported to  
the house-boat or any other point where 
they might need to be used1 and then    
quickly reassembled4 ,after much        
experiment as to the best means of      
constructing them1 the following plan   

was devised4 ,the cloth covering was    
permanently fastened to the front rib1  
to which were attached the front        
extension pieces by means of small metal
 clips secured by small wood screws4 ,on
 the rear edge of the front main rib1 at
 a uniform distance of #cj inches apart1
 #aj small metal horns of #a-mm4 tubing1
 #e cm4 long1 each brazed to an         
independent clamping thimble1 as shown  
in ,fig4 #i of ,plate #ff1 were         
fastened4 ,the front end of each of the 
cross-ribs was slightly rounded out to  
fit the front main rib1 and in the      
wooden block which was glued in this end
 of the cross-rib a hole was bored to   
fit these horns4 ,each of the cross-ribs
 was then pushed over its proper horn   
and against the front main rib1 and the 
cloth covering then drawn back toward   
the rear tips of the cross-ribs4 ,in the
 extreme rear edge of the cloth covering
 a seam was made1 and in this was       
inserted the 8,d0-rib already described4
 ,the cloth was then tightly stretched  

and a wood screw forced through the     
8,d0-rib and into and through the metal 
ferrule at the tip of the cross-rib4    
,near the inner and outer edges of the  
cloth covering eyelets were placed about
 #f inches apart1 through which small   
cords were then inserted and tied to the
 end cross-ribs4 ,the main or mid-rib   
was then placed on top of the cross-ribs
 and fastened to them with wood screws1 
and the cross-braces were then fastened 
on the top of the wing1 as shown in     
,plate #ed4 ,the frame of the wing was  
stiffened horizontally by cross         
guy-wires which passed from each        
cross-rib1 at the point where the       
mid-rib crossed it1 to the adjoining    
cross-rib1 at the point where it was    
connected to the front rib4 ,each of the
 main ribs was individually guyed1 in   
the manner clearly shown in ,plate #eb1 
in order to stiffen it in the vertical  
direction1 the fittings for these       
guy-wires being shown in detail in      
,figs4 #aa-ae of ,plate #ff4 ,finally1  

small guy-wires were run from the front 
end of the cross-ribs over a guy-post   
#ab inches high at the point where the  
cross-rib crossed the mid-rib to the    
rear tip of the cross-rib4 ,these cross 
guy-wires were regulated in p#bjf       
tightness by raising and lowering a     
screw in the slot of the head of which  
they rested1 and which was threaded in  
the end of the small guy-post4 ,upper   
and lower guy-wires1 running from the   
main ribs to the guy-posts on the       
aerodrome1 as already described1 and as 
is clearly shown in the drawings1       
,plates #eb and #ed1 completed the      
guy-wire system for the wings1 except   
for the 8drift wires10 which for the    
front wings were run from the lower side
 of the mid-rib to the bowsprit at the  
front of the machine1 and for the rear  
wings to the main frame4  ,each wing    
when completely assembled weighed       
approximately #bi pounds1 and had a     
rectangular surface #bb4e by #aa4e feet 
7measured on the chord of the curve71 or

 #bfj square feet1 making the weight per
 square foot equal about #ej grammes1   
rather less than #a4e times as much per 
square foot as the wings for the        
steam-driven models4 ,the total         
supporting surface of the aerodrome was 
#ajdj square feet1 and as the aerodrome 
when equipped for flight weighed1       
including the aviator1 #hej pounds this 
gave #a4bb square feet to the pound1 or 
#j4hb pound to the square foot4         
,although this was a somewhat larger    
proportion of weight to supporting      
surface than it had originally been     
expected to have1 there is every reason 
to believe that it was sufficient1 for  
the quarter-size model1 when weighted so
 that it had #a4bb square feet to the   
pound1 flew well1 as will later appear4 
p#bjg    ,,chapter ,,vii  ,,equilibrium 
,,and ,,control  ,in an aerodrome it is 
essential not only that its component   
parts shall be so disposed that the     
initial equilibrium is correct and      
highly stable1 but also that some       

efficient means be provided for quickly 
and accurately restoring the            
equilibrium1 if for any reason it is    
disturbed4 ,if the aerodrome is of      
sufficient size and power to carry a    
human being it is1 of course1 possible  
merely to supply an efficient means of  
controlling the lateral and horizontal  
equilibrium of the machine and depend   
upon the intelligence and skill of the  
operator1 as developed by practice and  
experience1 to maintain the proper      
equilibrium of the machine while in the 
air4 ,this method1 however1 is open to  
the objection that no matter how skilled
 the aviator may be there remains the   
probability of a serious if not fatal   
accident as the result of any momentary 
lapse or diversion of attention until   
the 8sense of equilibrium0 has been     
developed4 ,one of the chief problems1  
therefore1 which had impressed itself   
from the beginning of the work1 was to  
devise some means by which the          
equilibrium of the aerodrome would be   

automatically maintained under the      
varying conditions of flight1 so as to  
leave the aviator free1 as far as       
possible1 to control the direction of   
flight and to devote his attention to   
other important matters connected with  
the proper functioning of the various   
parts of the aerodrome4 ,in the         
development of the models it had been   
absolutely necessary to develop some    
efficient automatic control1 as they    
were far too small to carry an aviator1 
and the conditions of flight in the open
 air1 even on the calmest day1 were such
 that constant readjustments of the     
equilibrium were necessary4 ,the success
 attained in the automatic control of   
the equilibrium of the models had been  
so great1 and so much time would have   
been required for an aviator to acquire 
skill sufficient to control a machine   
without such automatic equilibrium1 that
 it was considered both expedient and   
safe to embody in the large aerodrome   
the plans which had proved so successful

 in the models4 ,it was necessary1      
however1 to provide in addition in the  
large machine means whereby the aviator 
could quickly and accurately either     
modify the action of the automatic      
devices or1 if desired1 entirely        
supersede the automatic control by      
purely manual control4 ,three distinct  
problems were1 therefore1 encountered in
 connection with the equilibrium and    
control of the large aerodrome4 ,in the 
first place1 the machine as a whole had 
to be so designed1 and its component    
parts so disposed as to secure a highly 
stable initial equilibrium2 second1     
automatic means had to be provided for  
p#bjh maintaining this equilibrium under
 the varying conditions of flight and   
for restoring it if for any reason it   
was disturbed1 and1 finally1 provision  
had to be made for the quick and        
accurate control of the flight by the   
aviator4 ,these problems1 while         
intimately related1 had to be met one by
 one and solved separately4  ,the       

general type of machine adopted was that
 which had been developed in the years  
of experiment with the steam-driven     
models4 ,from the very first            
consideration of the large aerodrome1 it
 seemed advisable to follow this type1  
which not only had shown itself to be   
distinguished by remarkable longitudinal
 and lateral stability in the tests1 but
 was actually the only type in the world
 which had at that time shown any       
possibility of successful flight4 ,there
 was1 of course1 a question whether     
single surface or superposed wings would
 be used1 and in spite of the negative  
results obtained in the tests of the    
models with the superposed wings1 it was
 felt that a considerable field for     
development was open in this direction4 
,however1 in spite of the advantages    
which theoretical considerations showed 
might be obtained through the           
introduction of this and various other  
modifications of the original type1 the 
whole teaching of past experience in the

 construction of the model aerodromes   
had been that success was more certain  
to be achieved by following the course  
in which genuine practical results had  
been achieved4 ,it was decided1         
therefore1 that in the construction of  
the large aerodrome the design should   
follow as closely as constructional     
conditions would permit the lines of the
 successful model ,aerodromes ,nos4 #e  
and #f1 which have already been fully   
described4  ,the longitudinal stability 
of an aerodrome is largely dependent    
upon the relation of three chief        
factors2 the center of pressure1 the    
center of gravity and the line of       
thrust4 ,for an aerodrome of the        
8,langley0 type1 the relative positions 
of these which give the greatest degree 
of stability had been determined as far 
as possible through the years of        
experiment with the models4 ,however1   
while it is the usual experience in     
designing machinery1 or even scientific 
apparatus1 that what appears            

theoretically to be the best plan has to
 be considerably modified for           
constructional reasons1 yet in the      
design of an aerodrome this is          
particularly true1 for not only must all
 the various parts function properly1   
both separately and as a whole1 but this
 result must be secured for the very    
minimum of weight4 ,experience alone can
 enable one to appreciate thoroughly how
 seriously this consideration of weight 
complicates the problem4  ,in making the
 original designs for the large         
aerodrome it had been recognized that   
the relative positions of the line of   
thrust1 center of pressure1 and center  
of gravity were much better in model    
,no4 #f than in model ,no4 #e4 ,from    
,data ,sheet ,no4 #a1 for ,aerodrome    
,no4 #e when it made its flight on ,may 
#f1 #ahif1 it will be noted that the    
line of thrust being assumed to be at   
the point #aejj1dc p#bji the center of  
gravity was at the point #adig1 and     
that1 assuming the rear wings to have   

two-thirds of the lifting effect of the 
front ones1 the center of pressure was  
calculated to be at the point #adih1 or 
one centimetre in front of the center of
 gravity1 measured in the horizontal    
plane4 ,in the vertical plane the center
 of pressure was calculated to be at the
 point #becf1 and the center of gravity 
was found by test to be at the point    
#beja1 when the line of thrust was      
assumed to be at the point #bejj1 the   
center of gravity being actually one    
centimetre above the line of thrust4    
,from the data sheet of ,aerodrome ,no4 
#f1 for its flight of ,november #bh1    
#ahif1 it will be noted that the line of
 thrust being at the point #aejj the    
center of pressure was at the point     
#adhg1 and the center of gravity at the 
point #adhd2 that is1 the center of     
pressure was three centimeters in front 
of the center of gravity1 measured in   
the horizontal plane4 ,in the vertical  
plane1 taking the line of thrust at the 
point #bejj1 the center of pressure was 

at the point #bebe1 and the center of   
gravity at the point #bdhf1 the center  
of gravity being #ad centimetres below  
the line of thrust and #ci centimetres  
below the center of pressure1 the       
distance from the center of pressure to 
the line of thrust being1 therefore1 #fd
 per cent of the distance between the   
center of pressure and the center of    
gravity4  ,as has been explained in     
,part ,i1 while it is not desirable that
 the center of gravity be a great       
distance below the center of pressure1  
as such a relation tends to produce a   
special kind of rolling and pitching in 
varying currents of air1 it is highly   
desirable that the center of gravity    
should lie some distance below the line 
of thrust in order that the three forces
 may be balanced4 ,in a machine like    
model ,no4 #e1 where the center of      
gravity was actually1 though very       
slightly above the line of thrust1 there
 is a constant tendency to produce      
rotation of the aerodrome1 if for any   

reason its equilibrium is disturbed1    
which is corrected in practice by the   
action of the ,pnaud tail4 ,in model    
,no4 #f1 on the other hand1 the         
disposition of the three factors was    
such that they tended to maintain1      
rather than to destroy1 the initial     
equilibrium of the machine4  ,these     
desirable relative positions had been   
made possible in model ,no4 #f by the   
fact that the center of gravity and line
 of thrust could be located at          
practically any desired point1 since    
with the use of steam the power plant   
consists of two separable parts1 the    
boiler1 with its fuel and water tanks1  
and the engine4 ,these parts can1       
therefore1 be placed in any part of the 
aerodrome that constructional or        
theoretical reasons demand4             
,furthermore1 the engine constitutes    
such a relatively small portion of the  
weight of the entire machine that1 if   
for any reason it is desirable to place 
the engine in the same plane as the line

 of thrust1 its weight is not sufficient
 to alter materially the position of the
 center of gravity1 since the boiler1   
water and fuel tanks can be placed as   
low as desirable and connected with the 
engine by suitable pipes4 p#baj  ,with a
 gasoline engine1 however1 the          
conditions are very greatly altered4    
,here the engine constitutes practically
 the entire weight of the power plant1  
only such accessories as the ignition   
coil1 batteries1 and carburetor being   
available for lowering the center of    
gravity1 unless the fuel1 cooling water 
tanks and radiator be placed below the  
engine and the liquids forced up by     
means of a pump4 ,in making the first   
designs for the large aerodrome1        
therefore1 it was found that it would be
 practically impossible to make the     
relative positions of the center of     
gravity and line of thrust the same as  
had existed in model ,no4 #f1 however   
desirable it might be4 ,the center of   
gravity could be brought appreciably    

lower than the line of thrust only by   
placing the gasoline engine in a plane  
considerably below that of the          
propellers1 and this necessitated the   
addition of at least two more sets of   
gears with heavy bearings and braces4   
,besides this almost prohibitive factor 
of weight1 it was also foreseen that    
great difficulty would be experienced in
 keeping even the two sets of bevel     
gears already necessary aligned and in  
proper condition for efficiently        
transmitting the power to the propellers
 unless the frame and other parts were  
made prohibitively heavy4 ,it was1      
therefore1 found necessary to bring the 
center of gravity practically in the    
same plane with the line of thrust1     
which made its general features as      
regards equilibrium more nearly resemble
 those of model ,no4 #e than of ,no4 #f4
  ,the weight of the aviator1 it is     
true1 constituted an appreciable part of
 the flying weight of the large machine1
 and it at first seemed possible to     

lower the center of gravity by placing  
him at a considerable distance below the
 line of thrust4 ,but it was recognized 
from the beginning that the aviator     
would probably have to give a great deal
 of attention to any form of engine in  
order to insure its working properly1   
and his position must1 therefore1 be    
selected with a view to the proper      
supervision of the engine and without   
regard to its effect on the center of   
gravity4  ,although the repeated        
successful flights of model ,no4 #e     
under varying conditions of wind and    
power inspired the belief that the minor
 adjustments1 as well as the general    
plan of the large aerodrome1 were such  
as to give highly stable equilibrium1   
nevertheless1 more direct corroboration 
of this opinion was desired1 and it was 
largely for this reason that the        
quarter-size model was constructed4 ,in 
it every detail of the larger machine   
which in any way affected its           
equilibrium was exactly reproduced to   

scale1 and the greatest care was taken  
that the same relative positions of the 
center of pressure1 the center of       
gravity and the line of thrust which it 
was proposed to employ for the large    
aerodrome should be used on the model in
 its flight of ,august #h1 #aijc1 which 
is later described4 ,the entire success 
of this flight1 so far as the balancing 
was concerned1 in spite of the fact that
 the engine worked erratically and that 
the launching speed was much less than  
it should have been1 removed every doubt
 p#baa that the equilibrium of the large
 aerodrome would be satisfactory under  
normal conditions4  ,the second problem 
encountered in connection with the      
balancing and control of the large      
aerodrome was that of providing an      
efficient means for maintaining the     
equilibrium under varying atmospheric   
conditions4 ,although much had been done
 toward the solution of this problem in 
the development of the models1 the whole
 question was reopened and thoroughly   

reconsidered in designing the large     
aerodrome4 ,the ,pnaud tail1 when made  
elastic or when more or less rigid1 but 
attached to the frame through an elastic
 connection1 and normally set at a      
negative angle1 furnishes a means of    
automatically controlling the           
equilibrium1 which is sufficiently      
sensitive and accurate to enable a      
machine to fly for a considerable       
distance1 at least in moderately calm   
weather1 as is evidenced by the various 
flights of the model aerodromes1 where  
there was no human intelligence to      
control them4 ,but owing to the         
principle of action of the ,pnaud tail1 
the flight of an aerodrome controlled by
 it must of necessity be more or less   
undulatory in its course4 ,furthermore1 
the tests with the models had indicated 
that1 while the ,pnaud tail served      
remarkably well as a means of           
controlling the equilibrium of the      
machine1 provided the balancing had been
 rather accurately determined1 and1     

further1 provided nothing happened to   
affect seriously the equilibrium of the 
machine1 it was limited in its          
effectiveness by its narrow range of    
action4 ,it was thought that a control  
mechanism which should be more sensitive
 and at the same time should act more   
powerfully to prevent the upsetting of  
the equilibrium when the machine was    
subjected to rather strong disturbing   
forces was desirable for any machine    
which was to transport a human being    
and1 therefore1 involved the risk of a  
fatal accident4  ,in the earlier period 
of the work and before the correct      
application of the ,pnaud tail to the   
model aerodromes had been found1 ,mr4   
,langley had planned a large number of  
different forms of automatic control for
 preserving the equilibrium of the      
machines4 ,the more frequently recurring
 of these were devices for changing the 
angle of the wings or tail1 and others  
for shifting the wings or tail bodily so
 as to shift the position of the center 

of pressure with respect to the center  
of gravity1 the motive power for        
operating the devices being in some     
cases that derived from a gyroscope or a
 pendulum1 and in others small electric 
motor apparatus controlled by a pendulum
 or a gyroscope4 ,most of these1        
however1 never reached the stage of     
development where they were actually    
tried on the machines in flight1 as the 
tests of some of them in the shop showed
 that they were unreliable1 while others
 were abandoned either when partly built
 or when only the drawings for them had 
been made4 ,among the better-preserved  
models of devices for this purpose which
 were in existence when the writer      
became associated with the work are     
those shown in ,plate #fh1 p#bab where  
the piece at the top is a pendulum      
7inverted or direct7 which controls the 
movement of the horizontal tail by means
 of the cords and apparatus shown1      
actuating these through the small       
electro magnets and apparatus attached4 

,just below the rod1 which represents a 
piece of the midrod1 are three parts1   
the first of which is a group of six    
little batteries clustered in a circle1 
while next to it is a system of needles 
hung in gymbals1 with electro-steering  
apparatus in cups which itself turns on 
a graduated base1 these electric        
connections1 together with the battery1 
controlling the vertical rudder4 ,on the
 right of this is another piece of      
apparatus for actuating windlass        
cylinders which turn one way or the     
other as the contact is made by one side
 or the other of the pendulum or the    
needle4 ,at the bottom1 on the two rods1
 is a tail-piece which automatically    
throws the center of pressure forward or
 backward according as the aerodrome    
departs one way or the other from the   
horizontal4  ,in spite of the fact that 
all the early attempts of ,mr4 ,langley 
to devise such a mechanical control had 
been very unsatisfactory1 the idea that 
something of this kind was necessary had

 never really been abandoned by him4    
,here was to be seen one of his chief   
characteristics1 which was never to     
abandon any idea that seemed valuable   
until it was brought to a successful    
issue or some very strong proof was     
developed that the idea was             
impracticable4 ,while on a trip abroad  
during the summer of #ahii1 and         
especially while resting at             
,vallombrosa1 ,italy1 ,mr4 ,langley's   
mind again turned to this problem1 and  
he wrote a number of very interesting   
letters emphasizing the importance of   
devising such a mechanism which should  
be controlled by gravity4 ,when he      
returned to the ,institution in the fall
 he insisted upon the same idea4        
,illustration3 ,,pl4 #fh  ,,automatic   
,,equilibrium ,,devices  ,illustration3 
,,pl4 #fi  ,,fig4 #a  ,,fig4 #b         
,,mechanism ,,of ,,control  ,a mechanism
 which had been devised by the writer   
for another1 but somewhat similar1      
purpose seemed to be well adapted to    

this end1 and it was accordingly decided
 to construct a small model of such a   
size as would be suitable for use on one
 of the steam-driven models4 ,the plan  
of control which it was proposed to     
follow was to have some mechanism which 
would control the angle of the tail     
through the action of gravity on a      
pendulum bob4 ,since it would require an
 exceedingly heavy pendulum should the  
deflections of it be directly utilized  
to produce corresponding movements of   
the tail1 the most feasible plan seemed 
to be to have a light pendulum1 which1  
while free to move under the action of  
gravity1 would nevertheless by its      
movement cause some outside force to    
produce corresponding and simultaneous  
movements of the tail4 ,the general     
scheme of arrangement is shown in ,plate
 #fi1 ,figs4 #a and #b4 ,this device    
consists essentially of a cylinder 7#a7 
in which is mounted a piston with the   
piston rod 7#c7 passing through the     
cylinder head and connected to the cord 

7#e7 which passes over the pulley 7#f71 
fastened to the tube 7#b71 which is     
slidably mounted on the midrod 7#g71    
whence it is carried over the pulley    
7#h7 on the guy-post 7#i74 ,from here it
 is connected to the spring 7#aj7 which 
is fastened by the p#bac bridle 7#aa7 to
 the upper side of the ,pnaud tail      
7#ab74 ,the other end of the piston rod 
7#c7 passes through the head in the     
other end of the cylinder1 and has      
connected to it a cord 7#ad7 which      
passes over the pulley 7#ae7 fastened to
 the tube 7#b71 whence it is continued  
over the pulley 7#af7 and is joined to  
the spring 7#ag71 which is connected by 
the bridle 7#ah7 to the lower side of   
the tail4 ,mounted on top of the        
cylinder 7#a7 is a valve chamber 7#bj7  
having ports leading to the two ends of 
the cylinder4 ,mounted in the valve     
chamber is a rocking valve surrounded by
 a bushing having ports in it1 and to   
which is fastened a rod 7#be7 which     
passes through the said valve and the   

head of the valve chamber4 ,fastened to 
the rod 7#be7 of the bushing is a lever 
7#bf71 which by means of the link 7#bg7 
is connected to the piston rod 7#c74    
,fastened to the rocking valve is a rod 
7#bh7 which telescopes over the rod     
7#be7 and also passes through the same  
head of the valve chamber1 and carries  
at its outer end a pendulum 7#bi7 on the
 lower end of which is the bob 7#cj74   
,if steam or any other fluid under      
pressure is furnished to the valve      
chamber through the pipe 7#ca71 none    
will be admitted to the cylinder so long
 as the pendulum is vertical or at right
 angles to the axis of the cylinder2 and
 the tail will be in its normal         
position1 which we will suppose to be an
 upward inclination of five degrees4    
,if1 now1 the front of the machine be   
depressed1 thereby causing the pendulum 
to move to the right1 such movement of  
the pendulum will cause the valve to    
open1 admitting fluid to the left-hand  
end of the cylinder4 ,this1 acting on   

the piston1 will force it towards the   
right1 which1 by means of the cord1 will
 cause the angle of the tail to be      
increased1 thereby causing the rear of  
the machine to be depressed and the     
front to be raised4 ,but as soon as the 
piston begins to move under the action  
of the fluid pressure it simultaneously 
moves the bushing which surrounds the   
valve by means of the connecting links  
and levers1 so that as soon as the      
piston has moved a distance proportional
 to the amount that the valve has been  
opened by the pendulum1 it causes the   
bushing to shut off the port and thus   
prevents further fluid entering the     
cylinder4 ,as soon as the aerodrome     
responds to the action of the tail the  
pendulum will1 of course1 begin to move 
back to its normal position of          
perpendicularity to the cylinder1 and   
will then open the valve to the other   
port1 thereby causing fluid to pass into
 the opposite end of the cylinder4 ,this
 fluid acting on the piston will move it

 in the opposite direction and thereby  
cause the tail to be drawn back to its  
normal position at the same time that   
the pendulum gradually reaches its      
normal position1 owing to the return of 
the aerodrome to its normal position4   
,in the explanation given above it was  
assumed that the slidable tube 7#b7 was 
in a fixed position4 ,it was planned to 
have the equilibrium normally maintained
 automatically and at the same time     
permit the operator to modify the       
automatic control and even to assume    
full manual control4 ,to secure this1   
the slidable tube 7#b7 was connected at 
each end to an p#bad endless cord 7#bj7 
which after passing over suitable       
pulleys was connected to the control    
wheel 7#ea7 at the aviator's car4  ,a   
model of this device was constructed in 
the spring of #aijj and was tested with 
steam pressure in the shop4 ,the test   
showed that the device acted immediately
 and with precision1 the piston         
performing movements simultaneously and 

in exact accordance with the pendulum4  
,the device1 however1 was never tried in
 a flight of any of the aerodromes owing
 to the lack of time necessary to       
properly install it on the machine4     
,furthermore1 it was thought probable   
that the rapid acceleration of the      
aerodrome at the moment of launching    
would so disturb the pendulum as to     
cause it to be in a very different      
position from that of vertical1 and also
 that the motion of the aerodrome       
through the air would itself be a       
somewhat disturbing factor4  ,because of
 the difficulties involved in this or   
any other mechanical device for         
controlling the equilibrium1 it was in  
every way advisable to retain in the    
large machine the ,pnaud system1 which1 
though itself imperfect in many ways1   
had been thoroughly tested in actual    
flight4 ,in the models1 it will be      
remembered1 the combined ,pnaud tail and
 rudder controlled the longitudinal     
equilibrium by movement in the vertical 

plane under the combined influence of   
its initial negative angle and the      
elasticity of its connection with the   
frame1 the flight being kept as nearly  
as possible in a straight line by the   
vertical surfaces of the tail4 ,although
 it was necessary that the large        
aerodrome should be capable of being    
steered in a horizontal direction1 it   
was felt to be unwise to give the       
combined ,pnaud tail and rudder motion  
in the horizontal plane in order to     
attain this end1 since the use of it for
 such a double function might very      
seriously interfere with its proper     
action in preserving the longitudinal   
stability4 ,it was1 therefore1 at first 
thought best to dissociate the rudder   
and tail so that the rudder might be    
used for horizontal steering without in 
any way interfering with the proper     
functioning of the tail4 ,but1 as the   
main desideratum was to obtain a flight 
of the large machine as soon as         
possible1 and perfection of steering    

control seemed secondary1 it was        
decided1 after further consideration1 in
 order not to risk the unpredictable    
effects that might result from small    
changes1 to duplicate on the large      
machine the combined ,pnaud tail and    
rudder of the model1 and to add another 
rudder for steering in the horizontal   
plane4 ,constructional requirements     
determined as the only available        
position for this rudder a rather       
disadvantageous one4 ,as will be seen   
from ,plate #ec1 its efficiency was     
diminished by its being only about half 
as far from the center of gravity as the
 combined ,pnaud tail and rudder1 and by
 being located in the lee of a          
considerable portion of the frame1 where
 it would be subject to the             
cross-currents of air created by the    
forward motion of the frame4 p#bae  ,for
 the preservation of the equilibrium of 
the aerodrome1 though the aviator might 
assist by such slight movements as he   
was able to make in the limited space of

 the aviator's car1 the main reliance   
was upon the ,pnaud tail4 ,but1 in the  
absence of any data for determining the 
effect produced in passing from the     
model to the large machine1 it could not
 be certain that calculations based upon
 the balancing of the model would       
accurately determine the proper         
balancing of the large machine4 ,it was 
therefore decided to provide such       
attachment for the ,pnaud tail that1    
while it would always have elastic      
connection with the main frame1 yet its 
angle could be appreciably changed      
without affecting in any way the degree 
of elasticity of this connection4 ,after
 many changes in plans for securing this
 result1 it was finally decided to      
arrange it in the manner shown in the   
drawings4 ,referring to the general     
plans in ,plates #ec and #ed1 and to the
 details in ,fig4 #a of ,plate #ef1 the 
main stem of the ,pnaud tail is seen to 
be connected by a pin to the horn 7#ag71
 which is brazed to the clamping        

thimble1 by which it is mounted on the  
vertical tube 7#af71 suitably connected 
and braced to the rear end of the       
midrod1 the horn 7#ag7 being larger than
 the stem of the tail and set at an     
angle to the vertical tube 7#af71 the   
pin connection permitting the tail to   
swing up and down4 ,the bridle 7#dj71   
connected to the center of the tail on  
its upper side1 passes upward where it  
is connected to the spring 7#da71 the   
other end of which is connected to a    
single wire rope 7#db71 which passes    
over the pulley mounted on the top of   
the post 7#dc71 which is guyed to the   
upper guy-post by the wire 7#dd74 ,the  
wire rope 7#db71 after passing over the 
pulley1 is connected to the spring      
7#de71 around the two ends of which it  
forms a loop1 and from there it passes  
down to the plane of the main frame and 
through suitable pulley blocks to the   
aviator's control wheel 7#ej71 which is 
mounted on the starboard side of the    
main frame1 convenient to the aviator's 

right hand when he is facing forward4   
,from this point the wire rope passes   
through the various pulley blocks       
towards the rear of the machine1 and    
through the pulley block 7#df7 mounted  
on the side and near the bottom of the  
rear lower guy-post4 ,at a short        
distance beyond this pulley it is       
connected to a weaker spring 7#dg71 the 
other end of which is connected by a    
second bridle 7#dh7 to the under side of
 the ,pnaud tail at its center4 ,in     
order to prevent the springs 7#da71     
7#de7 and 7#dg71 which furnish the      
elasticity for the ,pnaud-tail          
connection1 from being strained beyond  
their elastic limit1 either by a sudden 
gust of wind or by the aviator          
attempting to move so large an area of  
surface too suddenly1 the wire rope     
7#db7 was made continuous around the    
springs1 the portion between the points 
where it was joined to the two ends of  
the springs being made of such a length 
as to take the entire strain should the 

strain on the cord become greater than  
sufficient to stretch the springs #ej   
per cent of their original length4 p#baf
  ,in the construction of the           
equilibrium control wheel it was decided
 that some arrangement must be secured  
whereby the wheel would normally be     
inactive and maintain whatever position 
it had been set to1 and at the same time
 could be moved by the aviator with one 
hand1 the mere act of grasping it       
rendering it free to be moved1 and      
whereby it must automatically lock      
itself in any position in which it might
 be when the aviator removed his hand   
from it4 ,the multiplicity of things    
requiring the attention of the aviator  
made it desirable that his attention to 
any one of the important details1       
whether the engine1 the equilibrium1 or 
the steering1 should never require more 
than one hand1 thus leaving the other   
hand free either to hold on to the      
machine or to control some other detail 
at the same time4 ,while an irreversible

 wheel1 such as would be secured by the 
use of a worm and worm-wheel1 at first  
seemed likely to answer the purpose1 yet
 the movement of a worm-wheel by means  
of a worm is necessarily very slow if it
 is irreversible1 and it here seemed    
desirable to so arrange the wheel that  
in case of emergency1 of for rising or  
descending1 the aviator could swing the 
,pnaud tail from its extreme upper      
position to its extreme lower one by a  
small motion of his hand1 and thus small
 or large adjustments of the ,pnaud tail
 could be intuitively felt to have been 
produced without the aviator having to  
remember how many turns he had made of  
the wheel4  ,the control of the steering
 rudder was effected by a steering wheel
 7#ea7 similar in construction to the   
equilibrium control wheel 7#ej71 a      
continuous cord 7#eb7 passing from the  
steering wheel through suitable pulleys 
to either side of the steering rudder   
7r71 springs being interposed in loops  
in the cord on either side of the       

steering rudder to give some elasticity 
to the control apparatus in order to    
prevent possible danger from the aviator
 attempting to move the rudder too      
suddenly4 ,this steering rope passed    
directly through the steering rudder at 
the points where it was joined to it2 so
 that1 should one side of the cord in   
any way become entangled with the frame 
or with its pulleys1 the strain produced
 by the aviator in attempting to move it
 in the opposite direction would be     
taken up by the cord and thereby avoid  
the possibility of destroying the       
rudder4 ,for even should the cord become
 entangled on one side1 the rudder could
 be given a slight amount of adjustment 
through the elasticity of the coiled    
springs4  ,the design of the combined   
,pnaud tail and rudder followed very    
closely that which had been used for the
 models1 and its area of ninety-five    
square feet on the horizontal surface   
with a corresponding area of vertical   
surface bore the same relation to the   

area of the tail and rudder of the      
models that the area of the wings of the
 large machine bore to that of the wings
 of its prototype4  ,while the          
provisions for automatic equilibrium and
 manual control were not entirely ideal1
 even for the quiet atmospheric         
conditions under which it p#bag was     
proposed to make the first tests1       
nevertheless it was and still is        
believed that the provisions for such   
conditions were sufficient to enable a  
successful flight of a few miles to be  
obtained4 ,it was thought to be very    
certain that1 once a successful flight  
could be made1 the funds for the further
 prosecution of the work would be       
readily forthcoming1 and that when these
 funds were obtained the many problems  
of control1 rising and alighting1 could 
be undertaken4   p#bah    ,,chapter     
,,viii  ,,the ,,experimental ,,engine   
,it will be recalled that the contract  
for the engine for the large aerodrome1 
which had been entered into on ,december

 #ab1 #ahih1 called for its completion  
on ,february #bh1 #ahii4 ,between the   
time when the engine should have been   
completed and ,may1 #aijj1 the engine   
builder had been engaged in a continuous
 series of changes on it1 all connected 
with what might be briefly called its   
proper functioning4 ,the actual         
mechanical construction of the more     
important parts had been admirably      
executed1 and this main portion of the  
constructional work had been completed  
within the time called for by the       
contract4 ,the trouble was that the     
engine1 which was of the rotary cylinder
 type1 would not furnish anything like  
the power which had been expected of it1
 and which the size and number of its   
cylinders indicated that it should      
furnish4 ,no one who has not had        
practical experience in the development 
of gasoline engines1 can understand or  
appreciate how fourteen months could be 
spent in changes in the minor details of
 the engine with the expectation that   

each contemplated change would bring    
success2 and to anyone who has had      
experience in the matter1 an attempt to 
explain the delays would merely seem    
like a history of his own experiences4  
,it is1 therefore1 sufficient to say    
that the delay on the engine had now    
reached a point where it was necessary  
to bring it to a successful completion  
immediately or to abandon it definitely1
 and either find a competent builder who
 had already built engines which1 while 
not necessarily light1 were successful1 
and who would undertake to construct a  
light one on the same principles1 or1 as
 a last resort1 to turn to steam2 and   
even the contemplation of this was      
appalling4  ,on ,may #f1 #aijj1 the     
writer went to ,new ,york to see what   
could be done towards assisting the     
engine builder to complete the large    
engine and also1 if possible1 the small 
one which had been ordered for the      
quarter-size model later described4 ,he 
immediately made brake tests of the     

engine to determine accurately just what
 effects were being produced by the     
different changes the engine builder was
 making4 ,upon the first test the engine
 was found to develop only #b4hc        
horse-power1 and this could not be      
maintained for more than a few minutes1 
when without any apparent cause and     
without any signs of overheating the    
engine would altogether cease to develop
 any power4 ,after remaining in ,new    
,york for several weeks1 during which   
time many changes were made in the      
engine1 he finally got it to the point  
where it would develop four horse-power 
continuously2 but1 as it seemed         
impossible to get any better results    
p#bai without an indefinite amount of   
experiment1 it was decided that all hope
 of making this engine an immediate     
success would have to be abandoned4     
,interest in the development of the     
automobile was increasing at a rapid    
rate all over the world1 and while the  
builders in this country had not reached

 the stage of development which had been
 attained in ,europe1 especially in     
,france1 yet some ,american builders had
 succeeded in constructing cars         
propelled by gasoline engines which     
could be depended upon to run at least a
 short distance1 and it was1 therefore1 
hoped that some one of the more         
competent of these builders might be    
found who would undertake to construct a
 suitable engine4 ,after making a most  
extensive but fruitless search for such 
a builder in this country1 it was       
decided that it would be best to see    
what could be done in ,europe1 and as   
other administrative matters made it    
necessary for ,mr4 ,langley to go to    
,europe about the middle of ,june1 the  
writer accompanied him to see what could
 be done towards having a suitable      
engine built there4 ,some six weeks were
 spent in visiting all the important    
builders of gasoline engines in ,europe1
 and the results were very discouraging4
 ,everywhere the builders said that they

 did not care to undertake the work1 and
 that they did not consider it possible 
to construct an engine of #ab           
horse-power weighing less than #ajj to  
#aej kilograms 7#bbj to #ccj lbs471 or  
that1 if they had thought it possible1  
they would already have built it1 as    
they had had numerous inquiries for such
 engines1 and also wanted them for their
 own use4 ,the last hope of securing a  
suitable gasoline engine seemed to have 
vanished4  ,but1 discouraging as was the
 refusal of the engine builders of      
,europe to undertake to build the       
engine1 and still more so their opinion 
that such an engine was an              
impossibility1 inspection of the engines
 exhibited at the ,paris ,exposition had
 so strengthened the writer's conviction
 of the possibility of the undertaking  
that1 before parting with ,mr4 ,langley 
on ,august #c to return to ,america1 he 
personally assumed the responsibility of
 building an engine which would meet the
 requirements4  ,upon returning from    

,europe on ,august #ac1 and finding that
 the engine builder in ,new ,york had   
made no progress whatever towards       
improving the engine during his absence1
 the writer condemned both the large    
engine and the small one4 ,the engine   
builder had practically bankrupted      
himself in his attempts to construct    
these two engines1 having spent         
something like #hjjj or #aj1jjj in      
actual wages over and above the contract
 prices for the engines1 to say nothing 
of remuneration for his own time or such
 expenses as shop rent and power4 ,as   
all of the money for the large machine  
and practically all for the small one   
had been advanced to him at various     
times to assist him over financial      
stringencies--such advances1 however1   
having been secured by suitable         
bonds--it was decided to take the       
various parts of the two engines in     
p#bbj payment for the money which had   
been advanced1 as it was hoped that some
 of the parts of the engines might prove

 of use in experimental work4           
,immediately after the writer's return  
to ,washington he began work on the     
development of an engine4 ,taking some  
of the parts of the engine which had    
been condemned and constructing others1 
he was able by ,september #ah to have an
 experimental engine at work which1     
while not water-jacketed1 but           
provisionally cooled by wrapping wet    
cloths around the cylinders1 developed  
#ah-a_/b horse-power on the ,prony brake
 at #gae ,r4 ,p4 ,m41 the engine1       
including these wet cloths1 weighing    
#ajh pounds4 ,of course these wet cloths
 sufficed to keep the engine cool for   
only a short time--three to four minutes
 being the maximum4 ,this was only a    
temporary expedient for enabling the    
engine to run for a sufficient time to  
make brake tests and determine the power
 it developed1 but the results obtained 
were so very encouraging that it was    
decided to make water jackets for the   
cylinders of this engine and see what   

power it would then develop for more    
extended periods4  ,this experimental   
engine1 which was merely a 8patched-up0 
affair1 was first equipped with a       
sparking arrangement built on the       
wiping-contact principle4 ,with this    
sparking arrangement several important  
difficulties presented themselves1 among
 which may be particularly mentioned the
 great difficulty of so adjusting the   
sparking arrangements that the explosion
 in each cylinder occurred at exactly   
the same point in its cycle that the    
explosions occurred in all the other    
cylinders1 it being necessary to secure 
this result to a reasonably accurate    
degree in order to cause the engine to  
run smoothly enough to be used in the   
aerodrome4 ,where an engine has a large 
and heavy fly-wheel running at a high   
rate of speed1 the nicety of adjustment 
of the sparking arrangement is not so   
essential1 for the fly-wheel acts as a  
reservoir of energy and tends to smooth 
out the rough and jerky impulses which  

would be otherwise introduced by slight 
variations in the force of the          
explosions in the cylinders4 ,in        
constructing an engine for an aerodrome1
 however1 the permissible weight of the 
engine is so very small that the use of 
a fly-wheel having sufficient weight to 
act as an energy reservoir is           
practically prohibited4 ,another serious
 difficulty which was encountered with  
the wiping-contact type of sparking     
arrangement was that of keeping the     
stuffing boxes around the rotating      
contact rods tight enough to prevent    
leakage1 without at the same time       
binding and causing excessive friction4 
,although it seemed probable that the   
difficulties which have been mentioned1 
and other minor ones which were         
apparent1 could be remedied by further  
experiment1 yet the high tension or     
8jump-spark0 type of sparking apparatus 
seemed to offer much greater advantages4
 ,since it had fewer moving parts1 and  
furthermore since the wiping-contact    

sparking arrangement would have to be   
considerably modified in order to permit
 the construction of water jackets      
around the cylinders1 it was decided to 
construct a p#bba new sparking          
arrangement for the engine on the       
jump-spark principle4 ,after introducing
 this change in the engine it was found 
to run very much more smoothly and to   
require a minimum amount of care in     
adjusting it4  ,at the time that this   
engine was being developed it was       
practically impossible to obtain any    
outside information regarding the proper
 way of constructing it4 ,the little    
that was then known had been learned    
through laborious experience and at     
great cost by the experimenters who were
 attempting to build automobiles1 and   
was zealously guarded in the hope of    
preventing their rivals from utilizing  
the results of their labors4 ,it was the
 known custom1 however1 of all engine   
builders at this time to use a separate 
spark coil and a separate contact maker 

for each cylinder of an engine1 no      
matter how many cylinders there were4   
,this multiplication of the spark coils1
 which at that time were very heavy1 not
 only added greatly to the weight but   
also had the same defect that the       
wipe-spark type of sparking arrangement 
had of being exceedingly difficult to so
 adjust that all of the contact makers  
would perform their functions at exactly
 the same point in the cycle for each   
cylinder4 ,to obviate these             
difficulties1 both of adjustment and of 
excessive weight1 the writer devised    
what is supposed to have been at that   
time a new and valuable                 
multiple-sparking arrangement whereby   
only one battery1 one coil and one      
contact maker were utilized for causing 
the spark in all five cylinders1 a small
 commutating arrangement in the         
high-tension circuit distributing the   
sparks to the proper cylinders at the   
proper time4 ,this form of sparking     
arrangement was found upon test to work 

so satisfactorily that it was afterwards
 adopted for the small engine of the    
quarter-size model1 and also for the new
 and larger engine which was afterwards 
built and which will be described       
further on4 ,it is needless to describe 
in detail the many and perplexing       
difficulties which were experienced in  
procuring suitable spark coils1 spark   
plugs and other appurtenances of the    
sparking apparatus1 all of which at this
 time were in a very crude state of     
development1 there being only a few     
different makes on the market1 and most 
of these being very unsatisfactory4 ,one
 important minor improvement connected  
with the spark plugs may be described1  
as the beneficial effect produced by it 
was so very great that its use was      
continued in all future spark plugs for 
all of the engines4 ,this improvement1  
however1 is now incorporated in many of 
the plugs which are on the market1 and  
in some cases patents1 covering the     
particular form in which the improvement

 is incorporated1 are exploited by the  
manufacturer4 ,considerable difficulty  
was at first experienced with the spark 
plugs from a coating of soot 7resulting 
from the incomplete combustion of the   
gas and oil in the cylinder at the time 
of explosion7 which formed on the       
porcelain and thereby caused a          
short-circuit1 preventing the plug from 
working properly4 ,this was overcome by 
extending the metal portion of the plug 
for some distance into the cylinder1 and
 for something like three-quarters of an
 p#bbb inch beyond the end of the       
porcelain insulator4 ,the terminal which
 passed through the insulator was also  
extended for something like half an inch
 beyond the porcelain and bent to a     
proper extent to co-act with a piece of 
platinum wire inserted in the interior  
wall of the plug which formed the other 
terminal4 ,after making this improvement
 in the plugs practically no difficulty 
was experienced from short-circuits     
caused by the soot4  ,in making the     

tests of this experimental engine it was
 found practically impossible to absorb 
the power by a ,prony brake in a        
sufficiently uniform manner on account  
of the fact that the engine was being   
run without a fly wheel4 ,the consequent
 variation in the torque and speed      
during each revolution caused such great
 fluctuations in the reading of the     
scales which measured the pull of the   
,prony brake that no confidence could be
 felt in the accuracy of the readings   
and1 therefore1 no confidence could be  
placed in the determinations of the     
effect which different changes in the   
engine produced4 ,a water-absorption    
dynamometer consisting of a number of   
flat1 circular discs fastened to a shaft
 and rotating between other parallel    
flat discs arranged in a circular drum  
which was filled to any desired extent  
with water was immediately planned1 and 
the construction of two of them was     
begun so that power could be taken from 
both ends of the engine shaft1 which1 on

 account of its necessary lightness1 was
 apt to be injured by being twisted when
 all the power was taken from one end of
 the shaft4 ,in order to continue the   
tests on the engine while this          
dynamometer was being made it was       
decided to employ one of the propellers 
as a dynamometer4 ,although no accurate 
tests had been made to determine just   
how much power was required to drive    
these propellers at various speeds1 yet 
the fundamental law was known that under
 the same conditions the power required 
to drive any propeller would vary as the
 cube of the number of revolutions1 and 
since the ,prony-brake tests had given  
an approximation as to the amount of    
power which the engine developed at     
certain speeds1 the law of the          
propeller1 and extrapolations from the  
data obtained in the tests of the       
smaller propellers in #ahih1 enabled    
further approximations to be made as to 
the amount of extra power which the     
engine developed when certain changes   

enabled it to drive the propeller at    
increased speeds4 ,this method had also 
the great advantage that1 since the     
power required varies as the cube of the
 number of revolutions1 it is           
practically impossible for the engine to
 8run away0 with the propeller and cause
 serious damage through the possible    
excessive strains introduced by high    
speed4 ,this feature is also possessed  
by water-absorption dynamometers of the 
type which were built and used in the   
later tests4  ,the construction of water
 jackets for this engine proved an      
exceedingly formidable task1 it being   
impossible to braze the jackets directly
 to the walls of the cylinders without  
risk of ruining them4 ,it therefore     
became necessary to attach them by means
 of stuffing boxes1 which1 on account of
 their large size p#bbc and the         
necessity for keeping the weight a      
minimum1 was a most difficult piece of  
work4 ,the work was rendered still more 
difficult by the fact that the water    

jackets had to be made in halves which  
were brazed together after they had been
 fitted over the head of the cylinder4  
,even when the work was done in the most
 careful way this method of construction
 gave a great deal of trouble from the  
leaking of the stuffing boxes or the    
jackets themselves4 ,however1 after much
 delay1 the water jackets were finally  
completed1 and upon test the engine was 
found to develop #ba4e horse-power at   
#hbe ,r4 ,p4 ,m41 the engine itself     
weighing #abj pounds4  ,further changes 
were made in this engine1 especially in 
the pistons1 a new set of which were    
constructed which weighed #ae pounds    
less than the original set4 ,on account 
of the difficulty with the leakage of   
the water around the stuffing boxes of  
the water jackets1 and also from        
imperfections in the brazed joints of   
the jackets themselves1 it was found    
impossible to rely on the power that the
 engine would develop at any particular 
time1 as the water leaking from the     

jackets and running down on the spark   
plugs of the lower cylinders caused     
these cylinders to work erratically1 and
 this not only materially reduced the   
power but also caused jerky impulses in 
the absence of fly wheels4  ,it seemed  
so desirable to obtain as soon as       
possible a first test in actual flight  
of the large machine that the writer    
offered to put this engine in the       
aerodrome frame and make a test with it 
if the machine were launched over the   
water1 but with the launching track     
mounted directly on the river bank4     
,however1 ,mr4 ,langley felt it so      
necessary to make the initial test from 
the top of the house-boat and at an     
elevation of #cj feet or more that he   
would not consent to this1 and as the   
engine at its best did not develop quite
 #bd horse-power1 which had been        
calculated as the minimum which should  
be provided1 it was thought unwise to   
attempt to make the first test from the 
top of the house-boat until the         

aerodrome had been provided with engines
 that could be depended on to develop   
continuously not less than #bd          
horse-power4  ,it then became necessary 
either to build a duplicate engine and  
use both of them in the aerodrome1 the  
original plan as already explained      
having been to have two engines         
developing the #bd horse-power together2
 or1 second1 to construct an entirely   
new engine large enough to furnish a    
minimum of #bd horse-power and use this 
single engine4  ,as the construction and
 tests of this experimental engine had  
shown many places in which the weight   
might be safely reduced1 the writer     
decided to construct an entirely new and
 larger single engine1 and thereby avoid
 the extra weight and difficulties which
 would be introduced by having to use   
synchronizing gears where two engines   
were used1 it being impossible1 of      
course1 to run the two propellers from  
the two engines independently without   
risk of serious disaster4 p#bbd  ,it    

