,this file was produced from page images
 at the ,internet ,archive4             
,transcriber's ,note   ,this book was   
transcribed from scans of the original  
found at the ,internet ,archive4 ,i have
 rotated some images4 ,the caption for  
,figure #bj was illegible in the scanned
 pages so ,i used a description from a  
paragraph that referred to it4          
,,dirigible ,,balloons                  
,,instruction ,,paper                   
,,charles ,b4 ,,hayward      ,,member1  
,,society ,,of ,,automobile ,,engineers2
 ,,member1 ,,the ,,aeronautical         
,,society2       ,,formerly ,,secretary1
 ,,society ,,of ,,automobile            
,,engineers2 ,,formerly                 
,,engineering ,,editor1 ,,the           
,,automobile                            
,,american ,,school ,,of                
,,correspondence                        
,,chicago ,,illinois                    
,u4,s4,a4                               
,,copyright1 #aiab1 #aiah1 ,,by         
,,american ,,school ,,of                

,,correspondence                        
,,copyrighted ,,in ,,great ,,britain    
,,all ,,rights ,,reserved               
,,dirigible ,,balloons    ,,introduction
   ,of the first attempts of men to     
emulate the flight of birds1 we have no 
knowledge1 but one of the earliest1     
perhaps1 is embodied in the myth of     
,icarus and ,daedalus4 ,xerxes1 it is   
said1 possessed a throne which was drawn
 through the air by eagles4 ,the        
,chinese have sometimes been given      
credit for the invention of the balloon1
 as they have for many other scientific 
discoveries4 ,it is related that a      
balloon was sent up at ,pekin in        
celebration of the ascension of the     
throne by an emperor in the beginning of
 the fourteenth century4  ,illustration3
 ,fig4 #a4 ,de ,lana ,airboat4  99,early
 ,attempts499 ,leonardo da ,vinci       
devoted some time to the problem of     
artificial flight4 ,his sketches show   
the details of batlike wings which were 
to spread out on the downward stroke and

 fold up with the upward stroke4        
,francisco de ,lana planned to make a   
flying ship the appearance of which was 
somewhat like that shown in ,fig4 #a1 by
 exhausting the air from metal spheres  
fastened to a boat4 ,the boat was to be 
equipped with oars and sails for        
propulsion and guiding4 ,the method in  
which he purposed to create the vacuum  
in the spheres consisted of filling them
 with water1 thus driving out the air1  
then letting the water run out4 ,he     
thought that if he closed the tap at the
 proper time1 there would be neither air
 nor water in the spheres4 ,his flying  
ship was never constructed1 for he      
piously decided that ,god would never   
permit such a change in the affairs of  
men4  99,the ,first ,flying ,machine499 
,in #agha1 ,meerwein of ,baden1         
,germany1 constructed a flying machine1 
and was the first1 perhaps1 to          
intelligently take into account the     
resistance of the air4 ,he took the wild
 duck as a basis of calculation1 and    

found that a man and machine weighing   
together #bjj pounds would require a    
wing surface of from #abe to #acj square
 feet4 ,it is of interest to note that  
,lilienthal1 who met his death in trying
 to apply these principles1 over one    
hundred years later found these figures 
to be correct4 ,two views of ,meerwein's
 apparatus are shown in ,fig4 #b4 ,the  
construction involved two wood frames   
covered with cloth4 ,the machine weighed
 #ef pounds and had a surface area of   
#aaa square feet4 ,the operator was     
fastened in the middle of the under side
 of the wings1 and over a rod by which  
he worked the wings4 ,his attempts at   
flight were not successful1 as his ideas
 of the power of a man were in error4   
,illustration3 ,fig4 #b4 ,meerwein      
,flying ,machine  99,classification499  
,all attempts at human flight have gone 
to show that there are four possible    
ways in which man may hope to navigate  
the air4 ,he may imitate the flight of  
birds with a machine with moving or     

flapping wings2 he may use vertical     
screws or helices to pull himself up2 he
 may use an aeroplane and sail the air  
like an eagle2 or1 lastly1 he may raise 
himself by means of a gas bag and either
 drift with the wind or move forward by 
means of propellers4  ,in these         
attempts1 apparatus of several different
 types has been developed4 ,the types   
are classed in two general divisions    
based on their weight relative to that  
of the atmosphere1 viz1 the             
lighter-than-air machines and the       
heavier-than-air machines4              
,lighter-than-air machines are those    
which employ a bag filled with a gas    
whose specific gravity is sufficiently  
less than that of the air to lift the   
bag and the necessary attachments from  
the earth1 and include simple balloons  
and dirigibles4 ,heavier-than-air       
machines1 which will neither rise nor   
remain in the air without motive power1 
include all forms of aeroplanes4        
,,simple ,,balloons   99,theory499 ,the 

balloon-like airship has been more      
highly developed than any other type of 
aerial craft1 probably because it offers
 the most obvious means of overcoming   
the force of gravitation4 ,it depends on
 the law of ,archimedes3  ,every body   
which is immersed in a fluid is acted   
upon by an upward force1 exactly equal  
to the weight of the fluid displaced by 
the immersed body4  ,that is1 a body    
will be at rest if immersed in a fluid  
of equal specific gravity or equal      
weight1 volume for volume2 if the body  
has less specific gravity than the fluid
 in which it is immersed it will rise2  
if it has a greater specific gravity it 
will sink4 ,therefore1 if the total     
weight of a balloon is less than the    
weight of all the air it displaces it   
will rise in the air4 ,it is1 then1     
necessary to fill the balloon with some 
gas whose specific gravity is enough    
less than1 that of the air to make the  
weight of the gas itself1 the bags1 and 
the attachments1 less than the weight of

 the air displaced by the whole         
apparatus4 ,the gases usually employed  
are hydrogen1 coal gas1 and hot air4    
,at atmospheric pressure and freezing   
temperature1 the weight of a cubic foot 
of air is about 4#jh pound2 the weight  
of a cubic foot of hydrogen is about    
4#jje pound1 under the same conditions4 
,according to the law of ,archimedes1 a 
cubic foot of hydrogen would be acted   
upon by a force equal to the difference1
 or approximately 4#jge pound1 tending  
to move it upwards4 ,in the same way1 a 
cubic foot of coal gas1 which weighs    
4#jd pound1 would be acted upon by an   
upward force of 4#jd pound4  ,it is     
evident1 then1 that a considerable      
volume of gas is required to lift a     
balloon with its envelope1 net1 car1 and
 other attachments4  ,further1 it       
requires almost twice as much coal gas  
as hydrogen1 under the same conditions1 
for we have seen that the upward force  
on it is only half as great4 ,the       
lifting power of hot air is less than   

one-eighth as great as that of hydrogen 
at the highest temperature that can     
possibly be used in a balloon4          
,illustration3 ,fig4 #c4 ,montgolfier   
,balloon  ,the general type of          
lighter-than-air machines may be divided
 into aerostats 7ordinary balloons1     
which are entirely dependent on wind    
currents for lateral movement1 and which
 are often the chief features at country
 fairs7 and dirigible balloons or       
aeronats 7air swimmers74 ,dirigible     
balloons employ the gas bag for         
maintaining buoyancy1 and have rudders  
to guide them and propellers to drive   
them forward through the air in much the
 same way that ships are driven through 
the water4  99,the ,first ,balloon499   
,for several years1 ,joseph and ,steven 
,montgolfier had been experimenting with
 a view to constructing a balloon3 in   
the first place by filling bags with    
steam2 then by filling bags with smoke1 
and finally by filling bags with        
hydrogen4 ,these attempts were all      

failures1 for the steam rapidly         
condensed and the smoke and hydrogen    
leaked through the pores in the bags4   
,they finally hit upon the idea of      
filling the bag with hot air1 by means  
of a fire under its open mouth4 ,several
 balloons were burned up1 but the next  
was always made larger1 until1 at their 
first public exhibition on ,june #e1    
#aghc1 the bag had become over #ce feet 
in diameter4 ,on this occasion1 it rose 
to a height of between #ijj and #a1jjj  
feet1 but the hot air was gradually     
escaping1 and at the end of ten minutes 
the balloon fell to the ground4  ,the   
,montgolfiers then went to ,paris1      
where1 after suffering the loss of a    
paper balloon by rain1 they sent up a   
waterproofed linen one carrying a sheep1
 a duck1 and a rooster in a basket4 ,a  
rupture in the linen caused the three   
unwilling aeronauts to make a landing at
 the end of about ten minutes4 ,the     
,montgolfiers received great honor1 and 
small balloons of this type became a    

popular fad4 ,one of these balloons is  
shown in ,fig4 #c1 making an ascension4 
99,rozier499 ,the first man to go up in 
a balloon was ,rozier1 who ascended in a
 captive balloon to a height of about   
#hj feet1 in the latter part of the year
 #aghc4 ,later1 in company with a       
companion1 he made a voyage in a free   
balloon1 remaining in the air about half
 an hour4 ,in these balloons1 the air   
within was kept hot by means of a fire  
carried in a pan immediately below the  
mouth of the bag1 as shown in ,fig4 #d4 
,accidents were numerous on account of  
the fabric becoming ignited from the    
fire in the pan4  ,illustration3 ,fig4  
#d4 ,rozier ,hot-,air ,balloon          
99,improvements by ,charles499 ,the     
physicist1 ,charles1 was working along  
these lines at the same time4 ,he coated
 his balloon with a rubber solution to  
close up the pores1 and was thereby     
enabled to substitute hydrogen for the  
hot air4 ,shortly after the             
,montgolfiers' first public exhibition1 

,charles sent up his balloon for the    
benefit of the ,academie des ,sciences  
in ,paris4 ,the balloon1 which weighed  
about #ai pounds1 ascended rapidly in   
the air and disappeared in the clouds1  
where it burst and fell in a suburb of  
the city4 ,the impression produced upon 
the peasants at seeing it fall from the 
heavens was hardly different from what  
could be expected4 ,they believed it to 
be of devilish origin1 and immediately  
tore it into shreds4 ,charles           
subsequently built a large balloon quite
 similar to those in use today4 ,a net  
was used to support the basket1 and a   
valve1 operated by means of ropes from  
the basket1 was arranged at the top to  
permit the gas to escape as desired4    
99,the ,balloon ,successful499 ,the     
,english ,channel was first crossed in  
#aghe4 ,blanchard1 an ,englishman1 and  
,jeffries1 an ,american1 started from   
,dover on ,january #g in a balloon      
equipped with wings and oars4 ,after a  
very hazardous voyage1 during which they

 had to cast overboard everything       
movable to keep from drowning1 they     
landed in triumph on the ,french coast4 
,an attempt to duplicate this feat was  
made shortly afterward by ,rozier4 ,he  
constructed a balloon filled with       
hydrogen1 below which hung a receiver in
 which air could be heated4 ,he hoped to
 replace by the hot air the losses due  
to leakage of hydrogen4 ,soon after the 
start the balloon exploded1 due to the  
escaping gas reaching the fire1 and     
,rozier and his companion were dashed on
 the cliffs and killed4    ,,early      
,,dirigibles   99,meusnier the          
,pioneer499 ,the fact that the invention
 of the dirigible balloon and means of  
navigating it were almost simultaneous  
is very little known today and much less
 appreciated4 ,like the aeroplane1 its  
development was very much retarded by   
the lack of suitable means of           
propulsion1 and the actual history of   
what has been accomplished in this field
 dates back only to the initial circular

 flight of ,la ,france in #ahhe4 ,still 
the principles upon which success has   
been achieved were laid down within a   
year of the appearance of ,montgolfier's
 first gas bag4 ,lieutenant ,meusnier1  
who subsequently became a general in the
 ,french army1 must really be credited  
with being the true inventor of aerial  
navigation4 ,at a time when nothing     
whatever was known of the science1      
,meusnier had the distinction of        
elaborating at one stroke all the laws  
governing the stability of an airship1  
and calculating correctly the conditions
 of equilibrium for an elongated        
balloon1 after having strikingly        
demonstrated the necessity for this     
elongation4 ,this was in #agha and      
,meusnier's designs and calculations are
 still preserved in the engineering     
section of the ,french ,war ,office in  
the form of drawings and tables4  ,but  
as often proved to be the case in other 
fields of research1 his efforts went    
unheeded4 ,how marvelous the            

establishment of these numerous         
principles by one man in a short time   
really is1 can be appreciated only by   
noting the painfully slow process that  
has been necessary to again determine   
them1 one by one1 at considerable       
intervals and after numerous failures4  
,through not following the lines which  
he laid down1 aerial navigation lost a  
century in futile groping about2 in     
experiments absolutely without method or
 sequence4  ,illustration3 ,fig4 #e4    
,meusnier ,dirigible ,balloon           
,meusnier's designs covered two         
dirigible balloons and that he fully    
appreciated the necessity for size is   
shown by the dimensions of the larger1  
which unfortunately was never built4    
,this was to be #bfj feet long by #acj  
feet in diameter1 in the form of an     
ellipse1 the elongation being exactly   
twice the diameter4 ,in other words1 a  
perfect ellipsoid1 which was a logical  
and1 in fact1 the most perfect          
development of the spherical form4      

,although increased knowledge of wind   
resistance and the importance of the    
part it plays has proved his relative   
dimensions to be faulty1 a study of the 
principal features of his machine shows 
that he anticipated the present-day     
dirigible of the most successful type at
 practically every point1 barring1 of   
course1 the motive power1 as there was  
absolutely nothing available in that day
 except human effort4 ,as the latter    
weighs more than one-half ton per       
horse-power1 it goes without saying that
 ,meusnier's balloon would have been    
dirigible only in a dead calm4  ,he     
adopted the elongated form1 conceived   
the girth fastening1 the triangular or  
indeformable suspension1 the air        
balloonet and its pumps1 and the screw  
propeller1 all of which are to be found 
in the dirigibles of present-day ,french
 construction1 ,fig4 #e4 ,it need       
scarcely be added that the ,french have 
not only devoted a greater amount of    
time and effort to the development of   

the dirigible than any other nation1 but
 have also met with the greatest success
 in its use4 ,it was not until #ahhf1 or
 more than a century after ,meusnier had
 first elaborated those principles1 that
 their value became known4 ,they were   
set forth by ,lieutenant ,letourne1 of  
the ,french engineers1 in a paper       
presented to the ,academie des ,sciences
 by ,general ,perrier4  ,in one form or 
another1 the salient features of        
,meusnier's dirigible will be found     
embodied in the majority of attempts of 
later days4 ,his large airship was      
designed to consist of double envelope1 
the outer container of which was to     
provide the strength necessary1 and it  
was accordingly reinforced by bands4    
,the inner envelope was to provide the  
container for the gas and was not called
 upon to support any weight4 ,this inner
 bag or balloon proper was designed to  
be only partially inflated and the space
 between1 the two was to be occupied by 
air which could be forced into it at two

 points at either end1 by pumps1 so as  
to maintain the pressure on the gas bag 
uniform regardless of the expansion or  
contraction of its contents4 ,here in   
principle was the air balloonet of      
today4 ,instead of employing a net to   
hang the car from the outer envelope1   
the former was attached by means of a   
triangular suspension system fastened to
 a heavy rope band1 or girth1 encircling
 the outer envelope4 ,at the three      
points where the lifting rope members   
met1 a shaft running the length of the  
car and carrying what ,meusnier         
described as revolving oars was         
installed4 ,these constituted the       
prototype of the screw propeller1       
invented for aerial navigation at a time
 long antedating the use of steam for   
marine use4 ,thus he devised3 7#a7 ,the 
air balloonet to husband the gas supply 
and thus prevent the deformation of the 
outer container or support1 as well as  
to provide stability2 7#b7 the          
triangular suspension to attain         

