,a ,,catechism ,,of ,,the ,,steam       
,,engine    ,,in ,,its ,,various        
,,applications ,,to ,,mines1  ,,mills1  
,,steam ,,navigation1 ,,railways1  ,,and
 ,,agriculture4    ,,with    ,,practical
 ,,instructions ,,for ,,the             
,,manufacture  ,,and ,,management ,,of  
,,engines ,,of ,,every ,,class4         
,,by    ,,john ,,bourne1 ,c4,e4         
,,new ,,and ,,revised ,,edition4        
,transcriber's ,note3 ,inconsistencies  
in chapter headings and numbering  of   
paragraphs and illustrations have been  
retained in this edition4      ,,preface
    ,,to ,,the ,,fourth ,,edition4      
,for some years past a new edition of   
this work has been called for1 but ,i   
was unwilling to allow a new edition to 
go forth with all the original  faults  
of the work upon its head1 and ,i have  
been too much engaged in the  practical 
construction of steam ships and steam   
engines to find time for  the thorough  
revision which ,i knew the work         
required4 ,at length1 however1 ,i  have 

sufficiently disengaged myself from     
these onerous pursuits to  accomplish   
this necessary revision2 and ,i now     
offer the work to the public1  with the 
confidence that it will be found better 
deserving of the favorable  acceptation 
and high praise it has already received4
 ,there are very few  errors1 either of 
fact or of inference1 in the early      
editions1 which ,i have  had to correct2
 but there are many omissions which ,i  
have had to supply1  and faults of      
arrangement and classification which ,i 
have had to rectify4 ,i  have also had  
to bring the information1 which the work
 professes to afford1  up to the present
 time1 so as to comprehend the latest   
improvements4    ,for the sake of       
greater distinctness the work is now    
divided into chapters4  ,some of these  
chapters are altogether new1 and the    
rest have received such  extensive      
additions and improvements as to make   
the book almost a new one4  ,one purpose
 of my emendations has been to render my

 remarks intelligible to  a tyro1 as    
well as instructive to an advanced      
student4 ,with this view1 ,i  have      
devoted the first chapter to a popular  
description of the ,steam               
,engine--which all may understand who   
can understand anything--and in the     
subsequent gradations of progress ,i    
have been careful to set no object      
before the reader for the first time1 of
 which the nature and functions are  not
 simultaneously explained4 ,the design  
,i have proposed to myself1 in the      
composition of this work1 is to take a  
young lad who knows nothing of steam    
engines1 and to lead him by easy        
advances up to the highest point of     
information ,i have myself attained2 and
 it has been a pleasing duty to me  to  
smooth for others the path which ,i     
myself found so rugged1 and to  impart1 
for the general good of mankind1 the    
secrets which others have  guarded with 
so much jealousy4 ,i believe ,i am the  
first author who has  communicated that 

practical information respecting the    
steam engine1 which  persons proposing  
to follow the business of an engineer   
desire to possess4  ,my business has1   
therefore1 been the rough business of a 
pioneer2 and while  hewing a road       
through the trackless forest1 along     
which all might hereafter  travel with  
ease1 ,i had no time to attend to those 
minute graces of  composition and petty 
perfection of arrangement and           
collocation1 which are  the attribute of
 the academic grove1 or the literary    
parterre4 ,i am1  nevertheless1 not     
insensible to the advantages of method  
and clear  arrangement in any work      
professing to instruct mankind in the   
principles  and practice of any art2 and
 many of the changes introduced into the
  present edition of this work are      
designed to render it less exceptionable
  in this respect4 ,the woodcuts now    
introduced into the work for the first  
time will1 ,i believe1 much increase its
 interest and utility2 and upon the     

whole ,i am content to dismiss it into  
circulation1 in the belief that those   
who peruse it attentively will obtain a 
more rapid and more practical           
acquaintance with the steam engine in   
its various applications1 than they     
would be likely otherwise to acquire4   
,i have only to add that ,i have        
prepared a sequel to the present work1  
in  the shape of a ,hand-,book of the   
,steam ,engine1 containing the whole of 
the  rules given in the present work1   
illustrated by examples worked out at   
length1 and also containing such useful 
tables and other data1 as the  engineer 
requires to refer to constantly in the  
course of his practice4  ,this work may 
be bound up with the ,catechism1 if     
desired1 to which it is  in fact a ,key4
    ,i shall thankfully receive from    
engineers1 either abroad or at home1    
accounts of any engines or other        
machinery1 with which they may become   
familiar in their several localities2   
and ,i shall be happy1 in my turn1 to   

answer any inquiries on engineering     
subjects which fall within the compass  
of my information4 ,if young engineers  
meet with any difficulty in their       
studies1 ,i shall be happy to resolve it
 if ,i can2 and they may communicate    
with me upon any such point without     
hesitation1 in whatever quarter of the  
world they may happen to be4      ,,john
 ,,bourne4  #i ,,billiter ,,street1     
,,london1    ,march #ast1 #ahef4        
,,preface    ,,to ,,the ,,fifth         
,,edition4    ,the last edition of the  
present work1 consisting of #c1ejj      
copies1 having  been all sold off in    
about ten months1 ,i now issue another  
edition1 the  demand for the work being 
still unabated4 ,it affords1 certainly1 
some  presumption that a work in some   
measure supplies an ascertained want1   
when1  though addressing only a limited 
circle--discoursing only of technical   
questions1 and without any accident to  
stimulate it into notoriety1--it        
attains so large a circulation as the   

present work has reached4 ,besides      
being reprinted in ,america1 it has been
 translated into ,german1 ,french1      
,dutch1 and ,i believe1 into some other 
languages1 so that there is1 perhaps1   
not too much vanity in the inference    
that it has been found serviceable to   
those perusing it4 ,i can with truth    
say1 that the hope of rendering some    
service to mankind1 in my day and       
generation1 has been my chief inducement
  in writing it1 and if this end is     
fulfilled1 ,i have nothing further to   
desire4    ,i regret that circumstances 
have prevented me from yet issuing the  
,hand-,book which ,i have had for some  
time in preparation1 and to which1 in   
my ,preface of the last year1 ,i        
referred4 ,i hope to have sufficient    
leisure  shortly1 to give that and some 
other of my literary designs the        
necessary  attention4 ,whatever may have
 been the other impediments to a more   
prolific  authorship1 certainly one of  
them has not been the coldness of the   

approbation with which my efforts have  
been received1 since my past            
performances seem to me to have met with
 an appreciation far exceeding  their   
deserts4    ,,john ,,bourne4            
,february #b;d1 #aheg4                  
,,publishers' ,,notice4      ,in        
offering to the ,american public a      
reprint of a work on the ,steam ,engine 
so deservedly successful1 and so long   
considered standard1 the publishers     
have not thought it necessary that it   
should be an exact copy of the  ,english
 edition2 there were some details in    
which they thought it could be          
improved1 and better adapted to the use 
of ,american engineers4 ,on this        
account1 the size of the page has been  
increased to a full #abmo1 to admit  of 
larger illustrations1 which in the      
,english edition are often on too  small
 a scale2 and some of the illustrations 
themselves have been supplied  by others
 equally applicable1 more recent1 and to
 us more familiar  examples4 ,the first 

part of ,chapter ,,xi1 devoted in the   
,english edition to  ,english portable  
and fixed agricultural engines1 in this 
edition gives  place entirely to        
illustrations from ,american practice1  
of steam engines as  applied to         
different purposes1 and of appliances   
and machines necessary to  them4 ,but   
with the exception of some of the       
illustrations and the  description of   
them1 and the correction of a few       
typographical errors1 this  edition is a
 faithful transcript of the latest      
,english edition4          ,,contents4  
,classification of ,engines4    ,nature 
and uses of a ,vacuum4    ,velocity of  
falling ,bodies and ,momentum of moving 
,bodies4    ,central ,forces4           
,centres of ,gravity1 ,gyration1 and    
,oscillation4    ,the ,pendulum and     
,governor4    ,the ,mechanical ,powers4 
,friction4    ,strength of materials and
 ,strains subsisting in ,machines4      
,,chap4 ,i4--,,general ,,description    
,,of ,,the ,,steam ,,engine4    ,the    

,boiler4    ,the ,engine4    ,the       
,marine ,engine4    ,screw ,engines4    
,the ,locomotive ,engine4      ,,chap4  
,,ii4--,,heat1 ,,combustion1 ,,and      
,,steam4    ,heat4    ,combustion4      
,steam4      ,,chap4 ,,iii4--,,expansion
 ,,of ,,steam ,,and ,,action ,,of ,,the 
,,valves4      ,,chap4 ,,iv4--,,modes   
,,of ,,estimating ,,the ,,power ,,and   
,,performance ,,of  ,,engines ,,and     
,,boilers4    ,horses ,power4    ,duty  
of ,engines and ,boilers4    ,the       
,indicator4    ,dynamometer1 ,gauges1   
and ,cataract4      ,,chap4             
,v4--,,proportions ,,of ,,boilers4      
,heating and ,fire ,grate ,surface4     
,calorimeter and ,vent4    ,evaporative 
,power of ,boilers4    ,modern ,marine  
and ,locomotive ,boilers4    ,the ,blast
 in ,locomotives4    ,boiler ,chimneys4 
,steam ,room and ,priming4    ,strength 
of ,boilers4    ,boiler ,explosions4    
,,chap4 ,,vi4--,,proportions ,,of       
,,engines4    ,steam ,passages4    ,air 
,pump1 ,condenser1 and ,hot and ,cold   

,water ,pumps4    ,fly ,wheel4          
,strengths of ,land ,engines4           
,strengths of ,marine and ,locomotive   
,engines4      ,,chap4                  
,,vii4--,,constructive ,,details ,,of   
,,boilers4    ,land and ,marine         
,boilers4    ,incrustation and          
,corrosion of ,boilers4    ,locomotive  
,boilers4      ,,chap4                  
,,viii4--,,constructive ,,details ,,of  
,,engines4    ,pumping ,engines4        
,various forms of ,marine ,engines4     
,cylinders1 ,pistons1 and ,valves4      
,air ,pump and ,condenser4    ,pumps1   
,cocks1 and ,pipes4    ,details of the  
,screw and ,screw ,shaft4    ,details of
 the ,paddles and ,paddle ,shaft4       
,the ,locomotive ,engine4      ,,chap4  
,,ix4--,,steam ,,navigation4            
,resistance of ,vessels in ,water4      
,experiments on the ,resistance of      
,vessels4    ,influence of the size of  
,vessels upon their ,speed4             
,structure and ,operation of ,paddle    
,wheels4    ,configuration and ,action  

of the ,screw4    ,comparative          
,advantages of ,paddle and ,screw       
,vessels4    ,comparative ,advantages of
 different kinds of ,screws4            
,proportions of ,screws4    ,screw      
,vessels with full and auxiliary ,power4
    ,screw and ,paddles combined4       
,,chap4 ,x4--,,examples ,,of ,,engines  
,,of ,,recent ,,construction4           
,oscillating ,paddle ,engines4          
,direct acting ,screw ,engine4          
,locomotive ,engine4      ,,chap4       
,,xi4--,,on ,,various ,,forms ,,and     
,,applications ,,of ,,the ,,steam       
,,engine4    ,governor4    ,donkey      
,pumps4    ,portable ,steam ,engines4   
,stationary ,engines4    ,steam ,fire   
,engines4    ,steam ,excavator4         
,,chap4 ,,xii4--,,manufacture ,,and     
,,management ,,of ,,steam ,,engines4    
,construction of ,engines4    ,erection 
of ,engines4    ,management of ,marine  
,boilers4    ,management of ,marine     
,engines4    ,management of             
,locomotives4          ,,mechanical     

,,principles ,,of ,,the ,,steam         
,,engine4        ,,classification ,,of  
,,engines4      #a4 ,q4--,what is meant 
by a vacuum8    ,a4--,a vacuum means an 
empty space2 a space in which there is  
neither  water nor air1 nor anything    
else that we know of4    #b4            
,q4--,wherein does a high pressure      
differ from a low pressure engine8      
,a4--,in a high pressure engine the     
steam1 after having pushed the piston   
to the end of the stroke1 escapes into  
the atmosphere1 and the impelling  force
 is therefore that due to the difference
 between the pressure of the  steam and 
the pressure of the atmosphere4 ,in the 
condensing engine the  steam1 after     
having pressed the piston to the end of 
the stroke1 passes  into the condenser1 
in which a vacuum is maintained1 and the
 impelling  force is that due to the    
difference between the pressure of the  
steam above  the piston1 and the        
pressure of the vacuum beneath it1 which
 is nothing2  or1 in other words1 you   

have then the whole pressure of the     
steam urging  the piston1 consisting of 
the pressure shown by the safety-valve  
on the  boiler1 and the pressure of the 
atmosphere besides4    #c4 ,q4--,in what
 way would you class the various kinds  
of condensing  engines8    ,a4--,into   
single acting1 rotative1 and rotatory   
engines4 ,single acting  engines are    
engines without a crank1 such as are    
used for pumping water4  ,rotative      
engines are engines provided with a     
crank1 by means of which a  rotative    
motion is produced2 and in this         
important class stand marine and  mill  
engines1 and all engines1 indeed1 in    
which the rectilinear motion of  the    
piston is changed into a circular       
motion4 ,in rotatory engines the steam  
acts at once in the production of       
circular motion1 either upon a revolving
  piston or otherwise1 but without the  
use of any intermediate mechanism1  such
 as the crank1 for deriving a circular  
from a rectilinear motion4  ,rotatory   

engines have not hitherto been very     
successful1 so that only the  single    
acting or pumping engine1 and the double
 acting or rotative engine  can be said 
to be in actual use4 ,for some purposes1
 such1 for example1 as  forcing air into
 furnaces for smelting iron1 double     
acting engines are  employed1 which are 
nevertheless unfurnished with a crank2  
but engines of  this kind are not       
sufficiently numerous to justify their  
classification as  a distinct species1  
and1 in general1 those engines may be   
considered to be  single acting1 by     
which no rotatory motion is imparted4   
#d4 ,q4--,is not the circular motion    
derived from a cylinder engine very     
irregular1 in consequence of the unequal
 leverage of the crank at the  different
 parts of its revolution8    ,a4--,no2  
rotative engines are generally provided 
with a fly-wheel to  correct such       
irregularities by its momentum2 but     
where two engines with  their respective
 cranks set at right angles are         

employed1 the irregularity  of one      
engine corrects that of the other with  
sufficient exactitude for  many         
purposes4 ,in the case of marine and    
locomotive engines1 a fly-wheel is  not 
employed2 but for cotton spinning1 and  
other purposes requiring great          
regularity of motion1 its use with      
common engines is indispensable1 though 
it is not impossible to supersede the   
necessity by new contrivances4    #e4   
,q4--,you implied that there is some    
other difference between single  acting 
and double acting engines1 than that    
which lies in the use or  exclusion of  
the crank8    ,a4--,yes2 single acting  
engines act only in one way by the force
 of the  steam1 and are returned by a   
counter-weight2 whereas double acting   
engines  are urged by the steam in both 
directions4 ,engines1 as ,i have already
 said1  are sometimes made double       
acting1 though unprovided with a crank2 
and there  would be no difficulty in so 
arranging the valves of all ordinary    

pumping  engines1 as to admit of this   
action2 for the pumps might be contrived
 to  raise water both by the upward and 
downward stroke1 as indeed in some mines
  is already done4 ,but engines without 
a crank are almost always made single   
acting1 perhaps from the effect of      
custom1 as much as from any other       
reason1 and are usually spoken of as    
such1 though it is necessary to know    
that there are some deviations from the 
usual practice4        ,,nature ,,and   
,,uses ,,of ,a ,,vacuum4    #f4         
,q4--,the pressure of a vacuum you have 
stated is nothing2 but how can  the     
pressure of a vacuum be said to be      
nothing1 when a vacuum occasions a      
pressure of #ae lbs4 on the square inch8
    ,a4--,because it is not the vacuum  
which exerts this pressure1 but the     
atmosphere1 which1 like a head of water1
 presses on everything immerged  beneath
 it4 ,a head of water1 however1 would   
not press down a piston1 if the  water  
were admitted on both of its sides2 for 

an equilibrium would then be            
established1 just as in the case of a   
balance which retains its equilibrium   
when an equal weight is added to each   
scale2 but take the weight out of one   
scale1 or empty the water from one side 
of the piston1 and motion or  pressure  
is produced2 and in like manner pressure
 is produced on a piston  by admitting  
steam or air upon the one side1 and     
withdrawing the steam or  air from the  
other side4 ,it is not1 therefore1 to a 
vacuum1 but rather to  the existence of 
an unbalanced plenum1 that the pressure 
made manifest by  exhaustion is due1 and
 it is obvious therefore that a vacuum  
of itself  would not work an engine4    
#g4 ,q4--,how is the vacuum maintained  
in a condensing engine8    ,a4--,the    
steam1 after having performed its office
 in the cylinder1 is  permitted to pass 
into a vessel called the condenser1     
where a shower of  cold water is        
discharged upon it4 ,the steam is       
condensed by the cold water1  and falls 

in the form of hot water to the bottom  
of the condenser4 ,the  water1 which    
would else be accumulated in the        
condenser1 is continually  being pumped 
out by a pump worked by the engine4     
,this pump is called the  air pump1     
because it also discharges any air which
 may have entered with  the water4      
#h4 ,q4--,if a vacuum be an empty space1
 and there be water in the  condenser1  
how can there be a vacuum there8        
,a4--,there is a vacuum above the water1
 the water being only like so much  iron
 or lead lying at the bottom4    #i4    
,q4--,is the vacuum in the condenser a  
perfect vacuum8    ,a4--,not quite      
perfect2 for the cold water entering for
 the purpose of  condensation is heated 
by the steam1 and emits a vapor of a    
tension  represented by about three     
inches of mercury2 that is1 when the    
common  barometer stands at #cj inches1 
a barometer with the space above the    
mercury  communicating with the         
condenser1 will stand at about #bg      

inches4    #aj4 ,q4--,is this           
imperfection of the vacuum wholly       
attributable to the  vapor in the       
condenser8    ,a4--,no2 it is partly    
attributable to the presence of a small 
quantity of  air which enters with the  
water1 and which would accumulate until 
it  destroyed the vacuum altogether but 
for the action of the air pump1 which   
expels it with the water1 as already    
explained4 ,all common water contains a 
certain quantity of air in solution1 and
 this air recovers its elasticity  when 
the pressure of the atmosphere is taken 
off1 just as the gas in soda  water     
flies up so soon as the cork of the     
bottle is withdrawn4    #aa4 ,q4--,is a 
barometer sometimes applied to the      
condensers of steam  engines8           
,a4--,yes2 and it is called the vacuum  
gauge1 because it shows the degree  of  
perfection the vacuum has attained4     
,another gauge1 called the steam  gauge1
 is applied to the boiler1 which        
indicates the pressure of the steam  by 

the height to which the steam forces    
mercury up a tube4 ,gauges are also     
applied to the boiler to indicate the   
height of the water within it so that   
it may not be burned out by the water   
becoming accidentally too low4 ,in  some
 cases a succession of cocks placed a   
short distance above one another  are   
employed for this purpose1 and in other 
cases a glass tube is placed            
perpendicularly in the front of the     
boiler and communicating at each end    
with its interior4 ,the water rises in  
this tube to the same height as in  the 
boiler itself1 and thus shows the actual
 water level4 ,in most of the  modern   
boilers both of these contrivances are  
adopted4    #ab4 ,q4--,can a condensing 
engine be worked with a pressure less   
than that  of the atmosphere8           
,a4--,yes1 if once it be started2 but it
 will be a difficult thing to start  an 
engine1 if the pressure of the steam be 
not greater than that of the            
atmosphere4 ,before an engine can be    

started1 it has to be blown through     
with steam to displace the air within   
it1 and this cannot be effectually  done
 if the pressure of the steam be very   
low4 ,after the engine is started1      
however1 the pressure in the boiler may 
be lowered1 if the engine be  lightly   
loaded1 until there is a partial vacuum 
in the boiler4 ,such a  practice1       
however1 is not to be commended1 as the 
gauge cocks become  useless when there  
is a partial vacuum in the boiler2      
inasmuch as1 when  they are opened1 the 
water will not rush out1 but air will   
rush in4 ,it is  impossible1 also1 under
 such circumstances1 to blow out any of 
the sediment  collected within the      
boiler1 which1 in the case of the       
boilers of steam  vessels1 requires to  
be done every two hours or oftener4     
,this is  accomplished by opening a     
large cock which permits some of the    
supersalted  water to be forced         
overboard by the pressure of the steam4 
,in some cases1  in which the boiler    

applied to an engine is of inadequate   
size1 the  pressure within the boiler   
will fall spontaneously to a point      
considerably  beneath the pressure of   
the atmosphere2 but it is preferable1 in
 such  cases1 partially to close the    
throttle valve in the steam pipe1       
whereby the  issue of steam to the      
engine is diminished2 and the pressure  
in the boiler  is thus maintained1 while
 the cylinder receives its former       
supply4    #ac4 ,q4--,if a hole be      
opened into a condenser of a steam      
engine1 will air  rush into it8         
,a4--,if the hole communicates with the 
atmosphere1 the air will be drawn  in4  
#ad4 ,q4--,with what ,velocity does air 
rush into a vacuum8    ,a4--,with the   
velocity which a body would acquire by  
falling from the  height of a           
homogeneous atmosphere1 which is an     
atmosphere of the same  density         
throughout as at the earth's surface2   
and although such an  atmosphere does   
not exist in nature1 its existence is   

supposed1 in order to  facilitate the   
computation4 ,it is well known that the 
velocity with which  water issues from a
 cistern is the same that would be      
acquired by a body  falling from the    
level of the head to the level of the   
issuing point2 which  indeed is an      
obvious law1 since every particle of    
water descends and issues  by virtue of 
its gravity1 and is in its descent      
subject to the ordinary  laws of falling
 bodies4 ,air rushing into a vacuum is  
only another example  of the same       
general principle3 the velocity of each 
particle will be that  due to the height
 of the column of air which would       
produce the pressure  sustained2 and the
 weight of air being known1 as well as  
the pressure it  exerts on the earth's  
surface1 it becomes easy to tell what   
height a column  of air1 an inch square1
 and of the atmospheric density1 would  
require to  be1 to weigh #ae lbs4 ,the  
height would be #bg1hah feet1 and the   
velocity  which the fall of a body from 

such a height produces would be #a1cch  
feet  per second4        ,,velocity ,,of
 ,,falling ,,bodies ,,and ,,momentum    
,,of ,,moving ,,bodies4    #ae4         
,q4--,how do you determine the velocity 
of falling bodies of different  kinds8  
,a4--,all bodies fall with the same     
velocity1 when there is no resistance   
from the atmosphere1 as is shown by the 
experiment of letting fall1 from  the   
top of a tall exhausted receiver1 a     
feather and a guinea1 which reach  the  
bottom at the same time4 ,the velocity  
of falling bodies is one that is        
accelerated uniformly1 according to a   
known law4 ,when the height from which  
a body falls is given1 the velocity     
acquired at the end of the descent can  
be easily computed4 ,it has been found  
by experiment that the square root of   
the height in feet multiplied by #h4jba 
will give the velocity4    #af4         
,q4--,but the velocity in what terms8   
,a4--,in feet per second4 ,the distance 
through which a body falls by  gravity  

in one second is #af-a_/ab feet2 in two 
seconds1 #fd-d_/ab feet2 in  three      
seconds1 #add-i_/ab feet2 in four       
seconds1 #beg-d_/ab feet1 and so on4 ,if
  the number of feet fallen through in  
one second be taken as unity1 then the  
relation of the times to the spaces will
 be as follows3--    ,number of seconds 
#a #b #c #d #e #f  ,units of space      
passed through    #a #d #iafbecf c4     
so that it appears that the spaces      
passed through by a falling body are as 
the squares of the times of falling4    
#ag4 ,q4--,is not the urging force which
 causes bodies to fall the force of     
gravity8    ,a4--,yes2 the force of     
gravity or the attraction of the earth4 
#ah4 ,q4--,and is not that a uniform    
force1 or a force acting with a uniform 
pressure8    ,a4--,it is4    #ai4       
,q4--,therefore during the first second 
of falling as much impelling  power will
 be given by the force of gravity as    
during every succeeding  second8        
,a4--,undoubtedly4    #bj4 ,q4--,how    

comes it1 then1 that while the body     
falls #fd-d_/ab feet in two  seconds1 it
 falls only #af-a_/ab feet in one       
second2 or why1 since it falls  only    
#af-a_/ab feet in one second1 should it 
fall more than twice #af-a_/ab  feet in 
two8    ,a4--,because #af-a_/ab feet is 
the average and not the maximum velocity
  during the first second4 ,the velocity
 acquired at the end of the #ast  second
 is not #af-a_/ab1 but #cb-a_/f feet per
 second1 and at the end of the #b;d     
second a velocity of #cb-a_/f feet has  
to be added2 so that the total  velocity
 at the end of the #b;d second becomes  
#fd-b_/f feet2 at the end of the  #c;d1 
the velocity becomes #if-c_/f feet1 at  
the end of the #dth1 #abh-d_/f feet1    
and so on4 ,these numbers proceed in the
 progression #a1 #b1 #c1 #d1 c41 so     
that it appears that the velocities     
acquired by a falling body at different 
points1 are simply as the times of      
falling4 ,but if the velocities be as   
the  times1 and the total space passed  

through be as the squares of the times1 
then the total space passed through must
 be as the squares of the velocity2  and
 as the vis viva or mechanical power    
inherent in a falling body1 of  any     
given weight1 is measurable by the      
height through which it descends1 it    
follows that the vis viva is            
proportionate to the square of the      
velocity4  ,of two balls therefore1 of  
equal weight1 but one moving twice as   
fast as  the other1 the faster ball has 
four times the energy or mechanical     
force  accumulated in it that the slower
 ball has4 ,if the speed of a fly-wheel 
be  doubled1 it has four times the vis  
viva it possessed before--vis viva      
being measurable by a reference to the  
height through which a body must  have  
fallen1 to acquire the velocity given4  
#ba4 ,q4--,by what considerations is the
 vis viva or mechanical energy  proper  
for the fly-wheel of an engine          
determined8    ,a4--,by a reference to  
the power produced every half-stroke of 

the engine1  joined to the consideration
 of what relation the energy of the     
fly-wheel  rim must have thereto1 to    
keep the irregularities of motion within
 the  limits which are admissible4 ,it  
is found in practice1 that when the     
power  resident in the fly-wheel rim1   
when the engine moves at its average    
speed1  is from two and a half to four  
times greater than the power generated  
by  the engine in one half-stroke--the  
variation1 depending on the energy      
inherent in the machinery the engine has
 to drive and the equability of  motion 
required--the engine will work with     
sufficient regularity for most  ordinary
 purposes1 but where great equability of
 motion is required1 it  will be        
advisable to make the power resident in 
the fly-wheel equal to six  times the   
power generated by the engine in one    
half-stroke4    #bb4 ,q4---,can you give
 a practical rule for determining the   
proper  quantity of cast iron for the   
rim of a fly-wheel in ordinary land     

engines8    ,a4--,one rule frequently   
adopted is as follows3--,multiply the   
mean  diameter of the rim by the number 
of its revolutions per minute1 and      
square  the product for a divisor2      
divide the number of actual horse power 
of the  engine by the number of strokes 
the piston makes per minute1 multiply   
the  quotient by the constant number    
#b1gfj1jjj1 and divide the product by   
the  divisor found as above2 the        
quotient is the requisite quantity of   
cast iron  in cubic feet to form the    
fly-wheel rim4    #bc4 ,q4--,what is    
,boulton and ,watt's rule for finding   
the dimensions of the  fly-wheel8       
,a4--,boulton and ,watt's rule for      
finding the dimensions of the fly-wheel 
is as follows3--,multiply #dd1jjj times 
the length of the stroke in feet by  the
 square of the diameter of the cylinder 
in inches1 and divide the  product by   
the square of the number of revolutions 
per minute multiplied by  the cube of   
the diameter of the fly-wheel in feet4  

,the resulting number  will be the      
sectional area of the rim of the        
fly-wheel in square inches4             
,,central ,,forces4    #bd4 ,q4--,what  
do you understand by centrifugal and    
centripetal forces8    ,a4--,by         
centrifugal force1 ,i understand the    
force with which a revolving  body tends
 to fly from the centre2 and by         
centripetal force1 ,i understand  any   
force which draws it to the centre1 or  
counteracts the centrifugal  tendency4  
,in the conical pendulum1 or steam      
engine governor1 which consists  of two 
metal balls suspended on rods hung from 
the end of a vertical  revolving shaft1 
the centrifugal force is manifested by  
the divergence of  the balls1 when the  
shaft is put into revolution2 and the   
centripetal  force1 which in this       
instance is gravity1 predominates so    
soon as the  velocity is arrested2 for  
the arms then collapse and hang by the  
side of  the shaft4    #be4 ,q4--,what  
measures are there of the centrifugal   

force of bodies  revolving in a circle8 
,a4--,the centrifugal force of bodies   
revolving in a circle increases as  the 
diameter of the circle1 if the number of
 revolutions remain the same4  ,if there
 be two fly-wheels of the same weight1  
and making the same number  of          
revolutions per minute1 but the diameter
 of one be double that of the  other1   
the larger will have double the amount  
of centrifugal force4 ,the  centrifugal 
force of the same wheel1 however1       
increases as the square of  the         
velocity2 so that if the velocity of a  
fly-wheel be doubled1 it will  have four
 times the amount of centrifugal force4 
#bf4 ,q4--,can you give a rule for      
determining the centrifugal force of a  
body of a given weight moving with a    
given velocity in a circle of a given   
diameter8    ,a4--,yes4 ,if the velocity
 in feet per second be divided by #d4ja1
 the  square of the quotient will be    
four times the height in feet from which
 a  body must have fallen to have       

acquired that velocity4 ,divide this    
quadruple  height by the diameter of the
 circle1 and the quotient is the        
centrifugal  force in terms of the      
weight of the body1 so that1 multiplying
 the quotient  by the actual weight of  
the body1 we have the centrifugal force 
in pounds  or tons4 ,another rule is to 
multiply the square of the number of    
revolutions per minute by the diameter  
of the circle in feet1 and to divide    
the product by #e1hgj4 ,the quotient is 
the centrifugal force in terms of the   
weight of the body4    #bg4 ,q4--,how do
 you find the velocity of the body when 
its centrifugal  force and the diameter 
of the circle in which it moves are     
given8    ,a4--,multiply the centrifugal
 force in terms of the weight of the    
body by  the diameter of the circle in  
feet1 and multiply the square root of   
the  product by #d4ja2 the result will  
be the velocity of the body in feet per 
second4    #bh4 ,q4--,will you          
illustrate this by finding the velocity 

at which the  cast iron rim of a        
fly-wheel #aj feet in diameter would    
burst asunder by its  centrifugal force8
    ,a4--,if we take the tensile        
strength of cast iron at #ae1jjj lbs4   
per  square inch1 a fly-wheel rim of one
 square inch of sectional area would    
sustain #cj1jjj lbs4 ,if we suppose one 
half of the rim to be so fixed to the   
shaft as to be incapable of detachment1 
then the centrifugal force of the  other
 half of the rim at the moment of       
rupture must be equal to #cj1jjj lbs4   
,now #cj1jjj lbs4 divided by #di4dh 7the
 weight of the half rim7 is equal to    
#fjf4c1 which is the centrifugal force  
in terms of the weight4 ,then by the    
rule given in the last answer #fjf4c x  
#aj  #fjfc1 the square root of which  is
 #gh nearly1 and #gh x #d4ja  #cab4gh1  
the velocity of the rim in feet per     
second at the moment of rupture4    #bi4
 ,q4--,what is the greatest velocity at 
which it is safe to drive a cast  iron  
fly-wheel8    ,a4--,if we take #b1jjj   

lbs4 as the utmost strain per square    
inch to which  cast iron can be         
permanently subjected with safety2 then1
 by a similar  process to that just     
explained1 we have #d1jjj lbs4_/#di4dh  
#hj4h which  multiplied by #aj  #hjh1   
the square root of which is #bh4d1 and  
#bh4d x #d4ja   #aac4hhd1 the velocity  
of the rim in feet per second1 which may
 be  considered as the highest          
consistent with safety4 ,indeed1 this   
limit should  not be approached in      
practice on account of the risks of     
fracture from  weakness or imperfections
 in the metal4    #cj4 ,q4--,what is the
 velocity at which the wheels of railway
 trains may  run if we take #d1jjj lbs4 
per square inch as the greatest strain  
to which  malleable iron should be      
subjected8    ,a4--,the weight of a     
malleable iron rim of one square inch   
sectional area  and #g feet diameter is 
#ba4iia feet x #c4d lbs4  #gd4gf1 one   
half of which is  #cg4d lbs4 ,then by   
the same process as before1 #h1jjj_/cg4d

  #bac4i1 the  centrifugal force in     
terms of the weight3 #bac4i x #g1 the   
diameter of the  wheel  #adig4c1 the    
square root of which1 #ch4c x #d4ja     
#aee4ahg feet per  second1 the highest  
velocity of the rims of railway carriage
 wheels that is  consistent with safety4
 #aee4ahg feet per second is equivalent 
to #aje4h  miles an hour4 ,as #d1jjj    
lbs4 per square inch of sectional area  
is the  utmost strain to which iron     
should be exposed in machinery1 railway 
wheels  can scarcely be considered safe 
at speed even considerably under #ajj   
miles  an hour1 unless so constructed   
that the centrifugal force of the rim   
will  be counteracted1 to a material    
extent1 by the centripetal action of the
  arms4 ,hooped wheels are very unsafe1 
unless the hoops are1 by some process   
or other1 firmly attached to the arms4  
,it is of no use to increase the        
dimensions of the rim of a wheel with   
the view of giving increased strength   
to counteract the centrifugal force1 as 

every increase in the weight of the  rim
 will increase the centrifugal force in 
the same proportion4        ,,centres   
,,of ,,gravity1 ,,gyration1 ,,and       
,,oscillation4    #ca4 ,q4--,what do you
 understand by the centre of gravity of 
a body8    ,a4--,that point within it1  
in which the whole of the weight may be 
supposed to be concentrated1 and which  
continually endeavors to gain the       
lowest possible position4 ,a body hung  
in the centre of gravity will remain  at
 rest in any position4    #cb4          
,q4--,what is meant by the centre of    
gyration8    ,a4--,the centre of        
gyration is that point in a revolving   
body in which the  whole momentum may be
 conceived to be concentrated1 or in    
which the whole  effect of the momentum 
resides4 ,if the ball of a governor were
 to be moved  in a straight line1 the   
momentum might be said to be            
concentrated at the  centre of gravity  
of the ball2 but inasmuch as1 by its    
revolution round an  axis1 the part of  

the ball furthest removed from the axis 
moves more  quickly than the part       
nearest to it1 the momentum cannot be   
supposed to be  concentrated at the     
centre of gravity1 but at a point       
further removed from  the central shaft1
 and that point is what is called the   
centre of gyration4    #cc4 ,q4--,what  
is the centre of oscillation8           
,a4--,the centre of oscillation is a    
point in a pendulum or any swinging     
body1 such1 that if all the matter of   
the body were to be collected into  that
 point1 the velocity of its vibration   
would remain unaffected4 ,it is in  fact
 the mean distance from the centre of   
suspension of every atom1 in a  ratio   
which happens not to be an arithmetical 
one4 ,the centre of  oscillation is     
always in a line passing through the    
centre of suspension  and the centre of 
gravity4        ,,the ,,pendulum ,,and  
,,governor4    #cd4 ,q4--,by what       
circumstance is the velocity of         
vibration of a pendulous  body          

determined8    ,a4--,by the length of   
the suspending rod only1 or1 more       
correctly1 by the  distance between the 
centre of suspension and the centre of  
oscillation4  ,the length of the arc    
described does not signify1 as the times
 of vibration  will be the same1 whether
 the arc be the fourth or the four      
hundredth of a  circle1 or at least they
 will be nearly so1 and would be so     
exactly1 if the  curve described were a 
portion of a cycloid4 ,in the pendulum  
of clocks1  therefore1 a small arc is   
preferred1 as there is1 in that case1 no
 sensible  deviation from the cycloidal 
curve1 but in other respects the size of
 the  arc does not signify4    #ce4     
,q4--,if then the length of a pendulum  
be given1 can the number of  vibrations 
in a given time be determined8          
,a4--,yes2 the time of vibration bears  
the same relation to the time in  which 
a body would fall through a space equal 
to half the length of the  pendulum1    
that the circumference of a circle bears

 to its diameter4 ,the  number of       
vibrations made in a given time by      
pendulums of different  lengths1 is     
inversely as the square roots of their  
lengths4    #cf4 ,q4--,then when the    
length of the second's pendulum is known
 the proper  length of a pendulum to    
make any given number of vibrations in  
the minute  can readily be computed8    
,a4--,yes2 the length of the second's   
pendulum being known1 the length of     
another pendulum1 required to perform   
any given number of vibrations in the   
minute1 may be obtained by the following
 rule3 multiply the square root of  the 
given length by #fj1 and divide the     
product by the given number of          
vibrations per minute2 the square of the
 quotient is the length of pendulum     
required4 ,thus if the length of a      
pendulum were required that would make  
#gj  vibrations per minute in the       
latitude of ,london1 then               
,,sqrt7#ci4acic7 x #fj_/gj   7#e4cfc7b  
#bh4ge in4 which is the length required4