will be recalled that when the aerodrome
 was originally planned in #ahih it was 
proposed to have two engines of #ab     
horse-power each1 and the contract for  
the single engine of #ab horse-power    
provided that a duplicate was to be     
supplied1 if desired1 immediately upon  
the completion and delivery of the first
 one4 ,the calculations1 both from the  
whirling-table tests and from the       
results with the steam-driven models in 
actual flight1 indicated that #bd       
horse-power would be ample for the      
aerodrome1 which it was then expected   
would not exceed #fdj pounds in weight1 
with a supporting surface of #ifj square
 feet4 ,but it was found that the total 
weight of the machine was rapidly       
increasing on account of slight         
increases in the various details1 which 
when added together made a considerable 
increase in weight4 ,furthermore1 as it 
had been found difficult to keep all    
five of the cylinders of the            
experimental engine working uniformly1  

it was thought best to build this new   
engine sufficiently large to provide not
 only the extra power necessary because 
of the increased weight of the          
aerodrome1 but also to provide for      
further inevitable increases in weight1 
and over and above all this1 to provide 
also that the engine would furnish all  
the power necessary1 even though one of 
its cylinders should absolutely fail to 
work and act as a dead load on the      
others4 ,the writer accordingly designed
 this new engine to give #dj horse-power
 when all five of the cylinders were    
working1 and #bh horse-power even though
 one cylinder should act as a dead load 
on the others4  ,the various materials  
for the construction of this engine were
 ordered early in ,december1 #aijj1 with
 the promise of delivery not later than 
,january1 #aija4 ,owing to various      
causes1 however1 the major portion of   
the materials could not be obtained     
until late in the spring1 and1 in fact1 
a portion of them were not obtained     

until the summer of #aija4 ,during this 
period of delay1 however1 the engine for
 the quarter-size model was completely  
reconstructed and further tests were    
made with the experimental engine in    
developing accessories1 such as         
carburetors and spark coils4  ,the      
float-feed type of carburetor which was 
then coming into prominence in          
automobile work proved at that stage of 
its development to be totally           
unsuitable1 as the slight but constant  
tremor of the aerodrome frame1 when the 
engine was working at high speeds under 
a heavy load1 caused the float to act as
 a pump and periodically flood the      
carburetor4 ,this resulted in an        
irregularity of action of the engine    
which at times injured not only the     
transmission shafts1 gears1 and frame1  
but the engine itself by the serious    
pounding which occurred4 ,a form was    
next tried in which the gasoline was fed
 in through the valve seat of a lightly 
loaded valve which raised whenever there

 was suction in the inlet pipe1 the     
amount of gasoline fed being regulated  
by a pin valve4 ,later there were built 
several shapes and sizes of tanks filled
 with absorbent material1 which was     
saturated with gasoline and the surplus 
drawn off before starting the engine4   
,some of these tanks were provided with 
a jacket through which p#bbe a portion  
of the exhaust gases was passed in order
 to compensate for the cooling of the   
tank caused by the evaporation of the   
gasoline4 ,as a result of these tests it
 was found that a type consisting       
essentially of a tank filled with small 
lumps of a porous cellular wood 7tupelo 
wood7 which was initially saturated with
 gasoline1 and into which the gasoline  
was fed through a distributing pipe as  
rapidly as it was taken up by the air1  
which was sucked through it by the      
engine1 gave the best results4 ,instead 
of jacketing this tank1 the cooling     
effect due to evaporation was           
compensated by drawing the somewhat     

heated air from around the engine       
cylinders up through the loosely packed 
lumps of wood4 ,when tested in the shop 
this type was found to give such a very 
uniform mixture that the engine ran as  
smoothly and regularly as an electric   
motor1 the vibration in no way          
interfering with it1 and even when the  
sudden change from a state of rest to   
one of rapid motion through the air was 
imitated by suddenly turning on the     
carburetor the blast of several large   
electric fans from various angles1 it   
was found to have no appreciable effect 
on the running of the engine1 thus      
indicating that the trouble which was   
experienced with the model aerodrome in 
the trials of #aija was not likely to be
 repeated with the large aerodrome4     
,somewhat more than a dozen carburetors 
of various forms were constructed before
 this last type was devised1 but this   
proved so satisfactory that there were  
never thereafter any carburetor         
troubles4 ,in fact1 as will later       

appear1 a carburetor of this type kept  
the engine on the large aerodrome       
running at full power not only when the 
aerodrome was in a vertical position in 
the air1 but also after it had turned   
completely over on its back4   p#bbf    
,,chapter ,,ix  ,,the ,,quarter-,,size  
,,model ,,aerodrome  ,owing to the very 
considerable changes which              
constructional reasons necessitated in  
the relative positions of the center of 
pressure1 center of gravity1 and line of
 thrust from those which theoretical    
considerations pointed to as being best1
 it was decided in ,january1 #aijj1 to  
build a one-quarter-size model of the   
large aerodrome1 if a suitable engine   
capable of furnishing something like one
 and a half horse-power could be        
procured without delay4 ,it was hoped   
that it might be possible to construct  
this model immediately without seriously
 interfering with the progress of the   
work on the large machine1 and that some
 tests in free flight could then be made

 with it1 which would give very much    
more reliable data from which to        
determine the balancing of the large    
aerodrome than had been obtained from   
the tests of the steam-driven models    
,nos4 #e and #f4 ,a factor of           
uncertainty would still remain1 due to  
the difference in size between the large
 machine and the model1 which could be  
determined only by actual trial of the  
large machine itself2 but by making the 
model an exact duplicate1 on a smaller  
scale of the large machine1 very        
valuable results could be obtained4     
,tests of it in free flight would       
involve1 even with the probable         
attendant breakages1 a comparatively    
small expenditure of time and money4 ,a 
search was immediately begun for an     
engine builder who would undertake to   
furnish a suitable engine for this      
model4 ,the specifications called for an
 engine developing one and a half       
horse-power on the ,prony brake for five
 minutes without diminution in power    

caused by over heating4 ,while it was   
desired if possible to get an engine    
which would come within the given weight
 and develop the required power for a   
longer time than five minutes1 it was   
foreseen that the construction of a     
multiple-cylinder engine of so small a  
power made it necessary to resort to the
 air-cooled type1 and that such an      
engine would be doing exceedingly well  
to develop its maximum power            
continuously for as much as five        
minutes4 ,the only engine builder who   
could be found willing to undertake the 
construction of such an engine was the  
one already engaged in the construction 
of the larger engine4 ,as this builder  
was already twelve months behind in the 
delivery of the large engine1 it was    
felt that it would be unwise to give it 
to him1 both because the work on it     
might still further delay him in the    
completion of the large one1 and also   
because he was still having troubles    
with the large one1 which it was not    

certain he would ever be able to        
overcome4 ,after further consideration  
of the matter1 however1 it seemed so    
important to have a model which was an  
exact duplicate of the large machine for
 the p#bbg making of tests1 which might 
prevent not only serious damage but     
possibly fatal accidents1 that upon the 
assurance of the engine builder that the
 undertaking of the small engine would  
in no way interfere with the completion 
of the large one1 a contract was entered
 into on ,february #bc1 #aijj1 which    
specified that the engine should be     
delivered by ,april #a1 with a penalty  
for any delay beyond that date4  ,the   
frame for this quarter-size model was   
immediately begun and extra workmen were
 employed for work on it in order that  
its construction should in no way delay 
the completion of the large machine4    
,the decision to construct this         
quarter-size model of the large         
aerodrome had been made on the          
assumption that1 since it was to be     

one-sixteenth the weight of the large   
machine1 and therefore much heavier in  
comparison to its size than the steam   
models ,nos4 #e and #f1 it would1       
therefore1 not need to be so carefully  
constructed in order to obtain          
sufficient strength4 ,but when          
construction was actually begun it was  
found not only that the simpler and less
 expensive methods which it had been    
proposed to use in joining its frame    
together resulted in a weak             
construction1 but also that the time    
consumed in tinkering up the            
imperfections in the joints more than   
counterbalanced the extra time which    
would have been required to make the    
joints in the best manner from the      
beginning4 ,before going very far it was
 therefore decided to make the joints by
 following the same process which had   
been developed in the construction of   
the previous models4 ,the frame was     
accordingly built in the most           
substantial manner1 and when guyed by a 

system of guy-wires similar to that     
employed for the large machine it was   
found to be exceedingly stiff1 in fact  
very much stronger and stiffer than the 
frame of any of the preceding models4   
,in originally planning the model the   
intention was to make all its linear    
dimensions exactly one-fourth those of  
the large aerodrome4 ,before the designs
 were completed1 however1 it was seen   
from the previous experience with the   
steam-driven models that instead of the 
#fb4e-;cm4 propellers1 which a strict   
adherence to the quarter-size plan would
 demand1 it would be necessary to use   
propellers which were at least one metre
 in diameter4 ,moreover1 as the small   
engine would be more than one-fourth the
 size of the engine under construction  
for the large aerodrome1 a departure    
from the scale in the case of the       
transverse frame would be necessary4    
,the designs were therefore altered so  
as to admit of using the larger         
propellers1 and the tubes which formed  

the front of the transverse frame were  
bent1 as shown in the plan photograph1  
,plate #gj1 in order to give a large    
enough space for properly mounting the  
engine4  ,the frame with these          
modifications was completed in ,june1   
#aijj1 but no engine was ready for it1  
as the builder had failed to fulfill his
 contract for either the large or the   
small engine1 although several trips to 
,new ,york had been made to expedite    
their successful completion4 p#bbh      
,soon after this it became certain that 
the engines for both aerodromes would   
have to be constructed in the shops of  
the ,institution1 and owing to the      
greater importance of the experimental  
engine for the large aerodrome1 all the 
facilities of the shops were devoted to 
the early completion of it4 ,in         
,november1 #aijj1 however1 it was seen  
that the experimental engine alone would
 not furnish sufficient power for the   
large aerodrome1 and that a duplicate of
 it would have to be built or a new and 

larger engine designed and constructed1 
and that therefore it would be          
impossible to get the first tests of the
 large aerodrome in free flight before  
the following summer4 ,it was therefore 
decided that it would be best to suspend
 work temporarily on the large aerodrome
 and its engine1 and put all the workmen
 who could possibly be employed on the  
construction of the small engine1 so    
that it would be ready in time to permit
 some tests of the quarter-size model to
 be made during the following spring4   
,in order to expedite its construction  
as much as possible1 the attempt was    
made to utilize all the available parts 
from the small engine which had been    
undertaken by the engine builder in ,new
 ,york4 ,the cylinders1 which it had    
been expected would be kept cool by     
their rotation around the crank pin1    
were not well adapted for use as        
stationary cylinders1 since they were   
not provided with radiating ribs1 but it
 was hoped that by using them an engine 

could be very quickly constructed which 
would keep cool long enough to enable   
some short flights to be made with the  
model4  ,the work on this small engine  
was pushed forward very rapidly1 so that
 within a short time it was sufficiently
 complete to allow some power tests to  
be made with it4 ,in the first of these 
tests the attempt was made to measure   
the power by means of the ,prony brake1 
but as the engine had no fly wheel the  
fluctuations in speed during each       
revolution were so great as to make it  
impossible to obtain readings of any    
value4 ,when it was attempted to remedy 
this by putting a fly wheel on either   
side of the crank shaft of the engine1  
it was found that the sudden starting of
 the engine caused such severe strains  
in the crank shaft1 which had been built
 strong enough for driving the          
propellers but not for suddenly starting
 fly wheels having considerable inertia1
 as to make it unsafe to continue the   
use of fly wheels4 ,as without them the 

,prony brake could not be used1 it was  
decided to build a small                
water-absorption dynamometer on the same
 principle as the larger ones which were
 under construction for the large       
engine4 ,as this larger dynamometer has 
already been described1 it is only      
necessary to add that the small one     
consisted of twelve rotating plates and 
twelve stator plates twelve inches in   
diameter4 ,in order to avoid the        
construction of a special and elaborate 
testing frame for mounting the engine   
and the dynamometer exactly in line with
 each other1 it was attempted to connect
 them by means of a universal joint4    
,this 8short cut0 also proved the 8long 
way around40 ,the strains set up in the 
universal joint by the sudden starting  
of p#bbi the engine caused so much      
trouble on account of the inertia of the
 rotating plates of the dynamometer that
 the time lost in keeping the universal 
joint in working order during the tests 
more than counterbalanced the extra time

 which would have been required to      
construct a special wooden frame on     
which the dynamometer and engine could  
have been mounted in line with each     
other so that the crank shaft of the    
engine could have been directly         
connected to the shaft of the           
dynamometer4  ,much time was also lost  
in the effort to construct an apparatus 
by which a record could be obtained of  
the power actually used in propelling   
the aerodrome4 ,various methods were in 
use by which the thrust of the          
propellers could be more or less        
satisfactorily measured while the       
aerodrome was at rest1 but it was       
desired to know just how much power the 
aerodrome consumed while in actual free 
flight4 ,such a record it was hoped to  
obtain from a device incorporated in the
 propeller shafts4 ,this                
thrust-measuring device consisted       
essentially of a propeller shaft made in
 two sections1 one section telescoping  
the other for a short distance4 ,on the 

section of the shaft to which the       
propeller was attached there was mounted
 a drum1 having in its circumference two
 long slots diametrically opposite4 ,to 
the other section of the shaft a disc   
was fastened with two diametrically     
opposite rollers mounted on its         
periphery1 which fitted the slots in the
 drum of the other section4 ,a          
compression spring was interposed       
between the disc and the drum1 and the  
outside of the drum was so arranged that
 a strip of paper could be wound around 
and fastened to it which would serve as 
a chronograph sheet4 ,a pencil was      
fastened to the frame1 and1 since the   
drum was connected to the section of the
 shaft to which the propeller was       
attached and which therefore moved to   
and from the frame under the action of  
the propeller thrust1 a record of the   
actual thrust of the propeller at any   
particular moment could be obtained by  
simply pressing the pencil up against   
the paper on the drum and calculating   

the thrust from the calibration of the  
compression spring4 ,since the thrust   
would naturally be greater when the     
propellers were revolving in a moored   
condition1 during the few moments after 
the engine was started up and before the
 aerodrome was launched1 it was         
necessary to provide means for having   
the pencil point held away from the     
chronograph sheet until the aerodrome   
was launched1 and then have the point   
come to bear on the sheet4 ,this was    
accomplished by having the point held   
off by a small trigger arrangement which
 was to be released just at the moment  
that the aerodrome left the launching   
car4 ,a set of propeller shafts         
embodying this thrust-recording device  
was constructed1 but when they were     
actually tested on the aerodrome many   
difficulties were encountered which had 
not been anticipated4 ,in the first     
place the gasoline engine for the model 
was started up 7or 8cranked over07 by   
turning the propellers by hand4 ,a      

gasoline engine never starts slowly1 and
 on account of this suddenness of       
starting causes a very great strain in  
any p#bcj shafting by which it is       
connected to any driven mechanism4 ,the 
inertia of the driven mechanism1 even   
though it be apparently small1 becomes a
 most serious matter when an attempt is 
made to start up very suddenly4 ,this   
effect is very much intensified if the  
driven mechanism is connected to the    
engine through even one pair of gears1  
for there is always a certain amount of 
back-lash between the teeth of the      
gears1 and the effect of this back-lash 
is still further intensified when the   
driven mechanism is turned over by hand 
in order to start the engine1 as this   
takes up the back-lash on one side of   
the gears1 and the moment the engine    
starts permits a free movement until it 
suddenly takes up the back-lash and     
strikes the other side of the gear teeth
 with a blow4 ,the effect of this sudden
 starting of the engine proved most     

disastrous to the thrust-recording      
devices1 and1 although they were        
considerably strengthened1 it was found 
after a short time that in order to make
 them strong enough to withstand the    
shock of the sudden starting of the     
engine it would be necessary to make    
them inordinately heavy4 ,it was        
therefore decided to abandon all        
attempts to incorporate the             
thrust-recording device on this         
quarter-size model1 but it was hoped to 
install it later on one of the          
steam-driven models1 where the engine   
starts so slowly that there would be no 
need for excessive strength in it4  ,the
 engine for the quarter model when      
reconstructed with stationary instead of
 rotating cylinders was found in the    
shop tests referred to above to develop 
when working at its best between #a-a_/b
 and #b horse-power1 as measured by the 
absorption dynamometers4 ,however1 it   
was impossible to maintain this power   
steadily for more than #cj seconds4 ,in 

the first place1 the same difficulties  
7heretofore described7 that were met    
with in securing a suitable carburetor  
for the experimental engine were        
experienced at the same time in the     
development of the small engine4 ,in the
 second place1 as the engine had no     
cooling apparatus of any kind1 it was   
found that it could not be tested in the
 shop for more than #cj seconds owing to
 premature explosions4 ,it was hoped1   
however1 that by having everything ready
 for a flight before starting the       
engine1 it might be possible to launch  
the aerodrome before the cylinders began
 to heat seriously1 and that the greatly
 increased cooling effect due to the    
motion of the aerodrome through the air 
would permit the engine to develop      
sufficient power to secure a flight that
 would show whether or not the balancing
 was correct1 as the final disposition  
of some of the accessories on the large 
aerodrome could not be so well settled  
until it was known just how the         

calculated balancing of this new model  
corresponded with the actual balancing  
necessary for flight4  ,on account of   
,mr4 ,langley's reliance on the         
generally sound theory that where a     
successful method of conducting an      
experiment has been found only after a  
long series of failures it is best not  
to change to some unknown and untried   
plan1 it was impossible1 especially     
where failure in the test might involve 
a fatal accident1 to get him to deviate 
from his original plan of p#bca         
launching the large aerodrome from the  
top of the house-boat4 ,he apparently   
realized as well as anyone1 that in many
 respects the making of the test from   
the top of the house-boat had many      
serious drawbacks1 but he emphasized and
 impressed on the writer the importance 
of following as far as possible in the  
construction and test of the large      
machine1 the plans which had brought    
success with the models4 ,believing1    
however1 that there was probably a      

better method of launching the aerodrome
 than from the top of the house-boat1   
and that it would be well to prepare    
before hand as far as possible for      
following some other plan of launching  
immediately after a first successful    
test had been obtained from the top of  
the boat1 ,mr4 ,langley had constructed 
some floats which were arranged to be   
attached to the launching car of the    
quarter-size model so that the car could
 be converted into a catamaran raft4 ,it
 was not believed that this crude       
arrangement would suffice for a complete
 launching apparatus1 since the power of
 the aerodrome propellers would not be  
great enough to force the raft through  
the water at a sufficiently high speed2 
still it was thought that by having the 
launching car arranged in this way the  
model might be allowed to drive the raft
 rapidly through the water and thus give
 some idea as to what would be          
necessary1 in a more complete launching 
apparatus1 to obviate the danger of the 

drag of the raft causing the model to   
plunge over headlong into the water4    
,the launching car with these floats    
attached to it1 and with the            
quarter-size model mounted on the car1  
is clearly shown in ,plates #gc and #gd4
  ,while the results obtained with      
superposed wings in the tests of models 
,nos4 #e and #f in the summer of #ahii  
indicated that the 8single-tier0        
surfaces were much more efficient1      
still1 as has been already stated1 the  
great advantages of the superposed      
surfaces1 so far as strength of         
construction is concerned1 was fully    
realized at all times4 ,as a result of  
these tests it was decided to use the   
8single-tier0 surfaces in the first test
 of the large machine in order to insure
 as far as possible the best conditions4
 ,however1 it was from the beginning    
planned to construct superposed surfaces
 for use in the later tests of the large
 machine2 and1 in order to obtain more  
reliable data on such surfaces than had 

been obtained in the tests of the models
 in the summer of #ahii1 a set of       
superposed surfaces for the quarter-size
 model were constructed during the      
winter of #aijj-aija4 ,the quarter-size 
model1 equipped with these surfaces1 is 
shown in ,plates #ge and #gf1 where the 
model is seen mounted on its launching  
car1 which is attached to the floats    
heretofore referred to4 ,it was         
originally planned not to employ        
guy-posts when using the superposed     
surfaces1 but after the latter had been 
constructed and attached to the frame1  
it was found that they would have to be 
made with rigid joints instead of hinged
 joints if the guy-posts were omitted4  
,as the hinged joints1 however1 were    
already made1 and permitted the surfaces
 to be folded up so as to occupy a much 
smaller p#bcb space in shipping them1 it
 was decided to retain the hinged form  
of construction and use the guy-posts as
 shown in the above plates4             
,illustration3 ,,pl4 #gj  ,,plan ,,view 

,,of ,,quarter-,,size ,,model           
,,aerodrome1 ,,june #a1 #aijj           
,illustration3 ,,pl4 #ga  ,,plan ,,view 
,,of ,,quarter-,,size ,,model           
,,aerodrome  ,illustration3 ,,pl4 #gb   
,,end1 ,,side1 ,,and ,,three-,,quarter  
,,elevation ,,of ,,quarter-,,size       
,,model ,,aerodrome  ,illustration3     
,,pl4 #gc  ,,launching-,,car ,,with     
,,floats  ,illustration3 ,,pl4 #gd      
,,launching-,,car ,,with ,,floats       
,illustration3 ,,pl4 #ge                
,,quarter-,,size ,,model ,,aerodrome    
,,equipped ,,with ,,superposed          
,,surfaces1 ,,june #aa1 #aija1 ,,side   
,,view  ,illustration3 ,,pl4 #gf        
,,quarter-,,size ,,model ,,aerodrome    
,,equipped ,,with ,,superposed          
,,surfaces1 ,,june #aa1 #aija4 ,,end    
,,view  ,illustration3 ,,pl4 #gg        
,,cylinders ,,of ,,engine ,,of          
,,quarter-,,size ,,model ,,aerodrome    
,after much delay1 due to various       
causes1 the quarter-size model1 as shown
 in plan1 end elevation1 side elevation 

and three-quarter elevation in ,plates  
#ga and #gb1 respectively1 was taken    
down the river in ,june1 #aija1 in order
 to make some tests with it from the    
small house-boat1 which had been        
previously moved to the middle of the   
river opposite ,widewater1 ,va4 ,a test 
of it in free flight was made on ,june  
#ah1 its condition at this time being   
shown by ,data ,sheet ,no4 #ab in       
,appendix4 ,the launching apparatus     
worked perfectly and the aerodrome      
started off on an absolutely even keel1 
dropping only a few inches immediately  
upon leaving the launching apparatus1   
and continuing straight ahead directly  
into the light wind of something less   
than #b miles an hour4 ,after it had    
gone only about #ajj feet1 however1 it  
began to descend slowly1 but still      
maintained a perfectly even balance1 and
 finally touched the water about #aej   
feet from the house-boat1 having been in
 the air between #d and #e seconds4 ,it 
was immediately recovered1 and as soon  

as the wings could be dried out another 
test was made1 as it was thought        
probable that the wind had interfered   
with the carburetor to such an extent   
that the engine had not received the    
proper mixture of gas4 ,upon this second
 test the launching apparatus again     
worked perfectly and the aerodrome again
 flew straight ahead on a perfectly even
 keel1 and at a uniform height from the 
water until it had gone about #cjj feet1
 when it again began to descend slowly  
and finally touched the water about #cej
 feet from the house-boat1 having been  
in the air about #aj seconds4 ,while the
 tests were very disappointing1 owing to
 the extreme brevity of the flights1 yet
 they showed conclusively that the      
balancing of the aerodrome was correct1 
at least as far as motion in a straight 
line and in a quiet atmosphere was      
concerned4 ,as one and a half           
horse-power1 which was felt to be the   
very minimum which would successfully   
propel the aerodrome1 was furnished by  

the engine only when working at its very
 best1 and as the change in conditions  
from a quiet state to a velocity of     
something like #dj feet per second      
evidently caused a considerable drop in 
the power because of the change in the  
gaseous mixture which the carburetor    
furnished to the engine1 it was decided 
not to make any further test of the     
aerodrome until the engine cylinders    
could be reconstructed so as to provide 
more effective means for cooling it1 and
 thereby a reasonable margin of power   
above that actually necessary4 ,the     
aerodrome was accordingly returned to   
,washington for the purpose of making   
new cylinders for the engine4 ,in       
constructing these new cylinders the old
 cylinder heads from the previous       
cylinders were used in order to expedite
 their completion4 ,this proved in the  
end to be a very great mistake1 though  
at the time it seemed probable that the 
use of them would save much delay and   
considerable expense4 ,the new cylinders

 were constructed of steel tubing       
originally one-half inch thick1 which   
p#bcc was machined to the form clearly  
shown in the photograph1 ,plate #gg1    
where it will be seen that thin         
radiating ribs spaced one-quarter inch  
apart were formed integral with the     
cylinder1 the combustion chambers or    
heads being screwed on and brazed to the
 cylinders4 ,after much delay the new   
cylinders were completed1 and upon test 
it was found that while the radiating   
ribs assisted very greatly in keeping   
the engine cool1 yet the valves were so 
small that the gas was not able to get  
in and out of the cylinders rapidly     
enough to permit the engine to furnish  
its full power4 ,even at this stage it  
would have been better either to have   
made new cylinder heads with larger     
valves or to have made entirely new     
cylinders and cylinder heads1 but in the
 effort to economize time and money it  
seemed best to try to overcome part of  
the defect by adding an auxiliary inlet 

valve4 ,this was constructed1 and upon  
test it was found that1 although the    
engine developed #c4b horse-power on the
 ,prony brake at #ahjj ,r4 ,p4 ,m41 and 
even maintained #e4a horse-power on the 
brake for a few seconds when running at 
#cjjj ,r4 ,p4 ,m41 the ports leading    
from the valve chamber to the cylinders 
were so small that they became heated   
after the engine had run for #b minutes 
and premature ignition occurred1 which1 
of course1 immediately and very greatly 
reduced the power developed4  ,it was   
decided1 however1 in view of the tests  
in which the engine had developed #c4b  
horse-power at #ahjj ,r4 ,p4 ,m41 that  
there was sufficient margin of power to 
enable it to propel the quarter-size    
model1 even if it was not working at its
 best4 ,after concluding the            
,prony-brake tests on the engine1 it was
 mounted in its proper position in the  
aerodrome frame and connected to the    
propeller shafts4 ,some pendulum tests  
were then made1 showing an average lift 

of approximately #eg per cent of the    
total flying weight4 ,but it was found  
that the propeller and transmission     
shafts and their bearings would not     
stand the strain due to the increased   
power of the engine4 ,newer and stronger
 shafts and bearings were1 therefore1   
constructed and further pendulum tests  
were made4 ,it was then found that the  
transverse frame which supported the    
shafts and bearings was too weak1 and   
this was strengthened by substituting   
newer and thicker tubing where it seemed
 necessary4  ,these changes and repairs 
were all completed by ,october1 #aija1  
and the quarter-size model was at last1 
after months of delay1 felt to be in a  
condition which justified the           
expectation that its next flight would  
be entirely successful4 ,in view of the 
much more important work on the large   
aerodrome which demanded immediate      
attention the quarter-size model in this
 completed condition was put aside4     
,nothing more was done with it until    

,april1 #aijc1 when some shop tests were
 made preliminary to taking it to       
,quantico1 where1 on ,august #h1 it made
 a successful flight1 which is described
 in ,chapter ,,xii4   p#bcd    ,,chapter
 ,x  ,,construction ,,and ,,tests ,,of  
,,the ,,large ,,engine  ,the main       
requirement in an engine for an         
aerodrome--aside from reliability and   
smoothness of operation1 which are      
necessary in an engine for any kind of  
locomotion--is that it shall develop the
 greatest amount of power for the least 
weight4 ,it is1 therefore1 desirable to 
reduce the weight and number of parts of
 the engine to the very minimum1 so far 
as this can be done without sacrificing 
reliability and smoothness of running4  
,furthermore1 since the strongest metal 
for its weight is steel1 and since the  
greatest strength of steel is utilized  
when the stress acting on it is one of  
tension1 it is advisable to design the  
engine so that the parts which sustain  
the greatest strains shall be of steel  

and1 as far as possible1 meet with      
strains which are purely tensional ones4
  ,in designing the new engine for the  
large aerodrome it was1 therefore1      
planned to make it entirely of steel1 as
 far as this was possible4 ,the only    
parts which were not of steel were the  
bronze bushings for the bearings1 the   
cast-iron pistons1 and cast-iron liners 
of the cylinders4 ,previous experience  
had shown that1 while it is possible to 
use a cast-iron piston in a steel       
cylinder or even a steel piston in a    
steel cylinder1 provided the lubrication
 be kept exactly adjusted1 yet the      
proper lubrication of the piston and    
cylinder of a gas engine is difficult   
even under the most favorable           
conditions1 owing to the fact that      
excessive lubrication causes trouble    
from the surplus oil interfering with   
the sparking apparatus4 ,it was1        
therefore1 determined not to risk       
serious trouble by attempting to have   
the pistons bear directly on the steel  

walls of the cylinders4  ,while visiting
 the ,french engine builders in the     
summer of #aijj in the attempt to find  
one willing to undertake the            
construction of a suitable engine for   
the aerodrome1 it was pointed out to    
them that the great amount of weight    
which they claimed to be necessary for  
the cylinders1 and which they stated    
made it impossible for them to build an 
engine which would meet the requirements
 as to power and weight1 could be very  
greatly reduced by making the cylinders 
in the form of thin steel shells having 
cast-iron linings4 ,all1 however1 to    
whom this suggestion was made declared  
that it was impossible to build         
satisfactory cylinders in this way2 some
 of them even stated that they had tried
 it and found it impossible to keep the 
thin liners tight in the steel shells4  
,the difficulty which they had          
encountered is due to the difference in 
expansion of the steel and the iron when
 raised to a rather high temperature by 

the heat of the explosions1 if the      
cylinders are not well jacketed with    
water2 and if the steel p#bce shells are
 water jacketed they then do not expand 
as much as the cast-iron liners1 and    
this causes the latter to become 8out of
 round0 because of the compression      
strains produced in them when trying to 
expand more than the steel shells4 ,as  
past experience had shown1 however1 that
 it was possible to keep the liners     
tight in small cylinders1 it was        
believed that by taking proper care in  
the construction there would be no      
difficulty in this respect with the     
cylinders of this larger engine4  ,in   
carrying out these plans1 however1 of   
making the cylinders of steel1 numerous 
constructional difficulties were        
encountered which could not be foreseen 
when the design was made4 ,had they been
 foreseen1 provision for obviating them 
could easily have been made4 ,as will be
 seen from the drawing1 ,plate #gh1 the 
engine cylinders consisted primarily of 

a main outer shell of steel             
one-sixteenth of an inch thick1 near the
 bottom end of which was screwed and    
brazed a suitable flange1 by which it   
was bolted to the supporting drum or    
crank chamber4 ,these shells1 which were
 seamless1 with the heads formed        
integral1 were designed to be of        
sufficient strength to withstand the    
force of the explosion in them1 and1 in 
order to provide a suitable wearing     
surface for the piston1 a cast-iron     
liner one-sixteenth of an inch thick was
 carefully shrunk into them4 ,entering  
the side of the cylinder near the top1  
was the combustion chamber1 machined out
 of a solid steel forging1 which also   
formed the port which entered the       
cylinder and was fastened to it by      
brazing4 ,the water jackets1 which were 
formed of sheet steel 4#jbj inch thick1 
were also fastened to the cylinder by   
brazing1 and it was in connection with  
the brazing of these water jackets that 
the first serious difficulty was met in 

the construction of the engine4 ,in the 
first place1 as the jackets were of an  
irregular shape and of a different      
thickness of metal from the walls of the
 cylinder to which they were joined1 the
 expansion and contraction due to the   
extreme heat necessary for properly     
brazing the joints caused such serious  
strains in various and unexpected       
directions that it was only by          
exercising the very greatest care and   
patience that a completely tight joint  
at all points of the jacket could be    
secured4 ,in the second place1 the size 
of the cylinders and the consequently   
large extent of water-jacket surface1   
complicated the problem4 ,the           
maintenance over this large surface of  
the extreme heat necessary for brazing  
involved discomfort and1 indeed1 actual 
suffering to the person engaged in the  
work1 and much care and skill were      
demanded in so distributing the heat    
that the temperature of the surface of  
the jackets would be uniform enough to  

prevent serious strains from expansion  
and contraction4 ,as no workman could be
 found either competent to do the work  
or willing to undergo the personal      
discomfort1 the writer was obliged to do
 all this brazing work himself4 ,besides
 the difficulties due to the expansion  
and contraction of the jackets while    
they were being brazed1 the greatest    
care had to be exercised to avoid       
heating the cylinders so hot as to      
weaken the p#bcf joint where the        
explosion chambers were joined to the   
cylinders1 which1 of course1 had been   
brazed before the jackets were fitted to
 them preparatory to brazing them4      
,another great difficulty was that the  
ring which encircled the cylinder near  
the middle of its length1 and which     
formed the bottom part of the water     
jacket1 expanded very much more than the
 cylinder itself1 so that1 if it was    
brazed to the cylinder before the jacket
 was brazed to it1 the heat of brazing  
the jacket to the ring would cause the  

ring to break loose from the cylinder2  
while if the ring was not previously    
brazed to the cylinder1 but was brazed  
after the jacket had been brazed to it1 
the very much greater heat required for 
brazing the ring to the cylinder caused 
the spelter to burn out of the joint    
between the jacket and the ring4        
,furthermore1 it was found very         
difficult to braze the two joints at the
 same time1 since in brazing the ring to
 the cylinder it was best to have the   
cylinder in an inverted vertical        
position1 so that the spelter could be  
made to flow evenly around the ring and 
form a fillet against the wall of the   
cylinder1 while in brazing the jackets  
to the ring it was best to have the     
cylinder in the reverse vertical        
position or lying on its side so that   
the spelter could properly flow into    
this joint4 ,finally1 however1 after    
what proved to be most exasperating and 
tedious work1 the five cylinders        
necessary for the engine were completed 

and a series of tests was immediately   
made4 ,during the course of these tests 
the water circulation became obstructed 
in several instances1 and the consequent
 high temperature to which the cylinders
 and jackets were raised caused severe  
strains in the jackets which1 in turn1  
produced breaks in the brazed joints4   
,these breaks had to be rebrazed1 and in
 brazing them it was necessary in almost
 every case to remove the cast-iron     
liners and rebraze the entire jackets   
from start to finish1 as the application
 of the intense heat necessary for      
brazing at any one point produced such  
severe strains that before the break    
which was being repaired could be       
completed other breaks developed at     
various points of the jacket4 ,it was1  
therefore1 necessary to get the whole   
jacket up to a fairly uniform heat and  
complete the brazing while it was in    
this condition1 and then keep the whole 
cylinder at a uniform but gradually     
decreasing temperature until it had     

sufficiently cooled off4  ,on account of
 these troubles with the water jackets  
and the cylinders1 it was decided to    
build some extra cylinders1 not only    
because past experience had suggested   
improvements in detail in the           
construction of the jackets1 which would
 prevent to a large extent the great    
troubles which had been met with in the 
brazed joints1 but also to insure having
 sufficient cylinders to enable the     
engine to be always in working          
condition1 even though several of the   
cylinders might be out of commission    
from slight imperfections in the jackets
 or at other points4 ,while the         
construction of these new cylinders     
involved a repetition of the arduous    
task of brazing1 yet the minor          
improvements which were introduced p#bcg
 proved eminently successful in         
providing against future troubles from  
leaky jackets4  ,illustration3 ,,pl4 #gh
  ,,engine ,,of ,,aerodrome ,a4         
,,section ,,through ,,cylinder ,,and    

,,drum  ,illustration3 ,,pl4 #gi        
,,engine ,,of ,,aerodrome ,a4 ,,end     
,,elevation1 ,,port ,,side              
,illustration3 ,,pl4 #hj  ,,engine ,,of 
,,aerodrome ,a4 ,,top ,,plan            
,illustration3 ,,pl4 #ha  ,,engine ,,of 
,,aerodrome ,a4 ,,elevation ,,starboard 
,,bed ,,plate1 ,,sparking ,,mechanism   
,the general form of construction of the
 engine with the improved cylinders will
 be readily understood from the         
drawings1 ,plates #gh-ha1 in which      
,plate #gh is a detail sectional view1  
previously referred to1 through one of  
the cylinders2 ,plate #gi is an end     
elevation of the port side1 ,plate #hj  
is a plan view1 and ,plate #ha is an    
elevation of the starboard bed plate    
which supports that side of the engine1 
and by which it was fastened to the     
aerodrome frame1 this view showing      
particularly the sparking apparatus     
which was mounted on the bed plate4 ,the
 engine consists primarily of a single  
crank shaft provided with a single crank

 pin1 the shaft having bearings in a    
drum which consists essentially of two  
heads4 ,arranged around the crank shaft 
and attached at equidistant points of   
the drum are five cylinders4 ,mounted on
 the port side of the crank shaft and   
close to the crank arm is a small gear1 
which through suitable gears mounted on 
the port head of the drum drives a      
double-pointed cam which has a bearing  
on the exterior of the hub of the drum4 
,the ratio of these gears is such that  
the cam is driven at one-quarter the    
speed of the crank shaft1 and in the    
reverse direction4 ,mounted on the      
exterior side of the port head of the   
drum are five punch rods1 the upper ends
 of which are within a sixty-fourth of  
an inch of being in contact with the    
exhaust-valve stems of the cylinders1   
and on the lower end of these rods are  
hardened-steel rollers which rest on the
 double-pointed cam--this one cam thus  
serving to operate the exhaust valves of
 all five of the cylinders4 ,the port   

head of the drum is connected to the    
port bed plate1 by which it is          
supported1 by means of a flanged bushing
 in which are formed tongues and grooves
 which fit into corresponding grooves   
and tongues formed in the hub of the    
drum1 it being necessary to have a      
certain amount of space between this bed
 plate and the head of the drum to      
provide room for the exhaust-valve cam  
and its co-acting punch rods4 ,the      
starboard bed plate is fastened to the  
starboard head of the drum by bolts     
which draw the web of the bed plate     
against the face of the drum4 ,the      
sparking gears are driven by means of a 
gear formed on a sleeve which telescopes
 over the hub of the starboard drum1 and
 has a bearing thereon1 the end of the  
sleeve terminating in a ring which is   
fastened to the crank shaft4  ,since the
 five connecting rods must center on the
 one crank pin1 the bronze shoes in     
which they terminate can occupy only a  
portion of the circumference of the pin1

 and with the relative proportions which
 here existed between the length of     
stroke of crank and the length of the   
connecting rod1 the circumferential     
width of the connecting-rod shoes was   
slightly less than sixty degrees1 thus  
leaving uncovered a crank space of about
 one-sixth of the circumference1 which  
it was necessary to have in order to    
provide room for the change in relative 
position of the shoes due to the        
angularity of the connecting rods4 ,in  
p#bch the experimental engine the       
connecting-rod shoes were all given     
their bearing directly on the crank pin1
 as heretofore described1 being held in 
contact therewith by means of cone nuts1
 which were screw-threaded to the crank 
pin1 the taper of the cones permitting  
adjustment for wear4 ,this method of    
connecting these parts to the crank pin 
is the usual plan of connecting three or
 more connecting rods to one crank pin4 
,so much trouble had been experienced   
with the water jackets and with minor   

defects in the experimental engine that 
no long runs had been possible with it1 
and consequently no trouble had been    
experienced because of the small amount 
of bearing area provided by this method 
of joining the connecting rods to the   
crank pin4 ,when1 however1 the new      
engine was completed it was found that  
after working at high power for a few   
minutes the connecting-rod shoes heated 
so rapidly that it was impossible to run
 the engine for more than ten or twelve 
minutes1 the excessive heating of the   
shoes causing a great diminution in     
power besides the danger of serious     
damage if the tests were continued      
longer4 ,at first this defect seemed    
almost fatal1 as there appeared to be no
 way of providing sufficient bearing    
area for the five connecting rods on one
 crank pin4 ,happily1 however1 the      
writer was able to overcome this defect 
by an improved design which enables all 
five connecting rods to operate on the  
one crank pin1 and at the same time     

provides each with the full amount of   
bearing area which it would have were it
 the only connecting rod operating on   
the crank pin4 ,this arrangement        
consists essentially of a main          
connecting rod formed of a steel forging
 terminating in a sleeve which encircles
 the crank pin and is provided with a   
bronze lining for giving a proper       
bearing surface between the connecting  
rod and the crank pin1 both the steel   
sleeve and the bronze lining being      
split1 but at right angles to each      
other1 to permit assembling them on the 
crank pin4 ,this steel sleeve1 the upper
 half of which is formed integral with  
the main connecting rod is rounded off  
to a true circle on its exterior        
circumference1 except at the point where
 the rod joins it4 ,the other four      
connecting rods terminating in bronze   
shoes are then caused to bear on the    
exterior of this sleeve1 being held in  
contact therewith1 and permitted to have
 a sliding motion thereon sufficient to 

take care of the variation in angularity
 of the connecting rods1 by means of the
 cone nuts which are screw-threaded to  
the sleeve and locked thereto by means  
of the jam nuts1 as shown in the        
drawings4 ,the main connecting rod1 of  
course1 acts in the same way as in the  
ordinary case where each cylinder has   
its separate crank pin4 ,the other four 
connecting rods deliver their effort to 
the crank pin through the sleeve in     
which the first connecting rod          
terminates1 and they1 therefore1 do not 
receive any of the rubbing effect due to
 the rotation of the crank pin1 except  
that of slipping a very short distance  
over the circumference of the sleeve    
during each revolution1 the amount of   
slipping depending on the angularity of 
the connecting rod4 ,this improved type 
of bearing was successful from the time 
of its first trial1 and even in later   
p#bci tests in which the engine was run 
for ten consecutive hours at full power 
it showed no signs whatever of          

overheating4 ,as this new form of       
connecting-rod bearing for the crank pin
 had never been tried before1 the       
precaution was taken to leave the       
threads on the crank pin for the cone   
nuts1 so that if this new bearing should
 not prove successful the old plan of   
having the connecting-rod shoes bear    
directly on the crank pin could be      
reverted to4 ,these threads are clearly 
seen in ,plate #gh and were never       
removed from the crank pin1 though their
 removal would have added considerably  
to the area of the bearing surface of   
the main connecting rod1 had more       
bearing surface seemed necessary4  ,the 
lubrication of the main crank-shaft     
bearing and of the crank pin was        
effected by means of a small oil cup1   
fastened to the port bed plate1 which   
fed oil through a hole in the hub of the
 drum to a circular groove formed in the
 bronze bushing in the hub4 ,the crank  
shaft being hollow1 a hole was drilled  
through it in line with the groove in   

the bushing1 and the oil was then led   
from the interior of the crank shaft    
through a pipe connected to the plug in 
the end thereof1 and through a hole     
drilled in the crank arm to the hollow  
crank pin4 ,small holes through the     
crank pin permitted oil to pass to the  
exterior thereof and thus oil the       
bearing of the main connecting rod4     
,small holes through the sleeve and     
bushing of the main connecting rod fed  
oil under the shoes of the other four   
connecting rods1 the small holes being  
placed in oil grooves formed in the     
interior of the bronze bushing4 ,the    
lubrication of the pistons was effected 
by means of small crescent-shaped oil   
cups fastened to the outer wall of the  
cylinders1 which distributed the oil    
equidistantly around the circumference  
of the pistons1 through small tubes     
which projected through corresponding   
holes drilled in the cylinder wall4     
,these oil cups for the cylinders were1 
while small1 of sufficient size to      

furnish a supply for approximately one  
hour1 and were so positioned on each    
cylinder as to have a gravity feed4 ,it 
may be mentioned here that while there  
were many parts of the engine which were
 of unprecedented lightness there was   
nothing which excelled these oil cups in
 this respect1 as they were made of     
sheet steel 4#jjc of an inch thick1     
riveted and soldered up4 ,the           
crank-shaft bearing in the starboard    
drum was oiled from an oil cup mounted  
on the outside of the bed plate and     
connected by a pipe to a hole in the    
inner wall of the drum1 which was       
connected to the oil grooves in the     
bronze bushing in the hub of the drum4  
,the first set of pistons for this      
engine were similar in design to those  
shown in the assembled drawings1 except 
that they had side walls and heads which
 were twice as thick as those shown4    
,these lighter pistons were constructed 
later1 and were just as good as the     
earlier and heavier ones4 ,it will be   

noted that the pistons have two deep but
 thin ribs reinforcing the head4 ,the   
pistons were slightly tapered from the  
middle1 where they were 4#jje inch      
smaller than the cylinder bore1 toward  
the outer end1 where they were 4#jjge   
inch smaller p#bdj than the bore4 ,the  
outer piston ring was 4#jjce inch       
narrower than its groove1 the second one
 4#jjc inch1 the third 4#jjbe inch1 and 
the inner one 4#jjb inch narrower than  
its groove4 ,the rings were bored       
one-sixteenth inch off center with the  
exterior surface1 and had one-eighth    
inch diameter of spring4 ,they were of  
the lap-joint type1 with the sides of   
the laps carefully fitted and only      
one-sixty-fourth-inch clearance at the  
ends of the laps to allow for thermal   
expansion4 ,as no grinding facilities   
were obtainable in ,washington1 the     
cylinders were carefully bored smooth   
and free from taper1 and the pistons    
were worn in to a perfect fit by running
 them in by a belt for twenty-four      

hours1 with copious oil supply4  ,the   
main connecting rod was #g_/h-;inch     
diameter and solid1 while the other four
 were of the same diameter but with a   
#e_/h-;inch hole in them4 ,the gudgeon  
pins in the pistons were hollow steel   
tubes #g_/h-;inch diameter and          
case-hardened1 and were oiled entirely  
by the oil thrown off by centrifugal    
force from the crank-pin bearing1 the   
oil running along the connecting rods   
and through suitable holes at the heads 
into oil grooves in the bronze bushings 
in these heads4  ,since on an engine for
 an aerodrome the best plan for         
releasing the exhaust gases from the    
engine is to get rid of them as soon as 
possible1 so long as they are released  
behind the aviator and do not interfere 
with his view in the direction of       
motion1 it was decided to have the gases
 exhaust immediately from the combustion
 chambers2 but in order to prevent their
 playing on and heating the main bearing
 of the crank shaft in the port drum the

 combustion chambers were each provided 
with a chamber below the exhaust-valve  
seat1 with a side outlet therefrom4 ,the
 manifold pipe through which the gaseous
 mixture was supplied to the inlet      
valves of the engine consisted of a tube
 bent to a circle and having five branch
 tubes1 each leading to one of the      
automatic inlet valves1 which fitted    
removable cast-iron seats fastened by a 
nut in the upper part of each combustion
 chamber4 ,the very small amount of     
clearance between the engine and the    
frame necessitated that this pipe be cut
 in three places and joined by flanges  
in order to properly assemble it on the 
engine when the latter was mounted in   
the frame4 ,the carburetor1 which was   
placed near the rear of the aviator's   
car1 was connected through suitable     
pipes to this circular inlet pipe1 at a 
point horizontally in line with the     
center of the shaft4 ,the auxiliary air 
valve consisted of a sleeve rotatably   
mounted on the vertical pipe leading    

from the carburetor to the manifold1    
holes in the sleeve being brought to    
coincide more or less with holes in the 
vertical pipe1 by the operator1 when    
more or less air was required or when he
 wished to vary the speed of the engine4
 ,the cooling water for the jackets of  
the cylinders was led to them through a 
circular manifold pipe on the starboard 
side connected by a vertical pipe with  
the centrifugal pump situated at the    
lower point of the lower pyramid of the 
aerodrome frame4 ,the heated water was  
led from the jackets through another    
p#bda circular manifold pipe on the port
 side1 through two connections to the   
radiating tubes at the front and rear1  
respectively1 of the cross-frame4 ,these
 radiating tubes1 which were provided   
with thin radiating ribs soldered to    
them1 finally led the cooled water to   
the tank situated in the extreme rear of
 the aviator's car1 a suitable pipe from
 the bottom of this tank being connected
 to the inlet side of the centrifugal   