longitudinal stability2 and 7#c7 the    
screw propeller for propulsion1 beside  
selecting the proper location for the   
latter4    ,,problems ,,of ,,the        
,,dirigible   99,ability to ,float499   
,if ability to rise in the air depended 
merely upon a knowledge of the principle
 that made it possible1 it undoubtedly  
would have been accomplished many       
centuries ago4 ,as already mentioned1   
,archimedes established the fact that a 
body upon floating in a fluid displaces 
an amount of the latter equal in weight 
to the body itself1 and upon this theory
 was formulated the now well-known law1 
that every body plunged into a fluid is 
subjected by this fluid to a pressure   
from below1 equivalent to the weight of 
the fluid displaced by the body4        
,consequently1 if the weight of the     
latter be less than that of the fluid it
 displaces1 the body will float4 ,it is 
by reason of this that the iron ship    
floats and the fish swims in water4 ,if 
the weight of the body and the displaced

 water be the same1 the body will remain
 in equilibrium in the water at a       
certain level1 and if that of the body  
be greater1 it will sink4 ,all three of 
these factors are found in the fish1    
which1 with the aid of its natatory     
gland1 can rise to the surface1 sink to 
the bottom1 or remain suspended at      
different levels4 ,to accomplish these  
changes of specific gravity1 the fish   
fills this gland with air1 dilating it  
until full1 or compressing and emptying 
it4 ,in this we find a perfect analogy  
to the air balloonet of the dirigible1  
which serves the same purposes4 ,the    
method by which lifting power is        
obtained in the dirigible is exactly the
 same as in the case of the balloon4    
,but once in the air1 a balloon is1 to  
all intents and purposes1 a part of the 
atmosphere4 ,there is absolutely no     
sensation of movement1 either vertically
 or horizontally4 ,the earth appears to 
drop away from beneath and to sweep by  
horizontally1 and regardless of how     

violently the wind may be blowing1 the  
balloon is always in a dead calm because
 it is really part of the wind itself   
and is traveling with it at exactly the 
same speed4 ,if it were not for the loss
 of lifting power through the expansion 
and contraction of the gas1 making it   
necessary to permit its escape in order 
to avoid rising to inconvenient heights 
on a very warm day1 and the sacrifice of
 ballast to prevent coming to earth at  
night1 the ability of a balloon to stay 
up would be limited only by the         
endurance of its crew and the quantity  
of provisions it was able to transport4 
,as the use of air balloonets in the    
dirigible takes care of this1 the       
question of lifting power presents no   
particular difficulty4 ,it is only a    
matter of providing sufficient gas to   
support the increased weight of the car1
 motor and its accessories1 and the crew
 of the larger vessel1 with a factor of 
safety to allow for emergencies1 in     
order to permit of staying in the air   

long enough to make a protracted voyage4
  99,air ,resistance vs4 ,speed499      
,unless a voyage is to be governed in   
its direction entirely by the wind1 the 
dirigible must possess a means of moving
 contrary to the latter4 ,the moment    
this is attempted1 resistance is        
encountered1 and it is this resistance  
of the air that is responsible for the  
chief difficulties in the design of the 
dirigible4 ,to drive it against the     
wind1 it must have power2 to support the
 weight of the motor necessary1 the size
 of the gas bag must be increased4 ,but 
with the increase in size1 the amount of
 resistance is greatly multiplied and   
the power to force it through the air   
must be increased correspondingly4 ,the 
law is approximately as follows3  ,where
 the surface moves in a line            
perpendicular to its plane1 the         
resistance is proportional to the extent
 of the surface1 to the square of the   
speed with which the surface is moved   
through the air1 and to a coefficient1  

the mean value of which is #j4abe4      
,this coefficient is a doubtful factor1 
the figure given having been worked out 
years ago in connection with the        
propulsion of sailing vessels4 ,its     
value varies according to later         
experimenters between 4#jh and 4#af1 the
 mean of the more recent investigations 
of ,renard1 ,eiffel1 and others who have
 devoted considerable study to the      
matter1 being 4#jh4 ,this is dwelt upon 
more in detail under ,aerodynamics and  
it will be noted that the values of the 
coefficient ,k1 given here1 do not agree
 with those stated in that article4     
,they serve1 however1 to illustrate the 
principles in question4  ,in accordance 
with this law1 doubling the speed means 
quadrupling the resistance of the air4  
,for instance1 a surface of #af square  
feet moving directly against the air at 
a speed of #aj feet per second will     
encounter a resistance of #af ,x #ajj   
7square of the speed7 ,x #j4abe  #bjj   
pounds pressure4 ,doubling the speed1   

thus bringing it up to #bj feet per     
second1 would give the equation #af ,x  
#djj ,x #j4abe  #hjj pounds pressure1 or
 with the more recent value of the      
coefficient of 4#jh1 #eab pounds        
pressure4 ,the first consideration is   
accordingly to reduce the amount of     
surface moving at right angles4 ,the    
resistance of a surface having tapering 
sides which cut through or divide the   
molecules of air instead of allowing    
them to impinge directly upon it1 is    
greatly diminished2 hence1 ,meusnier's  
principle of elongation4 ,if we take the
 same panel presenting #af square feet  
of surface and build out on it a        
hemisphere1 its resistance at a speed of
 #aj feet per second will be exactly    
half1 or a pressure of #ajj pounds4  ,by
 further modifying this so as to        
represent a sharp point1 or acute-angled
 cone1 it will be #ch pounds4 ,there    
could accordingly be no question of     
attempting to propel a spherical        
balloon4  ,illustration3 ,fig4 #f4      

,giffard ,dirigible  ,it is necessary to
 select a form that presents as small a 
surface as possible to the air as the   
balloon advances1 while preserving the  
maximum lifting power4 ,but experience  
has strikingly demonstrated the analogy 
between marine and aerial practice--not 
only is the shape of the bow of the     
vessel of great importance but1         
likewise1 the stern4 ,the profile of the
 latter may permit of an easy reunion of
 the molecules of air separated by the  
former1 or it may allow them to come    
together again suddenly1 clashing with  
one another and producing disturbing    
eddies just behind the moving body4 ,to 
carry the comparison with a marine      
vessel a bit further1 the form must be  
such as to give an easy shear1 or sweep 
from stem to stern4  ,illustration3     
,fig4 #g4 ,de ,lome ,dirigible  ,that   
early investigators appreciated this is 
shown by the fact that ,giffard in      
#aheb1 ,fig4 #f1 ,de ,lome in #ahgb1    
,fig4 #g1 ,tissandier in #ahhd1 and     

,santos-,dumont in his numerous         
attempts1 adopted a spindle-shaped or   
fusiform balloon4 ,in other words1 their
 shape1 equally pointed at either end1  
was symmetrical in relation to their    
central plan4 ,however1 that the shape  
best adapted to the requirements of the 
bow did not serve equally well for the  
stern1 was demonstrated for the first   
time by ,renard1 to whom credit must be 
given for a very large part of the      
scientific development of the dirigible4
 ,almost a century earlier1             
,marey-,monge had laid down the         
principle that to be successfully       
propelled through the air1 the balloon  
must have the head of a cod and the tail
 of a mackerel4 ,nature exemplifies the 
truth of this in all swiftly moving     
fishes and birds4 ,renard accordingly   
adopted what may best be termed the     
pisciform type1 viz1 that of a          
dis-symmetrical fish with the larger end
 serving as the bow2 and the            
performances of the ,renard1 ,lebaudy1  

and ,clement-,bayard airships have shown
 that this is the most advantageous     
form4  ,the pointed stern prevents the  
formation of eddies and the creation of 
a partial vacuum in the wake which would
 impose additional thrust on the bow4   
,zeppelin has disregarded this factor by
 adhering to the purely cylindrical form
 with short hemispherical bow and stern1
 but it is to be noted that while other 
,german investigators originally        
followed this precedent1 they have      
gradually abandoned it1 owing to the    
noticeable retarding effect4            
99,critical ,size of ,bag499 ,next in   
importance to the best form to be given 
the vessel1 is the most effective       
size--something which has a direct      
bearing upon its lifting power4 ,this   
depends upon the volume1 while the      
resistance is proportional to the amount
 of surface presented4 ,greater lifting 
power can accordingly be obtained by    
keeping the diameter down and increasing
 the length4 ,but the resistance is also

 proportionate to the square of the     
speed1 while the volume1 or lifting     
power1 varies as the cube of the        
dimensions of the container1 so that in 
doubling the latter1 the resistance of  
the vessel at a certain speed is        
increased only four times while its     
lifting capacity is increased eight     
times4 ,consequently the larger         
dirigible is very much more efficient   
than the smaller one since it can carry 
so much more weight in the form of a    
motor and fuel in proportion to its     
resistance to the air4 ,as an           
illustration of this1 assume a          
rectangular container with square ends  
#a foot each way and #e feet long4 ,its 
volume will be #e cubic feet and if the 
lifting power of the gas be assumed as  
#b pounds per cubic foot1 its total     
lifting power will be #e pounds4 ,if a  
motor weighing exactly #e pounds per    
horse-power be assumed1 it will be      
evident that the motor which such a     
balloon could carry would be limited to 

#a horse-power1 neglecting the weight of
 the container4  ,double these          
dimensions and the container will then  
measure #b ,x #b ,x #aj feet1 giving a  
volume of #dj cubic feet1 and a lifting 
power1 on the basis already assumed1 of 
a motor capable of producing #h         
horsepower1 and this without taking into
 consideration that as the size of the  
motor increases1 its weight per         
horse-power decreases4 ,the balloon of  
twice the size will thus have a motor of
 #h horse-power to overcome the         
resistance of the head-on surface of #d 
square feet1 or #b horse-power per      
square foot of transverse section1      
whereas the balloon of half the size    
will have only #a horse-power per square
 foot of transverse section4 ,it is1    
accordingly1 not practicable to         
construct small dirigibles such as the  
various airships built by               
,santos-,dumont for his experiments1    
while1 on the other hand1 there are     
numerous limitations that will be       

obvious1 restricting an increase in size
 beyond a certain point1 as has been    
shown by the experience of the various  
,zeppelin airships4  ,to make it        
serviceable1 what ,berget terms the     
independent speed of a dirigible1 i4e41 
its power to move itself against the    
wind1 must be sufficient to enable it to
 travel under normally prevailing       
atmospheric conditions4 ,these naturally
 differ greatly in different countries  
and in different parts of the same      
country4 ,where meteorological tables   
showed the prevailing winds in a certain
 district to exceed #ae miles an hour   
throughout a large part of the year1 it 
would be useless to construct an airship
 with a speed of #ae miles an hour or   
less for use in that particular         
district1 as the number of days in the  
year in which one could travel to and   
from a certain starting point would be  
limited4 ,this introduces another factor
 which has a vital bearing upon the size
 of the vessel4 ,refer to the figures   

just cited and assume further that by   
doubling the dimensions and making the  
airship capable of transporting a motor 
of #h horse-power1 it has a speed of #aj
 miles an hour4 ,it is desired to double
 this4 ,but the resistance of the       
surface presented increases as the      
square of the speed4 ,hence1 it will not
 avail merely to double the power of the
 motor4 ,experience has demonstrated    
that the power necessary to increase the
 speed of the same body1 increases in   
proportion to the cube of the speed1 so 
that instead of a #af-;horse-power motor
 in the case mentioned1 one of #fd      
horse-power would be needed4 ,there are1
 accordingly1 a number of elements that 
must be taken into consideration when   
determining the size as well as the     
shape of the balloon4  99,static        
,equilibrium499 ,having settled upon the
 size and shape1 there must be an       
appropriate means of attaching the car  
to carry the power plant1 its           
accessories and control1 and the crew4  

,while apparently a simple matter1 this 
involves one of the most important      
elements of the design--that of         
stability4 ,a long envelope of          
comparatively small diameter being      
necessary for the reasons given1 it is  
essential that this be maintained with  
its axis horizontal4 ,in calm air1 the  
balloon1 or container1 is subjected to  
the action of two forces3 ,one is its   
weight1 applied to the center of gravity
 of the system formed by the balloon1   
its car1 and all the supports2 the other
 is the thrust of the air1 applied at a 
point known as the center of thrust and 
which will differ with different        
designs1 according as the car is        
suspended nearer or farther away from   
the balloon4 ,if the latter contained   
only the gas used to inflate it1 with no
 car or other weight to carry1 the      
center of gravity and the center of     
thrust would coincide1 granting that the
 weight of the envelope were negligible4
 ,as this naturally can not be the case1

 these forces are not a continuation of 
each other4 ,but as they must           
necessarily be equal if the balloon is  
neither ascending nor descending1 it    
follows that they will cause the balloon
 to turn until they are a continuation  
of each other1 and in the case of a     
pisciform balloon1 this will cause it to
 tilt downward4 ,like a ship with too   
much cargo forward1 it would be what    
sailors term down at the head4  ,as this
 would be neither convenient nor        
compatible with rapid propulsion1 it    
must be avoided by distributing the     
weight along the car in such a manner   
that when the balloon is horizontal1 the
 forces represented by the pressure     
above and the weight below1 must be in  
the same perpendicular4 ,this is        
necessary to insure static equilibrium1 
or a horizontal position while in a     
state of rest4 ,to bring this about1 the
 connections between the car and the    
balloon must always maintain the same   
relative position1 which is further     

complicated by the fact that they must  
be flexible at the same time4           
99,longitudinal ,stability499 ,but the  
longitudinal stability of the airship as
 a whole must be preserved1 and this    
also involves its stability of          
direction4 ,its axis must be a tangent  
to the course it describes1 if the      
latter be curvilinear1 ,or parallel with
 the direction of this course where the 
course itself is straight4 ,this is     
apparently something which should be    
taken care of by the rudder1 any        
tendency on the part of the airship to  
diverge from its course being corrected 
by the pilot4 ,but a boat that needed   
constant attention to the helm to keep  
it on its course would be put down as a 
cranky--in other words1 of faulty design
 in the hull4 ,a dirigible having the   
same defect would be difficult to       
navigate1 as the rudder alone would not 
suffice to correct this tendency in     
emergencies4 ,stability of direction is1
 accordingly1 provided for in the design

 of the balloon itself1 and this is the 
chief reason for adopting the form of a 
large-headed and slender-bodied fish1 as
 already outlined4 ,this brings the     
center of gravity forward and makes of  
the long tail an effective lever which  
overcomes any tendency of the ship to   
diverge from the course it should       
follow1 by causing the resistance of the
 air itself to bring it back into line4 
,however1 the envelope of the balloon   
itself would not suffice for this1 so   
just astern of the latter1 stabilizing  
surfaces are placed1 consisting of      
vertical planes fixed to the envelope4  
,these form the keel of the dirigible   
and are analogous to the keel of the    
ship4 ,stability of direction is thus   
obtained naturally without having       
constant recourse to the rudder1 which  
is employed only to alter the direction 
of travel4  ,the comparison between     
marine and aerial navigation must be    
carried even further4 ,these vertical   
planes1 or keel1 prevent rolling2 it is 

equally necessary to avoid pitching--far
 more so than in the case of a vessel in
 water4 ,so that while the question of  
stability of direction is intimately    
connected with longitudinal stability1  
other means are required to insure the  
latter4 ,the airship must travel on an  
even keel1 except when ascending or     
descending1 and the latter must be      
closely under the control of the pilot1 
as otherwise the balloon may incline at 
a dangerous angle4 ,this shows the      
importance of an unvarying connection   
between the car and the envelope to     
avoid defective longitudinal stability4 
,assume1 for instance1 that the car is  
merely attached at each end of a single 
line4 ,the car1 the horizontal axis of  
the balloon1 and the two supports would 
then form a rectangle4 ,when in a state 
of equilibrium the weight and the thrust
 are acting in the same line4 ,now      
suppose that the pilot desires to       
descend and inclines the ship downward4 
,the center of gravity is then shifted  