    #cg4 ,q4--,can you explain how it   
comes that the length of a pendulum     
determines the number of vibrations it  
makes in a given time8    ,a4--,because 
the length of the pendulum determines   
the steepness of the  circle in which   
the body moves1 and it is obvious1 that 
a body will descend  more rapidly over a
 steep inclined plane1 or a steep arc of
 a circle1 than  over one in which there
 is but a slight inclination4 ,the      
impelling force is  gravity1 which urges
 the body with a force proportionate to 
the distance  descended1 and if the     
velocity due to the descent of a body   
through a given  height be spread over a
 great horizontal distance1 the speed of
 the body  must be slow in proportion to
 the greatness of that distance4 ,it is 
clear1  therefore1 that as the length of
 the pendulum determines the steepness  
of  the arc1 it must also determine the 
velocity of vibration4    #ch4 ,q4--,if 
the motions of a pendulum be dependent  
on the speed with which  a body falls1  

then a certain ratio must subsist       
between the distance  through which a   
body falls in a second1 and the length  
of the second's  pendulum8    ,a4--,and 
so there is2 the length of the second's 
pendulum at the level of  the sea in    
,london1 is #ci4acic inches1 and it is  
from the length of the  second's        
pendulum that the space through which a 
body falls in a second has  been        
determined4 ,as the time in which a     
pendulum vibrates is to the time in     
which a heavy body falls through half   
the length of the pendulum1 as the      
circumference of a circle is to its     
diameter1 and as the height through     
which a body falls is as the square of  
the time of falling1 it is clear  that  
the height through which a body will    
fall1 during the vibration of a         
pendulum1 is to half the length of the  
pendulum as the square of the           
circumference of a circle is to the     
square of its diameter2 namely1 as      
#i4hfif is to #a1 or it is to the whole 

length of the pendulum as the half of   
this1 namely1 #d4icdh is to #a2 and     
#d4icdh times #ci4acic in4 is #af-a_/ab 
ft4  very nearly1 which is the space    
through which a body falls by gravity in
 a  second4    #ci4 ,q4--,are the       
motions of the conical pendulum or      
governor reducible to  the same laws    
which apply to the common pendulum8     
,a4--,yes2 the motion of the conical    
pendulum may be supposed to be          
compounded of the motions of two common 
pendulums1 vibrating at right  angles to
 one another1 and one revolution of a   
conical pendulum will be  performed in  
the same time as two vibrations of a    
common pendulum1 of which  the length is
 equal to the vertical height of the    
point of suspension above  the plane of 
revolution of the balls4    #dj4        
,q4--,is not the conical pendulum or    
governor of a steam engine driven  by   
the engine8    ,a4--,yes4    #da4       
,q4--,then will it not be driven round  
as any other mechanism would be  at a   

speed proportional to that of the       
engine8    ,a4--,it will4    #db4       
,q4--,then how can the length of the    
arms affect the time of  revolution8    
,illustration3 ,fig4 #a4    ,a4--,by    
flying out until they assume a vertical 
height answering to the  velocity with  
which they rotate round the central     
axis4 ,as the speed is  increased the   
balls expand1 and the height of the cone
 described by the  arms is diminished1  
until its vertical height is such that a
 pendulum of  that length would perform 
two vibrations for every revolution of  
the  governor4 ,by the outward motion of
 the arms1 they partially shut off the  
steam from the engine4 ,if1 therefore1 a
 certain expansion of the balls be      
desired1 and a certain length be fixed  
upon for the arms1 so that the  vertical
 height of the cone is fixed1 then the  
speed of the governor must  be such1    
that it will make half the number of    
revolutions in a given time  that a     
pendulum equal in length to the height  

of the cone would make of  vibrations4  
,the rule is1 multiply the square root  
of the height of the cone  in inches by 
#j4caihf1 and the product will be the   
right time of revolution  in seconds4   
,if the number of revolutions and the   
length of the arms be  fixed1 and it is 
wanted to know what is the diameter of  
the circle  described by the balls1 you 
must divide the constant number #ahg4eh 
by the  number of revolutions per       
minute1 and the square of the quotient  
will be  the vertical height in inches  
of the centre of suspension above the   
plane  of the balls' revolution4 ,deduct
 the square of the vertical height in   
inches from the square of the length of 
the arm in inches1 and twice the  square
 root of the remainder is the diameter  
of the circle in which the  centres of  
the balls revolve4    #dc4 ,q4 ,cannot  
the operation of a governor be deduced  
merely from the  consideration of       
centrifugal and centripetal forces8     
,a4--,it can2 and by a very simple      

process4 ,the horizontal distance of the
  arm from the spindle divided by the   
vertical height1 will give the amount   
of centripetal force1 and the velocity  
of revolution requisite to produce  an  
equivalent centrifugal force may be     
found by multiplying the centripetal    
force of the ball in terms of its own   
weight by #gj1ddj1 and dividing the     
product by the diameter of the circle   
made by the centre of the ball in       
inches2 the square root of the quotient 
is the number of revolutions per        
minute4 ,by this rule you fix the length
 of the arms1 and the diameter of  the  
base of the cone1 or1 what is the same  
thing1 the angle at which it is  desired
 the arms shall revolve1 and you then   
make the speed or number of  revolutions
 such1 that the centrifugal force will  
keep the balls in the  desired position4
    #dd4 ,q4--,does not the weight of   
the balls affect the question8          
,a4--,not in the least2 each ball may be
 supposed to be made up of a number  of 

small balls or particles1 and each      
particle of matter will act for  itself4
 ,heavy balls attached to a governor are
 only requisite to overcome  the        
friction of the throttle valve which    
shuts off the steam1 and of the         
connections leading thereto4 ,though the
 weight of a ball increases its         
centripetal force1 it increases its     
centrifugal force in the same           
proportion4        ,,the ,,mechanical   
,,powers4    #de4 ,q4--,what do you     
understand by the mechanical powers8    
,a4--,the mechanical powers are certain 
contrivances1 such as the wedge1  the   
screw1 the inclined plane1 and other    
elementary machines1 which convert  a   
small force acting through a great space
 into a great force acting  through a   
small space4 ,in the school treatises on
 mechanics1 a certain  number of these  
devices are set forth as the mechanical 
powers1 and each  separate device is    
treated as if it involved a separate    
principle2 but not  a tithe of the      

contrivances which accomplish the       
stipulated end are  represented in these
 learned works1 and there is no very    
obvious necessity  for considering the  
principle of each contrivance separately
 when the  principles of all are one and
 the same4 ,every pressure acting with a
  certain velocity1 or through a certain
 space1 is convertible into a greater   
pressure acting with a less velocity1 or
 through a smaller space2 but the       
quantity of mechanical force remains    
unchanged by its transformation1 and    
all that the implements called          
mechanical powers accomplish is to      
effect  this transformation4    #df4    
,q4--,is there no power gained by the   
lever8    ,a4--,not any3 the power is   
merely put into another shape1 just as  
the  contents of a hogshead of porter   
are the same1 whether they be let off by
  an inch tap or by a hole a foot in    
diameter4 ,there is a greater gush in   
the  one case than the other1 but it    
will last a shorter time2 when a lever  

is  used there is a greater force       
exerted1 but it acts through a shorter  
distance4 ,it requires just the same    
expenditure of mechanical power to lift 
#a lb4 through #ajj ft41 as to lift #ajj
 lbs4 through #a foot4 ,a cylinder of a 
given cubical capacity will exert the   
same power by each stroke1 whether  the 
cylinder be made tall and narrow1 or    
short and wide2 but in the one  case it 
will raise a small weight through a     
great height1 and in the other  case1 a 
great weight through a small height4    
#dg4 ,q4--,is there no loss of power by 
the use of the crank8    ,a4--,not any4 
,many persons have supposed that there  
was a loss of power by  the use of the  
crank1 because at the top and bottom    
centres it is capable  of exerting      
little or no power2 but at those times  
there is little or no  steam consumed1  
so that no waste of power is occasioned 
by the peculiarity4  ,those who imagine 
that there is a loss of power caused by 
the crank perplex  themselves by        

confounding the vertical with the       
circumferential velocity4  ,if the      
circle of the crank be divided by any   
number of equidistant  horizontal lines1
 it will be obvious that there must be  
the same steam  consumed1 and the same  
power expended1 when the crank pin      
passes from the  level of one line to   
the level of the other1 in whatever part
 of the circle  it may be1 those lines  
being indicative of equal ascents or    
descents of the  piston4 ,but it will be
 seen that the circumferential velocity 
is greater  with the same expenditure of
 steam when the crank pin approaches the
 top  and bottom centres2 and this      
increased velocity exactly compensates  
for the  diminished leverage1 so that   
there is the same power given out by the
 crank  in each of the divisions4       
#dh4 ,q4--,have no plans been projected 
for gaining power by means of a  lever8 
,a4--,yes1 many plans1--some of them    
displaying much ingenuity1 but all      
displaying a complete ignorance of the  

first principles of mechanics1 which    
teach that power cannot be gained by any
 multiplication of levers and  wheels4  
,i have occasionally heard persons say3 
,you gain a great deal of  power by the 
use of a capstan2 why not apply the same
 resource in the case  of a steam       
vessel1 and increase the power of your  
engine by placing a  capstan motion     
between the engine and paddle wheels8   
,others ,i have heard  say3 ,by the     
hydraulic press you can obtain unlimited
 power2 why not then  interpose a       
hydraulic press between the engines and 
the paddles8 ,to these  questions the   
reply is sufficiently obvious4 ,whatever
 you gain in force you  lose in         
velocity2 and it would benefit you      
little to make the paddles  revolve with
 ten times the force1 if you at the same
 time caused them to  make only a tenth 
of the number of revolutions4 ,you      
cannot1 by any  combination of          
mechanism1 get increased force and      
increased speed at the  same time1 or   

increased force without diminished      
speed2 and it is from the  ignorance of 
this inexorable condition1 that such    
myriads of schemes for  the realization 
of perpetual motion1 by combinations of 
levers1 weights1  wheels1 quicksilver1  
cranks1 and other mere pieces of inert  
matter1 have  been propounded4    #di4  
,q4--,then a force once called into     
existence cannot be destroyed8          
,a4--,no2 force is eternal1 if by force 
you mean power1 or in other words       
pressure acting though space4 ,but if by
 force you mean mere pressure1 then  it 
furnishes no measure of power4 ,power is
 not measurable by force but by  force  
and velocity combined4    #ej4 ,q4--,is 
not power lost when two moving bodies   
strike one other and  come to a state of
 rest8    ,a4--,no1 not even then4 ,the 
bodies if elastic will rebound from one 
another with their original velocity2 if
 not elastic they will sustain an       
alteration of form1 and heat or         
electricity will be generated of        

equivalent  value to the power which has
 disappeared4    #ea4 ,q4--,then if     
mechanical power cannot be lost1 and is 
being daily  called into existence1 must
 not there be a daily increase in the   
power  existing in the world8           
,a4--,that appears probable unless it   
flows back in the shape of heat or      
electricity to the celestial spaces4    
,the source of mechanical power is the  
sun which exhales vapors that descend in
 rain1 to turn mills1 or which  causes  
winds to blow by the unequal rarefaction
 of the atmosphere4 ,it is  from the sun
 too that the power comes which is      
liberated in a steam engine4  ,the solar
 rays enable plants to decompose        
carbonic acid gas1 the product of       
combustion1 and the vegetation thus     
rendered possible is the source of coal 
and other combustible bodies4 ,the      
combustion of coal under a steam boiler 
therefore merely liberates the power    
which the sun gave out thousands of     
years before4        ,,friction4    #eb4

 ,q4--,what is friction8                
,a4--,friction is the resistance        
experienced when one body is rubbed upon
  another body1 and is supposed to be   
the result of the natural attraction    
which bodies have for one another1 and  
of the interlocking of the  impalpable  
asperities upon the surfaces of all     
bodies1 however smooth4  ,there is1 no  
doubt1 some electrical action involved  
in its production1 not  yet recognized1 
nor understood2 and it is perhaps       
traceable to the  disturbance of the    
electrical equilibrium of the particles 
of the body  owing to the condensation  
or change of figure which all bodies    
must  experience when subjected to a    
strain4 ,when motion in opposite        
directions  is given to smooth surfaces1
 the minute asperities of one surface   
must  mount upon those of the other1 and
 both will be abraded and worn away1 in 
which act power must be expended4 ,the  
friction of smooth rubbing substances   
is less when the composition of those   

substances is different1 than when it   
is the same1 the particles being        
supposed to interlock less when the     
opposite prominences or asperities are  
not coincident4    #ec4 ,q4--,does      
friction increase with the extent of    
rubbing surface8    ,a4--,no2 the       
friction1 so long as there is no violent
 heating or abrasion1  is simply in the 
proportion of the pressure keeping the  
surfaces together1  or nearly so4 ,it   
is1 therefore1 an obvious advantage to  
have the bearing  surfaces of steam     
engines as large as possible1 as there  
is no increase of  friction by extending
 the surface1 while there is a great    
increase in the  durability4 ,when the  
bearings of an engine are made too      
small1 they very  soon wear out4    #ed4
 ,q4--,does friction increase in the    
same ratio as velocity8    ,a4--,no2    
friction does not increase with the     
velocity at all1 if the  friction over a
 given amount of surface be considered2 
but it increases as  the velocity1 if   

the comparison be made with the time    
during which the  friction acts4 ,thus  
the friction of each stroke of a piston 
is the same1  whether it makes #bj      
strokes in the minute1 or #dj3 in the   
latter case1  however1 there are twice  
the number of strokes made1 so that1    
though the  friction per stroke is the  
same1 the friction per minute is        
doubled4 ,the  friction1 therefore1 of  
any machine per hour varies as the      
velocity1 though  the friction per      
revolution remains1 at all ordinary     
velocities1 the same4  ,of excessive    
velocities we have not sufficient       
experience to enable us to  state with  
confidence whether the same law         
continues to operate among them4    #ee4
 ,q4--,can you give any approximate     
statement of the force expended in      
overcoming friction8    ,a4--,it varies 
with the nature of the rubbing bodies4  
,the friction of iron  sliding upon     
iron1 has generally been taken at about 
one tenth of the  pressure1 when the    

surfaces are oiled and then wiped again1
 so that no film  of oil is interposed4 
,the friction of iron rubbing upon brass
 has generally  been taken at about one 
eleventh of the pressure under the same 
circumstances2 but in machines in actual
 operation1 where a film of some        
lubricating material is interposed      
between the rubbing surfaces1 it is not 
more than one third of this amount or   
#a_/cc;d of the weight4 ,while this1    
however1 is the average result1 the     
friction is a good deal less in some    
cases4 ,mr4 ,southern1 in some          
experiments upon the friction of the    
axle of a  grindstone--an account of    
which may be found in the #feth volume  
of the  ,philosophical                  
,transactions--found the friction to    
amount to less than  #a_/djth of the    
weight2 and ,mr4 ,wood1 in some         
experiments upon the friction  of       
locomotive axles1 found that by ample   
lubrication the friction may be  made as
 little as #a_/fjth of the weight4 ,in  

some experiments upon the  friction of  
shafts by ,mr4 ,g4 ,rennie1 he found    
that with a pressure of from  #a to #e  
cwt4 the friction did not exceed        
#a_/cith of the pressure when tallow    
was the unguent employed2 with soft soap
 it became #a_/cdth4 ,the fact appears  
to be that the amount of the resistance 
denominated friction depends1 in a      
great measure1 upon the nature of the   
unguent employed1 and in certain  cases 
the viscidity of the unguent may        
occasion a greater retardation than  the
 resistance caused by the attrition4 ,in
 watchwork therefore1 and other  fine   
mechanism1 it is necessary both to keep 
the bearing surfaces small1  and to     
employ a thin and limpid oil for the    
purpose of lubrication1 for the         
resistance caused by the viscidity of   
the unguent increases with the amount   
of surface1 and the amount of surface is
 relatively greater in the smaller      
class of works4    #ef4 ,q4--,is a very 
thin unguent preferable also for the    

larger class of  bearings8    ,a4--,the 
nature of the unguent1 proper for       
different bearings1 appears to  depend  
in a great measure upon the amount of   
the pressure to which the  bearings are 
subjected1--the hardest unguents being  
best where the pressure  is greatest4   
,the function of lubricating substances 
is to prevent the  rubbing surfaces from
 coming into contact1 whereby abrasion  
would be  produced1 and unguents are    
effectual in this respect in the        
proportion of  their viscidity2 but if  
the viscidity of the unguent be greater 
than what  suffices to keep the surfaces
 asunder1 an additional resistance will 
be  occasioned2 and the nature of the   
unguent selected should always have     
reference1 therefore1 to the size of the
 rubbing surfaces1 or to the  pressure  
per square inch upon them4 ,with oil the
 friction appears to be a  minimum when 
the pressure on the surface of a bearing
 is about #ij lbs4 per  square inch4    
,the friction from too small a surface  

increases twice as  rapidly as the      
friction from too large a surface1 added
 to which1 the  bearing1 when the       
surface is too small1 wears rapidly     
away4    #eg4 ,q4--,has not ,m4 ,morin1 
in ,france1 made some very complete     
experiments  to determine the friction  
of surfaces of different kinds sliding  
upon one  another8    ,a4--,he has2 but 
the result does not differ materially   
from what is stated  above1 though1 upon
 the whole1 ,m4 ,morin1 found the       
resistance due to  friction to be       
somewhat greater than it has been found 
to be by various  other engineers4 ,when
 the surfaces were merely wiped with a  
greasy cloth1  but had no film of       
lubricating material interposed1 the    
friction of brass  upon cast iron he    
found to be 4#ajg1 or about #a_/ajth of 
the load1 which was  also the friction  
of cast iron upon oak4 ,but when a film 
of lubricating  material was interposed1
 he found that the friction was the same
 whether  the surfaces were wood on     

metal1 wood on wood1 metal on wood1 or  
metal on  metal2 and the amount of the  
friction in such case depended chiefly  
on the  nature of the unguent4 ,with a  
mixture of hog's lard and olive oil     
interposed between the surfaces1 the    
friction was usually from #a_/abth to   
#a_/adth of the load1 but in some cases 
it was only #a_/bjth of the load4       
#eh4 ,q4--,may water be made to serve   
for purposes of lubrication8            
,a4--,yes1 water will answer very well  
if the surface be very large  relatively
 with the pressure2 and in screw vessels
 where the propeller  shaft passes      
through a long pipe at the stern1 the   
stuffing box is  purposely made a little
 leaky4 ,the small leakage of water into
 the vessel  which is thus occasioned1  
keeps the screw shaft in this situation 
always  wet1 and this is all the        
lubrication which this bearing requires 
or  obtains4    #ei4 ,q4--,what is the  
utmost pressure which may be employed   
without heating  when oil is the        

lubricating material8    ,a4--,that will
 depend upon the velocity4 ,when the    
pressure exceeds #hjj  lbs4 per square  
inch1 however1 upon the section of the  
bearing in a  direction parallel with   
the axis1 then the oil will be forced   
out and the  bearing will necessarily   
heat4    #fj4 ,q4--,but1 with1 a given  
velocity1 can you tell the limit of     
pressure  which will be safe in         
practice2 or with a given pressure1 can 
you tell the  limit of velocity8        
,a4--,yes2 that may be done by the      
following empirical rule1 which has been
  derived from observations made upon   
bearings of different sizes and moving  
with different velocities4 ,divide the  
number #gj1jjj by the velocity of the   
surface of the bearing in feet per      
minute4 ,the quotient will be the number
  of pounds per square inch of section  
in the line of the axis that may be  put
 upon the bearing4 ,or1 if we divide    
#gj1jjj by the number of pounds per     
square inch of section1 then the        

quotient will be the velocity in feet   
per  minute at which the circumference  
of the bearing may work4    #fa4        
,q4--,the number of square inches upon  
which the pressure is reckoned1  is not 
the circumference of the bearing        
multiplied by its length1 but the       
diameter of the bearing multiplied by   
its length8    ,a4--,precisely so1 it   
will be the diameter multiplied by the  
length of the  bearing4    #fb4         
,q4--,what is the amount of friction in 
the case of surfaces sliding  upon one  
another in sandy or muddy water--such   
surfaces1 for example1 as  are to be    
found in the sluices of valves for      
water8    ,a4--,various experiments have
 been made by ,mr4 ,summers of          
,southampton to  ascertain the friction 
of brass surfaces sliding upon each     
other in salt  water1 with the view of  
finding the power required for moving   
sluice doors  for lock gates and for    
other similar purposes4 ,the surfaces   
were planed as  true and smooth as the  

planing machine would make them1 but    
were not  filed or scraped1 and the     
result was as follows3    ,area of      
,slide    ,weight or ,pressure on       
,power required to move the  rubbing    
rubbing ,surface4           ,slide      
slowly in muddy  ,surface4              
,salt ,water1 kept stirred up4    ,sq4  
in4                 ,lb4                
,lb4  #h                       #ef      
#ba4e                        #aab       
#dd4                        #afh        
#fe4e                        #bbd       
#hh4e                        #ccf       
#adj4e                        #ddh      
#agj4ge    ,illustration3 ,fig4 #b4     
,sketch of ,slide4 ,the facing on which 
the slide moved  was similar1 but three 
or four times as long4    ,these results
 were the average of eight fair trials2 
in each case1 the  sliding surfaces were
 totally immersed in muddy salt water1  
and although  the apparatus used for    
drawing the slide along was not very    
delicately  fitted up1 the power        

required may be considered as a         
sufficient  approximation for practical 
purposes4    ,it appears from these     
experiments1 that rough surfaces follow 
the same law  as regards friction that  
is followed by smooth1 for in each case 
the  friction increases directly as the 
pressure4        ,,strength ,,of        
,,materials ,,and ,,strains ,,subsisting
 ,,in ,,machines4    #fc4 ,q4--,in what 
way are the strengths of the different  
parts of a steam  engine determined8    
,a4--,by reference to the amount of the 
strain or pressure to which they  are   
subjected1 and to the cohesive strength 
of the iron or other material  of which 
they are composed4 ,the strains         
subsisting in engines are usually       
characterized as tensile1 crushing1     
twisting1 breaking1 and shearing        
strains2 but they may be all resolved   
into strains of extension and strains   
of compression2 and by the power of the 
materials to resist these two  strains1 
will their practical strength be        

measurable4    #fd4 ,q4--,what are the  
ultimate strengths of the malleable and 
cast iron1  brass1 and other materials  
employed in the construction of engines8
    ,a4--,the tensile and crushing      
strengths of any given material are by  
no  means the same4 ,the tensile        
strength1 or strength when extended1 of 
good  bar iron is about #fj1jjj lbs41 or
 nearly #bg tons per square inch of     
section2 and the tensile strength of    
cast iron is about #ae1jjj lbs41 or say 
#f #c_/d to #g tons per square inch of  
section4 ,these are the weights which   
are  required to break them4 ,the       
crushing strain of cast iron1 however1  
is about  #ajj1jjj lbs41 or #dd #a_/b   
tons2 whereas the crushing strength of  
malleable  iron is not more than #bg1jjj
 lbs41 or #ab tons1 per square inch of  
section1  and indeed it is generally    
less than this4 ,the ultimate tensile   
strength1  therefore1 of malleable iron 
is four times greater than that of cast 
iron1  but the crushing strength of cast

 iron is between three and four times   
greater than that of wrought iron4 ,it  
may be stated1 in round numbers1 that   
the tensile strength of malleable iron  
is twice greater than its crushing      
strength2 or1 in other words1 that it   
will take twice the strain to break a   
bar of malleable iron by drawing it     
asunder endways1 than will cripple it   
by forcing it together endways like a   
pillar2 whereas a bar of cast iron  will
 be drawn asunder with one sixth of the 
force that will be required to  break or
 cripple it when forced together endways
 like a pillar4    #fe4 ,q4--,what is   
the cohesive strength of steel8         
,a4--,the ultimate tensile strength of  
good cast or blistered steel is  about  
twice as great as that of wrought iron1 
being about #acj1jjj lbs4 per  square   
inch of section4 ,the tensile strength  
of gun metal1 such as is used  in       
engines1 is about #cf1jjj lbs4 per      
square inch of section2 of wrought      
copper about #cc1jjj lbs42 and of cast  

copper about #ai1jjj lbs4 per square    
,inch of section4    #ff4 ,q4--,is the  
crushing strength of steel greater or   
less than its  tensile strength8        
,a4--,it is about twice greater4 ,a good
 steel punch will punch through a  plate
 of wrought iron of a thickness equal to
 the diameter of the punch4 ,a  punch   
therefore of an inch diameter will      
pierce a plate an inch thick4 ,now  it  
is well known1 that the strain required 
to punch a piece of metal out of  a     
plate1 is just the same as that required
 to tear asunder a bar of iron of  the  
same area of cross section as the area  
of the surface cut4 ,the area of  the   
surface cut in this case will be the    
circumference of the punch1 #c4adaf     
inches1 multiplied by the thickness of  
the plate1 #a inch1 which makes the     
area of the cut surface #c4adaf square  
inches4 ,the area of the point of the   
punch subjected to the pressure is      
4#ghed square inches1 so that the area  
cut to the area crushed is as four to   

one4 ,in other words1 it will require   
four times the strain to crush steel    
that is required to tear asunder        
malleable iron1 or it will take about   
twice the strain to crush steel that  it
 will require to break it by extension4 
#fg4 ,q4--,what strain may be applied to
 malleable iron in practice8    ,a4--,a 
bar of wrought iron to which a tensile  
or compressing strain is  applied1 is   
elongated or contracted like a very     
stiff spiral spring1 nearly  in the     
proportion of the amount of strain      
applied up to the limit at which  the   
strength begins to give way1 and within 
this limit it will recover its  original
 dimensions when the strain is removed4 
,if1 however1 the strain be  carried    
beyond this limit1 the bar will not     
recover its original  dimensions1 but   
will be permanently pulled out or pushed
 in1 just as would  happen to a spring  
to which an undue strain had been       
applied4 ,this limit is  what is called 
the limit of elasticity2 and whenever it

 is exceeded1 the  bar1 though it may   
not break immediately1 will undergo a   
progressive  deterioration1 and will    
break in the course of time4 ,the limit 
of  elasticity of malleable iron when   
extended1 or1 in other words1 the       
tensile  strain to which a bar of       
malleable iron an inch square may be    
subjected  without permanently deranging
 its structure1 is usually taken at     
#ag1hjj  lbs41 or from that to #aj tons1
 depending on the quality of the iron4  
,it has  also been found that malleable 
iron is extended about one              
ten-thousandth  part of its length for  
every ton of direct strain applied to   
it4    #fh4 ,q4--,what is the limit of  
elasticity of cast iron8    ,a4--,it is 
commonly taken at #ae1cjj lbs4 per      
square inch of section2 but  this is    
certainly much too high1 as it exceeds  
the tensile strength of  irons of medium
 quality4 ,a bar of cast iron if        
compressed by weights will  be          
contracted in length twice as much as a 

bar of malleable iron under  similar    
circumstances2 but malleable iron1 when 
subjected to a greater  strain than #ab 
tons per square inch of section1        
gradually crumples up by  the mere      
continuance of the weight4 ,a cast-iron 
bar one inch square and ten  feet long1 
is shortened about one tenth of an inch 
by a compressing force  of #aj1jjj lbs41
 whereas a malleable iron bar of the    
same dimensions would  require to       
shorten it equally a compressing force  
of #bj1jjj lbs4 ,as the  load1 however1 
approaches #ab tons1 the compressions   
become nearly equal1  and above that    
point the rate of the compression of the
 malleable iron  rapidly increases4 ,a  
bar of cast iron1 when at its breaking  
point by the  application of a tensile  
strain1 is stretched about one          
six-hundredth part  of its length2 and  
an equal strain employed to compress it1
 would shorten  it about one            
eight-hundredth part of its length4     
#fi4 ,q4--,but to what strain may the   

iron used in the construction of        
engines be safely subjected8            
,a4--,the most of the working parts of  
modern engines are made of malleable    
iron1 and the utmost strain to which    
wrought iron should be subjected in     
machinery is #djjj lbs4 per square inch 
of section4 ,cast iron should not be    
subjected to more than half of this4 ,in
 locomotive boilers the strain of  #djjj
 lbs4 per square inch of section is     
sometimes exceeded by nearly one  half2 
but such an excess of strain approaches 
the limits of danger4    #gj4 ,q4--,will
 you explain in what way the various    
strains subsisting in a  steam engine   
may be resolved into tensile and        
crushing strains2 also in  what way the 
magnitude of those strains may be       
determined8    ,a4--,to take the case of
 a beam subjected to a transverse       
strain1 such as  the great beam of an   
engine1 it is clear1 if we suppose the  
beam broken  through the middle1 that   
the amount of strain at the upper and   

lower edges  of the beam1 where the     
whole strain may be supposed to be      
collected1 will1  with any given        
pressure on the piston1 depend upon the 
proportion of the  length to the depth  
of the beam4 ,one edge of the beam      
breaks by extension1  and the other edge
 by compression2 and the upper and lower
 edges may be  regarded as pillars1 one 
of which is extended by the strain1 and 
the other  is compressed4 ,if1 to make  
an extreme supposition1 the depth of the
 beam is  taken as equal to its length1 
then the pillars answering to the edges 
of  the beam will be compressed1 and    
extended by what is virtually a         
bellcrank  lever with equal arms2 the   
horizontal distance from the main centre
 to the  end of the beam being one of   
the arms1 and the vertical height from  
the  main centre to the top edge of the 
beam being the other arm4 ,the distance1
  therefore1 passed through by the      
fractured edge of the beam during a     
stroke  of the engine1 will be equal to 

the length of the stroke2 and the strain
 it  will have to sustain will          
consequently be equal to the pressure on
 the  piston4 ,if its motion were only  
half that of the piston1 as would be the
  case if its depth were made one half  
less1 the strain the beam would have  to
 bear would be twice as great2 and it   
may be set down as an axiom1 that  the  
strain upon any part of a steam engine  
or other machine is inversely  equal to 
the strain produced by the prime mover1 
multiplied by the  comparative velocity 
with which the part in question moves4  
,if any part of  an engine moves with a 
less velocity than the piston1 it will  
have a  greater strain on it1 if        
resisted1 than is thrown upon the       
piston4 ,if it  moves with a greater    
velocity than the piston1 it will have a
 less strain  upon it1 and the          
difference of strain will in every case 
be in the inverse  proportion of the    
difference of the velocity4    #ga4     
,q4--,then1 in computing the amount of  

metal necessary to give due  strength to
 a beam1 the first point is to determine
 the velocity with which  the edge of   
the beam moves at that point were the   
strain is greatest8    ,a4--,the web of 
a cast-iron beam or girder serves merely
 to connect the  upper and lower edges  
or flanges rigidly together1 so as to   
enable the  extending and compressing   
strains to be counteracted in an        
effectual manner  by the metal of those 
flanges4 ,it is only necessary1         
therefore1 to make the  flanges of      
sufficient strength to resist           
effectually the crushing and  tensile   
strains to which they are exposed1 and  
to make the web of the beam  of         
sufficient strength to prevent a        
distortion of its shape from taking     
place4    #gb4 ,q4--,is the strain      
greater from being movable or           
intermittent than if  it was stationary8
    ,a4--,yes it is nearly twice as     
great from being movable4 ,engineers are
 in  the habit of making girders        

intended to sustain a stationary load1  
about  three times stronger than the    
breaking weight2 but if the load be a   
movable  one1 as is the case in the     
girders of railway bridges1 they make   
the  strength equal to six times the    
breaking weight4    #gc4 ,q4--,then the 
strain is increased by the suddenness   
with which it is  applied8    ,a4--,if a
 weight be placed on a long and slender 
beam propped up in the  middle1 and the 
prop be suddenly withdrawn1 so as to    
allow deflection to  take place1 it is  
clear that the deflection must be       
greater than if the  load had been      
gradually applied4 ,the momentum of the 
weight and also of the  beam itself     
falling through the space through which 
it has been deflected1  has necessarily 
to be counteracted by the elasticity of 
the beam2 and the  beam will1 therefore1
 be momentarily bent to a greater extent
 than what is  due to the load1 and     
after a few vibrations up and down it   
will finally  settle at that point of   

deflection which the load properly      
occasions4 ,it is  obvious that a beam  
must be strong enough1 not merely to    
sustain the  pressure due to the load1  
but also that accession of pressure due 
to the  counteracted momentum of the    
weight and of the beam itself4 ,although
 in  steam engines the beam is not      
loaded by a weight1 but by the pressure 
of  the steam1 yet the momentum of the  
beam itself must in every case be       
counteracted1 and the momentum will be  
considerable in every case in which  a  
large and rapid deflection takes place4 
,a rapid deflection increases the       
amount of the deflection as well as the 
amount of the strain1 as is seen in  the
 cylinder cover of a ,cornish pumping   
engine1 into which the steam is         
suddenly admitted1 and in which the     
momentum of the particles of the metal  
put into motion increases the deflection
 to an extent such as the mere  pressure
 of the steam could not produce4    #gd4
 ,q4--,what will be the amount of       

increased strain consequent upon        
deflection8    ,a4--,the momentum of any
 moving body being proportional to the  
square of  its velocity1 it follows that
 the strain will be proportional to the 
square  of the amount of deflection     
produced in a specified time4    #ge4   
,q4--,but will not the inertia of a beam
 resist deflection1 as well as  the     
momentum increase deflection8           
,a4--,no doubt that will be so2 but     
whether in practical cases increase of  
mass without reference to strength or   
load will1 upon the whole1 increase  or 
diminish deflection1 will depend very   
much upon the magnitude of the  mass    
relatively with the magnitude of the    
deflecting pressure1 and the  rapidity  
with which that pressure is applied and 
removed4 ,thus if a force  or weight be 
very suddenly applied to the middle of a
 ponderous beam1 and  be as suddenly    
withdrawn1 the inertia of the beam will1
 as in the case of  the collision of    
bodies1 tend to resist the force1 and   

thus obviate  deflection to a           
considerable extent2 but if the pressure
 be so long  continued as to produce the
 amount of deflection due to the        
pressure1 the  effect of the inertia in 
that case will be to increase the       
deflection4    #gf4 ,q4--,will the      
pressure given to the beam of an engine 
in different  directions facilitate its 
fracture8    ,a4--,iron beams bent      
alternately in opposite directions1 or  
alternately  deflected and released1    
will be broken in the course of time    
with a much  less strain than is        
necessary to produce immediate fracture4
 ,it has been  found1 experimentally1   
that a cast-iron bar1 deflected by a    
revolving cam  to only half the extent  
due to its breaking weight1 will in no  
case  withstand #ijj successive         
deflections2 but1 if bent by the cam to 
only one  third of its ultimate         
deflection1 it will withstand #ajj1jjj  
deflections  without visible injury4    
,looking1 however1 to the jolts and     

vibrations to  which engines are        
subject1 and the sudden strains         
sometimes thrown upon  them1 either from
 water getting into the cylinder or     
otherwise1 it does not  appear that a   
strength answering to six times the     
breaking weight will give  sufficient   
margin for safety in the case of        
cast-iron beams4    #gg4 ,q4--,does the 
same law hold in the case of the        
deflection of malleable  iron bars8     
,a4--,in the case of malleable iron bars
 it has been found that no very         
perceptible damage was caused by #aj1jjj
 deflections1 each deflection being     
such as was due to half the load that   
produced a large permanent  deflection4 
#gh4 ,q4--,the power of a rod or pillar 
to resist compression becomes very      
little when the diameter is small and   
the length great8    ,a4--,the power of 
a rod or pillar to resist compression1  
varies nearly as  the fourth power of   
the diameter divided by the square of   
the length4 ,in  the case of hollow     

cylindrical columns of cast iron1 it has
 been found1  experimentally1 that the  
#c4eeth power of the internal diameter1 
subtracted  from the #c4eeth power of   
the external diameter1 and divided by   
the #a4gth  power of the length1 will   
represent the strength very nearly4 ,in 
the case  of hollow cylindrical columns 
of malleable iron1 experiment shows that
 the  #c4eith power of the internal     
diameter1 subtracted from the #c4eith   
power of  the external diameter1 and    
divided by the square of the length1    
gives a  proper expression for the      
strength2 but this rule only holds where
 the  strain does not exceed #h or #i   
tons on the square inch of section4     
,beyond #ab  or #ac tons per square inch
 of section1 the metal cannot be        
depended upon to  withstand the strain1 
though hollow pillars will sometimes    
bear #ae or #af  tons per square inch of
 section4    #gi4 ,q4--,does not the    
thickness of the metal of the pillars or
 tubes  affect the question8    ,a4--,it

 manifestly does2 for a tube of very    
thin metal1 such as gold leaf  or tin   
foil1 would not stand on end at all1    
being crushed down by its own  weight4  
,it is found1 experimentally1 that in   
malleable iron tubes of the  respective 
thicknesses of 4#ebe1 4#bgb1 and 4#abd  
inches1 the resistances per  square inch
 of section are #ai4ag1 #ad4dg1 and     
#g4dg tons respectively4 ,the  power of 
plates to resist compression varies     
nearly as the cube1 or more  nearly as  
the #b4hghth power of their thickness2  
but this law only holds so  long as the 
pressure applied does not exceed from #i
 to #ab tons per square  inch of        
section4 ,when the pressure is greater  
than this the metal is  crushed1 and a  
new law supervenes1 according to which  
it is necessary to  employ plates of    
twice or three times the thickness1 to  
obtain twice the  resisting power4      
#hj4 ,q4--,in a riveted tube1 will the  
riveting be much1 damaged by heavy      
strains8    ,a4--,it will be most       

affected by percussion4 ,long-continued 
impact on the  side of a tube1 producing
 a deflection of only one fifth of that 
which  would be required to injure it by
 pressure1 is found to be destructive of
  the riveting2 but in large riveted    
structures1 such as a ship or a railway 
bridge1 the inertia of the mass will1 by
 resisting the effect of impact1        
prevent any injurious action from this  
cause from taking place4    #ha4        
,q4--,will the power of iron to resist  
shocks be in all cases  proportional to 
its power to resist strains8    ,a4--,by
 no means4 ,some cast iron is very hard 
and brittle2 and although it  will in   
this state resist compression very      
strongly1 it1 will be easily  broken by 
a blow4 ,iron which has been remelted   
many times generally falls  into this   
category1 as it will also do if run into
 very small castings4 ,it  has been     
found1 by experiment1 that iron of which
 the crushing weight per  square inch is
 about #db tons1 will1 if remelted      

twelve times1 bear a  crushing weight of
 #gj tons1 and if remelted eighteen     
times it will bear a  crushing weight of
 #hc tons2 but taking its power to      
resist impact in its  first state at    
#gjf1 this power will be raised at the  
twelfth remelting to  #aaec1 and will be
 sunk at the eighteenth remelting to    
#adi4    #hb4 ,q4--,from all this it    
appears that a combination of cast iron 
and  malleable iron is the best for the 
beams of engines8    ,a4--,yes1 and for 
all beams4 ,engine beams should be made 
deeper at the  middle than they are now 
made2 the web should be lightened by    
holes pierced  in it1 and round the edge
 of the beam there should be a malleable
 iron hoop  or strap securely attached  
to the flanges by riveting or otherwise4
 ,the  flanges at the edges of engine   
beams are invariably made too small4 ,it
 is  in them that the strength of the   
beam chiefly resides4          ,,chapter
 ,i4      ,,general ,,description ,,of  
,,the ,,steam ,,engine4           99    

99       99       99       99    ,,the  
,,boiler4    #hc4 ,q4--,what are the    
chief varieties of the steam engine in  
actual  practical use8    ,a4--,there is
 first the single-acting engine1 which  
is used for pumping  water2 the rotative
 land engine1 which is employed to drive
 mills and  manufactories2 the rotative 
marine engine1 which is used to propel  
steam  vessels2 and the locomotive      
engine1 which is employed on railways4  
,the last  is always a high-pressure    
engine2 the others are1 for the most    
part1  condensing engines4    #hd4      
,q4--,will you explain the construction 
and action of the single-acting  engine1
 used for draining mines8               
,a4--,permit me then to begin with the  
boiler1 which is common and  necessary  
to all engines2 and ,i will take the    
example of a wagon boiler1  such as was 
employed by ,boulton and ,watt          
universally in their early  engines1 and
 which is still in extensive use4 ,this 
boiler is a long  rectangular vessel1   

with a rounded top1 like that of a      
carrier's wagon1  from its resemblance  
to which it derives its name4 ,a fire is
 set beneath  it1 and flues constructed 
of brickwork encircle it1 so as to keep 
the flame  and smoke in contact with the
 boiler for a sufficient time to absorb 
the  heat4    ,illustration3 ,fig4 #c   
#he4 ,q4--,this species of boiler has   
not an internal furnace1 but is set in  
brickwork1 in which the furnace is      
formed8    ,a4--,precisely so4 ,the     
general arrangement and configuration   
will be at  once understood by a        
reference to the annexed figure 7fig4   
#c71 which is a  transverse section of a
 wagon boiler4 ,the line b represents   
the top of the  grate or fire bars1     
which slope downward from the front at  
an angle of  about #be1 giving the fuel 
a tendency to move toward the back of   
the grate4  ,the supply of air ascends  
from the ash pit through the grate bars1
 and the  flame passes over a low wall  
or bridge1 and traverses the bottom of  

the  boiler4 ,the smoke rises up at the 
back of the boiler1 and proceeds through
  the flue ,f along one side to the     
front1 and returns along the other side 
of  the boiler1 and then ascends the    
chimney4 ,the performance of this course
 by  the smoke is what is termed a wheel
 draught1 as the smoke wheels once round
  the boiler1 and then ascends the      
chimney4    #hf4 ,q4--,is the           
performance of this course by the smoke 
universal in wagon  boilers8            
,a4--,no2 such boilers sometimes have   
what is termed a split draught4 ,the    
smoke and flame1 when they reach the end
 of the boiler1 pass in this case       
through an iron flue or tube1 reaching  
from end to end of the boiler2 and  on  
arriving at the front of the boiler1 the
 smoke splits or separates--one  half   
passing through a flue on the one side  
of the boiler1 and the other  half      
passing through a flue on the other side
 of the boiler--both of these  flues    
having their debouch in the chimney4    