pump4 ,the centrifugal pump was driven  
by means of a vertical shaft connected  
to the crank shaft through a set of     
bevel gears which drove it at three     
times the speed of the engine4 ,the     
bearings through which these gears were 
connected were mounted on the port bed  
plate1 and in order to allow for a      
certain amount of vibration between the 
engine and the pump this vertical       
connecting shaft had a telescoping      
section connected through suitable      
splines4  ,the sparking apparatus       
comprised1 first1 a primary sparker     
similar to the simplest form of such    
devices which have since come into      
common use1 where a cam driven by the   
engine co-acts with a pawl on the end of
 a spring1 but in this case1 as this    
sparker was used for all five cylinders1
 the cam was driven at a speed of two   
and one-half times that of the engine   
shaft1 thus making and breaking the     
primary circuit five times in each two  
revolutions of the engine4 ,second1 a   

spark coil1 the primary terminals of    
which were connected to the primary     
sparker and to a set of dry batteries4  
,third1 a secondary distributor         
consisting of a disc carrying a contact 
brush and driven at a speed one-half    
that of the engine1 this brush being    
constantly connected through a contact  
ring to one of the terminals of the     
high-tension side of the spark coil and 
running over the face of a five-section 
commutator1 each of the sections of     
which was connected to a spark plug1 the
 other high-tension terminal of the     
spark coil being1 of course1 grounded on
 the engine frame4 ,this sparking       
apparatus was first constructed by using
 blocks of red fibre for insulation4    
,after the engine was completed and was 
being tested difficulties were met with 
in the sparking apparatus which at that 
time appeared inexplicable4 ,after a    
great deal of annoyance and loss of time
 it was finally discovered that the red 
fibre was not as good an insulating     

medium as it was supposed to be1 owing  
to the zinc oxide used in making it4 ,in
 damp weather the sparking apparatus    
absolutely refused to work1 and it was  
found that the moisture in the air      
caused the zinc oxide in the fibre to   
nullify its insulating qualities4 ,this 
trouble1 after being located1 was cured 
by substituting hard rubber for the red 
fibre4  ,at the time when this engine   
was built1 as well as earlier when the  
experimental engine was built1 it was   
impossible to procure any wire which had
 been properly insulated to withstand   
the high voltages necessary for the     
connections between the high-tension    
side of the spark coil and the secondary
 distributor1 and from the secondary    
distributor to the spark plugs in the   
cylinders4 ,while at this time this     
appears a very simple matter1 yet the   
trouble experienced and p#bdb the delays
 caused by the lack of such small       
accessories which are now so easily     
procurable were very exasperating1 and  

it was finally necessary to insulate    
these wires by covering them with       
several thicknesses of ordinary rubber  
tube of different diameters telescoped  
over each other4  ,in the early tests of
 this new engine1 which were made with  
it mounted on a special testing frame   
and delivering its power to the         
water-absorption dynamometers1 the      
engine was operated without any fly     
wheels1 and1 so far as its smoothness of
 operation was concerned and its ability
 to generate its maximum power1 it did  
not require any4  ,after the completion 
of the tests on the testing frame the   
engine was assembled in the aerodrome   
frame1 which was first mounted on the   
floor of the launching car4 ,the car    
itself was mounted on a short track in  
the shop1 which arrangement provided a  
smoothly rolling carriage which could be
 utilized for measuring the thrust of   
the propellers by merely attaching a    
spring balance between the rear of the  
car and a proper holding strap on the   

track4 ,in the first tests of the engine
 under these conditions1 it was found   
that while the engine itself did not    
require any fly wheels1 yet the lack of 
them caused trouble with the            
transmission and propeller shafts1      
which1 while it had never been          
anticipated1 was easily understood when 
it was encountered4 ,this difficulty was
 caused by the 8reverse torque10 which  
fluctuated from a maximum to a minimum  
five times during each double revolution
 of the engine1 and which set up        
fluctuating torsional strains of such   
magnitude in the transmission and       
propeller shafts that the shafts        
themselves became exceedingly hot after 
a few minutes operation of the engine1  
and under more prolonged periods of     
operation these fluctuating torsional   
strains caused a permanent twisting and 
bending of the shafts4 ,the transmission
 and propeller shafts were at first made
 of tubing one-sixteenth of an inch     
thick1 but these were abandoned both on 

account of the necessity of abandoning  
the screw-thread method of attaching the
 flange couplings and gears1 and also   
because these shafts had been designed  
when it was expected to transmit only   
twelve horse-power to each propeller1   
while the increase of power in the large
 engine necessarily required much       
stronger shafts4 ,the first shafts which
 were actually tested in the frame were1
 therefore1 one and one-half inches in  
diameter by three-thirty-seconds of an  
inch thick1 the tubing having been      
one-thirty-second of an inch larger     
originally and turned down to this size 
to insure a straight shaft4 ,when these 
shafts twisted under the action of the  
reverse torque of the engine1 a very    
much heavier set1 practically twice as  
thick1 were constructed4 ,when used in  
the tests these heavier shafts1 while   
much stronger1 still showed a large     
amount of heating due to the fluctuating
 torsional strains4  ,upon calculation  
it was found that by providing specially

 light fly wheels the major portion of  
this reverse torque could be eliminated 
for a less increase p#bdc in weight than
 would be occasioned by sufficiently    
increasing the thickness of the         
transmission and propeller shafts to    
safely stand it4 ,since it was desired  
to concentrate as much as possible of   
the weight of the fly wheels in the     
rims1 the idea at once suggested itself 
of building them up like a bicycle wheel
 by means of tangent spokes4 ,two steel 
automobile-wheel rims were therefore    
procured thirty-three inches in         
diameter1 and these were provided with  
tangent spokes connected to special     
steel hubs fitted to the crank shaft of 
the engine4 ,the rims themselves not    
being quite heavy enough1 and           
constructional reasons necessitating    
their being at different distances from 
the center of length of the crank pin1  
the extra weight which it was desired to
 give to these rims was provided by     
means of steel wire wound tightly around

 and fastened to the rims1 the weight of
 each rim being made inversely          
proportional to its distance from the   
center of the crank pin4 ,the first     
spokes which were used for these wheels 
were standard bicycle spokes            
three-thirty-seconds of an inch in      
diameter1 but these were soon found to  
be entirely too weak to withstand the   
sudden strains due to the rapid starting
 of the engine4 ,they were therefore    
replaced by standard spokes one-eighth  
of an inch in diameter1 but these also  
proved too weak and were later replaced 
with special spokes made in the shop out
 of ,no4 #aj coppered-steel wire1 which 
by test was found to have a tensional   
strength of #baib pounds4 ,as these     
steel rims were only one-sixteenth of an
 inch thick and had not been made       
exactly true1 but had been straightened 
before being used1 it was found that    
they very quickly went out of shape     
under the strain due to the centrifugal 
force at high speeds1 and also when the 

engine was suddenly accelerated4 ,as    
long as they did stay true1 however1 it 
was found that they were sufficiently   
heavy to provide all of the fly-wheel   
effect it was necessary to have in order
 to eliminate all trouble from the      
reverse torque4  ,after further         
consideration1 it was decided that the  
only means of constructing a fly wheel  
which would have a stiff rim and at the 
same time would not be heavier than the 
steel ones1 which had been found        
adequate1 was by perpetrating what would
 at first sight appear to be an         
absurdity4 ,a new set of rims for the   
fly wheels was made by constructing them
 of an aluminum casting1 the section of 
the rim being ,u-shaped4 ,after         
machining these rims and assembling the 
fly wheels with them1 it was found that 
they were many times stiffer than the   
previous steel ones of the same weight1 
and after this change no further trouble
 was experienced in keeping the fly     
wheels perfectly true1 even under the   

most severe strains4 ,in fact1 on one   
occasion when the engine broke loose    
from the propellers1 it ran to a speed1 
which1 while not exactly known1 yet     
reached the limit of the tachometer1    
which was #bjjj ,r4 ,p4 ,m41 without    
injury to the fly wheels4  ,it will be  
recalled that in starting up the engine 
on the quarter-size model1 the initial  
8cranking0 necessary with a gasoline    
engine was accomplished by p#bdd having 
two of the mechanics turn the           
propellers4 ,while this same plan might 
have been followed in the case of the   
large aerodrome1 yet it would have      
involved some danger to the mechanics   
and would also have left the aviator    
without any means of restarting the     
engine should it for any reason stop    
while in the air4 ,believing it to be   
very important to provide means for     
enabling the aviator to restart the     
engine in case it stopped in the air1   
the writer devised the starting         
mechanism shown in the drawings1 ,plates

 #gh to #hj4 ,fastened by tongues and   
grooves to the port side of the engine  
crank shaft1 just outside of the bed    
plate1 is a worm wheel1 on the hub of   
which is mounted the bevel gear which   
drives the water-circulation pump       
through the bevel pinion1 as already    
described4 ,mounted on the web of the   
bed plate are two brackets1 in which the
 shaft for the starting crank is        
journaled1 this shaft passing forward   
and downward through the front of the   
cross-frame of the aerodrome1 where it  
is journaled in a bracket secured to the
 brace tubes thereof4 ,at the front or  
lower end of the shaft a crank handle is
 connected thereto by a ratchet         
mechanism4 ,the upper end of the        
starting shaft1 between the bearings of 
the two supporting brackets1 is tongued 
and grooved1 and slidably mounted       
thereon with co-acting grooves and      
tongues is a worm screw which1 in the   
position shown in ,plates #gi and #hj1  
is in gear with the worm wheel just     

described4 ,however1 when the worm screw
 is slid along on the shaft until it is 
against the upper bracket it is out of  
gear with the worm wheel4 ,mounted in   
the interior of the tubular starting    
shaft is a spring-pressed pawl plug1 not
 shown1 but which projects through one  
of the tongues on the shaft near the    
upper bracket4 ,if the worm screw is    
slid up against this upper bracket1 this
 pawl catches in a radial hole in the   
worm screw and holds it in this position
 out of gear with the worm wheel4       
,connected to this pawl plug and passing
 longitudinally through the center of   
the shaft is a wire which terminates in 
a button just at the end thereof4 ,by   
pulling on this button the operator may 
release the worm and thus permit it to  
slide downward so that when the starting
 crank is turned in a clockwise         
direction the worm will screw itself    
into gear with the worm wheel1 and any  
further turning of the starting crank   
will cause the worm to force the worm   

wheel1 and1 consequently1 the engine    
shaft1 around in a clockwise direction4 
,as soon as the engine gets an explosion
 the worm wheel slides the worm along   
against the upper bracket1 where the    
spring pawl catches and holds it till it
 is again released by the operator as   
before4  ,this starting mechanism was a 
success from the first1 and the engine  
was never started up in any other way4  
,with an aerodrome having the qualities 
of automatic equilibrium1 which the     
,langley machines have1 it was felt very
 certain that by this mechanism the     
engine could be easily restarted while  
in the air1 in case it was inadvertently
 stopped4 p#bde  ,the reason for        
building the engine with five cylinders 
instead of some other number1 and for   
arranging them radially on a central    
drum using only one crank pin may not   
appear quite obvious4 ,the advantages   
gained by such a construction1 however1 
are very great1 and may be briefly      
summed up as follows3  ,first1 since in 

a gas engine of the four-cycle type     
there is only one explosion in each     
cylinder every two revolutions1 and the 
crank shaft and crank pin therefore are 
loaded only one-quarter of the time for 
each cylinder1 it is obvious that by    
having four cylinders arranged radially 
around a central drum the load on the   
bearings of a single crank shaft and    
crank pin may be kept very uniform4     
,however1 with four cylinders thus      
arranged it is impossible to have the   
cylinders explode and exert their effort
 on the crank at uniform intervals in   
the cycle1 it being necessary to have   
the cylinders explode in the order of   
#a1 #c1 #d1 #b1 #a1 etc41 thus giving   
intervals between explosions of #ahj    
degrees1 #ij degrees1 #ahj degrees1 #bgj
 degrees1 etc41 or to have them explode 
in the order of #a1 #c1 #b1 #d1 #a1     
etc41 thus giving intervals of #ahj     
degrees1 #bgj degrees1 #ahj degrees1 #ij
 degrees1 etc4 ,on the other hand1 with 
any odd number of cylinders the         

explosions will occur at equal intervals
 in the cycle4 ,with three cylinders    
they will explode in the order of #a1   
#c1 #b1 #a1 etc41 or at equal intervals 
of #bdj degrees1 while with five        
cylinders they will explode in the order
 of #a1 #c1 #e1 #b1 #d1 #a1 etc41 or at 
equal intervals of #add degrees4 ,it is 
therefore seen that there is a great    
advantage in smoothness of operation and
 uniformity of torque of the engine     
through having an odd number of         
cylinders instead of an even number4    
,second1 it is readily apparent that the
 greater the number of cylinders1       
provided the number is an odd one1 the  
more uniform the torque will be1 and it 
would seem at first that seven cylinders
 would therefore be better than five1   
since the uniform intervals between     
explosions with seven cylinders would be
 only #ajc degrees 7approximately74 ,the
 advantage gained1 however1 through     
seven cylinders instead of five is      
largely1 if not completely1             

counterbalanced by the added number of  
parts and the difficulty of providing   
sufficient circumferencial width for the
 connecting-rod shoes on the crank-pin  
bearing1 even with the improved         
construction of this bearing already    
described4 ,there is considerable       
fluctuation of the torque in each       
revolution of the engine with five      
cylinders1 but this fluctuation of      
torque is more easily smoothed out by   
the use of very light fly wheels than by
 increasing the number of cylinders1 and
 thus adding to the complication of the 
engine4  ,third1 the strongest point in 
favor of the radially arranged cylinders
 is the reduction in weight and         
complication which it permits4 ,the     
crank shaft is reduced to the very      
minimum1 there being only one crank pin 
with two main bearings which can1       
without any difficulty whatever1 be kept
 absolutely in line with each other and 
thus prevent binding and loss of power4 
,again1 the use of a single-throw crank 

not only reduces the cost and weight of 
the crank p#bdf itself1 but makes it    
very much less liable to damage2 long   
crank shafts with several crank pins    
being frequently twisted by improper    
explosions in the cylinders4 ,the       
supporting drum or crank chamber is     
likewise reduced to the very minimum1   
both in weight and simplicity1 the drums
 being perfectly symmetrical with no    
lost space either inside of them or on  
their exteriors4 ,the cam mechanism for 
operating the valves is reduced to a    
simple ring carrying 7for a             
five-cylinder engine7 a double-pointed  
cam and journaled on the exterior of the
 hub of one of the drums1 the cam being 
driven by a train of gears journaled on 
studs mounted on the drum1 and co-acting
 with a gear fastened to the crank shaft
 against the crank arm4  ,the radial    
arrangement of the cylinders is thus    
seen to give not only an engine with the
 smallest number of parts1 each of which
 is as far as possible worked to a      

uniform amount during each complete     
revolution of the crank shaft1 but it   
also gives a very compact and readily   
accessible mechanism with its center of 
gravity coincident with its center of   
figure1 and with the liability of damage
 to it1 in case of a smash of the       
vehicle on which it is used1 reduced to 
the minimum from the fact that the      
greatest weight is located at the       
strongest part4  ,fourth1 and of almost 
as great importance as the reduction in 
weight which the five-cylinder radial   
arrangement permits1 is its unusual     
qualities as regards vibration4 ,since  
these five-cylinder engines were built  
by the writer a very thorough treatment 
of their properties as regards balancing
 has been given in a treatise on the    
balancing of engines1#dd so no          
discussion of the mathematical formul   
involved in a study of the question of  
the inherent balancing properties of    
these engines will be here given4 ,it is
 sufficient to call attention to the    

fact that in an engine having five      
cylinders arranged radially1 all of the 
reciprocating parts are balanced for all
 forces of the first1 second and third  
orders4 ,as it is only the reciprocating
 parts which give any trouble in        
balancing any engine1 the unbalanced    
rotating parts being readily balanced by
 placing an equal weight at an equal    
distance from the center of rotation1   
and on the opposite side thereof1 it is 
readily seen that the properties of     
balancing which are inherent in this    
type of engine are unusual4 ,a          
six-cylinder engine having a six-throw  
crank shaft is not nearly so thoroughly 
balanced as this type having its five   
cylinders radially arranged1 for in the 
latter case all the moving parts are in 
one plane1 while in the former case the 
moving parts are in six separate and    
parallel planes1 and there is           
consequently considerable longitudinal  
vibration which can never be overcome4  
,while this is true as regards the      

vibration due to moving masses1 it is   
still more impressively true as regards 
vibration due to reaction arising from  
the force of the explosions in the      
engine cylinders1 especially when the   
engine is running slowly and having     
heavy explosions4  ,the usual practice  
in balancing the rotating parts of an   
engine is to attach p#bdg balance       
weights to the crank arms which are     
prolonged beyond the center of the crank
 shaft and on the opposite side from the
 crank pin2 the radius of rotation of   
these balance weights being made        
approximately equal to the radius of the
 crank pin4 ,but aside from the         
constructional difficulties which would 
be introduced1 it was seen that if this 
plan was followed in this engine it     
would require a very large additional   
weight4 ,since the amount of this weight
 could be diminished in exact proportion
 to the increase of the radius of       
rotation of the balance weights1 it was 
at first decided to attach the weights  

to the rims of the fly wheels1 the      
relative amount of weight attached to   
each wheel being inversely proportional 
to its actual longitudinal distance from
 the crank-pin center4 ,it was very soon
 found that the attachment of these     
balance weights to the fly wheel caused 
excessive strains on the rims of the    
wheels1 thereby causing them to go out  
of line4 ,in order1 therefore1 to keep  
the amount of balance weight small by   
carrying it at a considerable distance  
from the center of the shaft1 the       
weights were finally arranged as clearly
 shown in the drawings1 ,plates #gh to  
#hj4 ,there it is seen that the main    
portion of each of the balance weights  
consists of a flat arm bolted between   
the flanges which couple the            
transmission shafts to the engine       
shafts4 ,the flat arm terminates in a   
lozenge-shaped lug1 additional weight   
being provided by a plate fastened to   
one end of a tube1 the other end of     
which terminates in a collar fastened   

around the transmission shaft4 ,the tube
 is inclined at an angle of about thirty
 degrees with the flat balance arm1 thus
 acting as a brace to prevent the       
balance arm from wobbling1 the plate on 
the bracing tube being fastened to the  
lozenge-shaped lug by means of small    
bolts4  ,the tabulated statement of the 
weight of this large engine is given    
below4 ,from this it will be readily    
seen that the net weight of the engine  
proper is #abd4ag pounds4 ,the fly      
wheels were in no way necessary to the  
engine itself1 but were used solely for 
the purpose of smoothing out the torque 
of the engine so that the transmission  
shafts and propeller shafts might be    
kept down to the very minimum in weight4
 ,including the two fly wheels1 the     
weight is #adj pounds4  ,including the  
#bj pounds of cooling water the total   
weight of the power plant is #bjg4dg    
pounds4 ,without flywheels the total    
weight is #aia4fd pounds4  ,the         
construction of this large engine was   

completed in ,december1 #aija1 and the  
first tests of it were made in ,january1
 #aijb4 ,as already stated1 these first 
tests were made with the engine mounted 
on a special testing frame and          
delivering its power to two             
water-absorption dynamometers1 no fly   
wheels being used1 as none were         
required4 ,later1 when it became        
necessary either to use fly wheels or to
 greatly increase the weight of the     
transmission and propeller shafts1 in   
order to overcome the reverse torque1   
the two light fly wheels were added1 and
 another series of tests was made of the
 engine on its testing frame4 ,the      
arrangement of the engine1 dynamometers1
 and accessory p#bdh apparatus is       
clearly shown in ,plates #hb1 #hc and   
#hd4 ,the engine ran in a clockwise     
direction1 as viewed in ,plate #hb4 ,,aa
 are the fly wheels2 ,,bb the balance   
weights2 ,,cc the dynamometer shafts1 on
 which are fastened the rotor plates    
which revolve inside of the dynamometer 

drums1 ,,dd1 between stator plates      
fastened therein4 ,the drums have a hub 
on either side1 by which they are       
supported1 these hubs being journaled on
 ball-bearings in the pedestals resting 
on the wooden framework4 ,the rotor     
plates do not touch the stator plates in
 the dynamometers1 but drag on the water
 with which the drums are partially     
filled1 and thus tend to cause the drums
 to revolve around with them4 ,the      
torque on each drum is measured by means
 of a rope1 not shown1 fastened into the
 hook at the top of the drum1 the rope  
being given a partial coil around the   
drum and passing off tangent thereto at 
the horizontal diameter is fastened to a
 pair of spring scales hung from the    
ceiling vertically above the point of   
tangency4 ,the scales and ropes were    
unfortunately not in position when these
 photographs were taken1 but the        
arrangement of them should be readily   
understood4 ,as the friction of the     
rotor plates on the water heats it in   

exact proportion to the amount of power 
absorbed1 the small amount of water in  
the drums would be soon converted into  
steam unless continually renewed or     
cooled4 ,when the rotor plates are      
revolving the centrifugal force keeps   
the water pressed toward the            
circumference of the drum1 and the      
friction at any speed is dependent on   
the area of the rotor plates in contact 
with the water4 ,the horse-power        
required to revolve the plates at any   
definite speed can therefore be         
controlled by having an outlet for the  
water at the proper radial distance from
 the shaft4 ,the water from the water   
mains is led through the upper vertical 
pipe and allowed to flow into the       
funnel1 and thence into the drum near   
the center where the centrifugal force  
throws it to the circumference of the   
drum4 ,the lower vertical pipe is       
connected to the drum at a suitable     
radial distance from the center1 and the
 heated water thus passes through this  

pipe and into the lower funnel connected
 to the sewer4 ,by the use of the       
funnels the drums are allowed to rock   
sufficiently to exert their pull on the 
spring scales without being affected by 
the supply and exhaust of water4        
,illustration3 ,,pl4 #hb  ,,dynamometer 
,,tests ,,of ,,large ,,engine           
,illustration3 ,,pl4 #hc  ,,dynamometer 
,,tests ,,of ,,large ,,engine           
,illustration3 ,,pl4 #hd  ,,dynamometer 
,,tests ,,of ,,large ,,engine  ,the     
water for cooling the cylinders is led  
from the bottom of the tank ,e to the   
circulating pump ,f1 supported in a     
discarded lower pyramid of the aerodrome
 frame1 the pump being driven by the    
small vertical shaft1 as already        
described4 ,the water1 after passing    
through the pump and the engine         
cylinders1 is led back to the upper part
 of the tank4 ,by suitable connections  
to the water mains and sewer1 the water 
in the tank is kept at any desired      
temperature4 ,the gasoline supply tank  

is seen on the left-hand side of the    
testing frame1 as viewed in ,plate #hb1 
the carburetor being placed below it and
 the gas supply pipe from the carburetor
 passing through the gasoline tank4     
,instead of jacketing the carburetor1 a 
grid formed of thin copper tubes is     
supported just above the multitude of   
small air pipes leading into the        
carburetor1 and some of p#bdi the hot   
water from the engine is by-passed      
through this grid and thus warms the air
 as it passes into the carburetor4 ,the 
small pipe that by-passes this water    
through the grid is seen connected to   
the outlet water pipe just above the    
cylinders1 a small butterfly valve in   
the outlet pipe enabling the amount of  
heated water passing through the grid to
 be controlled4 ,the return from the    
grid is by means of the small pipe      
leading to the top of the large water   
tank4 ,the tachometer1 which gives      
instantaneous readings of the speed of  
the engine1 is seen at ,g1 where it is  

at all times in full view of the        
operator4  ,these dynamometers proved to
 be excellently suited for the testing  
work1 and far ahead of anything else the
 writer has ever found for engine       
testing4 ,since the power required to   
rotate the rotor plates1 with a uniform 
amount of water in the drums1 varies as 
the cube of the speed1 it is readily    
seen that it is impossible for the      
engine to race or injure itself by      
running away1 as frequently happens     
where there is no engine governor and   
,prony brakes are used to measure the   
power4  ,in the early tests the engine  
was never allowed to develop more than  
#dj horse-power1 as it was feared that  
by letting it develop more1 which it was
 clearly seen to be capable of1 it might
 be injured and cause a delay in the    
tests of the aerodrome4 ,in the second  
series of tests it was allowed to       
develop #ea horse-power at #ice ,r4 ,p4 
,m41 but it was not thought to be       
advisable to let it run at maximum power

 for more than an hour1 for the same    
reason as before4 ,in the summer of     
#aijd1 after it was seen that there was 
no immediate possibility of securing    
funds for continuing the tests of the   
aerodrome1 it was planned to enter the  
engine in the competitive tests at the  
,st4 ,louis ,exposition1 where a prize  
of #bejj was offered for the lightest   
engine for its power4 ,as the conditions
 specified in this competition required 
that the engine run at its maximum power
 for one hour1 and that this be followed
 by a durability test of ten hours'     
continuous running1 it was decided to   
make some durability tests of the engine
 before taking it to ,st4 ,louis4 ,in   
these tests1 the engine was run on three
 separate trials for a period of ten    
hours#de with a constant load of #eb4d  
horse-power at #iej ,r4 ,p4 ,m4 ,even in
 these long durability tests the engine 
and the dynamometers both worked so     
smoothly and evenly that the engine did 
not vary its speed more than ten        

revolutions per minute1 and the pull on 
the spring scales varied less than ten  
pounds in the entire ten hours4         
,considerable correspondence was had    
with the officials of the ,st4 ,louis   
,exposition regarding the entrance of   
the engine in the competition1 in order 
to make sure that suitable facilities   
for conducting the tests had been       
provided4 ,after receiving assurance    
that everything necessary had been      
provided1 the engine and its testing    
dynamometers were boxed for shipment to 
,st4 ,louis and arrangements were just  
being completed for their transportation
 when the following telegram was p#bej  
received from the director in charge of 
the aeronautical department of the      
,exposition3 8,on account of lack of    
competition engine tests abandoned40 ,as
 the main object of entering the engine 
in the competition was to insure for it 
an unquestioned record of its           
performance it was decided to reassemble
 it in the testing frame in ,washington 

and invite some engineers of prominence 
to witness and certify to its           
performance1 but on account of the lack 
of funds for meeting the expenses       
incident to such a series of tests as it
 was planned to make this was never     
done4  ,in the tests which were         
witnessed on ,april #bf1 #aijb1 by      
,captain ,i4 ,n4 ,lewis1 ,recorder of   
the ,board of ,ordnance and             
,fortification1 the engine was held down
 to a pull of #bjj pounds on a #ac-;inch
 lever1 when running at #ajjj           
revolutions per minute4 ,in the later   
tests in ,may1 #aijc1 which were        
witnessed by ,captain ,gibson1 who was  
then ,recorder of the ,board of         
,ordnance and ,fortification1 and ,mr4  
,g4 ,h4 ,powell1 the ,secretary of the  
,board1 the engine was allowed to work  
at a pull of #bfe pounds on the         
#ac-;inch lever arm at a speed of #iej  
revolutions per minute4 ,in the tests   
made in ,august1 #aijd1 the engine was  
run for ten consecutive hours#df at a   

pull which varied from #bfc to #bga     
pounds1 or an average of #bfg pounds1 on
 a #ac-;inch lever1 with the speed      
varying from #ide to #iee revolutions   
per minute1 thus showing #eb4d          
horse-power at the average speed of #iej
 ,r4 ,p4 ,m4   ,,detailed ,,weight ,,of 
,,new ,,large ,,engine4   ,name of      
,weight in  part4                       
grammes4   ,crank shaft                 
#e1bbe  ,connecting rods 7total7        
#e1jje  ,pistons--    ,no4 #a           
#a1feb    ,no4 #b                       
#a1fdg    ,no4 #c                       
#a1fee    ,no4 #d                       
#a1ffj    ,no4 #e                       
#a1fdf   ,cylinders--    ,no4 #a        
7including exhaust and inlet valves1 oil
      cups1 etc47                       
#d1gfh    ,no4 #b 7including exhaust and
 inlet valves1 oil      cups1 etc47     
#d1fhe    ,no4 #c 7including exhaust and
 inlet valves1 oil      cups1 etc47     
#d1fch    ,no4 #d 7including exhaust and
 inlet valves1 oil      cups1 etc47     

#d1fcg    ,no4 #e 7including exhaust and
 inlet valves1 oil      cups1 etc47     
#d1gif   ,port crank chamber drum1      
including cam1 cam    gears1 punch rods1
 etc4                           #e1bbe  
,starboard crank chamber drum           
#c1ddj  ,spark plugs 7#e7               
#dej  ,outlet water pipe                
#dej  ,inlet water pipe                 
#cfj  ,inlet gas manifold               
#a1gjj  ,primary and secondary sparkers 
and wires              #eab  ,balance   
arm with braces for same--starboard     
#a1jdj  ,balance arm with braces for    
same--port              #a1jfg          
------                  ,total          
#ef1cbc  #abd4ag lbs4  ,starboard fly   
wheel                                   
#c1idf  ,port fly wheel                 
#c1bcd                                  
------             ,total weight of     
engine and fly wheels   #fc1ejc  #adj4jj
 lbs4  ,spark coil and batteries        
#f1hjj  ,carburetor                     
#c1gea  ,inlet gas pipe from carburetor 

to manifold            #gef  ,gasoline  
tank                                    
#a1jjd  ,water tank                     
#gag  ,water circulating pump and shaft 
#hjg  ,radiator                         
#g1gjj                                  
------                  ,total weight of
 power plant        #he1jch  #ahg4dg    
lbs4   p#bea    ,,chapter ,,xi  ,,shop  
,,tests ,,of ,,the ,,aerodrome  ,in     
,june1 #aijb1 after the proper          
adjustments of the carburetor and other 
accessories of the engine had been      
accurately determined in the tests on   
the testing frame1 the engine was       
assembled in its proper position in the 
aerodrome frame and connected to the    
propellers4 ,the aerodrome frame was    
then mounted directly on the floor of   
the launching car1 which was placed on a
 short track laid on the floor of the   
shop1 as previously described4 ,a large 
spring balance1 which had been          
previously calibrated1 was then         
connected between the car and an upright

 fastened to the track1 and tests were  
made to determine the thrust developed  
when the engine drove the propellers at 
different speeds4 ,upon finding that    
there was comparatively little vibration
 when the engine was driving the        
propellers even at its maximum speed1 it
 was felt safe to raise the aerodrome   
from the floor of the car and place it  
upon the uprights on which it would be  
supported in launching it4 ,quite an    
extended series of tests was then made1 
and although the uprights raised the    
aerodrome frame until the midrod was    
practically #i feet from the floor of   
the car1 and in the tests at maximum    
power the propellers developed an       
average thrust of #dej pounds1 yet it   
was found that the clutch hook held the 
bearing points of the frame so securely 
on the uprights of the car that all fear
 that the aerodrome might break loose   
from the car during the launching       
process was removed4  ,upon the         
completion of these tests1 which had    

proved most satisfactory1 the aerodrome 
frame was supported from the ceiling of 
the shop by means of four short coil    
springs which reproduced as nearly as   
possible the elastic or flexible        
suspension which the aerodrome would    
have when supported by its wings in the 
air4 ,these springs were attached at the
 same points on the main frame of the   
aerodrome at which the wings would be   
attached1 thus permitting a careful     
study of the amount of flexure and      
vibration which it would undergo in     
actual flight4 ,the most remarkable     
difference in the nature of the         
vibration induced in the frame was found
 when the aerodrome was thus supported  
by springs4 ,when it was supported on   
the rather unyielding launching car1 the
 general tremor set up in the frame by  
the engine and propellers was1 while    
small1 yet harsh1 the effect on a person
 standing in the aviator's car being    
rather unpleasant in the joints of the  
knees when experienced for several      

minutes4 ,when the frame was suspended  
by the springs it was found that all    
this harshness of tremor disappeared1 it
 being replaced by a slight general and 
rapid tremor of the whole frame1 which  
was not at all unpleasant1 and which    
p#beb had no tiring effect on one       
standing in the aviator's car4 ,in fact1
 the vibration in the first case        
resembled rather closely that of a motor
 vehicle supported on wheels having     
metal tires1 and in the second case a   
motor vehicle supported on wheels having
 pneumatic tires4  ,as in these tests in
 the shop it was impossible to keep the 
engine cool by circulating its cooling  
water through the radiator1 since there 
was no air current blowing across the   
latter to carry away the heat1 it was   
necessary to connect an extra water tank
 in the cooling-water circuit4 ,a tank  
holding about ten gallons was used1 and 
this sufficed for about ten minutes     
before the water was raised to the      
boiling point4  ,during one of these    

tests when the frame was supported from 
the springs1 and while the engine was   
developing about fifty horse-power1     
without any warning whatever1 both      
propellers suddenly twisted off from the
 flanges by which they were connected to
 the propeller shafts1 thus leaving the 
engine entirely unloaded4 ,the          
propellers both dropped quietly to the  
floor1 making only about one or two     
turns in falling the distance of        
approximately #aj feet1 and the engine1 
which had been running at about #hej ,r4
 ,p4 ,m41 immediately speeded up to an  
exceedingly high speed1 which1 while not
 exactly known1 since the tachometer    
only read to #bjjj ,r4 ,p4 ,m41 yet from
 the deflection produced on the         
tachometer needle must have been        
considerably higher than this4 ,although
 the fly wheels1 which were #cc inches  
in diameter1 with the aluminum rims and 
wire spokes1 had been exceedingly well  
made1 yet it was not considered safe to 
run them at this speed1 and the engine  

was immediately shut down4 ,at the      
moment1 however1 that the engine had    
broken loose from its propellers and    
also momentarily jumped to this         
exceedingly high speed there was        
absolutely no vibration that could be   
noticed1 the unloaded engine running as 
smoothly as an electric motor4 ,this    
showed very clearly that the running    
balance of the engine was as near       
perfect as it would be possible to get  
it1 except with a seven-cylinder engine1
 which is theoretically capable of more 
perfect balance4 ,it was evident that   
what small vibration there was in the   
frame while the engine was developing   
its power was due almost entirely to the
 reverse torque1 and1 of course1 could  
never be entirely eliminated4  ,in the  
tests of the engine working in the      
frame1 both while mounted on the car and
 also when suspended from the springs1 a
 great amount of delay was caused from  
the fact that the ball-bearings on the  
transmission and propeller shafts       

frequently went to pieces4 ,there were  
two reasons for this3 ,in the first     
place1 although carefully selected balls
 were used1 defective ones were         
continually encountered4 ,even a slight 
defect in a single ball resulted in its 
breaking under the rather severe test to
 which they were subjected1 and1 as is  
well known1 the breaking of one ball in 
a ball-bearing usually results in the   
destruction of the whole bearing1       
especially if the races are light4 ,the 
second cause was that p#bec the whole   
aerodrome had been originally designed  
with the expectation of using a maximum 
of #bd horse-power1 and as no margin had
 been left to provide for possible      
increases in the size of the bearings1  
there was no room to permit them to be  
increased without almost completely     
reconstructing portions of the          
transverse frame4 ,while in the end it  
would have been cheaper to have         
reconstructed these portions in order to
 put in larger bearings1 yet1 as is     

always the case in experimental work of 
this kind1 small changes which seem to  
hold out hope of overcoming difficulties
 are usually followed1 rather than      
reconstructions which can be seen to    
involve considerable expense and delay4 
,after a number of minor changes had    
been made in the bearings1 they were    
finally able to stand up fairly well    
under the severe strain to which they   
were subjected when the engine developed
 its full power1 and no further changes 
were made in them2 a defective race     
being1 however1 replaced by a new one as
 occasion demanded4  ,these tests       
demonstrated very clearly that at speeds
 of approximately #ajjj revolutions per 
minute ball-bearings which are subjected
 to considerable loads should be        
calculated with a considerable margin of
 safety1 as the yielding of the frame1  
which must necessarily be far from      
rigid1 causes more or less error in the 
alignment of the shafts and bearings1   
and this introduces considerably        

increased strains on the bearings4 ,in  
the early tests before the bearings were
 strengthened1 the balls in some of the 
races were on a few occasions ground to 
a very fine powder before it was        
discovered that they had failed4 ,such a
 result1 it will be understood1 could   
and did occur in the course of a very   
minute length of time4  ,in imitating as
 nearly as possible the conditions to   
which the carburetor of the engine would
 be subjected during the period of      
launching1 numerous tests were made in  
which the engine was brought to its     
maximum speed and1 without changing the 
adjustment of the mixture-controlling   
devices of the carburetor1 sudden blasts
 of air were turned on it from various  
directions1 and these were continued    
until the mixture-control devices were  
perfected to such a point that gusts of 
thirty miles an hour suddenly directed  
from any point against any portion of   
the apparatus would in no way effect the
 speed and power of the engine4 ,these  

tests were considered necessary in view 
of the very sudden changes in conditions
 to which the aerodrome would be        
subjected during its brief run down the 
launching track1 the conditions changing
 in approximately three seconds from    
absolute quiescence of the aerodrome to 
a plunge through space at thirty-five   
feet per second4 ,an aviator would be   
more than occupied with maintaining     
control of himself and of the aerodrome1
 which at the moment of leaving the     
track might require considerable change 
in the adjustment of the ,pnaud tail1   
and he would1 therefore1 not be able to 
make any adjustments of the             
engine-control devices4 ,this           
supposition was entirely confirmed in   
the actual tests of the aerodrome which 
are to be later described1 the rush down
 the track being p#bed so very brief    
that the engine could not have been     
given any attention by the aviator had  
it needed it1 which fortunately it did  
not4  ,it is hardly necessary to recount

 at any length the great difficulties   
which was experienced in these tests of 
the engine in the aerodrome frame before
 the shafts1 bearings1 propellers1 and1 
in fact1 the frame itself were all      
properly co-ordinated so that confidence
 could be felt that all of the parts    
would stand the strains which were      
likely to come on them when the         
aerodrome was in flight4 ,these tests   
were really not tests of the engine     
itself1 but of the frame1 shafts1 and   
bearings4 ,suffice it to say that nearly
 a year was consumed by the various     
breakages of the shafts1 bearings1 and  
propellers before it was felt that all  
of these parts could be depended on1 and
 even then the weakness of the bearings 
above referred to was fully recognized4 
,had some of the better-grade balls and 
steels for the bearings1 which have     
since that time come on the market1 been
 obtainable then1 there would have been 
no difficulty with these bearings4      
,however1 this same remark might be made

 with reference to nearly all of the    
details of the aerodrome1 for it was the
 accessories1 such as bearings for the  
transmission and propeller shafts1 spark
 plugs1 coils1 batteries1 and a suitable
 carburetor for the engine1 that caused 
the chief delay after the main          
difficulty of getting a suitable engine 
had been overcome4   p#bee    ,,chapter 
,,xii  ,,field-,,trials ,,in #aijc  ,the
 extended series of shop tests which had
 occupied a considerable portion of the 
late winter and early spring of #aijc   
had demonstrated the following facts3   
,first1 with the aerodrome mounted on   
the launching car1 a propeller thrust of
 from #dej to #dge pounds could be      
maintained indefinitely by the engine1  
and even when the engine was delivering 
its full power to the propellers1 the   
vibration was so small as to cause no   
apprehension that the wings and rudder  
would be made to vibrate sufficiently to
 produce undue strains in them4 ,second1
 with the aerodrome suspended from the  

ceiling by springs at the points at     
which the wings would be attached1 the  
vibration produced by the engine        
developing it's full power was even less
 than when the machine was mounted on   
the launching car and there was1        
consequently1 even less cause for       
concern that the wings and rudder might 
be set in vibration when the machine was
 free in the air4 ,third1 the engine    
could be depended upon to deliver       
something over #eb horse-power when the 
five cylinders were working properly1   
and even with one cylinder not working1 
but acting as a dead load against the   
others1 approximately #ce horse-power   
could be developed1 while with two      
cylinders not working at all1 the three 
which were working would deliver about  
#be horse-power4 ,therefore1 even       
assuming that two of the five cylinders 
might become deranged during a flight1  
there should still be sufficient power  
to propel the machine4 ,these tests1    
some of which had been witnessed by     

members of the ,board of ,ordnance and  
,fortification1 clearly demonstrated    
that the time had arrived when it was   
safe to give the aerodrome a test in    
free flight4 ,the machine itself        
together with all its appurtenances and 
much extra material for repairs in case 
of breakages1 which previous experience 
had shown to be almost certain1 was     
accordingly taken from the shop and     
placed on the house-boat preparatory to 
taking it down the river to the point   
opposite ,widewater1 ,va41 which had    
already been selected as the            
8experimental ground40  ,owing to the   
limited size of the shops it had been   
impossible to place the wings and rudder
 in their proper positions on the       
aerodrome and determine its balancing in
 a way similar to that practiced with   
the models4 ,the approximate settings   
for the wings and rudder had1 however1  
been determined by calculation from the 
data obtained in the test of the        
quarter-size model1 so that it remained 

only to place the wings and a weight to 
represent the rudder actually on the    
machine in the large space of the       
house-boat 7which1 however1 was not     
large enough to permit the rudder to be 
assembled along with the wings71 and    
thus check the balancing previously     
determined by calculation4 ,there were  
very p#bef few appurtenances which could
 be shifted in balancing the aerodrome1 
but the proper disposition of weight had
 been so accurately determined by       
calculation that the floats1 which1 as  
will be seen from the various           
photographs1 were merely cylindrical    
tanks with pointed ends1 and of a       
sufficient capacity to cause a          
displacement great enough to float the  
aerodrome when it came down into the    
water1 proved sufficient ballast for    
shifting the center of gravity to its   
proper point4 ,the flying weight of the 
aerodrome was #hcj pounds1#dg including 
the weight of the writer1 which was #abe
 pounds4 ,the total area of the wings or

 supporting surfaces was #ajdj square   
feet1 or the ratio of supporting surface
 to weight was #a4be square feet per    
pound1 which is the same as 4#h pound   
per square foot4  ,after the balancing  
of the large aerodrome had been         
completed on the house-boat1 and        
everything else got in readiness as far 
as could be done before actually        
arriving at the point at which the test 
was to be made1 the house-boat was towed
 down the river on ,july #ad1 #aijc1 and
 fastened to its mooring buoy1 which had
 been placed in the middle of the river 
at a point practically opposite         
,widewater1 ,va41 and approximately     
forty miles from ,washington4 ,see      
,coast-,survey ,chart1 ,plate #he4      
,sleeping quarters for the force of     
eight workmen and the regular soldier   
from the ,united ,states ,army1 who had 
been detailed as a special guard1 had   
been provided on the boat1 but owing to 
the lack of space it had been found     
impracticable to arrange proper cooking 

facilities on the boat1 and it had been 
found necessary to arrange to transport 
the workmen to ,chopawamsic ,island1    
near ,quantico1 ,va41 for their meals4  
,it had been planned to use the         
twenty-five-foot power launch for this  
purpose1 but owing to the heavy storms  
which became quite frequent soon after  
the house-boat was taken down the river1
 it was found that the small launch was 
not sufficient1 and it was necessary to 
employ a tug-boat and keep it stationed 
there at all times4 ,this added very    
considerably to the expense of the      
experiments1 as the hire of this one    
tug-boat very nearly equalled the       
pay-roll of the workmen1 and while it   
was not expected that the stay down the 
river would be so greatly prolonged as  
afterwards proved the case it was felt  
certain that minor delays were sure to  
occur and the experiments would at the  
very least require several weeks4       
,illustration3 ,,pl4 #he  ,,location    
,,of ,,house ,,boat ,,in ,,center ,,of  

,,potomac ,,river1 ,,july #ad1 #aijc    
,,from ,,sheet ,,no4 #c1 ,u4 ,s4 ,,coast
 ,,and ,,geodetic ,,survey ,,chart ,,of 
,,potomac ,,river1 ,,issue ,,of #ahhb   
,,scale #a #a-af ,,inch ,,to ,,statute  
,,mile  ,had it been possible to foresee
 the great delay which finally occurred 
before the large aerodrome was actually 
launched1 and the great expense arising 
from the necessity of maintaining one or
 more expensive tug-boats constantly1 it
 is very certain that an experimental   
station nearer ,washington would have   
been selected1 even though the nearer   
places on the river which were available
 were much less suitable1 both on       
account of the river being much narrower
 and the traffic very much heavier4 ,in 
fact1 at the time that the house-boat   
was taken down the river on ,july #ad1  
with the expectation that the           
experiments with the p#beg large        
aerodrome would certainly be concluded  
within four weeks1 the expenses of the  
work1 which had been met from the       