farther forward and the two forces are  
no longer in line4  ,but as the         
connections permit the car to swing in a
 vertical plane1 they permit the latter 
to move forward and parallel with the   
balloon1 thus forming a parallelogram   
instead of a rectangle4 ,this causes the
 center of gravity to shift even        
farther1 and as one of the most serious 
causes of longitudinal stability is the 
movement of the gas itself1 it would    
also rush to the back end and cause the 
balloon to stand on its head4 ,as the   
tendency of the gas is thus to augment  
any inclination accidentally produced1  
the vital necessity of providing a      
suspension that is incapable of         
displacement with relation to the       
balloon is evident4 ,here is where the  
importance of ,meusnier's conception of 
the principle of triangular suspension  
comes in4 ,instead of being merely      
supported by direct vertical connections
 with the balloon1 the ends of the car  
are also attached to the opposite ends  

of the envelope1 forming opposite       
triangles4 ,this gives an unvarying     
attachment1 so that when the balloon    
inclines1 the car maintains its relative
 position1 and the weight and thrust    
tend to pull each other back in the same
 line1 or1 in other words1 to trim ship4
  99,dynamic ,equilibrium499 ,in        
addition to being able to preserve its  
static equilibrium and to possess proper
 longitudinal stability1 the successful 
airship must also maintain its dynamic  
equilibrium--the equilibrium of the     
airship in motion4 ,this may be made    
clear by referring to the well-known    
expedients adopted to navigate the      
ordinary spherical balloon4 ,to rise1   
its weight is diminished by gradually   
pouring sand from the bags which are    
always carried as ballast4 ,to descend1 
it is necessary to increase the total   
weight of the balloon and its car1 and  
the only method of accomplishing this is
 to permit the escape of some of the    
gas1 the specific lightness of which    

constitutes the lifting power of the    
balloon4 ,as the gas escapes1 the thrust
 of the air on the balloon is decreased 
and it sinks--the ascensional effort    
diminishing in proportion to the amount 
of gas that is lost4 ,the balloon1 or   
the container itself1 being merely a    
spherical bag1 on the upper             
hemispherical half of which the net     
supporting the car presses at all       
points1 the question of deformation is  
not a serious one4 ,before it assumed   
proportions where the bag might be in   
danger of collapsing1 the balloon would 
have had to come to earth through lack  
of lifting power to longer sustain it4  
,owing to its far greater size1 as well 
as to the form of the surface which it  
presents to the air pressure1 such a    
crude method is naturally not applicable
 to the dirigible4  ,dynamic equilibrium
 must take into account not only its    
weight and the sustaining pressure of   
the air1 but also the resistance of the 
air exerted upon its envelope4 ,this    

resistance depends upon the dimensions  
and the shape of that envelope1 and in  
calculations the latter is always       
assumed to be invariable4 ,assume1 for  
instance1 that to descend the pilot of a
 dirigible allowed some of the hydrogen 
gas to escape4 ,as the airship came     
down1 it would have to pass through     
strata of air of constantly increasing  
pressure as the earth is approached4    
,the reason for this will be apparent as
 the lower strata bear the weight of the
 entire atmosphere above them4 ,the     
confined gas will no longer be          
sufficient to distend the envelope1 the 
latter losing its shape and becoming    
flabby4 ,as the original form is no     
longer retained1 the center of          
resistance of the air will likewise have
 changed together with the center of    
thrust1 and the initial conditions will 
no longer obtain4 ,but as the           
equilibrium of the airship depends upon 
the maintenance of these conditions1 it 
will be lost if they vary4  99,function 

of ,balloonets499 ,in the function of   
balloonets is realized the importance of
 the principle established by ,meusnier4
 ,it was almost a century later before  
it was rediscovered by ,dupuy de ,lome  
in connection with his attempts to make 
balloons dirigible4 ,that the balloon   
must always be maintained in a state of 
perfect inflation has been pointed out4 
,but gas is lost in descents and to a   
certain extent1 through the permeability
 of the envelope4 ,unless it is         
replaced1 the balloon will be only      
partially inflated4 ,in view of the     
great volume necessary1 it requires no  
explanation to show that it would be    
impossible to replace the gas itself by 
fresh hydrogen carried on the car4 ,it  
would have to be under high pressure and
 the weight of the steel cylinders as   
well as the number necessary to         
transport a sufficient supply would be  
prohibitive4 ,hence1 ,meusnier conceived
 the idea of employing air4 ,but this   
could not be pumped directly into the   

balloon to mix with the hydrogen gas1 as
 the resulting mixture would not only   
still be as inflammable as the former   
alone1 but it would also contain        
sufficient oxygen to create a very      
powerful and infinitely more dangerous  
explosive4 ,this led to the adoption of 
the air balloonet4  ,in principle the   
balloonet consists of dividing the      
interior of the envelope into two cells1
 the larger of which receives the light 
gas while the smaller is intended to    
hold air and terminates in a tube       
extending down to a pump in the car4 ,in
 other words1 a fabric partition        
adjacent to the lower part of the       
envelope inside and subject to          
deformation at will4 ,in actual practice
 it consists of a number of independent 
cells of this kind1 longitudinally      
disposed along the lower half of the    
interior of the envelope4  ,when the    
balloon is completely inflated with     
hydrogen1 as at the beginning of an     
ascent1 these balloonets lie flat       

against the lower part of the envelope1 
exactly like a lining4 ,as the airship  
rises1 the gas expands owing to the     
reduction in atmospheric pressure at a  
higher altitude1 as well as to the      
influence of heat4 ,with the increase in
 pressure1 uniform inflation is         
maintained by the escape of a certain   
amount of gas through the automatic     
valves provided for the purpose4 ,unless
 this took place1 the internal pressure 
might assume proportions placing the    
balloon in danger of blowing up4 ,to    
avoid this1 a pressure gauge            
communicating with the gas compartment  
is one of the most important instruments
 on the control board of the car1 and   
should its reading indicate a failure of
 the automatic valves1 the pilot must   
reduce the pressure by operating a hand 
valve4 ,but as the car descends1 the    
increased external pressure causes a    
recontraction of the gas until it no    
longer suffices to fill the envelope4   
,to replace the loss the air pumps are  

utilized to force air into the air      
balloonets until the sum of the volumes 
of gas and air in the different         
compartments equals the original volume4
 ,in this manner1 the initial           
conditions1 upon which the equilibrium  
of the airship is based1 are always     
maintained4  ,this is not the only      
method of correcting for change in      
volume1 nor of maintaining the          
longitudinal stability of the whole     
fabric1 the importance of which has     
already been detailed1 but experience   
has shown that it is the most practical4
 ,it is possible to give the balloon a  
rigid frame over which the envelope is  
stretched and to attach the car by means
 of a rigid metal suspension1 as in the 
various ,zeppelin airships1 or to take  
it semi-rigid1 as in the ,gross1 another
 ,german type in which ,zeppelin's      
precedent was followed only in the case 
of the suspension4 ,to prevent          
deformation by this means1 the balloon  
is provided with an absolutely rigid    

skeleton of aluminum tubes4 ,this       
framing is in the shape of a number of  
uniform cylindrical sections1 or gas    
compartments1 each one of which         
accommodates an independent balloon1    
while over the entire frame a very      
strong but light fabric constituting the
 outer or protecting envelope is        
stretched taut4 ,the idea of the        
numerous independent balloons is to     
insure a high factor of safety as the   
loss of the entire contents of two or   
three of them through accident would not
 dangerously affect the lifting power of
 the whole4 ,the numerous wrecks which  
attended the landings of these huge     
non-flexible masses during the early    
stages of their development led to the  
provision of some form of shelter       
wherever they were expected to land4    
,even now1 they are practically         
unmanageable in the air during a fierce 
wind and must be allowed to sail under  
control until the wind has spent itself4
  ,the system of air balloonets has     

accordingly been adopted by every other 
designer1 in variously modified forms1  
as illustrated by the ,german dirigible 
,parseval1 in which but two air bags    
were employed1 one at either end4 ,they 
were interconnected by an external tube 
to which the air-pump discharge was     
attached1 and were also operated by a   
counterbalancing system inside the gas  
bag1 by means of which the inflation of 
one balloonet1 as the after one1 for    
example1 caused the collapse of the     
other4  ,influence of ,fish ,form of    
,bag4 ,but a condition of dynamic       
equilibrium can not be obtained with the
 combined aid of the precautions already
 noted to secure longitudinal stability 
and that of the air balloonet in        
maintaining uniform inflation4 ,why this
 is so will be clear from a simple      
example4 ,if a simple fusiform or       
spindle-shaped balloon be suspended in  
the air in a horizontal plane1 the axis 
of which passes through its center of   
gravity1 it would be practically pivoted

 on the latter and would be extremely   
sensitive to influences tending to tilt 
it up or down4 ,it would be in a state  
of indifferent longitudinal equilibrium4
 ,as long as the axis of the balloon    
remains horizontal and the air pressure 
is coincident with that axis1 it will be
 in equilibrium1 but an equilibrium     
essentially unstable4 ,experiment proves
 that the moment the balloon inclines   
from the horizontal in the slightest    
degree1 there is a strong tendency for  
it to revolve about its center of       
gravity until it stands vertical to the 
air current1 or is standing straight up 
and down4 ,this1 of course1 refers to   
the balloon alone without any           
attachments4 ,such a tendency would be  
fatal1 amounting as it does to absolute 
instability4  ,if instead of symmetrical
 form1 tapering toward both ends1 a     
pisciform balloon be tried1 it will     
still evidence the same tendency1 but in
 greatly diminished degree4 ,this is not
 merely the theory affecting its        

stability but represents the findings of
 ,col4 ,charles ,renard1 who undoubtedly
 did more to formulate the exact laws   
governing the stability of a dirigible  
than any other investigator in this     
field4 ,his data is the result of a long
 and methodically carried out series of 
experiments4 ,in the case of the        
pisciform balloon1 the disturbing effect
 is due in unequal degree1 to the       
diameter of the balloon and its         
inclination and speed1 whereas the      
steadying effect depends upon the       
inclination and diameter1 but not on the
 ,speed4 ,the disturbing effect1        
therefore1 depends solely on the speed  
and augments very rapidly as the speed  
increases4 ,it will1 accordingly1 be    
apparent that there is a certain speed  
for which the two effects are equal1 and
 beyond which the disturbing influence1 
depending on speed1 will overcome the   
steadying effect4  ,to this rate of     
travel1 ,renard applied the term        
critical speed1 and when this is        

exceeded the equilibrium of the balloon 
becomes unstable4 ,to obtain this data1 
keels of varying shapes and dimensions  
were submitted to the action of a       
current of air1 the force of which could
 be varied at will4 ,in the case of the 
,la ,france1 the first fish-shaped      
dirigible1 the critical speed was found 
to be #aj meters1 or approximately #ci  
feet per second1 a speed of #ba4f miles 
per hour1 and a #bd-;horse-power motor  
suffices to drive the airship at this   
rate of travel4 ,but the internal       
combustion motor is now so light that a 
dirigible of this type could easily lift
 a motor capable of generating #hj to   
#ajj horse-power4 ,with this amount of  
power1 its theoretic speed would be #ej 
per cent greater1 or #cc miles an hour4 
,but this could not be accomplished in  
practice as long before it was reached  
the stability would become precarious4  
,as ,colonel ,renard observed in the    
instance just cited1 ,if the balloon    
were provided with a #ajj-;horse-power  

motor1 the first #bd horse-power would  
make it go and the other #gf horse-power
 would break our necks4  ,steadying     
,planes4 ,it is accordingly necessary to
 adopt a further expedient to insure    
stability4 ,this takes the form of a    
system of rigid planes1 both vertical   
and horizontal1 located in the axis of  
the balloon and placed a considerable   
distance to the rear of the center of   
gravity4 ,with this addition1 the       
resemblance of the after end of the     
balloon to the feathering of an arrow is
 apparent1 while its purpose is similar 
to that of the latter4 ,for this reason1
 these steadying planes have been termed
 the empennage1 which is the ,french    
equivalent of arrow feathering1 while   
its derivative empennation is employed  
to describe the counteraction of this   
disturbing effect4 ,in the ,la ,france1 
which measured about #bcj feet in length
 by #dj feet in diameter1 the area of   
the planes required to accomplish this  
was #afj square feet1 and the planes    

themselves were placed almost #ajj feet 
to the rear of the center of gravity4   
,by referring to the illustrations of   
the various ,french airships1 the       
various developments in the methods of  
accomplishing this will be apparent4    
,illustration3 ,fig4 #h4 ,la ,ville de  
,paris ,showing ,balloonets  ,in the    
,lebaudy balloon1 it took the form of   
planes attached to the framework between
 the car and the balloon4 ,in ,la       
,patrie and ,la ,republique1 the        
resemblance to the feathered arrow was  
completed by attaching four planes in   
the form of a cross directly to the     
stern of the balloon itself4 ,but as    
weight1 no matter how slight1 is a      
disturbing factor at the end of a long  
lever1 such as is represented by the    
balloon1 ,renard devised an improvement 
over these methods by conceiving the use
 of hydrogen balloonets as steadying    
planes4 ,the idea was first embodied in 
,la ,ville de ,paris1 ,fig4 #h1 in the  
form of cylindrical balloonets1 and as  

conical balloonets on the               
,clement-,bayard4 ,these balloonets     
communicate with the gas chamber proper 
of the balloon and consequently exert a 
lifting pressure which compensates for  
their weight1 so that they no longer    
have the drawback of constituting an    
unsymmetrical supplementary load4       
99,location of ,propeller499 ,the final 
factor of importance in the design of   
the successful dirigible is the proper  
location of the propulsive effort with  
relation to the balloon4 ,theoretically1
 this should be applied to the axis of  
the balloon itself1 as the latter       
represents the greater part of the      
resistance offered to the air4 ,at least
 one attempt to carry this out in       
practice resulted disastrously1 that of 
the ,brazilian airship ,pax1 while the  
form adopted by ,rose1 in which the     
propeller was placed between the twin   
balloons in a plane parallel with their 
horizontal axes1 was not a success4 ,in 
theory1 the balloon offers such a       

substantial percentage of the total     
resistance to the air that the area of  
the car and the rigging were originally 
considered practically negligible by    
comparison4 ,actually1 however1 this is 
not the case4 ,calculation shows that in
 the case of any of the typical ,french 
airships mentioned1 the sum of the      
surface of the suspending rigging alone 
is easily the equivalent of #b square   
meters1 or about #ba square feet1       
without taking into consideration the   
numerous knots1 splices1 pulleys1 and   
ropes employed in the working of the    
vessels1 air tubes communicating with   
the air balloonets1 and the like4 ,add  
to this equivalent area that of the     
passengers1 the air pump1 other         
transverse members and exposed surfaces1
 and the total will be found equivalent 
to a quarter or even a third of the     
transverse section of the balloon       
itself4  ,to insure the permanently     
horizontal position of the ship under   
the combined action of the motor and the

 air resistance1 a position of the      
propeller at a point about one-third of 
the diameter of the balloon below its   
horizontal axis will be necessary4      
,without employing a rigid frame like   
that of the ,zeppelin and the ,pax1     
however1 such a location of the shaft is
 a difficult matter for constructional  
reasons4 ,consequently1 it has become   
customary to apply the driving effort to
 the car itself1 as no other solution of
 the problem is apparent4 ,this accounts
 for the tendency common in the         
dirigible to float high forward1 and    
this tilting becomes more pronounced in 
proportion to the distance the car is   
hung beneath the balloon4 ,the term     
deviation is employed to describe this  
tilting effect produced by the action of
 the propeller4 ,conflicting            
requirements are met with in attempting 
to reduce this by bringing the car      
closer to the balloon as this           
approximation is limited by the danger  
of operating the gasoline motor too     

close to the huge volume of inflammable 
gas4 ,the importance of this factor may 
be appreciated from the fact that if the
 car were placed too far from the       
balloon1 the propulsive effect would    
tend to hold the latter at an angle     
without advancing much1 owing to the    
vastly increased air resistance of the  
much larger surface thus presented4     
99,relations of ,speed and ,radius of   
,travel499 ,the various factors         
influencing the speed of a dirigible    
have already been referred to1 but it   
will be apparent that the radius of     
action is of equally great importance4  
,it is likewise something that has a    
very direct bearing upon the speed and1 
in consequence1 upon the design as a    
whole4 ,it will be apparent that to be  
of any great value for military or other
 purposes1 the dirigible must possess   
not only sufficient speed to enable it  
to travel to any point of the compass   
under ordinarily prevailing conditions  
of wind and weather but also to enable  

it to remain in the air for some time   
and cover considerable distance under   
its own power4  ,total ,weight per      
,horsepower ,hour4 ,as is the case in   
almost every point in the design of the 
dirigible1 conflicting conditions must  
be reconciled in order to provide it    
with a power plant affording sufficient 
speed with ample radius of action4 ,it  
has already been pointed out that power 
requirements increase as the cube of the
 speed1 making a tremendous addition    
necessary to the amount of power to     
obtain a disproportionately small       
increase in velocity4 ,in this          
connection there is a phase of the motor
 question that has not received the     
attention it merits up to the present   
time4 ,the struggle to reduce weight to 
the attainable minimum has made weight  
per horsepower apparently the paramount 
consideration--a factor to which other  
things could be sacrificed4 ,and this is
 quite as true of aeroplane motors as   
those designed for use in the dirigible4