#hg4 ,q4--,what are the appliances      
usually connected with a wagon boiler8  
,a4--,on the top of the boiler1 near the
 front1 is a short cylinder1 with a  lid
 secured by bolts4 ,this is the manhole 
door1 the purpose of which is to  enable
 a man to get into the inside of the    
boiler when necessary for  inspection   
and repair4 ,on the top of this door is 
a small valve opening  downward1 called 
the atmospheric valve4 ,the intention of
 this valve is to  prevent a vacuum from
 being formed accidentally in the       
boiler1 which might  collapse it2 for if
 the pressure in the boiler subsides to 
a point  materially below the pressure  
of the atmosphere1 the valve will open  
and  allow air to get in4 ,a bent pipe1 
which rises up from the top of the      
boiler1 immediately behind the position 
of the manhole1 is the steam pipe  for  
conducting the steam to the engine2 and 
a bent pipe which ascends from  the top 
of the boiler1 at the back end1 is the  
waste-steam pipe for  conducting away   

the steam1 which escapes through the    
safety valve4 ,this  valve is set in a  
chest1 standing on the top of the       
boiler1 at the foot of  the waste-steam 
pipe1 and it is loaded with iron or     
leaden weights to a  point answerable to
 the intended pressure of the steam4    
#hh4 ,q4--,how is the proper level of   
the water in the boiler maintained8     
,a4--,by means of a balanced buoy or    
float4 ,this float is attached to a     
rod1 which in its turn is attached to a 
lever set on the top of a large  upright
 pipe4 ,the upper part of the pipe is   
widened out into a small  cistern1      
through a short pipe in the middle of   
which a chain passes to the  damper2 but
 any water emptied into this small      
cistern cannot pass into the  pipe1     
except through a small valve fixed to   
the lever to which the rod is  attached4
 ,the water for replenishing the boiler 
is pumped into the small  cistern on the
 top of the pipe2 and it follows from   
these arrangements that  when the buoy  

falls1 the rod opens the small valve and
 allows the feed  water to enter the    
pipe1 which communicates with the water 
in the boiler2  whereas1 when the buoy  
rises1 the feed cannot enter the pipe1  
and it has1  therefore1 to run to waste 
through an overflow pipe provided for   
the  purpose4    #hi4 ,q4--,how is the  
strength of the fire regulated8         
,a4--,the draught through the furnaces  
of land boilers is regulated by a  plate
 of metal or a damper1 as it is called1 
which slides like a sluice up  and down 
in the flue1 and this damper is closed  
more or less when the  intensity of the 
fire has to be moderated4 ,in wagon     
boilers this is  generally accomplished 
by self-acting mechanism4 ,in the small 
cistern pipe1  which is called a stand  
pipe1 the water rises up to a height    
proportional  to the pressure of the    
steam1 and the surface of the water in  
this pipe  will rise or fall with the   
fluctuations in the pressure of the     
steam4 ,in  this pipe a float is placed1

 which communicates by means of a chain 
with  the damper4 ,if the pressure of   
the steam rises1 the float will be      
raised  and the damper closed1 whereas1 
if the pressure in the boiler falls1 the
  reverse of this action will take      
place4    ,illustration3 ,fig4 #d4      
,illustration3 ,fig4 #e4      #ij4      
,q4--,are all land boilers of the same  
construction as that which you  have    
just described8    ,a4--,no2 many land  
boilers are now made of a cylindrical   
form1 with one or  two internal flues in
 which the furnace is placed4 ,a boiler 
of this kind is  represented in ,figs4  
#d and #e1 and which is the species of  
boiler  principally used in ,cornwall4  
,in this boiler a large internal        
cylinder or  flue runs from end to end4 
,in the fore part of this cylinder the  
furnace is  placed1 and behind the      
furnace a large tube filled with water  
extends to  the end of the boiler4 ,this
 internal tube is connected to the      
bottom part  of the boiler by a copper  

pipe standing vertically immediately    
behind the  furnace bridge1 and to the  
top part of the boiler by a bent copper 
pipe  which stands in a vertical        
position near the end of the boiler4    
,the smoke1  after passing through the  
central flue1 circulates round the sides
 and  beneath the bottom of the boiler  
before its final escape into the        
chimney4  ,the boiler is carefully      
covered over to prevent the dispersion  
of the heat4    ,illustration3 ,fig4 #f 
#ia4 ,q4--,will you describe the        
construction of the boilers used in     
steam  vessels8    ,a4--,these are of   
two classes1 flue boilers and tubular   
boilers1 but the  latter are now most   
used4 ,in the flue boiler the furnaces  
are set within  the boiler1 and the     
flues proceeding from them wind         
backwards and forwards  within the      
boiler until finally they meet and enter
 the chimney4 ,figs4 #f1  #g1 and #h are
 different views of the flue boilers of 
the steamer ,forth4  ,there are #d      

boilers 7as shown in plan1 ,fig4 #f71   
with #c furnaces in each1 or  #ab       
furnaces in all4 ,fig4 #g is an         
elevation of #b boilers1 the one to the 
right being the front view1 and that to 
the left a transverse section4 ,fig4  #h
 is a longitudinal section through #b   
boilers4 ,the direction of the arrows   
in plan and longitudinal section1 will  
explain the direction of the smoke      
current4    ,illustration3 ,fig4 #g4    
,illustration3 ,fig4 #h4    #ib4        
,q4--,is this arrangement different from
 that obtaining in tubular  boilers8    
,a4--,in tubular boilers1 the smoke     
after leaving the furnace just passes   
once through a number of small tubes and
 then enters the chimney4 ,these  tubes 
are sometimes of brass1 and they are    
usually about #c inches in  diameter1   
and #f or #g feet long4                 
,illustration3 ,fig4 #i4                
,illustration3 ,fig4 #aj4               
,illustration3 ,fig4 #aa4    ,figs4 #i1 
#aj1 and #aa represent a marine tubular 

boiler2 fig4 #i being a  vertical       
longitudinal section1 fig4 #aj half a   
front elevation and half a  transverse  
section1 and fig4 #aa half a back       
elevation and half a transverse  section
 near the end4 ,there is a projecting   
part on the top of the boiler  called   
the steam chest1 of which the purpose is
 to retain for the use of  the cylinder 
a certain supply of steam in a quiescent
 state1 in order that  it may have time 
to clear itself of foam or spray4 ,a    
steam chest is a usual  part of all     
marine boilers4 ,in fig4 #i ,a is the   
furnace1 ,b the steam chest1  and ,c the
 smoke box which opens into the chimney4
 ,the front of the smoke  box is usually
 closed by doors which may be opened    
when necessary to sweep  the soot out of
 the tubes4    ,the following are some  
forms of ,american boilers3    ,figs4   
#ab and #ac are the transverse and      
longitudinal sections of a common  form 
of ,american marine boiler4    ,figs4   
#ad and #ae are the front and sectional 

elevation of one of the boilers  of the 
,u4,s4 steamer ,water ,witch4           
,illustration3 ,fig4 #ab4               
,illustration3 ,fig4 #ac4               
,illustration3 ,fig4 #ad4               
,illustration3 ,fig4 #ae4    ,fig4 #af  
is a longitudinal section of a boiler of
 the drop flue variety4 ,for  land      
purposes the lowest range of tubes is   
generally omitted1 and the smoke  makes 
a last return beneath the bottom of the 
boiler4    ,figs4 #ag and #ah are the   
transverse and longitudinal sections of 
a tubular  boiler1 built in #ahcg by    
,r4,l4 ,stevens for the steamboat       
,independence4    ,illustration3 ,fig4  
#af4    ,illustration3 ,fig4 #ag4       
,illustration3 ,fig4 #ah4    ,fig4 #ai  
is a longitudinal section of a common   
wood-burning locomotive4                
,illustration3 ,fig4 #ai4          ,,the
 ,,engine4    #ic4 ,q4--,the steam      
passes from the boiler through1 the     
steam pipe into the  cylinder of the    
engine8    ,a4--,and presses up and down

 the piston alternately1 being admitted 
alternately above and below the piston  
by suitable valves provided for that    
purpose4    #id4 ,q4--,this             
reciprocating motion is all that is     
required in a pumping  engine8          
,a4--,the prevailing form of the pumping
 engine consists of a great beam        
vibrating on a centre like the beam of a
 pair of scales1 and the cylinder  is in
 connection with one end of the beam and
 the pump stands at the other  end4 ,the
 pump end of the beam is usually loaded1
 so as to cause it to  preponderate when
 the engine is at rest2 and the whole   
effort of the steam  is employed in     
overcoming this preponderance until a   
stroke is performed1  when1 the steam   
being shut off1 the heavy end of the    
beam again falls and  the operation is  
repeated4    #ie4 ,q4--in the           
double-acting engine the piston is      
pushed by the steam  both ways1 whereas 
in the single-acting engine it is only  
pushed one way8    ,a4--,the structure  

and action of a double-acting land      
engine of the kind  introduced by ,mr4  
,watt1 will be understood by a reference
 to the annexed  figure 7fig4 #bj71     
where an engine of this kind is shown in
 section4 ,a is  the cylinder in which a
 movable piston1 ,t1 is forced          
alternately up and  down by the         
alternate admission1 to each side1 of   
the steam from the  boiler4 ,the piston1
 by means of a rod called the piston    
rod1 gives motion  to the beam ,v ,w1   
which by means of a heavy bar1 ,p1      
called the connecting  rod1 moves the   
crank1 ,q1 and with it the fly wheel1   
,x1 from which the  machinery to be     
driven derives its motion4    #if4      
,q4--,where does the steam enter from   
the boiler8    ,illustration3 ,fig4 #bj4
    ,a4--,at the steam pipe1 ,b4 ,the   
throttle valve in that pipe is an       
elliptical plate of metal swivelling on 
a spindle passing through its edge  from
 side to side1 and by turning which more
 or less the opening through  the pipe  

will be more or less closed4 ,the extent
 to which this valve is  opened or      
closed is determined by the governor1   
,d1 the balls of which1 as  they        
collapse or expand1 move up or down a   
collar on the governor spindle1  which  
motion is communicated to the throttle  
valve by suitable rods and  bell-cranks4
 ,the governor1 it will be seen1        
consists substantially of two  heavy    
balls attached to arms fixed upon an    
upright shaft1 which is kept in         
revolution by means of a cord driven by 
a pulley on the fly wheel shaft4  ,the  
velocity with which the balls of the    
governor revolve being  proportional to 
that of the fly wheel1 it will follow1  
that if by reason of  too rapid a supply
 of steam1 an undue speed be given to   
the fly wheel1 and  therefore to the    
balls1 a divergence of the balls will   
take place to an  extent corresponding  
to the excess of velocity1 and this     
movement being  communicated to the     
throttle valve it will be partly closed 

7see fig4 #a71  the supply of steam to  
the engine will be diminished1 and the  
velocity of  its motion will be reduced4
 ,if1 on the other hand1 the motion of  
the engine  is slower than is requisite1
 owing to a deficient supply of steam   
through  ,b1 then the balls1 not being  
sufficiently affected by centrifugal    
force1  will fall towards the vertical  
spindle1 and the throttle valve1 ,c1    
will be  more fully opened1 whereby a   
more ample supply of steam will be      
admitted to  the cylinder1 and the speed
 of the engine will be increased to the 
requisite extent4    #ig4 ,q4--,the     
piston must be made to fit the cylinder 
accurately so as to  prevent the passage
 of steam8    ,a4--,the piston is       
accurately fitted to the cylinder1 and  
made to move in  it steam tight by a    
packing of hemp driven tightly into a   
groove or recess  round the edge of the 
piston1 and which is squeezed down by an
 iron ring  held by screws4 ,the piston 
divides the cylinder into two           

compartments1  between which there is no
 communication by which steam or any    
other elastic  fluid can pass4 ,a casing
 set beside the cylinder contains the   
valves1 by  means of which the steam    
which impels the piston is admitted and 
withdrawn1  as the piston commences its 
motion in each direction4 ,the upper    
steam box  ,b1 is divided into three    
compartments by two valves4 ,above the  
upper steam  valve ,v1 is a compartment 
communicating with the steam pipe ,b4   
,below the  lower valve ,e is another   
compartment communicating with a pipe   
called the  eduction pipe1 which leads  
downwards from the cylinder to the      
condenser1 in  which vessel the steam is
 condensed by a jet of cold water4 ,by  
the valve ,v1  a communication may be   
opened or closed between the boiler and 
the top of  the cylinder1 so as to      
permit or prevent a supply of steam from
 the one to  pass to the other4 ,by the 
valve ,e a communication may be open or 
closed  between the top of the cylinder 

and the condenser1 so that the steam in 
the  top compartment of the cylinder may
 either be permitted to escape into the 
condenser1 or may be confined to the    
cylinder4 ,the continuation of the      
steam pipe leads to the lower steam box 
,b'1 which1 like the upper1 is  divided 
into three compartments by two valves   
,v' and ,e'1 and the action of  the     
lower valves is in all respects the same
 as that of the upper4    #ih4 ,q4--,are
 all these valves connected together so 
that they act  simultaneously8          
,a4--,the four valves ,v1 ,e1 ,v'1 ,e'  
are connected by rods to a single handle
  ,h1 which handle is moved alternately 
up and down by means of pins or         
tappets1 placed on the rod which works  
the air pump4 ,when the handle ,h is    
pressed down1 the levers in connexion   
with it open the upper exhausting  valve
 ,e1 and the lower steam valve ,v'1 and 
close the upper steam valve ,v  and the 
lower exhausting valve ,e'4 ,on the     
other hand1 when the handle ,h is       

pressed up it opens the upper steam     
valve ,v and the lower exhausting valve 
,e'1 and at the same time closes the    
upper exhausting valve ,e1 and the lower
  steam valve ,v'4    #ii4 ,q4--,where  
is the condenser situated8    ,a4--,the 
condenser ,k is immerged in a cistern of
 cold water4 ,at its side  there is a   
tube ,i1 for the admission of water to  
condense the steam1 and  which is       
governed by a cock1 by opening which to 
any required extent1 a jet  of cold     
water may be made to play in the        
condenser4 ,from the bottom of the      
condenser a short pipe leads to the air 
pump ,j1 and in this pipe there is a    
flap valve1 called the foot valve1      
opening towards the air pump4 ,the air  
pump is a pump set in the same cistern  
of cold water that holds the  condenser1
 and it is fitted with a piston or      
bucket worked by the rod ,l1  attached  
to the great beam1 and fitted with a    
valve opening upwards in the  manner of 
a common sucking pump4 ,the upper part  

of the air pump  communicates with a    
small cistern ,s1 called the hot well1  
through a valve  opening outwards and   
called the delivery valve4 ,a pump ,m1  
called the hot  water pump1 lifts hot   
water out of the hot well to feed the   
boiler1 and  another pump ,n lifts cold 
water from a well or other source of    
supply1 to  maintain the supply of water
 to the cold water cistern1 in which the
  condenser and air pump are placed4    
#ajj4 ,q4--,will you explain now the    
manner in which the engine acts8        
,a4--,the piston being supposed to be at
 the top of the cylinder1 the handle  ,h
 will be raised by the lower pin or     
tappet on the air pump rod1 and the     
valves ,v and ,e' will be opened1 and at
 the same time the other pair of  valves
 ,v' and ,e will be closed4 ,steam will 
therefore be admitted above the  piston 
and the steam or air which had          
previously filled the cylinder below    
the piston will be drawn off to the     
condenser4 ,it will there encounter the 

jet of cold water1 which is kept        
constantly playing there by keeping the 
cock ,i sufficiently open4 ,it will thus
 be immediately condensed or reduced  to
 water1 and the cylinder below the      
piston will have a vacuum in it4 ,the   
steam therefore admitted from the steam 
pipe through the open valve ,v to  the  
top of the cylinder1 not being resisted 
by pressure below1 will press  the      
piston to the bottom of the cylinder4   
,as it approaches that position1  the   
handle ,h will be struck down by the    
upper pin or tappet on the air pump     
rod1 and the valves ,v and ,e'1         
previously open1 will be closed1 while  
the  valves ,v' and ,e1 previously      
closed1 will be opened4 ,the steam which
 has  just pressed down the piston1 and 
which now fills the cylinder above the  
piston1 will then flow off1 through the 
open valve ,e1 to the condenser1  where 
it will be immediately condensed by the 
jet of cold water2 and steam  from the  
boiler1 admitted through the open valve 

,v'1 will fill the cylinder  below the  
piston1 and press the piston upwards4   
,when the piston has reached  the top of
 the cylinder1 the lower pin on the air 
pump rod will have struck  the handle   
upwards1 and will thereby have closed   
the valves ,v' and ,e1 and  opened the  
valves ,v and ,e'4 ,the piston will then
 be in the same situation  as in the    
commencement1 and will again descend1   
and so will continue to be  driven up   
and down by the steam4    #aja4         
,q4--,but what becomes of the cold water
 which is let into the condenser  to    
condense the steam8    ,a4--,it is      
pumped out by the air pump in the shape 
of hot water1 its  temperature having   
been raised considerably by the         
admixture of the steam  in it4 ,when the
 air pump piston ascends it leaves      
behind it a vacuum2 and  the foot valve 
being relieved from all pressure1 the   
weight of the water in  the condenser   
forces it open1 and the warm water flows
 from the condenser  into the lower part

 of the air pump1 from which its return 
to the condenser  is prevented by the   
intervening valve4 ,when the air pump   
piston descends1  its pressure on the   
liquid under it will force open the     
valve in it1  through which the hot     
water will ascend2 and when the bucket  
descends to  the bottom of the pump     
barrel1 the warm water which was below  
it will all  have passed above it1 and  
cannot return4 ,when the bucket next    
ascends1 the  water above it1 not being 
able to return through the bucket valve1
 will be  forced into the hot well      
through the delivery valve ,s4 ,the hot 
water pump  ,m1 pumps a small quantity  
of this hot water into the boiler1 to   
compensate  for the abstraction of the  
water that has passed off in the form of
 steam4  ,the residue of the hot water  
runs to waste4    #ajb4 ,q4--,by what   
expedient is the piston rod enabled to  
pass through the  cylinder cover without
 leaking steam out of the cylinder or   
air into it8    ,a4--,the hole in the   

cylinder lid1 through which the piston  
rod passes1 is  furnished with a recess 
called a stuffing box1 into which a     
stuffing or  packing of plaited hemp is 
forced1 which1 pressing on the one side 
against  the interior of the stuffing   
box1 and on the other side against the  
piston  rod1 which is smooth and        
polished1 prevents any leakage in this  
situation4  ,the packing of this        
stuffing box is forced down by a ring of
 metal  tightened by screws4 ,this ring1
 which accurately fits the piston rod1  
has a  projecting flange1 through which 
bolts pass for tightening the ring down 
upon the packing2 and a similar         
expedient is employed in nearly every   
case  in which packing is employed4     
#ajc4 ,q4--,in what way is the piston   
rod connected to the great beam8        
,a4--,the piston rod is connected to the
 great beam by means of two links1  one 
at each side of the beam shown at f g1  
7fig4 #ba47 ,these links are  usually   
made of the same length as the crank1   

and their purpose is to  enable the end 
of the great beam to move in the arc of 
a circle while the  piston rod maintains
 the vertical position4 ,the point of   
junction1  therefore1 of the links and  
the piston rod is of the form of a      
knuckle or  bend at some parts of the   
stroke4    #ajd4 ,q4--,but what compels 
the top of the piston rod to maintain   
the  vertical position8    ,a4--,some   
engines have guide rods set on each side
 of the piston rod1 and  eyes on the top
 of the piston rod engage these guide   
rods1 and maintain the  piston rod in a 
vertical position in every part of the  
stroke4 ,more  commonly1 however1 the   
desired end is attained by means of a   
contrivance  called the parallel motion4
    #aje4 ,q4--,what is the parallel    
motion8    ,a4--,the parallel motion is 
an arrangement of jointed rods1 so      
connected  together that the divergence 
from the vertical line at any point in  
the arc  described by the beam is       
corrected by an equal and opposite      

divergence due  to the arc performed by 
the jointed rods during the stroke2 and 
as these  opposite deviations mutually  
correct one another1 the result is that 
the  piston rod moves in a vertical     
direction4    #ajf4 ,q4--,will you      
explain the action more in detail8      
,a4--,the pin1 fig #ba1 which passes    
through the end of the beam at f has  a 
link f g hung on each side of the beam1 
and a short cross bar1 called a  cross  
head1 extends from the bottom of one of 
these links to the bottom of  the other1
 which cross head is perforated with a  
hole in the middle for the  reception of
 the piston rod4 ,there are similar     
links b d at the point of  the main     
beam1 where the air pump rod is         
attached4 ,there are two rods d g       
connecting the links b d with the links 
f g1 and these rods1 as they  always    
continue parallel to the main beam      
throughout the stroke1 are called       
parallel bars4 ,attached to the end of  
these two rods at d are two other  rods 

c d1 of which the ends at c are attached
 to stationary pins1 while  the ends at 
d follow the motion of the lower ends of
 the links b d4  ,these rods are called 
the radius bars4 ,now it is obvious that
 the arc  described by the point d1 with
 c as a centre1 is opposite to the arc  
described by the point g with d as a    
centre4 ,the rod d g is1  therefore1    
drawn back horizontally by the arc      
described at d to an extent  equal to   
the versed sine of the arc described at 
g1 or1 in other words1  the line        
described by the point g becomes a      
straight line instead of a  curve4      
,illustration3 ,fig4 #ba4    #ajg4      
,q4--,does the air pump rod move        
vertically as well as the piston rod8   
,a4--,it does4 ,the air pump rod is     
suspended from a cross head1 passing    
from the centre of one of the links b d 
to the centre of the other link1  on the
 opposite side of the beam4 ,now1 as the
 distance from the central  axis of the 
great beam to the point b is equal to   

the length of the rod  c d1 it will     
follow that the upper end of the link   
will follow one arc1  and the lower end 
an equal and opposite arc4 ,a point in  
the centre of the  link1 therefore1     
where these opposite motions meet1 will 
follow no arc at  all1 but will move up 
and down vertically in a straight line4 
#ajh4 ,q4--,the use of the crank is to  
obtain a circular motion from a         
reciprocating motion8    ,a4--,that is  
the object of it1 and it accomplishes   
its object in a very  perfect manner1 as
 it gradually arrests the velocity of   
the piston towards  the end of the      
stroke1 and thus obviates what would    
otherwise be an  injurious shock upon   
the machine4 ,when the crank approaches 
the lowest part  of its throw1 and at   
the same time the piston is approaching 
the top of the  cylinder1 the motion of 
the crank becomes nearly horizontal1 or1
 in other  words1 the piston is only    
advanced through a very short distance1 
for any  given distance measured on the 

circle described by the crank pin4      
,since1  then1 the velocity of rotation 
of the crank is nearly uniform1 it will 
follow that the piston will move very   
slowly as it approaches the end of  the 
stroke2 and the piston is brought to a  
state of rest by this gradually         
retarded motion1 both at the top and the
 bottom of the stroke4    #aji4         
,q4--,what causes the crank to revolve  
at a uniform velocity8    ,a4--,the     
momentum of the machinery moved by the  
piston1 but more  especially of the fly 
wheel1 which by its operation redresses 
the unequal  pressures communicated by  
the crank1 and compels the crank shaft  
to revolve  at a nearly uniform         
velocity4 ,everyone knows that a heavy  
wheel if put into  rapid rotation cannot
 be immediately stopped4 ,at the        
beginning and end of  the stroke when   
the crank is vertical1 no force of      
torsion can be exerted  on the crank    
shaft by the crank1 but this force is at
 its maximum when the  crank is         

horizontal4 ,from the vertical point1   
where this force is nothing1  to the    
horizontal point1 where it is at its    
maximum1 the force of torsion  exerted  
on the crank shaft is constantly        
varying2 and the fly wheel by its       
momentum redresses these irregularities1
 and carries the crank through that     
dead point1 as it is termed1 where the  
piston cannot impart any rotative       
force4    #aaj4 ,q4--,are the           
configuration and structure of the steam
 engine1 as it  left the hand of ,watt1 
materially different from those of      
modern engines8    ,a4--,there is not   
much difference4 ,in modern rotative    
land engines1 the  valves for admitting 
the steam to the cylinder or condenser1 
instead of  being clack or pot-lid      
valves moved by tappets on the air pump 
rod1 are  usually sluice or sliding     
valves1 moved by an eccentric wheel on  
the crank  shaft4 ,sometimes the beam is
 discarded altogether1 and malleable    
iron is  more largely used in the       

construction of engines instead of the  
cast iron1  which formerly so largely   
prevailed4 ,but upon the whole the steam
 engine of  the present day is          
substantially the engine of ,watt2 and  
he who perfectly  understands the       
operation of ,watt's engine1 will have  
no difficulty in  understanding the     
operation of any of the numerous        
varieties of engines  since introduced4 
,,the ,,marine ,,engine4    #aaa4       
,q4--,will you describe the principal   
features of the kind of steam  engine   
employed for the propulsion of vessels8 
,a4--,marine engines are of two         
kinds1--paddle engines and screw        
engines4  ,in the one case the          
propelling instrument is paddle wheels  
kept in rotation  at each side of the   
ship3 in the other case1 the propelling 
instrument is a  screw1 consisting of   
two or more twisted vanes1 revolving    
beneath the water  at the stern4 ,of    
each class of engines there are many    
distinct varieties4    #aab4 ,q4--,what 

are the principal varieties of the      
paddle engine8    ,illustration3 ,fig4  
#bb4    ,illustration3 ,fig4 #bc4       
,a4--,there is the side lever engine    
7fig4 #bf71 and the oscillating engine  
7fig4 #bg71 besides numerous other forms
 of engine which are less known or      
employed1 such as the trunk 7fig4 #bb71 
double cylinder 7fig4 #bc71 annular1    
,gorgon 7fig4 #bd71 steeple 7fig4 #be71 
and many others4 ,the side lever        
engine1 however1 and the oscillating    
engine1 are the only kinds of paddle    
engines which have been received with   
wide or general favor4    ,illustration3
 ,fig4 #bd4    #aac4 ,q4--,will you     
explain the main distinctive features of
 the side lever  engine8    ,a4--,in all
 paddle vessels1 whatever be their      
subordinate characteristics1  a great   
shaft of wrought iron1 s1 turned round  
by the engine1 has to be  carried from  
side to side of the vessel1 on which    
shaft are fixed the  paddle wheels4 ,the
 paddle wheels may either be formed with

 fixed float  boards for engaging the   
water1 like the boards of a common      
undershot water  wheel1 or they may be  
formed with feathering float boards as  
they are  termed1 which is float boards 
movable on a centre1 and so governed by 
appropriate mechanism that they enter   
and leave the water in a nearly         
vertical position4 ,the common fixed or 
radial floats1 however1 are the kind    
most widely employed1 and they are      
attached to the arms of two or more     
rings of malleable iron which are fixed 
by appropriate centres on the  paddle   
shaft4 ,it is usual in steam vessels to 
employ two engines1 the  cranks of which
 are set at right angles with one       
another4 ,when the paddle  wheels are   
turned by the engines1 the float boards 
engaging the water cause  a forward     
thrust to be imparted to the shaft1     
which propels forward the  vessel on the
 same principle that a boat is propelled
 by the action of  oars4                
,illustration3 ,fig4 #be4    #aad4      

,q4--,these remarks apply to all paddle 
vessels8    ,a4--,they do4 ,with respect
 to the side lever engine1 it may be    
described  to be such a modification of 
the land beam engine already described1 
as  will enable it to be got below the  
deck of a vessel4 ,with this view1      
instead of a single beam being placed   
overhead1 two beams are used1 one of    
which is set on each side of the engine 
as low down as possible4 ,the cross     
head which engages the piston rod is    
made somewhat longer than the diameter  
of the cylinder1 and two great links or 
rods proceed one from each end of  the  
cross head to one of the side levers or 
beams4 ,a similar cross bar at  the     
other end of the beams serves to connect
 them together and to the  connecting   
rod which1 proceeding from thence       
upwards1 engages the crank1  and thereby
 turns round the paddle wheels4    #aae4
 ,q4--,will you further illustrate this 
general description by an  example8     
,illustration3 ,fig4 #bf4    ,q4--,fig4 

#bf is a side elevation of a side lever 
engine2 x x represent the  beams or     
keelsons to which the engines are       
attached1 and on which the  boilers     
rest4 ,the engines are tied down by     
strong bolts passing through the  bottom
 of the vessel1 but the boiler keeps its
 position by its weight  alone4 ,the    
condenser and air pump are worked off   
the side levers by means  of side rods  
and a cross head4 ,a strong gudgeon1    
called the main centre1  passes through 
the condenser at ,k1 the projecting ends
 of which serve to  support the side    
levers or beams4 ,l is the piston rod1  
which1 by means of  the cross head and  
side rods1 is connected to the side     
levers or beams1 one  of which is shown 
at ,h ,h4 ,the line ,m represents the   
connecting rod1 to  which motion is     
imparted by the beams1 through the      
medium of the cross tail  extending     
between the beams1 and which by means of
 the crank turns the  paddle shaft ,s4  
,the eccentric which works the slide    

valve is placed upon  the paddle shaft4 
,it consists of a disc of metal         
encircled by a hoop1 to  which a rod is 
attached1 and the disc is perforated    
with a hole for the  shaft1 not in the  
centre1 but near one edge4 ,when1       
therefore1 the shaft  revolves1 carrying
 the eccentric with it1 the rod attached
 to the  encircling hoop receives a     
reciprocating motion1 just as it would  
do if  attached to a crank in the shaft4
    #aaf4 ,q4--,will you describe the   
mode of starting the engine8    ,a4--,i 
may first mention that when the engine  
is at rest1 the connection  between the 
eccentric and the slide valve is broken1
 by lifting the end of  the eccentric   
rod out of a notch which engages a pin  
on the valve shaft1  and the valve is at
 such times free to be moved by hand by 
a bar of iron1  applied to a proper part
 of the valve gear for that purpose4    
,this being so1  the engineer1 when he  
wishes to start the engine1 first opens 
a small valve  called the blow through  

valve1 which permits steam from the     
boiler to  enter the engine both above  
and below the piston1 and also to fill  
the  condenser and air pump4 ,this steam
 expels the air from the interior of the
  engine1 and also any water which may  
have accumulated there2 and when this   
has been done1 the blow through valve is
 shut1 and a vacuum very soon forms     
within the engine1 by the condensation  
of the steam4 ,if now the slide valve   
be moved by hand1 the steam from the    
boiler will be admitted on one side of  
the piston1 while there is a vacuum on  
the other side1 and the piston will1    
therefore1 be moved in the desired      
direction4 ,when the piston reaches the 
end of the stroke1 the valve has to be  
moved in the reverse direction1 when    
the piston will return1 and after being 
moved thus by hand1 once or twice1  the 
connection of the valve with the        
eccentric is to be restored by  allowing
 the notch on the end of the eccentric  
rod to engage the pin on the  valve     

lever1 when the valve will be thereafter
 moved by the engine in the  proper     
manner4 ,it will1 of course1 be         
necessary1 when the engine begins to    
move1 to open the injection cock a      
little1 to enable water to enter for the
  condensation of the steam4 ,in the    
most recent marine engines1 a somewhat  
different mechanism from this is used   
for giving motion to the valves1 but    
that mechanism will be afterwards       
described4    #aag4 ,q4--,are all marine
 engines condensing engines8            
,a4--,nearly all of them are so2 but    
recently a number of gunboats have  been
 constructed1 with high pressure        
engines4 ,in general1 however1 marine   
engines are low pressure or condensing  
engines4    #aah4 ,q4--,will you now    
describe the chief features of the      
oscillating  paddle marine engine8      
,a4--,in the oscillating paddle marine  
engine1 the arrangement of the  paddle  
shaft and paddle wheels is the same as  
in the case already  described1 but the 

whole of the side levers1 side rods1    
cross head1 cross  tail1 and connecting 
rod are discarded4 ,the cylinder is set 
immediately  under the crank2 the top of
 the piston rod is connected immediately
 to the  crank pin2 and1 to enable the  
piston rod to accommodate itself to the 
movement of the crank1 the cylinder is  
so constructed as to be susceptible  of 
vibrating or oscillating upon two       
external axes or trunnions4 ,these      
trunnions are generally placed about    
half way up on the sides of the         
cylinder2 and through one of them steam 
is received from the boiler1 while      
through the other the steam escapes to  
the condenser4 ,the air pump is  usually
 worked by means of a crank in the      
shaft1 which crank moves the air  pump  
bucket up and down as the shaft         
revolves4    #aai4 ,q4--,will you give  
an example of a paddle oscillating      
engine8    ,a4--,i will take as an      
example the oscillating engines         
constructed by  ,messrs4 ,ravenhill     

,salked1 for the ,holyhead ,packets4    
,fig4 #bg is a  longitudinal section of 
this vessel1 showing an engine and      
boiler2 and fig4  #bh is a transverse   
section of one of the engines1 showing  
also one of the  wheels4 ,there are two 
cylinders in this vessel1 and one air   
pump1 which  lies in an inclined        
position1 and is worked by a crank in   
the shaft which  stretches between the  
cylinders1 and which is called the      
intermediate  shaft4 ,a ,a1 is one of   
the cylinders1 ,b ,b the piston rod1 and
 ,c ,c the  crank4 ,d is the crank in   
the intermediate shaft1 which works the 
air pump  ,e4 ,there are double         
eccentrics fixed on the shaft1 whereby  
the movement of  the slide valves is    
regulated4 ,the purpose of the double   
eccentrics is to  enable an improved    
arrangement of valve gear to be         
employed1 which is  denominated the link
 motion1 and which will be described    
hereafter4 ,i ,i  are the steam pipes   
leading to the steam trunnions ,k ,k1 on

 which1 and on  the eduction trunnions  
connected with the pipe ,m1 the         
cylinders oscillate4    #abj4 ,q4--,by  
what species of mechanism are the       
positions of the paddle  floats of      
feathering wheels governed8    ,a4--,the
 floats are supported by spurs          
projecting from the rim of the  wheel1  
and they may be moved upon the points of
 the spurs1 to which they  are attached 
by pins1 by means of short levers       
proceeding from the backs of  the       
floats1 and connected to rods which     
proceed towards the centre of the       
wheel4 ,the centre1 however1 to which   
these rods proceed is not concentric    
with the wheel1 and the rods1 therefore1
 are moved in and out as the wheel      
revolves1 and impart a corresponding    
motion to the floats4 ,in some          
feathering wheels the proper motion is  
given to the rods by means of an        
eccentric on the ship's side4 ,the      
action of paddle wheels1 whether radial 
or feathering1 will be more fully       

described in the chapter on ,steam      
,navigation4        ,,screw ,,engines4  
#aba4 ,q4--,what are the principal      
varieties of screw engines8             
,illustration3 ,fig4 #bg4               
,illustration3 ,fig4 #bh4    ,a4--,the  
engines employed for the propulsion of  
screw vessels are divided  into two     
great classes1--geared engines and      
direct acting engines2 and each  of     
these classes again has many varieties4 
,in screw vessels1 the shaft on  which  
the screw is set requires to revolve at 
a much greater velocity than  is        
required in the case of the paddle shaft
 of a paddle vessel2 and in  geared     
engines this necessary velocity of      
rotation is obtained by the             
intervention of toothed wheels1--the    
engines themselves moving with the      
usual velocity of paddle engines2       
whereas in direct acting engines the    
required velocity of rotation is        
obtained by accelerating the speed of   
the  engines1 and which are connected   

immediately to the screw shaft4    #abb4
 ,q4--,will you describe some of the    
principal varieties of geared  engines8 
,a4--,a good many of the geared engines 
for screw vessels are made in the  same 
manner as land engines1 with a beam     
overhead1 which by means of a           
connecting rod extending downwards1     
gives motion to the crank shaft1 on     
which are set the cog wheels which give 
motion to pinions on the screw          
shaft1--the teeth of the wheels being   
generally of wood and the teeth of  the 
pinions of iron4 ,there are usually     
several wheels on the crank shaft  and  
several pinions on the screw shaft2 but 
the teeth of each do not run in  the    
same line1 but are set a little in      
advance of one another1 so as to  divide
 the thickness of the tooth into as many
 parts as there are  independent wheels 
or pinions4 ,by this arrangement the    
wheels work more  smoothly than they    
would otherwise do4    #abc4 ,q4--,what 
other forms are there of geared screw   

engines8    ,a4--,in some cases the     
cylinders lie on their sides in the     
manner of the  cylinders of a locomotive
 engine4 ,in other cases vertical trunk 
engines are  employed2 and in other     
cases vertical oscillating engines4     
#abd4 ,q4--,will you give an example of 
a geared vertical oscillating  engine8  
,a4--,the engines of a geared           
oscillating engine are similar to the   
paddle  wheel engines 7figs4 #bg and    
#bh71 but the engines are placed        
lengthways of  the ship1 and instead of 
a paddle wheel on the main shaft1 there 
is a  geared wheel which connects with a
 pinion on the screw shaft4 ,the engines
  of the ,great ,britain are made off   
the same patterns as the paddle engines 
constructed by ,messrs4 ,john ,penn     
,son1 for ,h4,m4,s4 ,sphinx4 ,the       
diameter of  each cylinder is #hb-a_/b  
inches1 the length of travel or stroke  
of the  piston is #f feet1 and the      
nominal power is #ejj horses4 ,the      
,great ,britain is  of #c1ejj tons      

burden1 and her displacement at #af feet
 draught of water is  #b1igj tons4 ,the 
diameter of the screw is #ae-a_/b feet1 
length of screw in  the line of the     
shaft1 #c feet #b inches1 and the pitch 
of the screw1 #ai  feet4    #abe4       
,q4--,what do you mean by the pitch of  
the screw8    ,a4--,a screw propeller   
may be supposed to be a short piece cut 
off a screw  of large diameter like a   
spiral stair1 and the pitch of a spiral 
stair is  the vertical height from any  
given step to the step immediately      
overhead4    #abf4 ,q4--,what is the    
usual number of arms8    ,a4--,generally
 a screw has two arms1 but sometimes it 
has three or more4  ,the ,great ,britain
 had three arms or twisted blades       
resembling the vanes of  a windmill4    
,the multiple of the gearing in the     
,great ,britain is #c to #a1 and  there 
are #ag-a_/b square feet of heating     
surface in the boiler for each  nominal 
horse power4 ,the crank shaft being put 
into motion by the engine1  carries     

round with it the great cog wheel1 or   
aggregation of cog wheels1  affixed to  
its extremity2 and these wheels acting  
on suitable pinions on  the screw shaft1
 cause the screw to make three          
revolutions for every  revolution made  
by the engine4    #abg4 ,q4--,what are  
the principal varieties of direct acting
 screw engines8    ,a4--,in some cases  
four engines have been employed instead 
of two1 and the  cylinders have been    
laid on their sides on each side of the 
screw shaft4  ,this multiplication of   
engines1 however1 introduces needless   
complication1  and is now but little    
used4 ,in other cases two inverted      
cylinders are set  above the screw shaft
 on appropriate framing2 and connecting 
rods attached  to the ends of the piston
 rods turn round cranks in the screw    
shaft4    #abh4 ,q4--,what is the kind  
of direct acting screw engine employed  
by  ,messrs4 ,penn4    ,a4--,it is a    
horizontal trunk engine4 ,in this engine
 a round pipe called a  trunk penetrates

 the piston1 to which it is fixed1 being
 in fact cast in  one piece with it2 and
 the trunk also penetrates the top and  
bottom of the  cylinder1 through which  
it moves1 and is made tight therein by  
means of  stuffing boxes4 ,the          
connecting rod is attached at one end to
 a pin fixed in  the middle of the      
trunk1 while the other end engages the  
crank in the usual  manner4 ,the air    
pump is set within the condenser1 and is
 wrought by a rod  which is fixed to the
 piston and derives its motion          
therefrom4 ,the air pump  is of that    
species which is called double-acting4  
,the piston or bucket is  formed without
 valves in it1 but an inlet and outlet  
valve is fixed to each  end of the pump1
 through the one of which the water is  
drawn into the pump  barrel1 and through
 the other of which it is expelled into 
the hot well4        ,,the ,,locomotive 
,,engine4    #abi4 ,q4--,will you       
describe the more important features of 
the locomotive  engine8    ,a4--,the    

locomotive employed to draw carriages   
upon railways1 consists of  a           
cylindrical boiler filled with brass    
tubes1 through which the hot air  passes
 on its progress from the furnace to the
 chimney1 and attached to the  boiler   
are two horizontal cylinders fitted with
 pistons1 valves1 connecting  rods1 and 
other necessary apparatus to enable the 
power exerted by the  pistons to turn   
round the cranked axle to which the     
driving wheels are  attached4 ,there    
are1 therefore1 two independent engines 
entering into the  composition of a     
locomotive1 the cranks of which are set 
at right angles  with one another1 so   
that when one crank is at its dead      
point1 the other  crank is in a position
 to act with its maximum efficacy4 ,the 
driving  wheels1 which are fixed on the 
crank shaft and turn round with it1     
propel  the locomotive forward on the   
rails by the mere adhesion of friction1 
and  this is found sufficient not merely
 to move the locomotive1 but to draw a  

long train of carriages behind it4      
#acj4 ,q4--,are locomotive engines      
condensing or high pressure engines4    
,a4--,they are invariably high pressure 
engines1 and it would be impossible  or 
at least highly inconvenient1 to carry  
the water necessary for the  purpose of 
condensation4 ,the steam1 therefore1    
after it has urged the  piston to the   
end of the stroke1 escapes into the     
atmosphere4 ,in locomotive  engines the 
waste steam is always discharged into   
the chimney through a  vertical pipe1   
and by its rapid passage it greatly     
increases the intensity  of the draught 
in the chimney1 whereby a smaller fire  
grate suffices for  the combustion of   
the fuel1 and the evaporative power of  
the boiler is much  increased4    #aca4 
,q4--,can you give an example of a good 
locomotive engine of the usual  form8   
,a4--,to do this ,i will take the       
example of one of ,hawthorn's locomotive
  engines with six wheels represented in
 fig4 #bi2 not one of the most modern   

construction now in use1 nor yet one of 
the most antiquated4 ,m is the          
cylinder1 ,r the connecting rod1 ,c ,c  
the eccentrics by which the slide valve 
is moved2 ,j ,j is the steam pipe by    
which the steam is conducted from the   
steam dome of the boiler to the         
cylinder4 ,near the smoke stack end of  
this  pipe is a valve ,k or regulator   
moved by a handle p at the front of the 
boiler1 and of which the purpose is to  
regulate the admission of the steam  to 
the cylinder2 f is a safety valve kept  
closed by springs2 ,n is the  eduction  
pipe1 or1 as it is commonly termed in   
locomotives1 the blast  pipe1 by which  
the steam1 escaping from the cylinder   
after the stroke has  been performed1 is
 projected up the chimney ,h4 ,the water
 in the boiler of  course covers the    
tubes and also the top of the furnace or
 fire box4 ,it  will be understood that 
there are two engines in each           
locomotive1 though1  from the figure    
being given in section1 only one engine 

can be shown4 ,the  cylinders of this   
engine are each #ad inches diameter2 the
 length of the  stroke of the piston is 
#ba inches4 ,there are two sets of      
driving wheels1 #e  feet diameter1 with 
outside connections4    ,illustration3  
,fig4 #bi4    #acb4 ,q4--,what is the   
tender of a locomotive8    ,a4--,it is a
 carriage attached to the locomotive1 of
 which the purpose is  to contain coke  
for feeding the furnace1 and water for  
replenishing the  boiler4    #acc4      
,q4--,can you give examples of modern   
locomotives8    ,illustration3 ,fig4    
#cj4    ,illustration3 ,fig4 #ca4       
,a4--,the most recent locomotives       
resemble in their material features the 
locomotive represented in fig4 #bi4 ,i  
can1 however1 give examples of some of  
the most powerful engines of recent     
construction4 ,fig4 #cj represents      
,gooch's express engine1 adapted for the
 wide gauge of the ,great ,western      
,railway2 and fig4 #ca represents       
,crampton's express engine1 adapted for 

the  ordinary or narrow gauge railways4 
,the cylinders of ,gooch's engine are   
each  #ah inches diameter1 and #bd      
inches stroke2 the driving wheels are #h
 feet in  diameter2 the fire grate      
contains #ba square feet of area2 and   
the heating  surface of the fire box is 
#aec square feet4 ,there are in all #cje
 tubes in  the boiler1 each of #b inches
 diameter1 giving a heating surface in  
the  tubes of #agii square feet4 ,the   
total heating surface1 therefore1 is    
#aieb  square feet4 ,mr4 ,gooch states  
that an engine of this class will       
evaporate  from #cjj to #cfj cubic feet 
of water in the hour1 and will convey a 
load of  #bcf tons at a speed of #dj    
miles an hour1 or a load of #aha tons at
 a speed  of #fj miles an hour4 ,the    
weight of this engine empty is #ca tons2
 of the  tender #h-a_/b tons2 and the   
total weight of the engine when loaded  
is #ej  tons4 ,in one of ,crampton's    
locomotives1 the ,liverpool1 with one   
set more of  carrying wheels than the   

fig41 the cylinders are of #bd inches   
diameter and  #ah inches stroke2 the    
driving wheels are #h feet in diameter2 
the fire grate  contains #ba-a_/b square
 feet of area2 and the heating surface  
of the fire  box is #aed square feet4   
,there are in all #cjj tubes in the     
boiler of #b-c_/af  inches external     
diameter1 giving a surface in the tubes 
of #bacf square  feet1 and a total      
heating surface of #bbij square feet4   
,the weight of this  engine is stated to
 be #ce tons when ready to proceed on a 
journey4 ,both  engines were displayed  
at the ,great ,exhibition in #ahea1 as  
examples of the  most powerful          
locomotive engines then made4 ,the      
weight of such engines is  very         
injurious to the railway2 bending1      
crushing1 and disturbing the rails1  and
 trying very severely the whole of the  
railway works4 ,no doubt the  weight may
 be distributed upon a greater number of
 wheels1 but if the  weight resting on  
the driving wheels be much reduced1 they

 will not have  sufficient bite upon the
 rails to propel the train without      
slipping4 ,this1  however1 is only one  
of the evils which the demand for high  
rates of speed  has produced4 ,the width
 of the railway1 or1 as it is termed1   
the gauge of  the rails1 being in most  
of the railways in this kingdom limited 
to #d feet  #h-a_/b inches1 a           
corresponding limitation is imposed on  
the diameter of the  boiler2 which in   
its turn restricts the number of the    
tubes which can be  employed4 ,as1      
however1 the attainment of a high rate  
of speed requires much  power1 and      
consequently much heating surface in the
 boiler1 and as the  number of tubes    
cannot be increased without reducing    
their diameter1 it has  become          
necessary1 in the case of powerful      
engines1 to employ tubes of a  small    
diameter1 and of a great length1 to     
obtain the necessary quantity of        
heating surface2 and such tubes require 
a very strong draught in the  chimney to

 make them effective4 ,with a draught of
 the usual intensity the  whole of the  
heat will be absorbed in the portion of 
the tube nearest the  fire box1 leaving 
that portion nearest the smoke box      
nothing to do but to  transmit the      
smoke2 and with long tubes of small     
diameter1 therefore1 a  very strong     
draught is indispensable4 ,to obtain    
such a draught in  locomotives1 it is   
necessary to contract the mouth of the  
blast pipe1  whereby the waste steam    
will be projected into the chimney with 
greater  force2 but this contraction    
involves an increase of the pressure on 
the  eduction side of the piston1 and   
consequently causes a diminution in the 
power of the engine4 ,locomotives with  
small and long tubes1 therefore1 will   
require more coke to do the same work   
than locomotives in which larger and    
shorter tubes may be employed4          
,,chapter ,,ii4    ,,heat1 ,,combustion1
 ,,and ,,steam4        ,,heat4    #acd4 
,q4--,what is meant by latent heat8     