,hodgkins ,fund of the ,smithsonian     
,institution since the original         
allotment from the ,board of ,ordnance  
and ,fortification was exhausted more   
than a year previously1 had already made
 such heavy drafts on this fund that    
,mr4 ,langley was most reluctant to draw
 further on it1 even to the extent which
 seemed necessary to meet the expenses  
of a month of 8field-work40  ,before    
making the tests of the large aerodrome1
 it was intended to give the            
quarter-size model a preliminary trial  
to test the balancing which it was      
proposed to use on the large machine4   
,for this test it was planned to employ 
the small launching apparatus mounted on
 top of the small house-boat1 which had 
been used in the experiments with the   
steam-driven models ,nos4 #e and #f in  
#ahii1 and later with the quarter-size  
model in #aija4 ,however1 after arriving
 down the river1 it was found that the  
small house-boat which had been anchored
 at ,chopawamsic ,island since the      

experiments in #aija had deteriorated to
 such an extent that it was unsafe to   
take it out into the river4 ,the        
launching apparatus for the model was1  
therefore1 removed from it and placed on
 the turn-table of the large house-boat1
 alongside the launching track for the  
large machine4 ,after completing this   
transfer of the model-launching         
apparatus everything was thought to be  
in readiness for a test of the          
quarter-size model1 but upon making a   
shop test of the model to make sure that
 its engine was working properly1 it was
 found impossible to get it to work at  
all4 ,a few explosions could be obtained
 once in a while1 but very irregularly4 
,after spending considerable time in    
trying to locate the difficulty1 it was 
found that the commutator which         
distributes the high-tension sparking   
current to the proper cylinder at the   
proper time was short-circuited4 ,this  
commutator had been made of 8insulating 
fibre0 and had never caused any previous

 trouble4 ,it was now found1 however1   
that the very damp atmosphere which had 
been experienced during the preceding   
two weeks1 when the fog for a large     
portion of the time was so heavy that   
objects at a short distance across the  
water could not be seen1 had caused the 
moisture to penetrate the fibre and thus
 destroy its insulating qualities4      
,after much trouble some vulcanite and  
mica were secured and a new commutator  
made to replace the fibre one1 and1     
then1 after some minor difficulties had 
been remedied1 the engine for the model 
was got into good condition again4      
,after getting satisfactory shop tests  
on the model aerodrome1 and having      
everything in readiness for a flight1 it
 was necessary to wait many days before 
the weather was calm enough for a test4 
,however1 on ,august #h the weather     
quieted down and the model was launched 
at #i4cj a4 m4 into a wind blowing about
 #ab miles per hour from ,e4 ,,se4      
,referring to ,plate #hf1 which shows   

the quarter-size model mounted on its   
launching car on top of the large       
house-boat1 and which was taken only a  
few p#beh minutes before the model was  
actually launched1 it will be noted that
 a board 7,a7 projects from the front of
 the launching car4 ,this board1 which  
is mounted in a false floor of the      
launching car1 is so arranged that when 
it strikes the two blocks 7,b7 at the   
end of the track it is driven backward  
in the car against the triggers which   
prevent the uprights 7,d71 supporting   
the aerodrome1 from being folded down   
against the floor4 ,when this board     
strikes the triggers it releases them   
and the springs 7,c71 which in this case
 were rubber bands1 immediately fold the
 vertical posts or uprights 7,d7 against
 the brace posts 7,e71 which are        
immediately folded down flat against the
 floor of the car through the action of 
the spring hinges1 by which they are    
connected to it4 ,these uprights 7,d71  
which support the aerodrome at the front

 and rear1 respectively1 are not        
released until a fraction of a second   
after the release of the clutch hook    
7,f71 which is attached to the middle   
upright 7,g71 and which1 grasping the   
lower pyramid1 holds the machine down   
firmly against the uprights 7,d7        
previously referred to4 ,in order to    
prevent the possibility of the aerodrome
 being released prematurely while the   
car is held at the extreme rear end of  
the track by the hook 7,h71 a steel pin 
7,j71 which can just be seen in the     
photograph1 is pushed through a hole in 
the board 7,a71 and into a hole in a    
cross-member on the bottom of the car1  
thus holding the board in its proper    
position4 ,after the engine is started  
up one of the mechanics who has assisted
 in starting it is under orders to      
remove the pin at the word 8,ready10 and
 at the word 8,go0 the other mechanic   
who has assisted in starting the engine 
is under orders to release the hook     
7,h71 and thus allow the car to dash    

down the track4 ,in the experiment on   
,august #h the mechanic failed to remove
 the pin 7,j7 at the proper time1 and it
 was only after the machine had been    
released and started down the track that
 it was seen that the pin had not been  
removed4 ,it was then1 however1 too late
 to stop it1 so the car dashed down the 
track4 ,although the striking of the    
board against the blocks caused the pin 
to split the board to pieces1 the       
launching apparatus worked perfectly and
 the aerodrome started off on a         
perfectly even keel1 the propellers     
revolving at an exceedingly high rate of
 speed4 ,the aerodrome flew straight    
ahead for a distance of #cej feet1 when 
it began to circle towards the right1   
descending slightly as it circled4 ,upon
 completing a quarter circle it again   
began to rise1 flying straight ahead    
until it had gone a similar distance1   
when it again lost headway1 but before  
it reached the water the engine         
increased its speed and the aerodrome   

again rose4 ,when the engine slowed down
 for the third time1 however1 the       
aerodrome was not many feet above the   
river1 so that before the engine        
regained its normal speed the aerodrome 
touched the water with its propellers   
still revolving1 but very slowly4 ,while
 the total distance covered was only    
about #ajjj feet1 and the time that it  
was actually in the air #bg seconds1 yet
 in this brief time it had served the   
main purpose for which it had been      
built1 which was to find out if the     
balancing of p#bei the large aerodrome1 
which had been determined by calculation
 from the results obtained with the     
steam-driven models1 was correct4 ,for  
it was assumed that if the quarter-size 
model1 which was an exact counterpart of
 the large machine1 should fly          
successfully with the same balancing as 
that calculated for the large one1 the  
large one could reasonably be expected  
to act similarly4 ,it was at first      
thought best to make another test with  

the model immediately after recovering  
it from the water1 but by the time it   
could be brought into the house-boat and
 the water which had got into the engine
 cylinders could be removed and the     
engine made to work properly quite a    
strong wind had sprung up and rendered  
further tests of the model on this day  
impossible4 ,if the launching track for 
the small machine could have remained on
 the top of the boat without interfering
 with the completion of the preparations
 for testing the large machine1 it would
 have been left there and other tests   
made with the model when the weather was
 suitable1 but as this could not be done
 without interfering with the work on   
the large machine1 and the delays with  
the model had already been so great1 the
 small track was immediately removed and
 the model stored away in the house-boat
 for possible later tests4  ,at the     
first it was impossible to account for  
the engine on the model running so      
irregularly and slowing down so soon    

after it was launched1 as it was felt   
very certain that the cylinders could   
not in so short a time1 and with the    
aerodrome actually moving through the   
air1 have heated up sufficiently to     
cause it4 ,after a while1 however1 one  
of the workmen volunteered the          
information that in his zeal to fill the
 fuel tank completely so as to insure a 
long flight1 he had caused the tank to  
overflow so that some of the gasoline   
had run into the intake pipe1 and that  
he had noticed gasoline dripping from   
the intake pipe as the machine went down
 the track4 ,this excess gasoline in the
 intake pipe had caused the mixing valve
 which controls the quality of the      
explosive mixture to be improperly set1 
so that it would not furnish the proper 
mixture when the fuel was supplied in   
the proper way by the carburetor1 and   
consequently when this excess gasoline  
had evaporated1 the mixture furnished to
 the engine was not proper1 and it      
consequently slowed down1 there being no

 human intelligence on board to correct 
the adjustment of the mixing valve4  ,a 
series of seven photographs of this     
flight of the quarter-size model is     
given in ,plates #hg to #ic4 ,plate #hg1
 taken with a kodak from the tug-boat   
stationed several hundred yards directly
 ahead of the house-boat1 shows the     
machine in full flight heading directly 
for the tug-boat4 ,although the         
aerodrome was about fifteen or twenty   
feet higher above the level of the water
 than the camera1 still1 at the         
considerable distance from which the    
photograph was taken1 this view would   
not show so much of the under side      
unless the machine had been pointing    
upward4 ,the photograph also proves very
 clearly that at the time it was taken  
the machine had certainly not dropped at
 all below the level p#bfj at which was 
launched4 ,in ,plate #hh the camera was 
unfortunately not well aimed1 and only  
the front guy-post1 bearing points1     
float and bowsprit are visible1 besides 

the blur of the propellers1 which1 it   
will be noted1 were moving very rapidly4
 ,the camera with which this and the    
succeeding plates were taken was one of 
the two special telephoto cameras       
belonging to the ,zoological ,park1 but 
built in the course of the aerodromic   
work and used where especially rapid    
shutters were needed4 ,as the shutters  
on these cameras give an exposure of    
only #a_/ejj of a second1 and           
consequently are sufficiently rapid to  
show the individual feathers in a       
rapidly moving bird's wing1 any         
distortion of the machine in flight     
would certainly have been shown1 but1 as
 will be seen from the later            
photographs1 no distortion of any kind  
occurred1 both the surfaces and the     
framework remaining in a perfectly      
straight condition4 ,near the bottom of 
,plate #hh is the tug from which ,plate 
#hg was taken1 and a careful inspection 
of ,plate #hg shows two persons standing
 on the roof of the house-boat1 below   

the upper works1 the gentleman on the   
left being ,mr4 ,thomas ,w4 ,smillie1   
the official photographer of the        
,smithsonian ,institution1 who took all 
of the photographs except ,plate #hg1   
and1 as stated above1 used therefor the 
special telephoto cameras with the rapid
 shutters4 ,plate #hi is an exceedingly 
good view1 and shows the propellers     
revolving very rapidly while ,plates    
#ij1 #ia and #ib show very clearly that 
the speed of the propellers had greatly 
decreased between the successive        
photographs4 ,plate #ic shows the       
aerodrome shortly after it touched the  
water and had been almost completely    
submerged1 in spite of its floats1 by   
the very strong tide which was running4 
,though these plates show all that      
photographs can1 they give no adequate  
idea of the wonder and beauty of the    
machine when actually in flight4 ,for   
while the graceful lines of the machine 
make it very attractive to the eye even 
when stationary1 yet when it is actually

 in flight it seems veritably endowed   
with life and intelligence1 and the     
spectacle holds the observer awed and   
breathless until the flight is ended4   
,it seems hardly probable that anyone1  
no matter how skeptical beforehand1     
could witness a flight of one of the    
models and note the almost bird-like    
intelligence with which the automatic   
adjustments respond to varying          
conditions of the air without feeling   
that1 in order to traverse at will the  
great aerial highway man no longer needs
 to wrest from nature some strange1     
mysterious secret1 but only1 by diligent
 practice with machines of this very    
type1 to acquire an expertness in the   
management of the aerodrome not         
different in kind from that acquired by 
every expert bicyclist in the control of
 his bicycle4  ,illustration3 ,,pl4 #hf 
,,quarter-,,size ,,model ,,aerodrome    
,,mounted ,,on ,,launching-,,car        
,illustration3 ,,pl4 #hg                
,,quarter-,,size ,,model ,,aerodrome    

,,in ,,flight1 ,,august #h1 #aijc       
,illustration3 ,,pl4 #hh                
,,quarter-,,size ,,model ,,aerodrome    
,,in ,,flight1 ,,august #h1 #aijc       
,illustration3 ,,pl4 #hi                
,,quarter-,,size ,,model ,,aerodrome    
,,in ,,flight1 ,,august #h1 #aijc       
,illustration3 ,,pl4 #ij                
,,quarter-,,size ,,model ,,aerodrome    
,,in ,,flight1 ,,august #h1 #aijc       
,illustration3 ,,pl4 #ia                
,,quarter-,,size ,,model ,,aerodrome    
,,in ,,flight1 ,,august #h1 #aijc       
,illustration3 ,,pl4 #ib                
,,quarter-,,size ,,model ,,aerodrome    
,,in ,,flight1 ,,august #h1 #aijc       
,illustration3 ,,pl4 #ic                
,,quarter-,,size ,,model ,,aerodrome    
,,at ,,end ,,of ,,flight1 ,,august #h1  
#aijc  ,in describing this flight       
immediately after it was made1          
,professor ,john ,m4 ,manly1 who took   
the photograph shown in ,plate #hg1     
said3 8,the flight of the small         
aerodrome was an event which all who saw

 it will remember for the rest of their 
lives4 ,we were1 of course1 in a state  
of considerable nervous excitement and  
tension1 for1 after weeks of delay from 
high winds1 rains1 and p#bfa other      
uncontrollable causes1 at last we had a 
day ideally suited to the test4 ,this   
was1 to be sure1 not the great test1 the
 final test1 the test of the            
man-carrying flyer1 but it was felt by  
all to be of almost equal importance1   
for if the balancing of the small       
aerodrome was correct1 the large one    
would maintain its equilibrium1 and the 
problem of human flight would be solved 
practically as well as theoretically4   
,that the weather was now favorable for 
the test filled us with excitement4     
,again and again the favorable moment   
had seemed to come1 and had gone again  
before we could make ready for it4 ,the 
aerodrome was rapidly carried to the    
upper works of the house-boat and the   
observers and helpers went hastily to   
their positions4 ,the large tug-boat was

 stationed directly ahead1 almost in the
 line of flight1 and about a mile from  
the house-boat4 ,signals of readiness   
were exchanged1 and with every sense    
astrain we awaited the supreme moment4  
,the rocket gave the starting signal1   
and instantly there rushed towards us1  
moving smoothly1 without a quiver of its
 wings1 with no visible means of motion 
and no apparent effort1 but with        
tremendous speed1 the strange new       
inhabitant of the air4 ,onward it moved1
 looking like a huge white moth1 but    
seeming no creature of this world1 not  
only on account of its size1 its ease of
 movement and its wonderful speed1 but  
also because of its strange1 uncanny    
beauty4 ,it seemed visibly and          
gloriously alive as it advanced1 growing
 rapidly larger and more impressive4    
,straight at us it came1 and for a      
moment there was a wild fear that it    
would come right on and crush itself    
against the ponderous tug-boat4 ,there  
was a half impulse to move the tug-boat 

out of its way1 but the aerodrome seemed
 to realize its danger and rapidly1     
though not abruptly or violently1 as if 
it had intelligence and power of        
self-direction1 it checked its speed and
 circled to the right1 descending       
slightly4 ,soon it quickened its speed  
again and went straight ahead for about 
ten seconds1 when it again checked its  
flight and descended1 circling once     
more4 ,once again it attempted to       
increase its speed and rise1 but it was 
too near the water1 and in a few moments
 the waves had wet its propellers and   
wings1 and it sank1 a poor1 bedraggled  
creature4 ,but the vision of its beauty 
and power and seeming intelligence and  
life will long remain with those who saw
 its flight40  ,after removing the      
model-launching track so that the final 
arrangements could be completed for     
testing the large machine1 many weeks of
 delay were experienced1 almost entirely
 due to the unusually bad weather       
conditions which prevailed1 and which   

were unprecedented for the time of the  
year4 ,however1 on ,september #c the    
weather became more suitable1 and the   
aerodrome being in readiness the metal  
frame of the large machine was hoisted  
to the top of the boat and placed on the
 launching car1 and the wings1 rudder1  
etc41 were then hoisted up and properly 
assembled and everything made ready for 
a flight4 ,the parties with the         
telephoto cameras were sent to their    
stations on the shore1 where definite   
base lines had been marked out so that  
with the data as to p#bfb altitude and  
azimuth1 which these cameras            
automatically recorded1 the speed1      
height1 etc41 of the machine in flight  
could be accurately computed4 ,after    
stationing the tug-boats at proper      
points1 so as to render assistance      
should the aerodrome come down into the 
water at a considerable distance from   
the house-boat1 it was found1 upon      
attempting to start the engine1 that for
 some reason it would not operate4 ,the 

sparking battery which had been placed  
at the extreme rear of the aerodrome was
 found to be giving such a weak spark   
that it would not ignite the mixture in 
the cylinders4 ,upon removing the       
connection which grounded the terminal  
of the battery to the framework and     
replacing it by a large copper wire     
leading up to the engine so as to       
decrease the resistance of the circuit  
it was found that the battery still     
would not give sufficient spark4 ,a     
large quantity of dry cells1 such as    
were used for the engine1 had been      
procured to insure against delay from   
lack of batteries1 but upon attempting  
to get a new set from this reserve      
supply it was found that they1 as well  
as the set that was on the machine1 had 
so deteriorated that instead of giving  
eighteen amperes on short circuit they  
would give only three1 which was not a  
sufficient current to enable the engine 
to operate4 ,no shop tests on the large 
engine had been made since the large    

aerodrome had been brought down the     
river1 as no provision had been made for
 properly supporting the aerodrome in   
the house-boat in such a way as to      
permit the large propellers to whirl    
around without causing damage1 and1     
therefore1 the batteries which had      
hitherto proved to be suitable had not  
had any special test since they had been
 brought down the river4 ,as no         
batteries suitable for use were on hand1
 and as none could be procured from a   
point nearer than ,washington1 the test 
had to be abandoned for the day and the 
aerodrome removed to the interior of the
 boat4  ,it was at first impossible to  
account for the rapid deterioration of  
so large a number of dry cells1 but it  
was later found that the damp1          
penetrating fogs which had been         
experienced for nearly two months were  
responsible for it1 and that in order to
 preserve the batteries in such a       
climate it was necessary to place them  
in metallic boxes which could be nearly1

 if not quite1 hermetically sealed4 ,new
 batteries were immediately procured    
from ,washington1 and before again      
mounting the aerodrome on the launching 
track provision was made for testing the
 engine inside the house-boat4          
,illustration3 ,,pl4 #id  ,,hoisting    
,,wing ,,of ,,full-,,size ,,aerodrome   
,up to this time the wings had been     
stored inside the house-boat by         
suspending them from the ceiling1 but   
the time required to hoist them to the  
upper works on top of the boat1 after   
the main body of the aerodrome had been 
placed on the launching car preparatory 
to making a flight1 had added so greatly
 to the delay1 and consequently to the  
difficulty of getting the machine       
entirely ready for a flight while the   
weather conditions remained suitable for
 a test1 that it was decided to build   
some framework on the upper works and   
cover it with canvas so as to provide   
some boxes in which the wings could be  
p#bfc stored whenever it seemed probable

 that a flight would soon be possible4  
,some of the difficulties experienced in
 hoisting these wings from the interior 
of the boat to the upper works may be   
appreciated by an inspection of ,plate  
#id1 where one of them is seen just     
ready to be hoisted from the raft4 ,only
 one wing at a time could be handled on 
the raft1 even when there was no        
appreciable wind or roughness of the    
water1 so that in order to hoist all    
four wings the raft had to be hauled    
around from the door at the end of the  
boat to the side where the wing was     
hoisted1 and back again four times every
 time the machine was assembled         
preparatory to a flight4 ,the necessity 
for making occasional tests of the      
engine in order to make sure that no    
trouble would be again experienced in   
having proper batteries1 etc41 for the  
engine when the machine was again on the
 point of being launched also made it   
imperative to remove the wings from the 
interior of the house-boat1 as the      

tremendous blasts of air from the       
propellers would certainly have wrecked 
the wings had they remained in the boat 
while the engine was being tested4      
,after the wings had been stored in the 
8wing boxes10 thorough tests of the     
engine were made1 and before there came 
another day which was at all suitable   
for a trial1 it was accidentally        
discovered that the glued joints in the 
cross-ribs of the large wings had been  
softened by the moisture of the fogs    
which had penetrated everything1 and    
that the joints had all opened up and   
left the ribs in a practically useless  
condition4  ,it will be recalled from   
the description of these cross-ribs1    
,chapter ,,vi1 that the rib is composed 
of two channel-shaped strips1 the edges 
of which are glued together while the   
strips are bent over a form which causes
 the ribs to maintain the curved form   
desired after the glue has hardened4    
,recalling these facts1 it will be      
readily understood that there is at all 

times a considerable strain on the glued
 joints due to the two strips of wood   
trying to straighten out1 and1          
therefore1 if the glue should at any    
time become softened sufficiently to    
allow one strip to slide along on the   
other1 the joint would open up and the  
rib would consequently become straight4 
,when the construction of the hollow    
ribs was first contemplated it was      
realized that although the hollow       
construction would enable the ribs to be
 strong1 and at the same time           
exceedingly light1 yet it would make it 
imperative that the ribs be covered with
 a water-proof varnish in order to      
prevent the glue from being softened    
when the aerodrome came down into the   
water1 as it was expected from the first
 that it would do at the end of its     
flight4 ,considerable time and attention
 had1 therefore1 been given to this very
 problem of securing a suitable         
water-proof varnish1 and ribs coated    
with the varnish which was finally used 

had been submerged in water for more    
than #bd hours in testing this very     
point1 and no softening of the glue     
could be detected after this long       
submergence4 ,it had1 therefore1 been   
felt that the ribs had been given a test
 which was much more severe than any    
conditions which p#bfd were likely to be
 met with1 since the aerodrome would1 in
 no case which could be anticipated1 be 
in the water for so long a period as #bd
 hours1 and no trouble from this source 
need be anticipated4  ,in the present   
case1 however1 the moisture of the      
atmosphere1 which had been heavily laden
 with fog for several weeks1 had        
penetrated the varnish and softened the 
glue1 even though the submergence of #bd
 hours in water had shown no effect4 ,to
 construct new ribs for the wings would 
have required several weeks1 and the    
delays which had already been           
experienced had by this time prolonged  
the stay down the river so greatly that 
even under the very best conditions it  

seemed hardly possible to complete the  
tests before the coming of the          
equinoxial storms1 which would make it  
necessary to remove the boat from the   
middle of the river and place it in a   
safe harbor4 ,something1 therefore1 had 
to be done1 and that very quickly1 so   
that an immediate test could be made1 or
 else the tests would have to be delayed
 until the following season1 or possibly
 postponed indefinitely on account of   
the lack of funds4  ,owing to the       
varnish with which the ribs were        
covered1 it was impossible in repairing 
them to carry out the first plan which  
suggested itself of binding the ribs    
with a strip of cloth impregnated with  
glue and wound spirally from end to end4
 ,as the wood was so very thin1 it was  
impossible to bind the two parts        
together with wire1 and even thin bands 
of metal driven up on the tapered       
portion of the rib were not likely to   
draw the two strips together without    
crushing the wood4 ,what was finally    

done was to scrape the edges of the two 
strips where the joint had opened1      
thereby removing all the old glue1 and  
after putting fresh glue on all these   
edges the two strips were drawn together
 and bound with surgeons' tape1 which   
was found to adhere very firmly even to 
the varnished surface4  ,after repairing
 the ribs in this manner and readjusting
 the guy-wires of their framework so as 
to make the wing assume the correct     
form1 which had been slightly altered by
 the warping and twisting consequent on 
the opening up of the ribs1 everything  
was again in readiness for a test in    
free flight1 numerous tests of the      
engine having meanwhile been made both  
with the aerodrome frame inside of the  
house-boat and also when mounted on the 
launching track above4 ,the weather1    
which had been unprecedentedly bad all  
summer1 now became even worse1 and      
although short periods of calm lasting  
an hour or less occasionally occurred1  
there were for several weeks no calm    

periods long enough for completing the  
necessary preparations and making a     
test1 although the time required for    
assembling the aerodrome had been       
greatly shortened by building the 8wing 
boxes0 on the superstructure1 and in    
other ways previously described4 ,on    
several occasions when an attempt was   
made to utilize what appeared to be a   
relative calm1 the aerodrome was        
assembled on the launching apparatus and
 everything got in readiness except the 
actual fastening of the p#bfe wings and 
rudder to it1 but in every instance1    
before the wings could be actually      
applied and a flight made1 the wind     
became so strong as to absolutely       
prohibit a test4 ,on two occasions when 
the wings were actually attached1 heavy 
rain storms suddenly came up and        
drenched the machine before the wings   
could be removed1 and on several        
occasions it was necessary to leave the 
entire metal frame and engine of the    
aerodrome mounted on top of the boat all

 night1 because the heavy sea which was 
running made it impossible to utilize   
the large raft in returning the frame to
 the interior of the boat4  ,finally1   
however1 after it seemed almost useless 
to hope for calm weather1 what appeared 
to be a most propitious day arrived on  
,october #g4 ,the wind which had been   
quite high in the early morning         
gradually quieted until at #aj a4 m4 it 
was blowing only about twelve miles per 
hour and the indications were that it   
would quiet down still more4 ,every     
energy was concentrated in getting the  
aerodrome ready at the earliest possible
 moment1 as previous experience had     
shown too clearly that the conditions   
might be completely reversed in less    
than an hour4 ,as the tide and wind     
caused the boat to swing up the river   
from its buoy1 and thus made the        
launching track point down the river1   
the steam tug-boat was sent down the    
river for a distance of a mile or more  
so that1 should the aerodrome come down 

into the water without being able to    
make a return trip to the house-boat1   
the tug-boat would be able to reach it  
quickly and render assistance to both   
the writer and the machine should they  
need it4 ,at #ab4bj p4 m4 everything was
 in readiness and what appeared to be   
the decisive moment had arrived1 when   
the writer1 after starting up the engine
 and gradually raising its speed to the 
maximum1 and after taking the last      
survey of the whole machine to insure   
that everything was as it should be1    
finally gave the orders to release it4  
,although the writer did not have the   
privilege of seeing it glide down the   
track1 as his attention was too         
thoroughly engaged in insuring that he  
was in the proper position for reaching 
immediately any of the control          
apparatus1 either of the aerodrome or of
 the engine1 yet those who did witness  
the actual passage of the machine down  
the track have said that the sight was  
most impressive and majestic4 ,no sign  

of jar was apparent when the machine was
 first released1 but with lightning-like
 rapidity it gathered its speed as it   
rushed down the sixty feet of track1 the
 end of which it reached in three       
seconds1 at which time it had attained a
 speed of something over thirty-two feet
 per second4 ,just as the machine       
reached the end of the track the writer 
felt a sudden shock1 immediately        
followed by an indescribable sensation  
of being free in the air1 which had     
hardly been realized before the         
important fact was intuitively felt that
 the machine was plunging downward at a 
very sharp angle1 and he instinctively  
grasped the wheel which controls the    
,pnaud tail and threw it to its         
uppermost extent in an attempt to       
depress the rear of the machine and     
p#bff thereby overcome the sharp angle  
of descent4 ,finding that the machine   
made no response to this extreme        
movement of the tail1 he immediately    
realized that a crash into the water was

 unavoidable and braced himself for the 
shock4 ,the tremendous crash of the     
front wings being completely demolished 
as they struck the water had hardly     
become apparent before he found himself 
and the machine plunging downward       
through the water4 ,by some instinct he 
grasped the main guy-wires which were   
above his head1 and pulling himself     
through the narrow space between them   
freed himself from the machine and swam 
upward as rapidly as possible4 ,a few   
moments after reaching the surface of   
the water the uppermost point of the    
pyramid of the machine was seen to      
project from the water and he swam over 
and sat down on it until a row-boat     
could be sent to it from the nearby     
power-boat4  ,the first thing that the  
writer saw after looking around him was 
a newspaper reporter1 his boatman       
expending the utmost limit of his power 
in pushing his boat ahead to be the     
first one to arrive4  ,after giving     
directions to the workmen regarding the 

recovery of the machine1 the writer     
returned to the house-boat to obtain dry
 clothing1 and although his first       
inclination was not to make any         
statement until a complete examination  
could be made to determine both the     
cause of the lack of success and also   
the extent of the damage which had been 
sustained by the machine1 yet owing to  
the very great pressure brought to bear 
by the press representatives who said   
that unless some statement was given out
 they would write their own conclusions 
as to the cause of the mishap1 he       
finally gave out the following          
statement3    ,,statement ,,made ,,by   
,,mr4 ,,manly ,,to ,,associated ,,press 
8,it must be understood that the test   
to-day was entirely an experiment1 and  
the first of its kind ever made4 ,the   
experiment was unsuccessful4 ,the       
balancing1 upon which depends the       
success of a flight1 was based upon the 
tests of the models and proved to be    
incorrect1 but only an actual trial of  

the full-size machine itself could      
determine this4 ,my confidence in the   
future success of the work is unchanged4
 ,i can give you no further information4
 ,i shall make a formal report to       
,secretary ,langley40  ,illustration3   
,,pl4 #ie  ,,flight ,,of ,,large        
,,aerodrome1 ,,october #g1 #aijc        
,illustration3 ,,pl4 #if  ,,flight ,,of 
,,large ,,aerodrome1 ,,october #g1 #aijc
  ,,photograph ,,by ,t4 ,w4 ,,smillie   
,after recovering the machine the       
foreman of the workmen 7,mr4 ,reed7 who 
together with ,mr4 ,mc,donald were the  
only ones on top of the boat when the   
launching actually took place1 busied   
himself to discover what had caused the 
jerk to the machine at the moment it was
 released1 which had been immediately   
followed by the great depression of the 
front end4 ,after some little time he   
discovered that the upright guide at the
 extreme front of the launching car     
7which1 as heretofore stated1 was       
slotted to receive a metal lug          

projecting from the end of the guy-post1
 and thus prevent the front end of the  
p#bfg framework from being twisted by a 
side wind striking the machine while it 
was still on the launching car7 had been
 distorted1 the metal cap on it being   
stretched out of shape in a way which   
indicated that the pin of the front     
guy-post had hung in the cap1 and that  
the guy-post was not therefore free from
 this part of the car when the end of   
the launching track dropped4 ,the shock 
which the writer felt at the moment of  
launching and which had also been seen  
by others to occur was thus conclusively
 shown to have been due to the falling  
track1 dragging the front end of the    
machine down with it4 ,as the machine   
was travelling forward and the car had  
been almost instantly brought to a      
standstill by its buffer pistons        
co-acting with the buffer cylinders at  
the foot of the track1 this front       
guy-post had been pulled backwards1 and 
thus not only pulled the main guy-wires 

of the wings backwards and thereby      
depressed the front edge of the front   
wings so that they had no angle of      
inclination1 but had also bent the front
 end of the metal framework             
downward1--effects which were discovered
 from the later examination of the frame
 and the guy-post itself4 ,from the     
instantaneous photographs which were    
obtained1 indisputable evidence was     
obtained that this was what actually    
occurred4 ,referring to the photograph1 
,plate #ie1 which was taken by ,mr4 ,g4 
,h4 ,powell1 ,secretary of the ,board of
 ,ordnance and ,fortification1 and which
 shows the machine just a few feet in   
front of the point where it was actually
 launched1 it will at once be seen that 
the front end of the frame is bent      
downward and that the front guy-post    
instead of being parallel with the rear 
one has been deflected backward at the  
lower end through an angle of #cj       
degrees4 ,referring further to the      
photograph1 ,plate #if1 which was taken 

at the same instant as the one just     
described1 it will be seen that even    
this one1 which is a view of the machine
 as it passed almost directly over ,mr4 
,smillie's head1 most clearly shows the 
extreme extent to which the front wings 
had been distorted1 the rear edges of   
the wings near the frame having been    
twisted up until they struck the        
cross-frame1 and the outer ends being   
free to twist had been forced up very   
much higher4  ,after completing the     
recovery of the machine and the         
examination as to the extent of the     
injuries it had sustained1 and finding  
unquestionable evidence that the        
accident had been caused by the front   
guy-post hanging in its guide block on  
the launching car1 the workmen were set 
to work straightening out and arranging 
the various parts1 fittings and         
accessories1 and cleaning up the engine 
which fortunately had sustained no      
injury whatever4 ,after a consultation  
in ,washington with ,mr4 ,langley1 who  

had been unable to be present at the    
experiment1 both concerning what had    
already occurred and also what should be
 done regarding the future of the work1 
and in view of the fact that the        
statement which the writer had given to 
the press representatives1 immediately  
after the accident1 had been made before
 there had been time to make an         
examination of the machine itself1 it   
was decided that it would be best to    
give to the press p#bfh a short         
statement to correct the earlier one1   
and ,mr4 ,langley accordingly made      
public the following note3   8,mr4      
,langley states that he was not an eye  
witness of the experiment  at ,widewater
 yesterday1 having been detained in     
,washington by  business1 but that on   
the report of ,mr4 ,manly1 immediately  
in  charge1 he is able to say that the  
latter's first impression that  there   
had been defective balancing was        
corrected by a minuter  examination1    
when the clutch1 which held the         

aerodrome on the  launching ways and    
which should have released it at the    
instant of  the fall1 was found to be   
injured4   8,the machinery was working  
perfectly and giving every reason to    
anticipate a successful flight1 when    
this accident 7due wholly to  the       
launching mechanism7 drew the aerodrome 
abruptly downward at the  moment of     
release and cast it into the water near 
the house-boat4  ,the statement that the
 machine failed for lack of power to fly
 was  wholly a mistaken one4   8,the    
engine1 the frame and all the more      
important parts were  practically       
uninjured4 ,the engine is actually in   
good working order4  ,the damage done   
was confined to the slighter portions1  
like the  canvas wings and propellers1  
and these can be readily replaced4      
8,the belief of those charged with the  
experiment in the ultimate  successful  
working of the machine is in no way     
affected by this  accident1 which is one
 of the large chapter of accidents that 

beset  the initial stages of experiments
 so novel as the present ones4  ,it is  
chiefly unfortunate in coming at the end
 of the season when  outdoor work of    
this sort is impossible4   8,whether the
 experiments will be continued this year
 or not has not  yet been determined40  
,in view of the many inaccurate accounts
 published in the daily press at the    
time of this experiment1 special        
attention is directed to the fact that  
even under the enormous strain to which 
the aerodrome was subjected1 due to its 
striking the water at an angle of       
approximately forty-five degrees and at 
a speed certainly not less than forty   
miles an hour1 no bending or distortion 
of any kind was found in the frame after
 it was recovered1 except that a slight 
depression at the front had been        
produced by the lower guy-post catching 
on the launching car1 as previously     
described4 ,this is very clearly seen in
 ,plate #ig1 ,fig4 #a1 which shows the  
aerodrome being hoisted from the water1 

and in ,plate #ig1 ,fig4 #b1 which shows
 it just afterwards resting on the raft1
 the wings1 tail and rudder having been 
completely demolished by towing it      
through the water to the house-boat from
 the place where it struck the water4   
,this single distortion1 therefore1 was 
in no way a result of the strains       
experienced by the frame either while it
 was in the air or when it struck the   
water4 ,some of the press reports1 and1 
in fact1 some of the accounts published 
in the scientific press1 stated that the
 aerodrome frame had proved so weak that
 it broke while the machine was in the  
air1 and that this was the cause of the 
accident4 ,nothing could be farther from
 the actual facts than this1 for though 
there were many things connected with   
the machine which could not be properly 
tested until it was actually in the air1
 yet the strength of the frame had been 
most thoroughly p#bfi tested in the     
shops prior to the trial1 and it had    
been found that with the frame supported

 only at the extreme front and rear1 no 
appreciable deflection was produced upon
 it by the concentrated weight of four  
men at the center1 even when they       
simultaneously jumped up and down on it4
 ,that the aerodrome frame was amply    
strong was further evidenced by the fact
 that in the later trial1 hereafter     
described1 no injury was sustained by   
the frame even when the machine turned  
over in mid-air and struck the water    
flat on its back4 ,in fact1 no point    
regarding the aerodrome is more certain 
than that the frame was more than strong
 enough for its purpose4  ,plates #ih to
 #ajj show the aerodrome in the water   
from the moment after it arose and the  
writer1 who had extricated himself while
 it was plunging down through the water 
and beat it to the surface1 had swum    
over to it and sat down on the upper    
pyramid to await a row-boat1 until the  
machine was taken in tow by the         
tug-boat4  ,as the weather conditions   
were continually growing worse1 owing to

 the lateness of the season1 it was     
decided that it would be absolutely     
impossible to undertake to keep the     
house-boat down the river until the     
aerodrome could be repaired and another 
test made1 and the writer accordingly   
returned to ,quantico on the following  
day1 expecting to take the tug-boat from
 there to the house-boat and complete   
arrangements for bringing everything to 
,washington4 ,on reaching ,quantico1    
however1 it was found that a most       
violent storm was raging on the river1  
and had1 in fact1 been increasing in    
violence since the evening of ,october  
#g1 immediately following the trial4 ,on
 account of the storm it was impossible 
to reach the house-boat or to get into  
communication with the workmen1 who had 
sought refuge at the hotel at ,clifton  
,beach1 as the tug-boat itself was not  
at the point at which it was expected to
 be found1 and1 in fact1 it had not been
 seen by any of the river people since  
the morning of ,october #h1 when it was 

seen taking the workmen from the boat to
 ,clifton ,beach4 ,two days later1 or   
,october #aa1 when the storm had        
subsided and the tug-boat1 which had    
been blown many miles down the river1   
was able to return the workmen to the   
house-boat1 it was found that the storm 
had made a complete wreck of all the    
row-boats1 the power-launch1 and the    
large raft4 ,the row-boats had been     
completely demolished on the beaches1   
the launch had been broken from its     
moorings to the house-boat and driven   
ashore some four miles down the river1  
where it was found with the deck torn   
completely off1 a large hole stove in it
 amidships1 and the engine seriously    
damaged1 while the raft had been very   
seriously damaged on the beach many     
miles down the river4 ,after making     
temporary repairs to the raft and       
getting it launched1 it was used as a   
floating dock for making temporary      
repairs on the power-launch2 both were  
then returned to their moorings at the  

house-boat and everything got in        
readiness for towing the house-boat to  
,washington1 and this was finally       
accomplished on ,october #ab4 p#bgj     
,even while the boat was en route some  
of the workmen were busily engaged in   
the repair of the damaged parts1 the    
others having been sent ahead to        
,washington to begin work on the        
construction of new wings1 so that      
another trial could be had at the       
earliest moment that the weather would  
permit4  ,one extra pair of wings was on
 hand1 but these had been stored in the 
house-boat while it was down the river1 
and the damp weather1 which had caused  
such serious damage to the cross-ribs of
 the wings which were actually used1 had
 also so seriously affected the ribs of 
these extra wings that it was necessary 
to discard some of them and repair the  
others4 ,an extra ,pnaud tail was on    
hand1 as well as a steering rudder1 and 
it was estimated that unless some       
unforeseen delay occurred the aerodrome 

would be ready for flight in three      
weeks4  ,after making a careful         
examination of the places on the river  
which seemed most available for an      
experiment1 it was finally decided to   
make the next test just off the ,potomac
 ,flats1 at the junction of the main    
body of the river and the ,eastern      
,branch1 the traffic on this part of the
 river1 which would have been more      
dangerous and troublesome during the    
summer1 being quite light at this time  
of the year4 ,by making the experiment  
at this point it was possible to leave  
the house-boat at its dock until the    
weather seemed suitable and then have a 
tug-boat tow it to the exact point1     
which would be determined by the state  
of the wind and the tide4  ,after more  
completely examining the condition of   
the framework of the machine1 and       
discussing and maturely deliberating on 
the causes which had led to the accident
 of ,october #g1 the writer advised ,mr4
 ,langley not to make any changes either

 in the machine itself or in the        
launching apparatus1 except to remove   
the small lug from the metal rod which  
projected from the end of the guy-post1 
and which by catching in its guide on   
the launching car had been the sole     
cause of the accident4 ,the aerodrome   
was accordingly repaired so as to       
reproduce exactly the conditions which  
obtained at the time of the previous    
experiment1 except for this slight      
change1 and it was again ready for trial
 by the middle of ,november4 ,the       
weather1 however1 at this time was very 
variable1 there being at times          
comparatively quiet periods which lasted
 for only an hour or less1 which was not
 sufficient time for procuring a        
tug-boat and towing the boat to the     
proper point1 and then assembling the   
aerodrome and making a trial4 ,however1 
after many days waiting1 what appeared  
to be an exceptionally quiet day        
occurred on ,december #h1 the wind      
quieting down by noon to such an extent 

that practically a dead calm prevailed4 
,vigorous search was immediately        
instituted for a tug-boat to tow the    
house-boat to the point selected1 but it
 was very late in the afternoon before  
one could be procured1 and by the time  
the boat arrived at the proper place    
darkness was descending and a strong    
p#bga and exceedingly gusty wind had    
sprung up1 and it seemed almost         
disastrous to attempt an experiment4    
,illustration3 ,,pl4 #ig  ,,aerodrome   
,,being ,,recovered1 ,,october #g1 #aijc
  ,illustration3 ,,pl4 #ih  ,,aerodrome 
,,in ,,water1 ,,october #g1 #aijc       
,illustration3 ,,pl4 #ii  ,,aerodrome   
,,in ,,water1 ,,october #g1 #aijc       
,illustration3 ,,pl4 #ajj  ,,aerodrome  
,,in ,,water1 ,,october #g1 #aijc       
,however1 the funds which had been      
appropriated by the ,board of ,ordnance 
and ,fortification had been exhausted   
nearly two years before1 and all the    
expense since that time had been met    
from a special fund of the ,smithsonian 

,institution4 ,but1 owing to the heavy  
drains which the work had made upon this
 fund1 ,mr4 ,langley felt unwilling to  
draw further upon it1 and since there   
were no other funds available from which
 to meet the expenses which would be    
incurred by postponing the experiments  
until spring1 it was decided that it was
 practically a case of 8now or never10  
and although the river was full of large
 blocks of floating ice several inches  
thick1 which added enormously to the    
danger involved in the experiment1 the  
writer decided to make the test         
immediately so that the long-hoped-for  
success1 which seemed so certain1 could 
be finally achieved4  ,after            
considerable delay1 due to the great    
difficulty of properly assembling the   
huge wings in the strong and gusty wind1
 into which the boat could not be kept  
directly pointed1 owing both to the     
strong tide which was running and to the
 fact that the wind itself was rapidly  
varying through as great a range as     

ninety degrees1 and after many minor    
delays1 due to causes too numerous to   
mention1 the aerodrome was finally ready
 for test4  ,the wind was exceedingly   
gusty1 varying in velocity from twelve  
to eighteen miles per hour and shifting 
its direction most abruptly and         
disconcertingly1 so that the aerodrome  
was at one moment pointed directly into 
it and at the next moment side gusts    
striking under the port or starboard    
wings would wrench the frame severely1  
thus tending to twist the whole machine 
from its fastenings on the launching    
car4 ,after starting up the engine and  
bringing it to full speed1 the writer   
gave the signal for the machine to be   
released1 and it started quietly1 but at
 a rapidly accelerated pace1 down the   
launching track4 ,exactly what happened1
 either just before or just as the      
aerodrome reached the end of the track1 
it has been impossible to determine1 as 
all the workmen and visitors had gone to
 their stations on the various auxiliary

 boats1 except the two workmen 7,mr4    
,reed and ,mr4 ,mc,donald7 who had been 
retained on top of the boat to assist in
 the launching4 ,it had grown so dark   
that the cameras of ,mr4 ,smillie1 the  
official photographer1 were unable to   
get any impression when he used them1   
owing to the extreme rapidity of the    
shutters with which they were equipped4 
,fortunately1 one photograph of the     
machine while still in the air was      
secured1 which shows the result of what 
had occurred in the launching and before
 any further damage had been caused by  
its coming down into the water1 but the 
all-important question as to just what  
caused the accident which did occur     
remains to a certain extent a mystery4  
p#bgb  ,mr4 ,reed1 the foreman1 who was 
qualified to observe accurately1 not    
only through his having worked          
continuously for many years on the      
machines1 but also from his having      
witnessed the numerous tests of the     
models1 states that from his position   

near the rear end of the launching track
 he noticed that at a point about ten   
feet before the machine reached the end 
of the track the ,pnaud tail seemed to  
have dropped at the rear end in some    
inexplicable way so that it was dragging
 against the cross-pieces of the track1 
and that at the next instant1 when the  
car reached the end of the track1 he saw
 the machine continue onward1 but the   
rudder and whole rear portion of the    
frame and the wings seemed to be        
dragging on the launching car4 ,mr4     
,mc,donald1 the head machinist1 states  
that he had his attention so            
concentrated on the engine1 which he    
noticed was working perfectly and       
driving the propellers at a higher rate 
of speed than he had ever before seen it
 do1 that he did not see anything happen
 until he saw the machine shoot upward  
in the air1 gradually attaining a       
vertical position with its bow upward1  
where it was sustained for a few moments
 by the upward thrust of the propellers4

 ,after a few moments1 however1 the     
strong wind1 which was blowing from     
twelve to eighteen miles an hour        
directly ahead and acting against the   
wings which were now vertical1 drove the
 machine backwards towards the          
house-boat1 and he saw it come down into
 the water on its back1 with the writer 
gradually righting himself in accordance
 with the turning of the machine until  
he was finally hidden from view by the  
machine coming down on top of him4 ,the 
witnesses on the tug-boats seem not to  
have been able to perceive exactly what 
occurred4 ,all unite in stating that    
something seemed to happen to the       
machine just a few feet before the      
launching car reached the end of the    
track1 but what it was they could not   
say4 ,everyone who saw the accident and 
who was sufficiently familiar with the  
construction of the machine to be able  
intuitively to form an idea as to just  
what was taking place was so very close 
to the machine that when the accident   

happened everything seemed to merge into
 one vision1 which was that of the whole
 rear of the wings and rudder being     
completely destroyed as the machine shot
 upward at a rapidly increasing angle   
until it reached the vertical position  
previously mentioned4  ,the writer can  
only say that from his position in the  
front end of the machine1 where he was  
facing forward and where his main       
attention was directed towards insuring 
that the engine was performing at its   
best1 he was unable to see anything that
 occurred at the rear of the machine1   
but that just before the machine was    
freed from the launching car he felt an 
extreme swaying motion immediately      
followed by a tremendous jerk which     
caused the machine to quiver all over1  
and almost instantly he found the       
machine dashing ahead with its bow      
rising at a very rapid rate1 and that   
he1 therefore1 swung the wheel which    
controls the ,pnaud tail to its extreme 
downward limit of motion4 ,finding that 

p#bgc this had absolutely no effect1 and
 that by this time the machine had      
passed its vertical position and was    
beginning to fall backwards1 he swung   
himself around on his arms1 from which  
he supported himself1 so that in        
striking the water with the machine on  
top of him he would strike feet         
foremost4 ,the next few moments were for
 him most intense1 for he found himself 
under the water with the machine on top 
of him1 and with his cork-lined canvas  
jacket so caught in the fittings of the 
framework that he could not dive        
downward1 while the floor of the        
aviator's car1 which was pressing       
against his head1 prevented him from    
coming upward4 ,his one thought was that
 if he was to get out alive he would    
have to do so immediately1 as the       
pressure of the water on his lungs was  
beginning to make itself seriously felt4
 ,exerting all of the strength he could 
muster1 he succeeded in ripping the     
jacket entirely in two and thus freeing 

himself from the fastenings which had   
accidentally held him1 he dived under   
the machine and swam under the water for
 some distance until he thought he was  
out from under the machine4 ,upon rising
 to the surface his head came in contact
 with a block of ice1 which necessitated
 another dive to get free of the ice4   
,upon coming to the surface of the water
 he noticed ,mr4 ,hewitt1 one of the    
workmen1 just about to plunge in2 before
 he could call out to indicate he was   
safe1 ,mr4 ,hewitt had heroically       
plunged in with the expectation of      
diving under the machine where he       
believed the writer to be entangled4    
,finding the house-boat was being       
rapidly shoved upon him1 imperilling the
 life of both himself and ,mr4 ,hewitt1 
besides the safety of the aerodrome1 the
 writer gave orders that the tug-boat   
reverse and tow the house-boat away4    
,then1 with the assistance of a         
row-boat1 he reached the house-boat1    
where willing hands drew him on board   

and assisted him into dryer and warmer  
clothing4  ,meanwhile1 it had become    
quite dark1 and when the writer went    
outside to see about the aerodrome he   
found that the men on the tug-boat1 in  
their zeal to render assistance1 had    
fastened a rope to the rear end of the  
machine1 at the same time pulling it in 
the direction in which the front end was
 pointed1 and through their ignorance   
had forced it down into the muddy bottom
 of the river and broken the main       
framework completely in two1 thus       
rendering it absolutely impossible with 
the facilities at hand to remove it from
 the water to the interior of the boat4 
,it was finally necessary to tie the    
wrecked machine to the stern of the     
house-boat and have the boat towed to   
its dock where the mast and boom were   
assembled and the wrecked machine       
hoisted from the water4 ,this was       
finally accomplished about midnight1    
when the workmen1 who had been working  
at a fever heat all day1 were glad to   

close up the work for the day1 which had
 proved so unfortunate4  ,illustration3 
,,pl4 #aja  ,,attempted ,,launching ,,of
 ,,aerodrome1 ,,december #h1 #aijc      
,,enlargement ,,of ,,photograph ,,by    
,,the ,,washington ,,star  ,as has      
already been remarked1 darkness had     
descended to such an extent that the    
light was not strong enough to give     
photographs with the very rapid shutters
 with which ,mr4 ,smillie had his       
cameras equipped1 and that1 therefore1  
p#bgd incontrovertible evidence1 which  
the instantaneous photographs had given 
as to just what had occurred to the     
machine in the accident of ,october #g1 
was in this case unfortunately lacking4 
,it was at first thought that no        
photographs had been obtained while the 
machine was actually in the air1 but it 
was later found that by some rare       
fortune the photographer for ,the       
,washington ,star had secured a         
photograph1 which1 while small1 showed  
very distinctly some decidedly          

interesting facts4 ,an enlargement of   
this photograph is shown in ,plate #aja1
 by the kind permission of ,the         
,washington ,star4 ,referring to this   
photograph1 it will be seen that at the 
moment it was taken the machine was     
practically vertical in the air1 and it 
confirms the testimony of the eye       
witnesses1 and also the writer's        
impression that the machine was         
maintained in a vertical position for   
several moments by the upward thrust of 
the propellers4 ,it will also be seen   
that the ,pnaud tail has been completely
 demolished and is hanging as a limp    
roll of cloth1 which the strong wind has
 deflected backwards towards the        
house-boat1 the port rear wing has      
broken its main ribs1 both where they   
are attached to the main frame and also 
about midway the length of the wing1 the
 outer end being partially folded       
towards the frame4 ,the starboard rear  
wing has also broken both of its main   
ribs at the point where they are joined 

to the frame1 and they have also broken 
at a point about one-third their length 
from the frame1 the outer end being     
likewise folded towards the frame4 ,by a
 still more careful inspection1 it will 
also be seen that the port front wing is
 apparently uninjured1 while the        
starboard front wing has broken the     
middle main rib at a point between the  
sixth and seventh cross-ribs1 and while 
it cannot be distinctly seen at first   
that the front main rib has also broken 
at the same point very careful          
inspection will show that this is the   
case1 as the sixth and seventh ribs1    
showing as faintly darker lines in the  
photograph1 are seen to be displaced1 so
 that they are together and actually    
crossing each other4 ,it will           
furthermore be seen that both front     
wings have been pressed upward by the   
wind until their tips near the inner    
ends are in contact with the            
cross-frame4 ,this could not have       
happened unless the front guy-post had  

given away either by bending or         
breaking4 ,the fact that it has given   
way is further evidenced by a more      
careful examination of the extreme front
 end of the machine1 where it will be   
seen that the bowsprit and the curved   
tubes which form the extreme end of the 
steel frame have been bent from a       
straight line with reference to the main
 frame4 ,this bending of the bowsprit   
and the curved tubes could be produced  
only by the front guy-post coming in    
contact with some obstruction on the    
launching car as the machine left it4   
,it is known very certainly that the    
rear end of the machine came in contact 
with the launching car1 as the car      
itself shows a very deep gash in the    
wooden cross-piece at its center1 which 
was produced by the port-bearing point  
at the rear striking it4 ,as this       
bearing point was elevated five feet    
above the cross-piece of the launching  
car1 and was also six feet six inches to
 p#bge the rear of the point where the  

wood is torn1 this rear-bearing point   
must have travelled downward at an angle
 of approximately thirty-eight degrees  
in order for the bearing point to strike
 the car at this point4 ,as the lower   
end of the rear guy-post was only       
eighteen inches above the cross-piece of
 the launching car1 it1 of course1 would
 be broken before the bearing point     
could descend so much4 ,as has been     
previously stated1 ,mr4 ,reed1 who was  
at the rear of the launching track1     
states very positively that the rudder  
was dragging on the track at least ten  
feet before the launching car reached   
the front end of the track where the    
machine was actually launched4 ,there   
are several ways in which the rudder    
could have gotten down on the track1 but
 positive information is lacking4 ,if it
 was dragging on the track1 as ,mr4     
,reed states 7and from his extended     
experience and rather acute powers of   
observation ,i should place great       
credence in his report71 the subsequent 

demolition of the guy-posts succeeded by
 the destruction of the rear wings and  
serious injury of the front ones is     
easily explained4 ,if the dropping of   
the rudder on the track occurred from   
the breaking of the upper rudder post1  
over which the upper control wire       
passed1 the lower vertical surface would
 first come in contact with the track1  
and the destruction of this part would  
certainly occasion subsequent           
destruction of the horizontal and upper 
vertical surfaces of the rudder1 leaving
 the central rib of the rudder still    
attached to the frame1 and upon the     
machine being released from the car a   
few moments later this destroyed rudder 
would easily catch in the launching car 
and pull the aerodrome down on it1 and  
thus cause the destruction of the       
guy-posts1 wings1 and so forth4 ,if the 
dropping of the rudder was caused       
primarily by its main rib breaking loose
 from its connection with the frame1 the
 rudder would still be dragged along    

behind the machine by the wire cords    
through which it was operated1 and the  
subsequent launching of the machine     
would still give the rudder every chance
 to catch in the launching car and drag 
the machine down on it4  ,it can        
therefore be said that1 while positive  
information is lacking1 there is very   
strong evidence that the accident in the
 launching was due to the rudder        
becoming entangled with the launching   
track owing to the breakage of some part
 of the mechanism by which it was       
connected to the main frame4  ,it is of 
importance to note that the photograph  
furnishes incontrovertible evidence that
 the main frame of the machine was in no
 way injured1 except for the slight     
bending of the forward curved extension1
 and that1 therefore1 the accident was  
in no way due to the weakness of the    
frame4 ,the main frame was not even     
injured by the machine coming down in   
the water on its back1 and the later    
damage was entirely caused by the       

combination of the ignorance of the     
tug-boatmen and the darkness in which   
they were working1 when they attempted  
to tow it to the rear of the house-boat 
so that it could be removed from the    
water4 p#bgf  ,on the day following the 
trial a very careful inspection was made
 in the hope of obtaining some more     
definite information as to just what    
caused the accident1 but the serious    
injury to the machine caused by the     
tug-boatmen breaking it in the water had
 so greatly tangled things up that it   
was impossible to tell anything about   
it4 ,the workmen were immediately put to
 work removing fittings from the broken 
wings1 rudder1 etc41 and dismounting the
 engine1 which was immediately          
reassembled on its testing frame and    
found to be absolutely uninjured4 ,the  
transverse frame of the machine was     
comparatively uninjured1 the damage done
 by the men on the tug-boat being the   
breaking of the machine in two at a     
point just back of the cross-frame1     

together with the consequent destruction
 of the bearing points1 8trestle10 and  
certain fittings by which the main      
guy-wires were attached to the main     
tubes and pyramids4  ,the situation     
which now existed was most distressing  
and disheartening4 ,mr4 ,langley felt   
that he could not approve of further    
expenditures from any ,smithsonian fund1
 and the ,board of ,ordnance and        
,fortification of the ,war ,department  
having been severely criticised on the  
floors of ,congress for its original    
allotment for the work1 deemed it       
inexpedient to incur a possible         
curtailment of the funds annually placed
 at its disposal for general            
experimental work through a             
manifestation of continued interest in  
the flying machine4  ,as has already    
been stated1 representatives from the   
,board of ,ordnance and ,fortification  
of the ,war ,department were present at 
both tests of the large aerodrome2 on   
,october #g ,major ,montgomery ,m4      