 ,but it is quite as important to make  
the machine go as it is to make it rise 
in the air1 so that the question of     
total weight per horsepower hour has led
 to the abandonment of extremely light  
engines requiring a great deal of fuel4 
,speed is quite as costly in an airship 
as it is in an ,atlantic liner4 ,to     
double it1 the motor power must be      
multiplied by #h1 and the machine must  
carry #h times as much fuel4 ,but by    
cutting the power in half1 the speed is 
reduced only one-fifth4 ,the problem of 
long voyages in the dirigible is1       
accordingly1 how to reconcile best the  
minimum speed which will enable it to   
make way effectively against the        
prevailing winds1 with the reduction in 
power necessary to cut the fuel         
consumption down to a point that will   
insure a long period of running4  ,when 
the speed of the dirigible is greater   
than that of the prevailing wind1 it may
 travel in any direction2 when it is    
considerably less1 it can travel only   

with the wind2 when it is equal to the  
speed of the latter1 it may travel at an
 angle with the wind--in other words1   
tack1 as a ship does1 utilizing the     
pressure of the contrary wind to force  
the ship against it4 ,but as the air    
does not offer to the hull of the       
airship1 the same hold that water does  
to that of the seagoing ship1 the amount
 of leeway or drift in such a manoeuver 
is excessive4 ,this applies quite as    
much to the aeroplane as it does to the 
dirigible4    ,,french ,,dirigibles     
99,the ,first ,lebaudy499 ,the interest 
evidenced by the ,german ,war           
,department in ,zeppelin's airship was  
more than duplicated by that aroused in 
,french military circles by the success 
of the ,lebaudy ,brothers4 ,since #aijj 
these two brothers had been             
experimenting with dirigible balloons4  
,their first dirigible--built by the    
engineer ,juillot--made thirty flights1 
in all but two of which it succeeded in 
returning to its starting point4 ,this  

machine was somewhat similar to the     
later types built by ,santos-,dumont and
 carried a #dj-;horsepower ,daimler     
motor4 ,a speed of #cf feet per second1 
or about #be miles per hour1 was        
obtained4 ,during tests in the summer of
 #aijd1 the balloon was dashed against a
 tree and almost entirely destroyed4    
99,lebaudy #aijd499 ,the next year the  
,lebaudy #aijd appeared4 ,this was #aij 
feet long and had a capacity of #id1jjj 
cubic feet of gas4 ,the air bag was     
divided into three parts and contained  
#ag1fjj cubic feet of air4 ,it was      
supplied with air from a fan driven by  
the engine1 and an auxiliary electric   
motor and storage battery were carried  
to drive the fan when the gas engine was
 not working4 ,the storage battery was  
also used to furnish electric lights for
 the airship4 ,a horizontal sail of silk
 was stretched between the car and the  
gas bag1 which had an area of something 
over #a1jjj square feet1 and a sort of  
keel of silk was stretched below it4 ,a 

horizontal rudder1 shaped like a        
pigeon's tail1 was used at the rear1 and
 immediately behind it were two         
,v-shaped vertical rudders4 ,a small    
vertical sail was carried1 which could  
be used to assist in guiding the        
airship4 ,the car was #af feet long and 
was rigidly hung #aj feet below the bag4
 ,it was provided with an inverted      
pyramid of steel tubes meeting at an    
apex below the car to prevent injury in 
alighting4 ,sixty-three ascents were    
made in #aijd with this balloon1 all of 
them comparatively successful1 the      
longest being a journey of #fj miles in 
two hours and forty-five minutes4       
,illustration3 ,fig4 #i4 ,la ,patrie1   
,french ,war ,dirigible  ,the next year 
a new and larger balloon equipped with a
 more powerful motor was used4 ,many    
flights were made in tests for the      
,french ,war ,department4  99,la        
,patrie499 ,la ,patrie was then built   
for the ,french government by the       
,lebaudy ,brothers and was of the same  

design as their earlier airships4 ,in   
speed it was nearly equal to            
,zeppelin's1 and its dirigibility was   
nearly perfect4 ,fig4 #i shows a view of
 this airship in flight4  ,it was #bjj  
feet long1 and the #gj-;horsepower      
engine drove two propellers4 ,it could  
carry seven people and one-half ton of  
ballast4 ,it carried four people at a   
speed of #cj miles per hour4 ,on its    
last trip it covered #age miles in seven
 hours4 ,a few days afterward1 a heavy  
wind tore it away from its moorings and 
it was blown out to sea and lost4  99,la
 ,republique and ,le ,jaune499 ,two more
 airships of the same type1 ,la         
,republique and ,le ,jaune1 followed    
this4 ,these were tried by the ,french  
government1 in #aijh1 and both proved   
successful4 ,la ,republique is          
illustrated in ,fig4 #aj4 ,the shape and
 equipment of the car are shown in ,fig4
 #aa4 ,the automobile type of radiator  
may be seen attached to the side of the 
car4 ,during a flight in the fall of    

#aiji1 a propeller blade broke and was  
thrown clear through the balloon        
envelope1 causing the balloon to fall   
from a height of #ejj feet4 ,the four   
officers who formed the crew of the     
dirigible were killed instantly4        
99,clement-,bayard ,,ii499 ,the numerous
 factors that must be considered in the 
design of a successful dirigible balloon
 as well as the many conflicting        
conditions that must be reconciled have 
already been referred to in detail4 ,how
 these are carried out in practice may  
best be made clear by a description of  
what may be considered as an advanced   
type of dirigible1 the ,clement-,bayard 
,,ii1 ,fig4 #ab1 of ,french design1 and 
the most successful of the ,french      
military air fleet4 ,its predecessor1   
the ,clement-,bayard ,i1 ,fig4 #ac1 made
 thirty voyages1 some of them of        
considerable distances1 without         
suffering any damage1 but a study of its
 shortcomings led to their elimination  
in the following model4  ,illustration3 

,fig4 #aj4 ,la ,republique1 ,french ,war
 ,dirigible  ,illustration3 ,fig4 #aa4  
,car of ,la ,republique  ,the pisciform 
shape of the first ,clement-,bayard was 
retained but given more taper1 the      
dimensions being #bdh4f feet overall by 
#db4i greatest diameter1 this being but 
a short distance back of the bow4 ,this 
gives it a ratio of length to diameter  
of #e4gf4 ,the gas balloonet stabilizers
 were eliminated altogether1 ,fig4 #ab4 
,the total gas capacity is approximately
 #hj1jjj cubic feet4 ,like all ,french  
dirigibles it is of the true flexible   
type1 the only rigid construction being 
that of the framework of the car itself4
 ,to the latter are attached all rudders
 and stabilizing devices1 instead of    
making them a part of the envelope as   
formerly4 ,the latter is made of        
continental rubber cloth4               
,illustration3 ,fig4 #ab4               
,clement-,bayard ,,ii1 ,french          
,dirigible  ,light steel and aluminum   
tubing are employed in the construction 

of the frame supplemented by numerous   
piano-wire stays4 ,this frame extends   
almost the entire length of the envelope
 and carries at its rear end a cellular1
 or box-kite1 type of stabilizing       
rudder1 instead of the former gas       
balloonets employed on the              
,clement-,bayard ,i1 ,fig4 #ac4 ,this   
cellular rudder is in two parts1        
consisting of two units of four cells   
each1 the two groups being joined at the
 top1 with a space between them4 ,in    
addition to acting as a stabilizer1 this
 is also the direction rudder1 its      
leverage being increased by making the  
end planes somewhat larger than the     
partitions of the cells4 ,between the   
cellular stabilizing rudder and the     
envelope is placed the horizontal rudder
 for ascending or descending4 ,in the   
illustration this appears to be a flag1 
but it is in reality a long rectangular 
plane1 which may be tilted on its       
longitudinal axis1 the latter being at  
right angles to that of the balloon4    

,there are two air balloonets of about  
one-third the total capacity of the     
balloon itself1 and they are designed to
 be inflated by large aluminum          
centrifugal blowers driven from the main
 engines themselves4  ,illustration3    
,fig4 #ac4 ,clement-,bayard ,i  ,there  
are two motors1 each of #abe horsepower1
 both being of the same conventional    
design1 i4e41 four cylinder four cycle  
vertical water cooled4 ,in fact1 they   
are merely light automobile motors4 ,the
 cylinders have separate copper water   
jackets and the motors themselves are   
muffled1 which is a departure from the  
usual custom4 ,each drives a separate   
propeller carried on top of the main    
frame through bevel gearing4  ,the      
,clement-,bayard ,,ii made itself famous
 by its rapid and successful flight from
 the suburbs of ,paris across the       
,channel to ,london1 in ,october1 #aiaj4
  99,astra-,torres499 ,in reviewing the 
specifications of any of the big        
dirigibles1 the observer cannot fail to 

be struck by the excessive amount of    
power necessary to drive them at speeds 
which are lower than the minimum1 or    
landing speeds1 of many aeroplanes4     
,when a speed of #de miles per hour was 
first reached by a dirigible1 it was    
acclaimed as a great feat4 ,but this    
comparatively moderate rate of travel   
was surpassed only by increasing the    
number of motors and their horsepower   
until the fuel consumption became       
exceedingly high4 ,this necessitated the
 carrying of a great weight of fuel and 
cut down correspondingly the useful load
 that the dirigible was capable of      
lifting as well as restricted its radius
 of flight at full speed4 ,until        
aerodynamic research had demonstrated   
the contrary1 the necessity for such a  
tremendous amount of power was          
considered necessary to overcome the    
head resistance of the balloon itself4  
,research brought out in a striking     
manner how great a proportion of the    
total head resistance of an aeroplane   

was due to the struts and bracing wires4
 ,in the construction of the different  
types of airships illustrated1 it will  
be noted that the gear provided for     
suspending the car or cars below the    
balloon requires a great number of      
cables4 ,later developments showed that 
by eliminating the great amount of head 
resistance caused by these numerous     
surfaces1 the speed of a dirigible could
 be increased by over #ej per cent with 
the same amount of power4               
,illustration3 ,fig4 #ad4 ,section of   
,astra-,torres1 ,illustrating ,method of
 ,suspension4 ,,cb1 ,bracing of ,heavy  
,fabric ,bands2 ,,sr and ,a1 ,suspension
 ,ropes and ,cable ,passing through     
,envelope2 ,s1 ,expansion ,sleeve in    
,envelope2 ,,cc'1 ,ropes to ,sides of   
,car2 ,e1 ,envelope  ,improved          
,suspension4 ,the shortcoming of the    
dirigible with reference to suspension  
was realized more than ten years        
previous by a ,spaniard--,torres--but   
owing to lack of financial support1 he  

was unable to put his idea into         
execution4 ,the principle he evolved is 
made clear by ,fig4 #ad1 which gives a  
section of an ,astra-,torres dirigible  
illustrating the method of suspension4  
,instead of the ropes ,,sr used to      
suspend the car being attached to bands 
passing around the envelope1 these      
reinforcing bands ,,cb and also the     
ropes fastened to them are placed inside
 the envelope1 thus eliminating head    
resistance from those sources4          
,performance4 ,failing to obtain any    
encouragement in ,spain1 ,torres finally
 succeeded in interesting the ,french   
,astra ,company1 which built a vedette1 
or scouting airship1 of a little over   
#ej1jjj cubic feet capacity4 ,it was    
pitted against the ,colonel ,renard1 at 
that time the leading unit in the       
,french aerial navy and the fastest     
airship in commission4 ,the small       
,torres dirigible so completely         
outclassed its huge competitor that     
another of close to #cjj1jjj cubic feet 

capacity was built and tried against the
 ,parseval with similar results4 ,an    
,astra-,torres dirigible built for the  
,british government showed a speed in   
excess of #ej miles per hour4 ,this     
particular dirigible has been at the    
front in ,france almost since the       
outbreak of hostilities and has rendered
 considerable valuable service4 ,its    
success led the ,french ,government to  
order a huge replica of it1 having a    
capacity of over #hjj1jjj cubic feet and
 with motors developing #a1jjj          
horsepower1 which would give it an      
indicated speed of #fj miles per hour4  
,so confident were its builders of      
attaining or even exceeding this1 that  
an order for a second and even larger   
airship of the ,astra-,torres design was
 placed before the first one was        
finished4 ,this is also fitted with     
motors aggregating #a1jjj horsepower and
 displaces #ch tons1 making it larger   
than any ,zeppelin that had been        
constructed up to the time it was built4

 ,as its construction and trials were   
undertaken during the war1 no details   
have been published1 but it is said on  
good authority that its speed exceeds   
#fj miles per hour1 so that it is faster
 than any of the ,german dirigibles4    
,construction4 ,unlike the ,german      
dirigibles1 the larger types of which   
have been characterized by a rigid      
frame1 the ,astra-,torres is a flexible 
airship and1 owing to its method of     
suspension1 its external appearance is  
decidedly unconventional1 since the     
envelope instead of being of the usual  
cigar shape is more like a triangular   
bundle of three cigars with the third   
one on top4 ,at the point where the     
three envelopes join1 as shown in       
section1 ,fig4 #ad1 heavy cloth bands   
,,cb are stretched across the arcs1     
forming a chord across each arc1 the    
three chords comprising an inverted     
triangle4 ,the suspension ropes ,,sr are
 attached to the opposite ends of the   
base of this inverted triangle and      

converge in straight lines downward     
through the gas space1 so that the air  
resistance offered by the ropes is      
practically eliminated since only a very
 small part of the suspension system    
appears outside the envelope4 ,this     
external part consists of vertical      
cables ,a attached to the collecting    
rings of the bracing system and         
extending downward through special      
accordion sleeves ,s which permit the   
free play necessary at the points where 
they pass through the outer wall of the 
envelope4 ,these sleeves also have      
another function--that of permitting the
 escape of gas under the pressure of    
expansion4 ,a short distance below the  
envelope ,e each of these cables splits 
into two parts ,c and ,c' attached to   
opposite sides of the car4  ,the        
,british airship mentioned is provided  
with but one car1 but the larger ,french
 ships have two placed tandem1 each of  
which carries a #ejj-;horsepower motor  
driving two two-bladed propellers of    

large diameter4 ,while the form of      
envelope made necessary by this         
construction increases the frictional   
resistance1 this is negligible in       
comparison with the great saving in     
power effected by the method of         
suspension1 not to mention the greater  
simplicity of construction4    ,,german 
,,dirigibles   99,early ,zeppelin       
,airships499 ,at the same time that     
,santos-,dumont was carrying on his     
hazardous experiments1 the problem was  
being attacked along slightly different 
lines by ,count ,zeppelin4  ,it will be 
remembered that ,dumont experienced much
 trouble on account of the envelope of  
his balloon being too flexible1 causing 
it to crumple in the middle and to      
become distorted in shape from the      
pressure of the air4 ,his efforts to    
overcome this by the employment of air  
bags did not meet with great success1   
even in his later types4  ,illustration3
 ,fig4 #ae4 ,zeppelin ,dirigible ,rising
 from ,lake ,constance  ,construction4  