,a4--,by latent heat is meant the heat  
existing in bodies which is not         
discoverable by the touch or by the     
thermometer1 but which manifests its    
existence by producing a change of      
state4 ,heat is absorbed in the         
liquefaction of ice1 and in the         
vaporization of water1 yet the          
temperature  does not rise during either
 process1 and the heat absorbed is      
therefore  said to become latent4 ,the  
term is somewhat objectionable1 as the  
effect  proper to the absorption of heat
 has in each case been made visible2 and
 it  would be as reasonable to call hot 
water latent steam4 ,latent heat1 in the
  present acceptation of the term1 means
 sensible liquefaction or  vaporization2
 but to produce these changes heat is as
 necessary as to  produce the expansion 
of mercury in a thermometer tube1 which 
is taken as  the measure of temperature2
 and it is hard to see on what ground   
heat can  be said to be latent when its 
presence is made manifest by changes    

which  only heat can effect4 ,it is the 
temperature only that is latent1 and    
latent temperature means sensible       
vaporization or liquefaction4    #ace4  
,q4--,but when you talk of the latent   
heat of steam1 what do you mean  to     
express8    ,a4--,i mean to express the 
heat consumed in accomplishing the      
vaporization  compared with that        
necessary for producing the temperature4
 ,the latent heat  of steam is usually  
reckoned at about #ajjj degrees1 by     
which it is meant  that there is as much
 heat in any given weight of steam as   
would raise its  constituent water #ajjj
 degrees if the expansion of the water  
could be  prevented1 or as would raise  
#ajjj times that quantity of water one  
degree4  ,the boiling point of water1   
being #bab degrees1 is #ahj degrees     
above the  freezing point of water--the 
freezing point being #cb degrees2 so    
that it  requires #aahj times as much   
heat to raise #a lb4 of water into      
steam1 as to  raise #aahj lbs4 of water 

one degree2 or it requires about as much
 heat to  raise a pound of boiling water
 into steam1 as would raise #e-a_/b lbs4
 of  water from the freezing to the     
boiling point2 #e-a_/b multiplied by    
#ahj being  #iij or #ajjj nearly4       
#acf4 ,q4--,when it is stated that the  
latent heat of steam is #ajjj degrees1  
it is only meant that this is a rough   
approximation to the truth8             
,a4--,precisely so4 ,the latent heat1 in
 point of fact1 is not uniform at  all  
temperatures1 neither is the total      
amount of heat the same at all          
temperatures4 ,m4 ,regnault has shown1  
by a very elaborate series of           
experiments on steam1 which he has      
lately concluded1 that the total heat in
  steam increases somewhat with the     
pressure1 and that the latent heat      
diminishes somewhat with the pressure4  
,this will be made obvious by the       
following numbers3    ,pressure4        
,temperature4             ,total ,heat4 
,latent ,heat4    #ae lbs4              

#bac4a                  #aagh4i         
#ife4h    #ej                 #bha4j    
#aaii4f            #iah4f   #ajj        
#cbg4h                   #abac4i        
#hhf4a    ,if1 then1 steam of #ajj lbs4 
be expanded down to steam of #ae lbs41  
it will  have #ce degrees of heat over  
that which is required for the          
maintenance of  the vaporous state1 or1 
in other words1 it will be surcharged   
with heat4    #acg4 ,q4--,what do you   
understand by specific heat8    ,a4--,by
 specific heat1 ,i understand the       
relative quantities of heat in  bodies  
at the same temperature1 just as by     
specific gravity ,i understand  the     
relative quantities of matter in bodies 
of the same bulk4 ,equal weights  of    
quicksilver and water at the same       
temperature do not contain the same     
quantities of heat1 any more than equal 
bulks of those liquids contain the  same
 quantity of matter4 ,the absolute      
quantity of heat in any body is not     
known2 but the relative heat of bodies  

at the same temperature1 or in other    
words their specific heats1 have been   
ascertained and arranged in tables1--   
the specific heat of water being taken  
as unity4    #ach4 ,q4--,in what way    
does the specific heat of a body enable 
the quantity  of heat in it to be       
determined8    ,a4--,if any body has    
only half the specific heat of water1   
then a pound of  that body will1 at any 
given temperature1 have only half the   
heat in it  that is in a pound of water 
at the same temperature4 ,the specific  
heat of  air is 4#bffi1 that of water   
being #a2 or it is #c4ge times less than
 that of  water4 ,an amount of heat1    
therefore1 which would raise a pound of 
water #a  degree would raise a pound of 
air #c4ge degrees4        ,,combustion4 
#aci4 ,q4--,what is the nature of       
combustion8    ,a4--,combustion is      
nothing more than an energetic chemical 
combination1  or1 in other words1 it is 
the mutual neutralization of opposing   
electricities4 ,when coal is brought to 

a high temperature it acquires a  strong
 affinity for oxygen1 and combination   
with oxygen will produce more  than     
sufficient heat to maintain the original
 temperature2 so that part of  the heat 
is rendered applicable to other         
purposes4    #adj4 ,q4--,does air       
consist of oxygen8    ,a4--,air consists
 of oxygen and nitrogen mixed together  
in the proportion  of #c4bi lbs4 of     
nitrogen to #a lb4 of oxygen4 ,every    
pound of coal requires  about #b4ff lbs4
 of oxygen for its saturation1 and      
therefore for every pound  of coal      
burned1 #h4ge pounds of nitrogen must   
pass through the fire1  supposing all   
the oxygen to enter into combination4   
,in practice1 however1  this perfection 
of combination does not exist2 from     
one-third to one-half  of the oxygen    
will pass through the fire without      
entering into combination  at all2 so   
that from #af to #ah lbs4 of air are    
required for every pound of  coal       
burned4 #ah lbs4 of air are about #bdj  

cubic feet1 which may be taken as  the  
quantity of air required for the        
combustion of a pound of coal in        
practice4    #ada4 ,q4--,what are the   
constituents of coal8    ,a4--,the chief
 constituent of coal is carbon or pure  
charcoal1 which is  associated in       
various proportions with volatile and   
earthy matters4 ,english  coal contains 
#hj to #ij per cent4 of carbon1 and from
 #h to #ah per cent4 of  volatile and   
earthy matters1 but sometimes more than 
this4 ,the volatile  matters are        
hydrogen1 nitrogen1 oxygen1 and sulphur4
    #adb4 ,q4--,what is the difference  
between anthracite and bituminous coal8 
,a4--,anthracite consists almost        
entirely of carbon1 having #ia per cent4
 of  carbon1 with about #g per cent4 of 
volatile matter and #b per cent4 of     
ashes4  ,newcastle coal contains about  
#hc per cent4 of carbon1 #ad per cent4  
of  volatile matter1 and #c per cent4 of
 ashes4    #adc4 ,q4--,will you         
recapitulate the steps by which you     

determine the  quantity of air required 
for the combustion of coal8             
,a4--,looking to the quantity of oxygen 
required to unite chemically with  the  
various constituents of the coal1 we    
find for example that in #ajj lbs4  of  
anthracite coal1 consisting of #ia4dd   
lbs4 of carbon1 and #c4df lbs4 of       
hydrogen1 we shall for the #ia4dd lbs4  
of carbon require #bdc4hd lbs4 of       
oxygen--since to saturate a pound of    
carbon by the formation of carbonic     
acid1 requires #b-b_/c lbs4 of oxygen4  
,to saturate a pound of hydrogen in the 
formation of water1 requires #h lbs4 of 
oxygen2 hence #c4df ,fibs4 of hydrogen  
will take #bg4fh lbs4 of oxygen for its 
saturation4 ,if then we add #bdc4hd     
lbs4 to #bg4fh lbs4 we have #bga4eb lbs4
 of oxygen required for the  combustion 
of #ajj lbs4 of coal4 ,a given weight of
 air contains nearly #bc4cb  per cent of
 oxygen2 hence to obtain #bga4eb lbs4 of
 oxygen1 we must have  about four times 
that quantity of atmospheric air1 or    

more accurately1 #aafd  lbs4 of air for 
the combustion of #ajj lbs4 of coal4 ,a 
cubic foot of air at  ordinary          
temperature weighs about 4#jge lbs42 so 
that #ajj lbs4 of coal  require #ae1ebd 
cubic feet of air1 or #a lb4 of coal    
requires about #aee cubic  feet of air1 
supposing every atom of the oxygen to   
enter into combination4  ,if1 then1 from
 one-third to one-half of the air passes
 unconsumed through  the fire1 an       
allowance of #bdj cubic feet of air for 
each pound of coal will  be a small     
enough allowance to answer the          
requirements of practice1 and in  some  
cases as much as #cjj cubic feet will be
 required1--the difference  depending   
mainly on the peculiar configuration of 
the furnace4    #add4 ,q4--,can you     
state the evaporative efficacy of a     
pound of coal8    ,a4--,the evaporative 
efficacy of a pound of carbon has been  
found  experimentally to be equivalent  
to that necessary to raise #ad1jjj lbs4 
of  water through #a degree1 or #ad lbs4

 of water through #ajjj degrees1        
supposing  the whole heat generated to  
be absorbed by the water4 ,now1 if the  
water be  raised into steam from a      
temperature of #fj1 then #aaah4i of heat
 will have  to be imparted to it to     
convert it into steam of #ae lbs4       
pressure per  square inch4 #ad1jjj _/   
#aaah4i  #ab4eab ,lbs4 will be the      
number of pounds of  water1 therefore1  
which a pound of carbon can raise into  
steam of #ae lbs4  pressure from a      
temperature of #fj4 ,this1 however1 is a
 considerably larger  result than can be
 expected in practice4    #ade4         
,q4--,then what is the result that may  
be expected in practice8    ,a4--,the   
evaporative powers of different coals   
appear to be nearly  proportional to the
 quantity of carbon in them2 and        
bituminous coal is1  therefore1 less    
efficacious than coal consisting chiefly
 of pure carbon4 ,a  pound of the best  
,welsh or anthracite coal is capable of 
raising from #i-a_/b  to #aj lbs4 of    

water from #bab into steam1 whereas a   
pound of the best  ,newcastle is not    
capable of raising more than about      
#h-a_/b lbs4 of water  from #bab into   
steam2 and inferior coals will not raise
 more than #f-a_/b  lbs4 of water into  
steam4 ,in ,america it has been found   
that #a lb4 of the  best coal is equal  
to #b-a_/b lbs4 of pine wood1 or1 in    
some cases to #c lbs42  and a pound of  
pine wood will not usually evaporate    
more than about #b #a_/b  lbs4 of water1
 though1 by careful management1 it may  
be made to evaporate #d  #a_/b lbs4     
,turf will generate rather more steam   
than wood4 ,coke is equal or  somewhat  
superior to the best coal in evaporative
 effect4    #adf4 ,q4--,how much water  
will a pound of coal raise into steam in
 ordinary  boilers8    ,a4--,from #f to 
#h lbs4 of water in the generality of   
land boilers of medium  quality1 the    
difference depending on the kind of     
boiler1 the kind of coal1  and other    
circumstances4 ,mr4 ,watt reckoned his  

boilers as capable of  evaporating      
#aj4jh cubic feet of water with a bushel
 or #hd lbs4 of ,newcastle  coal1 which 
is equivalent to #g #a_/b lbs4 of water 
evaporated by #a lb4 of  coal1 and this 
may be taken as the performance of      
common land boilers at  the present     
time4 ,in some of the ,cornish boilers1 
however1 a pound of coal  raises #aa4h  
lbs4 of boiling water into steam1 or a  
cwt4 of coal evaporates  about #ba cubic
 feet of water from #bab4    #adg4      
,q4--,what method of firing ordinary    
furnaces is the best8    ,a4--,the coals
 should be broken up into small pieces1 
and sprinkled thinly  and evenly over   
the fire a little at a time4 ,the       
thickness of the stratum  of coal upon  
the grate should depend upon the        
intensity of the draught3 in  ordinary  
land or marine boilers it should be     
thin1 whereas in locomotive  boilers it 
requires to be much thicker4 ,if the    
stratum of coal be thick  while the     
draught is sluggish1 the carbonic acid  

resulting from combustion  combines with
 an additional atom of carbon in passing
 through the fire1 and  is converted    
into carbonic oxide1 which may be       
defined to be invisible  smoke1 as it   
carries off a portion of the fuel3 if1  
on the contrary1 the  stratum of coal be
 thin while the draught is very rapid1  
an injurious  refrigeration is          
occasioned by the excess of air passing 
through the  furnace4 ,the fire should  
always be spread of uniform thickness   
over the  bars of the grate1 and should 
be without any holes or uncovered       
places1  which greatly diminish the     
effect of the fuel by the refrigeratory 
action  of the stream of cold air which 
enters thereby4 ,a wood fire requires to
 be  about #f inches thicker than a coal
 one1 and a turf fire requires to be #c 
or  #d inches thicker than a wood one1  
so that the furnace bars must be placed 
lower where wood or turf is burned1 to  
enable the surface of the fire to be  at
 the same distance from the bottom of   

the boiler4    #adh4 ,q4--,is a slow or 
a rapid combustion the most beneficial8 
,a4--,a slow combustion is found by     
experiment to give the best results as  
regards economy of fuel1 and theory     
tells us that the largest advantage     
will necessarily be obtained where      
adequate time has been afforded for a   
complete combination of the constituent 
atoms of the combustible1 and the       
supporter of combustion4 ,in many of the
 cases1 however1 which occur in         
practice1 a slow combustion is not      
attainable2 but the tendencies of slow  
combustion are both to save the fuel1   
and to burn the smoke4    #adi4 ,q4--,is
 not the combustion in the furnaces of  
the ,cornish boilers  very slow8        
,a4--,yes1 very slow2 and there is in   
consequence very little smoke evolved4  
,the coal used in ,cornwall is ,welsh   
coal1 which evolves but little smoke1   
and is therefore more favorable for the 
success of a smokeless furnace2 but  in 
the manufacturing districts1 where the  

coal is more bituminous1 it is  found   
that smoke may be almost wholly         
prevented by careful firing and by  the 
use of a large capacity of furnace4     
#aej4 ,q4--,do you consider slow        
combustion to be an advisable thing to  
practise in steam vessels8    ,a4--,no1 
,i do not4 ,when the combustion is slow1
 the heat in the furnaces  and flues is 
less intense1 and a larger amount of    
heating surface  consequently becomes   
necessary to absorb the heat4 ,in       
locomotives1 where  the heat of the     
furnace is very intense1 there will be  
the same economy of  fuel with an       
allowance of #e or #f square feet of    
surface to evaporate a  cubic foot of   
water as in common marine boilers with  
#aj or #ab4    #aea4 ,q4--,what is the  
method of consuming smoke pursued in the
  manufacturing districts8    ,a4--,in  
,manchester1 where some stringent       
regulations for the prevention of  smoke
 have for some time been in force1 it is
 found that the readiest way  of burning

 the smoke is to have a very large      
proportion of furnace room1  whereby    
slow combustion may be carried on4 ,in  
some cases1 too1 a favourable  result is
 arrived at by raising a ridge of coal  
across the furnace lying  against the   
bridge1 and of the same height3 this    
ridge speedily becomes a  mass of       
incandescent coke1 which promotes the   
combustion of the smoke  passing over   
it4    #aeb4 ,q4--,is the method of     
admitting a stream of air into the flues
 to  burn the smoke regarded favorably8 
,a4--,no2 it is found to be productive  
of injury to the boiler by the  violent 
alternations of temperature it          
occasions1 as at some times cold air    
impinges on the iron of the boiler1 and 
at other times flame1--just as  there   
happens to be smoke or no smoke emitted 
by the furnace4 ,boilers1  therefore1   
operating upon this principle1 speedily 
become leaky1 and are  much worn by     
oxidation1 so that1 if the pressure is  
considerable1 they are  liable to       

explode4 ,it is very difficult to       
apportion the quantity of air  admitted1
 to the varying wants of the fire2 and  
as air may at some times be  rushing in 
when there is no smoke to consume1 a    
loss of heat1 and an  increased         
consumption of fuel may be the result of
 the arrangement2 and1  indeed1 such is 
the result in practice1 though a        
carefully performed  experiment usually 
demonstrates a saving in fuel of #aj or 
#ab per cent4    #aec4 ,q4--,what other 
plans have been contrived for obviating 
the nuisance  of smoke8    ,a4--,they   
are too various for enumeration1 but    
most of them either operate  upon the   
principle of admitting air into the     
flues to accomplish the  combustion of  
the uninflammable parts of the smoke1 or
 seek to attain the  same object by     
passing the smoke over or through the   
fire or other  incandescent material4   
,some of the plans1 indeed1 profess to  
burn the  inflammable gases as they are 
evolved from the coal1 without          

permitting the  admixture of any of the 
uninflammable products of combustion    
which enter  into the composition of    
smoke2 but this object has been very    
imperfectly  fulfilled in any of the    
contrivances yet brought under the      
notice of the  public1 and in some cases
 these contrivances have been found to  
create  weightier evils than they       
professed to relieve4    #aed4 ,q4--,you
 refer1 ,i suppose1 to ,mr4 ,charles    
,wye ,williams' ,argand  furnace8       
,a4--,i chiefly refer to it1 though ,i  
also comprehend all other schemes in    
which there is a continuous admission of
 air into the flues1 with an            
intermittent generation of smoke4       
#aee4 ,q4--,this is not so in           
,prideaux's furnace8    ,a4--,no2 in    
that furnace the air is admitted only   
during a certain  interval1 or for so   
long1 in fact1 as there is smoke to be  
consumed4    #aef4 ,q4--,will you       
explain the chief peculiarities of that 
furnace8    ,a4--,the whole peculiarity 

is in the furnace door4 ,the front of   
the door  consists of metal ,venetians1 
which are opened when the top lever is  
lifted  up1 and shut when that lever    
descends to its lowest position4 ,when  
the  furnace door is opened to replenish
 the fire with coals1 the top lever is  
raised up1 and with it the piston of the
 small cylinder attached to the  side of
 the furnace4 ,the ,venetians are       
thereby opened1 and a stream of air     
enters the furnace1 which1 being heated 
in its passage among the numerous       
heated plates attached to the back of   
the furnace door1 is in a favorable     
condition for effecting the combustion  
of the inflammable parts of the  smoke4 
,the piston in the small cylinder       
gradually subsides and closes the       
,venetians2 and the rate of the         
subsidence of the piston may obviously  
be  regulated by a cock1 or1 as in this 
case1 a small screw valve1 so that the  
,venetians shall just close when there  
is no more smoke to be consumed2--the   

air or other fluid within the cylinder  
being forced out by the piston in  its  
descent4    #aeg4 ,q4--,had ,mr4 ,watt  
any method of consuming smoke8          
,a4--,he tried various methods1 but     
eventually fixed upon the method of     
coking the coal on a dead plate at the  
furnace door1 before pushing it into    
the fire4 ,that method is perfectly     
effectual where the combustion is so    
slow that the requisite time for coking 
is allowed1 and it is much  preferable  
to any of the methods of admitting air  
at the bridge or  elsewhere1 to         
accomplish the combustion of the        
inflammable parts of the  smoke4        
#aeh4 ,q4--,what are the details of ,mr4
 ,watt's arrangement as now employed8   
,a4--,the fire bars and the dead plate  
are both set at a considerable          
inclination1 to facilitate the advance  
of the fuel into the furnace4 ,in       
,boulton and ,watt's #cj horse power    
land boiler1 the dead plate and the     
furnace bars are both about #d feet     

long1 and they are set at the angle of  
#cj degrees with the horizon4    #aei4  
,q4--,is the use of the dead plate      
universally adopted in ,boulton and     
,watt's land boilers8    ,a4--,it is    
generally adopted1 but in some cases    
,boulton and ,watt have  substituted the
 plan of a revolving grate for consuming
 the smoke1 and the  dead plate then    
becomes both superfluous and            
inapplicable4 ,in this  contrivance the 
fire is replenished with coals by a     
self-acting mechanism4    #afj4         
,q4--,will you explain the arrangement  
of the revolving grate8    ,a4--,the    
fire grate is made like a round table   
capable of turning  horizontally upon a 
centre2 a shower of coal is precipitated
 upon the grate  through a slit in the  
boiler near the furnace mouth1 and the  
smoke evolved  from the coal dropped at 
the front part of the fire is consumed  
by passing  over the incandescent fuel  
at the back part1 from which all the    
smoke must  have been expelled in the   

revolution of the grate before it can   
have  reached that position4    #afa4   
,q4--,is a furnace with a revolving     
grate applicable to a steam  vessel8    
,a4--,i see nothing to prevent its      
application4 ,but the arrangement of the
  boiler would perhaps require to be    
changed1 and it might be preferable to  
combine its use with the employment of  
vertical tubes1 for the transmission  of
 the smoke4 ,the introduction of any    
effectual automatic contrivance for     
feeding the fire in steam vessels1 would
 bring about an important economy1  at  
the same time that it would give the    
assurance of the work being better      
done4 ,it is very difficult to fire     
furnaces by hand effectually at sea1    
especially in rough weather and in      
tropical climates2 whereas machinery    
would be unaffected by any such         
disturbing causes1 and would perform    
with  little expense the work of many   
men4    #afb4 ,q4--,the introduction of 
some mechanical method of feeding the   

fire  with coals would enable a double  
tier of furnaces to be adopted in steam 
vessels without inconvenience8          
,a4--,yes1 it would have at least that  
tendency2 and as the space available    
for area of grate is limited in a steam 
vessel by the width of the vessel1  it  
would be a great convenience if a double
 tier of furnaces could be  employed    
without a diminished effect4 ,it appears
 to me1 however1 that the  objection    
would still remain of the steam raised  
by the lower furnace being  cooled and  
deadened by the air entering the ash-pit
 of the upper fire1 for  it would strike
 upon the metal of the ash-pit bottom4  
#afc4 ,q4--,have any other plans been   
devised for feeding the fire by         
self-acting means besides that of a     
revolving grate8    ,a4--,yes1 many     
plans1 but none of them1 perhaps1 are   
free from an  objectionable             
complication4 ,in some arrangements the 
bars are made like  screws1 which being 
turned round slowly1 gradually carry    

forward the coal2  while in other       
arrangements the same object is sought  
to be attained by  alternately lifting  
and depressing every second bar at the  
end nearest the  mouth of the furnace4  
,in ,juckes' furnace1 the fire bars are 
arranged in the  manner of rows of      
endless chains working over a roller at 
the mouth of the  furnace1 and another  
roller at the farther end of the        
furnace4 ,these  rollers are put into   
slow revolution1 and the coal which is  
deposited at  the mouth of the furnace  
is gradually carried forward by the     
motion of the  chains1 which act like an
 endless web4 ,the clinkers and ashes   
left after  the combustion of the coal1 
are precipitated into the ash-pit1 where
 the  chain turns down over the roller  
at the extremity of the furnace4 ,in    
,messrs4 ,maudslays' plan of a          
self-feeding furnace the fire bars are  
formed  of round tubes1 and are placed  
transversely across the furnace4 ,the   
ends of  the bars gear into endless     

screws running the whole length of the  
furnace1  whereby motion is given to the
 bars1 and the coal is thus carried     
gradually  forward4 ,it is very doubtful
 whether any of these contrivances      
satisfy all  the conditions required in 
a plan for feeding furnaces of the      
ordinary form  by self-acting means1 but
 the problem of providing a suitable    
contrivance1  does not seem difficult of
 accomplishment1 and will no doubt be   
effected  under adequate temptation4    
#afd4 ,q4--,have not many plans been    
already contrived which consume the     
smoke of furnaces very effectually8     
,a4--,yes1 many plans2 and besides those
 already mentioned there are  ,hall's1  
,coupland's1 ,godson's1 ,robinson's1    
,stevens's1 ,hazeldine's1 ,indie's1     
,bristow and ,attwood's1 and a great    
number of others4 ,one plan1 which      
promises well1 consists in making the   
flame descend through the fire bars1    
and the fire bars are formed of tubes   
set on an incline and filled with       

water1 which water will circulate with a
 rapidity proportionate to the          
intensity of the heat4 ,after all1      
however1 the best remedy for smoke      
appears to consist in removing from it  
those portions which form the smoke     
before the coal is brought into use4    
,many valuable products may be got from 
the coal by subjecting it to this       
treatment2 and the residuum will be more
  valuable than before for the          
production of steam4        ,,steam4    
#afe4 ,q4--,have experiments been made  
to determine the elasticity of steam  at
 different temperatures8    ,a4--,yes2  
very careful experiments4 ,the following
 rule expresses the  results obtained by
 ,mr4 ,southern3--,to the given         
temperature in degrees of  ,fahrenheit  
add #ea4c degrees2 from the logarithm of
 the sum1 subtract the  logarithm of    
#ace4gfg1 which is #b4acbgidj2 multiply 
the remainder by #e4ac1  and to the     
natural number answering to the sum1 add
 the constant  fraction 4#a1 which will 

give the elastic force in inches of     
mercury4 ,if the  elastic force be      
known1 and it is wanted to determine the
 corresponding  temperature1 the rule   
must be modified thus3--,from the       
elastic force1 in  inches of mercury1   
subtract the decimal 4#a1 divide the    
logarithm of the  remainder by #e4ac1   
and to the quotient add the logarithm   
#b4acbgidj2 find  the natural number    
answering to the sum1 and subtract      
therefrom the  constant #ea4c2 the      
remainder will be the temperature       
sought4 ,the ,french  ,academy1 and the 
,franklin ,institute1 have repeated ,mr4
 ,southern's  experiments on a larger   
scale2 the results obtained by them are 
not widely  different1 and are perhaps  
nearer the truth1 but ,mr4 ,southern's  
results are  generally adopted by       
engineers1 as sufficiently accurate for 
practical  purposes4    #aff4 ,q4--,have
 not some superior experiments upon this
 subject been lately  made in ,france8  
,a4--,yes1 the experiments of ,m4       

,regnault upon this subject have been   
very  elaborate and very carefully      
conducted1 and the results are probably 
more  accurate than have been heretofore
 obtained4 ,nevertheless1 it is         
questionable how far it is advisable to 
disturb the rules of ,watt and          
,southern1 with which the practice of   
engineers is very much identified1 for  
the sake of emendations which are not of
 such magnitude as to influence         
materially the practical result4 ,m4    
,regnault has shown that the total      
amount of heat1 existing in a given     
weight of steam1 increases slightly     
with the pressure1 so that the sum of   
the latent and sensible heats do not    
form a constant quantity4 ,thus1 in     
steam of the atmospheric pressure1 or   
with #ad4g ,lbs4 upon the square inch1  
the sensible heat of the steam is #bab  
degrees1 the latent heat #iff4f degrees1
 and the sum of the latent and  sensible
 heats #aagh4f degrees2 whereas in steam
 of #ij pounds upon the  square inch the

 sensible heat is #cbj4b degrees1 the   
latent heat #hia4d  degrees1 and the sum
 of the latent and sensible heats       
#abaa4j degrees4 ,there  is1 therefore1 
#cc degrees less of heat in any given   
weight of water1 raised  into steam of  
the atmospheric pressure1 than if raised
 into steam of #ij  ,lbs4#a pressure4   
#afg4 ,q4--,what expansion does water   
undergo in its conversion into steam8   
,a4--,a cubic inch of water makes about 
a cubic foot of steam of the            
atmospheric pressure4    #afh4 ,q4--,and
 how much at a higher pressure8         
,a4--,that depends upon what the        
pressure is4 ,but the proportion is     
easily  ascertained1 for the pressure   
and the bulk of a given quantity of     
steam1 as  of air or any other elastic  
fluid1 are always inversely proportional
 to one  another4 ,thus if a cubic inch 
of water makes a cubic foot of steam1   
with  the pressure of one atmosphere1 it
 will make half a cubic foot with the   
pressure of two atmospheres1 a third of 

a cubic foot with the pressure of  three
 atmospheres1 and so on in all other    
proportions4 ,high pressure steam       
indeed is just low pressure steam forced
 into a less space1 and the  pressure   
will always be great in the proportion  
in which the space is  contracted4      
#afi4 ,q4--,if this be so1 the quantity 
of heat in a given weight of steam  must
 be nearly the same1 whether the steam  
is high or low pressure8    ,a4--,yes2  
the heat in steam is nearly a constant  
quantity1 at all  pressures1 but not so 
precisely4 ,steam to which an additional
 quantity of  heat has been imparted    
after leaving the boiler1 or as it is   
called  surcharged steam1 comes under a 
different law1 for the elasticity of    
such  steam may be increased without any
 addition being made to its weight2 but 
surcharged steam is not at present      
employed for working engines1 and it may
  therefore be considered in practice   
that a pound of steam contains very     
nearly the same quantity of heat at all 

pressures4    #agj4 ,q4--,does not the  
quantity of heat in any body vary with  
the  temperature8    ,a4--,other        
circumstances remaining the same the    
quantity of heat in a body  increases   
with the temperatures4    #aga4         
,q4--,and is not high pressure steam    
hotter than low pressure steam8         
,a4--,yes1 the temperature of steam     
rises with the pressure4    #agb4       
,q4--,how then comes it1 that there is  
the same quantity of heat in  the same  
weight of high and low pressure steam1  
when the high pressure  steam has the   
highest temperature8    ,a4--,because   
although the temperature or sensible    
heat rises with the  pressure1 the      
latent heat becomes less in about the   
same proportion4 ,and as  has been      
already explained1 the latent and       
sensible heats taken together  make up  
nearly the same amount at all           
temperatures2 but the amount is         
somewhat greater at the higher          
temperatures4 ,as a damp sponge becomes 

wet  when subjected to pressure1 so warm
 vapor becomes hot when forced into less
  bulk1 but in neither case does the    
quantity of moisture or the quantity of 
heat sustain any alteration4 ,common air
 becomes so hot by compression that     
tinder may be inflamed by it1 as is seen
 in the instrument for producing        
instantaneous light by suddenly forcing 
air into a syringe4    #agc4 ,q4--,what 
law is followed by surcharged steam on  
the application of  heat8    ,a4--,the  
same as that followed by air1 in which  
the increments in volume  are very      
nearly in the same proportion as the    
increments in temperature2  and the     
increment in volume for each degree of  
increased temperature is  #a_/dijth part
 of the volume at #cb4 ,a volume of air 
which1 at the  temperature of #cb1      
occupies #ajj cubic feet1 will at #bab  
fill a space of  #acf4gc cubic feet4    
,the volume which air or steam--out of  
contact with  water--of a given         
temperature acquires by being heated to 

a higher  temperature1 the pressure     
remaining the same1 may be found by the 
following  rule3--,to each of the       
temperatures before and after expansion1
 add the  constant number #deh3 divide  
the greater sum by the less1 and        
multiply the  quotient by the volume at 
the lower temperature2 the product will 
give the  expanded volume4    #agd4     
,q4--,if the relative volumes of steam  
and water are known1 is it  possible to 
tell the quantity of water which should 
be supplied to a  boiler1 when the      
quantity of steam expended is specified8
    ,a4--,yes2 at the atmospheric       
pressure1 about a cubic inch of water   
has to  be supplied to the boiler for   
every cubic foot of steam abstracted2 at
  other pressures1 the relative bulk of 
water and steam may be determined as    
follows3--,to the temperature of steam  
in degrees of ,fahrenheit1 add the      
constant number #deh1 multiply the sum  
by #cg4c1 and divide the product by  the
 elastic force of the steam in pounds   

per square inch2 the quotient will  give
 the volume required4    #age4          
,q4--,will this rule give the proper    
dimensions of the pump for  feeding the 
boiler with water8    ,a4--,no2 it is   
necessary in practice that  the feed    
pump should be able to supply the boiler
 with a much larger  quantity of water  
than what is indicated by these         
proportions1 from the  risk of leaks1   
priming1 or other disarrangements1 and  
the feed pump is  usually made capable  
of raising #c-a_/b times the water      
evaporated by the  boiler4 ,about       
#a_/bdjth of the capacity of the        
cylinder answers very well for  the     
capacity of the feed pump in the case of
 low pressure engines1  supposing the   
cylinder to be double acting1 and the   
pump single acting2 but  it is better to
 exceed this size4    #agf4 ,q4--,is    
this rule for the size of the feed pump 
applicable to the  case of high pressure
 engines8    ,a4--,clearly not2 for     
since a cylinder full of high pressure  

steam1  contains more water than the    
same cylinder full of low pressure      
steam1 the  size of the feed must vary  
in the same proportion as the density of
 the  steam4 ,in all pumps a good deal  
of the effect is lost from the imperfect
  action of the valves2 and in engines  
travelling at a high rate of speed1 in  
particular1 a large part of the water is
 apt to return1 through the suction     
valve of the pump1 especially if much   
lift be permitted to that valve4 ,in    
steam vessels moreover1 where the boiler
 is fed with salt water1 and where  a   
certain quantity of supersalted water   
has to be blown out of the boiler  from 
time to time1 to prevent the water from 
reaching too high a degree of           
concentration1 the feed pump requires to
 be of additional size to supply  the   
extra quantity of water thus rendered   
necessary4 ,when the feed water is      
boiling or very hot1 as in some engines 
is the case1 the feed pump will not     
draw from a depth1 and will altogether  

act less efficiently1 so that an  extra 
size of pump has to be provided in      
consequence4 ,these and other           
considerations which might be mentioned1
 show the propriety of making the  feed 
pump very much larger than theory       
requires4 ,the proper proportions of    
pumps1 however1 forms part of a         
subsequent chapter4      #a ,a table    
containing the results arrived at by ,m4
 ,regnault is given in  the ,key4       
,,chapter ,,iii4    ,,expansion ,,of    
,,steam ,,and ,,action ,,of ,,the       
,,valves4      #agg4 ,q4--,what is meant
 by working engines expansively8        
,a4--,adjusting the valves1 so that the 
steam is shut off from the cylinder     
before the end of the stroke1 whereby   
the residue of the stroke is left to  be
 completed by the expanding steam4      
#agh4 ,q4--,and what is the benefit of  
that practice8    ,a4--,it accomplishes 
an important saving of steam1 or1 what  
is the same  thing1 of fuel2 but it     
diminishes the power of the engine1     

while increasing  the power of the      
steam4 ,a larger engine will be required
 to do the same  work1 but the work will
 be done with a smaller consumption of  
fuel4 ,if1 for  example1 the steam be   
shut off when only half the stroke is   
completed1  there will only be half the 
quantity of steam used4 ,but there will 
be more  than half the power exerted2   
for although the pressure of the steam  
decreases after the supply entering from
 the boiler is shut off1 yet it         
imparts1 during its expansion1 some     
power1 and that power1 it is clear1  is 
obtained without any expenditure of     
steam or fuel whatever4    #agi4        
,q4--,what will be the pressure of the  
steam1 under such  circumstances1 at the
 end of the stroke8    ,a4--,if the     
steam be shut off at half stroke1 the   
pressure of the steam1  reckoning the   
total pressure both below and above the 
atmosphere1 will just  be one-half of   
what it was at the beginning of the     
stroke4 ,it is a well  known law of     

pneumatics1 that the pressure of elastic
 fluids varies  inversely as the spaces 
into which they are expanded or         
compressed4 ,for  example1 if a cubic   
foot of air of the atmospheric density  
be compressed  into the compass of half 
a cubic foot1 its elasticity will be    
increased  from #ae lbs4 on the square  
inch to #cj lbs4 on the square inch2    
whereas1 if  its volume be enlarged to  
two cubic feet1 its elasticity will be  
reduced to  #g-a_/b lbs4 on the square  
inch1 being just half its original      
pressure4 ,the  same law holds in all   
other proportions1 and with all other   
gases and  vapors1 provided their       
temperature remains unchanged2 and if   
the steam  valve of an engine be closed1
 when the piston has descended through  
one- fourth of the stroke1 the steam    
within the cylinder will1 at the end  of
 the stroke1 just exert one-fourth of   
its initial pressure4    #ahj4          
,q4--,then by computing the varying     
pressure at a number of stages1  the    