,macomb and ,mr4 ,g4 ,h4 ,powell1 and on
 ,december #g ,general ,w4 ,f4 ,randolph
 accompanied by ,major ,macomb and ,mr4 
,powell1 represented the ,war           
,department1 and ,dr4 ,f4 ,s4 ,nash1 at 
that time ,contract ,surgeon1 ,u4 ,s4   
,a41 was officially present at both     
trials to render medical assistance     
should it be needed4  ,by permission of 
the ,war ,department1 the official      
report of the tests submitted by ,major 
,macomb to the ,board of ,ordnance and  
,fortification is here made public3     
,enc4 #ast to #c;d end't1 ,,bof #faia4  
,,report   ,experiments with working    
models which were concluded ,august #h  
last  having proved the principles and  
calculations on which the design  of the
 ,langley aerodrome was based to be     
correct1 the next step  was to apply    
these principles to the construction of 
a machine of  sufficient size and power 
to permit the carrying of a man1 who    
could  control the motive power and     
guide its flight1 thus pointing the  way

 to attaining the final goal of         
producing a machine capable of  such    
extensive and precise aerial flight1    
under normal atmospheric  conditions1 as
 to prove of military or commercial     
utility4   ,mr4 ,c4 ,m4 ,manly1 working 
under ,prof4 ,langley1 had1 by the      
summer of  #aijc1 succeeded in          
completing an engine-driven machine     
which under  favorable p#bgg atmospheric
 conditions was expected to carry a man 
for any time up to half an hour1 and to 
be capable of having its  flight        
directed and controlled by him4   ,the  
supporting surface of the wings was     
ample1 and experiment showed  the engine
 capable of supplying more than the     
necessary motive power4   ,owing to the 
necessity of lightness1 the weight of   
the various  elements had to be kept at 
a minimum1 and the factor of safety in  
construction was therefore exceedingly  
small1 so that the machine  as a whole  
was delicate and frail and incapable of 
sustaining any  unusual strain4 ,this   

defect was to be corrected in later     
models  by utilizing data gathered in   
future experiments under varied         
conditions4   ,one of the most          
remarkable results attained was the     
production of a  gasoline engine        
furnishing over fifty continuous        
horse-power for a  weight of one hundred
 and twenty pounds4   ,the aerodrome1 as
 completed and prepared for test1 is    
briefly  described by ,prof4 ,langley as
 8built of steel1 weighing complete     
about seven hundred and thirty pounds1  
supported by one thousand and  forty    
feet of sustaining surface1 having two  
propellers driven by a  gas engine      
developing continuously over fifty brake
 horse-power40   ,the appearance of the 
machine prepared for flight was         
exceedingly  light and graceful1 giving 
an impression to all observers of being 
capable of successful flight4   ,on     
,october #g last everything was in      
readiness1 and ,i witnessed the         
attempted trial on that day at          

,widewater1 ,va41 on the ,potomac4 ,the 
engine worked well and the machine was  
launched at about #ab4ae p4 m4  ,the    
trial was unsuccessful because the front
 guy-post caught in its  support on the 
launching car and was not released in   
time to give  free flight1 as was       
intended1 but on the contrary1 caused   
the front  of the machine to be dragged 
downward1 bending the guy-post and      
making the machine plunge into the water
 about #ej yards in front of  the       
house-boat4 ,the machine was            
subsequently recovered and brought  back
 to the house-boat4 ,the engine was     
uninjured and the frame only  slightly  
damaged1 but the four wings and rudder  
were practically  destroyed by the first
 plunge and subsequent towing back to   
the  house-boat4 ,this accident         
necessitated the removal of the         
house-boat  to ,washington for the more 
convenient repair of damages4   ,on     
,december #h last1 between #d and #e p4 
m41 another attempt at a  trial was     

made1 this time at the junction of the  
,anacostia with the  ,potomac1 just     
below ,washington ,barracks4   ,on this 
occasion ,general ,randolph and myself  
represented the ,board  of ,ordnance and
 ,fortification4 ,the launching car was 
released at  #d4de p4 m41 being pointed 
up the ,anacostia towards the ,navy     
,yard4  ,my position was on the tug     
,bartholdi about #aej feet from and at  
right angles to the direction of        
proposed flight4 ,the car was set  in   
motion and the propellers revolved      
rapidly1 the engine working  perfectly1 
but there was something wrong with the  
launching4 ,the  rear guy-post seemed to
 drag1 bringing the rudder down on the  
launching ways1 and a crashing1 rending 
sound1 followed by the  collapse of the 
rear wings1 showed that the machine had 
been wrecked  in the launching1 just    
how1 it was impossible for me to see4   
,the  fact remains that the rear wings  
and rudder were wrecked before the      
machine was free of the ways4 ,their    

collapse deprived the machine  of its   
support in the rear1 and it consequently
 reared up in front  under the action of
 the motor1 assumed a vertical position1
 and then  toppled over to the rear1    
falling into the water a few feet in    
front  of the boat4 p#bgh   ,mr4 ,manly 
was pulled out of the wreck uninjured   
and the wrecked  machine was            
subsequently placed upon the house-boat1
 and the whole  brought back to         
,washington4   ,from what has been said 
it will be seen that these unfortunate  
accidents have prevented any test of the
 apparatus in free flight1  and the     
claim that an engine-driven1            
man-carrying aerodrome has been         
constructed lacks the proof which actual
 flight alone can give4   ,having       
reached the present stage of advancement
 in its development1  it would seem     
highly desirable1 before laying down the
  investigation1 to obtain conclusive   
proof of the possibility of free        
flight1 not only because there are      

excellent reasons to hope for  success1 
but because it marks the end of a       
definite step toward the  attainment of 
the final goal4   ,just what further    
procedure is necessary to secure        
successful flight  with the large       
aerodrome has not yet been decided upon4
 ,professor  ,langley is understood to  
have this subject under advisement1 and 
will doubtless inform the ,board of his 
final conclusions as soon as            
practicable4   ,in the meantime1 to     
avoid any possible misunderstanding1 it 
should  be stated that even after a     
successful test of the present great    
aerodrome1 designed to carry a man1 we  
are still far from the  ultimate goal1  
and it would seem as if years of        
constant work and  study by experts1    
together with the expenditure of        
thousands of  dollars1 would still be   
necessary before we can hope to produce 
an  apparatus of practical utility on   
these lines4   ,m4 ,m4 ,,macomb1  ,major
 ,artillery ,corps4   ,,washington1     

,january #f1 #aijd4  ,the attitude of   
the ,board of ,ordnance and             
,fortification1 with reference to       
rendering further financial assistance  
to the work1 is clearly shown by the    
following extract from the official     
report of the ,board on ,october #f1    
#aijd1 to the ,secretary of ,war3       
,,the ,,langley ,,aerodrome   ,early in 
the year #ahih a board composed of      
officers of the ,army  and ,navy was    
appointed to examine the models and     
principles of the  aerodrome devised by 
,dr4 ,s4 ,p4 ,langley1 ,secretary of the
 ,smithsonian  ,institution1 and to     
report whether or not1 in its opinion1 a
 large  machine of this design could be 
built1 and1 if so1 whether it would  be 
of practical value4   ,the report of    
this board was referred to the ,board of
 ,ordnance and  ,fortification for      
action1 and ,doctor ,langley was invited
 to appear  before the ,board and       
further explain the proposed            
construction4   ,in view of the great   

utility of such a device1 if a practical
  success1 the ,board1 on ,november #i1 
#ahih1 made an allotment of  #be1jjj for
 the construction1 development1 and test
 of an aerodrome  to be made under the  
direction of ,doctor ,langley1 with the 
understanding that an additional        
allotment of the same amount would  be  
made later4 ,on ,december #ah1 #ahii1   
the additional allotment of  #be1jjj was
 made4   ,the construction of the       
machine was delayed by ,doctor          
,langley's  inability to procure a      
suitable motor1 which he was finally    
obliged  to design4 ,the aerodrome was  
completed about ,july #ae1 #aijc1 and   
preparations for its test were made at a
 point in the ,potomac ,river  about #dj
 miles below ,washington4 p#bgi         
,preliminary arrangements having been   
completed and tests made of  a          
quarter-size model1 the first attempt at
 actual flight with the  man-carrying   
aerodrome was made on ,october #g1      
#aijc4   ,on this occasion there were   

present on behalf of the ,board1 ,major 
,m4  ,m4 ,macomb1 ,artillery ,corps1 and
 ,mr4 ,g4 ,h4 ,powell1 clerk of the     
,board4   ,major ,macomb in his report  
to the ,board stated that--   8,the     
trial was unsuccessful because the front
 guy-post caught in its  support on the 
launching car and was not released in   
time to give  free flight1 as was       
intended1 but on the contrary1 caused   
the front  of the machine to be dragged 
downward1 bending the guy-post and      
making the machine plunge into the water
 about #ej yards in front of  the       
house-boat40  ,this accident            
necessitated the removal of the         
house-boat to ,washington for the more  
convenient repair of damages4 ,the      
repairs having been completed1 on       
,december #h1 #aijc1 another attempt at 
a trial was made1 this time at the      
junction of the ,anacostia and the      
,potomac ,rivers4 ,general ,w4 ,f4      
,randolph and ,major ,macomb1 members of
 the ,board1 and ,mr4 ,powell1 were     

present4 ,major ,macomb reported as     
follows3   8,the launching car was      
released at #d4de p4 m4 4 4 4 ,the car  
was set  in motion and the propellers   
revolved rapidly1 the engine working    
perfectly1 but there was something wrong
 with the launching4 ,the  rear guy-post
 seemed to drag1 bringing the rudder    
down on the  launching ways1 and a      
crashing1 rending sound1 followed by the
  collapse of the rear wings1 showed    
that the machine had been wrecked  in   
the launching1 just how1 it was         
impossible for me to see40  ,march #c1  
#aijd1 the ,board stated that it was not
 8prepared to make an additional        
allotment at this time for continuing   
the work10 whereupon ,doctor ,langley   
requested that arrangements be made for 
a distribution of the aerodrome material
 procured jointly from funds allotted by
 the ,board and by the ,smithsonian     
,institution4 ,doctor ,langley was      
informed that all of the material would 
be left in his possession and available 

for any future work that he might be    
able to carry on in connection with the 
problem of mechanical flight4  ,that    
this refusal of the ,board of ,ordnance 
and ,fortification to render further    
assistance to the work was due to the   
fear that such action would result in a 
curtailment of their appropriation by   
,congress is clearly shown by the       
following extract from the official     
report of the ,board on ,november #ad1  
#aijh1 to the ,secretary of ,war3       
,,aerial ,,navigation   ,for a number of
 years the ,board has been interested in
 the subject  of aerial navigation1 and 
as long ago as #ahih made allotments to 
carry on experiments with a machine of  
the heavier-than-air type1  under the   
direction of the late ,dr4 ,s4 ,p4      
,langley1 ,secretary of  the            
,smithsonian ,institution1 who had made 
exhaustive experiments  in              
aerodynamics1#dh and who had            
demonstrated the practicability  of     
mechanical flight by the successful     

operation of engine-driven  models4     
,the many problems and mechanical       
difficulties met with in the            
development of the full-size machine    
have been set forth in the  various     
published statements#di p#bhj of ,doctor
 ,langley1 and the  unsuccessful outcome
 of the experiments is too well known to
 require  reiteration4 ,it may be said1 
however1 that at the time of the trials 
the ,board was of the opinion that the  
failure of the aerodrome to             
successfully operate was in no manner   
due to the machine itself1 but  solely  
to accidents in the launching apparatus1
 which caused the  wreck of the         
aerodrome before it was in free flight4 
,doctor ,langley considered it desirable
 to continue the experiments1  but the  
,board deemed it advisable1 largely in  
view of the adverse  opinions expressed 
in ,congress and elsewhere1 to suspend  
operations  in this direction4  ,these  
adverse opinions expressed in ,congress 
were wholly due to the bitter criticism 

by the newspapers1 whose hostility was  
engendered by ,mr4 ,langley's refusal to
 admit their representatives to the     
shops and house-boat where the work was 
in progress4 ,mr4 ,langley had at all   
times tried to make his position in the 
matter clear to the newspapers1 but1 on 
,august #ai1 #aijc1 at the time of one  
of his visits to the experimental       
station near ,widewater1 ,va41 he found 
the newspaper representatives so        
persistent in their misrepresentations  
of his reasons for excluding them that  
he gave out the following statement1    
which was published at that time3       
,,smithsonian ,,institution1            
,,washington1 ,d4 ,c41  ,august #ai1    
#aijc4   ,,to ,,the ,,press3 ,the       
present experiments being made in       
mechanical  flight have been carried on 
partly with funds provided by the ,board
  of ,ordnance and ,fortification and   
partly from private sources1  and from a
 special endowment of the ,smithsonian  
,institution4 ,the  experiments are     

carried on with the approval of the     
,board of ,regents  of the ,smithsonian 
,institution4   ,the public's interest  
in them may lead to an unfounded        
expectation  as to their immediate      
results1 without an explanation which is
 here  briefly given4   ,these trials1  
with some already conducted with        
steam-driven flying  machines1 are      
believed to be the first in the history 
of invention  where bodies1 far heavier 
than the air itself1 have been sustained
  in the air for more than a few seconds
 by purely mechanical means4   ,in my   
previous trials1 success has only been  
reached after initial  failures1 which  
alone have taught the way to it1 and ,i 
know no  reason why the prospective     
trials should be an exception4   ,it is 
possible1 rather than probable1 that it 
may be otherwise now1  but judging them 
from the light of past experience1 it is
 to be  regretted that the enforced     
publicity which has been given to these 
initial experiments1 which are          

essentially experiments and nothing     
else1 may lead to quite unfounded       
expectations4   ,it is the practice of  
all scientific men1 indeed of all       
prudent men1  not to make public the    
results of their work till these are    
certain4  ,this consideration1 and not  
any desire to withhold from the public  
matters in which the public is          
interested1 has dictated the policy     
thus far pursued here4 ,the fullest     
publicity1 consistent with the  national
 interest 7since these recent           
experiments have for their  object the  
development of a machine for war        
purposes71 will be given  to this work  
when it reaches a stage which warrants  
publication4   7,signed47 ,s4 ,p4       
,,langley4   ,although it was impossible
 to immediately find funds for actively 
continuing the work1 the writer finally1
 after some delay1 persuaded ,mr4       
,langley to allot a small sum from a    
limited fund which personal friends had 
some time previously placed at his      

disposal for use in any experiments he  
might wish to make4 ,this small sum was 
used to meet the expense of the workmen 
who were kept employed long enough to   
completely repair the main frame so     
that1 should further experiments be     
possible at a later time1 there would be
 no danger of important parts and       
fittings having been lost in the        
meantime1 and even if no further        
experiments were made the frame would be
 in such condition that others could    
profit from an examination of it1 the   
frame itself embodying the solution of  
many important problems which had cost  
much time and money4  ,in the spring of 
#aijd1 after the repairs to the main    
frame were well under way1 the writer on
 his own initiative undertook to see    
what could be done towards securing for 
,mr4 ,langley's disposal the small      
financial assistance necessary to       
continue the work2 but he found that    
while a number of men of means were     
willing to assist in the development of 

the aerodrome1 provided arrangements    
were made for later commercialization1  
yet none were ready to render the       
assistance from a desire to assist in   
the prosecution of scientific work4     
,many years prior to this ,mr4 ,langley 
had had some very tempting propositions 
made to him by certain business men with
 a view to carrying on the work in a way
 that would lead to later commercial    
development4 ,he had never patented     
anything previously in his life1 and    
although many friends had urged that it 
was only proper that he should patent   
whatever of value had been developed in 
connection with the aerodromes1 he      
steadfastly refused to do so4 ,he had   
given his time and his best labors to   
the world without hope of remuneration1 
and he could not bring himself at his   
stage of life to consent to capitalize  
his scientific work4 ,success seemed    
only a step away1 and his age was such  
that any delay in achieving success     
increased the probability of his not    

living to see it1 but he maintained     
positively and resolutely that1 if      
neither the ,war ,department nor others 
felt sufficient interest in the work to 
provide the small amount of funds       
necessary to continue the experiments1  
and they therefore could be continued   
only by his giving in and permitting his
 work to be capitalized1 he would have  
to deny himself the hope of living to   
see the machine achieve success4  ,the  
result is well known to all4            
,,present ,,status ,,of ,,the ,,work    
,the completely repaired frame of the   
large machine is now stored in one of   
the workshops at the ,smithsonian       
,institution4 ,the large engine1 the    
steam-driven models ,nos4 #e and #f1 and
 the quarter-size model1 driven by the  
three p#bhb horse-power gasoline engine1
 are on exhibition at the ,u4 ,s4       
,national ,museum4 ,the launching-car   
and a small amount of materials have    
also been stored away4 ,the large       
house-boat1 the construction and        

maintenance of which proved such a      
serious drain on the finances1 and the  
preservation of which would have        
entailed the continuance of heavy fixed 
charges1 has been turned over to the    
,war ,department and sold1 as has also  
the power-launch and other paraphernalia
 which it seemed useless to preserve4   
,the writer is firmly convinced that the
 aerodrome is not only correct in       
principle but that it possesses no      
inherent faults or weaknesses1 and that 
the success which the work deserves has 
been frustrated by two most unfortunate 
accidents in the launching of the       
machine4 ,other plans of launching1     
several of which were studied out during
 the early stages of the work on the    
large machine1 would have avoided the   
accident which did occur1 but1 of       
course1 might have produced others      
possibly even more disastrous1 but which
 could be determined only by actual     
trial4 ,but even recognizing certain    
fundamental weaknesses of the launching 

mechanism as used1 he believes that     
there is no inherent reason why the     
machine should not have been            
successfully launched1 and that the     
accidents which proved so disastrous in 
the two experiments were not such as    
should cause a lack of confidence in the
 final success of the aerodrome4  ,it   
might be of interest to add that the    
writer is now preparing to resume the   
work at the earliest opportunity1 and   
that the machine will be used in        
practically the form in which it existed
 at the two previous experiments1 though
 a slight change will be made permitting
 experiments over the land rather than  
the water4 ,the only thing that prevents
 an immediate resumption is the pressure
 of private business matters4  ,before  
closing this record the writer wishes to
 acknowledge the very valuable          
assistance in the work rendered by ,mr4 
,richard ,rathbun1 ,assistant ,secretary
 of the ,smithsonian ,institution1      
through his moral support and interest  

in it at all times1 and especially      
during the trying days of the summer of 
#aijc2 by ,captain ,i4 ,n4 ,lewis1 who1 
while ,recorder of the ,board of        
,ordnance and ,fortification from #ahih 
to #aijb1 manifested keen interest in   
the work and gave it his moral support  
before the ,board2 by ,professor ,john  
,m4 ,manly1 who devoted the whole of the
 summer of #aijc to it2 and by          
,professor ,w4 ,g4 ,manly1 who devoted a
 large part of the summer of #aijc to   
assistance in the preparation for the   
actual field-trials of the aerodrome4   
,mention must also be made of the very  
loyal and valuable services rendered by 
,mr4 ,r4 ,l4 ,reed1 the very efficient  
foreman of the work during the last ten 
years of its progress1 to whom much     
credit is due for his perseverance and  
skill in overcoming many of the         
difficulties which presented themselves1
 as well as to ,mr4 ,g4 ,d4 ,mc,donald1 
,mr4 ,c4 ,h4 ,darcey1 ,mr4 ,f4 ,hewitt1 
,mr4 ,r4 ,s4 ,newham p#bhc and the other

 employees who labored faithfully for   
the several years they were engaged on  
it4    ,,bl,,riot ,,machine ,,of  #aijg 
,,on ,,langley ,,type  ,since completing
 the preparation of this ,memoir1 the   
writer's attention has been called to   
some very interesting tests made at     
,issy by ,m4 ,louis ,blriot with a      
machine of the ,langley type4 ,these    
tests confirm in such a practical manner
 the conviction that the large aerodrome
 would have flown successfully had it   
not been wrecked in launching that it   
has seemed well to here quote an        
interesting description of them         
published in the 8,bollettino della     
,societ ,aeronautica ,italiana1 ,august1
 #aijg10 under the title 8,il nuovo     
aeroplano ,blriot10 a translation of    
which is as follows3    ,,the ,,new     
,,bl,,riot ,,aeroplane   ,the ,blriot   
,,iv in the form of a bird1 of which we 
spoke at length  in ,no4 #d of the      
,bulletin of this year1 does not appear 
to give good  results1 perhaps on       

account of its lack of stability1 and   
,blriot  instead of trying some         
modifications which might remedy such a 
grave fault1 laid it aside and at once  
began the construction of  a new type1  
,no4 ,v1 adopting purely and simply the 
arrangement of  the ,american1 ,langley1
 which offers a good stability 7see     
,bulletin  #aa-ab1 ,november to         
,december1 #aije1 pages #ahg and #ahh74 
,the experiments1 which were commenced a
 month ago1 were first  completely      
negative1 because the #bd ,,hp4 motor   
would not turn the  propeller1 which was
 #a4hj m4 in diameter and #a4dj m4      
pitch4   ,by advice of ,captain ,ferber1
 ,blriot reduced the pitch of his       
propeller to #j4ij m41 so that the motor
 could give all its force4   ,this      
modification was an important one for   
his aeroplane4 ,from  that moment every 
trial marked an advance4 ,on ,july #ab1 
he made a  flight of #cj m41 and the    
aviator was able to show that the       
lateral  stability was perfect4 ,on     

,july #ae1 the trial was made against a 
wind  of #f miles an hour1 but gave good
 results4 ,he made a flight of #hj  m41 
showing1 however1 that the hind part of 
the aeroplane was too  heavy4 ,in this  
flight he arose as high as a second     
story1 and on  landing the wheels and   
one propeller were somewhat damaged4    
,on ,july #bd1 repairs having been      
completed1 a new trial was made4  ,this 
time1 in order to remedy the defect in  
the balance1 ,blriot  had moved his seat
 forward about #hj cm4 ,the correction  
was too  great1 for on that day the     
aeroplane1 although the hind part arose1
  was not able to leave the ground4 ,on 
,july #bg1 after having mounted  the    
seat on wheels as skiffs1 ,blriot       
resumed the trials and made  a flight of
 #abj m41 at first moving his seat back 
and then1 after  getting started1       
bringing it forward4 ,blriot had not    
provided this  aeroplane with an        
elevating rudder1 but1 following the    
example  of ,lilienthal1 changed the    

center of gravity of the apparatus by   
moving his own person1 and after having 
established the proper angle  remained  
immovable on his seat4 ,in order to     
arise or descend1 the  aviator made use 
of the spark lever1 thus varying the    
number of  turns of the propeller4      
,during a second trial on the same day1 
having accidently reached  the limit of 
the aviation field1 ,blriot1 without    
allowing himself  to be surprised and   
obliged to descend1 decided to attempt a
 turn  by maneuvering the steering      
rudder p#bhd and to return again to  the
 center of the field4 ,with marvelous   
precision1 the aeroplane  began to      
describe a circle of about #bjj m4      
radius1 inclining as if  on a banked    
track4 ,having finished the flight1 he  
quickly regained  his balance still in  
the direction of the wind1 but on       
account of a  slight movement of the    
aviator1 the aeroplane fell to such an  
extent  that he was obliged to land4 ,he
 landed gently and without shock1       

rolling on his wheels4   ,on ,august #a1
 he made another flight of #ajj m4 in   
#f-a_/b seconds2 and  on the #fth1 one  
of #bfe m4 with one interruption4 ,while
 the attention  of the pilot was        
distracted for a moment1 the aeroplane1 
which was  flying at a height of #b or  
#c m4 above the ground1 touched the soil
  with its sustaining wheels at the end 
of #abb m4 and then immediately         
arising1 covered the remaining #adc m4  
at a height of #ab m4 ,blriot1  moving  
forward too quickly1 caused the         
aeroplane to descend swiftly  to the    
ground1 and the shock broke the axle and
 the blades of the  propeller were bent4
 ,in order to confirm this account1 we  
reproduce  what was said in the 8,auto0 
of ,august #g1 #aijg4   8,m4 ,blriot1   
continuing the trials of his aeroplane  
yesterday1  surpassed the superb results
 which he had already obtained4 ,the    
trial took place at #b o'clock in the   
afternoon on the aviation field  of     
,issy4 ,after a sustained flight of     

about #abb m4 at a height of #b  m41 the
 aeroplane touched the ground1 without  
stopping1 however1 and  set out again   
almost immediately at a height of #ab m4
 and traversed  about #adc m4 ,m4       
,blriot1 who for the time had no other  
means of  balancing but by moving his   
body1 then moved a little forward to    
stop the ascent4 ,the aeroplane plunged 
forward1 and in the fall the  propeller 
was damaged and the axle broken4   8,m4 
,blriot1 whose courage as a sportsman   
equals his learning  as an engineer1 was
 fortunately uninjured4 ,an inspection  
of the  apparatus showed that one blade 
of the propeller was bent1 which  was   
sufficient to prevent the maneuver made 
by the aviator having  its desired      
effect and contributed to the fall4 ,the
 engine will be  repaired without       
difficulty and the trials will be       
resumed ,friday40   ,on ,august #aj1 he 
made a flight of #hj m41 but the motor  
was not in  perfect order1 so ,blriot   
did not make other trials4 ,he decided1 

however1 to substitute definitely a #ej 
,,hp4 motor for the #bd ,,hp4  motor    
with which he made all the experiments  
above reported1 which  were of a        
character to encourage the most sanguine
 expectations4   ,ferber advised ,blriot
 to adopt an elevating rudder also1     
because  the effect produced by changing
 the position of the center of  gravity1
 although efficacious is very difficult 
and delicate to  control4   ,the        
conclusion of an article by ,ferber in  
8,nature0 of ,august #aj1 is  worthy of 
note4 ,he says3 8,let us remark1 in     
conclusion1 how fruitful  is the method 
of personal trial which we have always  
advised in  preference to any           
calculation4 ,this year1 with his fourth
 apparatus1  ,blriot has not met with   
any damage to his aeroplane4 ,he made   
the  trials himself and they quickly led
 to results1 because each trial  gave   
him an exact idea of what was to be     
corrected4 ,that is the  condition of   
success40   p#bhe    ,,appendix  ,,study

 ,,of ,,the ,,american ,,buzzard ,,and  
,,the 8,,john ,,crow0  ,in the          
preparation of this ,memoir1 the writer 
has deemed it best to generally omit any
 mention of plans and ideas which were  
brought forth in the work1 unless       
constructions or tests in accordance    
with them were carried to a sufficient  
extent to admit of some definite        
conclusion regarding them4 ,however1    
owing to the important part played by   
the warping of the supporting surfaces1 
or the variation in the angle of        
auxiliary surfaces1 in the methods of   
preserving the equilibrium of           
practically all flying machines of the  
present day1 it may be of interest to   
here add a short mention of the         
direction in which plans along this line
 were originally proposed in this work4 
,mention has already been made of the   
importance which ,mr4 ,langley attached 
to the study of the works of the great  
master-builder1 ,nature1 though         
recognizing at the same time that owing 

both to the difference in the forces and
 methods of construction possible to    
man1 it was not in general possible for 
him to produce the best results by      
attempting to too closely imitate the   
methods or plans of ,nature4  ,mr4      
,langley considered it not practicable  
or best to attempt to imitate the       
details of construction of the flying   
mechanism of birds4 ,at the same time1  
he strongly believed that much was to be
 learned from them about the practical  
side of the art of balancing1 and he    
therefore spent a great deal of time    
both in analyzing the methods practiced 
by the birds in preserving their        
equilibrium and in criticizing his own  
plans in this direction in the light of 
what ,nature would seem likely to do if 
she had to construct a flying creature  
on such a large scale4 ,in carrying on  
his investigations in the art as        
practiced by the birds1 he made a trip  
to ,jamaica during the early weeks of   
#aijj1 in order to study the species of 

buzzard which are so numerous and tame  
there and are known locally as the      
8,john ,crow40 ,after his return from   
this trip he wrote the following very   
interesting letter to ,mr4 ,robert      
,ridgway1 requesting certain data       
regarding the ,american buzzard1 which  
he wished to compare with some data on  
the 8,john ,crow0 which he had obtained 
on this trip3   ,,march #bi1 #aijj4     
,,dear ,,mr4 ,,ridgway3   ,i have just  
returned from ,jamaica1 where among     
other occupations1  ,i have been        
studying the evolutions of the buzzard  
locally called  the 8,john ,crow10 a    
soaring bird which is almost as much    
superior in  skill to our buzzard as    
that is to a barn-yard fowl in its power
 of  keeping itself in the air without  
flapping its wings1 in what is  very    
nearly a calm4   ,i have observed       
particularly the following points with  
the ,jamaica  specimen 7which ,i can    
only give1 however1 approximately71 and 
,i  should like to have you give        

corresponding ones for our ,washington  
buzzard if you can oblige me4 p#bhf   ,i
 note here that the measurements were   
made on a live bird and that  it was    
impracticable to get the separate weight
 of the wings except  by estimate1 but  
the two wings may be estimated          
collectively as  #a-a_/d lbs41 the whole
 weight being #b-c_/d lbs4 to #c lbs4   
,approximate values3     ,weight of the 
bird complete1 #c pounds4    ,length of 
bird1 #bc inches4    ,spread of wings   
from tip to tip1 #e ft4 #e in4          
,complete curtate area of both wings    
7that is1 the area of the shadow  of the
 bird's wings when these are fully      
extended under a vertical  sun7 is #fjj 
square inches1 or nearly #d sq4 ft41    
consequently each  square foot of the   
bird's sustaining surface carries #c_/d 
lbs4  ,diedral angle nearly #aej4  ,when
 the bird is soaring in a nearly calm   
atmosphere1 which it inexplicably       
does1--soaring ,i mean nearly in line of
 the observer's eyes and coming directly

 to of going directly away from him1--it
 presents nearly the following          
appearance3  ,illustration3 ,,fig4      
#a--;,jamaica1 ,mch4 #bb1 #aijj4 8,john 
,crow40 ,sketch soaring horizontally1 by
 ,w4 ,h4 ,holmes4 ,weight #c lbs4 ,total
 wings area  #edf in4 ,perpendicular    
distance c below a b  #c4c in4          
7#edf7_/g  ,,cp#b;,,cg#b4               
,illustration3 ,,fig4 #b--;,another4    
,,cp#b;,,cg#b  #c4c in4  7#edf7_/g4     
,,figs4 #a and #b4--,type sketches of   
wings by ,holmes from a mean of         
positions taken from his own sketches   
and photographs1 and also from  sketches
 and photographs by ,langley4           
,illustration3 ,,fig4 #c4--,type sketch 
of same birds1 average type1 position of
 wings4--,s4 ,p4 ,langley               
,,cp#b;,,cg#bc4f in4  7#edf7_/f4e4      
,illustration3 ,,fig4 #d4--;,average    
typical position of wings in soaring    
gull4 ,from memory by ,s4 ,p4 ,langley4 
7,the scale here may be taken           
approximately at #a_/ac74   p#bhg  ,i   

must preface what follows by a little   
statement of the things which           
particularly interest me here and which 
are not a naturalist's ordinary concern4
  ,first1 ,i want to know the ,,cg of   
the bird when in flight4 ,you will      
understand that though there is but one 
center of gravity 7here symbolized as   
,,cg71 it may be considered 7#a7 with   
reference to its position on the        
horizontal plan of the bird with wings  
extended1 when it will always be found  
somewhere in the medial vertical plane1 
passing through the body1 and usually   
nearly at a certain point with reference
 to length1 the position thus considered
 being called ,,cg1 or 7#b7 the position
 of the same ,,cg with reference to a   
vertical plane passing transversely     
through the medial line1 the position   
thus considered being called ,,cg#b4 ,in
 the latter case you will understand    
that the ,,cg which is that of the whole
 body1 wings and all1 will be carried   
more or less upward when the wings are  

thrown high up1 and will be carried     
temporarily downward when the wings are 
at their lowest point of the stroke4 ,it
 would have a certain position when the 
bird was at rest and another position   
when it was soaring and the wings were  
above the body4  ,the soaring bird is   
chiefly held upward by the pressure of  
the air under each wing1 and just as the
 common center of gravity is a point    
where all the efforts of gravity are    
supposed to be centered1 so there is a  
common center of pressure1 or one point 
where all the efforts of the upper      
pressure of the air may be supposed to  
be centered1 and it will be clear1 on   
very little consideration that this     
latter point must be always nearly in a 
vertical line through the ,,cg1 and     
usually above it4 ,call it ,,cp4  ,,cg#a
 and ,,cp#a are then1 the symbols of    
,,cg and ,,cp as referred to the        
horizontal plane4 ,,cg#b and ,,cp#b are 
the symbols for the corresponding ones  
when referred to their position in the  

vertical plane4  ,i shall be glad to    
explain to you1 if you are not familiar 
with it1 the simple method of finding   
the ,,cg#a and ,,cg#b4 ,it consists in  
bending the wings into just the position
 that they would ordinarily occupy above
 the body in plain soaring flight1      
keeping them there by a very light bent 
stick or wire1 then hanging the bird up 
by a line attached to the tip of one    
wing1 and see where this line would pass
 through the body of the bird1 for the  
,,cg will be somewhere in this line4    
,after marking then1 on the body of the 
bird its position1 hang it up a second  
time by the head or tail and note again 
where the new vertical line runs in the 
new position4 ,there is but one ,,cg and
 but one point in which two straight    
lines can cross1 and that will be the   
,,cg necessarily4 ,note with all care   
just where this is above or below the   
center of the body of the bird4  ,as for
 the ,,cp for either wing1 that may be  
nearly found by tracing the wing on a   

flat piece of thick paper or cardboard  
strong enough not to bend much--cutting 
out the tracing and balancing it well on
 the point of a pencil--the point about 
which it balances is very near ,,cp#b or
 the center of pressure in the vertical 
plane4 ,there is such a point of course 
in each wing1 and when they are thrown  
up in the actual position that they have
 in calm soaring flight1 we may suppose 
a horizontal line drawn between them1   
and it is the distance from this        
horizontal line to ,,cg#b compared with 
the area of the wings or with the       
distance between their extended tips    
which we want to know1 which gives the  
vertical distance which the ,,cg is     
below the ,,cp1 the thing we want to    
know4  ,it will be very convenient also 
to have a wing dissected from the body  
and the wing itself held in about the   
soaring curve by a bit of light stick   
balanced on a pencil point1 which will  
give the ,,cg of the wing as distinct   
from that of the body4 ,however1 the    

three things ,i principally want1 beside
 a sketch or p#bhh photograph of the    
bird from about its own level coming    
directly toward or going directly away  
in soaring flight1 are these3           
,approximate weight of the bird1--and   
approximate tracing of its extended wing
 with the area1 so that we can tell the 
area of the supporting surface relative 
to the weight1 and finally1 the distance
 between ,,cp#b1 and ,,cg#b1 which is   
obtainable by the process which ,i have 
explained4  ,i am afraid that what ,i   
have just been describing at such length
 may have a certain obscurity to you1   
but if you will give me an opportunity1 
,i shall be pleased to illustrate it    
with the actual experiment when the bird
 is hung up by a string1 and you will   
see that it is in reality simple4       
,referring to the sketches on page #c of
 this communication1 a and b correspond 
to the centers of pressure on either    
wing where the upward pressure of the   
air distributed over each wing may be   

supposed to be gathered in a single     
point4 ,this1 as ,i have said1 is called
 the center of pressure with reference  
to the vertical flight1 and its symbol  
is ,,cp#b1 while the horizontal dotted  
line between them represents the level  
of ,,cp#b1 from the best estimate that  
,i could make when the wings are in     
their natural position of soaring4 ,it  
is evident that this line passed far    
above the body of the vulture1 and if   
7the corresponding symbol for the height
 of the center of gravity being ,,cg#b71
 the ,,cg#b1 of the entire bird be      
taken1 it will be found to lie nearly in
 the point c4 ,where c is in the present
 case1 ,i could not determine exactly in
 my hasty examinations in the live bird1
 but ,i assume that it is about #a_/b   
way between the central horizontal axial
 line of the bird's body and the upper  
portion4 ,i repeat that it is important 
to me to know what the vertical distance
 is between ,,cp#b and ,,cg#b in each   
specimen of soaring bird4 ,i may observe

 in illustration that in the common     
sea-gull1 it is nearly as shown in the  
faint sketch2 that is to say1 that the  
corresponding line a b in the soaring   
gull passes distinctly through the upper
 part of the body1 and the distance down
 to the ,,cg#b of the whole in the gull 
is almost nil1 while in the buzzard it  
is very considerable as shown by the    
corresponding distance in the 8,john    
,crow40  ,now1 what ,i want to get from 
you is the corresponding figures for an 
average specimen of our ,washington     
buzzard4 ,if you will kindly have one   
killed and weighed while fresh1 and     
before the rigor-mortis has set in1     
first noting the position of its wings  
when soaring in a calm1 and 7if         
possible7 when coming toward you or     
going away in about a horizontal plane  
with your eye1 in which position the    
wings will be elevated and bent somewhat
 as in the case of the above sketch of  
the 8,john ,crow02 if you will kindly do
 this1 so as to give me corresponding   

facts with reference to the buzzard1    
namely weight1 area of extended wing    
surface1 distance between tips as bent  
up in ordinary flight1 distance between 
extended tips1 the quantity             
,,cp#b;,,cg#b1 and also will make such a
 tracing of the buzzard's wing as ,mr4  
,manly will show you of the 8,john      
,crow's10 ,i shall be obliged4  ,my     
impression is that the buzzard is a     
considerably heavier bird than the      
8,john ,crow10 without1 however1 very   
much greater spread of wing4 ,i may     
observe that when the wings of the      
,jamaica bird were spread out1 they were
 spread quite to their utmost extent1   
and the distance between the tips of the
 terminal feathers was much greater than
 when in flight4 ,i wish you would      
kindly also add the scientific name of  
the 8,john ,crow10 with any particulars 
that you would think of interest4  ,if  
there be any special expenses incurred  
in the preparation of this memorandum1  
including the time of a photographer1 ,i

 will direct them to be paid from the   
,smithsonian fund4 p#bhi  ,if you could 
get ,mr4 ,holmes 7who made most of the  
sketches and all of the photographs of  
the 8,john ,crow071 to try and do       
something like this for your buzzard1   
especially getting such a photograph of 
it in flight1 as will give the position 
of its center of gravity relative to the
 center of pressure on the wings1 it    
would add very greatly to the value of  
your memoranda1 and ,i think ,mr4       
,holmes takes so full and intelligent an
 interest in the subject1 that he might 
be pleased to give his help4   ,very    
truly yours1  ,s4 ,p4 ,,langley1        
,secretary4   ,,mr4 ,,robert ,,ridgway1 
,smithsonian ,institution1  ,curator1   
,division of ,ornithology1 ,u4 ,s4      
,national ,museum1 ,washington1  ,d4 ,c4
   ,in response to this request1 ,mr4   
,ridgway submitted the following very   
interesting information3   ,,smithsonian
 ,,institution1  ,,united ,,states      
,,national ,,museum   ,,washington1 ,d4 

,c41 ,october #af1 #aijj4   ,,prof4 ,s4 
,p4 ,,langley1  ,secretary1 ,smithsonian
 ,institution4   ,,sir3   ,i have the   
honor of submitting herewith the data   
obtained by ,mr4  ,rolla ,p4 ,currie    
concerning measurements1 etc41 of the   
common ,turkey  ,buzzard 7,cathartes    
aura7 of the ,united ,states1 as        
requested by you  in your letter of     
,march #bi1 last4   ,the difficulties in
 the way of securing these data1 already
  explained by me in previous           
communications1 are responsible for the 
delay in submitting them4   ,hoping that
 this material may prove of use to you1 
,i am1   ,very respectfully1  ,r4       
,,ridgway1  ,curator1 ,division of      
,birds4    ,,memoranda ,,in ,,regard    
,,to ,,the ,,turkey ,,buzzard 7,,second 
,,specimen7   #a4 ,weight4--#ahej       
grammes4   #b4 ,area of outstretched    
wings4--#fda square inches4 7,computed  
from  three sheets of tracings1 ,a#a and
 ,a#b comprising the entire area  of    
both wings2 ,b1 a single wing47         