,zeppelin employed a very rigid         
construction4 ,his first balloon1 which 
was built in #ahih1 was the largest     
which had ever been made4 ,it is        
illustrated in ,fig4 #ae1 which shows   
his first design slightly improved4 ,it 
was about #dj feet in diameter and #dbj 
feet long--an air craft as large as many
 an ocean vessel4 ,the envelope         
consisted of two distinct bags1 an outer
 and an inner one1 with an air space    
between4 ,the air space between the     
inner and outer envelopes acted as a    
heat insulator and prevented the gas    
within from being affected by rapid     
changes of temperature4 ,the inner bag  
contained the gas1 and the outer one    
served as a protective covering4 ,in the
 construction of this outer bag lies the
 novelty of ,zeppelin's design4 ,a rigid
 framework of strongly braced aluminum  
rings was provided and this was covered 
with linen and silk which had been      
specially treated to prevent leakage of 
gas4 ,the inner envelope consisted of   

seventeen gas-tight compartments which  
could be filled or emptied separately4  
,in the event of the puncture of one of 
them1 the balloon would remain afloat4  
,an aluminum keel was provided to       
further increase the rigidity4 ,a       
sliding weight could be moved backward  
or forward along the keel and cause the 
nose of the airship to point upward or  
downward as desired4 ,this would make   
the craft move upward or downward       
without throwing out ballast or losing  
gas4 ,lender each end of the balloon a  
light aluminum car was rigidly fastened 
and in each was a #af-;horsepower       
,daimler gasoline engine4 ,the two      
engines could be worked either          
independently of each other or together4
 ,each engine drove a vertical and      
horizontal propeller4 ,the propellers   
each had four aluminum blades4 ,as will 
be seen from ,fig4 #ae1 the ears were   
too far apart for ordinary means of     
communication and so speaking tubes1    
electric bells1 and an electric         

telegraph system were installed4  ,first
 ,trials4 ,very little was known as to  
the effects of alighting on the ground  
with such a rigid affair as this vessel1
 therefore the cars were made like boats
 so that the airship could alight and   
float on the water4 ,the first trials   
were made over ,lake ,constance in      
,july1 #aijj4 ,the mammoth craft was    
housed in a huge floating shed1 and the 
vessel emerged from it with the gas bag 
floating above and the two cars touching
 the water4 ,she rose easily from the   
water1 and then began a series of       
mishaps such as usually fall to the lot 
of experimenters4 ,the upper cross stay 
proved too weak for the long body of the
 balloon and bent upward about #aj      
inches during the flight4 ,this         
prevented the propeller shafts from     
working properly4 ,then the winch which 
worked the sliding weight was broken    
and1 finally1 the steering ropes to the 
rudders became entangled4 ,in spite of  
all this1 a speed of #ac feet per       

second1 or about #i miles per hour1 was 
obtained4 ,these breakages made it      
necessary to descend to the lake for    
repairs and in alighting the framework  
was further damaged by running into a   
pile in the lake4 ,the airship was      
repaired and another flight was made    
later in the year1 during which a speed 
of #cj feet per second1 or #bj miles per
 hour1 was obtained4  ,second ,airship4 
,zeppelin had sunk his own private      
fortune and that of his supporters in   
his first venture1 and it was not till  
five years later that he succeeded in   
raising enough money to construct a     
second airship4 ,no radical changes in  
construction were made in the new model1
 but there were slight improvements made
 in all its details4 ,the balloon was   
about #h feet shorter than the original 
and the propellers were enlarged4 ,three
 vertical rudders were placed in front  
and three behind the balloon1 and below 
the end of the craft horizontal rudders 
were installed to assist in steering    

upward or downward4 ,the steering was   
taken care of from the front car4  ,the 
most important change was made possible 
by the improvement in gasoline engines  
during the preceding five years4 ,where1
 in the earlier model1 he had two       
#af-;horsepower engines1 he now used an 
#he-;horsepower engine in each car1 with
 practically the same weight4 ,in fact1 
the total weight of the vessel was only 
#i tons1 while his first airship weighed
 #aj tons4  ,his new craft made many    
successful flights4 ,one was made at the
 rate of #ch miles per hour and         
continued for seven hours1 covering a   
total distance of #bff miles4  99,later 
,zeppelins499 ,the later ,zeppelins     
embody no remarkable changes in design1 
the principal alteration being in size4 
,one of these is illustrated in ,fig4   
#af4 ,in this the gas bag was increased 
to #ddf feet in length and it held over 
#dfj1jjj cubic feet of gas4 ,this gave  
it a total lifting power of #af tons4   
,with this1 ,zeppelin made a voyage of  

over #cge miles4 ,he was in the air for 
twenty hours on this trip and carried   
eleven passengers with him4             
,illustration3 ,fig4 #af4 ,zeppelin     
,airship in ,flight  ,in ,august1 #aijh1
 the ,zeppelin left its great iron house
 at ,friedrichshafen and sailed in a    
great circle over ,lake ,constance4 ,the
 day after it started1 however1 it was  
destroyed by a storm1 and sudden        
destruction from one cause or another   
has ended the existence of practically  
every one of the ,zeppelins built since1
 usually after a very brief period of   
service4  99,shape and ,framing499 ,in  
the early days of dirigible design the  
data upon which the shape and           
proportions of the envelope were based  
were purely empirical4 ,schwartz1       
,germany's pioneer in this field1       
adopted the projectile as representing  
the form offering the least air         
resistance and accordingly designed his 
envelope with a sharply pointed bow and 
a rounded-off stern1 giving it a length 

four times its diameter4 ,zeppelin did  
not agree with these conclusions and    
adopted a pencil form1 rounded at the   
nose and tapering to a sharp point at   
the stern1 making the length nine to ten
 times the diameter4 ,subsequent        
research work in the aerodynamic        
laboratory has demonstrated that the    
most efficient form for air penetration 
is one having a length six times its    
maximum diameter with the latter        
situated at a point four-tenths of the  
total length from the bow4 ,it has      
likewise been proved that an ellipse is 
more efficient than either the          
projectile or pencil form and that      
tapering to a sharp point at the stern  
offers no particular advantage4 ,as a   
result1 the most approved form resembles
 the shape of a perfecto cigar1 the nose
 being somewhat blunter than the after  
end4 ,this form is likewise that of the 
swiftest-swimming fishes and has been   
shown to have the least head resistance 
as well as the minimum skin friction2 it

 results in a section to which the term 
stream-line has been applied1 and it is 
now employed on all exposed             
non-supporting surfaces on aeroplanes1  
such as the struts and even the bracing 
cables4 ,laboratory research has        
demonstrated that it is worth while to  
reduce the head resistance of even such 
apparently negligible surfaces as those 
presented by these wires and cables and1
 therefore1 they are stream-lined by    
attaching recessed triangular strips of 
wood to their forward sides4  ,framing  
,details4 ,despite this1 the builders of
 the ,zeppelins have adhered to the     
original pencil shape with but slight   
modifications at the bow and stern1     
probably because that shape is much     
easier to build and assemble from       
standard girders4 ,the form of girder   
employed is shown in ,fig4 #ag1 while   
the complete assembly of the frame is   
illustrated in ,fig4 #ah4 ,the girders  
form the longerons1 or longitudinal     
beams1 running the entire length of the 

rigid frame and supported at equidistant
 points by ring members built of similar
 girder sections4 ,the fourth ring from 
the nose and each alternate ring after  
that are further braced by being trussed
 to the longitudinal beams around their 
entire circumferences1 as shown in ,fig4
 #ah4 ,the larger ,v-shaped truss at the
 bottom forms the gangway1 which is now 
placed inside the envelope instead of   
being suspended beneath it1 as formerly4
 ,this is done to eliminate the head    
resistance set up by the additional     
surface thus exposed4 ,in the first     
instance in which this gangway was      
incorporated in the envelope1 no        
provision was made for ventilation1 and 
the ship was wrecked by a gas explosion4
 ,regardless of how tight the fabric is 
made1 gas is always oozing out through  
it to a greater or less extent4 ,this   
fact is now met by providing ventilating
 shafts leading from the gangway to the 
upper surface of the envelope4          
,additional shafts through the envelope 

lead to gun platforms1 forward1         
amidships1 and aft1 and are reached by  
aluminum ladders4  ,illustration3 ,fig4 
#ag4 ,trellis ,type of ,aluminum ,girder
 used in ,longitudinals of ,zeppelin    
,frame  ,illustration3 ,fig4 #ah4       
,aluminum ,frame ,construction of       
,zeppelin ,hull  ,framing of            
,schutte-,lanz ,type4 ,it has become    
customary to refer to all large ,german 
airships as ,zeppelins1 but many of     
those used during the past three years  
have been of the ,schutte-,lanz build1  
which is also a rigid frame type of     
dirigible but has been designed with a  
view of overcoming some of the          
disadvantages of the aluminum frame     
construction encountered in the use of  
the ,zeppelin4 ,the length and diameter 
of the latter airships are such that1 no
 matter how rigidly the framing is      
assembled1 there is more or less sag4   
,when the sag exceeds a certain amount1 
the frame is apt to buckle at the point 
where it occurs1 involving expensive    

repairs or wrecking the airship         
altogether4 ,to overcome this           
difficulty1 the ,schutte-,lanz type     
employs a rigid frame of flexible       
material1 namely1 laminated wood in     
strip form1 held together at joints and 
crossings by aluminum fittings and      
braced inside by cables4 ,as shown by   
,fig4 #ai1 no rigid longitudinal beams  
are employed1 the only girders used     
being rings1 to which a network built of
 the wood strips is attached4 ,starting 
at the nose1 each continuous strip      
follows an open spiral path such as     
would be traced in the air by a screw of
 very large pitch1 in fact1             
approximating the rifling of a gun      
barrel4 ,it will also be noted from the 
illustration that the form of the       
,schutte-,lanz airship is the           
cigar-shape1 which laboratory research  
has shown to be the most efficient4     
,illustration3 ,fig4 #ai4 ,schutte-,lanz
 ,type of ,frame ,construction of       
,laminated ,wood with ,aluminum         

,fittings  ,the use of wood in          
conjunction with the spiral construction
 of the supporting members of the       
framing affords the maximum degree of   
flexibility1 since the displacement of  
any of these members under stresses of  
either tension or compression would have
 to be very great to cause damage to the
 frame as a whole4 ,the frame not being 
rigid1 strictly speaking1 either as     
units or as a complete assembly1 stress 
at any particular point would simply    
cause all the members near that point to
 give in the direction of the strain1   
and the rest of the frame would         
accommodate itself to their change of   
position by either elongating or        
shortening slightly4 ,in addition to    
these advantages1 the ,schutte-,lanz    
type of construction is said to be      
lighter than the ,zeppelin for an       
airship of the same load-carrying       
capacity4  99,power ,plant499 ,compared 
with their successors of war times1 the 
early ,zeppelins were mere pigmies where

 power is concerned4 ,many of these     
pioneers were driven by less than #ajj  
horsepower all told1 whereas in the     
later types no single motor unit as     
small as this total has been employed4  
,the motors used most largely have been 
the #afj-;horsepower ,mercedes and the  
#bjj-;horsepower ,maybach1 both of which
 are described in detail under the title
 ,aviation ,motors4 ,from five to ten of
 these units have been used on a single 
ship1 giving an aggregate in some of the
 latest types of close to #b1jjj        
horsepower4 ,power has been applied     
through five or six propellers to limit 
their diameter and to guard against the 
breakdown of any one of the units       
putting the power plant out of          
commission as a whole4 ,to distribute   
the weight of the engines equally and to
 insure each propeller a position in    
which it can work in undisturbed air1   
the engines have been placed at widely  
separated points on the airship and in  
different planes so that no two are     

coaxial4 ,the main engine room is       
usually located in a cabin just back of 
the operating bridge and wireless room1 
while the remaining motors are suspended
 in independent gondolas at different   
points along the sides4 ,where more than
 #a1jjj horsepower has been used1 each  
of these gondolas' has been fitted with 
two motors placed side by side and so   
coupled that either one or both may be  
employed to drive the single propeller  
carried by the propelling car4 ,all the 
more recent propellers have been of the 
two-bladed type4  99,control            
,surfaces499 ,the numerous expedients   
formerly resorted to by various         
designers in providing for stabilizing1 
steering1 and elevating surfaces have   
been abandoned for forms that are       
practically a duplication of aeroplane  
practice4 ,experience demonstrated that 
the different types of multiplane       
rudders1 elevators1 and stabilizing     
surfaces employed in earlier days not   
only offered no operating advantages but

 were actually detrimental1 in that they
 increased the head resistance          
unnecessarily4 ,moreover1 their         
complication meant increased weight and 
weaker construction4 ,they have         
accordingly been displaced by monoplane 
surfaces which are of exactly the same  
type of construction as those used on   
the aeroplane and the location and      
proportions of which are very evidently 
based on aeroplane practice4 ,both the  
horizontal and vertical stabilizers are 
of approximately triangular form and    
have the steering and elevating surfaces
 hinged to them at their after ends1 so 
that1 except for the pointed extremity  
of the envelope which extends beyond    
them1 the tail unit of the later        
,zeppelins is practically the same as   
the empennage of an aeroplane4 ,the     
horizontal surfaces are apparently      
depended on entirely to effect the      
ascent and descent1 there being no      
evidence of swiveling propellers by     
means of which the power of the engines 

could be employed to draw the airship up
 or down4 ,the great weight of ballast  
carried is1 of course1 in the form of   
water1 but this is discarded in order to
 ascend only when the power of the      
engines exerted against the elevating   
planes is no longer capable of keeping  
the airship at the altitude desired4 ,in
 the low temperatures encountered in    
night flights1 however1 the contraction 
of the hydrogen gas is so great that the
 crew has found it necessary to reduce  
the weight by discarding not only every 
pound of ballast but1 as far as         
possible1 everything portable4 ,despite 
this1 several airships have fallen when 
their fuel supply was exhausted1 one    
coming to the ground in ,scotland1 two  
dropping into the ,north ,sea1 and three
 or four falling in ,france4            
99,operating ,controls499 ,all the      
operating controls are centered at the  
navigating bridge1 which is inclosed to 
form the commander's cabin4 ,by means of
 push buttons1 switches1 levers1 and    

wheels every operating function required
 is set into motion from this central   
point4 ,whether auxiliary motors are    
carried for the purpose of pumping air  
into the balloonets or this is one of   
the duties of the main engine just back 
of the wireless room does not appear1   
but with the aid of a push button board 
the amount of air in any of the         
balloonets may be increased or decreased
 at will4 ,there is a control button for
 each operation1 or two for each        
balloonet1 which fact necessitates a    
rather forbidding looking board1 since  
the more recent ,zeppelins have         
seventeen to nineteen gas bags within   
each of which is incorporated an air    
balloonet4  ,the amount of fuel supplied
 to any one of the motor units can      
likewise be controlled from a central   
board1 and this is also true of the     
ballast release apparatus1 so that water
 can be emptied from any one of the     
ballast tanks at will1 thus facilitating
 ascent or descent by lightening one end