average or mean pressure throughout the 
stroke may be approximately  determined8
    ,illustration3 ,fig4 #cb4 ,diagram  
showing law of expansion of steam in a  
cylinder4    ,a4--,precisely so4 ,thus  
in the accompanying figure1 7fig4 #cb71 
let ,e be a  cylinder1 ,j the piston1 a 
the steam pipe1 c the upper port1 f the 
lower port1 d the steam pipe1 prolonged 
to e the equilibrium valve1 g  the      
eduction valve1 ,m the steam jacket1 ,n 
the cylinder cover1 ,o stuffing  box1 n 
piston rod1 ,p cylinder bottom2 let the 
cylinder be supposed to be  divided in  
the direction of its length into any    
number of equal parts1 say  twenty1 and 
let the diameter of the cylinder        
represent the pressure of the  steam1   
which1 for the sake of simplicity1 we   
may take at #aj lbs41 so that  we may   
divide the cylinder1 in the direction of
 its diameter1 into ten  equal parts4   
,if now the piston be supposed to       
descend through five of the  divisions1 
and the steam valve then be shut1 the   

pressure at each  subsequent position of
 the piston will be represented by a    
series1 computed  according to the laws 
of pneumatics1 and which1 if the initial
 pressure be  represented by #a1 will   
give a pressure of 4#e at the middle of 
the stroke1  and 4#be at the end of it4 
,if this series be set off on the       
horizontal lines1 it will mark out a    
hyperbolic curve--the area of the part  
exterior to which represents the  total 
efficacy of the stroke1 and the interior
 area1 therefore1 represents  the       
diminution in the power of a stroke1    
when the steam is cut off at  one-      
fourth of the descent4 ,if the squares  
above the point1 where the steam  is cut
 off1 be counted1 they will be found to 
amount to #ej2 and if those  beneath    
that point be counted or estimated1 they
 will be found to amount to  about #fi4 
,these squares are representative of the
 power exerted2 so that  while an amount
 of power represented by #ej has been   
obtained by the  expenditure of a       

quarter of a cylinder full of steam1 we 
get an amount of  power represented by  
#fi1 without any expenditure of steam at
 all1 merely by  permitting the steam   
first used to expand into four times its
 original  volume4    #aha4 ,q4--,then  
by working an engine expansively1 the   
power of the steam is  increased1 but   
the power of the engine is diminished8  
,a4--,yes4 ,the efficacy of a given     
quantity of steam is more than doubled  
by expanding the steam four times1 while
 the efficacy of each stroke is  made   
nearly one-half less4 ,and1 therefore1  
to carry out the expansive  principle in
 practice1 the cylinder requires to be  
larger than usual1 or  the piston faster
 than usual1 in the proportion in which 
the expansion is  carried out4 ,every   
one who is acquainted with simple       
arithmetic1 can  compute the terminal   
pressure of steam in a cylinder1 when he
 knows the  initial pressure and the    
point at which the steam is cut off2 and
 he can  also find1 by the same process1

 any pressure intermediate between the  
first  and the last4 ,by setting down   
these pressures in a table1 and taking  
their  mean1 he can determine the       
effect1 with tolerable accuracy1 of any 
particular measure of expansion4 ,it is 
necessary to remark1 that it is the     
total pressure of the steam that he must
 take2 not the pressure above the       
atmosphere1 but the pressure above a    
perfect vacuum4    #ahb4 ,q4--,can you  
give any rule for ascertaining at one   
operation the  amount of benefit        
derivable from expansion8               
,a4--,divide the length of stroke       
through which the steam expands1 by the 
length of stroke performed with full    
pressure1 which last call #a2 the       
hyperbolic logarithm of the quotient is 
the increase of efficiency due to       
expansion4 ,according to this rule it   
will be found1 that if a given  quantity
 of steam1 the power of which working at
 full pressure is  represented by #a1 be
 admitted into a cylinder of such a size

 that its  ingress is concluded when    
one-half the stroke has been performed1 
its  efficacy will be raised by         
expansion to #a4fi2 if the admission of 
the steam  be stopped at one-third of   
the stroke1 the efficacy will be #b4aj2 
at  one- fourth1 #b4ci2 at one-fifth1   
#b4fa2 at one-sixth1 #b4gi2 at          
one-seventh1  #b4ie2 at one-eighth1     
#c4jh4 ,the expansion1 however1 cannot  
be carried  beneficially so far as      
one-eighth1 unless the pressure of the  
steam in the  boiler be very            
considerable1 on account of the         
inconvenient size of  cylinder or speed 
of piston which would require to be     
adopted1 the  friction of the engine1   
and the resistance of vapor in the      
condenser1 which  all become relatively 
greater with a smaller urging force4    
#ahc4 ,q4--,is this amount of benefit   
actually realized in practice8          
,a4--,only in some cases4 ,it appears to
 be indispensable to the realization  of
 any large amount of benefit by         

expansion1 that the cylinder should be  
enclosed in a steam jacket1 or should in
 some other way be effectually          
protected from refrigeration4 ,in some  
engines not so protected1 it has been   
found experimentally that less benefit  
was obtained from the fuel by  working  
expansively than by working without     
expansion--the whole benefit  due to    
expansion being more than counteracted  
by the increased  refrigeration due to  
the larger surface of the cylinder      
required to develop  the power4 ,in     
locomotive engines1 with outside        
cylinders1 this condition of  the       
advantageous use of expansion has been  
made very conspicuous1 as has  also been
 the case in screw steamers with four   
cylinders1 and in which the             
refrigerating surface of the cylinders  
was consequently large4    #ahd4        
,q4--,the steam is admitted to and from 
the cylinder by means of a  slide or    
sluice valve8    ,illustration3 ,fig4   
#cc4    ,a4--,yes2 and of the slide     

valve there are many varieties2 but the 
kinds  most in use are the ,d valve1--so
 called from its resemblance to a half  
cylinder or ,d in its cross section--and
 the three ported valve1 shown in  fig4 
#cc1 which consists of a brass or iron  
box set over the two ports or  openings 
into the cylinder1 and a central port   
which conducts away the  steam to the   
atmosphere or condenser2 but the length 
of the box is so  adjusted that it can  
only cover one of the cylinder ports and
 the central  or eduction port at the   
same time4 ,the effect1 therefore1 of   
moving the  valve up and down1 as is    
done by the eccentric1 is to establish a
  connection alternately between each   
cylinder port and the central passage   
whereby the steam escapes2 and while the
 steam is escaping from beneath the     
piston1 the position of the valve is    
such1 that a free communication exists  
between the space above the piston and  
the steam in the boiler4 ,the piston  is
 thus urged alternately up and down--the

 valve so changing its position  before 
the piston arrives at the end of the    
stroke1 that the pressure is by  that   
time thrown on the reverse side of the  
piston1 so as to urge it into  motion in
 the opposite direction4    #ahe4       
,q4--,is the motion of the valve1 then1 
the reverse of that of the  piston8     
,a4--,no4 ,the valve does not move down 
when the piston moves down1 nor does  it
 move down when the piston moves up2 but
 it moves from its mid position1  to the
 extremity of its throw1 and back again 
to its mid position1 while  the piston  
makes an upward or downward movement1 so
 that the motion is as  it were at right
 angles to the motion of the piston2 or 
it is the same  motion that the piston  
of another engine1 the crank of which is
 set at  right angles with that of the  
first engine1 would acquire4    #ahf4   
,q4--,then in a steam vessel the valve  
of one engine may be worked  from the   
piston of the other8    ,a4--,yes1 it   
may2 or it may be worked from its own   

connecting rod2 and in  the case of     
locomotive engines1 this has sometimes  
been done4    #ahg4 ,q4--,what is meant 
by the lead of the valve8    ,a4--,the  
amount of opening which the valve       
presents for the admission of  the      
steam1 when the piston is just beginning
 its stroke4 ,it is found  expedient    
that the valve should have opened a     
little to admit steam on the  reverse   
side of the piston before the stroke    
terminates2 and the amount of  this     
opening1 which is given by turning the  
eccentric more or less round  upon the  
shaft1 is what is termed the lead4      
#ahh4 ,q4--,and what is meant by the lap
 of the valve8    ,a4--,it is an        
elongation of the valve face to a       
certain extent over the  port1 whereby  
the port is closed sooner than would    
otherwise be the case4  ,this extension 
is chiefly effected at that part of the 
valve where the  steam is admitted1 or  
upon the steam side of the valve1 as the
 technical  phrase is2 and the intent of

 the extension is to close the steam    
passage  before the end of the stroke1  
whereby the engine is made to operate to
 a  certain extent expansively4 ,in some
 cases1 however1 there is also a certain
  amount of lap given to the escape or  
eduction side1 to prevent the eduction  
from being performed too soon when the  
lead is great2 but in all cases  there  
is far less lap on the eduction than on 
the steam side1 very often  there is    
none1 and sometimes less than none1 so  
that the valve is incapable  of covering
 both the ports at once4    #ahi4       
,q4--,what is the usual proportional    
length of stroke of the valve8          
,a4--,the common stroke of the valve in 
rotative engines is twice the  breadth  
or depth of the port1 and the length of 
the valve face will then be  just the   
breadth of the port when there is lap on
 neither the steam nor  eduction side4  
,whatever lap is given1 therefore1 makes
 the valve face just  so much longer4   
,in some engines1 however1 the stroke of

 the valve is a good  deal more than    
twice the breadth of the port2 and it is
 to the stroke of  the valve that the   
amount of lap should properly be        
referred4    #aij4 ,q4--,can you tell   
what amount of lap will accomplish any  
given amount  of expansion8             
,a4--,yes1 when the stroke of the valve 
is known4 ,from the length of the       
stroke of the piston subtract that part 
of the stroke which is intended to  be  
accomplished before the steam is cut    
off2 divide the remainder by the  length
 of the stroke of the piston1 and       
extract the square root of the          
quotient1 which multiply by half the    
stroke of the valve1 and from the       
product take half the lead2 the         
remainder will be the lap required4     
#aia4 ,q4--,can you state how we may    
discover at what point of the stroke    
the eduction passage will be closed8    
,a4--,to find how much before the end of
 the stroke the eduction passage  will  
be closed3--to the lap on the steam side

 add the lead1 and divide the  sum by   
half the stroke of the valve2 find the  
arc whose sine is equal to  the         
quotient1 and add #ij to it42 divide the
 lap on the eduction side by  half the  
stroke of the valve1 and find the arc   
whose cosine is equal to the  quotient2 
subtract this arc from the one last     
obtained1 and find the cosine  of the   
remainder2 subtract this cosine from #b1
 and multiply the remainder  by half the
 stroke of the piston2 the product is   
the distance of the piston  from the end
 of the stroke when the eduction passage
 is closed4    #aib4 ,q4--,can you      
explain how we may determine the        
distance of the piston  from the end of 
the stroke1 before the steam urging it  
onward is allowed to  escape8           
,a4--,to find how far the piston is from
 the end of its stroke when the  steam  
that is propelling it by expansion is   
allowed to escape to the  atmosphere or 
condenser--to the lap on the steam side 
add the lead2 divide  the sum by half   

the stroke of the valve1 and find the   
arc whose sine is  equal to the         
quotient2 find the arc whose sine is    
equal to the lap on the  eduction side1 
divided by half the stroke of the valve2
 add these two arcs  together and       
subtract #ij2 find the cosine of the    
residue1 subtract it from  #a1 and      
multiply the remainder by half the      
stroke of the piston2 the product  is   
the distance of the piston from the end 
of its stroke when the steam  that is   
propelling it is allowed to escape into 
the atmosphere or  condenser4 ,in using 
these rules1 all the dimensions are to  
be taken in  inches1 and the answers    
will be found in inches also4    #aic4  
,q4--,is it a benefit or a detriment to 
open the eduction passage  before the   
end of the stroke8    ,a4--,in engines  
working at a high rate of speed1 such as
 locomotive  engines1 it is very        
important to open the exhaust passage   
for the escape of  the steam before the 
end of the stroke1 as an injurious      

amount of back  pressure is thus        
prevented4 ,in the earlier locomotives a
 great loss of  effect was produced from
 inattention to this condition2 and when
 lap was  applied to the valves to      
enable the steam to be worked           
expansively1 it was  found that a still 
greater benefit was collaterally        
obtained by the earlier  escape of the  
steam from the eduction passages1 and   
which was incidental to  the application
 of lap to the valves4 ,the average     
consumption of coke per  mile was       
reduced by ,mr4 ,woods from #dj lbs4 per
 mile to #ae lbs4 per mile1  chiefly by 
giving a free outlet to the escaping    
steam4    #aid4 ,q4--,to what extent can
 expansion be carried beneficially by   
means of  lap upon the valve8           
,a4--,to about one-third of the stroke2 
that is1 the valve may be made with  so 
much lap1 that the steam will be cut off
 when two thirds of the stroke  have    
been performed1 leaving the residue to  
be accomplished by the agency  of the   

expanding steam2 but if more lap be put 
on than answers to this  amount of      
expansion1 a very distorted action of   
the valve will be produced1  which may  
impair the efficiency of the engine4 ,if
 a further amount of  expansion than    
this is wanted1 it may be accomplished  
by wire drawing the  steam1 or by so    
contracting the steam passage that the  
pressure within the  cylinder must      
decline when the speed of the piston is 
accelerated1 as it is  about the middle 
of the stroke4    #aie4 ,q4--,will you  
explain how this result ensues8         
,a4--,if the valve be so made as to shut
 off the steam by the time two  thirds  
of the stroke have been performed1 and  
the steam be at the same time  throttled
 in the steam pipe1 the full pressure of
 the steam within the  cylinder cannot  
be maintained except near the beginning 
of the stroke where  the piston travels 
slowly2 for1 as the speed of the piston 
increases1 the  pressure necessarily    
subsides1 until the piston approaches   

the other end of  the cylinder1 where   
the pressure would rise again but that  
the operation of  the lap on the valve  
by this time has had the effect of      
closing the  communication between the  
cylinder and steam pipe1 so as to       
prevent more  steam from entering4 ,by  
throttling the steam1 therefore1 in the 
manner here  indicated1 the amount of   
expansion due to the lap may be doubled1
 so that  an engine with lap enough upon
 the valve to cut off the steam at      
two-thirds  of the stroke1 may1 by the  
aid of wire drawing1 be virtually       
rendered  capable of cutting off the    
steam at one-third of the stroke4       
#aif4 ,q4--,is this the usual way of    
cutting off the steam8    ,a4--,no2 the 
usual way of cutting off the steam is by
 means of a separate  valve1 termed an  
expansion valve2 but such a device      
appears to be hardly  necessary in      
ordinary engines4 ,in the ,cornish      
engines1 where the steam is  cut off in 
some cases at one-twelfth of the stroke1

 a separate valve for  the admission of 
steam1 other than that which permits its
 escape1 is of  course indispensable2   
but in common rotative engines1 which   
may realize  expansive efficacy by      
throttling1 a separate expansion valve  
does not  appear to be required4        
#aig4 ,q4--,that is1 where much         
expansion is required1 an expansion     
valve is  a proper appendage1 but where 
not much is required1 a separate        
expansion  valve may be dispensed with8 
,a4--,precisely so4 ,the wire drawing of
 the steam causes a loss of part of  its
 power1 and the result will not be quite
 so advantageous by throttling  as by   
cutting off4 ,but for moderate amounts  
of expansion it will suffice1  provided 
there be lap upon the slide valve4      
#aih4 ,q4--,will you explain the        
structure or configuration of expansion 
apparatus of the usual construction8    
,illustration3 ,fig #cd4    ,a4--,the   
structure of expansion apparatus is very
 various2 but all the  kinds operate    

either on the principle of giving such a
 motion to the slide  valve as will     
enable it to cut off the steam1 at the  
desired point1 or on  the principle of  
shutting off the steam by a separate    
valve in the steam  pipe or valve       
casing4 ,the first class of apparatus   
has not been found so  manageable1 and  
is not in extensive use1 except in that 
form known as the  link motion4 ,of the 
second class1 the most simple probably  
is the  application of a cam giving     
motion to the throttle valve1 or to a   
valve of  the same construction1 which  
either accurately fits the steam pipe1  
or  which comes round to a face1 which1 
however1 it is restrained from touching 
by a suitable construction of the cam4  
,a kind of expansion valve1 often       
employed in marine engines of low speed1
 is the kind used in the ,cornish       
engines1 and known as the equilibrium   
valve4 ,this valve is represented in    
fig4 #cd4 ,it consists substantially of 
an annulus or bulging cylinder of       

brass1 with a steam-tight face both at  
its upper and lower edges1 at which     
points it fits accurately upon a        
stationary seat4 ,this annulus may be   
raised or lowered without being resisted
 by the pressure of the steam1 and  in  
rotative engines it is usually worked by
 a cam on the shaft4 ,the  expansion cam
 is put on the shaft in two pieces1     
which are fastened to each  other by    
means of four bolts passing through     
lugs1 and is fixed to the  shaft by     
keys4 ,a roller at one end of a         
bell-crank lever1 which is  connected   
with the expansion valve1 presses       
against the cam1 so that the  motion of 
the lever will work the valve4 ,the     
roller is kept against the cam  by a    
weight on a lever attached to the same  
shaft1 but a spring is  necessary for   
high speeds4 ,if the cam were concentric
 with the shaft1 the  lever which       
presses upon it would remain stationary1
 and also the expansion  valve2 but by  
the projection of the cam1 the end of   

the lever receives a  reciprocating     
motion1 which is communicated to the    
valve4    #aii4 ,q4--,the cam then works
 the valve8    ,a4--,yes4 ,the position 
of the projection of the cam determines 
the point  in relation to the stroke at 
which the valve is opened1 and its      
circumferential length determines the   
length of the time during which the     
valve continues open4 ,the time at which
 the valve should begin to open is  the 
same under all circumstances1 but the   
duration of its opening varies  with the
 amount of expansion desired4 ,in order 
to obtain this variable  extent of      
expansion1 there are several projections
 made upon the cam1 each  of which gives
 a different degree1 or grade as it is  
usually called1 of  expansion4 ,these   
grades all begin at the same point on   
the cam1 but are of  different lengths1 
so that they begin to move the lever at 
the same time1  but differ in the time  
of returning it to its original         
position4    #bjj4 ,q4--,how is the     

degree of expansion changed8            
,a4--,the change of expansion is        
effected by moving the roller on to the 
desired grade2 which is done by slipping
 the lever carrying the roller  endways 
on the shaft or pin sustaining it4      
#bja4 ,q4--,are such cams applicable in 
all cases8    ,a4--,in engines moving at
 a high rate of speed the roller will be
 thrown  back from the cam by its       
momentum1 unless it be kept against it  
by means of  springs4 ,in some cases ,i 
have employed a spring formed of a great
 number of  discs of ,india rubber to   
keep the roller against the cam1 but a  
few brass  discs require to be          
interposed to prevent the ,india rubber 
discs from being  worn in the central   
hole4    #bjb4 ,q4--,may not the        
percussion incident to the action of a  
cam at a high  speed1 when the roller is
 not kept up to the face by springs1 be 
obviated  by giving a suitable          
configuration to the cam itself8        
,a4--,it may at all events be reduced4  

,the outline of the cam should be a     
parabola1 so that the valve may be set  
in motion precisely as a falling  body  
would be2 but it will1 nevertheless1 be 
necessary that the roller on  which the 
cam presses should be forced upward by a
 spring rather than by a  counterweight1
 as there will thus be less inertia or  
momentum in the mass  that has to be    
moved4    #bjc4 ,q4--,an additional     
slide valve is sometimes used for       
cutting off the  steam8    ,a4--,yes1   
very frequently2 and the slide valve is 
sometimes on the side or  back of the   
valve casing1 and sometimes on the back 
of the main or  distributing valve1 and 
moving with it4    #bjd4 ,q4--,are cams 
used in locomotive engines8    ,a4--,in 
locomotive engines the use of cams is   
inadmissible1 and other  expedients are 
employed1 of which those contrived by   
,stephenson and by  ,cabrey operate on  
the principle of accomplishing the      
requisite variations  of expansion by   
altering the throw of the slide valve4  

#bje4 ,q4--,what is ,stephenson's       
arrangement8    ,illustration3 ,fig4    
#ce4    ,a4--,stephenson connects the   
ends of the forward and backward        
eccentric  rods by a link with a curved 
slot in which a pin upon the end of the 
valve  rod works4 ,by moving this link  
so as to bring the forward eccentric rod
 in  the same line with the valve rod1  
the valve receives the motion due to    
that  eccentric2 whereas if the backward
 eccentric rod is brought in a line with
  the valve rod1 the valve gets the     
motion proper for reversing1 and if the 
link be so placed that the valve rod is 
midway between the two eccentric  rods1 
the valve will remain nearly stationary4
 ,this arrangement1 which is  now       
employed extensively1 is what is termed 
the link motion4 ,it is  represented in 
the annexed figure1 fig4 #ce1 where e is
 the valve rod1  which is attached by a 
pin to an open curved link susceptible  
of being  moved up and down by the      
bell-crank lever f'' f''1 supported on  

the  centre g1 and acting on the links  
f1 while the valve rod e remains in  the
 same horizontal plane2 d d' are the    
eccentric rods1 and the link is         
represented in its lowest position4 ,the
 dotted lines h' h'' show the  position 
of the eccentric rods when the link is  
in its highest position1  and l l' when 
in mid position4    #bjf4 ,q4--,what is 
,cabrey's arrangement8    ,a4--,mr4     
,cabrey makes his eccentric rod         
terminate in a pin which works  into a  
straight slotted lever1 furnished with  
jaws similar to the jaws on  the        
eccentric rods of locomotives4 ,by      
raising the pin of the eccentric rod  in
 this slot1 the travel of the valve will
 be varied1 and expansive action  will  
be the result4    #bjg4 ,q4--,what other
 forms of apparatus are there for       
working steam  expansively8             
,a4--,they are too numerous for         
description here1 but a few of them may 
be  enumerated4 ,fenton seeks to        
accomplish the desired object by        

introducing a  spiral feather on the    
crank axle1 by moving the eccentric     
laterally against  which the eccentric  
is partially turned round so as to cut  
off the steam at  a different part of   
the stroke4 ,dodds seeks to attain the  
same end by  corresponding mechanical   
arrangements4 ,farcot1 ,edwards1 and    
,lavagrian cut  off the steam by the    
application of a supplementary valve at 
the back of  the ordinary valve1 which  
supplementary valve is moved by tappets 
fixed to  the valve casing4 ,bodmer1 in 
#ahda1 and ,meyer1 in #ahdb1 employed   
two slides  or blocks fitted over       
apertures in the ordinary slide valve1  
and which  blocks were approximated or  
set apart by a right and left handed    
screw  passing through both4#a          
,hawthorn1 in #ahdc1 employed as an     
expansion valve  a species of frame     
lying on the ordinary cylinder face upon
 the outside of  the valve1 and working 
up against the steam side of the valve  
at each end  so as to cut off the steam4

 ,in the same year ,gonzenbach patented 
an  arrangement which consists of an    
additional slide valve and valve casing 
placed on the back of the ordinary slide
 valve casing1 and through this         
supplementary valve the steam must first
 pass4 ,this supplementary valve is     
worked by a double ended lever1 slotted 
at one end for the reception of a  pin  
on the valve link1 the position of which
 in the slot determines the  throw of   
the supplementary valve1 and the        
consequent degree of expansion4    #bjh4
 ,q4--,what is the arrangement of       
expansion valve used in the most        
approved modern engines8    ,a4--,in    
modern engines1 either marine or        
locomotive1 it is found that if  they   
are fitted with the link motion1 as they
 nearly all are1 a very good  expansive 
action can be obtained by giving a      
suitable adjustment to it1  without     
employing an expansion valve at all4    
,diagrams taken from engines  worked in 
this manner show a very excellent       

result1 and most of the modern  engines 
trust for their expansive working to the
 link motion and the  throttle valve4   
#a ,in #ahch ,i patented an arrangement 
of expansion valve1 consisting of two   
movable plates set upon the ordinary    
slide valve1 and which might be drawn   
together or asunder by means of a right 
and left handed screw passing  through  
both plates4 ,the valve spindle was     
hollow1 and a prolongation of  the screw
 passed up through it1 and was armed on 
the top with a small  wheel1 by means of
 which the plates might be adjusted     
while the engine was  at work4 ,in #ahci
 ,i fitted an expansion valve in a steam
 vessel1 consisting  of two plates1     
connected by a rod1 and moved by tappets
 up against the  steam edges of the     
valve4 ,in another steam vessel ,i      
fitted the same species  of valve1 but  
the motion was not derived from tappets1
 but from a moving  part of the engine1 
though at the moderate speed at which   
these engines  worked ,i found tappets  

to operate well and make little noise4  
,in #ahcg ,i  employed1 as an expansion 
valve1 a rectangular throttle valve1    
accurately  fitting a bored out seat1 in
 which it might be made to revolve1     
though it  did not revolve in working4  
,this valve was moved by a pin in a     
pinion1  making two revolutions for     
every revolution of the engine1 and the 
configuration of the seat determined the
 amount of the expansion4 ,in #ahee ,i  
have again used expansion valves of this
 construction in engines making one     
hundred revolutions per minute1 and with
 perfectly satisfactory results4--      
,j4,b4          ,,chapter ,,iv4         
,,modes ,,of ,,estimating ,,the ,,power 
,,and ,,performance ,,of ,,engines ,,and
 ,,boilers4      ,,horses ,,power4      
#bji4 ,q4--,what do you understand by a 
horse power8    ,a4--,an amount of      
mechanical force that will raise #cc1jjj
 lbs4 one foot  high in a minute4 ,this 
standard was adopted by ,mr4 ,watt1 as  
the average  force exerted by the       

strongest ,london horses2 the object of 
his  investigation being to enable him  
to determine the relation between the   
power of a certain size of engine and   
the power of a horse1 so that when it   
was desired to supersede the use of     
horses by the erection of an engine1 he 
might1 from the number of horses        
employed1 determine the size of engine  
that would be suitable for the work4    
#baj4 ,q4--,then when we talk of an     
engine of #bjj horse power1 it is meant 
that the impelling efficacy is equal to 
that of #bjj horses1 each lifting       
#cc1jjj lbs4 one foot high in a minute8 
,a4--,no1 not now2 such was the case in 
,watt's engines1 but the capacity of    
cylinder answerable to a horse power has
 been increased by most engineers  since
 his time1 and the pressure on the      
piston has been increased also1 so  that
 what is now called a #bjj horse power  
engine exerts1 almost in every  case1 a 
greater power than was exerted in       
,watt's time1 and a horse power1  in the

 popular sense of the term1 has become a
 mere conventional unit for  expressing 
a certain size of engine1 without       
reference to the power  exerted4        
#baa4 ,q4--,then1 each nominal horse    
power of a modern engine may raise much 
more than #cc1jjj lbs4 one foot high in 
a minute8    ,a4--,yes2 some raise      
#eb1jjj lbs41 others #fj1jjj lbs41 and  
others #ff1jjj  lbs41 one foot high in a
 minute by each nominal horse power4    
,some engines  indeed work as high as   
five times above the nominal power1 and 
therefore no  comparison can be made    
between the performances of different   
engines1  unless the power actually     
exerted be first discovered4    #bab4   
,q4--,how is the power actually exerted 
by engines ascertained8    ,a4--,by     
means of an instrument called the       
indicator1 which is a miniature         
cylinder and piston attached to the     
cylinder cover of the main engine1 and  
which indicates1 by the pressure exerted
 on a spring1 the amount of  pressure or

 vacuum existing within the cylinder4   
,from this pressure1  expressed in      
pounds per square inch1 deduct a pound  
and a half of pressure  for friction1   
the loss of power in working the air    
pump1 c42 multiply the  area of the     
piston in square inches by this residual
 pressure1 and by the  motion of the    
piston1 in feet per minute1 and divide  
by #cc1jjj2 the  quotient is the actual 
number of horses power of the engine4   
,the same  result is attained by        
squaring the diameter of the cylinder1  
multiplying by  the pressure per square 
inch1 as shown by the indicator1 less a 
pound and a  half1 and by the motion of 
the piston1 in feet per minute1 and     
dividing by  #db1jag4    #bac4 ,q4 ,how 
is the nominal power of an engine       
ascertained8    ,a4--,since the nominal 
power is a mere conventional expression1
 it is  clear that it must be determined
 by a merely conventional process4 ,the 
nominal power of ordinary condensing    
engines may be ascertained by the       

following rule3 multiply the square of  
the diameter of the cylinder in  inches1
 by the velocity of the piston in feet  
per minute1 and divide the  product by  
#f1jjj2 the quotient is the number of   
nominal horses power4 ,in  using this   
rule1 however1 it is necessary to adopt 
the speed of piston  prescribed by ,mr4 
,watt1 which varies with the length of  
the stroke4 ,the  speed of piston with a
 #b feet stroke is1 according to his    
system1 #afj per  minute2 with a #b ft4 
#f in4 stroke1 #agj2 #c ft41 #ahj2 #c   
ft4 #f in41 #ahi2 #d  ft41 #bjj2 #e ft41
 #bae2 #f ft41 #bbh2 #g ft41 #bde2 #h   
ft41 #bef ft4    #bad4 ,q4--,does not   
the speed of the piston increase with   
the length of the  stroke8    ,a4--,it  
does3 the speed of the piston varies    
nearly as the cube root of  the length  
of the stroke4    #bae4 ,q4--,and may   
not therefore some multiple of the cube 
root of the  length of the stroke be    
substituted for the velocity of the     
piston in  determining the nominal      

power8    ,a4--,the substitution is     
quite practicable1 and will accomplish  
some  simplification1 as the speed of   
piston proper for the different lengths 
of  stroke cannot always be remembered4 
,the rule for the nominal power of      
condensing engines when thus arranged1  
will be as follows3 multiply the  square
 of the diameter of the cylinder in     
inches by the cube root of the  stroke  
in feet1 and divide the product by #dg2 
the quotient is the number of  nominal  
horses power of the engine1 supposing it
 to be of the ordinary  condensing      
description4 ,this rule assumes the     
existence of a uniform  effective       
pressure upon the piston of #g lbs4 per 
square inch2 ,mr4 ,watt  estimated the  
effective pressure upon the piston of   
his #d horse power  engines at #f-h lbs4
 per square inch1 and the pressure      
increased slightly  with the power1 and 
became #f4id lbs4 per square inch in    
engines of #ajj  horse power2 but it    
appears to be more convenient to take a 

uniform  pressure of #g lbs4 for all    
powers4 ,small engines1 indeed1 are     
somewhat less  effective in proportion  
than large ones1 but the difference can 
be made up  by slightly increasing the  
pressure in the boiler2 and small       
boilers will  bear such an increase     
without inconvenience4    #baf4         
,q4--,how do you ascertain the power of 
high pressure engines8    ,a4--,the     
actual power is readily ascertained by  
the indicator1 by the same  process by  
which the actual power of low pressure  
engines is ascertained4  ,the friction  
of a locomotive engine when unloaded is 
found by experiment to  be about #a lb4 
per square inch on the surface of the   
pistons1 and the  additional friction   
caused by any additional resistance is  
estimated at  about 4#ad of that        
resistance2 but it will be a            
sufficiently near  approximation to the 
power consumed by friction in high      
pressure engines1  if we make a         
deduction of a pound and a half from the

 pressure on that  account1 as in the   
case of low pressure engines4 ,high     
pressure engines1 it  is true1 have no  
air pump to work2 but the deduction of a
 pound and a half  of pressure is       
relatively a much smaller one where the 
pressure is high1  than where it does   
not much exceed the pressure of the     
atmosphere4 ,the  rule1 therefore1 for  
the actual horse power of a high        
pressure engine will  stand thus3 square
 the diameter of the cylinder in inches1
 multiply by the  pressure of the steam 
in the cylinder per square inch less    
#a-a_/b lb41 and  by the speed of the   
piston in feet per minute1 and divide by
 #db1jag2 the  quotient is the actual   
horse power4    #bag4 ,q4--,but how do  
you ascertain the nominal horse power of
 high  pressure engines8    ,a4--,the   
nominal horse power of a high pressure  
engine has never been  defined2 but it  
should obviously hold the same relation 
to the actual power  as that which      
obtains in the case of condensing       

engines1 so that an engine  of a given  
nominal power may be capable of         
performing the same work1  whether high 
pressure or condensing4 ,this relation  
is maintained in the  following rule1   
which expresses the nominal horse power 
of high pressure  engines3 multiply the 
square of the diameter of the cylinder  
in inches by  the cube root of the      
length of stroke in feet1 and divide the
 product by  #ae4f4 ,this rule gives the
 nominal power of a high pressure engine
 three  times greater than that of a low
 pressure engine of the same dimensions2
  the average effective pressure being  
taken at #ba lbs4 per square inch       
instead of #g lbs41 and the speed of the
 piston in feet per minute being in     
both rules #abh times the cube root of  
the length of stroke4#a    #bah4        
,q4--,is #abh times the cube root of the
 stroke in feet per minute the  ordinary
 speed of all engines8                  
,a4--,locomotive engines travel at a    
quicker speed--an innovation brought    

about not by any process of scientific  
deduction1 but by the accidents and     
exigencies of railway transit4 ,most    
other engines1 however1 travel at about 
the speed of #abh times the cube root of
 the stroke in feet2 but some marine    
condensing engines of recent            
construction travel at as high a rate as
 #gjj  feet per minute4 ,to mitigate the
 shock of the air pump valves in cases  
in  which a high speed has been         
desirable1 as in the case of marine     
engines  employed to drive the screw    
propeller without intermediate gearing1 
,india  rubber discs1 resting on a      
perforated metal plate1 are now         
generally  adopted2 but the ,india      
rubber should be very thick1 and the    
guards employed  to keep the discs down 
should be of the same diameter as the   
discs  themselves4    #bai4 ,q4--,can   
you suggest any eligible method of      
enabling condensing  engines to work    
satisfactorily at a high rate of speed8 
,a4--,the most feasible way of enabling 

condensing engines to work              
satisfactorily at a high speed1 appears 
to lie in the application of  balance   
weights to the engine1 so as to balance 
the momentum of its moving  parts1 and  
the engine must also be made very strong
 and rigid4 ,it appears  to be advisable
 to perform the condensation partly in  
the air pump1 instead  of altogether in 
the condenser1 as a better vacuum and a 
superior action of  the air pump valves 
will thus be obtained4 ,engines         
constructed upon this  plan may be      
driven at four times the speed of common
 engines1 whereby an  engine of large   
power may be purchased for a very       
moderate price1 and be  capable of being
 put into a very small compass2 while   
the motion1 from  being more equable1   
will be better adapted for most purposes
 for which a  rotary motion is required4
 ,even for pumping mines and blowing    
iron  furnaces1 engines of this kind    
appear likely to come into use1 for they
 are  more suitable than other engines  

for driving the centrifugal pump1 which 
in  many cases appears likely to        
supersede other kinds of pumps for      
lifting  water2 and they are also       
conveniently applicable to the driving  
of fans1  which1 when so arranged that  
the air condensed by one fan is employed
 to  feed another1 and so on through a  
series of #d or #e1 have succeeded in   
forcing air into a furnace with a       
pressure of #b-a_/b lbs4 on the square  
inch1 and with a far steadier flow than 
can be obtained by a blast engine  with 
any conceivable kind of compensating    
apparatus4 ,they are equally  applicable
 if blast cylinders be employed4        
#bbj4 ,q4--,then1 if by this            
modification of the engine you enable it
 to  work at four times the speed1 you  
also enable it to exert four times the  
power8    ,a4--,yes2 always supposing it
 to be fully supplied with steam4 ,the  
nominal  power of this new species of   
engine can readily be ascertained by    
taking  into account the speed of the   

piston1 and this is taken into account  
by the  ,admiralty rule for power4      
#bba4 ,q4--,what is the ,admiralty rule 
for determining the power of an  engine8
    ,a4--,square the diameter of the    
cylinder in inches1 which multiply by   
the  speed of the piston in feet per    
minute1 and divide by #f1jjj2 the       
quotient  is the power of the engine by 
the ,admiralty rule4#b    #bbb4         
,q4--,the high speed engine does not    
require so heavy a fly wheel as  common 
engines8    ,a4--,no2 the fly wheel will
 be lighter1 both by virtue of its      
greater  velocity of rotation1 and      
because the impulse communicated by the 
piston is  less in amount and more      
frequently repeated1 so as to approach  
more nearly  to the condition of a      
uniform pressure4    #bbc4 ,q4--,can    
nominal be transformed into actual horse
 power8    ,a4--,no2 that is not        
possible in the case of common          
condensing engines4  ,the actual power  
exerted by an engine cannot be deduced  

from its nominal  power1 neither can the
 nominal power be deduced from the power
 actually  exerted1 or from anything    
else than the dimensions of the         
cylinder4 ,the  actual horse power being
 a dynamical unit1 and the nominal horse
 power a  measure of capacity of the    
cylinder1 are obviously incomparable    
things4    #bbd4 ,q4--,that is1 the     
nominal power is a commercial unit by   
which  engines are bought and sold1 and 
the actual power a scientific unit by   
which the quality of their performance  
is determined8    ,a4--,yes2 the nominal
 power is as much a commercial measure  
as a yard or a  bushel1 and is not a    
thing to be ascertained by any process  
of science1 but  to be fixed by         
authority in the same manner as other   
measures4 ,the actual  power1 on the    
contrary1 is a mechanical force or      
dynamical effort capable  of raising a  
given weight through a given distance in
 a given time1 and of  which the amount 
is ascertainable by scientific          

investigation4    #bbe4 ,q4--,is there  
any other measure of an actual horse    
power than #cc1jjj  lbs4 raised one foot
 high in the minute8    ,a4--,there     
cannot be any different measure1 but    
there are several  equivalent measures4 
,thus the evaporation of a cubic foot of
 water in the  hour1 or the expenditure 
of #cc cubic feet of low pressure steam 
per minute1  is reckoned equivalent to  
an actual horse power1 or #ebh cubic    
feet of water  raised one foot high in  
the minute involves the same result4    
#a ,tables of the horse power of both   
high and low pressure      engines are  
given in the ,key4    #b                
,example4--,what is the power of an     
engine of #db inches      diameter1     
#c-a_/b feet stroke1 and making #he     
strokes per minute8 ,the      speed of  
the piston will be #g 7the length of a  
double stroke7 x #he       #eie feet per
 minute4 ,now #db x #db  #a1gfd x #eie  
#a1jdi1ehj _/ #f1jjj       #age horses  
power4          ,,duty ,,of ,,engines   