,note4--,as the bird was in process of  
moult1 one of the large wing  quills1 as
 shown by the tracings and compo-board  
patterns1 is but  partially developed1  
thus slightly modifying the results     
obtained4  ,its length1 if full grown1  
would be nearly the same as that of the 
quill just above it4   #c4 ,distance    
between the tips of these wings4--#e    
feet1 #h4g inches4   #d4 ,distance      
between the tips of the same wings when 
the bird is in  horizontal soaring      
flight4--,estimating the dihedral angle 
of the  wings to be #aej1 and elevating 
the wings so as to make this angle1  the
 distance between their tips p#bij      
measures #e feet1 #e4g inches1  or #c   
inches less than when fully extended in 
the horizontal plane4   #e4 ,the        
position of the center of pressure of   
the wing4--,this is  indicated on two   
compo-board patterns1 ,c and ,d4 ,c was 
made  from a fully extended wing1 while 
,d was made from the wing in the        
soaring position4 ,the centers of       

pressure of the wings are about  #b     
feet1 #j4e inches apart1 or #a foot1    
#j4be inches from the central  point of 
the bird's body4   #f4 ,the position of 
the center of gravity of the soaring    
bird4--7,length of buzzard1 #bf inches47
 ,the center of gravity of  the soaring 
buzzard in the horizontal plane1 ,,cg#a1
 was found to lie  #i-a_/b inches behind
 the tip of the beak and #af-a_/b inches
 in front  of the tip of the tail4      
,the center of gravity of the soaring   
bird in the vertical plane1  ,,cg#b1 was
 found to lie #b4h inches above the     
ventral point of the  body and #a4f     
inches below the dorsal point1 the depth
 of the bird's  body at ,,cg#a1 being   
#d4d inches4   ,in determining the      
center of gravity1 the bird was frozen  
in the  soaring position1 its wings     
making a dihedral angle of #aej4 ,it    
was then hung up1 first horizontally and
 then vertically1 and  balanced till the
 line from which it was suspended       
coincided with a  plumb-line placed in  

front of it2 the measurements were then 
made4   ,the bird was afterwards1 and   
while still frozen1 hung up in the same 
way in ,mr4 ,smillie's photographic     
room1 and exposures made by him  in both
 positions4 ,these photographs1 ,e#a and
 ,f#a were enlarged  to natural size1   
and measurements made on the            
enlargements yielded1  as nearly as     
could be determined1 the same results as
 when taken  directly upon the bird4    
,as determined by measurements upon the 
buzzard in soaring position1  the center
 of gravity was found to be #b4fe inches
 below the center  of pressure          
7estimating the center of pressure to be
 at the bend of  the wing72 or1         
employing the compo-board pattern in a  
corresponding  position1 the distance   
was seen to be a small fraction of an   
inch  less4   #g4 ,the position of the  
root of the wing4--,this is indicated on
 the  tracing ,a#a4   a4 7,depth of the 
body on a vertical line with root1 #c4e 
inches47  ,the root lies #a4f inches    

below dorsal line1 #a4i inches above    
ventral  line4   b4 7,length of body1   
#bf inches47 ,the root lies #g4f inches 
behind  tip of beak1 #ah4d inches in    
front of tip of tail4   #h4 ,the        
dihedral angle between the wings4--,the 
photographs taken  previously were not  
sufficiently large or distinct to enable
 us to  determine this with exactness4  
,it was estimated1 however1 as #aej1    
and experiments were made on this basis4
   #i4 ,the center of gravity of the    
dissected wing4--,this was found1       
first1 for the wing having all the      
muscles1 up to the ball and  socket     
joint1 intact4 ,one of the wings was    
frozen in the soaring  position and its 
center of gravity found by balancing on 
a point4  ,its position was marked by a 
wire thrust through the wing at this    
place1 and the wing 7,h7 is preserved in
 formalin4 ,this position  is also      
marked on a special tracing1 ,i4 ,it    
lies #f inches from the  base of the    
humerus bone 7root of wing74 ,secondly1 

it was found  for the wing denuded of   
all muscle4 ,its position was marked on 
the other wing of the bird1 which is    
preserved dry1 spread in the  soaring   
position4 ,it lies #i-c_/d inches from  
the base of the humerus4  p#bia   #aj4  
,the weight of the dissected wing4--    
a4 ,with all muscle up to the ball and  
socket joint intact1 #cbe  grammes4   b4
 ,with all muscle removed1 #aij grammes4
   ,weight of muscle1 therefore1 #ace   
grammes4   ,the position of the root of 
the tail4--   a4 ,in the horizontal     
plane1 #aa4h inches in front of the tip 
of the  longest tail feather2 #ad4b     
inches behind tip of beak4   b4 ,in the 
vertical plane3 7depth of body from     
ventral point below  root of tail to a  
point directly above1 which is on a     
level with the  highest point of the    
back1 #b4e inches47 #a4e inches above   
ventral  point1 #a inch below dorsal    
point4   ,weight of tail4--,with muscle1
 #dj grammes2 without muscle1 #cj       
grammes4 ,weight of muscle1 therefore1  

#aj grammes4    ,,exhibits              
,,accompanying ,,these ,,memoranda      
,illustration3 ,,exhibit ,e#a4--,turkey 
,buzzard suspended in soaring  position4
 7,r4 ,p4 ,currie47   ,a#a and ,a#b4    
,two sheets1 comprising a tracing of the
 entire  turkey buzzard with fully      
outstretched wings4 ,from these the area
  of the wings and the distance between 
their tips was obtained4 ,the  position 
of the root of the wing and the root of 
the tail is also  marked on one of these
 sheets4   ,b4 ,one sheet1 comprising a 
tracing of a single wing1 and from      
which the area was also computed4 ,this 
area1 multiplied by #b1  gives the same 
result as the sum of both wings on ,a#a 
and ,a#b4 ,the  compo-board pattern ,c  
was made from this tracing4   ,c4       
,compo-board pattern of fully extended  
wing1 on which the center  of pressure  
is indicated4   ,d4 ,compo-board pattern
 of wing in soaring position1 on which  
the  center of pressure is shown4 p#bib 
,e#a4 ,photograph of bird in soaring    

position1 suspended  horizontally4      
,e#b4 ,same1 enlarged to natural size4  
,f#a4 ,photograph of bird in soaring    
position1 suspended vertically4   ,f#b4 
,same1 enlarged to natural size4   ,g4  
,tracing of wing in soaring position1   
from which the compo-board  pattern ,d  
was made4   ,illustration3 ,,exhibit    
,f#a4--,turkey ,buzzard suspended       
vertically in  soaring position4 7,r4   
,p4 ,currie47   ,h4 ,wing preserved in  
formalin1 on which the center of gravity
 is  recorded4   ,i4 ,tracing of wing ,h
 when frozen in soaring position1 on    
which  the center of gravity is marked4 
,j4 ,wing with muscle removed1 on which 
the center of gravity is  shown4        
,several persons connected with the     
,smithsonian ,institution and ,u4  ,s4  
,national ,museum have contributed      
towards securing the results  herewith  
submitted4 ,among them1 ,i desire       
especially to mention ,mr4  ,w4 ,h4     
,holmes1 ,mr4 p#bic ,f4 ,a4 ,lucas1 ,mr4
 ,n4 ,r4 ,wood1 and ,mr4 ,r4  ,l4 ,reed4

 ,mr4 ,holmes superintended the         
experiments in connection  with ,no4 #f 
7finding the bird's center of gravity71 
and by his  suggestions and criticisms  
helped me in many other particulars4    
,the  photographs and enlargements were 
made by ,mr4 ,t4 ,w4 ,smillie4          
,respectfully submitted1  ,,rolla ,p4   
,,currie1  ,aid1 ,division of ,insects1 
acting in the ,division of ,birds4      
,,october #af1 #aijj4   ,the feats of   
airmanship performed by the 8,john      
,crow0 seemed to greatly impress ,mr4   
,langley and shortly after this trip he 
wrote the following letter to the       
writer3    ,,smithsonian ,,institution  
,,washington1 ,d4 ,c41 ,april #af1      
#aijj4   ,,dear ,,mr4 ,,manly3   ,i am  
reminded of the consequence that ,i     
have1 in connection with  ,mr4 ,chanute 
and perhaps ,mr4 ,huffaker1 attached in 
the past to the  possibility of         
directing the bird1 and consequently the
 flying  machine1 by the mere inflection
 of the wing1 that is1 by changing  its 

angle2 and you recall to me that ,mr4   
,huffaker at one time  proposed to      
arrange a wing1 with some provision of a
 spring1 which  should enable it to     
change its angle automatically4 4 4 4 4 
,i have been noting this ability to     
guide by the slight inflection  of the  
wing1 in my studies of the ,jamaica     
buzzard1 and am ready  to say that ,i   
think1 while the quarter-sized working  
model of the  great aerodrome is        
building1 it will be worth while to make
 some  arrangement of the frame or      
wing-holder which will make it possible 
to test this idea4 ,i will endeavor to  
work out something of the  kind more in 
detail myself1 but whatever it is1 it   
will apparently  involve the ability of 
the wing to rotate about a line passing 
nearly through it lengthwise1 and an    
allowance for this2 if not in  the wing 
itself1 then in the wing-holder2 will   
need to be made while  the present model
 is under construction4   ,i will       
request you to especially look out for  

this1 as far as you  can on these       
indications4   ,very respectfully yours1
  ,s4 ,p4 ,,langley1  ,secretary4   ,the
 instructions and suggestions contained 
in this letter and in many conferences  
on the subject were never carried out by
 the writer1 on account of the extreme  
pressure of the work already on him     
which had for its object1 not the       
production of a flying machine which    
would embody all of the control which we
 wished it to have1 but which would be  
burdened only with such devices and     
arrangements as would enable it to      
transport a human being1 and thus       
demonstrate the practicability of human 
flight4   p#bid    ,,secretary          
,,langley',s ,,instructions ,,to        
,,assistants   ,,smithsonian            
,,institution1 ,,washington1 ,d4 ,c41   
,november #cj1 #ahie4   ,,dear ,,sir3   
,the following instructions are to      
replace those of ,may #ac1 #ahie3   #a4 
,the minimum fraction of its own 8flying
 weight0 7that is1  weight complete with

 initial water and fuel71 which the     
aerodrome  shall lift on the pendulum1  
is #ej percent1#ej under such engine    
power as can certainly be gotten up in  
the field and maintained  during forty  
seconds from the time the aerodrome is  
let go4   ,the blast1 the pumps1 and all
 other essential parts must1 in other   
words1 be in such a condition that steam
 enough for this lifting  over #ej per  
cent of weight can be gotten up readily 
and surely  in the field and in a time  
which will still leave at least forty   
seconds' supply4   #b4 ,the minimum     
relation of supporting area to weight in
 any  aerodrome constructed hereafter1  
is to be two feet to the pound1#ej  and 
the minimum of power at the rate of one 
steadily-maintained  horse power#ej at  
the brake under ordinary conditions1 to 
not over  twenty-two pounds 7ten kilos7 
of flying weight4 ,in absence of a      
brake determination horse power may be  
taken--   ,h4 ,p4  7revs4 per min4 at   
rest  pitch           diameter 7in ft47 

thrust 7in lbs477 _/ #cc1jjj4   ,these  
rules do not apply to ,no4 #e1 but they 
do to ,no4 #f1 which is to  be built    
over1 if necessary1 to meet them4   #c4 
,in balancing an aerodrome1 unless      
otherwise instructed1 set wings  at a   
root angle of either #aj1 #g1 or #e1    
after being certain from  previous      
inversion and sanding1 that the tip     
angle in motion will  not differ from   
this root angle as much as #e4   ,the   
object in balancing any aerodrome with a
 single pair of wings  is to be able to 
bring the c g#b under their c p#b       
without any  reference to the tail1     
which supports nothing1 unless specially
  ordered4 ,but as this condition cannot
 now be obtained in ,nos4 #e  and #f1   
these at any rate1 and perhaps future   
aerodromes1 are to  carry a second pair 
of wings4 ,when this second pair of     
wings is of  nearly equal size with the 
first it is to be assumed in preliminary
  adjustments for weight and center of  
pressure1 that the second pair  has     

two-thirds the lifting efficiency per   
unit area of the first4   ,calling the  
whole distance from the mean center of  
pressure of  the wings to the center of 
gravity ,m4 ,m is to have a definite    
relation to the breadth of p#bie wings  
from tip to tip 7b7 and  total fore and 
aft length 7#a71 which is provisionally 
fixed at ,m   7bl7_/#h1 and the line of 
thrust is to be not over one-fourth the 
way  from c p#b to c g#b4   ,generally  
speaking the front pair of wings will be
 fixed in position  and the adjustment  
for balancing made by moving the rear   
pair4   ,the individual weights of all  
parts checked by lump weighing are  to  
be given by the caretaker 7,mr4         
,huffaker71 under the general  scheme   
shown in the note4 ,the work on the     
aerodromes being divided  into two      
classes1 viz43 metal work and all which 
is not metal1 the  two in charge of this
 work 7,mr4 ,reed and ,mr4 ,maltby7 are 
severally  responsible for knowing the  
weight in grammes of any of the parts   

they have put into their work1 giving   
these weights to ,mr4 ,huffaker1        
together with any data for filling out  
the annexed tables1#ea on  his request4 
,until further orders1 ,mr4 ,huffaker is
 charged with the  responsibility of    
seeing that these conditions are met    
before  any aerodrome is boxed1 and will
 keep the record of weights of  the     
aerodromes and their principal parts as 
already completed1  in a book1 to be    
preserved in your keeping1 which will   
also be  arranged to show with signed   
photographs and descriptions1 and  with 
sketches where needed1 the condition and
 weight 7as far as  constructed7 of     
every aerodrome1 and of any new         
construction of any  part1 on the first 
of each month4   ,particular attention  
is directed to the preceding paragraph1 
and to  the need that evidence of a     
definite character is to be obtained and
  preserved of everything already done1 
and being done4   ,without special      
orders to the contrary1 you will not    

authorize the  boxing of any aerodrome  
which does not1 to your knowledge1 meet 
these conditions4   ,each aerodrome is  
to have the following parts in duplicate
 or in  triplicate3   #b pairs wings2   
#b pairs tails2  #b pairs light silk    
covered rudders2  #c pairs wheels2      
with any other parts in duplicate or    
triplicate1 which experience  has shown 
to be necessary4   ,mr4 ,reed will not  
box any aerodrome till a certificate    
from ,mr4  ,huffaker can be put on the  
inside cover1 with the list of contents1
  showing what the conditions are as to 
weight1 wing area1 power1  etc41 and the
 person in the field charged with the   
duty of launching  the aerodrome 7at    
present ,mr4 ,reed71 is authorized not  
to let it go  unless he is satisfied    
that it has a full forty seconds' supply
 of  steam4 p#bif   ,i am satisfied that
 a great deal of time is lost in putting
  the aerodrome together for flight1    
owing to the absence of any  preliminary
 drill in doing this4 ,before it goes   

into the field the  whole is to be      
completely boxed1 and then taken out    
from the box  and set up on the clutch1 
and steam gotten up for flight4 ,all    
this  is to be done in the shop before  
the final boxing1 and provision is  to  
be made so that no wiring or adjusting  
of parts is to be done in  the field    
which can possibly be avoided by        
forethought in the shop4  ,the          
tail-piece1 for instance1 is to be      
bushed with brass1 so that it  will     
always come into the same place1 and    
make a tight fit1 in spite  of wetting  
or shrinking1 in the steel tube1 where  
it is to go into a  guide-way with a    
bayonet spring1 or a like contrivance   
for setting  it at once securely into   
position4   ,the mean positions of the  
wings and tail are to be laid out  in   
some way permanently on the mid-rod1 but
 every guy-rod or  adjustable piece is  
to be arranged so as to fit at once     
securely and  permanently in its        
position without wiring or like slow    

process4   ,very truly yours1  ,s4 ,p4  
,,langley1  ,secretary4   ,w4 ,c4       
,,winlock1 ,esq41  ,assistant in        
,charge1  ,smithsonian ,institution4    
,a copy to be communicated to3--   ,mr4 
,huffaker1   ,mr4 ,reed1   ,mr4 ,maltby4
    ,,footnotes4  #cg 8,the ,flying     
,machine0 ,mc,clure's ,magazine1 ,june1 
#ahig4  #ch ,one noted astronomer and   
mathematician re-affirmed this opinion  
as late as #aijj and even stated that   
man could not hope to construct a flying
 machine capable of sustaining a weight 
as great as our largest birds1 knowing  
that even at that time the model        
,aerodromes ,nos4 #e and #f had already 
done more than this4  #ci ,these wings  
are described in ,chapter ,,vi1 pp4     
#aia4  #dj ,see 8,experiments in        
,aerodynamics40 ,it will be recalled    
that in the experiments with the        
8plane-dropper0 there was a greatly     
reduced lifting power with superposed   
planes when their distance apart was    
one-half the width the planes1 unless a 

speed of about #db4e feet a second was  
obtained4 ,in the above tests with the  
superposed wings1 the speed was only    
from twenty to twenty-two feet a second 
at the time of launching1 and as the    
distance between the surfaces was only  
one-half as great as their width1 it is 
not surprising that the lifting power   
should not be as great as with the      
8single-tier0 wings4  #da ,in fact the  
setting of the tail at a negative angle 
and fastening it to the frame by an     
elastic or spring connection was only   
begun in #ahif1 and while it proved to  
be the key to the solution of the       
problem of automatic longitudinal       
stability1 yet it was not at that time  
so recognized1 although the first real  
test of the aerodromes after the elastic
 connection and negative angle of the   
tail were adopted resulted in the       
epoch-making flight of ,no4 #e on ,may  
#f4 ,by comparing the angle of the tail 
on ,no4 #e in ,plate #bg;,a1 ,part ,i1  
with the angle of the tail on ,no4 #f in

 ,plate #bg;,b1 ,part ,i1 it will be    
seen that while the first had an angle  
of much less than #e degrees1 the latter
 had an angle of about #ae degrees4 ,but
 the wooden springs changed so that it  
was not accurately known what the angle 
really was at the time at either flight 
in #ahif4  #db ,the drawings1 ,plate    
#ee1 which illustrate many of the       
fittings used on the frame1 show the    
guy-wires as attached by means of loops 
twisted in their ends1 these drawings   
having been made before the final plan  
of attaching the wires had been devised4
  #dc ,see explanation of system of     
locating points in ,part ,i1 ,chap4     
,,ii1 p4 #ae4  #dd ,see ,balancing of   
,engines1 by ,archibald ,sharpe4  #de   
,except for a ten minute stop to renew  
the supply of lubricating oil and change
 the sparking batteries4  #df ,see      
foot-note1 page #bdi4  #dg ,the weight  
was afterwards increased to #hej pounds 
due to repairing the wings and adding   
more sparking batteries4  #dh ,see      

,experiments in ,aerodynamics1          
,smithsonian ,contributions to          
,knowledge1 ,vol4 #bg1 ,washington      
#ahia4  #di ,researches and ,experiments
 in ,aerial ,navigation1 ,smithsonian   
,publication ,no4 #ahji1 ,washington1   
#aijh4  #ej ,all these minimum          
permissible conditions are connected by 
the tacit assumption that the supporting
 area is not greatly over #b ft4 to the 
pound of weight4 ,if for instance the   
weight were increased by larger wings or
 more wings1 furnishing a much greater  
supporting area per pound1 these        
conditions would not necessarily apply4 
#ea ,these tables were later designated 
as 8,data ,sheets40 ,several copies1    
with the data duly entered on them1 are 
given in this appendix1 and the form    
which ,mr4 ,langley included in this    
letter is therefore not repeated        
here4--,,editor4   p#big    ,,data      
,,sheets4   ,,data ,,sheet ,no4 #a4     
,weight of ,aerodrome ,no4 #e1 as       
photographed on ,may #aa1 #ahif4        

,certified to by ,r4 ,l4 ,reed1 ,may #f1
 #ahif4                                 
----------------------------------------
----------------------  ,parts4         
,sizes4     ,weight4                    
----------------------------------------
--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     
everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for clutch1 etc4                        
#bddc                                   
#b ,engine1 gears1 shafts1 etc4         
#aaaj                                   
#c ,pump1 pump shaft                    
#bca                                    
#d ,hull covering                       
#cej                                    
#e ,gasoline tanks1 valves              
#agh                                    
#f ,smokestack                          
#cdb                                    
#g ,float                               

#bge                                    
#h ,reel                                
#gg                                     
#i ,wing clamps1 #bce2 clamp for        
guy-posts1 #bi                          
#bfd                                    
#aj ,other things1 counter              
#ge                                     
#aa ,burners                            
#cfj                                    
#ab ,boilers                            
#fea                                    
#ac ,separators1 steam gauge1 pipe to   
engine                                  
#edj                                    
#ad ,exhaust pipe                       
#adc                                    
#ae                                     
#af                                     
#ag ,wings 7without clamp7              
#aiej                                   
#ah ,tail 7without clamp7               
#ai ,rudder                             
#cej                                    
#bj ,guy sticks1 each1 #eg              

#aad                                    
#ba ,propellers                         
#hjj                                    
#bb ,extra length of midrod1 #cjh2 drop 
piece for rudder1 #dj                   
#cdh                                    
#bc ,wood ,bowsprit                     
#gd                                     
#bd ,other things                       
#be                                     
#bf                                     
#bg ,fuel 7at starting flight7          
#bjj                                    
#bh ,water 7at starting flight7         
#ijj                                    
#bi                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#aa1gge  #bf                            
#ce                                     
#cf                                     
#cg                                     

#ch ,total area of support 7not         
including tail7 sq4 ft4                 
#fh                                     
#ci ,total area of support in feet1     
divided by total flying weight in lbs4  
#b4f                                    
#dj ,total area of horizontal tail sq4  
ft4                                     
#da ,total area of rudder 7vertical7    
sq4 ft4                                 
#f                                      
#db ,horse-power at brake4 ,horse-power 
by formula99 4#gb                       
#g                                      
#dc ,minimum pressure during #dj secs4  
lift1 #aej lbs4                         
#dd ,lift at pendulum 7during #dj secs4 
absolute7 #eggb                         
#de ,lift at pendulum 7during #dj secs4 
in terms of wt47 #di                    
#df ,minimum pressure with which wheels 
turn1 #aj lbs4                          
#dg ,position of center of pressure of  
wings ,f4 ,w41 #aege2 ,r4 ,w41 #achc4e  
#dh ,time of getting up full steam1 #a  

minute                                  
#di                                     
#ej ,curvature of wings1 #a_/aa         
#ea ,root angle of wings1 #i            
#eb ,tip angle of wings1 #i             
#ec ,position of wings1 ,front rib on   
,f4                         ,w41 #afjg2 
,r4 ,w41 #adae4e                        
#ed ,how guyed                          
#ee                                     
#ef                                     
#eg                                     
#eh ,position of tail                   
#ei ,angle of tail                      
#fj ,co-efficient elasticity of tail    
#fa ,position of rudder1 center1        
#abhh4c2 rear end1 #abbi4h              
#fb ,line of thrust1 #bejj              
#fc ,line of thrust1 #aejj which is #i  
cm4 below the center of midrod          
#fd ,center of gravity#a of whole1 #adig
                                        
#fe ,center of gravity#b #beja1 i4 e41  
#a                         cm4 above    
line of thrust                          

#ff ,center of pressure#a of whole      
estimate1 #adih                         
#fg ,center of pressure#b1 #becf        
#fh                                     
#fi                                     
#gj                                     
#ga                                     
#gb                                     
----------------------------------------
--------------------   ,parts4 ,remarks4
   #a ,front end of bowsprit1 #afhf4c4  
#b ,front end of midrod1 #afaa4f4   #e  
,front edge of ,f4 ,w41 #afjg4   #h ,c4 
of ,p4 on ,f4 ,w41 #aege4   #aa ,back   
edge of ,f4 ,w41 #aebg4   #ad ,back edge
 of cross frame1 #aeji4   #ag ,line     
through center of propellers1 #aejj4    
#ba ,c4 of ,g41 #adig4   #bd ,front edge
 of ,r4 ,w41 #adae4e4   #bg ,c4 of ,p4  
on ,r4 ,w41 #achc4e4   #cj ,end of      
mid-rod1 #acfj4e4   #cc ,front end of   
rudder1 #acdc4h4   #cf ,back edge of ,r4
 ,w41 #acce4e4   #ci ,center of rudder1 
#abhh4c4   #da ,back end of rudder1     
#abbi4h4  99 ,h4 ,p4  7,rev4diam4pitch  

ratiothrust7_/#ccjjj   ,this is         
calculated on the assumption that the   
center of pressure on each wing or on   
pair of wings at a motion of #bjjj feet 
per minute is in ordinary curved wings  
#b-e the way from front to rear1 that   
for wings of usual size the rear wings  
have #b-c of the efficiency per surface 
of the front ones and that the tail     
proper bears no part of the weight2 but 
if rear wing is smaller or larger this  
efficiency is smaller or larger per unit
 of surface4   p#bih    ,,data ,,sheet  
,no4 #b4   ,weight of ,aerodrome ,no4   
#f4  ,certified to by ,r4 ,l4 ,reed1    
,november #bg and #bh1 #ahif4           
----------------------------------------
---------------------------  ,parts4    
,sizes4      ,weight4                   
----------------------------------------
-------------------------               
m4 ft4gr4 lbs4  #a ,frame1 including    
everything of metal1                    
permanent and undetachable1 such as bed-
                           plate1       

cross-rods for the support of           
propellers1 bearing points for clutch1  
etc4                                    
#aagh        #b ,engine1 gears1 shafts1 
etc4                          #ajdc     
#c ,pump1 pump shaft                    
#aij        #d ,hull covering           
#cde        #e ,gasoline tanks1 valves  
#cjf        #f ,smokestack1 #cjb2       
burner1 #agb                            
#dgd        #g ,float                   
#bge        #h ,reel                    
#gg        #i ,wing clamps1 #bch2 drop  
piece for rudder1              #bgh     
#dj                                     
#aj ,other things                       
#aef        #aa ,boiler1 frames1 mica   
cover                           #fid    
#ab ,separator1 steam gauge1 pipe to    
engines              #ece        #ac    
,exhaust pipe                           
#hb        #ad                          
#ae                                     
#af                                     
#ag ,wings 7without clamp71 wet         

#baed        #ah ,tail 7without clamp7  
#ai ,rudder                             
#cge        #bj ,guy sticks1 each #ec   
#ajf        #ba ,propellers             
#fdd        #bb ,extra length of midrod 
#cih        #bc ,wood bowsprit          
#ace        #bd ,counter                
#ge        #be                          
#bf                                     
#bg ,fuel 7at starting flight7          
#bej        #bh ,water 7at starting     
flight7                          #bcej  
#bi                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#ab1abj        #ce                      
#cf                                     
#cg                                     
#ch ,total area of support 7not         
including            #ed                
tail7                         sq4 ft4   
#ci ,total area of support in feet1     

divided                               by
 total flying        weight in lbs4     
#b                #dj ,total area of    
horizontal tail    sq4 ft4  4#f         
#da ,total area of rudder 7vertical7    
sq4 ft4  4#f                    #db     
,horse-power at brake  ,horse-power by  
formula99                               
#dc ,minimum steam pressure during #dj  
secs4                     #acj          
lift                                    
#dd ,lift at pendulum 7during one minute
                      #g1baa            
absolute7                               
#de ,lift at pendulum 7during one minute
 in                               terms 
of wt47                                 
#df ,minimum pressure with which wheels 
turn                    #aj   #dg       
,position of center of pressure of wings
                        #dh ,time of    
getting up full steam1 #ge secs4        
#di ,angle of midrod with horizon1 #b   
#ag                            #ej      
,curvature of wings1 #a in #ah1 #a_/d   

from                                    
front                                   
#ea ,root angle of wings1 #aj #cj       
#eb ,tip angle of wings1 #aj #cj        
#ec ,position of wings                  
#ed ,how guyed                          
#ee                                     
#ef                                     
#eg                                     
#eh ,position of tail                   
#ei ,angle of tail                      
#fj ,co-efficient elasticity of tail    
#fa ,position of rudder                 
#fb                                     
#fc ,line of thrust #aejj               
#fd ,center of gravity#a of whole1      
#adhc4h                            #fe  
,center of gravity#b1 #bdhb             
#ff ,center of pressure#a of whole      
estimate1 #adhg                         
#fg ,center of pressure#b1 #bebj        
#fh                                     
#fi                                     
#gj                                     
#ga                                     

#gb                                     
----------------------------------------
-------------------------   ,parts4     
,remarks4   #a ,front end of bowsprit1  
#agig4   #b ,center of float in first   
trial1 ,nov4   #f ,front end of midrod1 
#afac4g4 #i ,front edge of ,f4 ,w41     
#aeie4g4   #ab ,center of float in      
flight1 ,nov4 #bh1 #ahif1 #aege4h4   #af
 ,c4 of ,p4 on ,f4 ,w41 #aefc4g4   #ai  
,back edge of ,f4 ,w41 #aeae4g4   #bb   
,line through center   of propellers1   
#aejj4   #bf ,c4 of ,g41 #adhd4d 7old   
,c4 of ,g41 #adhf4c74   #bi ,front edge 
of ,r4 ,w41 #adjf4   #cb ,c4 of ,p4 on  
,r4 ,w41 #acgd4   #ce ,end of midrod1   
#acea4c   #ch ,front end of rudder1     
#accd4e4   #da ,back edge of ,r4 ,w41   
#acbf4   #dc ,center of rudder1 #abgi4  
#df ,back end of rudder1 #abbj4e4   #di 
,reed wings1 #hj cm4#ahe cm4 in         
rectangle4   #ec ,weight in shop1 #aihb 
g4   #ef ,on day of flight they weighed 
#baed g4 because they were damp4   #fj  
,area #ed sq4 ft4   #fc ,spread of      

wings1 #cei cms4 or #aa #i-c_/h4   #fg  
,weight of aerodrome in flight1 #ab1abj 
grs4  99 ,h4 ,p4  7,rev4diam4pitch      
ratiothrust7_/#ccjjj   ,this is         
calculated on the assumption that the   
center of pressure on each wing or on   
pair of wings at a motion of #bjjj feet 
per minute is in ordinary curved wings  
#b-e the way from front to rear1 that   
for wings of usual size the rear wings  
have #b-c of the efficiency per surface 
of the front ones and that the tail     
proper bears no part of the weight2 but 
if rear wing is smaller or larger this  
efficiency is smaller or larger per unit
 of surface4   ,this is undoubtedly     
incorrect1 as if it were true1 the ,c4  
,g4 would be just at the center of the  
separator1 and this would be impossible4
 ,mr4 ,reed states that the ,c4 ,g4 was 
#b cm4 below the side frame1 and if this
 is correct1 we would have ,c4 ,g4      
#bdhf4   p#bii    ,,data ,,sheet ,no4   
#c4   ,weight of ,aerodrome ,no4 #f1    
,flat ,wings and ,pnaud ,rudder4        

,certified to by ,chas4 ,m4 ,manly1     
,june #g1 #ahii4                        
----------------------------------------
----------------------  ,parts4         
,sizes4     ,weight4                    
----------------------------------------
--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     
everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for clutch1 etc4                        
#bhfg                                   
#b ,engine1 gears1 shafts1 etc4         
#c ,pump1 #abc2 pump shaft1 #di         
#agb                                    
#d ,hull covering1 including apron and  
piece behind separator                  
#bgd                                    
#e ,gasoline and air tanks1 #afg1 #aad2 
air valve1 #af                          
#big                                    
#f ,smokestack1 #cai2 counter1 #ie2     
burner1 #afe                            

#fgi                                    
#g ,float1 #bge2 pipe from pump to      
boiler1 #dj                             
#cae                                    
#h ,reel1 with fork and float           
#abh                                    
#i ,wing clamps1 #ahh2 guy-post clamps1 
#bab        #bd                         
#aj ,boiler1 #gfd2 steam gauge and      
connections1 #gi                        
#hdc                                    
#aa ,front lower bearing post1 #ge2     
clutch post1 #eh2 rear bearing points1  
#bhh        #aee                        
#ab ,separator and pipes leading to     
engines and pump                        
#ejb                                    
#ac ,drop piece for rudder1 #eg2        
#ge        guy-post for rudder1 #ah     
#ad                                     
#ae                                     
#af                                     
#ag ,wings 7without clamp7              
#bjgg                                   
#ah ,superposed wings1 #cddh            

#ai ,rudder                             
#cbc                                    
#bj ,guy sticks1 each #ec               
#ajf                                    
#ba ,propellers                         
#fbj                                    
#bb ,extra length of midrod             
#cgg                                    
#bc ,wood bowsprit                      
#abh                                    
#bd ,canvas keel1 #cf2 rudder1 #gf      
#aab                                    
#be                                     
#bf                                     
#bg ,fuel 7at starting flight7          
#age                                    
#bh ,water 7at starting flight7         
#aebe                                   
#bi                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#aa1iie #bf4dd                          

#ce                                     
#cf                                     
#cg                                     
#ch ,total area of support 7not         
including tail7 sq4 ft4                 
#ed                                     
#ci ,total area of support in feet1     
divided by total flying weight in lbs4  
#b4jd                                   
#dj ,total area of horizontal tail sq4  
ft4                                     
#i4e                                    
#da ,total area of rudder 7vertical7    
sq4 ft4                                 
#g4ge                                   
#db ,horse-power at brake ,horse-power  
by formula99                            
#dc                                     
#dd ,lift at pendulum 7during one       
minute absolute7                        
#de ,lift at pendulum 7during one       
minute in terms of wt47                 
#df ,minimum pressure with which wheels 
turn                                    
#dg ,position of center of pressure of  

wings   #dj from front                  
#dh                                     
#di                                     
#ej ,curvature of wings1 #a in #ah      
#ea ,root angle of wings1 #aj           
#eb ,tip angle of wings1 #aj            
#ec ,position of wings--front edge of   
front wing1 #aeie4g2 of rear wing1      
#adjf4e                                 
#ed ,how guyed--with wires from wing to 
wing on top and to guy-post on bottom   
#ee                                     
#ef                                     
#eg                                     
#eh ,position of center of rudder1      
#abgi4e                                 
#ei ,angle of tail1 #aj                 
#fj ,co-efficient elasticity of tail    
#fa  ,position of rudder                
#fb                                     
#fc ,line of thrust1 #aejj              
#fd ,center of gravity#a of whole1      
#adhd4d                                 
#fe ,center of gravity#b                
#ff ,center of pressure#a of whole      

estimate                                
#fg ,center of pressure#b               
#fh                                     
#fi                                     
#gj                                     
#ga                                     
#gb                                     
,parts4 ,remarks4   #a ,front edge of   
bowsprit1 #agjb4g4 ,weight #bhfg gm4 for
 part #a  includes also part #b4   #b   
,center of float with small wind vane   
rudder1 #afbh4i4   #f ,front edge of    
midrod1 #afac4g4   #i ,center of float  
with small rudder off1 #afji4b4   #ab   
,front edge of ,f4 ,w41 #aeie4g4   #ae  
,c4 of ,p4 on ,f4 ,w41 #aefc4g4   #ah   
,back edge of ,f4 ,w41 #aeae4g4   #ba   
,line through center of propellers1     
#aejj4   #be ,c4 of ,g41 #adhd4d4   #bh 
,front edge of ,r4 ,w41 #adjf4e4   #ca  
,c4 of ,p4 on ,r4 ,w41 #acgd4e4   #cd   
,end of midrod1 #acea4h4   #cg ,front   
end of rudder1 #acce4   #ci ,back edge  
of ,r4 ,w41 #acbf4e4   #db ,center of   
rudder1 #abgi4e4   #de ,back end of     

rudder1 #abba4  99 ,h4 ,p4              
7,rev4diam4pitch ratiothrust7_/#ccjjj   
,this is calculated on the assumption   
that the center of pressure on each wing
 or on pair of wings at a motion of     
#bjjj feet per minute is in ordinary    
curved wings #b-e the way from front to 
rear1 that for wings of usual size the  
rear wings have #b-c of the efficiency  
per surface of the front ones and that  
the tail proper bears no part of the    
weight2 but if rear wing is smaller or  
larger this efficiency is smaller or    
larger per unit of surface4   p#cjj     
,,data ,,sheet ,no4 #d4   ,weight of    
,aerodrome ,no4 #f1 ,superposed ,wings  
and ,pnaud ,rudder4  ,certified to by   
,chas4 ,m4 ,manly1 ,june #ac1 #ahii4    
----------------------------------------
----------------------  ,parts4         
,sizes4     ,weight4                    
----------------------------------------
--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     
everything of                           

metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for clutch1 etc4                        
#bhfg                                   
#b ,engine1 gears1 shafts1 etc4         
#c ,pump1 #abc2 pump shaft1 #di         
#agb                                    
#d ,hull covering1 including apron and  
piece behind separator                  
#bgd                                    
#e ,gasoline and air tanks1 #afg1 #aad2 
air valve1 #af                          
#big                                    
#f ,smokestack1 #cai2 counter1 #ie2     
burner1 #agj                            
#ehd                                    
#g ,float                               
#cae                                    
#h ,reel1 with fork and float           
#abh                                    
#i ,wing clamps1 #ahh2 guy-post clamps1 
#bd                                     
#bab                                    
#aj ,boiler1 #gfd2 steam gauge and      

connections1 #gi                        
#hdc                                    
#aa ,front bearing point1 #ge2 clutch   
post1 #eh2 rear bearing points1 #aee    
#bhh                                    
#ab ,separator and pipes to engines and 
pump                                    
#ejb                                    
#ac ,drop piece and guy-post for rudder 
#ge                                     
#ad                                     
#ae                                     
#af                                     
#ag ,wings 7without clamp71 #bjgg2      
superposed wings                        
#cddh                                   
#ah ,tail 7without clamp7               
#ai ,rudder                             
#cbc                                    
#bj ,guy sticks                         
#ajf                                    
#ba ,propellers                         
#fbj                                    
#bb ,extra length of midrod             
#cgg                                    

#bc ,wood bowsprit                      
#abh                                    
#bd ,canvas keel1 #cf                   
#cf                                     
#be                                     
#bf                                     
#bg ,fuel 7at starting flight7          
#age                                    
#bh ,water 7at starting flight7         
#aebe                                   
#bi                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#ac1bge                                 
#ce                                     
#cf                                     
#cg                                     
#ch ,total area of support 7not         
including tail7 sq4 ft4                 
#hg4d                                   
#ci ,total area of support in feet1     
divided by total flying weight in lbs   

#dj ,total area of horizontal tail sq4  
#i4e               ft4                  
#da ,total area of rudder 7vertical7    
#g4ge              sq4 ft4              
#db ,horse-power at brake ,horse-power  
by formula99                            
#dc                                     
#dd ,lift at pendulum 7during one       
minute absolute7                        
#de ,lift at pendulum 7during one       
minute in terms of wt47                 
#df ,minimum pressure with which wheels 
turn                                    
#dg ,position of center of pressure of  
wings1 #dj from front                   
#dh                                     
#di                                     
#ej ,curvature of wings1 #a in #ah      
#ea ,root angle of wings1 #aj           
#eb ,tip angle of wings1 #aj            
#ec ,position of wings--front edge of   
front wing1 #aei                        
#ed ,how guyed                          
#ee                                     
#ef                                     

#eg                                     
#eh ,position of tail                   
#ei ,angle of tail1 #g-a_/b             
#fj ,co-efficient elasticity of tail1   
#abdj grammes at center to deflect to   
the horizontal                          
#fa ,position of rudder                 
#fb                                     
#fc ,line of thrust1 #aejj              
#fd ,center of gravity#a of whole1      
#adhd4d                                 
#fe ,center of gravity#b                
#ff ,center of pressure#a of whole      
estimate                                
#fg ,center of pressure#b               
#fh                                     
#fi                                     
#gj                                     
#ga                                     
#gb                                     
----------------------------------------
--------------------   ,parts4 ,remarks4
   #a ,front edge of bowsprit1 #agjb4g4 
,weight #bhfg gm4 includes parts #b4    
#b ,center of float without small wind  

vane rudder1 #afff4a4 7,center of  float
 with wind vane rudder on1 #afbg47   #h 
,front edge of midrod1 #afac4g4   #aa   
,front edge of ,f4 ,w41 #aehe4   #ac ,c4
 of ,p4 on ,f4 ,w41 #aefc4g4   #af ,rear
 edge of ,f4 ,w41 #aeca4g4   #ai ,line  
through center of propellers1 #aejj4    
#bc ,c4 of ,g41 #adhd4d4   #bf ,front   
edge of ,r4 ,w41 #acie4h4   #bi ,c4 of  
,p4 on ,r4 ,w41 #acgd4e4   #cb ,end of  
midrod1 #acea4h4   #ce ,front end of    
rudder1 #acce4   #ch ,back edge of ,r4  
,w41 #acdb4e4   #dj ,center of rudder1  
#abgi4e4   #dc ,back end of rudder1     
#abba4  99 ,h4 ,p4  7,rev4diam4pitch    
ratiothrust7_/#ccjjj   ,this is         
calculated on the assumption that the   
center of pressure on each wing or on   
pair of wings at a motion of #bjjj feet 
per minute is in ordinary curved wings  
#b-e the way from front to rear1 that   
for wings of usual size the rear wings  
have #b-c of the efficiency per surface 
of the front ones and that the tail     
proper bears no part of the weight2 but 

if rear wing is smaller or larger this  
efficiency is smaller or larger per unit
 of surface4   p#cja    ,,data ,,sheet  
,no4 #e4   ,weight of ,aerodrome ,no4   
#f1 ,flat ,wings and ,pnaud ,rudder4    
,certified to by ,chas4 ,m4 ,manly1     
,june #bb1 #ahii4                       
----------------------------------------
----------------------  ,parts4         
,sizes4     ,weight4                    
----------------------------------------
--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     
everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for clutch1 etc4 7bowsprit1 #gh;g7      
#bhfg                                   
#b ,engine1 gears1 shafts1 etc4         
#c ,pump1 #abc2 pump shaft1 #di         
#agb                                    
#d ,hull covering1 including apron and  
piece behind separator                  
#bgd                                    

#e ,gasoline and air tanks1 #afg1 #agd2 
air valve1 #af                          
#ceg                                    
#f ,smokestack1 #cai2 counter1 #ie2     
burner1 #agj                            
#ehd                                    
#g ,float                               
#cae                                    
#h ,reel1 with fork and float           
#abh                                    
#i ,wing clamps1 #ahh2 guy-post clamps1 
#bd                                     
#bab                                    
#aj ,boiler1 #gfd2 steam gauge and      
connections1 #gi                        
#hdc                                    
#aa ,front bearing post1 #ge2           
clutch-post1 #eh                        
#acc                                    
#ab ,rear bearing points                
#aee                                    
#ac ,separator and pipes to engines and 
pump                                    
#ejb                                    
#ad ,drop piece and guy-posts1 #ah2 for 

rudder1 #eg                             
#ge                                     
#ae                                     
#af                                     
#ag ,wings 7without clamp7              
#bjgg                                   
#ah ,tail 7without clamp7               
#ai ,rudder                             
#cbc                                    
#bj ,guy sticks                         
#ajf                                    
#ba ,propellers                         
#fbj                                    
#bb ,extra length of midrod             
#cgg                                    
#bc ,wood bowsprit                      
#abh                                    
#bd ,other things                       
#be                                     
#bf                                     
#bg ,fuel 7at starting flight7          
#age                                    
#bh ,water 7at starting flight7         
#aebe                                   
#bi                                     

#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#aa1idh #bf4c                           
#ce                                     
#cf                                     
#cg                                     
#ch ,total area of support 7not         
including tail7 sq4 ft4                 
#ed                                     
#ci ,total area of support in feet1     
divided by total flying weight in lbs4  
#dj ,total area of horizontal tail sq4  
ft4                                     
#i4e                                    
#da ,total area of rudder 7vertical7    
sq4 ft4                                 
#g4ge                                   
#db ,horse-power at brake ,horse-power  
by formula99                            
#dc                                     
#dd ,lift at pendulum 7during one       
minute absolute7                        

#de ,lift at pendulum 7during one       
minute in terms of wt47                 
#df ,minimum pressure with which wheels 
turn                                    
#dg ,position of center of pressure of  
wings #dj from front                    
#dh                                     
#di                                     
#ej ,curvature of wings1 #a in #ah      
#ea ,root angle of wings1 #aj           
#eb ,tip angle of wings1 #aj            
#ec ,position of wings                  
#ed ,how guyed                          
#ee                                     
#ef                                     
#eg                                     
#eh ,position of tail                   
#ei ,angle of tail1 #g #cj              
#fj ,co-efficient elasticity of tail1   
#abdj grammes at center to deflect to   
the horizontal                          
#fa ,position of rudder                 
#fb                                     
#fc ,line of thrust1 #aejj              
#fd ,center of gravity#a of whole       

#fe ,center of gravity#b                
#ff ,center of pressure#a of whole      
estimate                                
#fg ,center of pressure#b               
#fh                                     
#fi                                     
#gj                                     
#ga                                     
#gb                                     
----------------------------------------
--------------------   ,parts4 ,remarks4
   #a ,front edge of bowsprit1 #afhe4g4 
,weight #bhfg gm4 includes ,parts #b4   
#b ,back edge of cylindrical part of    
float1 #afjf4e   #e ,front edge of      
midrod1 #afac4g4   #h ,front edge of ,f4
 ,w41 #aeie4g4   #aa ,c4 of ,p4 on ,f4  
,w41 #aefc4g4   #ad ,back edge of ,f4   
,w41 #aeae4g4   #ag ,line through center
 of propellers1 #aejj4   #ba ,c4 of ,g41
 #adhd4d4   #bd ,front edge ,r4 ,w41    
#adjf4e4   #bg ,c4 of ,p4 on ,r4 ,w41   
#acgd4e4   #cj ,end of midrod1 #acea4h4 
#cc ,front end of rudder1 #acce4   #cf  
,back edge ,r4 ,w41 #acbf4e4   #ch      

,center of rudder1 #abgi4e4   #da ,back 
end of rudder1 #abba4  99 ,h4 ,p4       
7,rev4diam4pitch ratiothrust7_/#ccjjj   
,this is calculated on the assumption   
that the center of pressure on each wing
 or on pair of wings at a motion of     
#bjjj feet per minute is in ordinary    
curved wings #b-e the way from front to 
rear1 that for wings of usual size the  
rear wings have #b-c of the efficiency  
per surface of the front ones and that  
the tail proper bears no part of the    
weight2 but if rear wing is smaller or  
larger this efficiency is smaller or    
larger per unit of surface4   p#cjb     
,,data ,,sheet ,no4 #f4   ,weight of    
,aerodrome ,no4 #e1 ,flat ,wings and    
,pnaud ,rudder4  ,certified to by ,chas4
 ,m4 ,manly1 ,june #bc1 #ahii4          
----------------------------------------
----------------------  ,parts4         
,sizes4     ,weight4                    
----------------------------------------
--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     

everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for clutch1 etc4                        
#cjej                                   
#b ,engine                              
#dfd                                    
#c ,pump1 #ccd2 pump shaft1 #ee         
#chi                                    
#d ,hull covering                       
#cih                                    
#e ,gasoline tanks1 air tanks1 valves1  
etc4                                    
#cdh                                    
#f ,smokestack                          
#cgc                                    
#g ,float1 #bge2 drop piece for rudder1 
#eg2 guy-post1 #ah                      
#cej                                    
#h ,reel1 #abh2 steam gauge1 #ha        
#bji                                    
#i ,wing clamps1 #bjj2 guy-post clamps1 
#cb                                     
#bcb                                    

#aj ,boiler1 #gfd2 burner1 #agj2        
counter1                         #ie    
#ajbi                                   
#aa ,rear extension to midrod           
#agd                                    
#ab ,separator and pipes to engine and  
pump                                    
#ejb                                    
#ac ,exhaust pipe                       
#hd                                     
#ad ,front lower bearing point1 #hd2    
clutch post1 #da                        
#abe                                    
#ae ,rear bearing points1 #adf2 extra   
strengtheners1 #cb                      
#agh                                    
#af                                     
#ag ,wings 7without clamp7              
#bcdb                                   
#ah ,tail 7without clamp7               
#ai ,rudder                             
#cbb                                    
#bj ,guy sticks1 each #ef               
#aab                                    
#ba ,propellers                         

#hcg                                    
#bb ,extra length of midrod at front    
#abi                                    
#bc ,wood bowsprit                      
#acb                                    
#bd ,other things                       
#be                                     
#bf                                     
#bg ,fuel 7#cge at starting flight7     
#bjj                                    
#bh ,water 7#bajj at starting flight7   
#faf in boiler                          
#adjj                                   
#bi                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#ac1cgj                                 
#ce                                     
#cf                                     
#cg                                     
#ch ,total area of support 7not         
including tail7 sq4 ft4                 

#fh                                     
#ci ,total area of support in feet1     
divided by total flying weight in lbs   
#dj ,total area of horizontal tail sq4  
ft4                                     
#f4id                                   
#da ,total area of rudder 7vertical7    
sq4 ft4                                 
#g4fd                                   
#db ,horse-power at brake ,horse-power  
by formula99                            
#dc                                     
#dd ,lift at pendulum 7during one       
minute absolute7                        
#de ,lift at pendulum 7during one       
minute in terms of wt47                 
#df ,minimum pressure with which wheels 
turn                                    
#dg ,position of center of pressure of  
wings                                   
#dh                                     
#di                                     
#ej ,curvature of wings                 
#ea ,root angle of wings1 #aj           
#eb ,tip angle of wings1 #aj            

#ec ,position of wings                  
#ed ,how guyed                          
#ee                                     
#ef                                     
#eg                                     
#eh ,position of tail                   
#ei ,angle of tail1 #g #cj              
#fj ,co-efficient elasticity of tail    
#fa ,position of rudder                 
#fb                                     
#fc ,line of thrust1 #aejj              
#fd ,center of gravity#a of whole       
#fe ,center of gravity#b                
#ff ,center of pressure#a of whole      
estimate                                
#fg ,center of pressure#b               
#fh                                     
#fi                                     
#gj                                     
#ga                                     
#gb                                     
----------------------------------------
--------------------   ,parts4 ,remarks4
   #a ,front end of midrod1 #afaa4e4    
#b ,front edge of ,f4 ,w41 #afji4g4   #e