 or the other4 ,elevating and steering  
surfaces are operated by small          
hand-steering wheels with cables passing
 around their drums1 a member of the    
crew being stationed at each of these   
controlling wheels4 ,owing to the number
 of motors used1 the instrument board is
 the most formidable appearing piece of 
apparatus on the bridge1 since there is 
a revolution counter for each power unit
 in addition to the numerous other      
instruments required4 ,some of these    
instruments are the aneroid barometer   
for indicating the altitude1 transverse 
and longitudinal clinometers to show the
 amount of heel and the angle at which  
the airship is traveling with relation  
to the horizontal1 the anemometer1 or   
air-speed indicator1 manometers1 or     
pressure gauges1 for each one of the gas
 bags1 fuel and ballast supply gauges1  
drift indicators1 electric bomb         
releasers1 mileage recorders1 and the   
like4 ,in addition to these1 there are a
 large chart and a compass1 so the      

navigating bridge of a ,zeppelin        
combines in small space all the         
instruments to be found in the engine   
room and on the bridge of an ocean liner
 besides several which the latter does  
not require4 ,that the proper           
coordination of all the functions       
mentioned is an exceedingly difficult   
task for one man seems evident from the 
numerous ,zeppelins that have apparently
 wrecked themselves4  99,crew           
,carried499 ,in the various ,zeppelins  
that have been captured or shot down by 
the ,british or ,french1 the personnel  
has varied from fifteen to thirty men   
but in the majority of instances has not
 exceeded twenty4 ,the positions and    
duties are about as follows3 ,the       
commander1 lieutenant-commander1 and    
chief engineer1 and possibly a          
navigating officer are stationed at the 
bridge4 ,two or three of the crew are   
also stationed there to work the        
manually operated controls4 ,in the     
cabin just back of the bridge are two   

wireless operators and one or two engine
 attendants for the motors in the engine
 room behind the wireless room4 ,a      
similar number of engine attendants are 
stationed in the after engine room and  
there is at least one attendant for each
 of the other motor units4 ,one man is  
stationed at each machine gun1 of which 
there are three to five on the roof and 
two in each car1 and at least as many   
bombers are needed to load the droppers4
 ,as a reserve there are usually an     
additional gun pointer for each gun and 
an extra engine attendant1 since to run 
continuously most of the crew would have
 to stand watch and watch as in marine  
practice4 ,the sleeping accommodations  
consist of canvas hammocks slung in the 
gangway4  99,explosives ,carried499 ,in 
addition to a liberal supply of         
ammunition for the machine guns1 a large
 weight of bombs is carried1 though the 
quantity as well as the size of the     
bombs themselves has been exaggerated in
 the same or even greater ratio than    

that which has proved characteristic of 
the ,german military press-agency       
service4 ,the bombs are carried         
suspended in racks amidships1 and the   
bomb droppers are also located at that  
part of the ship so that the release of 
the bombs will not upset the            
longitudinal equilibrium of the craft4  
,the bomb-dropping apparatus is         
controlled electrically from the        
navigating bridge but may also be       
operated by hand from the same point4   
,it has been reported by the ,germans   
that their latest types of ,zeppelins   
are capable of dropping bombs weighing  
#a ton each4 ,in view of the effect that
 the sudden release of a weight of #a   
ton would have on the airship itself1   
this is manifestly very much of an      
exaggeration4 ,zeppelin bombs that have 
failed to explode have never exceeded   
#bjj to #cjj pounds and many of those   
employed are doubtless still lighter4   
,so far as the total amount carried is  
concerned1 many of the later airships   

doubtless are capable of transporting #b
 to #c tons and still carrying          
sufficient fuel1 though adverse         
conditions would prevent their return1  
as has frequently happened4    ,,british
 ,,war ,,dirigibles   99,adoption of    
,small ,type499 ,german designers have  
continued to pin their faith blindly to 
the huge rigid type1 despite the fact   
that prior to the war almost a dozen of 
these costly machines met with disaster 
as fast as they could be turned out4    
,since the war started1 their           
destruction has kept pace pretty closely
 with their building without their      
accomplishing anything of military      
value4 ,the ,british naval aeronautic   
service1 on the other hand1 appreciated 
the futility of such tremendous and     
unwieldy construction and1 after a      
single demonstration of its uselessness1
 abandoned it altogether4 ,this single  
attempt was the ill-fated ,mayfly1 which
 was most appropriately named1 since its
 performance resolved into a certainty  

the doubt expressed by its title4 ,in   
being taken out of its shed1 the framing
 of the airship was damaged1 and it     
collapsed a few minutes later so that it
 never did fly4 ,one of the early types 
of small ,british dirigibles is shown in
 ,fig4 #bj4  ,attention has since been  
concentrated in most part on the        
construction of aeroplanes in constantly
 increasing numbers1 although the       
dirigible has not been given up         
altogether4 ,however1 its restricted    
usefulness as well as the necessary     
limitations of its effective size has   
been recognized4 ,early in the war      
,great ,britain planned the construction
 of fifty small dirigibles1 of both the 
rigid and nonrigid types1 all of which  
have undoubtedly since been completed4  
,they are small airships designed       
chiefly for scouting and short-range    
bombing raids over camps when in army   
service and for coast patrol and        
submarine hunting as an aid to the naval
 forces4 ,while no specifications are   

available1 the cubic capacity of these  
patrol airships probably does not exceed
 #ej1jjj to #ge1jjj cubic feet1 their   
over-all length being approximately #ajj
 to #abe feet4  ,illustration3 ,fig4    
#bj4 ,an ,early ,type of ,small ,british
 ,dirigible  99,aeroplane ,features499  
,to simplify the construction and at the
 same time minimize the amount of head  
resistance1 the car consists of an      
aeroplane fuselage of the tractor type1 
fitted with a comparatively small       
motor--under #ajj horsepower--and having
 accommodations for a pilot and an      
observer in two cockpits1 placed tandem4
 ,the control surfaces are also similar 
to those used in aeroplane construction4
 ,despite their low power1 these        
dirigibles can make #dj miles an hour1  
owing to their greatly reduced head     
resistance4 ,instead of employing either
 an auxiliary blowing motor or a blower 
driven by the motor itself1 the supply  
duct to the air balloonet is made rigid 
and is sloped forward so that its open  

end comes directly in the slip stream of
 the propeller2 thus the latter serves  
to inflate the balloonet as well as to  
drive the dirigible4 ,the desired amount
 of inflation is controlled by a valve4 
,illustration3 ,fig4 #ba4 ,side and ,end
 ,views of ,british ,astra-,torres      
,dirigible ,used for ,anti-,submarine   
,patrol ,service  99,use in ,locating   
,submarines499 ,many of these small     
scouting and naval-patrol dirigibles    
have given a good account of themselves 
and comparatively few have met with     
accident or have been destroyed by the  
enemy4 ,on frequent occasions they have 
been very successful in locating        
submarines below the surface1 since the 
body of the under-water boat is readily 
detected from an altitude of a thousand 
feet or more1 even though submerged to a
 great depth and despite a heavy ripple 
on the surface that makes the water     
absolutely opaque when viewed from the  
deck of a ship4 ,doubtless they will be 
employed to an increasing extent as the 

hunt for the submarine becomes more and 
more intensive1 though their use is very
 much restricted during the winter      
months1 owing to the frequent and severe
 storms encountered4  99,british        
,astra-,torres499 ,a number of          
comparatively small ,astra-,torres      
dirigibles have also been built in      
,great ,britain for coast patrol and    
anti-submarine work4 ,the line drawing  
at the left of ,fig4 #ba illustrates the
 general design and construction of     
these small airships1 while the various 
letters indicate the different parts of 
the gas container1 air balloonets1      
suspension and car1 and the end view at 
the right of the figure shows the small 
amount of head resistance offered by the
 suspension of this type as compared    
with that of the usual form of nonrigid 
dirigible4 ,a is the balloon itself1 or 
main gas container1 the pressure relief 
valve for which is located at ,m4 ,,bb  
are the air balloonets connected with   
the blower ,h in the car4 ,in the       

illustration these balloonets are shown 
fully inflated as they would be after   
the gas bag had lost a considerable     
proportion of its original contents     
through leakage or expansion4 ,at the   
beginning of a flight1 when the gas bag 
is fully inflated with hydrogen1 they   
lie perfectly flat along the lower side 
of the envelope1 being brought into     
service only as they are needed to keep 
the envelope distended to its full      
volume4  ,the novel method of suspension
 to which this type of dirigible owes   
its greater speed and fuel economy1     
because of the reduction of the head    
resistance1 is shown by the numerous    
supporting ropes ,o-,o-,o1 which        
terminate in a comparatively few cables 
attached to the car4 ,in the small      
,british airships referred to here1     
there is but one small car designed to  
carry a crew of two men and the engine  
is of comparatively low power1 driving a
 propeller at either end of the car1 but
 in the large ,french dirigibles of the 

same type1 two large cars are placed    
tandem some distance apart and are      
fitted with #ejj-;horsepower motors4    
,the various parts indicated by the     
letters are3 ,,cc propellers1 ,d motor1 
,f space for pilot and crew1 ,g fuel and
 oil tanks1 ,j guide rope1 ,k gas valve1
 ,,ll air valves1 ,,nn balloonet cable1 
,p rudder1 ,q stabilizer1 ,,rr bracing  
cables1 and ,s the car itself4          
,,military ,,uses ,,of ,,zeppelins      
99,limitations of ,use499 ,nothing      
excites the ,teutonic imagination so    
strongly as things military to which the
 characteristic ,german adjective       
kolossal can be enthusiastically        
applied4 ,it was for this reason that1  
despite its uniform record of tragic    
disaster for years before the war1 the  
,germans pinned their faith to the      
,zeppelin as a weapon that could not    
fail to strike terror to the hearts of  
the ,british and ,french and make them  
hasten to sue for peace4 ,however1 apart
 from its reputed employment on the     

single occasion that the ,german grand  
fleet left the security of the ,kiel    
,canal1 it is not known to have been    
used in any purely military operation4  
,the aeroplane has been developed to a  
point that1 in spite of the ability of  
the ,zeppelin to ascend rapidly when    
hard pressed1 would make it suicidal for
 one of the huge gas bags to sally forth
 in daylight1 unless attended by a large
 number of battle planes to prevent     
enemy flying machines from attacking it4
 ,no such use of the ,zeppelin has been 
recorded thus far4 ,consequently1 it has
 been used only in nocturnal            
bomb-dropping expeditions1 chiefly      
directed against ,london and only       
undertaken when weather conditions made 
detection difficult4 ,in order to carry 
these out1 it has been necessary to     
establish stations in ,belgium1 since   
the fuel consumption of the ,zeppelin is
 so great that1 even with its tremendous
 fuel supply of #c to #e tons1 a flight 
to ,london and return to points well    

within the ,german border is            
impracticable4 ,the first raids of this 
character were carried out successfully1
 but subsequent attempts were marked by 
the loss of one or two airships on each 
occasion1 so that the practice was      
abandoned as being too expensive for the
 results attained and aeroplanes were   
substituted4  99,number ,built499       
,taking it for granted that the         
numbering of the ,german airships has   
been consecutive1 the total number built
 during the first three and one-half    
years of the war by the ,germans would  
be between eighty and one hundred4 ,all 
large ,german airships have come to be  
commonly termed ,zeppelins1 but a number
 of them were of the ,schutte-,lanz     
type1 almost equally large and also     
characterized by rigid construction1    
which1 however1 was of wood with        
aluminum fittings instead of being all  
metal1 as it was found that the huge    
metal frame accumulated a static charge 
of high potential that was responsible  

for igniting the gas in one or two      
instances4  99,weakness of ,type499 ,the
 ,l-,i 7,luftschiff1 or airship71 the   
first of the ,german airships designed  
for purely military purposes1 was a     
,zeppelin #ebe feet long by #ej feet in 
diameter1 of #ggg1jjj cubic feet        
capacity1 and #bb tons displacement4    
,its three sets of motors developed #ejj
 horsepower and it had a speed of #eb   
miles per hour4 ,it was launched at     
,friedrichshafen in #aiab1 and after a  
number of successful cross-country      
trips1 it was tried in connection with  
naval maneuvers off ,heligoland4 ,before
 the trial had proceeded very far1 a    
sudden squall broke the backbone of the 
huge gas bag and hurled it into the sea1
 drowning fifteen out of the crew of    
twenty-two4 ,it is a striking commentary
 on the frailness of these aerial       
monsters that every one of the big      
airships built up to that time had met  
disaster in an equally sudden manner but
 from a totally different cause in each 

instance4 ,the ,l-,,ii was slightly     
shorter but had #e feet longer beam and 
displaced #bg tons4 ,she was designed   
particularly for naval use1 had four    
sets of motors developing #ijj          
horsepower1 and was fitted with a       
navigating bridge like that of a ship4  
,it was confidently thought that all    
possible shortcomings had been remedied 
and success finally achieved in the     
,l-,,ii1 but before there was any       
opportunity to demonstrate its          
efficiency1 the airship exploded in     
mid-air1 killing its entire crew4       
,effectiveness ,grossly ,overrated4     
,despite this unbroken chain of         
disasters1 the ,german official press   
bureau spread broadcast the prowess of  
the ,zeppelin1 its magnificent ability1 
and its remarkable achievements as an   
engine of war--in theory1 since this was
 a year or two prior to the outbreak of 
hostilities4 ,had it not been for the   
forced descent of the ,zeppelin ,,iv at 
,luneville1 where it was taken          

possession of by the ,french1 these     
tales might have been accepted at their 
face value4 ,but the log of the         
commander of this airship showed that   
its maximum speed was but #de miles per 
hour1 the load #aj1efj pounds1 and the  
ascensional effort #de1ajj pounds4 ,the 
fuel consumption averaged #big pounds   
per hour while the fuel capacity was    
only sufficient for a flight of seven   
hours4 ,during its flight1 it had       
reached an altitude of only #f1bej feet1
 to accomplish which over #c tons of    
ballast had to be dropped4 ,it was also 
shown that the critical flying height of
 these huge airships is between #c1ejj  
and #d1jjj feet1 ,zeppelin himself      
declaring that his machines were useless
 above #e1jjj feet4 ,this probably      
accounts for the fact that the early    
raids on ,english towns were carried out
 at a height but slightly in excess of  
#b1jjj feet4 ,later types1 however1 are 
said to have reached high altitudes4    
,illustration3 ,fig4 #bb4 ,zeppelin     