,,and ,,boilers4    #bbf4 ,q4--,what is 
meant by the duty of a engine8          
,a4--,the work done in relation to the  
fuel consumed4    #bbg4 ,q4--,and how is
 the duty ascertained8    ,a4--,in      
ordinary mill or marine engines it can  
only be ascertained by the  indicator1  
as the load upon such engines is        
variable1 and cannot readily be         
determined2 but in the case of engines  
pumping water1 where the load is        
constant1 the number of strokes         
performed by the engine will represent  
the  work done1 and the amount of work  
done by a given quantity of coal        
represents the duty4 ,in ,cornwall the  
duty of an engine is expressed by the   
number of millions of pounds raised one 
foot high by a bushel1 or #id lbs4  of  
,welsh coal4 ,a bushel of ,newcastle    
coal will only weigh #hd ,lbs42 and in  
comparing the duty of a ,cornish engine 
with the performance of an engine in    
some locality where a different kind of 
coal is used1 it is necessary to  pay   

regard to such variations4    #bbh4     
,q4--,can you tell the duty of an engine
 when you know its consumption  of coal 
per horse power per hour8    ,a4--,yes1 
if the power given be the actual1 and   
not the nominal1 power4  ,divide #aff4cb
 by the number of pounds of coal        
consumed per actual horse  power per    
hour2 the quotient is the duty in       
millions of pounds4 ,if you  already    
have the duty in millions of pounds1 and
 wish to know the  equivalent           
consumption in pounds per actual horse  
power per hour1 divide  #aff4cb by the  
duty in millions of pounds2 the quotient
 is the consumption  per actual horse   
power per hour4 ,the duty of a          
locomotive engine is  expressed by the  
weight of coke it consumes in           
transporting a ton through  the distance
 of one mile upon a railway2 but this is
 a very imperfect  method of            
representing the duty1 as the tractive  
efficacy of a pound of  coke becomes    
less as the speed of the locomotive     

becomes greater2 and the  law of        
variation is not accurately known4      
#bbi4 ,q4--,what amount of power is     
generated in good engines of the        
ordinary kind by a given weight of coal8
    ,a4--,the duty of different kinds of
 engines varies very much1 and there    
are also great differences in the       
performance of different engines of the 
same class4 ,in ordinary rotative       
condensing engines of good construction1
  #aj lbs4 of coal per nominal horse    
power per hour is a common consumption2 
but such engines exert nearly twice     
their nominal power1 so that the        
consumption per actual horse power per  
hour may be taken at from #e to #f  lbs4
 ,engines working very expansively1     
however1 attain an economy much         
superior to this4 ,the average duty of  
the pumping engines in ,cornwall is     
about #fj1jjj1jjj lbs4 raised #a ft4    
high by a bushel of ,welsh coals1 which 
weighs #id lbs4 ,this is equivalent to a
 consumption of #c4a lbs4 of coal per   

actual horse power per hour2 but some   
engines reach a duty of above           
#ajj1jjj1jjj1 or #a4gd lbs4 of coal per 
actual horse power per hour4            
,locomotives consume from #h to #aj lbs4
 of coke in evaporating a cubic foot  of
 water1 and the evaporation of a cubic  
foot of water per hour may be set  down 
as representing an actual horse power in
 locomotives as well as in  condensing  
engines1 if expansion be not employed4  
,when the locomotive is  worked         
expansively1 however1 there is of course
 a less consumption of water  and fuel  
per horse power1 or per ton per mile1   
than when the full pressure  is used    
throughout the stroke2 and most         
locomotives now operate with as  much   
expansion as can be conveniently given  
by the slide valves4    #bcj4 ,q4--,but 
is not the evaporative power of         
locomotives affected  materially by the 
proportions of the boiler8    ,a4--,yes1
 but this may be said of all boilers2   
but in locomotive boilers1  perhaps1 the

 effect of any misproportion becomes    
more speedily manifest4 ,a  high        
temperature of the fire box is found to 
be conducive to economy of  fuel2 and   
this condition1 in its turn1 involves a 
small area of grate bars4  ,the heating 
surface of locomotive boilers should be 
about #hj square feet  for each square  
foot of grate bars1 and upon each foot  
of grate bars about  #a cwt4 of coke    
should be burnt in the hour4    #bca4   
,q4--,probably the heat is more rapidly 
absorbed when the temperature  of the   
furnace is high8    ,a4--,that seems to 
be the explanation4 ,the rapidity with  
which a hot body  imparts heat to a     
colder1 varies as the square of the     
difference of  temperature2 so that if  
the temperature of the furnace be very  
high1 the  larger part of the heat      
passes into the water at the furnace1   
thereby  leaving little to be           
transmitted by the tubes4 ,if1 on the   
contrary1 the  temperature of the       
furnace be low1 a large part of the heat

 will pass into  the tubes1 and more    
tube surface will be required to absorb 
it4 ,about #af  cubic feet of water     
should be evaporated by a locomotive    
boiler for each1  square foot of fire   
grate1 which1 with the proportion of    
heating surface  already mentioned1     
leaves #e square feet of heating surface
 to evaporate a  cubic foot of water in 
the hour4 ,this is only about half the  
amount of  surface usual in land and    
marine boilers per cubic foot           
evaporated1 and its  small amount is due
 altogether to the high temperature of  
the furnace1  which1 by the rapidity of 
transmission it causes1 is tantamount to
 an  additional amount of heating       
surface4    #bcb4 ,q4--,you have stated 
that the steam and vacuum gauges are    
generally  glass tubes1 up which mercury
 is forced by the steam or sucked by the
  vacuum8    ,a4--,vacuum gauges are    
very often of this construction1 but    
steam  gauges more frequently consist of
 a small iron tube1 bent like the letter

  ,u1 and into which mercury is poured4 
,the one end of this tube communicates  
with the boiler1 and the other end with 
the atmosphere2 and when the  pressure  
of the steam rises in the boiler1 the   
mercury is forced down in  the leg      
communicating with the boiler and rises 
in the other leg1 and the  difference of
 level in the legs denotes the pressure 
of the steam4 ,in this  gauge a rise of 
the mercury one inch in the one leg     
involves a difference  of the level     
between the two legs of two inches1 and 
an inch of rise is1  therefore1         
equivalent to two inches of mercury1 or 
a pound of pressure4 ,a  small float of 
wood is placed in the open leg to show  
the rise or fall of  the mercury1 and   
this leg is surmounted by a brass scale1
 graduated in  inches1 to the marks of  
which the float points4    #bcc4        
,q4--,what other kinds of steam and     
vacuum gauges are there8    ,a4--,there 
are many other kinds2 but probably      
,bourdon's gauges are now in  more      

extended use than1 any other1 and their 
operation has been found to be          
satisfactory in practice4 ,the principle
 of their action may be explained to    
be1 that a thin elliptical metal tube1  
if bent into a ring1 will seek to  coil 
or uncoil itself if subjected to        
external or internal pressure1 and to   
an extent proportional to the pressure  
applied4 ,the end of the tube is        
sharpened into an index1 and moves to an
 extent corresponding to the  pressure  
applied to the tube2 but in the more    
recent forms of this  apparatus1 a dial 
and a hand1 like those of a clock1 are  
employed1 and the  hand is moved round  
by a toothed sector connected to the    
tube1 and which  sector acts on a pinion
 attached to the hand4 ,mr4 ,shank1 of  
,paisley1 has  lately introduced a form 
of steam gauge like a thermometer1 with 
a  flattened bulb2 and the pressure of  
the steam1 by compressing the bulb1     
causes the mercury to rise to a point   
proportional to the pressure applied4   

,,the ,,indicator4    #bcd4 ,q4--,you   
have already stated that the actual     
power of an engine is  ascertained by an
 instrument called the indicator1 which 
consists of a  small cylinder with a    
piston moving against a spring1 and     
compressing it to  an extent answerable 
to the pressure of the steam4 ,will you 
explain further  the structure and mode 
of using that instrument8               
,illustration3 ,fig4 #cf    ,a4--,the   
structure of the common form of         
indicator will be most readily          
apprehended by a reference to fig4 #cf1 
which is a ,mc,naught's indicator4      
,upon a movable barrel ,a1 a piece of   
paper is wound1 the ends of which are   
secured by the slight brass clamps shown
 in the drawing4 ,the barrel is         
supported by the bracket b1 proceeding  
from the body of the indicator1  and at 
the bottom of the barrel a watch spring 
is coiled with one end  attached to the 
barrel and the other end to the bracket1
 so that when the  barrel is drawn round

 by a string wound upon its lower end   
like a roller  blind1 the spring returns
 the barrel to its original position1   
when the  string is relaxed4 ,the string
 is attached to some suitable part of   
the  engine1 and at every stroke the    
string is drawn out1 turning round the  
barrel1 and the barrel is returned again
 by the spring on the return  stroke4   
#bce4 ,q--,but in what way can these    
reciprocations of the barrel determine  
the power of the engine8    ,a4--,they  
do not determine it of themselves1 but  
are only part of the  operation4 ,in the
 inside of the cylinder c there is a    
small piston moving  steam tight in a   
cylinder of which d is the piston rod1  
and e a spiral  spring of steel1 which  
the piston1 when forced upwards by the  
steam or  sucked downwards by the       
vacuum1 either compresses or extends2 f 
is a cock  attached to the cylinder of  
the indicator1 and which is screwed into
 the  cylinder cover4 ,it is obvious    
that1 so soon as this cock is opened1   

the  piston will be forced up when the  
space above the piston of the engine is 
opened to the boiler1 and sucked down   
when that space is opened to the        
condenser--in each case to an extent    
proportionate to the pressure of the    
steam or the perfection of the vacuum1  
the top of the piston c being open  to  
the atmosphere4 ,a pencil1 p1 with a    
knife hinge1 is inserted into the       
piston rod1 at e1 and the point of the  
pencil bears upon the surface of  the   
paper wound upon the drum ,a4 ,if the   
drum ,a did not revolve1 this pencil    
would merely trace on the paper a       
vertical line2 but as the drum ,a moves 
round and back again every stroke of the
 engine1 and as the pencil moves up  and
 down again every stroke of the engine1 
the combined movements trace  upon the  
paper a species of rectangle1 which is  
called an indicator  diagram2 and the   
nature of this diagram determines the   
nature of the  engine's performance4    
#bcf4 ,q4--,how does it do this8        

,a4--,it is clear that if the pencil was
 moved up instantaneously to the  top of
 its stroke1 and was also moved down    
instantaneously to the bottom of  its   
stroke1 and if it remained without      
fluctuation while at the top and        
bottom1 the figure described by the     
pencil would be a perfect rectangle1 of 
which the vertical height would         
represent the total pressure of the     
steam  and vacuum1 and therefore the    
total pressure urging the piston of the 
engine4 ,but in practice the pencil will
 neither rise nor fall  instantaneously1
 nor will it remain at a uniform height 
throughout the  stroke4 ,if the steam be
 worked expansively the pressure will   
begin to fall  so soon as the steam is  
cut off2 and at the end of the stroke1  
when the  steam comes to be discharged1 
the subsidence of pressure will not be  
instantaneous1 but will occupy an       
appreciable time4 ,it is clear1         
therefore1  that in no engine can the   
diagram described by an indicator be a  

complete  rectangle2 but the more nearly
 it approaches to a rectangle1 the      
larger  will be the power produced at   
every stroke with any given pressure1   
and the  area of the space included     
within the diagram will in every case   
accurately  represent the power exerted 
by the engine during that stroke4       
#bcg4 ,q4--,and how is this area        
ascertained8    ,a4--,it may be         
ascertained in various ways2 but the    
usual mode is to take  the vertical     
height of the diagram at a number of    
equidistant points on a  base line1 and 
then to take the mean of these several  
heights as  representative of the mean  
pressure actually urging the piston4    
,now if you  have the pressure on the   
piston per square inch1 and if you know 
the number  of square inches in its     
area1 and the velocity with which it    
moves in feet  per minute1 you have     
obviously the dynamical effort of the   
engine1 or1 in  other words1 its actual 
power4    #bch4 ,q4--,how is the base   

line you have referred to obtained8     
,a4--,in proceeding to take an indicator
 diagram1 the first thing to be  done is
 to allow the barrel to make two or     
three reciprocations with the  pencil   
resting against it1 before opening the  
cock attached to the  cylinder4 ,there  
will thus be traced a horizontal line1  
which is called the  atmospheric line1  
and in condensing engines1 a part of the
 diagram will  be above and a part of it
 below this line2 whereas1 in high      
pressure  engines the whole of the      
diagram will be above this line4 ,upon  
this line  the vertical ordinates may be
 set off at equal distances1 or upon any
 base  line parallel to it2 but the     
usual course is to erect the ordinates  
on the  atmospheric line4    #bci4      
,q4--,will you give an example of an    
indicator diagram8    ,illustration3    
,fig4 #cg    ,a4--,fig4 #cg is an       
indicator diagram taken from a low      
pressure engine1 and  the waving line a 
b c1 forming a sort of irregular        

parallelogram1 is that  which is        
described by the pencil4 ,the           
atmospheric line is represented by  the 
line o o4 ,the scale at the side shows  
the pressure of the steam1 which  in    
this engine rose to about #i lbs4 per   
square inch1 and the vacuum fell to  #aa
 lbs4 ,the steam begins to be cut off   
when1 about one-fourth of the stroke    
has been performed1 and the pressure    
consequently falls4    #bdj4 ,q4--,is   
this species of indicator which you have
 just described  applicable to          
locomotive engines8    ,a4--,it is no   
doubt applicable under suitable         
conditions2 but another  species of     
indicator has been applied by ,mr4      
,gooch to locomotive engines1  which    
presents several features of superiority
 for such a purpose4    ,this indicator 
has its cylinder placed horizontally2   
and its piston  compresses two          
elliptical springs2 a slide valve is    
substituted for a cock1  to open or     
close the communication with the engine4

 ,the top of the piston  rod of this    
indicator is connected to the short arm 
of a smaller lever1 to  the longer arm  
of which the pencil is attached1 and the
 pencil has thus a  considerably larger 
amount of motion than the piston2 but it
 moves in the  arc of a circle instead  
of in a straight line4 ,the pencil marks
 on a web of  paper1 which is unwound   
from one drum and wound on to another1  
so that a  succession of diagrams are   
taken without the necessity of any      
intermediate  manipulation4    #bda4    
,q4--,these diagrams being taken with a 
pencil moving in an arc1 will  be of a  
distorted form8    ,a4--,they will not  
be of the usual form1 but they may be   
easily translated  into the usual form4 
,it is undoubtedly preferable that the  
indicator should  act immediately in the
 production of the final form of        
diagram4          ,,dynamometer1        
,,gauges1 ,,and ,,cataract4      #bdb4  
,q4--,what other gauges or instruments  
are there for telling the  state1 or    

regulating the power of an engine8      
,a4--,there is the counter for telling  
the number of strokes the engine  makes1
 and the dynamometer for ascertaining   
the tractive power of steam  vessels or 
locomotives2 then there are the gauge   
cocks1 and glass tubes1 or  floats1 for 
telling the height of water in the      
boiler2 and in pumping  engines there is
 the cataract for regulating the speed  
of the engine4    #bdc4 ,q4--,will you  
describe the mechanism of the counter8  
,a4--,the counter consists of a train of
 wheel work1 so contrived that by  every
 stroke of the engine an index hand is  
moved forward a certain space1  whereby 
the number of strokes made by the engine
 in any given time is  accurately       
recorded4 ,in most cases the motion is  
communicated by means of a              
detent1--attached to some reciprocating 
part of the engine1--to a ratchet  wheel
 which gives motion to the other wheels 
in its slow revolution2 but it  is      
preferable to derive the motion from    

some revolving part of the engine  by   
means of an endless screw1 as where the 
ratchet is used the detent will         
sometimes fail to carry it round the    
proper distance4 ,in the counter        
contrived by ,mr4 ,adie1 an endless     
screw works into the rim of two small   
wheels situated on the same axis1 but   
one wheel having a tooth more than  the 
other1 whereby a differential motion is 
obtained2 and the difference in  the    
velocity of the two wheels1 or their    
motion upon one another1 expresses  the 
number of strokes performed4 ,the       
endless screw is attached to some       
revolving part of the engine1 whereby a 
rotatory motion is imparted to it2  and 
the wheels into which the screws work   
hang down from it like a  pendulum1 and 
are kept stationary by the action of    
gravity4    #bdd4 ,q4--,what is the     
nature of the dynamometer8    ,a4--,the 
dynamometer employed for ascertaining   
the traction upon railways  consists of 
two flat springs joined together at the 

ends by links1 and the  amount of       
separation of the springs at the centre 
indicates1 by means of a  suitable hand 
and dial1 the force of traction4 ,a     
cylinder of oil1 with a  small hole     
through its piston1 is sometimes added  
to this instrument to  prevent sudden   
fluctuations4 ,in screw vessels the     
forward thrust of the  screw is measured
 by a dynamometer constructed on the    
principle of a  weighing machine1 in    
which a small spring pressure at the    
index will  balance a very great        
pressure where the thrust is employed2  
and in each  case the variations of     
pressure are recorded by a pencil on a  
sheet of  paper1 carried forward by     
suitable mechanism1 whereby the mean    
thrust is  easily ascertained4 ,the     
tractive force of paddle wheel steamers 
is  ascertained by a dynamometer fixed  
on shore1 to which the floating vessel  
is attached by a rope4 ,sometimes the   
power of an engine is ascertained by a  
friction break dynamometer applied to   

the shaft4    #cde4 ,q4--,what will     
determine the amount of thrust shown by 
the  dynamometer8    ,a4--,in           
locomotives and in paddle steamers it   
will be determined by the  force turning
 the wheels1 and by the smallness of the
 diameter of the  wheels2 for with small
 wheels the thrust will be greater than 
with large  wheels4 ,in screw vessels   
the thrust will be determined by the    
force turning  round the screw1 and by  
the smallness of the screw's pitch2 for 
with any  given force of torsion a fine 
pitch of screw will give a greater      
thrust  than a coarse pitch of screw1   
just as is the case when a screw works  
in a  solid nut4    #bdf4 ,q4--,will you
 explain the use of the glass gauges    
affixed to the  boiler8    ,a4--,the    
glass gauges are tubes affixed to the   
fronts of boilers1 by the  aid of which 
the height of the water within the      
boilers is readily  ascertainable1 for  
the water will stand at the same height 
in the tube as  in the boiler1 with     

which there is a communication          
maintained both at the  top and bottom  
of the tube by suitable stopcocks4 ,the 
cocks connecting the  glass tube with   
the boiler should always be so          
constructed that the tube  may be blown 
through with the steam1 to clear it of  
any internal concretion  that may impair
 its transparency2 and the construction 
of the sockets in  which the tube is    
inserted should be such1 that1 even when
 there is steam  in the boiler1 a broken
 tube may be replaced with facility4    
#bdg4 ,q4--,what then are the gauge     
cocks8    ,a4--,the gauge cocks are     
cocks penetrating the boiler at         
different  heights1 and which1 when     
opened1 tell whether it is water or     
steam that  exists at the level at which
 they are respectively inserted4 ,it is 
unsafe  to trust to the glass gauges    
altogether as a means of ascertaining   
the  water level1 as sometimes they     
become choked1 and it is necessary1     
therefore1 to have gauge cocks in       

addition2 but if the boiler be short of 
steam1 and a partial vacuum be produced 
within it1 the glass gauges become  of  
essential service1 as the gauge cocks   
will not operate in such a case1  for   
though opened1 instead of steam and     
water escaping from them1 the air  will 
rush into the boiler4 ,it is expedient  
to carry a pipe from the lower  end of  
the glass tube downward into the water  
of the boiler1 and a pipe  from the     
upper end upward into the steam in the  
boiler1 so as to prevent  the water from
 boiling down through the tube1 as it   
might otherwise do1 and  prevent the    
level of the water from being           
ascertainable4 ,the average level  of   
water in the boiler should be above the 
centre of the tube2 and the  lowest of  
the gauge cocks should always run water1
 and the highest should  always blow    
steam4    #bdh4 ,q4--,is not a float    
sometimes employed to indicate the level
 of the  water in the boiler8    ,a4--,a
 float for telling the height of water  

in the boiler is employed  only in the  
case of land boilers1 and its action is 
like that of a buoy  floating on the    
surface1 which1 by means of a light rod 
passing vertically  through the boiler1 
shows at what height the water stands4  
,the float is  usually formed of stone  
or iron1 and is so counterbalanced as to
 make its  operation the same as if it  
were a buoy of timber2 and it is        
generally put  in connection with the   
feed valve1 so that in proportion as the
 float  rises1 the supply of feed water 
is diminished4 ,the feed water in land  
boilers is admitted from a small open   
cistern1 situated at the top of an      
upright or stand pipe set upon the      
boiler1 and in which there is a column  
of water sufficiently high to balance   
the pressure of the steam4    #bdi4     
,q4--,what is the cataract which is     
employed to regulate the speed of       
pumping engines8    ,illustration3 ,fig4
 #ch4     ,a4--,the cataract consists of
 a small pump-plunger b and barrel1 set 

in  a cistern of water1 the barrel being
 furnished on the one side with a       
valve1 c1 opening inwards1 through which
 the water obtains admission to  the    
pump chamber from the cistern1 and on   
the other by a plug1 d1 through  which1 
if the plunger be forced down1 the water
 must pass out of the pump  chamber4    
,the engine in the upward stroke of the 
piston1 which is  accomplished by the   
preponderance of weight at the pump end 
of the beam1  raises up the plunger of  
the cataract by means of a small        
rod1--the water  entering readily       
through the valve already referred to2  
and when the engine  reaches the top of 
the stroke1 it liberates the rod by     
which the plunger  has been drawn up1   
and the plunger then descends by        
gravity1 forcing out  the water through 
the cock1 the orifice of which has      
previously been  adjusted1 and the      
plunger in its descent opens the        
injection valve1 which  causes the      
engine to make a stroke4    #bej4       

,q4--,suppose the cock of the cataract  
be shut8    ,a4--,if the cock of the    
cataract be shut1 it is clear that the  
plunger  cannot descend at all1 and as  
in that case the injection valve cannot 
be  opened1 the engine must stand still2
 but if the cock be slightly opened1    
the plunger will descend slowly1 the    
injection valve will slowly open1 and   
the engine will make a gradual stroke as
 it obtains the water necessary for     
condensation4 ,the extent to which the  
cock is open1 therefore1 will  regulate 
the speed with which the engine works2  
so that1 by the use of the  cataract1   
the speed of the engine may be varied to
 suit the variations in  the quantity of
 water requiring to be lifted from the  
mine4 ,in some cases  an air cylinder1  
and in other cases an oil cylinder1 is  
employed instead of  the apparatus just 
described2 but the principle on which   
the whole of these  contrivances operate
 is identical1 and the only difference  
is in the  detail4    #bea4 ,q4--,you   

have now shown that the performance of  
an engine is  determinable by the       
indicator2 but how do you determine the 
power of the  boiler8    ,a4--,by the   
quantity of water it evaporates4 ,there 
is1 however1 no very  convenient        
instrument for determining the quantity 
of water supplied to a  boiler1 and the 
consequence is that this element is     
seldom ascertained4          ,,chapter  
,v4      ,,proportion ,,of ,,boilers4   
,,heating ,,and ,,fire ,,grate          
,,surface4    #beb4 ,q4--,what are the  
considerations which must chiefly be    
attended to in  settling the proportions
 of boilers8    ,a4--,in the first place
 there must be sufficient grate surface 
to enable  the quantity of coal         
requisite for the production of the     
steam to be  conveniently burnt1 taking 
into account the intensity of the       
draught2 and  in the next place there   
must be a sufficient flue surface       
readily to absorb  the heat thus        
produced1 so that there may be no       

needless waste of heat by  the chimney4 
,the flues1 moreover1 must have such an 
area1 and the chimney  must be of such  
dimensions1 as will enable a suitable   
draught through the  fire to be         
maintained2 and finally the boiler must 
be made capable of  containing such     
supplies of water and steam as will     
obviate inconvenient  fluctuations in   
the water level1 and abate the risk of  
water being carried  over into the      
engine with the steam4 ,with all these  
conditions the boiler  must be as light 
and compact as possible1 and must be so 
contrived as to be  capable of being    
cleaned and repaired with facility4     
#bec4 ,q4--,supposing1 then1 that you   
had to proportion a boiler1 which       
should be capable of supplying steam    
sufficient to propel a steam vessel or  
railway train at a given speed1 or to   
perform any other given work1 how  would
 you proceed8    ,a4--,i would first    
ascertain the resistance which had to be
 overcome1 and  the velocity with which 

it was necessary to overcome it4 ,i     
should then be  in a position to know   
what pressure and volume of steam were  
required to  overcome the resistance at 
the prescribed rate of motion2 and1     
finally1 ,i  should allow a sufficient  
heating and fire grate surface in the   
boiler  according to the kind of boiler 
it was1 to furnish the requisite        
quantity  of steam1 or1 in other words1 
to evaporate the requisite quantity of  
water4    #bed4 ,q4--will you state the 
amount of heating surface and grate     
surface  necessary to evaporate a given 
quantity of water8    ,a4--,the number  
of square feet of heating or flue       
surface1 required to  evaporate a cubic 
foot of water per hour1 is about #gj    
square feet in  ,cornish boilers1 #h to 
#aa square feet in land and marine      
boilers1 and #e or #f  square feet in   
locomotive boilers4 ,the number of      
square feet of heating  surface per     
square foot of fire grate1 is from #ac  
to #ae square feet in  wagon boilers2   

about #dj square feet in ,cornish       
boilers2 and from #ej to #ij  square    
feet in locomotive boilers4 ,about #hj  
square feet in locomotives is a  very   
good proportion4    #bee4 ,q4--,what is 
the heating surface of boilers per horse
 power8    ,a4--,about #i square feet of
 flue and furnace surface per horse     
power is  the usual proportion in wagon 
boilers1 reckoning the total surface as 
effective surface1 if the boilers be of 
a considerable size2 but in the  case of
 small boilers the proportion is larger4
 ,the total heating surface  of a two   
horse power wagon boiler is1 according  
to ,boulton and ,watt's  proportions1   
#cj square feet1 or #ae ft4 per horse   
power2 whereas1 in the  case of a #de   
horse power boiler the total heating    
surface is #dch square  feet1 or #i4f   
ft4 per horse power4 ,in marine boilers 
nearly the same  proportions obtain4    
,the original boilers of the ,great     
,western steamer1 by  ,messrs4          
,maudslay1 were proportioned with about 

#aj square feet of flue and  furnace    
surface per horse power1 reckoning the  
total amount as effective2  but in the  
boilers of the ,retribution1 by the same
 makers1 but of larger  size1 a somewhat
 smaller proportion of heating surface  
was adopted4 ,boulton  and ,watt have   
found that in their marine flue boilers1
 #i square feet of  flue and furnace    
surface are requisite to boil off a     
cubic foot of water  per hour1 which is 
the proportion of heating surface that  
is allowed in  their land boilers per   
horse power2 but inasmuch as in most    
modern engines1  and especially in      
marine engines1 the nominal considerably
 exceeds the  actual power1 they allow  
#aa or #ab square feet of heating       
surface per  nominal horse power in     
their marine boilers1 and they reckon as
 effective  heating surface the tops of 
the flues1 and the whole of the sides of
 the  flues1 but hot the bottoms4 ,for  
their land engines they still retain    
,mr4  ,watt's standard of power1 which  

makes the actual and the nominal power  
identical2 and an actual horse power is 
the equivalent of a cubic foot of  water
 raised into steam every hour4    #bef4 
,q4--,what is the proper proportion of  
fire grate per horse power8             
,a4--,boulton and ,watt allow #j4fd of a
 square foot area of grate bars per     
nominal horse power in their marine     
boilers1 and a good effect arises from  
this proportion2 but sometimes so large 
an area of fire grate cannot be         
conveniently got1 and the proportion of 
half a square foot per horse power1     
which is the proportion adopted in the  
original boiler of the ,great  ,western1
 seems to answer very well in engines   
working with a moderate  pressure1 and  
with some expansion2 and this proportion
 is now very widely  adopted4 ,with this
 allowance1 there will be #bb to #bd    
square feet of heating  surface per     
square foot of fire grate2 and if the   
consumption of fuel be  taken at #f lbs4
 per nominal horse power per hour1 there

 will be about #ab  lbs4 of coal        
consumed per hour on each square foot of
 grate4 ,the furnaces  should not be    
more than #f ft4 long1 as1 if much      
longer than this1 it will  be impossible
 to work them properly for any          
considerable length of time1 as  they   
will become choked with clinker at the  
back ends4    #beg4 ,q4--,what quantity 
of fuel is usually consumed per hour on 
each  square foot of fire grate8        
,a4--,the quantity of fuel burned on    
each square foot of fire grate per      
hour1 varies very much in different     
boilers2 in wagon boilers it is from #aj
  to #ac lbs42 in ,cornish boilers from 
#c-a_/b to #d lbs42 and in locomotive   
boilers from #hj to #aej lbs42 but about
 #a cwt4 per hour is a good proportion  
in locomotives1 as has been already     
explained4        ,,calorimeter ,,and   
,,vent4    #beh4 ,q4--,in what manner   
are the proper sectional area and the   
proper  capacity of the flue of a boiler
 determined8    ,a4--,the proper        

collective area for the escape of the   
smoke and flame over  the furnace       
bridges in marine boilers is #ai square 
inches per nominal horse  power1        
according to ,boulton and ,watt's       
practice1 and for the sectional area  of
 the flue they allow #ah square inches  
per horse power4 ,the sectional area  of
 the flue in square inches is what is   
termed the calorimeter of the  boiler1  
and the calorimeter divided by the      
length of the flue in feet is  what is  
termed the vent4 ,in marine flue boilers
 of good construction the  vent varies  
between the limits of #bj and #be1      
according to the size of the  boiler and
 other circumstances--the largest       
boilers having generally the  largest   
vents2 and the calorimeter divided by   
the vent will give the length  of the   
flue in feet4 ,the flues of all flue    
boilers diminish in their  calorimeter  
as they approach the chimney1 as the    
smoke contracts in its  volume in       
proportion as it parts with its heat4   

#bei4 ,q4--,is the method of determining
 the dimensions of a boiler flue1 by  a 
reference to its vent and calorimeter1  
the method generally pursued8           
,a4--,it is ,boulton and ,watt's method2
 but some very satisfactory boilers     
have been made by allowing a proportion 
of #j4f of a square foot of fire  grate 
per nominal horse power1 and making the 
sectional area of the flue at  the      
largest part #a_/gth of the area of fire
 grate1 and at the smallest part1  where
 it enters the chimney1 #a_/aath of the 
area of the fire grate4 ,these          
proportions are retained whether the    
boiler is flue or tubular1 and from #ad 
to #af square feet of tube surface is   
allowed per nominal horse power4        
#bfj4 ,q4--,are the proportions of vent 
and calorimeter1 taken by ,boulton  and 
,watt for marine flue boilers1          
applicable also to wagon and tubular    
boilers8    ,a4--,no4 ,in wagon and     
tubular boilers very different          
proportions prevail1  yet the           

proportions of every kind of boiler are 
determinable on the same  general       
principle4 ,in wagon boilers the        
proportion of the perimeter of the  flue
 which is effective as heating surface1 
is to the total perimeter as #a  to #c1 
or1 in some cases as #a to #b4e2 and    
with any given area of flue1  therefore1
 the length of the flue must be from #c 
to #b4e times greater than  would be    
necessary if the total surface were     
effective1 else the requisite  quantity 
of heating surface will not be obtained4
 ,if1 then1 the vent be the             
calorimeter1 divided by the length1 and 
the length be made #c or #b4e times     
greater1 the vent must become #c or #b4e
 times less2 and in wagon boilers       
accordingly1 the vent varies from #h to 
#aa instead of from #ba to #be1 as in   
the case of marine flue boilers4 ,in    
tubular marine boilers the calorimeter  
is usually made only about half the     
amount allowed by ,boulton and ,watt for
  marine flue boilers1 or1 in other     

words1 the collective sectional area of 
the tubes1 for the transmission of the  
smoke1 is from #h to #i square inches   
per nominal horse power4 ,it is better1 
however1 to make the sectional area     
larger than this1 and to work the boiler
 with the damper sufficiently  closed to
 prevent the smoke and flame from       
rushing exclusively through a  few of   
the tubes4    #bfa4 ,q4--,what are the  
ordinary dimensions of the flue in wagon
 boilers8    ,a4--,in ,boulton and      
,watt's #de horse wagon boiler the area 
of flue is #ah  square inches per horse 
power1 but the area per horse power     
increases very  rapidly as the size of  
the boiler becomes less1 and amounts to 
about #hj  square inches per horse power
 in a boiler of #b horse power4 ,some   
such  increase is obviously inevitable1 
if a similar form of flue be retained in
  the larger and smaller powers1 and at 
the same time the elongation of the     
flue in the same proportion as the      
increase of any other dimension is      

prevented2 but in the smaller class of  
wagon boilers the consideration of      
facility of cleaning the flues is also  
operative in inducing a large           
proportion of sectional area4 ,boulton  
and ,watt's #b horse power wagon boiler 
has #cj square feet of surface1 and the 
flue is #ah inches high above the  level
 of the boiler bottom1 by #i inches     
wide2 while their #ab horse wagon       
boiler has #aah square feet of heating  
surface1 and the dimensions of the  flue
 similarly measured are #cf inches by   
#ac inches4 ,the width of the  smaller  
flue1 if similarly proportioned to the  
larger one1 would be #f-a_/b  inches1   
instead of #i inches1 and1 by assuming  
this dimension1 we should  have the same
 proportion of sectional area per square
 foot of heating  surface in both       
boilers4 ,the length of flue in the #b  
horse boiler is #ai4e  ft41 and in the  
#ab horse boiler #ci ft41 so that the   
length and height of  the flue are      
increased in the same proportion4       

#bfb4 ,q4--,will you give an example of 
the proportions of a flue1 in the  case 
of a marine boiler8    ,a4--,the ,nile  
steamer1 with engines of #aaj horse     
power by ,boulton and  ,watt1 is        
supplied with steam by two boilers1     
which are1 therefore1 of #ee  horses    
power each4 ,the height of the flue     
winding within the boiler is #fj        
inches1 and its mean width #af-a_/b     
inches1 making a sectional area or      
calorimeter of #iij square inches1 or   
#ah square inches per horse power of    
the boiler4 ,the length of the flue is  
#ci ft41 making the vent #be1 which is  
the vent proper for large boilers4 ,in  
the ,dee and ,solway steamers1 by ,scott
  and ,sinclair1 the calorimeter is only
 #i4gb square inches per horse power2   
in the ,eagle1 by ,caird1 #aa4i2 in the 
,thames and ,medway1 by ,maudslay1      
#aa4cd1  and in a great number of other 
cases it does not rise above #ab square 
inches per horse power2 but the engines 
of most of these vessels are  intended  

to operate to a certain extent          
expansively1 and the boilers are  less  
powerful in evaporating efficacy on that
 account4    #bfc4 ,q4--,then the chief 
difference in the proportions           
established by  ,boulton and ,watt1 and 
those followed by the other             
manufacturers you have  mentioned is1   
that ,boulton and ,watt set a more      
powerful boiler to do the  same work8   
,a4--,that is the main difference4 ,the 
proportion which one part of the  boiler
 bears to another part is very similar  
in the cases cited1 but the  proportion 
of boiler relatively to the size of the 
engine varies very  materially4 ,thus   
the calorimeter of each boiler of the   
,dee and ,solway is  #abif square       
inches2 of the ,eagle1 #aedh square     
inches2 and of the ,thames and  ,medway1
 #aacd square inches2 and the length of 
flue is #eg1 #fj1 and #eb ft4 in  the   
boilers respectively1 which makes the   
respective vents #bb-a_/b1 #be1 and     
#ba4 ,taking then the boiler of the     

,eagle for comparison with the boiler of
  the ,nile1 as it has the same vent1 it
 will be seen that the proportions of   
the two are almost identical1 for #iij  
is to #aedh as #ci is to #fj1 nearly2   
but ,messrs4 ,boulton and ,watt would   
not have set a boiler like that of the  
,eagle to do so much work4    #bfd4     
,q4--,then the evaporating power of the 
boiler varies as the sectional  area of 
the flue8    ,a4--,the evaporating power
 varies as the square root of the area  
of the  flue1 if the length of the flue 
remain the same2 but it varies as the   
area  simply1 if the length of the flue 
be increased in the same proportion as  
its other dimensions4 ,the evaporating  
power of a boiler is referable to the   
amount of its heating surface1 and the  
amount of heating surface in any  flue  
or tube is proportional to the product  
of the length of the tube and  the      
square root of its sectional area1      
multiplied by a certain quantity  that  
is constant for each particular form4   

,but in similar tubes the length  is    
proportional to the square root of the  
sectional area2 therefore1 in  similar  
tubes1 the amount of heating surface is 
proportional to the  sectional area4 ,on
 this area also depends the quantity of 
hot air passing  through the flue1      
supposing the intensity of the draught  
to remain  unaffected1 and the quantity 
of hot air or smoke passing through the 
flue  should vary in the same ratio as  
the quantity of surface4    #bfe4       
,q4--,a boiler1 therefore1 to exert four
 times the power1 should have  four     
times the extent of heating surface1 and
 four times the sectional area  of flue 
for the transmission of the smoke8      
,a4--,yes2 and if the same form of flue 
is to be retained1 it should be of      
twice the diameter and twice the length2
 or twice the height and width if       
rectangular1 and twice the length4 ,as  
then the diameter or square root of  the
 area increases in the same ratio as the
 length1 the square root of the  area   

divided by the length ought to be a     
constant quantity in each type of       
boiler1 in order that the same          
proportions of flue may be retained2 and
 in  wagon boilers without an internal  
flue1 the height in inches of the flue  
encircling the boiler divided by the    
length of the flue in feet will be #a   
very nearly4 ,instead of the square root
 of the area1 the effective  perimeter1 
or outline of that part of the cross    
section of the flue which  is effective 
in generating steam1 may be taken2 and  
the effective perimeter  divided by the 
length ought to be a constant quantity  
in similar forms of  flues and with the 
same velocity of draught1 whatever the  
size of the flue  may be4    #bff4      
,q4--,will this proportion alter if the 
form of the flue be changed8    ,a4--,it
 is clear1 that with any given area of  
flue1 to increase the  perimeter by     
adopting a different shape is tantamount
 to a diminution of  the length of the  
flue2 and1 if the perimeter be          

diminished1 the length of  the flue must
 at the same time be increased1 else it 
will be impossible to  obtain the       
necessary amount of heating surface4 ,in
 ,boulton and ,watt's wagon  boilers1   
the sectional area of the flue in square
 inches per square foot of  heating     
surface is #e4d in the two horse boiler2
 in the three horse it is  #d4gd2 in the
 four horse1 #d4ce2 six horse1 #c4ge2   
eight horse1 #d4cc2 ten  horse1 #c4if2  
twelve horse1 #c4fc2 eighteen horse1    
#c4ag2 thirty horse1 #b4eb2  and in the 
forty-five horse boiler1 #b4je square   
inches4 ,taking the amount  of heating  
surface in the #de horse boiler at #i   
square feet per horse power1  we obtain 
#ah square inches of sectional area of  
flue per horse power1 which  is also    
,boulton and ,watt's proportion of      
sectional area for marine boilers  with 
internal flues4    #bfg4 ,q4--,if to    
increase the perimeter of a flue is     
virtually to diminish  the length1 then 
a tubular boiler where the perimeter is 

in effect greatly  extended ought to    
have but a short length of tube8        
,a4--,the flue of the ,nile steamer if  
reduced to the cylindrical form would   
be #ce-a_/b inches in diameter to have  
the same area2 but it would then        
require to be made #dg-c_/d feet long1  
to have the same amount of heating      
surface1 excluding the bottom as        
non-effective4 ,supposing that with     
these  proportions the heat is          
sufficiently extracted from the smoke1  
then every  tube of a tubular boiler in 
which the same draught existed ought to 
have  very nearly the same proportions4 
#bfh4 ,q4--,but what are the best       
proportions of the parts of tubular     
boilers relatively with one another8    
,a4--,the proper relative proportions of
 the parts of tubular boilers may       
easily be ascertained by a reference to 
the settled proportions of flue         
boilers2 for the same general principles
 are operative in both cases4 ,in  the  
,nile steamer each boiler of #ee horse  

power has about #dig square feet of     
flue surface or #i square feet per horse
 power1 reckoning the total surface  as 
effective4 ,the area of the flue1 which 
is rectangular is #iij square  inches1  
therefore the area is equal to that of a
 tube #ce-a_/b inches in  diameter2 and 
such a tube1 to have a heating surface  
of #dig square feet1  must be #ec4d feet
 or #fdj4h inches in length4 ,the       
length1 therefore1 of the  tube1 will be
 about #ah times its diameter1 and with 
the same velocity of  draught these     
proportions must obtain1 whatever the   
absolute dimensions of  the tube may be4
 ,with a calorimeter1 therefore1 of #ah 
square inches per  horse power1 the     
length of a tube #c inches diameter must
 not exceed #d feet  #f inches1 since   
the heat will be sufficiently extracted 
from the smoke in  this length1 if the  
smoke only travels at the velocity due  
to a calorimeter  of #ah square inches  
per horse power4    #bfi4 ,q4--,is this1
 then1 the maximum length of flue which 

can be used in  tubular boilers with    
advantage8    ,a4--,by no means4 ,the   
tubes of tubular boilers are almost     
always more than  #d feet #f inches     
long1 but then the calorimeter is almost
 always less than  #ah square inches per
 horse power--generally about two thirds
 of this4  ,indeed1 tubular boilers with
 a large calorimeter are not found to be
 so  satisfactory as where the          
calorimeter is small1 partly from the   
propensity  of the smoke in such cases  
to pass through a few of the tubes      
instead of  the whole of them1 and      
partly from the deposit of soot which   
takes place  when the draught is        
sluggish4 ,it is a very confusing       
practice1 however1 to  speak of nominal 
horse power in connection with boilers1 
since that is a  quantity quite         
indeterminate4        ,,evaporative     
,,power ,,of ,,boilers4      #bgj4      
,q4--,the main thing after all in       
boilers is their evaporative powers8    
,a4--,the proportions of tubular        

boilers1 as of all boilers1 should      
obviously have reference to the         
evaporation required1 whereas the demand
  upon the boiler for steam is very     
often reckoned contingent upon the      
nominal horse power of the engine2 and  
as the nominal power of an engine is  a 
conventional quantity by no means in    
uniform proportion to the actual        
quantity of steam consumed1 perplexing  
complications as to the proper          
proportions of boilers have in          
consequence sprung up1 to which most of 
the  failures in that department of     
engineering may be imputed4 ,it is      
highly  expedient1 therefore1 in        
planning boilers for any particular     
engine1 to  consider exclusively the    
actual power required to be produced1   
and to  apportion the capabilities of   
the boiler accordingly4    #bga4        
,q4--,in other words you would recommend
 the inquiry to be restricted  to the   
mode of evaporating a given number of   
cubic feet of water in the  hour1       

instead of embracing the problem how an 
engine of a given nominal  power was to 
be supplied with steam8    ,a4--,i would
 first1 as ,i have already stated1      
consider the actual power  required to  
be produced1 and then fix the amount of 
expansion to be  adopted4 ,if the engine
 had to work up to three times its      
nominal power1 as  is now common in     
marine engines1 ,i should either        
increase correspondingly  the quantity  
of evaporating surface in the boiler1 or
 adopt such an amount  of expansion as  
would increase threefold the efficacy of
 the steam1 or  combine in a modified   
manner both of these arrangements4      
,reckoning the  evaporation of a cubic  
foot of water in the hour as equivalent 
to an actual  horse power1 and allowing 
a square yard or #i square feet as the  
proper  proportion of flue surface to   
evaporate a cubic foot of water in the  
hour1  it is clear that ,i must either  
give #bg square feet of heating surface 
in  the boiler to have a trebled power  

without expansion1 or ,i must cut off   
the  steam at one seventh of the stroke 
to obtain a three-fold power without    
increasing the quantity of heating      
surface4 ,by cutting off the steam1     
however1 at one third of the stroke1 a  
heating surface of #ac-a_/b square  feet
 will give a threefold power1 and it    
will usually be the most judicious      
course to carry the expansion as far as 
possible1 and then to add the           
proportion of heating surface necessary 
to make good the deficiency still  found
 to exist4    #bgb4 ,q4--,but is it     
certain that a cubic foot of water      
evaporated in the  hour is equivalent to
 an actual horse power8    ,a4--,an     
actual horse power as fixed by ,watt is 
#cc1jjj lbs4 raised one foot  high in   
the minute2 and in ,watt's #dj horse    
power engine1 with a #ca-a_/b inch      
cylinder1 #g feet stroke1 and making    
#ag-a_/b strokes a minute1 the effective
  pressure is #f4ib lbs4 on the square  
inch clear of all deductions4 ,now1 as a

  horse power is #cc1jjj lbs4 raised one
 foot high1 and as there are #f4ib lbs1 
on the square inch1 it is clear that    
#cc1jjj divided by #f4ib1 on #dgfh      
square  inches with #f4ib lbs4 on each  
if lifted #a foot or #ab inches high1   
will also  be equal to a horse power4   
,but #dgfh square inches multiplied by  
#ab inches  in height is #egbbd4d cubic 
inches1 or #cc4a cubic feet1 and this is
 the  quantity of steam which must be   
expended per minute to produce an actual
  horse power4    #bgc4 ,q4--,but are   
#cc cubic feet of steam expended per    
minute equivalent to  a cubic foot of   
water expended in the hour8             
,a44--,not precisely1 but nearly so4 ,a 
cubic foot of water produces #affi      
cubic feet of steam of the atmospheric  
density of #ae lbs4 per square inch1    
whereas a consumption of #cc cubic feet 
of steam in the minute is #aihj cubic   
feet in the hour4 ,in ,watt's engines   
about one tenth was reckoned as loss in 
filling the waste spaces at the top and 

bottom of the cylinder1 making #ahgb    
cubic feet as the quantity consumed per 
hour without this waste2 and in  modern 
engines the waste at the ends of the    
cylinder is inconsiderable4    #bgd4    
,q4--,what power was generated by a     
cubic foot of water in the case of  the 
,albion ,mill engines when working      
without expansion8    ,a4--,in the      
,albion ,mill engines when working      
without expansion1 it was  found that #a
 lb4 of water in the shape of steam     
raised #bh1dhi lbs4 #a foot  high4 ,a   
cubic foot of water1 therefore1 or      
#fb-a_/b lbs41 if consumed in the  hour1
 would raise #aghjefb4e lbs4 one foot   
high in the hour1 or would raise        
#bi1fgf lbs4 one foot high in a minute2 
and if to this we add one tenth for     
waste at the ends of the cylinder1 a    
waste which hardly exists in modern     
engines1 we have #cb1fdc lbs4 raised one
 foot high in the minute1 or a horse    
power very nearly4 ,in some cases the   
approximation appears still nearer4     