 ,c4 of ,p4 on ,f4 ,w41 #aegg4g4   #h   
,back edge of ,f4 ,w41 #aebi4g4   #aa   
,line through center of propellers1     
#aejj4   #ae ,c4 of ,g41 #adid4f4   #ah 
,front edge of ,r4 ,w41 #adaa4g4   #ba  
,c4 of ,p4 on ,r4 ,w41 #acgi4g4   #bd   
,rear end of midrod1 #acfj4c4   #bg     
,rear end of ,r4 ,w41 #acca4g4  99 ,h4,p
  7,rev4diam4pitch ratiothrust7_/#ccjjj 
,this is calculated on the assumption   
that the center of pressure on each wing
 or on pair of wings at a motion of     
#bjjj feet per minute is in ordinary    
curved wings #b-e the way from front to 
rear1 that for wings of usual size the  
rear wings have #b-c of the efficiency  
per surface of the front ones and that  
the tail proper bears no part of the    
weight2 but if rear wing is smaller or  
larger this efficiency is smaller or    
larger per unit of surface4   p#cjc     
,,data ,,sheet ,no4 #g4   ,weight of    
,aerodrome ,no4 #e1 ,flat ,wings and    
,pnaud ,rudder4  ,certified to by ,chas4
 ,m4 ,manly1 ,july #ab1 #ahii4          

----------------------------------------
----------------------  ,parts4         
,sizes4     ,weight4                    
----------------------------------------
--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     
everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for gears1 clutch1 shafts1 etc4         
#cjej                                   
#b ,engine                              
#dfd                                    
#c ,pump1 #ccd2 pump shaft1 with gear   
and eccentric and end rod1 #ee          
#chi                                    
#d ,hull ,covering1 #bfd2 apron #aae2   
piece behind separator1 #ai             
#cih                                    
#e ,gasoline and air tanks1 #afg1 #afe2 
air valve1 #af                          
#cdh                                    
#f ,smokestack1 #caj2 piece to protect  
midrod1 #fc                             

#cgc                                    
#g ,float1 #bge2 drop piece for rudder1 
#eg2 guy-post1 #ah                      
#cej                                    
#h ,reel1 fork and float1 #abh2 steam   
gauge with pipe1 #ha                    
#bji                                    
#i ,wing clamps1 #bjj2 guy-post clamps1 
#cb                                     
#bcb                                    
#aj ,boiler1 #gfd2 burner1 #agj2        
counter1                         #ie    
#ajbi                                   
#aa ,rear extension to midrod           
#agd                                    
#ab ,separator and pipes to engine and  
pump                                    
#ejb                                    
#ac ,exhaust pipe1 #hd                  
#hd                                     
#ad ,front lower bearing point1 #hd2    
clutch post1 #da                        
#abe                                    
#ae ,rear bearing points1 #adf2 extra   
strengtheners1 #cb                      

#agh                                    
#af                                     
#ag ,wings 7without clamp7 7#bahj in    
#ahif7                                  
#bcdb                                   
#ah ,tail 7without clamp72 part of      
rudder                                  
#ai ,rudder reduced 7,no4 #b or new one1
                          #bii7         
#cbb                                    
#bj ,guy sticks1 each #ef               
#aab                                    
#ba ,propellers 7#ie cms42 wood1 #hcg2  
#ie                         cms4 canvas1
 #edh7                                  
#hcg                                    
#bb ,extra length of midrod 7front71    
#abi             #abi                   
#bc ,wood bowsprit 7complete71 #acb     
#acb                                    
#bd ,other things                       
#be                                     
#bf                                     
#bg ,fuel 7#cge at starting flight7     
#bjj                                    

#bh ,water 7#bajj at starting flight7   
#faf in boiler                          
#adjj                                   
#bi                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#ac1cgi                                 
#ce                                     
#cf                                     
#cg                                     
#ch ,total area of support 7not         
including tail7 sq4 ft4                 
#fh                                     
#ci ,total area of support in feet1     
divided by total flying weight in lbs4  
#dj ,total area of horizontal tail sq4  
#f4id              ft4                  
#da ,total area of rudder 7vertical7    
sq4 ft4                                 
#g4fd                                   
#db ,horse-power at brake ,horse-power  
by formula99                            

#dc                                     
#dd ,lift at pendulum 7during one       
minute absolute7                        
#de ,lift at pendulum 7during one       
minute in terms of wt47                 
#df ,minimum pressure with which wheels 
turn                                    
#dg ,position of center of pressure of  
wings                                   
#dh                                     
#di                                     
#ej ,curvature of wings1 #a in #ab      
#ea ,root angle of wings1 #aj           
#eb ,tip angle of wings1 #aj            
#ec ,position of wings                  
#ed ,how guyed                          
#ee                                     
#ef                                     
#eg                                     
#eh ,position of tail                   
#ei ,angle of tail1 #g #cj              
#fj ,co-efficient elasticity of tail1   
#abdj grammes at center of rudder to    
bring it to a horizontal2 #dij grammes  
at point same distance from front       

end of rudder as length of rudder of    
#ahif1 to bring to horizontal           
#fa ,position of rudder                 
#fb                                     
#fc ,line of thrust1 #aejj              
#fd ,center of gravity#a of whole       
#fe ,center of gravity#b                
#ff ,center of pressure#a of whole      
estimate                                
#fg ,center of pressure#b               
#fh                                     
#fi                                     
#gj                                     
#ga                                     
#gb                                     
----------------------------------------
--------------------   ,parts4 ,remarks4
   #a ,front end of bowsprit1 #agjj4e4  
,front end of midrod #afaa4e4   #c      
,front edge of ,f4 ,w41 #afji4g4   #f   
,c4 of ,p4 on ,f4 ,w41 #aegg4g4   #i    
,rear edge of ,f4 ,w41 #aebi4g4   #ab   
,line through center of propellers      
#aejj4   #af ,front edge of ,r4 ,w41    
#adaa4g4   #ai ,c4 of ,p4 on ,r4 ,w41   

#acgi4g4   #bb ,end of midrod1 #acfj4c4 
#be ,front end of rudder1 #acdc4e4   #bh
 ,back edge of ,r4 ,w41 #acca4g4   #ca  
,center of rudder1 #abhh4   #cd ,back   
end of rudder1 #abbi4e4  99 ,h4,p4      
7,rev4diam4pitch ratiothrust7 _/ #ccjjj 
,this is calculated on the assumption   
that the center of pressure on each wing
 or on a pair of wings at a motion of   
#bjjj feet per minute is in ordinary    
curved wings #b-e the way from the front
 to the rear1 that for wings of usual   
size the rear wing have #b-c of the     
efficiency per surface of the front ones
 and that the tail proper bears no part 
of the weight2 but if rear wing is      
smaller or larger this efficiency is    
smaller or larger per unit of surface4  
p#cjd    ,,data ,,sheet ,no4 #h4        
,weight of ,aerodrome ,no4 #e1 ,flat    
,wings and ,pnaud ,rudder4  ,certified  
to by ,chas4 ,m4 ,manly1 ,july #ai1     
#ahii4                                  
----------------------------------------
----------------------  ,parts4         

,sizes4     ,weight4                    
----------------------------------------
--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     
everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for clutch1 etc4                        
#ceef                                   
#b ,engine1 gears1 shafts1 etc4         
#dgf                                    
#c ,pump1 pump shaft                    
#chi                                    
#d ,hull covering1 #bfd2 apron1 #aae2   
piece behind separator1 #ai             
#cih                                    
#e ,gasoline and air tanks1 #afg1 #afe2 
air valve1 #af                          
#cdh                                    
#f ,smokestack1 #caj2 piece to protect  
midrod1 #fc                             
#cgc                                    
#g ,float1 #bge2 drop piece for rudder1 
#eg2 guy-post1 #ah                      

#cej                                    
#h ,reel1 fork and float1 #abh2 steam   
gauge with pipe1 #ha                    
#bji                                    
#i ,wing clamps1 #bjj2 guy-post clamps1 
#cb                                     
#bcb                                    
#aj ,boiler1 #hjj2 burner1 #agj2        
counter1                         #ie    
#ajfe                                   
#aa ,rear extension to midrod           
#agd                                    
#ab ,separator and pipes to engine and  
pump                                    
#ejb                                    
#ac ,exhaust pipe                       
#hd                                     
#ad ,front lower bearing point1 #hd2    
clutch post1 #da                        
#abe                                    
#ae ,rear bearing points1 #adf2 extra   
strengtheners1 #cb                      
#agh                                    
#af                                     
#ag ,wings 7without clamp7              

#bddf                                   
#ah ,tail 7without clamp71 part of      
rudder                                  
#ai ,rudder                             
#bii                                    
#bj ,guy sticks1 each #ef               
#aab                                    
#ba ,propellers1 #ie cm4 wood           
#hcg                                    
#bb ,extra length of midrod             
#afh                                    
#bc ,wood bowsprit                      
#gh                                     
#bd ,other things                       
#be                                     
#bf                                     
#bg ,fuel 7#cge at starting flight7     
#bjj                                    
#bh ,water 7#bajj at starting flight7   
#faf in boiler                          
#adjj                                   
#bi                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     

#cc                                     
#cd ,total flying weight                
#ce                                     
#cf                                     
#cg                                     
#ch ,total area of support 7not         
including tail7 sq4 ft4                 
#fh                                     
#ci ,total area of support in feet1     
divided by total flying weight in lbs4  
#dj ,total area of horizontal tail sq4  
ft4                                     
#da ,total area of rudder 7vertical7    
sq4 ft4                                 
#db ,horse-power at brake ,horse-power  
by formula99                            
#dc                                     
#dd ,lift at pendulum 7during one       
minute absolute7                        
#de ,lift at pendulum 7during one       
minute in terms of wt47                 
#df ,minimum pressure with which wheels 
turn                                    
#dg ,position of center of pressure of  
wings                                   

#dh                                     
#di                                     
#ej ,curvature of wings                 
#ea ,root angle of wings1 #aj           
#eb ,tip angle of wings1 #aj            
#ec ,position of wings                  
#ed ,how guyed                          
#ee                                     
#ef                                     
#eg                                     
#eh ,position of tail                   
#ei ,angle of tail1 #e                  
#fj ,co-efficient elasticity of         
tail1 #bjj grammes at center gives      
deflection to horizontal                
#fa ,position of rudder                 
#fb ,elasticity caused by two           
#a_/b-;inch                             
rubber bands above and two #a_/d-;inch  
bands1 in tandem1 below                 
#fc ,line of thrust1 #aejj              
#fd ,center of gravity#a of whole       
#fe ,center of gravity#b                
#ff ,center of pressure#a of whole      
estimate                                

#fg ,center of pressure#b               
#fh                                     
#fi                                     
#gj                                     
#ga                                     
#gb                                     
----------------------------------------
--------------------   ,parts4 ,remarks4
   #a ,front end of bowsprit1 #afhc4e4  
#b ,c4 of float1 #afad4e4   #e ,front   
end of midrod1 #afaa4e4   #h ,c4 of reel
 and float1 #aegg4e4   #aa ,front edge  
of ,f4 ,w41 #afji4g4   #ad ,c4 of ,p4 on
 ,f4 ,w41 #aegg4g4   #ag ,rear edge of  
,f4 ,w41 #aebi4g4   #bj ,line through   
center of propellers1 #aejj4   #bd ,c4  
of ,g41 #adih4   #bg ,front edge of ,r4 
,w41 #adjf4g4   #cj ,c4 of ,p4 on ,r4   
,w41 #acgd4g4   #cc ,end of midrod1     
#acfj4c4   #cf ,front end of rudder1    
#acdc4e4   #ci ,back edge of ,r4 ,w41   
#acbf4g4   #da ,center of rudder1 #abhh4
   #dd ,back end of rudder1 #abbi4e4    
#dg ,n4 ,b4--,distance between ,c4 ,p4  
on ,f4 ,w41 and ,c4 ,g4  #gi4g4         

,distance between ,c4 ,p4 on ,r4 ,w4 and
 ,c4 ,g4  #abc4c4 ,if the mean ,c4 ,p4  
is to be over the ,c4 ,g4 we should     
require an efficiency for the rear      
wings of #fd4f4  99 ,h4 ,p4             
7,rev4diam4pitch ratiothrust7_/#ccjjj   
,this is calculated on the assumption   
that the center of pressure on each wing
 or on pair of wings at a motion of     
#bjjj feet per minute is in ordinary    
curved wings #b-e the way from front to 
rear1 that for wings of usual size the  
rear wings have #b-c of the efficiency  
per surface of the front ones and that  
the tail proper bears no part of the    
weight2 but if rear wing is smaller or  
larger this efficiency is smaller or    
larger per unit of surface4   p#cje     
,,data ,,sheet ,no4 #i4   ,weight of    
,aerodrome ,no4 #f1 ,flat ,wings and    
,pnaud ,rudder4  ,certified to by ,chas4
 ,m4 ,manly1 ,july #bg1 #ahii4          
----------------------------------------
----------------------  ,parts4         
,sizes4     ,weight4                    

----------------------------------------
--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     
everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for clutch4 etc4                        
#bhfg                                   
#b ,engine1 gears1 shafts1 etc4         
#c ,pump1 #abc2 pump shaft1 #di         
#agb                                    
#d ,hull covering1 including apron and  
piece behind separator                  
#bgd                                    
#e ,gasoline and air tanks1 #afg1 #agd2 
air valve1 #ah                          
#cfa                                    
#f ,smokestack1 #cai2 counter1 #ie2     
burner1 #agj                            
#ehd                                    
#g ,float                               
#bij                                    
#h ,reel1 fork and float                
#abh                                    

#i ,wing clamps1 #ahh2 guy-post clamps1 
#bd                                     
#bab                                    
#aj ,boiler1 #gfd2 steam gauge and      
connections1 #gi                        
#hdc                                    
#aa ,front bearing point1 #ge2 clutch   
post1 #eh2 rear bearing points1 #aee    
#bhh                                    
#ab ,separator and pipes leading to     
engine and pump                         
#ejb                                    
#ac ,drop piece and guy-post for rudder 
#ge                                     
#ad                                     
#ae                                     
#af                                     
#ag ,wings 7without clamp71 repaired    
#babc                                   
#ah ,tail 7without clamp7               
#ai ,rudder                             
#bii                                    
#bj ,guy sticks                         
#ajf                                    
#ba ,propellers                         

#fbh                                    
#bb ,extra length of midrod             
#cgg                                    
#bc ,wood bowsprit                      
#gh                                     
#bd ,other things 7canvas keel1 #cf2    
rudder1 #gf7                            
#aab                                    
#be                                     
#bf                                     
#bg ,fuel 7at starting flight7          
#age                                    
#bh ,water 7at starting flight7         
#aebe                                   
#bi                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#ab1jai                                 
#ce                                     
#cf                                     
#cg                                     
#ch ,total area of support 7not         

including tail7 sq4 ft4                 
#ed                                     
#ci ,total area of support in feet1     
divided by total flying                 
weight in lbs                           
#dj ,total area of horizontal tail sq4  
ft4                                     
#i4e                                    
#da ,total area of rudder 7vertical7    
sq4 ft4                                 
#g4ge                                   
#db ,horse-power at brake ,horse-power  
by formula99                            
#dc                                     
#dd ,lift at pendulum 7during one       
minute absolute7                        
#de ,lift at pendulum 7during one       
minute in terms of wt47                 
#df ,minimum pressure with which wheels 
turn                                    
#dg ,position of center of pressure of  
wings                                   
#dh                                     
#di                                     
#ej ,curvature of wings1 #a in #ah      

#ea ,root angle of wings1 #aj           
#eb ,tip angle of wings #aj             
#ec ,position of wings4                 
#ed ,how guyed4                         
#ee                                     
#ef                                     
#eg                                     
#eh ,position of tail                   
#ei ,angle of tail1 #e                  
#fj ,co-efficient elasticity of tail1   
#bjj grammes at center to deflect it    
to the horizontal                       
#fa ,position of rudder                 
#fb                                     
#fc ,line of thrust1 #aejj              
#fd ,center of gravity#a of whole       
#fe ,center of gravity#b                
#ff ,center of pressure#a of whole      
estimate                                
#fg ,center of pressure#b               
#fh                                     
#fi                                     
#gj                                     
#ga                                     
#gb                                     

----------------------------------------
--------------------   ,parts4 ,remarks4
   #a ,front end of bowsprit1 #afie4g4  
,weight #bhfg includes ,parts #b4   #b  
,front end of midrod1 #afbc4g4   #e ,c4 
of float1 #afah4b4   #h ,reel and float1
 #aegf4g4   #aa ,front edge1 ,f4 ,w41   
#aeie4h4   #ac ,c4 of ,p4 on ,f4 ,w41   
#aefc4h4   #af ,rear edge ,f4 ,w41      
#aeae4h4   #ai ,line through center of  
propellers1 #aejj4   #bc ,c4 of ,g41    
#adhe4e4   #bf ,front edge of ,r4 ,w41  
#adjf4g4   #bi ,c4 of ,p4 on ,r4 ,w41   
#acgd4g4   #cb ,end of midrod1 #aceb4b4 
#ce ,front end of rudder1 #accc4i4   #ch
 ,rear edge of ,r4 ,w41 #acbf4g4   #dj  
,center of rudder1 #abhj4f4   #dc ,back 
end of rudder1 #abai4i4  99 ,h4 ,p4     
7,rev4diam4pitch ratiothrust7_/#ccjjj   
,this is calculated on the assumption   
that the center of pressure on each wing
 or on pair of wings at a motion of     
#bjjj feet per minute is in ordinary    
curved wings #b-e the way from front to 
rear1 that for wings of usual size the  

rear wings have #b-c of the efficiency  
per surface of the front ones and that  
the tail proper bears no part of the    
weight2 but if the rear wing is smaller 
or larger this efficiency is smaller or 
larger per unit of surface4   p#cjf     
,,data ,,sheet ,no4 #aj4   ,weight of   
,aerodrome ,no4 #e1 ,flat ,wings and    
,pnaud ,rudder4  ,certified to by ,chas4
 ,m4 ,manly1 ,july #bg1 #ahii4          
----------------------------------------
-------------------------  ,parts4      
,sizes4        ,weight4                 
----------------------------------------
-----------------------                 
m4  ft4 gr4 lbs4  #a ,frame1 including  
everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 gears1 shafts1   
etc4 7such as guy-wires and turn        
buckles1 #bf;g74                        
#ccdb                                   
#b ,engine4                             
#dgf                                    

#c ,pump1 #cja2 pump shaft1 #ee2 support
                             to pump1   
#cc4                                    
#chi                                    
#d ,hull covering3 front1 #dg2 sides1   
#ib2 top #df2 small side pieces1 #dd4   
#bbi                                    
#e ,gasoline and air tanks1 #afg1 #afe2 
air valve1 #ah2 netting1 #cj2 piece     
rear of separator1 #bj4                 
#djj                                    
#f ,smokestack1 #caj2 piece to protect  
midrod1 #fc4                            
#cgc                                    
#g ,float1 #bij2 drop piece for rudder1 
#eg4                                    
#cdg                                    
#h ,reel1 fork and float1 #abh2 counter1
                            #ie4        
#bbc                                    
#i ,wing clamps1 #bjb2 guy-post clamps1 
#cc4                                    
#bce                                    
#aj ,burner1 #agj2 boiler #gei4         
#ibi                                    

#aa ,separator with tubes brazed to it4 
#eac                                    
#ab ,steam pipe1 #hg2 steam gauge and   
connections1 #ha4                       
#afh                                    
#ac ,exhaust pipe1 #ij2 wooden plugs in 
nose of frame1 #aj                      
#ajj                                    
#ad ,upper front bearing point and      
clutch post4                            
#acf                                    
#ae ,lower front bearing point1 #hd2    
lower rear bearing point1 #adf2         
clutch1 #da4                            
#bga                                    
#af                                     
#ag ,wings 7without clamp71 front1      
#bffb2 rear #bfje4                      
#becd                                   
#ah ,tail 7without clamp74              
#ai ,rudder4                            
#bii                                    
#bj ,guy sticks #fe2 rear1 #ej4         
#aad                                    
#ba ,propellers1 #ajj cm4 round ends1   

#cj blade4                              
#geg                                    
#bb ,extra length of midrod1 front1     
#agd2 rear1 #bbg4                       
#dja                                    
#bc ,wood bowsprit 7heavy one74         
#acj                                    
#bd ,other things4                      
#be                                     
#bf                                     
#bg ,fuel 7#cij at starting flight74    
#bbe                                    
#bh ,water 7#bjjj at starting flight74  
#aejj                                   
#bi                                     
#cj ,lead on bowsprit to balance4       
#ac                                     
#ca ,sundries unknown4                  
#cb                                     
#cc                                     
#cd ,total flying weight4               
#ad1gjd #a #jc                          
#ce                                     
#cf                                     
#cg                                     

#ch ,total area of support 7not         
including tail74 sq4 ft4                
#fh                                     
#ci ,total area of support in feet1     
divided by total flying weight in lbs4  
#b4aice                                 
#dj ,total area of horizontal tail4 sq4 
ft4                                     
#f4id                                   
#da ,total area of rudder 7vertical74   
sq4 ft4                                 
#g4fd                                   
#db ,horse-power at brake ,horse-power  
by formula99                            
#dc                                     
#dd ,lift at pendulum 7during one       
minute absolute74                       
#de ,lift at pendulum 7during one       
minute in terms of wt474                
#df ,minimum pressure with which wheels 
turn4                                   
#dg ,position of center of pressure of  
wings4                                  
#dh                                     
#di                                     

#ej ,curvature of wings1 #a in #ab1 but 
about #a in #aa now4                    
#ea ,root angle of wings1 #aj4          
#eb ,tip angle of wings #aj4            
#ec ,position of wings4                 
#ed ,how guyed4                         
#ee                                     
#ef                                     
#eg                                     
#eh ,position of tail4                  
#ei ,angle of tail1 #e elevation at     
rear end4                               
#fj ,co-efficient elasticity of tail1   
#bjj grammes at center to deflect it    
to a horizontal4                        
#fa ,position of rudder4                
#fb                                     
#fc ,line of thrust1 #aejj4             
#fd ,center of gravity#a of whole1      
#adih4                                  
#fe ,center of gravity#b4               
#ff ,center of pressure#a of whole      
estimate4                               
#fg ,center of pressure#b4              
#fh                                     

#fi                                     
#gj                                     
#ga                                     
#gb                                     
----------------------------------------
-----------------------   ,parts4       
,remarks4   #a #ac grammes of lead on   
end of bowsprit4   #b ,end of bowsprit1 
#agjh4   #d ,c4 of float1 #afbb4   #f   
,front end of midrod1 #afai4   #i ,reel 
and float1 #afja4e4   #ab ,front edge of
 ,f4 ,w41 #afji4g4   #ae ,c4 of ,p4 on  
,f4 ,w41 #aegg4g4   #ag ,rear edge of   
,f4 ,w41 #aebi4g4   #bj ,line through   
center of propellers1 #aejj   #bd ,c4 of
 ,g41 #adih4   #bg ,front edge of ,r4   
,w41 #adjd4g4   #cj ,c4 of ,p4 on ,r4   
,w41 #acgb4g4   #cc ,end of midrod1     
#acej4c4   #cf ,front end of rudder1    
#accc4e4   #ci ,back edge of ,r4 ,w41   
#acbd4g4   #da ,centre of rudder1       
#abgi4e4   #dd ,rear end of rudder1     
#abbb4   #dg ,distance between ,c4 ,p4  
on ,f4 ,w4 and ,c4 ,g41  #gi4g4         
,distance  between ,c4 ,p4 on ,r4 ,w41  

and ,c4 ,g4  #abe4c4 ,if the mean ,c4   
,p4 is to  be over the ,c4 ,g4 we should
 require an efficiency of #fc4f for the 
rear wings4  99 ,h4 ,p4                 
7,rev4diam4pitch ratiothrust7_/#ccjjj   
,this is calculated on the assumption   
that the center of pressure on each wing
 or on pair of wings at a motion of     
#bjjj feet per minute is in ordinary    
curved wings #b-e the way from front to 
rear1 that for wings of usual size the  
rear wings have #b-c of the efficiency  
per surface of the front ones and that  
the tail proper bears no part of the    
weight3 but if the rear wing is smaller 
or larger this efficiency is smaller or 
larger per unit of surface4   p#cjg     
,,data ,,sheet ,no4 #aa4   ,weight of   
,aerodrome ,no4 #e1 ,superposed ,wings  
and ,pnaud ,rudder4  ,certified to by   
,chas4 ,m4 ,manly1 ,august #c1 #ahii4   
----------------------------------------
----------------------  ,parts4         
,sizes4     ,weight4                    
----------------------------------------

--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     
everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for clutch1 etc4                        
#ceef                                   
#b ,engine1 complete                    
#dgf                                    
#c ,pump1 #cja2 pump shaft1 #ee2 support
                          to pump1 #cc  
#chi                                    
#d ,hull covering1 #bgf2 apron1 #aag2   
piece behind separator                  
#cic                                    
#e ,gasoline and air tanks1 #afg1 #afe2 
air valve1 #ag                          
#cdi                                    
#f ,smokestack and piece to protect     
midrod                                  
#che                                    
#g ,float1 #bij2 drop piece for rudder1 
#eg2 guy-post and clamp1 #ag            
#cfd                                    

#h ,reel1 fork and float1 #abh2 steam   
gauge with pipe1 #ha                    
#bji                                    
#i ,wing claps1 #bjb2 guy-post clamps1  
#cc             #bce                    
#aj ,boiler1 #gge2 burner1 #aga2        
counter1                         #ajj   
#ajdf                                   
#aa ,rear extension to midrod           
#bbg                                    
#ab ,separator and pipes to engine and  
pump                                    
#eac                                    
#ac ,exhaust pipe                       
#ij                                     
#ad ,front lower bearing points1 #hd2   
clutch post1 #da                        
#abe                                    
#ae ,rear bearing points1 #adf2 extra   
strengtheners1 #cb                      
#agh                                    
#af                                     
#ag ,wings 7without clamp7              
#ah ,tail 7without clamp71 part of      
rudder                                  

#ai ,rudder                             
#cji                                    
#bj ,guy sticks1 each #fj               
#abj                                    
#ba ,propellers1 #ajj cm4 round end     
#geg                                    
#bb ,extra length of midrod1 front      
#agd                                    
#bc ,wood bowsprit                      
#acj                                    
#bd ,other things1 #bdh grammes of lead 
on end of bowsprit                      
#bdh                                    
#be                                     
#bf                                     
#bg ,fuel 7at starting flight7          
#bh ,water 7at starting flight7         
#bi                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#ad1ced                                 
#ce                                     

#cf                                     
#cg                                     
#ch ,total area of support 7not         
including tail7 sq4 ft4                 
#hg4e                                   
#ci ,total area of support in feet1     
divided by total flying weight in lbs4  
#b4ge                                   
#dj ,total area of horizontal tail sq4  
ft4                                     
#f4id                                   
#da ,total area of rudder 7vertical7    
sq4 ft4                                 
#g4fd                                   
#db ,horse-power at brake ,horse-power  
by formula99                            
#dc                                     
#dd ,lift at pendulum 7during one       
minute absolute7                        
#de ,lift at pendulum 7during one       
minute in terms of wt47                 
#df ,minimum pressure with which wheels 
turn                                    
#dg ,position of center of pressure of  
wings                                   

#dh                                     
#di                                     
#ej ,curvature of wings1 #a in #aa      
#ea ,root angle of wings1 #aj           
#eb ,tip angle of wings1 #aj            
#ec ,position of wings                  
#ed ,how guyed                          
#ee                                     
#ef                                     
#eg                                     
#eh ,position of tail                   
#ei ,angle of tail                      
#fj ,co-efficient elasticity of         
tail1 #bjj grammes at center gives      
deflection of #e                        
#fa ,position rudder                    
#fb ,elasticity caused by rubber bands  
#fc ,line of thrust1 #aejj              
#fd ,center of gravity#a of whole       
#fe ,center of gravity#b                
#ff ,center of pressure#a of whole      
estimate                                
#fg ,center of pressure#b               
#fh                                     
#fi                                     

#gj                                     
#ga                                     
#gb                                     
----------------------------------------
--------------------   ,parts4 ,remarks4
   #a ,c4 ,p4 on ,f4 ,w41 #aegg4g4   #b 
,line through center of propellers1     
#aejj4   #f ,c4 of ,g41 #adih4   #h ,c4 
,p4 on ,r4 ,w41 #acgb4g4  99 ,h4 ,p4    
7,rev4diam4pitch ratiothrust7 _/ #ccjjj 
,this is calculated on the assumption   
that the center of pressure on each wing
 or on pair of wings at a motion of     
#bjjj feet per minute is in ordinary    
curved wings #b-e the way from front to 
rear1 that for wings of usual size the  
rear wings have #b-c of the efficiency  
per surface of the front ones and that  
the tail proper bears no part of the    
weight2 but if rear wing is smaller or  
larger this efficiency is smaller or    
larger per unit of surface4   p#cjh     
,,data ,,sheet ,no4 #ab4   ,weight of   
,aerodrome1 ,one-,quarter ,model4       
,certified to by ,chas4 ,m4 ,manly1     

,june #aa1 #aija4                       
----------------------------------------
----------------------  ,parts4         
,sizes4     ,weight4                    
----------------------------------------
--------------------                    
m4ft4gr4 lbs4  #a ,frame1 including     
everything of                           
metal1 permanent and undetachable1      
such as bed-plate1 cross-rods for the   
support of propellers1 bearing points   
for clutch1 etc4                        
#cbde                                   
#b ,engine1 bed plates and sparkers     
#dedi  #aj                              
#c ,gears1 shafts1 etc4                 
#affb                                   
#d                                      
#e                                      
#f                                      
#g ,floats1 front1 #bab2 rear1 #bbj     
#dcb                                    
#h ,reel1 float and cord1 #adb          
#adb                                    
#i ,wing clamps1 #hf and #ig2 rudder    

clamp and post                          
#ahc                                    
#aj ,carburetor and fuel                
#gcg                                    
#aa ,spark coil1 #aeab2 holders1 #aaj   
#afbb                                   
#ab ,battery                            
#afbg                                   
#ac ,primary connections                
#ad ,secondary connections              
#ae ,guy-post clamps1 each #ac          
#bf                                     
#af                                     
#ag ,wings 7without clamp71 new flat    
wings                                   
#bfcd                                   
#ah ,tail 7without clamp71 ,pnaud rudder
             #cec                       
#ai ,rudder1 wind vane                  
#hh                                     
#bj ,guy sticks                         
#cj                                     
#ba ,propellers1 #ehe each              
#aagj                                   
#bb ,extra length of midrod1 front1     

#abe2 rear1 #bbe                        
#cej                                    
#bc ,wood bowsprit                      
#ge                                     
#bd ,other ,things                      
#be ,counter                            
#aaj                                    
#bf ,guy-post clamp and post for rudder 
#af                                     
#bg                                     
#bh                                     
#bi ,drop piece for rudder              
#ec                                     
#cj                                     
#ca ,sundries unknown                   
#cb                                     
#cc                                     
#cd ,total flying weight                
#ai1ajd                                 
#ce                                     
#cf                                     
#cg                                     
#ch ,total area of support 7not         
including tail7 sq4 ft4                 
#fa4da                                  

#ci ,total area of support in feet1     
divided by total flying weight in lbs4  
#a4df                                   
#dj ,total area of horizontal tail sq4  
ft4                                     
#f                                      
#da ,total area of rudder 7vertical7    
sq4 ft4                                 
#f                                      
#db ,horse-power at brake #a4e at #gej  
,r4                         ,p4 ,m4     
#dc ,engine gave #b4ja ,h4 ,p4 on brake 
at                         #ijj ,r4 ,p4 
,m4                                     
#dd ,lift at pendulum 7during one       
minute absolute7                        
#de ,lift at pendulum 7during one       
minute in terms of wt47                 
#df ,minimum pressure with which wheels 
turn                                    
#dg ,position of center of pressure of  
wings                                   
#dh                                     
#di                                     
#ej ,curvature of wings1 #a in #bj-a_/b 

#ea ,root angle of wings1 #aj           
#eb ,tip angle of wings1 #aj            
#ec ,position of wings3 ,c4 ,p4 ,f4 ,w41
                            #aeg4hb2 ,c4
 ,p4 ,r4 ,w41 #achf4i                   
#ed ,how guyed                          
#ee ,position of tail                   
#ef ,angle of tail1 #e                  
#eg ,co-efficient elasticity of tail1   
#bjj at center depresses to horizontal  
#eh ,position of rudder 7center71       
#abib4i                                 
#ei                                     
#fj ,line of thrust1 #aejj1 through     
center of propellers                    
#fa ,center of gravity#a of whole1      
#aejc4g                                 
#fb ,center of gravity#b1 #bdig4e       
#fc ,center of pressure#a of whole      
estimate1 #aejc4g                       
#fd ,center of pressure#b1 #beac4b      
#fe ,center of clutch post1 #aeae4d     
#ff ,center of coil1 #aeee4c            
#fg ,center front float1 #af4de         
#fh ,center rear float1 #acgb4f         

#fi ,center wind vane rudder1 #adce4f   
#gj ,center ,pnaud rudder1 #abib4i      
#ga ,rear end ,pnaud rudder1 #abae4i    
#gb ,front end of ,bowsprit1 #agjg4b    
----------------------------------------
--------------------  99 ,h4,p4         
7,rev4diam4pitch ratiothrust7 _/ #ccjjj 
,this is calculated on the assumption   
that the center of pressure on each wing
 or on pair of wings at a motion of     
#bjjj feet per minute is in ordinary    
curved wings #b-e the way from front to 
rear1 that for wings of usual size the  
rear wing have #b-c of the efficiency   
per surface of the front ones and that  
the tail proper bears no part of the    
weight2 but if rear wing is smaller or  
larger this efficiency is smaller or    
larger per unit of surface4   p#cji     
,,index    ,a   ,abbreviations and      
symbols for points on aerodrome ''' #ad1
 #ae   ,accidents1 in launching large   
aerodrome ''' #abf1 #ahd1 #ahe1 #bfe-bha
    loss of model aerodrome ''' #ag1    
#id1 #aed   ,aeolipiles1 alcohol '''    

#ee1 #ef1 #ei1 #fj1 #fe1 #ff1 #aab      
,aerial navigation1 report of ,board of 
,ordnance on ''' #bgf1 #bgi             
,aerodrome1 balancing of ''' #de-eb1    
#ha1 #ij1 #aji1 #acd1 #baa1 #bab        
construction of ''' #ec-hj1 #afd-ahg1   
#bcd-bej    definition of word ''' iii  
dimensions of 7see aerodrome models and 
data sheets74    eighth-size model '''  
#acc1 #acd1 #aed    engines 7see engines
 and motors74    experiments with models
 ''' #f-ad1 #af-bd1 #acc-aee    field   
trials 7see trials74    first flight of 
model1 ,may #f1 #ahif ''' #b1 #c1 #ajg1 
#ajh1 #aag    first trial of a 8flying  
machine0 in free air ''' #ig    flight  
7see also trials74     first model1 ,may
 #f1 #ahif ''' #b1 #c1 #ajg1 #aag       
large machine 7#aijc7 ''' #abf1 #abg1   
#bee-bhb     photographs of ''' #ajh1   
#bei1 #bfj    large ''' #abf1 #abg1     
#abi1 #acj1 #aef1 #ahc1 #bbe1 #bee-bhb  
construction of ''' #afd-ahg1 #bcd-bej  
launching apparatus for ''' #aef-afc1   
#ahc     shop tests ''' #bea-bed        

trials 7#aijc7 ''' #abf1 #aha1 #bee-bhb 
weight of ''' #bgg    launching         
apparatus for models ''' #ib-abb1 #acc1 
#acd       large aerodrome ''' #aef-afc1
 #ahc    man-carrying 7see also         
aerodrome large7 ''' #abc1 #abe1 #abi1  
#acj1  #aea1 #aec1 #aef-ahg1 #bcd-bej1  
#bee1 #bhb4    model1 descriptions of   
7see also data sheets74       ,no4 #j   
''' #ba1 #cj1 #ca1 #cf1 #ch1 #dj1 #ec1  
#ee1 #ge       ,nos4 #a1 #b1 #c ''' #bh1
 #bi1 #ch1 #dj1 #ec       ,no4 #d '''   
#ec1 #fb-fg1 #fi1 #gj1 #gb1 #ge-gi1     
#ha-hc1 #hf1 #ib-aji1 #abj       ,no4 #e
 ''' #bf1 #fd-ff1 #fi1 #gj1 #ge-gi1 #ha1
 #hb-hd1 #hf1 #hh1 #hi1  #ij1 #ib-aji1  
#aaj-abb1 #acj1 #aca1 #acd1 #ace-aee1   
#aeh1 #agd1 #ahh1 #ahi1  #bjh-baj1 #bca1
 #beg1 #bha4       ,no4 #f ''' #di1 #fa1
 #fb1 #gh-ha1 #hi1 #ij1 #ib-aji1        
#aaj-abb1 #acj1  #aca1 #acd1 #aeh1 #agd1
 #ahh1 #aic1 #bjh1 #baj1 #bca1 #beg1    
#bha4       rubber pull ''' #aa-bj      
eighth-size ''' #acc1 #acd1 #aed        
frames of ''' #ci1 #ec-hj1 #ij1 #aab1   

#aai1 #abi     launching apparatus for  
''' #ib-aab1 #acd     quarter-size '''  
#aeh1 #aei1 #agj1 #bbf-bcc1 #bcd1 #bee1 
#beg-bfa1 #bha     results from ''' #ag1
 #abi     steam driven 7see also ,nos4  
#e1 #f7 ''' #abb1 #afd1 #afe1 #bbd1 #bha
     trials1 of ,nos4 #j1 #a1 #b1 #c    
7#ahib7 ''' #bi1 #ec       ,nos4 #d1 #e1
 #f 7#ahic7 ''' #fc1 #ib-ajf       ,nos4
 #e1 #f 7#ahif7 ''' #b1 #gi1 #ajf-aji   
,no4 #f 7#ahih7 ''' #fa       ,nos4 #e1 
#f 7#ahii7 ''' #di1 #gi1 #ace-aee1 #bca1
 #beg       ,nos4 #cj1 #ca1 and others  
''' #f-ad1 #ag1 #ai    motors 7see      
engines and motors74    quarter-size    
models 7see aerodrome models74          
rubber-power models ''' #e1 #h-bd1 #dd  
weights of 7see weight and data sheets74
   ,aerodromics1 science of ''' iii1 #g 
,aerodynamics ''' #g1 #cj1 #dc1 #dd1    
#hj1 #ia1 #ii    experiments in ''' #a1 
#f1 #g1 #ai1 #ba1 #cb1 #da1 #hj1 #ih1   
#abh1 #aej1 #aec   ,aeronaut 7see also  
aviator7 ''' #acj   ,air1 compressed '''
 #aa1 #bd1 #be1 #bf1 #fh1 #aab    liquid

 ''' #aed    resistance of ''' #f1 #h1  
#i1 #adb1 #afe-afg   ,air-chamber '''   
#fd1 #fh1 #fi1 #ih1 #aab1 #aac          
,air-cooled engine ''' #bbf   ,alcohol  
and hydrocarbons1 use of1 as fuel '''   
#bd1 #be1 #ce1 #ee1 #eg1 #ff1  #gb1 #gc 
,alcohol aeolipiles ''' #ee1 #ef1 #fj1  
#ff1 #fi1 #aab   ,allegheny             
,observatory1 experiments at ''' #aa1   
#ac1 #ca1 #aej   ,allotment1            
,government1 for man-carrying aerodrome 
''' #abd-abf1 #acb1 #bgh                
,aluminum-bronze1 use of ''' #aad1 #aaf1
 #agc1 #agd   ,aluminum in engine       
construction ''' #cb1 #aad1 #bdc1 #beb  
sheathing of hull ''' #fi    wires '''  
#hd   ,aneroid barometer for determining
 height ''' #ahf   ,anemometer cups ''' 
#adc   ,angle1 diedral1 of wings '''    
#de1 #hb1 #hi    of inclination ''' #da1
 #dc1 #hc1 #ii1 #ajj     rotation '''   
#fa     wings1 root angle ''' #hc1 #hi1 
#ia1 #ig1 #ih1 #ajj1 #aja1 #ajc   ,area1
 relation to weight and power ''' #dc1  
#dd1 #fd1 #ij1 #ii1 #aja    supporting  

7see also surface7 ''' #hb1 #hg-hi1 #ia1
 #ic   ,asbestos1 use of ''' #ce1 #fc1  
#fg   ,associated ,press statement to   
''' #bff1 #bhj   ,aviator1 equilibrium  
of ''' #afa1 #afi1 #bec    weight of '''
 #acj1 #baj1 #bef   ,aviator's car '''  
#ahe-ahg1 #bad1 #bea1 #beb    jacket '''
 #bgc    seat ''' #ahe    wheel '''     
#bad1 #baf1 #bfe1 #bff1 #bgb   ,b       
,bagging or pocketing of wings ''' #hd1 
#hf1 #ajj1 #aie1 #bjc   ,balance 7see   
also equilibrium7 ''' #hb1 #afe         
,balancing of aerodrome ''' #de-eb1 #ha1
 #ij1 #aji1 #acd1 #baa1 #beh     engine 
''' #bdf1 #bdg     wings and rudder ''' 
#baa1 #bee   ,ball-bearings on launching
 car ''' #afj1 #age1 #agg1 #beb1 #bec   
,bamboo ribs for wings ''' #bjj         
,barometer1 aneroid ''' #ahf   ,barus1  
,dr ,carl1 boiler experiments by '''    
#eh1 #gj-ge1 #ic-ie   ,batteries1       
electric ''' #aa1 #bd1 #bf1 #bg1 #afb1  
#bab1 #bbj-bbb1 #bcg1 #bdj1  #bda1 #beg1
 #bfb1 #bfc   ,bearings1 ball1 on       
aerodrome and launching car ''' #afj1   

#age1 #agg1 #beb1  #bec    bronze1 on   
model aerodromes ''' #agg   ,bedplates  
''' #aaf1 #afh1 #age1 #bgc   8,beehive0 
boilers 7see boilers74   ,bell          
,alexander ,graham ''' #d1 #if1         
#ajb-ajd1 #ajf1 #ajh   ,bessemer steel  
guy wires ''' #agb   ,bevel gears '''   
#agd1 #agg1 #bda   ,bird-wings1         
construction of ''' #g1 #ahh1 #bjj1 #bja
   ,birds1 soaring1 study of ''' #g1 #i1
 #hh1 #bhg   ,blazer1 ,s4 ,m41 engineer 
''' #abf   8,bleeder10 feed tube for    
burner ''' #fg1 #aac   ,blriot aeroplane
 of ,langley type ''' #bhc   ,blower for
 artificial wind ''' #fa1 #ig1 #bbe     
,board of ,ordnance and ,fortification  
''' #abd1 #abf1 #acb1 #bej1 #bee1 #bga1 
#bgf1 #bgh1 #bgi1 #bhj   ,boat1 house   
''' #ib1 #ic1 #acf1 #adh1 #adi1         
#aef-afc1 #bfi   ,body1 construction of 
7see also hull7 ''' #cb1 #fj   ,boiler1 
8,beehive0 type ''' #cd1 #ci    coil of 
''' #cd-ci1 #gj1 #ga1 #aac-aaf          
development of ''' #ee-ei1 #fe1 #fh1    
#gj-ge1 #ajb1 #aad-aaf    pressure '''  

#eh1 #ei1 #fc1 #fh1 #fi1 #aja1 #ajb     
report on1 by ,dr4 ,barus ''' #gj-ge    
serpollet type ''' #ef1 #eg    spray    
type ''' #gj    tests of ''' #gj-ge1    
#ace    tubing of ''' #gj-ge1 #aad1 #ada
    water-tube type of ''' #cd1 #ce1    
#gj-ge1 #aad   ,bolometer1 development  
of ''' #abc   ,brake1 horse-power '''   
#bh1 #cg1 #eh1 #fa1 #fd-fi1 #aag1 #bbc1 
#bbd1 #bcj1 #bcc    ,prony ''' #ch1 #fa1
 #fe1 #ff1 #aag1 #agi1 #bbb1 #bbh1 #bcc1
 #bdi   ,brass1 use of ''' #ed1 #fc1    
#aac1 #ahj   ,brazing ''' #aag1 #agc1   
#age1 #bce1 #bcf   ,bronze1 aluminum '''
 #aad1 #aaf1 #aga1 #agc1 #agg1 #bcd1    
#bcg-bdj   ,burners1 ,bunsen type '''   
#ce1 #fh1 #gb1 #aac    gasoline ''' #ef1
 #fj1 #fa1 #fb1 #fe1 #fg1 #fh1 #gj-ge1  
#aab-aaf1 #adi    shield for ''' #fj1   
#fg1 #ie1 #aae   ,bushing1 cast-iron '''
 #aad-aag1 #aba   ,buzzard1 ,american1  
and 8,john ,crow10 study of ''' #bhe    
,c   ,cameras1 telephoto ''' #bfj1 #bfa1
 #bgc   8,canvas-covered0 propellers '''
 #hd1 #agh   ,car1 aviator's '''        

#ahe-ahg1 #bad1 #bea1 #beb    launching 
7see launching apparatus74   ,carbon1   
energy developed by the use of ''' #bg  
,carbonic-acid gas as motive power '''  
#aa1 #bd1 #bf1 #bh1 #bi1 #ci1 #ec1 #ed  
liquid ''' #bd1 #bh     freezing of ''' 
#bh-bi     latent heat of ''' #bh       
,carburetor1 development of1 suitable   
type of ''' #bbd1 #bbe1 #bci1 #bdj1     
#bdh1 #bdi1 #bea1 #bec1 #bei            
,carpenter1 ,frank ,g41 witnesses       
flights ''' #ajh   ,cast-iron1 use of   
7see also iron7 ''' #aad-aag1 #aba1     
#bcd-bcf1 #bdj   8,cast-off0 apparatus  
''' #if1 #aaj   ,center of gravity '''  
#aj1 #ac-af1 #de-eb1 #fa1 #fd1 #hj1 #ia1
 #ajc1 #adc1 #add1  #aej1 #bji1 #baj    
in relation to pressure ''' #aj1 #aa1   
#ae1 #df1 #dh1 #fd1 #ih1 #ii1 #aja1     
#ajc     pressure ''' #g1 #aj1 #aa1 #ac1
 #ae1 #de-eb1 #gh1 #hj1 #hd1 #hg1 #hh1  
#ij1 #ia1  #bjj1 #bji1 #baj      formul 
for ''' #di1 #hg1 #hh1 #ij     wings and
 tail ''' #af     rotation ''' #fb      
thrust ''' #fb   ,centrifugal pump '''  

#bda1 #bdh   ,charcoal1 as fuel ''' #eg 
,china silk 7see silk74   ,chopawamsic  
,island1 ,potomac ,river ''' #ic1 #ace1 
#aec1 #ahc1 #bef   ,chronograph         
attachments ''' #afb1 #afc1 #bbi        
,circulating pump ''' #aad1 #bdd        
,clamps1 wing ''' #hb1 #hi1 #ade1 #ahc  
,coast and ,geodetic ,survey ''' #ic1   
#ade1 #bef   ,coefficient of elasticity 
''' #adf   ,coil1 spark 7see sparking   
devices74   ,compressed air ''' #bd1    
#be-bf1 #fh1 #aab1 #aac   ,condenser1   
steam ''' #fe   ,construction and tests 
of large engine ''' #bcd-bej            
,construction of frame and engines '''  
#ec-hj      of large aerodrome '''      
#afd-ahg     supporting surfaces '''    
#ahh-bjf   ,control1 equilibrium and '''
 #gg1 #gh1 #aai1 #bjg-bag    gyroscopic 
''' #gh1 #baa   ,cooling systems1 7see  
water and air cooling74   ,copper1 use  
of ''' #bg1 #ci1 #fc1 #gb1 #aab-aae1    
#afb   ,copper tubing ''' #ce1 #ef1 #eg1
 #ei1 #aab1 #aae1 #adj1 #ada1 #bdh      
,counter1 speed ''' #fb1 #abj1 #ahe1    