,l-#di ,brought ,down ,intact by a      
,french ,airman1 ,resting on ,hillside  
near ,bourbon-,les-,baines ,copyright by
 ,underwood and ,underwood1 ,new ,york  
,shortly before the outbreak of the war 
the ,l-#e was completed4 ,this had a    
capacity of about #a1jjj1jjj cubic feet1
 motors aggregating #a1jjj horsepower or
 over1 and a reputed speed of #fe miles 
per hour4 ,just what was the fate of    
this particular ship did not become     
known1 since information of a military  
character has not been permitted to leak
 out of ,germany from that time on4 ,but
 capture or destruction has accounted   
for many of the intermediate numbers of 
the series2 big ,german airships have   
been brought down in ,england1 in the   
,north ,sea1 in ,france1 and at         
,saloniki1 their loss culminating in the
 disaster to four out of the fleet of   
five that attempted a raid over ,london 
but were caught by adverse winds which  
exhausted their fuel supply so that they
 were blown out of control1 toward the  

south of ,france4 ,french anti-aircraft 
batteries or aeroplanes accounted for   
three of these1 while the fourth1 the   
,l-#di1 was captured intact4            
,illustration3 ,fig4 #bc4 ,nose of      
,giant ,l-#di and ,group of ,sightseers 
,copyright by ,underwood and ,underwood1
 ,new ,york  99,l-#di499 ,an essential  
part of the equipment of every form of  
,german military apparatus is a means of
 destroying it in case of capture4 ,in  
the case of the big airships1 the       
officers are provided with revolvers    
loaded with incendiary bullets1 which   
are fired into the gas bag1 so that     
until the ,l-#di was forced to descend  
in the south of ,france by the          
activities of a battle plane1 plus a    
lack of fuel1 no airship of a recent    
type had ever been captured intact4 ,in 
this case1 the commander fired his      
pistol at the balloon but missed and was
 prevented from firing again by a       
,french peasant who covered him with a  
shotgun4 ,the wireless operator         

succeeded in using a sledge hammer on   
some of the apparatus of the very       
completely equipped wireless cabin      
before he was captured but did not do   
sufficient damage to prevent reassembly 
of the parts with little trouble4 ,with 
the exception of the earlier type of    
,zeppelin that was forced to descend at 
,luneville prior to the war1 the ,l-#di 
was the first that was ever known to    
have landed undamaged in hostile        
territory1 as practically all the others
 were destroyed in the air1 most of them
 having been wrecked either by aeroplane
 or anti-aircraft fire4 ,fig4 #bb shows 
the ,l-#di as it rested on a hillside at
 ,bourbon-les-,baines1 ,france1 and     
,fig4 #bc shows a close view of the nose
 of the monster4  ,standardized ,parts4 
,comparing the ,l-#di with many of its  
predecessors led to the conclusion that 
it was one of the latest types1 but an  
inspection of its construction revealed 
the use of many parts produced in       
quantities from standard patterns as    

well as a lack of the finish that has   
always characterized airship            
construction4 ,appearance and comfort   
had both been sacrificed with a view to 
saving the last ounce of superfluous    
weight in order to carry more fuel and  
ammunition4 ,evidently the production of
 these large airships has been reduced  
to a manufacturing basis and they are   
constructed in series in much the same  
manner as motor cars1 though on a       
reduced scale4  ,general ,design4 ,in   
its general construction the ,l-#di was 
along the same lines that have          
characterized the ,zeppelin since its   
inception1 the outer envelope being     
stretched over a rigid frame of aluminum
 girders1 inclosing a large number of   
independent balloons inflated with the  
usual hydrogen gas1 no trace being      
discovered of the non-inflammable gas1  
the discovery of which had been hailed  
by the ,german press4 ,the commander's  
cabin was suspended well forward with   
the wireless room directly behind it1   

while a ,v-shaped gangway1 recessed in  
the envelope proper so as to present no 
additional head resistance1 ran back    
from the latter the whole length of the 
ship4 ,this and the gun platform on top1
 mounting two machine guns and reached  
by a ladder suspended in a well         
amidships1 have been familiar features  
of all the recent ,zeppelins4 ,the main 
envelope contained nineteen independent 
gas bags1 each of which was made        
integral with an air balloonet to take  
care of the expansion and contraction of
 the hydrogen with varying altitudes and
 temperatures4 ,distributed along the   
lower part of the frame inside the      
envelope were a series of #ej-;gallon   
water-ballast tanks4  ,power ,plant4 ,no
 less than nine large motors were       
employed to drive the huge gas bag1 the 
maximum horsepower probably aggregating 
#a1fjj to #b1jjj4 ,the motors were      
distributed in five different locations1
 the largest being suspended just abaft 
the wireless room4 ,the remainder were  

placed in self-contained units in the   
form of gondolas suspended from the     
sides of the frame1 as shown in ,fig4   
#bd1 the outline being that of a        
blunt-nosed fish4 ,each of these        
gondolas carried two motors placed side 
by side and coupled up so that either   
one or both could be employed to drive  
the single propeller4 ,for cruising     
speeds one motor in each gondola        
supplied sufficient power or in some    
gondolas both motors could remain idle4 
,no accommodation was provided for      
attendants in the gondolas1 any of which
 could easily be reached by light       
ladders from the inclosed gangway4  ,to 
insure greater safety1 the fuel supply  
was divided among sixteen tanks1 all of 
which were interconnected with each     
other and the engines so that gasoline  
from any tank or tanks could be diverted
 to any particular engine4 ,the supply  
of lubricating oil for each engine was  
carried in a tank in the gondola itself4
  ,control4 ,vertical and horizontal    

stabilizing surfaces of conventional    
form were built on the sharply tapering 
rear end of the frame1 the elevator and 
rudder being similar to those used in   
aeroplane construction1 except that the 
rudder was in two sections1 the larger  
of which was placed on top of the       
envelope4 ,the control of these         
surfaces1 the operation of all the      
engines1 the control of the water       
ballast1 the air supply to the          
balloonets1 and the fuel supply to the  
motors were all concentrated at a panel 
board in the commander's cabin1 the     
forward end of which bore a close       
resemblance to the bridge of a          
man-of-war4 ,by means of thirty-eight   
push buttons1 half red and half white1  
air could be released from or pumped    
into the balloonets1 while in a similar 
manner the contents of any one of the   
water-ballast tanks could be emptied4   
,elaborate controls were provided for   
the power plant1 it being possible to   
vary the speed or stop any one or more  

of the motors from the bridge4 ,the     
rudder and elevators were operated by   
means of small hand wheels1 similar to a
 marine steering wheel4 ,one of the most
 prominent features of the operating    
cabin was a huge chart frame1 capable of
 carrying a large scale map covering a  
considerable area1 as well as an ample  
supply of maps4 ,few instruments were   
found in the captured ship and it is    
thought highly probable that everything 
not fastened in place had been dumped   
overboard at the last to increase its   
lifting power4  ,illustration3 ,fig4    
#bd4 ,one of ,six ,gondolas1 or ,power  
,units of the ,zeppelin ,l-#di          
,copyright by ,underwood and ,underwood1
 ,new ,york  ,apart from the use of     
standardized fittings and parts and the 
employment of a great deal more power in
 a slightly different manner than had   
characterized the earlier types of      
,zeppelins1 the ,l-#di revealed nothing 
of unusual importance in airship design 
and certainly none of the world-beating 

features that ,german propaganda had    
been heralding for some time previous4  
99,destruction of ,zeppelins499 ,mention
 has already been made of the fact that 
practically the only use made by        
,germany of her huge airships has been  
the bombardment of open cities1 and that
 always at night4 ,from the first of    
,september1 #aiad1 up to the end of     
#aiag1 between thirty and forty had met 
disaster1 but only two were captured    
intact4 ,the first of these was         
discovered by a ,russian cavalry patrol 
while at anchor and its crew of thirty  
men were made prisoners4 ,this was at an
 early period in the war1 while the     
second one to be captured was the       
,l-#di1 already referred to1 which      
formed one of a squadron of five        
evidently sent out on a bombing         
expedition against ,london4 ,owing to   
adverse winds1 they never reached their 
destination and four of them were known 
to have been put out of action1 all     
except the ,l-#di being destroyed in the

 air4 ,not a few of these big airships  
have fallen victims to their own        
weakness and succumbed to the elements1 
in one instance a high wind tearing the 
airship loose from its moorings while   
the crew was not aboard4 ,this was at   
,kiel1 and after traveling a number of  
miles unguided1 the big bag fell into   
the ,north ,sea4 ,in quite a number of  
other cases head winds have prevented   
the return of the raiders to their base 
and they have either been destroyed by  
their crews or wrecked at sea in        
attempting to return4 ,in still other   
instances the unwieldy monsters have    
been wrecked by high winds when         
attempting to land1 as was so frequently
 the case prior to the war4  ,aeroplane 
and ,anti-,aircraft ,fire ,effective4   
,before the war broke out the ability of
 either the aeroplane or the            
anti-aircraft gun to overcome the       
,zeppelin was purely theoretical1 but   
actual experience has demonstrated that 
much of the theory was well founded4 ,at

 least three ,zeppelins have been       
destroyed by ,british aviators in       
mid-air1 all or most of the crews being 
killed1 while probably an equal number  
have been accounted for by ,french      
aviators in open battle4 ,the war had   
not been under way a month before       
,french anti-aircraft gunners showed    
their skill by bringing down-a ,zep1    
while only a week later a ,russian      
battery accomplished the same feat1 in  
this instance killing the entire crew4  
,in #aiaf1 ,british and ,french gunners 
succeeded in either winging or setting  
on fire three or four1 while two dropped
 into the ,north ,sea and one was blown 
up by its crew1 having run out of fuel  
while raiding ,scotch towns4  ,bombing  
,raids against ,zeppelin ,sheds4 ,not   
the least of the disadvantages from     
which such huge and unwieldy craft      
suffer is the fact that the             
correspondingly large structures        
required to house them make exceedingly 
easy marks for the raiding aviator4     

,bombing1 however1 is such an uncertain 
art that even such large buildings as   
these cannot be struck from any altitude
 with a fair degree of accuracy4        
,consequently1 in the number of raids   
that have been carried out against      
,zeppelin sheds1 success has been due   
very largely to the temerity of the     
aviators1 who have descended within a   
few hundred feet of their mark despite  
the fire directed at them from all      
quarters4 ,at least three and probably  
more of the big airships have been      
destroyed in this manner by ,british    
aviators1 who have made flights of      
several hundred miles to reach their    
destination1 while the destruction of as
 many more has been ascribed by the     
,germans to the accidental explosion of 
a bomb in the shed4 ,in view of the     
great precautions taken against accident
 from the explosion of the bombs carried
 by the airship itself1 it is not       
considered at all likely that there was 
anything accidental about the wrecking  

of these craft4  ,one of the earliest   
attempts against ,zeppelin headquarters 
at ,friedrichshafen on ,lake ,constance1
 which resulted in the destruction of   
the ,l-#ca1 is typical of the plan      
followed in attacks of this kind4 ,two  
,british aviators flew from their base  
in ,france1 about #bej miles distant1 at
 a high altitude4 ,they became separated
 before reaching their destination owing
 to a mist4 ,this1 however1 prevented   
their discovery until they had dropped  
within a few hundred feet of the surface
 of the lake1 which it was necessary to 
do to obtain a view of the airship      
sheds4 ,the first pilot dropped his     
cargo of bombs from a height of only    
#ajj feet or so over the shed and was   
rewarded by seeing it catch fire4 ,he   
had hardly straightened out on his      
return course before he heard the attack
 of his companion4 ,the latter was not  
so fortunate in escaping unscathed1 as a
 bullet pierced his fuel tank and       
compelled him to descend4 ,in the       

majority of instances1 however1 the     
raiders have succeeded not only in      
carrying out their task but in escaping 
undamaged as well4    ,,captive         
,,balloons   99,military ,value499 ,as  
an aid to military operations1 the use  
of the captive balloon dates back many  
years4 ,it was extensively employed in  
the ,civil war and more recently in the 
,boer war1 but with the advent of both  
the dirigible and the aeroplane1 it was 
generally considered outside of ,germany
 that its reason for existence had      
passed away4 ,the ,german military plans
 included a large number of balloons for
 artillery observation purposes and they
 were used right from the start4 ,it was
 only when the fighting settled down to 
trench warfare1 however1 that they came 
into prominence and the aid that they   
rendered the ,german batteries put their
 opponents at a serious disadvantage4   
,like the bayonet1 which was also       
generally considered to have been       
relegated to military operations of the 

past1 the captive balloon is now playing
 a very important role1 particularly on 
the western front4 ,in favorable        
weather1 anywhere from ten to forty of  
these aerial observation posts will be  
visible from a single point on the line4
  99,spherical ,type ,defective499 ,the 
captive balloon of the present day1     
however1 bears no resemblance to its    
predecessors4 ,from a sphere1 it has    
been developed into a form that more    
nearly resembles the dirigible and at   
the same time1 it embodies some of the  
features of the aeroplane4 ,the old     
spherical balloon was always at the     
mercy of the wind1 which not only       
governed the altitude to which the      
balloon would rise but also made things 
extremely uncomfortable as well as      
dangerous for the observers4 ,with      
#a1jjj feet of cable out1 such a balloon
 rises to an equivalent height on a     
perfectly1 calm day4 ,but even a light  
wind cuts this height down by #ajj or   
#bjj feet1 while if a strong wind is    

blowing1 the balloon is held down to    
within a few hundred feet of the ground 
regardless of the length of cable paid  
out4 ,every strong gust beats it over at
 a perilous angle and the resulting     
shocks to the basket are so severe that 
its occupants can have little thought   
for anything but their own safety4      
,strong cross gusts set both the bag and
 basket to spinning and jumping in a    
manner that would make the results of   
the severest storm at sea seem mild by  
comparison1 since the movements of the  
basket are executed with such rapidity  
that they seem to be in almost every    
plane simultaneously4 ,as a result1 the 
old type of captive balloon was         
available for service only in the       
calmest weather4  99,modern ,kite       
,balloon499 ,it should not be supposed  
that the improved type of observation   
balloon now in use in such large numbers
 provides any unusual amount of ease or 
comfort1 since it is also prey to the   
wind and does a great deal of swinging  

about as well as jerking when the wind  
is more than #ae or #bj miles an hour4  
,but it has been improved to a point    
where the wind not only serves to       
elevate1 instead of depressing it1 but  
also to steady it4 ,the new type4 ,fig4 
#be1 is technically known as a kite     
balloon1 because1 in addition to the    
appendages attached to the bag itself   
for steadying purposes1 it is equipped  
with a tail to assist in keeping it     
heading into the wind4 ,this consists of
 a number of bucket-shaped pieces of    
heavy canvas attached to the tail cable 
by bridles so as to catch the wind and  
hold it1 thus placing a heavy strain on 
the cable and preventing the balloon    
from swinging violently4 ,as is the case
 with practically everything used at the
 front1 the technical name of the new   
type of balloon is prominent by its     
absence4 ,it is a ,drache 7kite7 to the 
,germans and a blimp to ,tommy ,atkins4 
,both its shape and attitude when aloft 
bear a close resemblance to a huge      

sausage1 so that the term sausage is    
used by all the belligerents in common  
to a large extent4 ,a side view of an   
,american type is shown in ,fig4 #bf4   
,illustration3 ,fig4 #be4 ,head-,on     
,view of ,modern ,kite ,balloon1        
,showing ,details of ,tail ,buckets     
,copyright by ,central ,news ,service1  
,new ,york ,city  ,it will be noted from
 ,figs4 #be and #bf that the suspension 
of the basket and the appendages        
attached to the balloon at the rear hold
 it in a position which is roughly the  
equivalent on a large scale of the curve
 of an aeroplane wing4 ,it has both     
camber and an angle of incidence1 so    
that the wind serves to elevate it      
instead of beating it down4 ,this       
lifting effect is further increased by  
tubes of large diameter1 open at the    
forward end only and curving around the 
end of the gas bag at the rear4 7,it is 
also equipped with an air balloonet1 the
 same as a dirigible47 ,the wind enters 
the lower end of this tubular member1   

which is in a line with the longitudinal
 axis of the balloon1 but it must pass  
around the curve at the end of the gas  
bag before it can fully inflate it1 so  
that it performs the double function of 
increasing the lift and steadying the   
balloon1 though the latter is its chief 
purpose4 ,the basket is suspended quite 
a distance below the gas bag and has    
accommodation for two observers4 ,like  
scores of other inventions that the     
,germans were the first to utilize on a 
large scale in the present war1 the kite
 balloon was not a ,german creation but 
was originally developed in ,france4    
,illustration3 ,fig4 #bf4 ,american     
,kite ,balloon of ,latest ,type         
,ascending ,copyright by ,committee on  
,public ,information1 ,washington1 ,d   
,c4  99,methods of ,inflation499 ,the   
average capacity of the kite balloons   
used for observation purposes is #bh1jjj
 cubic feet4 ,they are inflated with    
hydrogen either from a portable         
generating plant forming part of the    