,thus1 in a #dj horse engine working    
without expansion1 ,watt found that     
4#fgd  feet of water were evaporated    
from the boiler per minute1 which is    
just a  cubic foot per horse power per  
hour2 but it is not certain in this case
  that the nominal and actual power were
 precisely identical4 ,it will be  quite
 safe1 however1 to reckon an actual     
horse power as producible by the        
evaporation of a cubic foot of water in 
the hour in the case of engines  working
 without expansion2 and for boiling off 
this quantity in flue or  wagon boilers1
 about #h lbs4 of coal will be required 
and #i square feet of  flue surface4    
,,modern ,,marine ,,and ,,locomotive    
,,boilers4    #bge4 ,q4--,these         
proportions appear chiefly to refer to  
old boilers4 ,i wish  you to state what 
are the proportions of modern flue and  
tubular marine  boilers4    ,a4--,in    
modern marine boilers the area of fire  
grate is less than in ,mr4  ,watt's     
original boilers1 where it was one      

square foot to nine square feet  of     
heating surface4 ,the heat in the       
furnace is consequently more intense1   
and a somewhat less amount of surface   
suffices to evaporate a cubic foot of   
water4 ,in ,boulton and ,watt's modern  
flue boilers they allow for the         
evaporation of a cubic foot of water #h 
square feet of heating surface1 #gj     
square inches of fire grate1 #ac square 
inches sectional area of flues1 #f      
square inches sectional area of chimney1
 #ad square inches area over furnace    
bridges1 ratio of area of flue to area  
of fire grate #a to #e4d4 ,to evaporate 
a cubic foot of water per hour in       
tubular boilers1 the proportions are--  
heating surface #i square feet1 fire    
grate #gj square inches1 sectional area 
of tubes #aj square inches1 sectional   
area of back uptake #ab square inches1  
sectional area of front uptake #aj      
square inches1 sectional area of chimney
  #g square inches1 ratio of diameter of
 tube to length of tube #a_/bhth to     

#a_/cjth1 cubical content of boiler     
exclusive of steam chest #f4e cubic     
feet1  cubical content of steam chest   
#a4e cubic feet4    #bgf4 ,q4--,these   
proportions do not apply to locomotive  
boilers8    ,a4--,not at all4 ,in       
locomotive boilers the draught is       
maintained by the  projection of the    
waste steam which escapes from the      
cylinders up the  chimney1 and the      
draught is much more powerful and the   
combustion much more  rapid than in     
cases in which the combustion is        
maintained by the natural  draught of a 
chimney1 except indeed the chimney be of
 very unusual  temperature and height4  
,the proportions proper for locomotive  
boilers will  be seen by the dimensions 
of a few locomotives of approved        
construction1  which have been found to 
give satisfactory results in practice1  
and which  are recorded in the following
 ,table3                                
,name of ,engine                        
,great ,britain4   ,pallas4      ,snake4

      ,sphinx4  ,diameter of cylinder   
#ah in4      #ae in4     #ad-a_/d in4   
#ah in4  ,length of stroke              
#bd in4      #bj in4     #ba in4        
#bd in4  ,diameter of driving wheel     
#h ft4       #f ft4     #f-a_/b ft4     
#e ft4  ,inside diameter of fire box    
#ec in4      #ee in4     #da-a_/c in4   
#dd in4  ,inside width of fire box      
#fc in4      #db in4     #dc-a_/d in4   
#ci-a_/b;in4  ,height of fire box above 
bars  #fc in4      #eb in4     #dh-a_/c 
in4 #ee-a_/b;in4  ,number of fire bars  
#bi          444  #cb               #af 
,thickness of fire bars         #c_/d   
in4     #a-c_/d in4  #e_/h in4        #a
 in4  ,number of ,tubes                 
#cje         #acd        #aha           
#adb  ,outside diameter of tubes      #b
 in4       #b in4      #a-g_/h in4      
#b-a_/h                                 
in4  ,length of tubes                #aa
 ft #c in  #aj ft #f in #aj ft #c-a_/b  
in4 #ad                                 
ft #c-a_/d in4  ,space between tubes    

#a_/b in4     #c_/d in4    #a_/b in4    
,inside diameter of ferules     #a-i_/af
 in4  #a-a_/b in4  #a-e_/af in4 #a-e_/h 
in4  ,diameter of chimney            #ag
 in4      #ae in4     #ac in4           
#ae-a_/b in4  ,diameter of blast orifice
      #e-a_/b in4    #d-e_/h in4 #d-a_/b
 in4  #d-c_/d in4  ,area of grate       
#ba sq4 ft4  #af4jd sqft #ab4d sq4 ft4  
#aj4ef                                  
sq4 ft  ,area of air space of grate     
#aa4d sqft   #d4jh sqft  #e4ed sq4 ft4  
#e                                      
sq4 ft4  ,area of tubes                 
#e4df sqft   #b4dj sqft  #b4h sq4 ft4   
#b4ib                                   
sq4 ft4  ,area though ferules           
#d sq4 ft4   #a4fd sqft  #b sq4 ft4     
#b4jd                                   
sq4 ft4  ,area of chimney               
#a4gg sqft   #a4bc sqft  4#iba sq4 ft4  
#a4ca                                   
sq4 ft4  ,area of blast orifice         
#bc4gf sqin  #af4h sqin  #ad4ah sq4 in4 
#ag4g                                   

sq4 in4  ,heating surface of tubes      
#afbg sqft   #ffh4g sqft #hbc sq4 ft4   
#hfd                                    
sq4 ft4        ,,the ,,blast ,,in       
,,locomotives4    #bgg4 ,q4--,what is   
the amount of draught produced in       
locomotive boilers in  comparison with  
that existing in other boilers8         
,a4--,a good chimney of a land engine   
will produce a degree of exhaustion     
equal to from #a-a_/b to #b-a_/b inches 
of water4 ,in locomotive boilers the    
exhaustion is in some cases equal to #ab
 or #ac inches of water1 but from #c  to
 #f inches is a more common proportion4 
#bgh4 ,q4--,and what force of blast is  
necessary to produce this exhaustion8   
,a4--,the amount varies in different    
engines1 depending on the sectional     
area of the tubes and other             
circumstances4 ,but on the average1 it  
may be  asserted that such a pressure of
 blast as will support an inch of       
mercury1  will maintain sufficient      
exhaustion in the smoke box to support  

an inch of  water2 and this ratio holds 
whether the exhaustion is little or     
great4 ,to  produce an exhaustion in the
 smoke box1 therefore1 of #f inches of  
water1  the waste steam would require to
 be of sufficient pressure to support a 
column of #f inches of mercury1 which is
 equivalent to a pressure of #c lbs4  on
 the square inch4    #bgi4 ,q4--,how is 
the force of the blast determined8      
,a4--,by the amount of contraction given
 to the mouth of the blast pipe1  which 
is a pipe which conducts the waste steam
 from the cylinders and  debouches at   
the foot of the chimney4 ,if a strong   
blast be required1 the  mouth of this   
pipe requires to be correspondingly     
contracted1 but such  contraction throws
 a back pressure on the piston1 and it  
is desirable to  obtain the necessary   
draught with as little contraction of   
the blast pipe  as possible4 ,the blast 
pipe is generally a breeches pipe of    
which the legs  join just before        
reaching the chimney2 but it is better  

to join the two  cylinders below1 and to
 let a single pipe ascend to within #ab 
or #ah inches  of the foot of the       
chimney4 ,if made with too short a piece
 of pipe above  the joining1 the steam  
will be projected against each side of  
the chimney  alternately1 and the       
draught will be damaged and the chimney 
worn4 ,the  blast pipe should not be    
regularly tapered1 but should be large  
in the body  and gathered in at the     
mouth4    #bhj4 ,q4--,is a large and    
high chimney conducive to strength of   
draught in  locomotives8    ,a4--,it has
 not been found to be so4 ,a chimney of 
three or four times its  own diameter in
 height appears to answer fully as well 
as a longer one2 and  it was found that 
when in an engine with #ag inch         
cylinders a chimney of  #ae-a_/d inches 
was substituted for a chimney of        
#ag-a_/b inches1 a superior  performance
 was the result4 ,the chimney of a      
locomotive should have half  the area of
 the tubes at the ferules1 which is the 

most contracted part1  and the blast    
orifice should have #a_/ajth of the area
 of the chimney4 ,the  sectional area of
 the tubes through the ferules should be
 as large as  possible4 ,tubes without  
ferules it is found pass one fourth more
 air1 and  tubes with ferules only at   
the smoke box end pass one tenth more   
air than  when there are ferules at both
 ends4    #bha4 ,q4--,is the exhaustion 
produced by the blast as great in the   
fire box  as in the smoke box8          
,a4--,experiments have been made to     
determine this1 and in few cases has it 
been found to be more than about half as
 great as ordinary speeds2 but much     
depends on the amount of contraction in 
the tubes4 ,in an experiment made  with 
an engine having #adg tubes of #a-c_/d  
inches external diameter1 and #ac  feet 
#aj inches long1 and with a fire grate  
having an area of #i-a_/b square  feet1 
the exhaustion at all speeds was found  
to be three times greater in  the smoke 
box than in the fire box4 ,the          

exhaustion in the smoke box was         
generally equivalent to #ab inches of   
water1 while in the fire box it was     
equivalent to only #d inches of water2  
showing that #d inches were required  to
 draw the air through the grate and #h  
inches through the tubes4    #bhb4      
,q4--,what will be the increase of      
evaporation in a locomotive from a      
given increase of exhaustion8           
,a4--,the rate of evaporation in a      
locomotive or any other boiler will vary
  as the quantity of air passing through
 the fire1 and the quantity of air      
passing through the fire will vary      
nearly as the square root of the        
exhaustion4 ,with four times the        
exhaustion1 therefore1 there will be    
about  twice the evaporation1 and       
experiment shows that this theoretical  
law holds  with tolerable accuracy in   
practice4    #bhc4 ,q4--,but the same   
exhaustion will not be produced by a    
given strength  of blast in all engines8
    ,a4--,no2 engines with contracted   

fire grates and an inadequate sectional 
area of tubes1 will require a stronger  
blast than engines of better            
proportions2 but in any given engine the
 relations between the blast  exhaustion
 and evaporation1 hold which have been  
already defined4    #bhd4 ,q4--,is the  
intensity of the draught under easy     
regulation8    ,a4--,the intensity of   
the draught may easily be diminished by 
partially  closing the damper in the    
chimney1 and it may be increased by     
contracting  the orifice of the blast4  
,a variable blast pipe1 the orifice of  
which may  be enlarged or contracted at 
pleasure1 has been much used4 ,there are
  various devices for this purpose1 but 
the best appears to be that adopted  in 
,stephenson's engine1 where a conical   
nozzle is moved up or down within  the  
blast pipe1 which is made somewhat      
larger in diameter than the base of  the
 cone1 but with a ring projecting       
internally1 against which the base of   
the cone abuts when the nozzle is pushed

 up4 ,when the nozzle stands at the  top
 of the pipe the whole of the steam has 
to pass through it1 and the  intensity  
of the blast is increased by the        
increased velocity thus given to  the   
steam2 whereas when the nozzle is moved 
downward the steam escapes  through the 
annular opening left between the nozzle 
and the pipe1 as well  as through the   
nozzle itself1 and the intensity of the 
blast is diminished  by the enlargement 
of the opening for the escape of the    
steam thus made  available4             
#bhe4,q4--,what is the best diameter for
 the tubes of locomotive boilers8       
,a4--,bury's locomotive with #ad inch   
cylinders contains #ib tubes of         
#b-a_/hth  inches external diameter1 and
 #aj feet #f inches long2 whereas       
,stephenson's  locomotive with #ae inch 
cylinders contains #aej tubes of        
#a-e_/hths external  diameter1 #ac feet 
#f inches long4 ,in ,stephenson's       
boiler1 in order that the  part of the  
tubes next the chimney may be of any    

avail for the generation  of steam1 the 
draught has to be very intense1 which in
 its turn involves a  considerable      
expenditure of power2 and it is         
questionable whether the  increased     
expenditure of power upon the blast1 in 
,stephenson's long tubed  locomotives1  
is compensated by the increased         
generation of steam consequent  upon the
 extension of the heating surface4 ,when
 the tubes are small in  diameter they  
are apt to become partially choked with 
pieces of coke2 but  an internal        
diameter of #a-e_/hths may be employed  
without inconvenience if  the draught be
 of medium intensity4    #bhf4          
,q4--,will you illustrate the relation  
between the length and diameter  of     
locomotive tubes by a comparison with   
the proportion of flues in flue         
boilers8    ,a4--,in most locomotives   
the velocity of the draught is such that
 it would  require very long tubes to   
extract the heat from the products of   
combustion1 if the heat were transmitted

 through the metal of the tubes  with   
only the same facility as through the   
iron of ordinary flue boilers4  ,the    
,nile steamer1 with engines of #aaj     
nominal horses power each1 and with  two
 boilers having two independent flues in
 each1 of such dimensions as to  make   
each flue equivalent to #ee nominal     
horses power1 works at #fb per cent4    
above the nominal power1 so that the    
actual evaporative efficacy of each     
flue would be equivalent to #hi actual  
horses power1 supposing the engines  to 
operate without expansion2 but as the   
mean pressure in the cylinder is        
somewhat less than the initial pressure1
 the evaporative efficacy of each  flue 
may be reckoned equivalent to #hj actual
 horses power4 ,with this  evaporative  
power there is a calorimeter of #iij    
square inches1 or #ab4c  square inches  
per actual horse power2 whereas in      
,stephenson's locomotive  with #aej     
tubes1 if the evaporative power be taken
 at #bjj cubic feet of  water in the    

hour1 which is a large supposition1 the 
engine will be equal  to #bjj actual    
horses power4 ,if the internal diameter 
of the tubes be taken  at thirteen      
eighths of an inch1 the calorimeter per 
actual horse power will  only be #a4aacf
 square inches1 or in other words the   
calorimeter in the  locomotive boiler   
will be #aa4aa times less than in the   
flue boiler for the  same power1 so that
 the draught in the locomotive must be  
#aa4aa times  stronger1 and the ratio of
 the length of the tube to its diameter 
#aa4aa  times greater than in the flue  
boiler1 supposing the heat to be        
transmitted  with only the same         
facility4 ,the flue of the ,nile would  
require to be #ce-  #a_/b inches in     
diameter if made of the cylindrical     
form1 and #dg-c_/d feet  long2 the tubes
 of a locomotive if #a-c_/hths inch     
diameter would only  require to be      
#bb4ai inches long with the same        
velocity of draught2 but as  the draught
 is #aa4aa times faster than in a flue  

boiler1 the tubes ought to  be #bdf4eeh 
inches1 or about #bj-a_/b feet long     
according to this proportion4  ,in      
practice1 however1 they are one third   
less than this1 which reduces the       
heating surface from #i to #f square    
feet per actual horse power1 and this   
length even is found to be inconvenient4
 ,it is greatly preferable therefore  to
 increase the calorimeter1 and diminish 
the intensity of the draught4           
,,boiler ,,chimneys4    #bhg4 ,q4--,by  
what process do you ascertain the       
dimensions of the chimney  of a land    
boiler8    ,a4--,by a reference to the  
volume of air it is necessary in a given
 time  to supply to the burning fuel1   
and to the velocity of motion produced  
by  the rarefaction in the chimney2 for 
the area of the chimney requires to be  
such1 that with the velocity due to that
 rarefaction1 the quantity of air       
requisite for the combustion of the fuel
 shall pass through the furnace in  the 
specified time4 ,thus if #bjj cubic feet

 of air of the atmospheric  density are 
required for the combustion of a pound  
of coal1--though #bej  lbs4 is nearer   
the quantity generally required1--and   
#aj lbs4 of coal per  horse power per   
hour are consumed by an engine1 then    
#bjjj cubic feet of air  must be        
supplied to the furnace per horse power 
per hour1 and the area of  the chimney  
must be such as to deliver this quantity
 at the increased bulk  due to the high 
temperature of the chimney when moving  
with the velocity  the rarefaction      
within the chimney occasions1 and which1
 in small chimneys1  is usually such as 
to support a column of half an inch of  
water4 ,the  velocity with which a      
denser fluid flows into a rarer one is  
equal to the  velocity a heavy body     
acquires in falling through a height    
equal to the  difference of altitude of 
two columns of the heavier fluid of such
 heights  as will produce the respective
 pressures2 and1 therefore1 when the    
difference of pressure or amount of     

rarefaction in the chimney is known1 it 
is easy to tell the velocity of motion  
which ought to be produced by it4 ,in   
practice1 however1 these theoretical    
results are not to be trusted1 until    
they have received such modifications as
 will make them representative of  the  
practice of the most experienced        
constructors4    #bhh4 ,q4--,what then  
is the rule followed by the most        
experienced  constructors8              
,a4--,boulton and ,watt's rule for the  
dimensions of the chimney of a land     
engine is as follows3--multiply the     
number of pounds of coal consumed under 
the boiler per hour by #ab1 and divide  
the product by the square root of the   
height of the chimney in feet2 the      
quotient is the area of the chimney in  
square inches in the smallest part4 ,a  
factory chimney suitable for a #bj      
horse boiler is commonly made about #bj 
in4 square inside1 and #hj ft4 high2    
and these dimensions are those which    
answer to a consumption of #ae lbs4 of  

coal per horse power per hour1 which is 
a very common consumption in  factory   
engines4 ,if #ae lbs4 of coal be        
consumed per horse power per hour1  the 
total consumption per hour in a #bj     
horse boiler will be #cjj lbs41 and     
#cjj multiplied by #ab  #cfjj1 and      
divided by #i 7the square root of the   
height7  #djj1 which is the area of the 
chimney in square inches4 ,it will  not 
answer well to increase the height of a 
chimney of this area to more  than #dj  
or #ej yards1 without also increasing   
the area1 nor will it be of  utility to 
increase the area much without also     
increasing the height4 ,the  quantity of
 coal consumed per hour in pounds1      
multiplied by #e1 and divided  by the   
square root of the height of the        
chimney1 is the proper collective  area 
of the openings between the bars of the 
grate for the admission of air  to the  
fire4    #bhi4 ,q4--,is this rule       
applicable to the chimneys of steam     
vessels8    ,a4--,in steam vessels      

,boulton and ,watt have heretofore been 
in the habit  of allowing #h-a_/b square
 inches of area of chimney per horse    
power1 but  they now allow #f square    
inches to #g square inches4 ,in some    
steam vessels a  steam blast like that  
of a locomotive1 but of a smaller       
volume1 is used in  the chimney1 and    
many of the evils of a boiler deficient 
in draught may be  remedied by this     
expedient1 but a steam blast in a low   
pressure engine  occasions an obvious   
waste of steam2 it also makes an        
unpleasant noise1 and  in steam vessels 
it frequently produces the inconvenience
 of carrying the  smaller parts of the  
coal up the chimney1 and scattering it  
over the deck  among the passengers4 ,it
 is advisable1 therefore1 to give a     
sufficient  calorimeter in all low      
pressure boilers1 and a sufficient      
height of chimney  to enable the chimney
 to operate without a steam jet2 but it 
is useful to  know that a steam jet is a
 resource in the case of a defective    

boiler1 or  where the boiler has to be  
urged beyond its power4        ,,steam  
,,room ,,and ,,priming4    #bij4        
,q4--,what is the capacity of steam room
 allowed in boilers per horse  power8   
,a4--,the capacity of steam room allowed
 by ,boulton and ,watt in their land    
wagon boilers is #h-c_/d cubic feet per 
horse power in the two horse power      
boiler1 and #e-c_/d cubic feet in the   
#bj horse power boiler2 and in the      
larger class of boilers1 such as those  
suitable for #cj and #de horse power    
engines1 the capacity of the steam room 
does not fall below this amount1  and1  
indeed1 is nearer #f than #e-c_/d cubic 
feet per horse power4 ,the content  of  
water is #ah-a_/b cubic feet per horse  
power in the two horse power  boiler1   
and #ae cubic feet per horse power in   
the #bj horse power boiler4    #bia4    
,q4--,is this the proportion ,boulton   
and ,watt allow in their marine         
boilers8    ,a4--,boulton and ,watt in  
their early steam vessels were in the   

habit of  allowing for the capacity of  
the steam1 space in marine boilers #af  
times  the content of the cylinder2 but 
as there were two cylinders1 this was   
equivalent to #h times the content of   
both cylinders1 which is the  proportion
 commonly followed in land engines1 and 
which agrees very nearly  with the      
proportion of between #e and #f cubic   
feet of steam room per horse  power     
already referred to4 ,taking for example
 an engine with #bc inches  diameter of 
cylinder and #d feet stroke1 which will 
be #ah4d horse power--the  area of the  
cylinder will be #dae4dgf square inches1
 which1 multiplied by  #dh1 the number  
of inches in the stroke1 will give      
#aiidb4hdh for the  capacity of the     
cylinder in cubic inches2 #h times this 
is #aeiedb4ghd cubic  inches1 or #ib4c  
cubic feet2 #ib4c divided by #ah4d is   
rather more than #e  cubic feet per     
horse power4    #bib4 ,q4--,is the      
production of the steam in the boiler   
uniform throughout  the stroke of the   

engine8    ,a4--,it varies with the     
slight variations in the pressure within
 the  boiler throughout the stroke4     
,usually the larger part of the steam is
  produced during the first part of the 
stroke of the engine1 for there is  then
 the largest demand for steam1 as the   
steam being commonly cut off  somewhat  
before the end of the stroke1 the       
pressure rises somewhat in the  boiler  
during that period1 and little steam is 
then produced4 ,there is less  necessity
 that the steam space should be large   
when the flow of steam from  the boiler 
is very uniform1 as it will be where    
there are two engines  attached to the  
boiler at right angles with one another1
 or where the  engines work at a great  
speed1 as in the case of locomotive     
engines4 ,a high  steam chest too1 by   
rendering boiling over into the steam   
pipes1 or priming  as it is called1 more
 difficult1 obviates the necessity for  
so large a  steam space2 as does also a 
perforated steam pipe stretching through

 the  length of the boiler1 so as not to
 take the steam from one place4 ,the use
  of steam of a high pressure1 worked   
expansively1 has the same operation2 so 
that in modern marine boilers1 of the   
tubular construction1 where the whole   
or most of these modifying circumstances
 exist1 there is no necessity for  so   
large a proportion of steam room as #e  
or #f cubic feet per nominal horse      
power1 and about one1 #a-a_/b1 or #b    
cubic feet of steam room per cubic foot 
of water evaporated1 more nearly        
represents the general practice4        
#bic4 ,q4--,is this the proportion of   
steam room adopted in locomotive        
boilers8    ,a4--,no2 in locomotive     
boilers the proportion of steam room per
 cubic foot  of water evaporated is     
considerably less even than this4 ,it   
does not  usually exceed #a_/e of a     
cubic foot per cubic foot of water      
evaporated2 and  with clean water1 with 
a steam dome a few feet high set on the 
barrel of  the boiler1 or with a        

perforated pipe stretching from end to  
end of the  barrel1 and with the steam  
room divided about equally between the  
barrel  and the fire box1 very little   
priming is found to occur even with this
  small proportion of total steam room4 
,about #c_/d the depth of the barrel is 
usually filled with water1 and #a_/d    
with steam4    #bid4 ,q4--,what is      
priming8    ,a4--,priming is a violent  
agitation of the water within the       
boiler1 in  consequence of which a large
 quantity of water passes off with the  
steam in  the shape of froth or spray4  
,such a result is injurious1 both as    
regards  the efficacy of the engine1 and
 the safety of the engine and boiler2   
for  the large volume of hot water      
carried by the steam into the condenser 
impairs the vacuum1 and throws a great  
load upon the air pump1 which           
diminishes the speed and available power
 of the engine2 and the existence  of   
water within the cylinder1 unless there 
be safety valves upon the  cylinder to  

permit its escape1 will very probably   
cause some part of the  machinery to    
break1 by suddenly arresting the motion 
of the piston when it  meets the surface
 of the water1--the slide valve being   
closed to the  condenser before the     
termination of the stroke1 in all       
engines with lap  upon the valves1 so   
that the water within the cylinder is   
prevented from  escaping in that        
direction4 ,at the same time the boiler 
is emptied of its  water too rapidly for
 the feed pump to be able to maintain   
the supply1 and  the flues are in danger
 of being burnt from a deficiency of    
water above  them4    #bie4 ,q4--,what  
are the causes of priming8    ,a4--,the 
causes of priming are an insufficient   
amount of steam room1 an  inadequate    
area of water level1 an insufficient    
width between the flues or  tubes for   
the ascent of the steam and the descent 
of water to supply the  vacuity the     
steam occasions1 and the use of dirty   
water in the boiler4 ,new  boilers prime

 more than old boilers1 and steamers    
entering rivers from the  sea are more  
addicted to priming than if sea or river
 water had alone been  used in the      
boilers--probably from the boiling point
 of salt water being  higher than that  
of fresh1 whereby the salt water acts   
like so much molten  metal in raising   
the fresh water into steam4 ,opening the
 safety valve  suddenly may make a      
boiler prime1 and if the safety valve be
 situated near  the mouth of the steam  
pipe1 the spray or foam thus created may
 be mingled  with the steam passing into
 the engine1 and materially diminish its
  effective power2 but if the safety    
valve be situated at a distance from the
  mouth of the steam pipe1 the quantity 
of foam or spray passing into the       
engine may be diminished by opening the 
safety valve2 and in locomotives1       
therefore1 it is found beneficial to    
have a safety valve on the barrel of    
the boiler at a point remote from the   
steam chest1 by partially opening       

which1 any priming in that part of the  
boiler adjacent to the steam chest  is  
checked1 and a purer steam than before  
pusses to the engine4    #bif4          
,q4--,what is the proper remedy for     
priming8    ,a4--,when a boiler primes1 
the engineer generally closes the       
throttle  valve partially1 turns off the
 injection water1 and opens the furnace 
doors1 whereby the generation of steam  
is checked1 and a less violent          
ebullition in the boiler suffices4      
,where the priming arises from an       
insufficient amount of steam room1 it   
may be mitigated by putting a higher    
pressure upon the boiler and working    
more expansively1 or by the             
interposition of a perforated plate     
between the boiler and the steam chest1 
which breaks the ascending water and    
liberates the steam4 ,in some cases1    
however1 it may be necessary to set a   
second steam chest on the top of the    
existing one1 and it will be preferable 
to establish a communication with  this 

new chamber by means of a number of     
small holes1 bored through the  iron    
plate of the boiler1 rather than by a   
single large orifice4 ,where  priming   
arises from the existence of dirty water
 in the boiler1 the evil  may be        
remedied by the use of collecting       
vessels1 or by blowing off largely  from
 the surface2 and where it arises from  
an insufficient area of water  level1 or
 an insufficient width between the flues
 for the free ascent of  the steam and  
the descent of the superincumbent water1
 the evil may be  abated by the addition
 of circulating pipes in some part of   
the boiler1  which will allow the water 
to descend freely to the place from     
whence the  steam rises1 the width of   
the water spaces being virtually        
increased by  restricting their function
 to the transmission of a current of    
steam and  water to the surface4 ,it is 
desirable to arrange the heating surface
 in  such a way that the feed water     
entering the boiler at its lowest point 

is  heated gradually as it ascends1     
until toward the superior part of the   
flues  it is raised gradually into      
steam2 but in all cases there will be   
currents  in the boiler for which it is 
proper to provide4 ,the steam pipe      
proceeding  to the engine should        
obviously be attached to the highest    
point of the  steam chest1 in boilers of
 every construction4    #big4           
,q4--,having now stated the proportions 
proper to be adopted for  evaporating   
any given quantity of water in steam    
boilers1 will you proceed  to show how  
you would proportion a boiler to do a   
given amount of work8 say  a locomotive 
boiler which will propel a train of #ajj
 tons weight at a speed  of #ej miles an
 hour4    ,a4--,according to experiments
 on the resistance of railway trains at 
various rates of speed1 made by ,mr4    
,gooch1 of the ,great ,western ,railway1
 it  appears that a train weighing1 with
 locomotive1 tender1 and carriages1     
about #ajj tons1 experiences1 at a speed

 of #ej miles an hour1 a resistance  of 
about #c1jjj lbs41 or about #cj lbs4 per
 ton2 which resistance includes  the    
resistance of the engine as well as that
 of the train4 ,this1 therefore1  is the
 force which must be imparted at the    
circumference of the driving  wheels1   
except that small part intercepted by   
the engine itself1 and the  force       
exerted by the pistons must be greater  
than that at the circumference  of the  
driving wheel1 in the proportion of     
their slower motion1 or in the          
proportion of the circumference of the  
driving wheel to the length of a  double
 stroke of the engine4 ,if the diameter 
of the driving wheel be #e-a_/b  feet1  
its circumference will be #ag4bgh feet1 
and if the length of the  stroke be #ah 
inches1 the length of a double stroke   
will be #c feet4 ,the  pressure on the  
pistons must therefore be greater than  
the traction at the  circumference of   
the driving wheel1 in the proportion of 
#ag4bgh to #c1 or1  in other words1 the 

mean pressure on the pistons must be    
#ag1bgh lbs42 and  the area of          
cylinders1 and pressure of steam1 must  
be such as to produce  conjointly this  
total pressure4 ,it thus becomes easy to
 tell the volume and  pressure of steam 
required1 which steam in its turn       
represents its  equivalent of water     
which is to be evaporated from the      
boiler1 and the  boiler must be so      
proportioned1 by the rules already      
given1 as to evaporate  this water      
freely4 ,in the case of a steam vessel1 
the mode of procedure is  the same1 and 
when the resistance and speed are known1
 it is easy to tell  the equivalent     
value of steam4        ,,strength ,,of  
,,boilers4    #bih4 ,q4--,what strain   
should the iron of boilers be subjected 
to in  working8    ,a4--,the iron of    
boilers1 like the iron of machines or   
structures1 is  capable of withstanding 
a tensile strain of from #ej1jjj to     
#fj1jjj lbs4 upon  every square inch of 
section2 but it will only bear a third  

of this strain  without permanent       
derangement of structure1 and it does   
not appear  expedient in any boiler to  
let the strain exceed #d1jjj lbs4 upon  
the square  inch of sectional area of   
metal1 especially if it is liable to be 
weakened  by corrosion4                 
#bii4,q4--,have any experiments been    
made to determine the strength of       
boilers8    ,a4--,the question of the   
strength of boilers was investigated    
very  elaborately a few years ago by a  
committee of the ,franklin ,institute1  
in  ,america1 and it was found that the 
tenacity of boiler plate increased with 
the temperature up to #eej1 at which    
point the tenacity began to diminish4   
,at #cb1 the cohesive force of a square 
inch of section was #ef1jjj lbs42 at    
#egj1 it was #ff1ejj lbs42 at #gbj1     
#ee1jjj lbs42 at #a1jej1 #cb1jjj lbs42  
at  #a1bdj1 #bb1jjj lbs42 and at #a1cag1
 #i1jjj lbs4 ,copper follows a different
  law1 and appears to be diminished in  
strength by every addition to the       

temperature4 ,at #cb the cohesion of    
copper was found to be #cb1hjj lbs4 per 
square inch of section1 which exceeds   
the cohesive force at any higher        
temperature1 and the square of the      
diminution of strength seems to keep    
pace with the cube of the increased     
temperature4 ,strips of iron cut in the 
direction of the fibre were found to be 
about #f per cent4 stronger than  when  
cut across the grain4 ,repeated piling  
and welding was found to  increase the  
tenacity of the iron1 but the result of 
welding together  different kinds of    
iron was not found to be favorable4 ,the
 accidental  overheating of a boiler was
 found to reduce the ultimate or maximum
  strength of the plates from #fe1jjj to
 #de1jjj lbs4 per square inch of        
section1 and riveting the plates was    
found to occasion a diminution in  their
 strength to the extent of one third4   
,these results1 however1 are not        
precisely the same as those obtained by 
,mr4 ,fairbairn4    #cjj4 ,q4--,what    

were the results obtained by him8       
,a4--,he found that boiler plate bore a 
tensile strain of #bc tons per  square  
inch before rupture1 which was reduced  
to #af tons per square inch  when joined
 together by a double row of rivets1 and
 #ac tons1 or about  #cj1jjj1 when      
joined together by a single row of      
rivets4 ,a circular boiler1  therefore1 
with the ends of its plates double      
riveted1 will bear at the  utmost about 
#cf1jjj lbs4 per square inch of section1
 or about #ab1jjj lbs4  per square inch 
of section without permanent derangement
 of structure4    #cja4 ,q4--,what      
pressure do cylindrical boilers sustain 
in practice8    ,a4--,in some locomotive
 boilers1 which are worked with a       
pressure of #hj  lbs4 upon the square   
inch1 the thickness of the plates is    
only #e_/afths of  an inch1 while the   
barrel of the boiler is #ci inches in   
diameter4 ,it will  require a length of 
#c4b inches of the boiler when the      
plates are #e_/afths  thick to make up a

 sectional area of one square inch1 and 
the separating  force will be #ci times 
#c4b multiplied by #hj1 which makes the 
separating  force #i1ihd lbs41 sustained
 by two square inches of sectional      
area--one on  each side2 or the strain  
is #d1iib lbs4 per square inch of       
sectional area1  which is quite as great
 strain as is advisable4 ,the accession 
of strength  derived from the boiler    
ends is not here taken into account1 but
 neither is  the weakening effect       
counted that is caused by the rivet     
holes4 ,some  locomotives of #d feet    
diameter of barrel and of #c_/hths iron 
have been  worked to as high a pressure 
as #bjj lbs4 on the inch2 but such feats
 of  daring are neither to be imitated  
nor commended4    #cjb4,q4--,can you    
give a rule for the proper thickness of 
cylindrical  boilers8    ,a4--,the      
thickness proper for cylindrical boilers
 of wrought iron1 exposed  to an        
internal pressure1 may be found by the  
following rule3--multiply #b4ed  times  

the internal diameter of the cylinder in
 inches by the greatest  pressure within
 the cylinder per circular inch1 and    
divide by #ag1hjj2 the  result is the   
thickness in inches4 ,if we apply this  
rule to the example of  the locomotive  
boiler just given1 we have #ci x #b4ed x
 #fb4hcb 7the pressure  per circular    
inch corresponding to #hj lbs4 per      
square inch7  #fbbd4acgi1  and this1    
divided by #ag1hjj1 gives #j4cdi as the 
thickness in inches1  instead of        
#j4cabe1 or #e_/afths1 the actual       
thickness4 ,if we take the  pressure per
 square inch instead of per circular    
inch1 we obtain the  following rule1    
which is somewhat simpler3--multiply the
 internal diameter  of the cylinder in  
inches by the pressure in pounds per    
square inch1 and  divide the product by 
#h1ijj2 the result is the thickness in  
inches4 ,both  these rules give the     
strain about one fourth of the elastic  
force1 or #d1dej  lbs4 per square inch  
of sectional area of the iron2 but      