#bdc1 #bdi     propellers ''' #agh      
,covering for tail ''' #hf1 #ajc        
wings ''' #ed1 #fc1 #gg1 #ha1 #hf1 #hh1 
#ij1 #adh1 #aid1 #aie1 #bje   ,crank    
bell ''' #aaj    starting ''' #bdd      
,crank-pin ''' #bcg-bci1 #bdc-bdg       
,crank-shaft ''' #bcg1 #bci1 #bdd-bdf1  
#bej   ,cube1 law of the ''' #abi1 #acj1
 #bbb1 #bdd1 #bdi   ,currie1 ,rolla ,p41
 report on ,american ,buzzard ''' #bhi  
,curved surfaces 7see also wing         
curvature7 ''' #ah1 #dd1 #dg1 #ii       
,cylinders 7see also engines1           
cylinders74    aluminum in construction 
of ''' #aad    brass in construction of 
''' #ed    steel tubes in ''' #aaf1     
#aba1 #bcd1 #bce1 #bci1 #bdj            
construction of ''' #aab1 #aad1 #aaf1   
#aba1 #bab1 #bac1 #bcb1 #bce1 #bci1     
#bdj1 #bdf    five1 engine ''' #bde1    
#bdf1 #bej1 #bee    high-pressure '''   
#cc    low-pressure ''' #cc    multiple1
 engine ''' #bbf    oscillating ''' #cc1
 #ch    tests of 7see also engine tests7
 ''' #ee    walls of ''' #bci    weight 

of ''' #bdf1 #bdg1 #bej   ,d   ,daniell1
 on energy in storage batteries ''' #bg 
,data sheets ''' #big   ,definitions of 
terms and symbols ''' #ad1 #ae          
,deflection1 absence of ''' #bfi   de   
,lucy1 on sustaining surfaces ''' #ai   
,diedral angle of wings ''' #de1 #hb1   
#hc1 #he1 #hi1 #if1 #adf   ,dimensions  
7see aerodrome descriptions and data    
sheets74   ,distance of flights '''     
#ajc1 #ajg-aji1 #ace-aee1 #beh          
,distortion of wings ''' #hb-hd1 #ia1   
#ih1 #aje   ,dry batteries ''' #bfb     
,duration of flights 7see also time7 '''
 #ajc1 #ajg1 #ajh1 #acg1 #ade1  #adh1   
#beh   ,dynamometer1 use of ''' #bbb1   
#bbh1 #bbi1 #bcj1 #bdb1 #bdg1 #bdi   ,e 
,eagle quill and spruce rib1 comparative
 strength of ''' #bja   ,early steam    
motors and other models ''' #cj-dj      
,efficiency of wings ''' #hg1 #hi1 #ia1 
#add1 #aib1 #aic   ,eighth-size models  
''' #acc1 #acd1 #aed   ,elastic limit of
 rubber ''' #i1 #bb1 #bc   ,elasticity  
of tail ''' #gh1 #ij1 #add1 #aeb        

coefficient of ''' #ea1 #add1 #adf      
,electric batteries ''' #bd1 #bf1 #bg1  
#bab1 #bfb1 #bfc    circuits ''' #gj1   
#bab1 #bbj-bbc1 #bcg1 #bda1 #beg        
,electricity as motive power ''' #bd1   
#bf-bh   ,energy in foot pounds 7see    
also lift7 ''' #bc-bg   ,engine 7see    
also motors7 ''' #aab-aaf1 #agi1 #ahj1  
#bbb-bbe1 #bbf-bcc1  #bcd-bej1 #bha     
,american builders ''' #aca1 #ahj1 #bai1
 #bbh    air-cooled ''' #bbf            
automobile ''' #bai    balancing of ''' 
#bdf1 #bdg    carbonic-acid gas ''' #bd1
 #bf-bi    compressed air ''' #aa1      
#bd-bf1 #fh1 #aab    construction of1   
and frames ''' #ec-gi1 #aad1 #aaf1 #bai1
 #bbc-bcc       tests ''' #bcd-bej      
contract for ''' #abf    cylinders of   
''' #cc1 #ch1 #ed1 #aab1 #aad-aaf1 #aba1
 #bab1 #bac1 #bcb1  #bce-bci1 #bdf1     
#bej1 #bee    description of            
one-horse-power ''' #cg1 #aaf           
electric ''' #bd1 #bf-bh    ,european   
builders ''' #aca1 #adj1 #bai1 #bcd     
experimental ''' #bah-bbe               

five-cylinder ''' #bbd1 #bcb1 #bcd-bej1 
#bee    gas 7see also gasoline7 ''' #bf1
 #bh1 #aca1 #acc    gasoline ''' #bd1   
#cg1 #fe1 #abe1 #aca1 #agi1 #baj1 #bah1 
#bai1 #bbd1 #bgg    gunpowder ''' #bd1  
#be    horse-power 7see also brake1     
horse-power7 ''' #cg1 #eh1 #aaf1 #bcc   
hot-water ''' #bd1 #be1 #fh    large1   
construction and tests of ''' #acc1     
#bcd-bej1 #bha1 #bhb     weight of '''  
#bdg1 #bej1 #bef    ,manly ''' #bai-bbe 
multiple cylinder ''' #bbf              
oscillating ''' #cc1 #ch    radiator '''
 #beb    steam ''' #bd1 #cj-dj1 #fd1    
#fi1 #aaf1 #abj     dimensions of '''   
#aaf    ,stringfellow ''' #cj1 #ca      
tests ''' #cg1 #ee1 #fa1 #fi1 #ajb1     
#acc1 #adh1 #bcd-bej1 #bha1 #bhb        
water-cooled ''' #bbj1 #bce1 #bcf1 #bda1
 #bdg1 #bdh1 #beb    weight of ''' #aaf1
 #abf1 #acj1 #bji1 #bdg1 #bej           
,equilibrium1 maintenance of ''' #f1    
#ca1 #de1 #ea1 #add1 #bac-baf    of     
aviator ''' #afa1 #afi1 #bac1 #bec      
and control ''' #gg1 #gh1 #aai1 #bjg-bag

    lateral1 and longitudinal stability 
''' #ca1 #de-eb   ,evaporation1 rate of 
gasoline ''' #fe1 #ff   ,evaporators '''
 #cg1 #fe1 #fg1 #aad1 #adh   ,f         
8,factor of safety0 ''' #aaa1 #ahf      
,feathers1 pliability of ''' #ahh1 #bjj 
toy-propeller1 blades made of ''' #h    
,feed1 gravity ''' #bci   ,fibre        
insulation ''' #bda1 #beg   ,field      
trials1 eighth-size ''' #acc1 #acd1 #aed
     large and quarto size models '''   
#abf1 #aeh1 #agj1 #aha1 #bbf-bcd1       
#bee-bhb     models ,nos4 #j1 #a1 #b1 #c
 ''' #bi1 #ec      ,nos4 #d1 #e1 #f ''' 
#fc1 #ib-ajf      ,nos4 #e1 #f1 #b '''  
#fa1 #gi1 #ace-aee1 #bca1 #beg          
,fire-proofing preparation ''' #adh     
,first flight of heavier than air       
machine ''' #ajg1 #ajh   ,first trial of
 a flying-machine in free air ''' #ig   
,flexure of wings ''' #hb-hd1 #ia1 #ih1 
#aje   ,flight 7see aerodrome and       
aerodrome model flights74    bird1 study
 of ''' #g    of large machine ''' #abf1
 #aha1 #bee-bhb     ,may #f1 #ahif '''  

#b1 #c1 #ajg-ajh     models ,nos4 #d1   
#e1 #f ''' #b1 #fc1 #gi1 #ib-aji1       
#ace-aee     quarter size model ''' #bei
     rubber-driven models ''' #af-bj    
quarter-size models ''' #aeh1 #agj1     
#bbf-bcc1 #bdc1 #bee1 #beg-bfa1 #bha    
,floating the models ''' #fd1 #fh1 #fi1 
#ii1 #ajc1 #aai1 #abj   ,fly-wheels of  
engine ''' #bdb1 #bdc1 #bdg1 #beb       
,flying aerodrome model as a kite '''   
#acc1 #aed1 #aee   ,flying-weight of    
aerodromes 7see also data sheets7 '''   
#ae1 #fb1 #fc1  #gf1 #gg1 #ha1 #hi1 #ia1
 #adh1 #bdg1 #bej1 #bef   ,foot-pounds1 
definition of ''' #ae    energy in 7see 
also horse-power7 ''' #bb1 #bg1 #fb     
,force-pump ''' #eg   ,formul3    area  
''' #ai    center of pressure ''' #di1  
#hg1 #hh1 #ij1 #aja    drift ''' #da1   
#dc    efficiency ''' #dg    ,harting's 
''' #ai    horse-power ''' #ae1 #fb     
lift or weight ''' #da1 #dc1 #fb        
,manly's1 for changing center of        
pressure ''' #ea    ,maxim's1 for       
horse-power ''' #ae    resistance '''   

#da    soaring speed ''' #ia    tandem  
wing ''' #hg    work 7see also          
horse-power7 ''' #ah1 #bc1 #bg1 #fb     
,frame1 construction of1 model ''' #ci1 
#ec-hj1 #ij1 #aab1 #aai1 #abi      large
 aerodrome ''' #afd-ahg1 #bec    main   
''' #afe-afh1 #agj    resistance of ''' 
#afe-afg    testing of ''' #gi          
transverse ''' #gg1 #afe1 #agd-agh      
work ''' #aah   ,french academy1        
communication to ''' #c   ,fuel1 alcohol
 and hydrocarbon ''' #bd1 #be1 #ce1 #ee1
 #eg1 #ff1 #gb1 #gc    carbon ''' #bg   
carbonic acid gas ''' #aa1 #bd1 #bf1    
#bh1 #bi1 #ci1 #ec1 #ed    charcoal ''' 
#eg    gas ''' #bf1 #bh1 #cg    gasoline
 ''' #bd1 #be1 #cf1 #cg1 #fe-fh1 #aab1  
#abe1 #bbd1 #bdh1 #bei    quantity of   
''' #fh   ,fuel-tank ''' #cf1 #fe1 #fg1 
#fh1 #aab1 #aac   ,funds for experiments
 ''' #abd-abf1 #acb1 #beg1 #bgh1 #bgi1  
#bha   ,g   ,gaertner1 ,mr41 instrument 
maker ''' #ic1 #ie   ,gas1 carbonic-acid
 ''' #bd1 #bf1 #bh1 #cf1 #fh1 #aac      
,gas-burners ''' #ce1 #ee1 #fj1 #fe1    

#gj-ge1 #aab1 #aac   ,gas-engine 7see   
also engines1 gas and gasoline7 ''' #bf1
 #bh1 #cg    ,five cylinder ''' #bbd1   
#bcd-bej1 #bee    large ''' #bcd-bej1   
#bgg    model ''' #bf-bh1 #fe1 #aca1    
#acc1 #bcb-bcd   ,gasoline-burners '''  
#ef1 #fj1 #fb1 #fe1 #fg1 #fh1 #gj-ge1   
#aab-aaf1 #adi   ,gasoline-engines '''  
#bd1 #cg1 #fe1 #abe1 #aca1 #agi1 #baj1  
#bah-bbe1 #bcb-bcd1  #bdh1 #bei1 #bgg   
,gasoline-evaporator ''' #cg1 #fe1 #adh 
,gears ''' #aad1 #aag1 #acf1 #acg1 #afh1
 #agd1 #age1 #agg1 #bcg1 #bda   ,gibson1
 ,captain1 recorder ''' #bej            
,goldbeater's skin1 for wings ''' #gg   
,goode1 ,g4 ,brown ''' #ig   ,government
 allotment 7see also ,board of ,ordnance
 and  ,fortification7 ''' #abd-abf1     
#acb1 #bgi   ,gravity1 center of '''    
#aj1 #ac-af1 #de-eb1 #fa1 #fd1 #hj1 #ia1
 #ih1 #aja1 #ajc1  #adc1 #add1 #aej1    
#bji1 #baj   ,gravity-feed ''' #bci     
,guiding 7see equilibrium and control2  
sustaining surfaces2 and  rudder74      
,gun-metal ''' #agd   ,gunpowder '''    

#bd1 #be   ,guy-posts ''' #ahd1 #ahi1   
#aii1 #bff1 #bfg1 #bfh1 #bgj1 #bgd1 #bge
   ,guying1 early systems of ''' #ha1   
#hd-ia    wire ''' #ha1 #hd-ij1 #ii1    
#afd-agc1 #ahi1 #aia1 #aif1 #aii1 #bfd1 
#bff   ,gyroscopic control ''' #gh1 #baa
   ,h   ,harting's formula ''' #ai      
,head resistance ''' #adb1 #afe-afg     
,heating apparatus 7see burners74       
,herring1 ,a4 ,m41 assistant ''' #ajd   
,hewitt1 ,mr41 at rescue of ,mr4 ,manly 
''' #bgc   ,hodgkin's fund1 aid from '''
 #beg   ,holmes1 ,w4 ,h4 ''' #bhf1 #bhi 
,horizontal flight1 velocity required to
 sustain ''' #a1 #af-ai1 #dc1 #ia       
rudder ''' #h   ,horse-power1 exerted by
 rubber ''' #i1 #bb    ,maxim's formula 
''' #ae    required to sustain flight   
''' #a    developed ''' #bh1 #cg1 #ee1  
#eh1 #fd-fi1 #aag1 #agi1 #bbc1 #bcc1    
#bdi   ,hot-water engine ''' #bd1 #be   
,house-boat and launching apparatus ''' 
#ib-aji1 #aaj-abb1 #adh1 #adi1 #aef1    
#afc1 #bfi   ,huffaker1 ,e4 ,c4 ''' #dd1
 #df   ,hull1 construction of ''' #cj1  

#cb1 #cf1 #ec1 #fj1 #fi1 #ge1 #aab1     
#aah-aba    forms of ''' #cj1 #ca1 #cb1 
#ch1 #fj1 #fi    resistance ''' #di1 #fi
    steel tubes for ''' #ci1 #fi1 #ge1  
#aab1 #aah1 #abj   ,i   ,ignition 7see  
electric batteries and circuits74       
,indian rubber for power 7see also      
rubber7 ''' #ba1 #dj   ,internal work of
 the wind ''' #f1 #db   ,inclination1   
angle of ''' #da1 #dc1 #hc1 #ii1 #ajj   
,insulation ''' #add1 #bda1 #beg        
,iron1 use of ''' #fc1 #fd1 #aad-aag1   
#bcd1 #bcf1 #bdj   ,j   ,jacket1 cork1  
aviator's ''' #bgc    water ''' #bbj1   
#bcd1 #bcf1 #bda1 #bdg1 #beb   8,john   
,crow0 7bird of ,jamaica71 study of ''' 
#bhe   ,k   ,kite1 model flown as '''   
#acc1 #aed1 #aee   ,l   ,langley4 ,s4   
,p4 ''' #c1 #d1 #i1 #ah1 #gf-gi1 #ic1   
#ie1 #ajb-ajh1 #aab1 #abc-abf1  #abh1   
#aca1 #acc1 #ace1 #aec1 #aef1 #afa1     
#agi1 #ahc1 #ahd1 #ahh1 #baa1 #bab1     
#bai1 #bbc1 #bcj1 #bca1 #beg1 #bff-bfh1 
#bgj1 #bga1 #bhg1 #bhj1 #bha            
statement of ''' #abd1 #bhj    letter of

 instructions from 7see appendix74      
study of 8,john ,crow0 bird 7see        
appendix74    aerodrome1 ,war           
,department report on ''' #bgg1 #bgh1   
#bgi   8,langley type0 of aerodrome ''' 
#gg1 #afd1 #bjh1 #bdd1 #bff1 #bgf1      
#bgh-bha      rudder ''' #gg1 #hf       
,lateral stability ''' #de-eb1 #ig      
,launching1 difficulties of ''' #aj1    
#aa1 #ab1 #ib1 #id1 #if1 #ii    methods 
of ''' #ac1 #id-ig1 #aaj    of large    
machine ''' #bfe-bfg1 #bga-bgb1 #bgf1   
#bhb   ,launching-apparatus ''' #ib-abb1
 #acd1 #adi1 #aef-afc1 #ahc1 #ahe1 #bca1
 #beg1  #bfa1 #bfe-bfg1 #bgj1 #bgb1     
#bgf1 #bhb    overhead ''' #e1 #ib-abb1 
#acc-ace1 #aci1 #adb1 #adc1 #ade1 #aea1 
#aeb1 #aed1  #aef-afc    underneath ''' 
#acd1 #ace1 #ade-adg1 #aea1 #aeb1 #aed1 
#aef-afc1 #ahc    weakness of ''' #bfe1 
#bgf1 #bhb   ,launching-car ''' #aeh1   
#aei1 #ahc1 #ahd1 #bee1 #beh1 #bfb1     
#bff-bfh1 #bga1  #bgb1 #bgd1 #bgg       
,launching speed 7see also velocity7 '''
 #ace1 #afa1 #afb   ,law of the cube '''

 #abi1 #acj   ,lewis1 ,captain ,i4 ,n4  
''' #bej   ,lift of propellers 7see also
 pendulum tests7 ''' #fa1 #fb1 #ff1 #fi1
 #gg1  #id1 #ii1 #ajb1 #aje1 #ajg1 #aea1
 #ahi1 #aib   ,lilienthal1 ,otto1 on    
efficiency of curves ''' #dd   ,lineal  
velocity ''' #a1 #dc1 #aaj1 #aff        
,liquid air ''' #aed   ,longitudinal    
stability ''' #de-eb   ,lubrication ''' 
#aac1 #agg1 #bcd1 #bci1 #bdj   ,m       
,mc,donald1 ,mr4 ''' #bff1 #bga1 #bgb   
,mc,kinley1 ,president ,william '''     
#abc1 #abd   ,macomb1 ,major ,m4 ,m41   
report of ''' #bgf-bgh   ,maltby1 ,mr41 
machinist ''' #ic-ie1 #ajb1 #ajf        
,man-carrying machine ''' #abc1 #abe1   
#abi1 #acj1 #aea1 #aec1 #aef-ahg1       
#bcd-bej1 #bee-bhb   ,manly1 ,c4 ,m41   
assistant in charge of experiments '''  
#abc1 #abi1  #bah-bbd1 #bfe1 #bff1 #bfh1
 #bgb1 #bgf1 #bgh      engine '''       
#bai-bbe      formula ''' #ea    ,john  
,m41 description of flight1 by '''      
#bfj-bfa   ,maxim's formula for         
horse-power ''' #ae   ,mechanical flight

 ''' #b-d     theory of ''' #a     ,dr4 
,bell on ''' #d     ,mr4 ,langley on '''
 #c-d   ,mica1 use of ''' #fc1 #gb1     
#aae1 #beg   ,models 7see also aerodrome
 model description and trials74         
experiments with ''' #a1 #acc-aee       
small ''' #f-ad1 #ag1 #ai    flight of  
7see trials74    launching of 7see also 
launching apparatus7 ''' #ib-abb1 #acc1 
#acd    rubber-driven ''' #e1 #h-bd1 #gf
    steam-driven 7see also ,nos4 #d1 #e1
 #f7 ''' #acd1 #ace    steam1 motor1 and
 other ''' #cj-dj   ,motive power 7see  
also engines1 electricity1 and fuel7 '''
 #h1 #aa1  #ba-bi1 #aah    discussion of
 ''' #aa   ,motors1 available 7see also 
engines7 ''' #aa1 #ba-bi1 #bgh          
carbonic acid gas ''' #aa1 #bd1 #bf1    
#bh1 #bi1 #ci1 #ec1 #ed    compressed   
air ''' #aa1 #bd1 #be1 #bf1 #fh1 #aab1  
#aac    construction of early types of  
''' #cj-dj    electrical ''' #bd1 #bf1  
#bg1 #bab1 #bfb1 #bfc    gas ''' #bf1   
#bh1 #cg1 #aca1 #acg    gasoline '''    
#bd1 #cg1 #fe1 #abe1 #aca1 #agi1 #baj1  

#bah1 #bai1 #bbd1 #bgg    gunpowder ''' 
#bd1 #be    hot-water ''' #bd1 #be1 #fh 
rubber ''' #e1 #h-bd1 #gf    steam '''  
#bd1 #be1 #cj-dj    weight of 7see also 
weight of engines7 ''' #aaf1 #abf1 #acj1
 #bji1  #bdg1 #bej   ,mount ,whitney1   
observations on ''' #abc   ,n   ,nash1  
,dr4 ,f4 ,s4 ''' #bgf   ,national       
,museum1 models in ''' #bhb             
,needle-valve ''' #ef1 #eg1 #aac        
,nitric acid1 use of ''' #ga            
,nomenclature of parts of aerodrome ''' 
#ad1 #ae   ,o   ,oiling systems '''     
#aac1 #agg1 #bcd1 #bci1 #bdj   ,open    
wind1 experiments in ''' #db1 #ii1 #beg1
 #bga1 #bgb   ,ordinance and            
,fortification 7see ,board of74         
,oxygen1 necessity of ''' #gb   ,p      
,paper covering for rudder ''' #hf1 #ajc
   ,pnaud1 ,alphonse1 toy aeroplane     
designed by ''' #g-i1 #ba1 #bb1 #dj     
tail or rudder ''' #h1 #ab1 #ac1 #ej1   
#ea1 #gi1 #hb1 #ajg1 #abb1 #aci-adg1    
#aea1 #aeb1 #aec1 #bji1 #baa1 #bac1     
#bad1 #baf1 #bec1 #bfd1 #bgj-bgb        

8,pendulum0 test for lift ''' #fj1 #fa1 
#ff1 #id1 #aca1 #ace1 #baa1 #bab1 #bad1 
#bcb   ,percaline for wing covering ''' 
#aid1 #aie   ,pinion 7see gears74       
,piston 7see engines and cylinders74    
,pitch of propellers ''' #fc1 #fi1 #gf1 
#id1 #aha   ,plane 7see also wings and  
surfaces74    dropper ''' #aej          
surface1 angle of inclination of ''' #f1
 #h1 #da-de1 #fa1 #hc1 #ig1 #ii1 #ajj   
velocity required to sustain ''' #a1    
#dc1 #aaj1 #aff   ,pocketing of wings   
''' #hd1 #hf1 #ajj1 #aie1 #bjc          
,potomac ,river1 location of tests on   
''' #ic   ,power 7see also steam1 fuel1 
and electricity74    development of ''' 
#h1 #ci    formula for ''' #fb          
generating apparatus ''' #aab1 #abe     
relation to area and weight ''' #dc     
,power-gauge 7see dynamometer74         
,powell1 ,major ,g4 ,h41 recorder '''   
#bej1 #bfg1 #bgf   ,press1 attitude of  
''' #abg1 #bfh    report to1 ,mr4       
,langley's ''' #bhj      ,mr4 ,manly's  
''' #bff-bfg   ,pressure1 center of ''' 

#g1 #aj1 #aa1 #ac1 #ae1 #de-eb1 #fd1    
#gh1 #hj1 #hd1 #hg1  #hh1 #ij1 #ia1     
#bjj1 #bji1 #baj      rules for locating
 ''' #di1 #hg1 #hh1 #ij1 #aja      and  
center of gravity ''' #aj1 #aa1 #ae1    
#df1 #dh1 #fd1 #ih-aja1 #ajc    steam   
''' #bd1 #cj-dj1 #ec-ei1 #fc-ge1 #aja1  
#aad1 #aag1 #acd1 #ace1 #acg1  #ada1    
#adb1 #adi1 #aej   ,pressure-gauge '''  
#aad   ,prony-brake ''' #ch1 #fa1 #fe1  
#ff1 #aag1 #agi1 #bbb1 #bbh1 #bcc1 #bdi 
,propellers ''' #g1 #h1 #aa1 #ac1 #bb1  
#dj1 #fh1 #fi1 #id1 #ie1 #ajb1 #ajc1    
#ajh1  #aji1 #aah1 #aai1 #acf1 #aci1    
#adc1 #ade1 #adi1 #agh-ahd1 #beh1 #bfa1 
#bfb1 #bfh1  #bgb1 #bgg    construction 
of ''' #fc1 #gf1 #ih1 #ajj1 #agh-ahd    
early forms of ''' #g1 #h1 #aa1 #bb1 #cc
    lift of ''' #fa1 #fb1 #ff1 #fi1 #gg1
 #id1 #ajb1 #aje1 #ajg1 #aca1 #adh1     
#aea1  #ahi1 #aib    pitch of ''' #fc1  
#fi1 #gf1 #aah1 #aha    position of ''' 
#ci1 #fc    shafts of ''' #ci1 #aag1    
#age-agg1 #bdb    slip of ''' #ajg1 #aji
    speed of 7see also revolutions per  

minute7 ''' #fa1 #ia1 #id1 #ii1  #ajg1  
#aad1 #acd1 #bfd1 #bgb    tests of 7see 
pendulum1 lift1 and thrust74    thrust  
of ''' #dg1 #fb1 #id1 #aai1 #adh1 #aed1 
#afa1 #agd    toy ''' #g1 #h1 #i1 #ba1  
#bb   ,pumps ''' #cf1 #cg1 #eg1 #ei1    
#fe1 #fh1 #ga1 #ge1 #aad1 #aae1 #ada1   
#bda    centrifugal ''' #bda1 #bdh      
circulating ''' #aad1 #bdd              
double-acting ''' #fh1 #aad    force '''
 #eg   ,q   ,quantico1 ,va41 flights at 
''' #fd1 #ff1 #gi1 #ic1 #adg1 #bee1 #bfi
   ,quarter-size model ''' #aeh1 #aei1  
#agj1 #bbf-bcc1 #bdc1 #bee1 #beg-bfa1   
#bha   ,quill1 eagle's1 and spruce rib  
compared ''' #bjj1 #bja   ,r   ,radiator
 7see also engine1 water-cooled7 '''    
#beb   ,randolph1 ,gen4 ,w4 ,f4 '''     
#bgf1 #bgg   ,record of flights 7see    
also data sheets7 ''' #b1 #c1 #ag1 #ajg1
 #aag1  #ace-aee1 #bee-bhb   ,reed1 ,r4 
,l41 chief carpenter ''' #ic-ie1 #ajb1  
#ajf1 #bff1 #bga1 #bgb1 #bge   ,reel    
attached to float ''' #aai1 #abj        
,relation of area to weight and power   

''' #dc1 #dd1 #fd1 #ha1 #hi1 #ij1 #ii   
,reservoir 7see air-chamber and tank74  
,resistance1 air ''' #f1 #h1 #i1 #adb   
of frame and guy-wires ''' #afe-afg     
,revolutions of engine and propellers   
per minute 7see also speed7 '''  #cc1   
#eh1 #fc1 #fe1 #ff1 #ajb1 #aji1 #aae1   
#bdi1 #beb   ,rib1 spruce and eagle's   
quill1 compared ''' #bjj1 #bja   ,ribs1 
construction of ''' #cg1 #hj1 #ha1 #hf1 
#hi1 #ahh1 #aid-bjf1 #bfc1 #bfd         
,ridgway1 ,robert1 on ,american ,buzzard
 ''' #cja   ,root-angle of wings '''    
#hb1 #hc1 #ia1 #ih1 #ajj1 #aja1 #ajc    
,rotation1 angle of ''' #fa    center of
 ''' #fb   ,rubber as a source of power 
''' #e1 #h-bd1 #dd1 #gf    elastic limit
 of ''' #i1 #bb    8fatigue0 of ''' #bc 
horse-power produced by ''' #i1 #bb1 #bc
    springs ''' #b1 #ahe    insulation  
''' #add1 #bda   ,rubber-driven models  
''' #e1 #h-bb   ,rubber-pull and        
rubber-twisted models ''' #af-bd        
,rudder 7see also tail7 ''' #h1 #i1 #gg1
 #hj-ia1 #abb1 #acf1 #bjg-bag1 #bee1    

#bgb1 #bge    horizontal ''' #h         
,pnaud's ''' #h1 #ab1 #ac1 #ej1 #gi1    
#hg1 #ajg1 #abb1 #aci-adg1 #aea1 #bji1  
#baa1 #bac1 #bad1 #baf1 #bec1 #bgj-bgb1 
#bge    vertical evolution of ''' #ha1  
#hb1 #hf1 #ig1 #aja1 #ajf   ,rudder-tail
 7see tail-rudder74   ,s                
,sanding-tests of wings ''' #hd1 #he1   
#hi1 #ii1 #aij-bjd   8,separator10      
evolution of1 for dry steam ''' #eh1    
#ei1 #fe1 #fh1 #aad1 #adb               
,serpollet-type boilers ''' #ef1 #eg    
,shafts1 main1 construction of ''' #aag 
propeller ''' #ci1 #aag1 #age-agg1 #bdb 
,sharp1 ,archibald1 on balancing of     
engines ''' #bdf   ,sheathing1 aluminum 
''' #fi    mica ''' #fc1 #gb1 #aae      
,shop tests ''' #dj1 #bah1 #bea-bed     
,silk wing-covering ''' #ed1 #fc1 #ha1  
#hf-hh1 #ij1 #adh1 #aid1 #aie1 #bje     
,sliding tail designed ''' #af1 #hd     
,smillie1 ,thomas ,w41 photographer ''' 
#bfj1 #bfg1 #bga1 #bgc   ,smithsonian   
,institution ''' #a1 #f1 #ag1 #ah1 #ca1 
#db1 #abd-abf1 #aga1 #agd1  #agf1 #agi1 

#beg1 #bfj1 #bga1 #bgf1 #bhj-bha        
,smoke-stack ''' #fj1 #fg1 #gd1 #gh     
,soaring birds1 study of 7see also      
appendix7 ''' #g1 #i1 #hh               
,soaring-speed ''' #cb1 #da1 #fi        
,sparking devices 7see electric         
batteries and circuits74   ,specific    
gravity ''' #abj   ,speed attained 7see 
also velocity7 ''' #ca1 #cb1 #da1 #ee1  
#fa1 #ia1 #ii1  #ajg1 #aad1 #acd1 #afa1 
#bfd   ,speed-counter ''' #fb1 #abj1    
#ahe1 #bdc1 #bdi1 #beb   ,spokes1 wire  
''' #bdc   ,spruce guy-sticks and frames
 ''' #he-hg1 #ij    ribs compared with  
quills ''' #bjj1 #bja   ,st4 ,louis     
,exposition tests ''' #bdi   ,stability1
 lateral and longitudinal ''' #de-eb1   
#gg   ,starter on launching-car ''' #id1
 #ie   ,starting-crank on launching-car 
''' #bdc1 #bdd   ,steam1 dry1 production
 of ''' #eh   ,steam-chest ''' #aag     
,steam-engine ''' #bd1 #cj-dj1 #fd1 #fi1
 #aaf1 #abj   ,steam-gauge ''' #aad     
construction of frames and ''' #ec-hj   
,steam-generating apparatus ''' #aad-aaf

   ,steam-motors and other models '''   
#cj-dj1 #acd1 #ace   ,steam-pressure '''
 #bd1 #cj-dj1 #ec-ei1 #fc-gj1 #aja1     
#ajb1 #aad1 #aag1 #acd1  #ace1 #acg1    
#ada1 #adb1 #adi1 #aej   ,steel1 use of 
''' #fi1 #aab1 #aaf1 #aai1 #aba1 #agb1  
#agd1 #bcd1 #bgg    tubes1 for hull ''' 
#ci1 #fi1 #ge1 #aab1 #aah1 #abj         
,steering apparatus 7see also           
equilibrium and control7 ''' #bad-baf1  
#bfe1 #bff1 #bgb     automatic ''' #cj1 
#gg1 #baa1 #baf   ,steering wheel '''   
#bad1 #baf1 #bfe1 #bff1 #bgb   ,storage 
batteries 7see batteries1 electrical74  
,stringfellow engine ''' #cj1 #ca       
,superposed wings ''' #ac1 #ad1 #ag1    
#ach1 #aec1 #aic1 #bca   ,supporting    
surfaces ''' #aa1 #dd1 #gg1 #ha1 #ii1   
#ahh-bjf   ,supports for propellers ''' 
#aab     wings and tails ''' #cf1 #fi   
,surfaces 7see also planes and wings74  
covering for ''' #gg1 #ha1 #hf1 #hg1    
#ij1 #adh1 #aid1 #aie    curved ''' #dd1
 #df    plane1 observations on velocity 
of ''' #a    rigid ''' #f1 #df          

supporting ''' #aa #dd1 #gg1 #ic1 #ii   
#ahh-bjf    sustaining ''' #a1 #e1      
#da-dd1 #hj-ia1 #ii     and guiding ''' 
#e1 #hj-ia   ,surgeons' tape1 used for  
mending ribs ''' #bfd   ,sustaining     
surface ''' #a1 #e1 #da-dd1 #hj-ia1 #ii 
de ,lucy on ''' #ai   ,symbols ''' #ad1 
#ae   ,synchronizing mechanism ''' #ajh1
 #aba1 #acf1 #acg   ,t   ,table1 turn   
''' #aef1 #afe1 #aff    whirling ''' #a1
 #e1 #f1 #g1 #aa1 #ac1 #ca1 #db1 #afe1  
#aff1 #agh1 #ahi-aid   ,tachometer '''  
#fb1 #abj1 #ahe1 #bdc1 #bdi1 #beb       
,tail ''' #h1 #i1 #gj1 #gg1 #hj1 #ia1   
#ii1 #bjg-bag    adjustment of ''' #af1 
#hd    connections of ''' #hd1 #bac-baf 
covering ''' #hf #ajc    ,pnaud ''' #ab1
 #ac1 #ej1 #gi1 #ajg1 #abb1 #aci-adg1   
#aea-aec1 #bji1 #baa1  #bac1 #bad1 #bae 
sliding ''' #af1 #hd    use as guiding  
and sustaining surface ''' #hj          
,tail-rudder ''' #gg1 #hf1 #hg1 #aai1   
#aeb1 #aec    ,langley ''' #gg1 #hf     
,tank1 air ''' #fd1 #fh1 #fi1 #aab1 #aad
    fuel ''' #cf1 #fe-fh1 #aab1 #aac    

water ''' #beb   ,telephoto camera '''  
#bfj1 #bfa1 #bgc   ,tests 7see also     
engine tests1 trials1 and flights74     
boilers ''' #gj-ge1 #ace    construction
 and ''' #bcd-bej    cylinder ''' #ee   
engine ''' #cg1 #ee1 #fa1 #fi1 #ajb1    
#acc1 #ace1 #adh1 #bcd-bej1 #bea-bed1   
#bha    experimental engine '''         
#aijb-aijd ''' #bej    frame ''' #gi    
power ''' #fa1 #fb1 #fi1 #ajb           
resistance ''' #afe-afg    sanding1 of  
wings ''' #hd1 #he1 #hi1 #ij1 #aij-bjd  
shop1 of large machine ''' #dj1 #bah1   
#bea-bed    ,st4 ,louis ,exposition ''' 
#bdi    whirling-table ''' #a1 #e1 #f1  
#g1 #aa1 #ac1 #ca1 #db1 #afe-aff1 #agh1 
#ahi-aid    wing ''' #hd1 #he1 #hi1 #ii1
 #aij-bjd   ,testing ground 7see also   
,quantico7 ''' #fd1 #ff1 #ib1 #ic1 #bee1
 #bef1  #bgg1 #bhj   ,thrust1 center of 
''' #fb    propeller ''' #dg1 #fb1 #id1 
#aai1 #adh1 #aed1 #afa1 #agd            
,thrust-recording devices ''' #bbi1 #bcj
   ,thurston1 ,r4 ,h4 ''' #abh1 #abi    
,time of flights ''' #ajc1 #ajg1 #ajh1  

#aji1 #acg1 #ade1 #adh1 #beh   ,torque  
''' #bbb1 #bdb   ,toy aeroplanes ''' #g1
 #i1 #ba1 #bb1 #dj   ,transmission 7see 
also shaft and gears7 ''' #aag1         
#age-agg1 #bdb   ,transverse frame '''  
#gg1 #afe1 #agd-agh   ,trials1 first '''
 #ig    7#ahia7 ''' #ag    7#ahib7 '''  
#ec1 #ib    7#ahic7 ''' #fe1 #ic-if     
7#ahid7 ''' #fe1 #if-ajj    7#ahie7 ''' 
#aja-ajf    7#ahif7 ''' #b1 #gi1        
#ajf-aji    7#ahig7 ''' #abc-abe        
7#ahih7 ''' #fa    7#ahii7 ''' #gi1     
#ace-aee    7#aijc7 ''' #abf1 #aha1     
#bee-bhb   ,tubes in hull construction  
''' #fi1 #aab1 #aaf1 #aai1 #abj1 #agb1  
#agd1 #bcd1  #bgg   ,turn-table '''     
#aef1 #afe1 #aff   ,turnbuckle 7see also
 guying7 ''' #agj1 #aga1 #agb   ,v      
,valve-chest ''' #aad1 #bac   ,valves   
''' #aad1 #aag1 #bac    exhaust ''' #bcg
    mechanically operated ''' #aad1 #bac
    motion ''' #aab1 #aad1 #aae1 #bac   
needle ''' #ef1 #eg1 #aac1 #bab         
,vaporization ''' #cg1 #fg1 #adh1 #adi  
,varnish1 collodion ''' #aib    not     

affected by ammonia ''' #aih            
pyroxelene ''' #hf    water-proof '''   
#bfc1 #bfd   ,velocity ''' #ah1 #ca1    
#cb1 #ee1 #ia1 #ii1 #ajg1 #aji1 #aad1   
#acd1 #aej1 #afa1  #aff1 #ahe1 #bfd1    
#bfe    initial ''' #ajj1 #aaj1 #aej1   
#afc    required to sustain plane '''   
#a1 #dc1 #aaj1 #aff   ,vertical rudder  
''' #ha1 #hb1 #hf1 #ig1 #aja1 #ajf      
,vulcanite1 use of ''' #beg   ,w   ,war 
,department1 allotment ''' #abd-abf1    
#acb1 #bgh1 #bgi     ,board of ,ordnance
 and ,fortification ''' #abd-abf        
,report of ''' #bgf-bhj   ,washington   
,evening ,star1 report of ''' #bgd      
,watches1 stop1 for timing flight '''   
#aji   ,water1 cooling1 for engine '''  
#bce1 #bcf1 #bda1 #bdg1 #bdh1 #beb      
,water-engine1 hot ''' #bd1 #be         
,water-jacket ''' #bbj1 #bcd1 #bcf      
,water-proof varnish ''' #bfc1 #bfd     
,water-tank ''' #beb   ,watkins ,j4 ,e4 
''' #ci   ,weight 7see also data        
sheets74    flying1 of aerodrome '''    
#ae1 #ch1 #fb1 #fc1 #gf1 #gg1 #ha1 #hi1 

#ij1 #ia1  #aja1 #aji1 #aaf1 #adh1 #bjf1
 #bdg1 #bej1 #bef1 #bgg    of aerodrome 
''' #ca1 #ch1 #dj1 #ec1 #fb1 #fc1 #aaf1 
#abf1 #acj1 #bjf1 #bef     covering for 
wings ''' #aid     parts of aerodrome   
''' #ca1 #fc1 #aaf1 #aij1 #bej          
engine ''' #aaf1 #aag1 #abf1 #acj1 #aef1
 #bji1 #bdg1 #bej1 #bgg    per          
horse-power ''' #ca1 #abf    relation to
 area and power ''' #dc1 #dd1 #fd1 #ha1 
#hi1 #ij1 #if    total1 with aviator '''
 #bef   ,wellner1 ,georg ''' #dd1 #dg   
,wheel1 fly ''' #bdb1 #bdc1 #bdg1 #beb  
steering ''' #bad-baf1 #bfe1 #bff1 #bgb 
,whirling-table ''' #a1 #e1 #f1 #g1 #aa1
 #ac1 #ca1 #db1 #afe-aff1 #agh1 #ahi-aid
   ,widewater1 ,va41 experimental       
grounds 7#aijc7 ''' #bee1 #bef1 #bgg1   
#bhj   ,wind1 artificial ''' #db1 #fa   
difficulties of launching in ''' #id1   
#ii1 #bfe1 #bga1 #bgb1 #bgf1 #bhb       
experiments in ''' #db1 #fa1 #ii1 #beg1 
#bga    internal work of the ''' #f1 #db
    open ''' #db1 #ii1 #beg1 #bga1 #bgb 
,wind-shield for burners ''' #fj1 #fg1  

#ie1 #aae   ,wind-vane rudder ''' #acf  
,wing-clamps ''' #hb1 #hi1 #ade1 #ahc   
,wings1 adjustment of1 for center of    
gravity ''' #af    angle of ''' #de1    
#fa1 #hb1 #hc1 #hi1 #ia1 #ig1 #ih1 #ajj1
 #aja1 #ajc    arrangement of '''       
#de-dg1 #gg1 #hf1 #hi1 #aid1 #bee       
bagging of ''' #hd1 #hf1 #ajj1 #aie1    
#bjc    bird1 construction of ''' #g1   
#ahh1 #bjj1 #bja    boxes for ''' #bfc1 
#bfd    construction of ''' #g1 #gj1    
#hj1 #ha1 #hg1 #ij1 #ia1 #ii1 #aje1     
#aai1 #aba1  #ach1 #ahh-bjf    covering 
of1 cloth ''' #aie1 #aii1 #bjd1 #bje    
goldbeater's skin ''' #gg      paper '''
 #hf      silk ''' #ed1 #fc1 #ha1       
#hf-hh1 #ij1 #adh1 #aid1 #aie1 #bje     
weight of ''' #aid    curvature of '''  
#ah1 #dd1 #df1 #dg1 #hf1 #hg1 #ij1 #ii1 
#aab    distortion of ''' #hb1 #hc1 #hd1
 #ia1 #ih1 #aje    double tier ''' #ac1 
#ad1 #ag1 #ach1 #aic1 #bca    efficiency
 of ''' #df1 #hg1 #hi1 #ia1 #add1 #aib1 
#aic    flexure of 7see distortion of74 
pocketing of ''' #hd1 #hf1 #ajj1 #aie   

#bjc    quills and spruce ribs compared 
''' #bjj1 #bja    ribs of ''' #cg1 #hj1 
#ha1 #hf1 #hi1 #ahh1 #aid-bjf    single 
tier ''' #ag1 #adb1 #adf1 #adg-aea1     
#aec1 #aib1 #aic1 #bca    superposed '''
 #ac1 #ad1 #ag1 #ach1 #aec1 #aic1 #bca  
surface of ''' #i1 #fi1 #ha1 #ii        
tandem efficiency of ''' #df1 #hg    two
 sets of ''' #ac1 #gg1 #ajf1 #ach1 #bca 
weight of ''' #aij1 #aif   ,wire guying 
''' #ha1 #hd-ia1 #ii1 #afd-agc1 #ahi1   
#aia1 #aie1 #aif1 #aii1 #bfd1  #bff     
resistance ''' #afe-afg    spokes '''   
#bdc   ,wooden guy sticks ''' #fc1 #ha1 
#he    ribs ''' #cg1 #hj1 #ha1 #hf1 #hi1
 #ahh1 #aid-bjf1 #bfc1 #bfd   ,wrecking 
of large machine ''' #abf1 #ahd1        
#bfe-bha   ,z   ,zinc1 energy developed 
from ''' #bg1 #bda   ,zoological ,park  
cameras ''' #bfj1 #bfa1 #bgc            
,,transcriber',s ,,endnote  ,original   
spelling and grammar have been generally
 retained1 with some exceptions noted   
below4  ,illustrations are moved from   
inside paragraphs to between paragraphs4

  ,footnotes have been renumbered and   
moved from the ends of pages to the to  
the ends of the appropriate sections1   
which are3 ,advertisement 7page iii72   
,part ,i2 and ,part ,,ii1 up to just    
ahead of the ,,data ,,sheets1 which have
 their own footnotes1 which were neither
 moved nor renumbered4  ,pages #af-ah4  
,page #af ended at with another one1    
,no4 #ca1 also shown1 followed by       
,plates #a-d1 followed by page #ag1     
which contained two data tables1        
followed by page #ah1 which continued   
the original paragraph4 ,the transcriber
 has closed the paragraph1 and moved the
 ,plates and tables to follow it4       
,pages #ca-cb4 ,the footnote on page #ca
 said only ,see footnote on page #cb4   
,the footnote on page #cb had no anchor 
in the text4 ,therefore1 to simplify1   
the page #ca footnote has been          
eliminated1 and its anchor is linked    
directly to the page #cb footnote4      
,pages #df-dg4 ,the footnote on page #dg
 had no anchor in the text4 ,however1   

the footnote on page #df said only ,see 
,footnote page #dg4 ,therefore1 the     
footnote anchor on page #df has been    
linked directly to the footnote on page 
#dg1 eliminating the page #df footnote4 
,page #fc4 ,the large table was split   
into two tables1 repeating the first    
column in each part4 ,large curly       
brackets 1 1 indicating combination of  
information on two or more lines1 have  
been replaced by ,unicode box drawing   
characters1 e4g4 4 ,tables in general1  
and these box characters in particular1 
may not line up properly unless the user
 is employing a monospaced font4  ,page 
#adj4 ,the paragraph for ,june #bc      
originally ended dotted line in ,plate4 
,the transcriber has inserted  #cd41 as 
a guess4  ,pages #aij-aib4 ,the wide    
tables were split into two1 repeating   
the first column in each part4  ,page   
#aic4 ,the wide tables were transposed1 
row for column4  ,page #bja4 ,the wide  
table was split into two4  ,pages       
#big-cjh1 ,data ,sheets4 ,remarks       

originally situated in the tables are   
appended below each ,data ,sheet4 ,the  
units of measurement were originally    
spelled out--m4,metres2 ft4,feet2       
gr4,grammes2 and lbs4,pounds4 ,in the   
footnotes to the ,data ,sheets1 in the  
phrases curved wings #b-e the way1 and  
rear wings have #b-c of the efficiency1 
the hyphen seems to mean division1 like 
_/4 ,this usage occurs also in the      
caption to ,plate #he1 in ,,scale #a    
#a-af ,,inch ,,to ,,statute ,,mile4     
,page #bii4 ,item #da1 #g #ge changed to
 #g4ge4  ,,index4 ,the original index   
was structured in a way not suitable for
 this ebook4 ,the white space on the    
printed page substituted for words not  
repeated4 ,thus1 under ,balancing of    
aerodrome1  444 1 were indented entries 
for engine1 wings and rudder1 c4 ,this  
spacing has been rendered herein as a   
horizontal bar 1 one for each word to be
 understood as repeated4 ,so in this    
case1 two bars1 meaning ,balancing of4  
,moreover1 page numbers referenced by   

index entries were right-justified and  
preceded by dotted leaders4 ,herein1 the
 leaders have been indicated by         
horizontal ellipsis '''4 ,the leaders in
 the ,table of ,contents have also been 
replaced by ellipses4  ,estimating from 
,internet ,archive's stated scanning    
rate of #djj ppi1 the pages were about  
#f4b by #i4b inches4 ,body text was     
printed in #i point type1 with #c point 
leading1 and footnotes were printed in  
#e4d point type4