equipment of the balloon company or from
 a supply carried under high pressure in
 heavy steel bottles similar to those   
used for transporting oxygen or carbonic
 acid gas intended for industrial use4  
,since the balloon companies are        
stationed about #d miles back of the    
firing line1 the use of the portable    
plant is practical1 but it has been     
found more economical and more          
convenient to generate the gas on a     
large scale at special establishments in
 ,france and ,england and send it to the
 front in containers4 ,with a portable  
plant1 several hours are necessary to   
inflate the gas bag1 whereas with a     
large supply of the gas at hand under   
high pressure1 the operation may be     
carried out in less than an hour4  ,the 
balloon naturally works under the same  
difficulties as all lighter-than-air    
craft1 that is1 there is a constant     
leakage of the hydrogen through the     
fabric in addition to that lost by the  
expansion of the gas on warm days when  

the summer sun beats down directly on   
the gas bag4 ,where a field generating  
plant is employed1 quick inflation of a 
new balloon or replacement of loss is   
accomplished by the used of several     
nurses1 ,fig4 #bg4 ,these are simply    
large gas bags which are kept           
replenished by the gas plant working    
constantly1 in other words1 they are    
storage tanks1 and when it is necessary 
to inflate the balloon quickly1 their   
contents are simply transferred to it4  
,illustration3 ,fig4 #bg4 ,landing ,big 
,kite ,balloon at ,training ,station    
,somewhere in ,england4 ,nurse in       
,background ,copyright by ,underwood and
 ,underwood1 ,new ,york  99,balloon     
,company499 ,though aeronautical in     
character1 the kite balloon service is  
actually a branch of the artillery1 to  
which it is directly attached4 ,a       
balloon company accordingly consists of 
twelve to twenty artillery officers of  
varying ranks and about #abj to #acj    
men4 ,of the officers1 six to eight are 

artillery lieutenants or captains and go
 aloft as observers1 this number being  
necessary because the strain of watching
 constantly is very great and the       
observers must be relieved at frequent  
intervals1 the balloon otherwise being  
kept up continuously1 both day and      
night4 ,there are also a number of      
sergeants1 each of whom is in charge of 
a different branch of the work1 such as 
the inflation1 transport1 telephone     
service1 and winding machine4 ,no less  
than fifteen #c-ton to #e-ton motor     
trucks are necessary for each balloon   
company besides two or more motorcycle  
messengers1 the care of the machines    
usually being entrusted to the corporals
 of the company4 ,the remainder of the  
company are practically laborers1 whose 
chief duties are to attach the ballast  
bags to the ropes when it is intended to
 hold the balloon on the ground for any 
length of time and to utilize their own 
weight for the same purpose when the    
balloon is about to go aloft or is only 

on the ground temporarily4 ,in addition1
 every company has its surgeon and      
assistants1 quartermaster1 cooks1       
company clerk1 and other attaches       
necessary to complete its organization1 
since a balloon company serves as an    
independent unit4  99,equipment499 ,the 
paraphernalia required is quite as      
elaborate as that necessary to keep     
several aeroplanes aloft1 though        
naturally of a different nature4 ,it    
must all be readily portable1 for a     
balloon company has to change camp more 
or less frequently1 or as often as the  
enemy artillery happens to discover its 
range4 ,to secure mobility is the       
purpose of the great number of motor    
trucks employed4 ,one of these is       
equipped with a hoisting winch and a    
large drum capable of holding #c1jjj or 
#d1jjj feet of about #c_/h-;inch steel  
cable4 ,the winch is driven by the same 
engine that propels the truck1 and in   
case of emergency the engine may be     
applied to the two purposes alternately 

within a short space of time4 ,for      
instance1 in case of attack either by   
shrapnel from an enemy battery or by a  
hostile aviator1 it may be used to      
quickly haul in or let out cable to     
change the altitude of the balloon1 or  
it may be employed to drive the truck to
 another and more favorable location    
with the balloon in tow4  ,another truck
 houses a complete telephone exchange1  
since the observers in the balloon may  
wish to communicate with any one of a   
number of batteries which they are      
serving4 ,telephone communication is    
established by means of an insulated    
wire which forms the core of the cable1 
while the steel cable itself acts as the
 return wire to complete the circuit4   
,in some cases1 a separate copper cable 
is employed1 using the steel cable as   
the return half of the circuit4 ,in     
addition there is a truck for           
transporting the balloons1 for the      
company must always have duplicate      
equipment at hand in case of the        

destruction of the balloon it is using  
or1 as more frequently happens1 damage  
of a nature that requires hours or days 
to repair4 ,in addition to the balloon  
itself1 there are covers and the ground 
cloth1 as in inflating a balloon no part
 of its fabric must be allowed to touch 
the ground because of the danger of     
stones or sticks tearing rents in it4   
,the balloon proper and its immediate   
accessories utilize at least one and    
sometimes two motor trucks4  ,to hold   
the balloon on the ground when out of   
service1 there are eighty sacks of sand 
weighing #be pounds each1 or an         
aggregate of #a ton of ballast1 in      
addition to which there are necessary a 
large number of steel screw stakes1     
spare ropes and parts1 ladders and the  
like1 besides the basket and its        
equipment4 ,the stakes are employed to  
hold the balloon down in a heavy wind by
 pegging it in the same manner as a     
tent4 ,three or four trucks are required
 to carry the large supply of hydrogen  

necessary1 which entails the            
transportation of #acj to #aej          
containers4 ,each container holds       
several thousand cubic feet of gas under
 high pressure1 which is released       
through a reducing valve4 ,some of the  
other transportation units required are 
the cook wagon1 quartermaster's stores  
truck1 truck for carrying tents1        
blankets1 and other impediments for the 
men1 and the doctor's wagon 7ambulance74
  99,advantages of ,kite ,balloon499 ,it
 became a necessity to resurrect the    
captive balloon and bring it up to date1
 not simply because the ,germans were   
employing it in numbers1 but because    
experience demonstrated that it         
possessed numerous advantages over the  
aeroplane for artillery observation4    
,the observer in an aeroplane is carried
 back and forth over and around the     
location he wishes to watch1 at high    
speed and at a constantly varying       
altitude4 ,he must communicate by means 
of either signals or wireless1 and it is

 not always possible for him in either  
case to know whether his signals have   
been received and understood1 since it  
is possible to transmit messages by     
wireless from an aeroplane but a very   
difficult matter to receive4 ,the       
observers in a kite balloon1 on the     
other hand1 have the advantage of being 
able to scrutinize a certain sector     
constantly with the aid of powerful     
glasses4 ,with a few weeks of experience
 in observing a given terrain they      
become so familiar with it that any     
changes or the movements of troops or   
supplies are quickly distinguished4 ,the
 greatest advantage1 however1 is that   
the information thus acquired may be    
instantly transmitted not merely to one 
but to any one or all of a group of     
batteries extending over a mile or two  
of front in either direction1 the       
balloons being stationed #d to #f miles 
apart4 ,the observers are fitted with   
portable head sets so that they speak   
directly into their telephones without  

the necessity of removing the glasses   
from their eyes1 which enables them to  
watch the fall of the shells and tell   
the battery attendant in the dugout     
alongside the gun whether a shell fell  
short1 over1 left1 or right1 and the    
amount of correction needed before the  
smoke from the explosion has cleared    
away4 ,with the aid of close corrections
 of this nature the battery commander is
 in a position to get the range exactly 
without the great expenditure of        
ammunition that firing entirely by map  
or with the assistance of aeroplane     
observers entails4 ,instances are       
recorded in which a #i4e-;inch shell has
 been landed right in a concrete        
pill-box not over #ae feet square from a
 distance of #c miles after six trial   
shots had been fired to obtain the      
range4 ,such a shot is reported back to 
the battery by the balloon observer as a
 direct hit1 and it is only necessary to
 fire the gun at the same range and     
direction to score as often as          

necessary4  99,duties of ,balloon       
,crew499 ,each kite balloon carries     
aloft two observers1 ,fig4 #bh1 both of 
whom can concentrate their entire       
attention on the work of spotting1 since
 they have nothing to do with the       
control of the balloon itself1 except to
 give orders4 ,their chief duties       
consist of counter-battery observation1 
that is1 spotting the location of enemy 
batteries1 and being constantly alert to
 detect any suspicious movements back of
 the enemy's lines1 such as movements of
 troops1 ammunition1 or supplies4 ,the  
batteries controlled from observation   
balloons are the heavies1 which are     
located #a mile or more back of the     
front line trenches and to the gunners  
of which the objects they are firing at 
are never visible4 ,some of the heaviest
 guns mounted on specially constructed  
railway trucks are often fired from     
points #e miles or more back of the     
lines4 ,in fact1 when balked in their   
attempt to take ,calais1 the ,germans   

bombarded the town with the aid of      
long-range naval guns from a distance of
 over #ae miles and every shot dropped  
into either some part of the city or its
 outskirts4 ,buildings1 hills1 or       
specially constructed and concealed     
observation towers are frequently       
utilized in conjunction with captive    
balloons to serve as auxiliary          
observation posts1 so that the base line
 connecting the two may be used to      
triangulate distances and thus calculate
 them more accurately than is possible  
by direct observation from a single     
point4  ,illustration3 ,fig4 #bh4       
,french ,kite ,balloon ,observers about 
to ,ascend ,copyright by ,committee on  
,public ,information1 ,washington1      
,d4,c4  99,risks ,incurred499 ,enemy    
,fire4 ,while the observers in a kite   
balloon are not subjected to all the    
risks that the aviator must encounter   
when he goes aloft or1 at least1 not to 
the same extent1 their lot is far from  
being free from danger4 ,one of the     

duties of the reconnoitering aviator is 
to destroy observation balloons by means
 of incendiary bombs equipped with      
fishhooks which catch in the fabric or  
by the use of his machine gun4 ,enemy   
batteries may also succeed in getting   
the range of the balloon and fire at it 
with large caliber shrapnel1 which      
spreads its fragments over an area #ajj 
yards or more in diameter when it       
bursts4 ,so many of the ,german balloons
 were downed by ,french and ,british    
aviators in the early part of the       
war--and the ,germans retaliated in     
kind--that a battle plane is now always 
detailed to keep watch above the balloon
 to ward off attacks by aeroplanes4     
,escape of ,balloon4 ,in addition to the
 risk of being shot down1 there is the  
ever-present danger of the balloon being
 wrecked by a sudden squall or of its   
breaking away from its windlass through 
the parting of the cable and floating   
over the enemy lines4 ,balloons have    
been lost through both causes in a      

number of instances4 ,each of the two   
observers wears a heavy harness to which
 is attached a parachute suspended by a 
light cord from the rigging of the      
balloon1 so that in case of emergency   
they may save themselves by jumping     
without having to make any preparations 
for their sudden drop4  ,in case of the 
breakage of the cable1 which usually    
results from a strong wind coming up    
suddenly and putting a terrific strain  
on the steel line by jerking it1 the    
observers are guided in their actions by
 the direction in which the balloon     
moves4 ,when it is carrying them back   
over their own territory1 they navigate 
in the same manner as a free balloon1   
coming to the ground as soon as a       
favorable landing place can be reached4 
,instruction in free ballooning is      
accordingly an important part of the    
curriculum that the kite balloon        
observers must go through4 ,should the  
wind be in the opposite direction1      
however1 as only too often proves to be 

the case1 all instruments1 papers1 and  
maps are immediately thrown over the    
side and the observers promptly follow  
suit in their parachutes1 abandoning the
 balloon to its fate4 ,as the balloon   
travels with the speed of the wind1 once
 it is released1 and the parachute of   
the descending observer is carried in   
the same direction1 prompt action is    
vital to prevent coming to the ground in
 the enemy's territory4 ,in a #cj-mile  
wind1 for example1 only eight minutes   
would elapse from the moment that the   
balloon broke away until it traversed   
the #d miles intervening between its    
station and the enemy's lines4 ,on some 
occasions1 kite balloons which were not 
fit for further service have been loaded
 with explosives and released from a    
height that would cause them to land    
well within the enemy's territory with  
disastrous results to the men detailed  
to capture them4  99,marine ,service499 
,the kite balloon was first used by the 
,british naval forces in their          

operations against the ,dardanelles and 
proved so valuable that they have since 
been employed in fleet expeditions in   
the ,north ,sea as well as for          
anti-submarine work4 ,in the latter form
 of service1 they have the same         
superiority over the aeroplane for      
observation that they possess in land   
operations4 ,the ship naturally cannot  
run the risk of remaining stationary1   
but as the speed of the balloon is the  
same as that of the ship towing it1 the 
observers do not pass over a given area 
with anything like the velocity of an   
aeroplane1 while their elevated position
 affords the same advantages for        
detecting the presence of the submerged 
submarine or the approach of enemy      
vessels4                                
,,examination ,,paper                   
,,dirigible ,,balloons   99,read        
,carefully399 ,place your name and full 
address at the head of the paper4 ,any  
cheap1 light paper like the sample      
previously sent you may be used4 ,do not

 crowd your work1 but arrange it neatly 
and legibly4 ,do not copy the answers   
from the ,instruction ,paper2 use your  
own words1 so that we may be sure you   
understand the subject4     #a4 ,what   
essential features of design did        
,meusnier's first dirigible             
incorporate8    #b4 ,describe the       
difference between rigid1 semi-rigid1   
and flexible       types of dirigibles4 
#c4 ,state the laws governing the       
increase of resistance with speed1      
the increase of power necessary for a   
given increase of speed1 and       the  
ratio in which the volume and area of   
the gas bag increase       with         
increased dimensions4    #d4 ,what      
provides the lifting power of the       
dirigible and how is this       lifting 
power utilized8 ,why should this lifting
 power be so much       less at night   
than in the daytime8 ,what is net       
lifting power8    #e4 ,what are air     
balloonets8 ,how and for what purpose   
are they used8    #f4 ,what is the most 

efficient form of envelope for the      
dirigible1 and       why8    #g4 ,why   
cannot the ordinary spherical balloon be
 propelled as a       dirigible8    #h4 
,is the form of the stern as important  
as the bow8    #i4 ,what is longitudinal
 stability and how is it obtained8      
#aj4 ,how is stability of direction     
obtained8 ,what are stabilizing         
planes8   #aa4 ,why must a form of      
suspension for the car that cannot be   
accidentally displaced with relation to 
the balloon be provided8  #ab4          
,theoretically1 where should the        
propulsive effort be applied to a       
dirigible8 ,what factors affect the     
placing of the propeller and what has   
been proved to be the most practical    
solution of the problem8    #ac4        
,discuss the advantages of the kite     
balloon over the aeroplane for          
observation4   #ad4 ,what is the effect 
of the wind on a modern kite balloon8   
#ae4 ,what is the difference between    
pounds per horsepower and pounds        

per horsepower hour as applied to the   
motor of a dirigible8 ,which       is   
more important8    #aj4 ,sketch and     
explain the ,astra-,torres suspension4  
#ag4 ,what differences exist between a  
,zeppelin and a ,schutte-,lanz          
dirigible8   #ah4 ,describe the ,l-#di1 
discussing power plant and control4     
#ai4 ,define static and dynamic         
equilibrium as applied to the dirigible4
   #bj4 ,is the ,zeppelin effective8    
,discuss fully4  99,after completing the
 work1 add and sign the following       
statement399  ,i hereby certify that the
 above work is entirely my own4         
7,signed7