#c1jjj lbs4 is  enough when the flame   
impinges directly on the iron1 as in    
some of the  ordinary cylindrical       
boilers1 and the rule may be adapted for
 that strain  by taking #f1jjj as a     
divisor instead of #h1ijj4    #cjc4     
,q4--,in marine and wagon boilers1 which
 are not of a cylindrical  form1 how do 
you procure the requisite strength8     
,a4--,where the sides of the boiler are 
flat1 instead of being cylindrical1  a  
sufficient number of stays must be      
introduced to withstand the pressure2   
and it is expedient not to let the      
strain upon these stays be more than    
#c1jjj lbs4 per square inch of section1 
as the strength of internal stays in    
boilers is generally soon diminished by 
corrosion4 ,indeed1 a strain at all     
approaching that upon locomotive boilers
 would be very unsafe in the case  of   
marine boilers1 on account of the       
corrosion1 both internal and external1  
to which marine boilers are subject4    
,the stays should be small and numerous 

rather than large and few in number1 as1
 when large stays are employed1 it  is  
difficult to keep them tight at the     
ends1 and oxidation of the shell        
follows from leakage at the ends of the 
stays4 ,all boilers should be  proved1  
when new1 to twice or three times the   
pressure they are intended to  bear1 and
 they should be proved occasionally by  
the hand pump when in use1  to detect   
any weakness which corrosion may have   
occasioned4    #cjd4 ,q4--,will you     
describe the disposition of the stays in
 a marine  boiler8    ,a4--,if the      
pressure of steam be #bj lbs4 on the    
square inch1 which is a  very common    
pressure in tubular boilers1 there will 
be a pressure of #b1hhj  lbs4 on every  
square foot of flat surface2 so that if 
the strain upon the  stays is not to    
exceed #c1jjj lbs4 on the square inch of
 section1 there must  be nearly a square
 inch of sectional area of stay for     
every square foot of  flat surface on   
the top and bottom1 sides1 and ends of  

the boiler4 ,this  very much exceeds the
 proportion usually adopted2 and in     
scarcely any  instance are boilers      
stayed sufficiently to be safe when the 
shell is  composed of flat surfaces4    
,the furnaces should be stayed together 
with  bolts of the best scrap iron1     
#a-a_/d inch in diameter1 tapped through
 both  plates of the water space with   
thin nuts in each furnace2 and it is    
expedient to make the row of stays1     
running horizontally near the level of  
the bars1 sufficiently low to come      
beneath the top of the bars1 so as to be
  shielded from the action of the fire1 
with which view they should follow  the 
inclination of the bars4 ,the row of    
stays between the level of the bars  and
 the top of the furnace should be as    
near the top of the furnace as will     
consist with the functions they have to 
perform1 so as to be removed as far  as 
possible from the action of the heat2   
and to support the furnace top1  cross  
bars may either be adopted1 to which the

 top is secured with bolts1  as in the  
case of locomotives1 or stays tapped    
into the furnace top1 with a  thin nut  
beneath1 may be carried to the top of   
the boiler2 but very little  dependence 
can be put in such stays as stays for   
keeping down the top of  the boiler2 and
 the top of the boiler must1 therefore1 
be stayed nearly as  much as if the     
stays connecting it with the furnace    
crowns did not exist4  ,the large rivets
 passing through thimbles1 sometimes    
used as stays for  water spaces or      
boiler shells1 are objectionable2 as1   
from the great amount  of hammering such
 rivets have to receive to form the     
heads1 the iron  becomes crystalline1 so
 that the heads are liable to come off1 
and1 indeed1  sometimes fly off in the  
act of being formed4 ,if such a fracture
 occurs  between the boilers after they 
are seated in their place1 or in any    
position not accessible from the        
outside1 it will in general be necessary
  to empty the faulty boiler1 and repair

 the defect from the inside4    #cje4   
,q4--,what should be the pitch or       
numerical distribution of the stays8    
,a4--,the stays1 where the sides of the 
boiler are flat1 and the pressure  of   
the steam is from #bj to #cj lbs41      
should be pitched about a foot or #ah   
inches asunder2 and in the wake of the  
tubes1 where stays cannot be carried    
across to connect the boiler sides1     
angle iron ribs1 like the ribs of a     
ship1 should be riveted to the interior 
of the boiler1 and stays of greater     
strength than the rest should pass      
across1 above1 and below the tubes1 to  
which the angle irons would communicate 
the strain4 ,the whole of the long      
stays within a boiler should be firmly  
riveted to the shell1 as if built  with 
and forming a part of it2 as1 by the    
common method of fixing them in  by     
means of cutters1 the decay or          
accidental detachment of a pin or cutter
  may endanger the safety of the boiler4
 ,wherever a large perforation in the   

shell of any circular boiler occurs1 a  
sufficient number of stays should be    
put across it to maintain the original  
strength2 and where stays are           
intercepted by the root of the funnel1  
short stays in continuation of them     
should be placed inside4        ,,boiler
 ,,explosions4    #cjf4 ,q4--,what is   
the chief cause of boiler explosions8   
,a4--,the chief cause of boiler         
explosions is1 undoubtedly1 too great a 
pressure of steam1 or an insufficient   
strength of boiler2 but many  explosions
 have also arisen from the flues having 
been suffered to become  red hot4 ,if   
the safety valve of a boiler be         
accidentally jammed1 or if the  plates  
or stays be much worn by corrosion1     
while a high pressure of steam  is      
nevertheless maintained1 the boiler     
necessarily bursts2 and if1 from an     
insufficiency of water in the boiler1 or
 from any other cause1 the flues  become
 highly heated1 they may be forced down 
by the pressure of the steam1  and a    

partial explosion may be the result4    
,the worst explosion is where the  shell
 of the boiler bursts2 but the collapse 
of a furnace or flue is also  very      
disastrous generally to the persons in  
the engine room2 and sometimes  the     
shell bursts and the flues collapse at  
the same time2 for if the flues  get red
 hot1 and water be thrown upon them     
either by the feed pump or  otherwise1  
the generation of steam may be too rapid
 for the safety valve to  permit its    
escape with sufficient facility1 and the
 shell of the boiler  may1 in           
consequence1 be rent asunder4 ,sometimes
 the iron of the flues  becomes highly  
heated in consequence of the improper   
configuration of the  parts1 which1 by  
retaining the steam in contact with the 
metal1 prevents  the access of the      
water3 the bottoms of large flues1 upon 
which the flame  beats down1 are very   
liable to injury from this cause2 and   
the iron of  flues thus acted upon may  
be so softened that the flues will      

collapse  upward with the pressure of   
the steam4 ,the flues of boilers may    
also become  red hot in some parts from 
the attachment of scale1 which1 from its
  imperfect conducting power1 will cause
 the iron to be unduly heated2 and if   
the scale be accidentally detached1 a   
partial explosion may occur in          
consequence4    #cjg4 ,q4--,does the    
contact of water with heated metal      
occasion an  instantaneous generation of
 steam8    ,a4--,it is found that a     
sudden disengagement of steam does not  
immediately  follow the contact of water
 with the hot metal1 for water thrown   
upon red  hot iron is not immediately   
converted into steam1 but assumes the   
spheroidal form and rolls about in      
globules over the surface4 ,these       
globules1 however high the temperature  
of the metal may be on which they  are  
placed1 never rise above the temperature
 of #bje1 and give off but very  little 
steam2 but if the temperature of the    
metal be lowered1 the water  ceases to  

retain the spheroidal form1 and comes   
into intimate contact with  the metal1  
whereby a rapid disengagement of steam  
takes place4 ,if water be  poured into a
 very hot copper flask1 the flask may be
 corked up1 as there  will be scarce any
 steam produced so long as the high     
temperature is  maintained2 but so soon 
as the temperature is suffered to fall  
below #cej  or #djj1 the spheroidal     
condition being no longer maintainable1 
steam is  generated with rapidity1 and  
the cork will be projected from the     
mouth of  the flask with great force4   
#cjh4 ,q4--,what precautions can be     
taken to prevent boiler explosions8     
,a4--,one useful precaution against the 
explosion of boilers from too great  an 
internal pressure1 consists in the      
application of a steam gauge to each    
boiler1 which will make the existence of
 any undue pressure in any of the       
boilers immediately visible2 and every  
boiler should have a safety valve of    
its own1 the passage leading to which   

should have no connection with the      
passage leading to any of the stop      
valves used to cut off the connection   
between the boilers2 so that the action 
of the safety valve may be made         
independent of the action of the stop   
valve4 ,in some cases stop valves have  
jammed1 or have been carried from their 
seats into the mouth of the pipe        
communicating between them1 and the     
action of the safety valves should be   
rendered independent of all such        
accidents4 ,safety valves1 themselves1  
sometimes stick fast from corrosion1    
from the spindles becoming bent1 from  a
 distortion of the boiler top with a    
high pressure1 in consequence of  which 
the spindles become jammed in the       
guides1 and from various other  causes  
which it would be tedious to enumerate2 
but the inaction of the  safety valves  
is at once indicated by the steam gauge1
 and when discovered1  the blow through 
valves of the engine and blow off cocks 
of the boiler  should at once be opened1

 and the fires raked out4 ,a cone in the
 ball of  the waste steam pipe to send  
back the water carried upward by the    
steam1  should never be inserted2 as in 
some cases this cone has become loose1  
and  closed up the mouth of the waste   
steam pipe1 whereby the safety valves   
being rendered inoperative1 the boiler  
was in danger of bursting4    #cji4     
,q4--,may not danger arise from         
excessive priming8    ,a4--,if the water
 be carried out of the boiler so rapidly
 by priming that  the level of the water
 cannot be maintained1 and the flues or 
furnaces are  in danger of becoming red 
hot1 the best plan is to open every     
furnace door  and throw in a few buckets
 full of water upon the fire1 taking    
care to  stand sufficiently to the one  
side to avoid being scalded by the rush 
of  steam from the furnace4 ,there is no
 time to begin drawing the fires in such
  an emergency1 and by this treatment   
the fires1 though not altogether        
extinguished1 will be rendered incapable

 of doing harm4 ,if the flues be        
already red hot1 on no account must cold
 water be suffered to enter the  boiler1
 but the heat should be maintained in   
the furnaces1 and the blow off  cocks be
 opened1 or the mud hole doors loosened1
 so as to let all the water  escape2 but
 at the same time the pressure must be  
kept quite low in the  boiler1 so that  
there will be no danger of the hot flues
 collapsing with  the pressure of the   
steam4    #caj4 ,q4--,are plugs of      
fusible metal useful in preventing      
explosions8    ,a4--,plugs of fusible   
metal were at one time in much repute as
 a  precaution against explosion1 the   
metal being so compounded that it melted
  with the heat of high pressure steam2 
but the device1 though ingenious1 has   
not been found of any utility in        
practice4 ,the basis of fusible metal is
  mercury1 and it is found that the     
compound is not homogeneous1 and that   
the  mercury is forced by the pressure  
of the steam out of the interstices of  

the metal combined with it1 leaving a   
porous metal which is not easily        
fusible1 and which is1 therefore1 unable
 to perform its intended function4  ,in 
locomotives1 however1 and also in some  
other boilers1 a lead rivet is  inserted
 with advantage in the crown of the fire
 box1 which is melted out  if the water 
becomes too low1 and thus gives notice  
of the danger4    #caa4 ,q4--,may not   
explosion occur in marine boilers from  
the accumulation  of salt on the flues8 
,a4--,yes1 in marine boilers this is a  
constant source of danger1 which is     
only to be met by attention on the part 
of the engineer4 ,if the water in  the  
boiler be suffered to become too salt1  
an incrustation of salt will  take place
 on the furnaces1 which may cause them  
to become red hot1 and  they may then be
 collapsed even by their own weight     
aided by a moderate  pressure of steam4 
,the expedients which should be adopted 
for preventing  such an accumulation of 
salt from taking place within the boiler

 as will be  injurious to it1 properly  
fall under the head of the management of
 steam  boilers1 and will be explained  
in a subsequent chapter4                
,,chapter ,,vi4    ,,proportions ,,of   
,,engines4           99       99        
99       99       99    ,,steam         
,,passages4    #cab4 ,q4--,what size of 
orifice is commonly allowed for the     
escape of the  steam through the safety 
valve in low pressure engines8          
,a4--,about #j4h of a circular inch per 
horse power1 or a circular inch per     
#a-a_/d horse power4 ,the following     
rule1 however1 will give the dimensions 
suitable for all kinds of engines1      
whether high or low pressure3--multiply 
the square of the diameter of the       
cylinder in inches by the speed of the  
piston in feet per minute1 and divide   
the product by #cge times the pressure  
on the boiler per square inch2 the      
quotient is the proper area of the      
safety valve in square inches4 ,this    
rule of course supposes that the        

evaporating surface has been properly   
proportioned to the engine power4       
#cac4 ,q4--,is this rule applicable to  
locomotives8    ,a4--,it is applicable  
to high pressure engines of every kind4 
,the  dimensions of safety valves1      
however1 in practice are very variable1 
being  in some cases greater1 and in    
some cases less1 than what the rule     
gives1  the consideration being         
apparently as often what proportions    
will best  prevent the valve from       
sticking in its seat1 as what           
proportions will  enable the steam to   
escape freely4 ,in ,bury's locomotives1 
the safety valve  was generally #b-a_/b 
inches diameter for all sizes of boiler1
 and the valve  was kept down by a lever
 formed in the proportion of #e to #a1  
fitted at one  end with a ,salter's     
balance4 ,as the area of the valve was  
#e square inches1  the number of pounds 
shown on the spring balance denoted the 
number of  pounds pressure on each      
square inch of the boiler4    #cad4     

,q4--,is there only one safety valve in 
a locomotive boiler8    ,a4--,there are 
always two4    #cae4 ,q4--,and are they 
always pressed down by a spring balance1
 and never  by weights8    ,a4--,they   
are never pressed down by weights2 in   
fact1 weights would not  answer on a    
locomotive at all1 as they would jump up
 and down with the  jerks or jolts of   
the train1 and cause much of the steam  
to escape4 ,in land  and marine boilers1
 however1 the safety valve is always    
kept down by  weights2 but in steam     
vessels a good deal of steam is lost in 
stormy  weather by the opening of the   
valve1 owing to the inertia of the      
weights  when the ship sinks suddenly in
 the deep recess between the waves4     
#caf4 ,q4--,what other sizes of safety  
valves are used in locomotives8         
,a4--,some are as large as #d inches    
diameter1 giving #ab square inches of   
area2 and others are as small as        
#a-c_/af inch diameter1 giving #a square
 inch  of area4    #cag4 ,q4--,and are  

these valves all pressed down by a      
,salter's spring  balance8    ,a4--,in  
the great majority of cases they are so1
 and the lever by which  they are       
pressed down is generally graduated in  
the proportion of the area  of the valve
 to unity2 that is1 in the case of a    
valve of #ab inches area1  the long end 
of the lever to which the spring balance
 is attached is #ab  times the length of
 the short end1 so that the weight or   
pressure on the  balance shows the      
pressure per square inch on the boiler4 
,in some cases1  however1 a spiral      
spring1 and in other cases a pile of    
elliptical springs1  is placed directly 
upon the top of the valve1 and it       
appears desirable that  one of the      
valves at least should be loaded in this
 manner4 ,it is difficult  when the     
lever is divided in such a proportion as
 #ab to #a1 to get  sufficient lift of  
the valve without a large increase of   
pressure on the  spring2 and it appears 
expedient1 therefore1 to employ a       

shorter lever1  which involves either a 
reduction in the area of the valve1 or  
an increased  strength in the spring4   
#cah4 ,q4--,what are the proper         
dimensions of the steam passages8       
,a4--,in slow working engines the common
 size of the cylinder passages is  one  
twenty-fifth of the area of the         
cylinder1 or one fifth of the diameter  
of the cylinder1 which is the same      
thing4 ,this proportion corresponds very
  nearly with one square inch per horse 
power when the length of the cylinder   
is about equal to its diameter2 and one 
square inch of area per horse power  for
 the cylinder ports and eduction        
passages answers very well in the case  
of engines working at the ordinary speed
 of #bbj feet per minute4 ,the area  of 
the steam pipe is usually made less than
 the area of the eduction pipe1         
especially when the engine is worked    
expansively1 and with a considerable    
pressure of steam4 ,in the case of      
ordinary condensing engines1 however1   

working with the usual pressure of from 
#d to #h lbs4 above the atmosphere1  the
 area of the steam pipe is not less than
 a circular inch per horse  power4 ,in  
such engines the diameter of the steam  
pipe may be found by the  following     
rule3 divide the number of nominal horse
 power by #j4h and extract  the square  
root of the quotient1 which will be the 
internal diameter of the  steam pipe4   
#cai4 ,q4--,will you explain by what    
process of computation these            
proportions are arrived at8    ,a4--,the
 size of the steam pipe is so regulated 
that there will be no  material         
disparity of pressure between the       
cylinder and boiler2 and in  fixing the 
size of the eduction passage the same   
object is kept in view4  ,when the      
diameter of the cylinder and the        
velocity with which the piston  travels 
are known1 it is easy to tell what the  
velocity of the steam in the  steam pipe
 will be2 for if the area of the        
cylinder be #be times greater  than that

 of the steam pipe1 the steam in the    
steam pipe must travel #be  times faster
 than the piston1 and the difference of 
pressure requisite to  produce this     
velocity of the steam can easily be     
ascertained1 by finding  what height a  
column of steam must be to give that    
velocity1 and what the  weight or       
pressure is of such a column4 ,in       
practice1 however1 this  proportion is  
always exceeded from the condensation of
 steam in the pipe4    #cbj4 ,q4--,if   
the relation you have mentioned subsist 
between the area of  the steam passages 
and the velocity of the piston1 then the
 passages must  be larger when the      
piston travels very rapidly8            
,a4--,and they are so made4 ,the area of
 the ports of locomotive engines is     
usually so proportioned as to be from   
#a_/ajth to #a_/hth the area of the     
cylinder--in some cases even as much as 
#a_/fth2 and in all high speed  engines 
the ports should be very large1 and the 
valve should have a good  deal of travel

 so as to open the port very quickly4   
,the area of port which  it appears     
advisable to give to modern engines of  
every description1 is  expressed by the 
following rule3--multiply the area of   
the cylinder in  square inches by the   
speed of the piston in feet per minute1 
and divide the  product by #d1jjj2 the  
quotient is the area of each cylinder   
port in square  inches4 ,this rule gives
 rather more than a square inch of port 
per nominal  horse power to condensing  
engines working at the ordinary speed2  
but the  excess is but small1 and is    
upon the right side4 ,for engines       
travelling  very fast it gives a good   
deal more area than the common          
proportion1 which  is too small in      
nearly every case4 ,in locomotive       
engines the eduction pipe  passes into  
the chimney and the force of the issuing
 steam has the effect  of maintaining a 
rapid draught through the furnace as    
before explained4 ,the  orifice of the  
waste steam pipe1 or the blast pipe as  

it is termed1 is much  contracted in    
some engines with the view of producing 
a fiercer draught1  and an area of      
#a_/bb;d of the cylinder is a common    
proportion2 but this is as  much        
contraction as should be allowed1 and is
 greater than is advisable4    #cba4    
,q4--,in engines moving at a high rate  
of speed1 you have stated that  it is   
important to give the valve lead1 or in 
other words to allow the  steam to      
escape before the end of the stroke8    
,a4--,yes1 this is very important1 else 
the piston will have to force out  the  
steam from the cylinder1 and will be    
much resisted4 ,near the end of the     
stroke the piston begins to travel      
slowly1 and if the steam be then        
permitted to escape1 very little of the 
effective stroke is lost1 and time  is  
afforded to the steam1 before the motion
 of the piston is again  accelerated1 to
 make its escape by the port4 ,in some  
locomotives1 from  inattention to this  
adjustment1 and from a contracted area  

of tube section1  which involved a      
strong blast1 about half the power of   
the engine has been  lost2 but in more  
recent engines1 by using enlarged ports 
and by giving  sufficient lead1 this    
loss has been greatly diminished4       
#cbb4 ,q4--,what do you call sufficient 
lead8    ,a4--,in fast going engines ,i 
would call it sufficient lead1 when the 
eduction port was nearly open at the end
 of the stroke4    #cbc4 ,q4--,can you  
give any example of the benefit of      
increasing the lead8    ,a4--,the early 
locomotives were made with very little  
lead1 and the  proportions were in fact 
very much the same as those previously  
existing in  land engines4 ,about #ahcb1
 the benefits of lap upon the valve1    
which had  been employed by ,boulton and
 ,watt more than twenty years before1   
were  beginning to be pretty generally  
apprehended2 and1 in the following year1
  this expedient of economy was applied 
to the steamer ,manchester1 in the      
,clyde1 and to some other vessels1 with 

very marked success4 ,shortly after     
this time1 lap began to be applied to   
the valves of locomotives1 and it was   
found that not only was there a benefit 
from the operation of expansion1  but   
that there was a still greater benefit  
from the superior facility of  escape   
given to the steam1 inasmuch as the     
application of lap involved the         
necessity of turning the eccentric round
 upon the shaft1 which caused the       
eduction to take place before the end of
 the stroke4 ,in #ahdj1 one of the      
engines of the ,liverpool and           
,manchester ,railway was altered so as  
to have #a  inch lap on the valve1 and  
#a inch opening on the eduction side at 
the end  of the stroke1 the valve having
 a total travel of #d-a_/d inches4 ,the 
consumption of fuel per mile fell from  
#cf4c lbs4 to #bh4f lbs1 or about #be   
per cent41 and a softer blast sufficed4 
,by using larger exhaust passages1      
larger tubes1 and closer fire bars1 the 
consumption was subsequently  brought   

down to #ae lbs4 per mile4        ,,air 
,,pump1 ,,condenser1 ,,and ,,hot ,,and  
,,cold ,,water ,,pumps4    #cbd4        
,q4--,will you state the proper         
dimensions of the air pump and          
condenser in laud and marine engines8   
,a--,mr4 ,watt made the air pump of his 
engine half the diameter of the         
cylinder and half the stroke1 or one    
eighth of the capacity1 and the         
condenser was usually made about the    
same size as the air pump2 but as the   
pressure of the steam has been increased
 in all modern engines1 it is  better to
 make the air pump a little larger than 
this proportion4 #j4f of  the diameter  
of the cylinder and half the stroke     
answers very well1 and the  condenser   
may be made as large as it can be got   
with convenience1 though  the same size 
as the air pump will suffice4    #cbe4  
,q4--,are air pumps now sometimes made  
double acting8    ,a4--,most of the     
recent direct acting marine engines for 
driving the screw  are fitted with a    

double acting air pump1 and when the air
 pump is double  acting1 it need only be
 about half the size that is necessary  
when it is  single acting4 ,it is single
 acting in nearly every case1 except the
 case of  direct acting screw engines of
 recent construction4    #cbf4          
,q4--,what is the difference between a  
single and a double acting air  pump8   
,a4--,the single acting air pump expels 
the air and water from the  condenser   
only in the upward stroke of the pump1  
whereas a double acting  air pump expels
 the air and water both in the upward   
and downward stroke4  ,it has1          
therefore1 to be provided with inlet and
 outlet valves at both  ends1 whereas   
the single acting pump has only to be   
provided with an inlet  or foot valve1  
as it is termed1 at the bottom1 and with
 an outlet or  delivery valve1 as it is 
termed1 at the top4 ,the single acting  
air pump  requires to be provided with a
 valve or valves in the piston or bucket
 of  the pump1 to enable the air and    

water lying below the bucket when it    
begins  to descend1 and which have      
entered from the condenser during the   
upward  stroke1 to pass through the     
bucket into the space above it during   
the  downward stroke1 from whence they  
are expelled into the atmosphere on the 
upward stroke succeeding4 ,but in the   
double acting air pump no valve is      
required in the piston or bucket of the 
pump1 and all that is necessary is  an  
inlet and outlet valve at each end4     
#ccg4 ,q--,what are the dimensions of   
the foot and discharge valves of the    
air pump8    ,a4--,the area through the 
foot and discharge valves is usually    
made equal  to one fourth of the area of
 the air pump1 and the diameter of the  
waste  water pipe is made one fourth of 
the diameter of the cylinder1 which     
gives  an area somewhat less than that  
of the foot and discharge valve         
passages4  ,but this proportion only    
applies in slow engines4 ,in fast       
engines1 with the  air pump bucket      

moving as fast as the piston1 the area  
through the foot and  discharge valves  
should be equal to the area of the pump 
itself1 and the  waste water pipe should
 be of about the same dimensions4       
#cbh4 ,q4--,you have stated that double 
acting air pumps need only be of  half  
the size of single acting ones4 ,does   
that relation hold at all speeds8       
,a4--,it holds at all speeds if the     
velocity of the pump buckets are in     
each case the same2 but it does not hold
 if the engine with the single  acting  
pump works slowly1 and the engine with  
the double acting pump moves  rapidly1  
as in the case of direct acting screw   
engines4 ,all pumps moving at  a high   
rate of speed lose part of their        
efficiency1 and such pumps should       
therefore be of extra size4    #cbi4    
,q4--,how do you estimate the quantity  
of water requisite for  condensation8   
,a4--,mr4 ,watt found that the most     
beneficial temperature of the hot well  
of his engines was #ajj degrees4 ,if1   

therefore1 the temperature of the steam 
be #bab1 and the latent heat #a1jjj1    
then #a1bab may be taken to represent   
the heat contained in the steam1 or     
#a1aab if we deduct the temperature of  
the hot well4 ,if the temperature of the
 injection water be #ej1 then #ej       
degrees of cold are available for the   
abstraction of heat2 and as the total   
quantity of heat to be abstracted is    
that requisite to raise the quantity  of
 water in the steam #a1aab degrees1 or  
#a1aab times that quantity one  degree1 
it would raise one fiftieth of this1 or 
#bb4bd times the quantity of  water in  
the steam1 #ej degrees4 ,a cubic inch of
 water therefore raised into  steam will
 require #bb4bd cubic inches of water at
 #ej degrees for its  condensation1 and 
will form therewith #bc4bd cubic inches 
of hot water at  #ajj degrees4 ,mr4     
,watt's practice was to allow about a   
wine pint 7#bh4i cubic  inches7 of      
injection water1 for every cubic inch of
 water evaporated from  the boiler4     

#ccj4 ,q4--,is not a good vacuum in an  
engine conducive to increased power8    
,a4--,it is4    #cca4 ,q4--,and is not  
the vacuum good in the proportion in    
which the  temperature is low1 supposing
 there to be no air leaks8    ,a4--,yes4
    #ccb4 ,q4--,then how could ,mr4     
,watt find a temperature of #ajj in the 
water  drawn from the condenser1 to be  
more beneficial than a temperature of   
#gj  or #hj1 supposing there to be an   
abundant supply of cold water8    #ccc4 
,a4--,because the superior vacuum due to
 a temperature of #gj or #hj  involves  
the admission of so much cold water into
 the condenser1 which has  afterward to 
be pumped out in opposition to the      
pressure of the atmosphere1  that the   
gain in the vacuum does not equal the   
loss of power occasioned by  the        
additional load upon the pump1 and there
 is therefore a clear loss by  the      
reduction of the temperature below #ajj1
 if such reduction be caused by  the    
admission of an additional quantity of  

water4 ,if the reduction of             
temperature1 however1 be caused by the  
use of colder water1 there is a gain    
produced by it1 though the gain will    
within certain limits be greater if     
advantage be taken of the lowness of the
 temperature to diminish the  quantity  
of injection4    #ccd4 ,q4--,how do you 
determine the proper area of the        
injection orifice8    ,a4--,the area of 
the injection orifice proper for any    
engine can easily be  told when the     
quantity of water requisite to condense 
the steam is known1  and the pressure is
 specified under which the water enters 
the condenser4  ,the vacuum in the      
condenser may be taken at #bf inches of 
mercury1 which is  equivalent to a      
column of water #bi4d ft4 high1 and the 
square root of #bi4d  multiplied by     
#h4jba is #dc4ae1 which is the velocity 
in feet per second that  a heavy body   
would acquire in falling #bi4d ft41 or  
with which the water  would enter the   
condenser4 ,now1 if a cubic foot of     

water evaporated per  hour be equivalent
 to an actual horse power1 and #bh4i    
cubic inches of water  be requisite for 
the condensation of a cubic inch of     
water in the form of  steam1 #bh4i cubic
 feet of condensing water per horse     
power per hour1 or  #ac4ije cubic inches
 per second1 will be necessary for the  
engine1 and the  size of the injection  
orifice must be such that this quantity 
of water  flowing with the velocity of  
#dc4ae ft4 per second1 or #eag4h inches 
per  second1 will gain admission to the 
condenser4 ,dividing1 therefore1        
#ac4ije1  the number of cubic inches to 
be injected1 by #eag4h1 the velocity of 
influx  in inches per second1 we get    
#j4jbfhe for the area of the orifice in 
square  inches2 but inasmuch as it has  
been found by experiment that the actual
  discharge of water through a hole in a
 thin plate is only six tenths of the   
theoretical discharge on account of the 
contracted vein1 the area of the        
orifice must be increased in the        

proportion of such diminution of effect1
  or be made #j4jddge1 or #a_/bb;d of a 
square inch per horse power4 ,this1 it  
will be remarked1 is the theoretical    
area required per actual horse power2   
but as the friction and contractions in 
the pipe further reduce the  discharge1 
the area is made #a_/aeth of a square   
inch per actual horse power1  or rather 
per cubic foot of water evaporated from 
the boiler4    #cce4 ,q4--,cannot the   
condensation of the steam be            
accomplished by any  other means than by
 the admission of cold water into the   
condenser8    ,a4--,it may be           
accomplished by the method of external  
cold1 as it is  called1 which consists  
in the application of a large number of 
thin  metallic surfaces to the          
condenser1 on the one side of which the 
steam  circulates1 while on the other   
side there is a constant current of cold
  water1 and the steam is condensed by  
coming into contact with the cold       
surfaces1 without mingling with the     

water used for the purpose of           
refrigeration4 ,the first kind of       
condenser employed by ,mr4 ,watt was    
constructed after this fashion1 but he  
found it in practice to be  inconvenient
 from its size1 and to become furred up 
or incrusted when the  water was bad1   
whereby the conducting power of the     
metal was impaired4 ,he  therefore      
reverted to the use of the jet of cold  
water1 as being upon the  whole         
preferable4 ,the jet entered the        
condenser instead of the cylinder as    
was the previous practice1 and this     
method is now the one in common use4    
,some few years ago1 a good number of   
steam vessels were fitted with ,hall's  
condensers1 which operated on the       
principle of external cold1 and which   
consisted of a faggot of small copper   
tubes surrounded by water2 but the  use 
of those condensers has not been        
persisted in1 and most of the vessels   
fitted with them have returned to the   
ordinary plan4    #ccf4 ,q4--,you stated

 that the capacity of the feed pump was 
#a_/bdjth of the  capacity of the       
cylinder in the case of condensing      
engines1--the engine  being double      
acting and the pump single acting1--and 
that in high pressure  engines the      
capacity of the pump should be greater  
in proportion to the  pressure of the   
steam4 ,can you give any rule that will 
express the proper  capacity for the    
feed pump at all pressures8             
,a4--,that will not be difficult4 ,in   
low pressure engines the pressure in    
the boiler may be taken at #e lbs4 above
 the atmospheric pressure1 or #bj  lbs4 
altogether2 and as high pressure steam  
is merely low pressure steam  compressed
 into a smaller compass1 the size of the
 feed pump in relation to  the size of  
the cylinder must obviously vary in the 
direct proportion of  the pressure2 and 
if it be #a_/bdjth of the capacity of   
the cylinder when the  total pressure of
 the steam is #bj lbs41 it must be      
#a_/abjth of the capacity  of the       

cylinder when the pressure is #dj lbs4  
per square inch1 or #be lbs4  per square
 inch above the atmospheric pressure4   
,this law of variation is  expressed by 
the following rule3--multiply the       
capacity of the cylinder in  cubic      
inches by the total pressure of the     
steam in lbs4 per square inch1 or  the  
pressure per square inch on the safety  
valve plus #ae1 and divide the  product 
by #d1hjj2 the quotient is the capacity 
of the feed pump in cubic  inches1 when 
the feed pump is single acting and the  
engine double acting4  ,if the feed pump
 be double acting1 or the engine single 
acting1 the  capacity of the pump must  
just be one half of what is given by    
this rule4    #ccg4 ,q4--,but should not
 some addition be made to the size of   
pump thus  obtained if the pump works at
 a high rate of speed8    ,a4--,no2 this
 rule makes allowance for defective     
action4 ,all pumps lift  much less water
 than is due to the size of their       
barrels and the number of  their        

strokes4 ,moderately good pumps lose #ej
 per cent4 of their theoretical  effect1
 and bad pumps #hj per cent4    #cch4   
,q4--,to what is this loss of effect to 
be chiefly ascribed8    ,a4--,mainly to 
the inertia of the water1 which1 if the 
pump piston be  drawn up very rapidly1  
cannot follow it with sufficient        
rapidity2 so that  there may be a vacant
 space between the piston and the water2
 and at the  return stroke the momentum 
of the water in the pipe expends itself 
in  giving a reverse motion to the      
column of water approaching the pump4   
,messrs4 ,kirchweger and ,prusman1 of   
,hanover1 have investigated this subject
  by applying a revolving cock at the   
end of a pipe leading from an elevated  
cistern containing water1 and the water 
escaped at every revolution of the  cock
 in the same manner as if a pump were   
drawing it4 ,with a column of  water of 
#ag feet1 they found that at #hj        
revolutions of the cock per minute1  the
 water delivered per minute by the cock 

was #i4de gallons2 but with #adj        
revolutions of the cock per minute1 the 
water delivered per minute by the  cock 
was only #e4db gallons4 ,they           
subsequently applied an air vessel to   
the  pipe beside the cock1 when the     
discharge rose to #ab4i gallons per     
minute  with #hj revolutions1 and #ah4bh
 gallons with #adj revolutions4 ,air    
vessels  should therefore be applied to 
the suction side of fast moving pumps1  
and  this is now done with good results4
    #cci4 ,q4--,what are the usual      
dimensions of the cold water pump of    
land  engines8    ,a4--,if to condense a
 cubic inch of water raised into steam  
#bh4i cubic  inches of condensing water 
are required1 then the cold water pump  
ought to  be #bh4i times larger than the
 feed pump1 supposing that its losses   
were  equally great4 ,the feed pump1    
however1 is made sufficiently large to  
compensate for leaks in the boiler and  
loss of steam through the safety  valve1
 so that it will be sufficient if the   

cold water pump be #bd times  larger    
than the feed pump4 ,this ratio is      
preserved by the following rule3--      
multiply the capacity of the cylinder in
 cubic inches by the total pressure  of 
the steam per square inch1 or the       
pressure on the safety valve plus #ae1  
and divide the product by #bjj4 ,the    
quotient is the proper capacity of the  
cold water pump in cubic inches when the
 engine is double acting1 and the  pump 
single acting4        ,,fly ,,wheel4    
#cdj4 ,q4--,by what considerations do   
you determine the dimensions of the  fly
 wheel of an engine8    ,a4--,by a      
reference to the power generated1 each  
half stroke of the  engine1 and the     
number of half strokes that are         
necessary to give to the  fly wheel its 
standard velocity1 supposing the whole  
power devoted to that  object4 ,in      
practice the power resident in the fly  
varies from #b-a_/b to #f  times that   
generated each half stroke2 and if the  
weight of the wheel be  equal to the    

pressure on the piston1 its velocity    
must be such as it would  acquire by    
falling through a height equal to from  
#b-a_/b to #f times the  stroke1        
according to the purpose for which the  
engine is intended4 ,if a  very equable 
motion is required1 a heavier or swifter
 fly wheel must be  employed4    #cda4  
,q4--,what is ,boulton and ,watt's rule 
for fly wheels8    ,a4--,their rule is  
one which under any given circumstances 
fixes the  sectional area of the fly    
wheel rim1 and it is as                 
follows3--multiply #dd1jjj  times the   
square of the diameter of the cylinder  
in inches by the length of  the stroke  
in feet1 and divide this product by the 
product of the square of  the number of 
revolutions of the fly wheel per minute1
 multiplied by the  cube of its diameter
 in feet4 ,the quotient is the area of  
section of the  fly wheel rim in square 
inches4        ,,strengths ,,of ,,land  
,,engines4    #cdb4 ,q4--,can you give a
 rule for telling the proper thickness  

of the  cylinders of steam engines8     
,a4--,in low pressure engines the       
thickness of metal of the cylinder1 in  
engines of a medium size1 should be     
about #a_/djth of the diameter of the   
cylinder1 which1 with a pressure of     
steam of #bj lbs4 above the atmosphere1 
will occasion a strain of only #djj     
,lbs4 per square inch of section of the 
metal2 the thickness of the metal of the
 trunnion bearings of oscillating       
engines should be #a_/cb;d of the       
diameter of the cylinder1 and the       
breadth of  the bearing should be about 
half its diameter4 ,in high pressure    
engines the  thickness of the cylinder  
should be about #a_/afth its diameter1  
which1 with  a pressure of steam of #hj 
lbs4 upon the square inch1 will occasion
 a strain  of #fdj lbs4 upon the square 
inch of section of the metal2 and the   
thickness  of the metal of the trunnion 
bearings of high pressure oscillating   
engines  should be #a_/acth of the      
diameter of the cylinder4 ,the strength1

 however1 is  not the sole consideration
 in proportioning cylinders1 for they   
must be  made of a certain thickness1   
however small the pressure is within    
them1  that they may not be too fragile1
 and will stand boring4 ,while1 also1 an
  engine of #dj inches diameter would be
 about one inch thick1 the thickness    
would not be quite two inches in an #hj 
inch cylinder4 ,in fact there will be  a
 small constant added to the thickness  
for all diameters1 which will be        
relatively larger the smaller the       
cylinders become4 ,in the cylinders of  
,penn's #ab horse power engines1 the    
diameter of cylinder being #ba-a_/b     
inches1 the thickness of the metal is   
#i_/afths3 in ,penn's #dj inch          
cylinders1  the thickness is #a inch1   
and in the engines of the ,ripon1       
,pottinger1 and  ,indus1 by ,messrs4    
,miller1 ,ravenhill and ,co41 with      
cylinders #gf inches  diameter1 the     
thickness of the metal is #a-aa_/af4    
,these are all oscillating  engines4    

#cdc4 ,q4--,what is the proportion of   
the piston rod8    ,a4--,the diameter of
 the piston rod is usually made #a_/ajth
 of the diameter  of the cylinder1 or   
the sectional area of the piston rod is 
#a_/ajjth of the  area of the cylinder4 
,this proportion1 however1 is not       
applicable to  locomotive1 or even fast 
moving marine engines4 ,in locomotive   
engines the  piston rod is made #a_/gth 
of the diameter of the cylinder1 and it 
is obvious  that where the pressure on  
the piston is great1 the piston rod must
 be  larger than when the pressure on   
the piston is small4    #cdd4 ,q4--,what
 are the proper dimensions of the main  
links of a land beam  engine8           
,a4--,the sectional area of the main    
links in land beam engines is #a_/aacth 
of the area of the cylinder1 and the    
length of the main links is usually     
half the length of the stroke4    #cde4 
,q4--,what are the dimensions of the    
connecting rod of a land engine8        
,a4--,in land engines the connecting rod

 is usually of cast iron with a         
cruciform section3 the breadth across   
the arms of the cross is about #a_/bjth 
of the length of the rod1 the sectional 
area at the centre #a_/bhth of the  area
 of the cylinder1 and at the ends       
#a_/ceth of the area of the cylinder3   
the length of the rod is usually #c-a_/b
 times the length of the stroke4 ,it  is
 preferable1 however1 to make the       
connecting rod of malleable iron1 and   
then the dimensions will be those proper
 for marine engines4    #cdf4 ,q4--,what
 was ,mr4 ,watt's rule for the          
connecting rod8    ,a4--,some of his    
connecting rods were of iron and some of
 wood4 ,to  determine the thickness when
 of wood1 multiply the square of the    
diameter  of the cylinder in inches by  
the length of the stroke in feet1 and   
divide  the product by #bd4 ,extract the
 fourth root of the quotient1 which is  
the  thickness in inches4 ,for iron the 
rule is the same1 only the divisor was  
#eg4f instead of #bd4    #cdg4          

,q4--,what are the dimensions of the end
 studs of a land engine beam8           
,a4--,in low pressure engines the       
diameter of the end studs of the engine 
beam are usually made #a_/ith of the    
diameter of the cylinder when of cast   
iron1 and #a_/ajth when of wrought iron1
 which gives a load with low steam of   
about #ejj lbs4 per circular inch of    
transverse section2 but a larger size   
is preferable1 as with large bearings   
the brasses do not wear so rapidly  and 
the straps are not so likely to be burst
 by the bearings becoming oval4  ,these 
sizes1 as also those which immediately  
follow1 suppose the pressure  on the    
piston to be #ah lbs4 per circular inch4
    #cdh4 ,q4--,how is the strength of a
 cast iron gudgeon computed8    ,a4--,to
 find the proper size of a cast iron    
gudgeon adapted to sustain any  given   
weight3--multiply the weight in lbs4 by 
the intended length of  bearing         
expressed in terms of the diameter2     
divide the product by #ejj1 and  extract

 the square root of the quotient1 which 
is the diameter in inches4    #cdi4     
,q4--,what was ,mr4 ,watt's rule for the
 strength of gudgeons8                  
,a4--,supposing the gudgeon to be       
square1 then1 to ascertain the          
thickness1  multiply the weight resting 
on the gudgeon by the distance between  
the  trunnions1 and divide the product  
by #ccc4 ,extract the cube root of the  
quotient1 which is the thickness in     
inches4    #cej4 ,q4--,how do you find  
the proper strength for the cast iron   
beam of a  land engine8    ,a4--,if the 
force acting at the end of an engine    
beam be taken at #ah lbs4  per circular 
inch of the piston1 then the force      
acting at the middle will  be #cf lbs4  
per circular inch of the piston1 and the
 proper strength of the  beam at the    
centre will be found by the following   
rule3--divide the weight  in lbs4 acting
 at the centre by #bej1 and multiply the
 quotient by the  distance between the  
extreme centres4 ,to find the depth1 the

 breadth being  given3--divide this     
product by the breadth in inches1 and   
extract the  square root of the         
quotient1 which is the depth4 ,the depth
 of a land engine  beam at the ends is  
usually made one third of the depth at  
the centre 7the  depth at the centre    
being equal to the diameter of the      
cylinder in the case  of low pressure   
engines71 while the length is made equal
 to three times the  length of the      
stroke1 and the mean thickness #a_/ajhth
 of the length--the  width of the edge  
bead being about three times the        
thickness of the web4 ,in  many modern  
engines the force acting at the end of  
the beam is more than #ah  lbs4 per     
circular inch of the piston1 but the    
above rules are still  applicable by    
taking an imaginary cylinder with an    
area larger in the  proportion of the   
larger pressure4    #cea4 ,q4--,what was
 ,mr4 ,watt's rule for the main beams of
 his engines8    ,a4--,some of those    
beams were of wood and some of cast     

iron4 ,the wood  beams were so          
proportioned that the thickness was     
#a_/ehth of the  circumference1 and the 
depth #a_/cge4 ,the side of the beam1   
supposing it  square1 was found by      
multiplying the diameter of the cylinder
 by the length  of the stroke1 and      
extracting the cube root of the         
quotient1 which will be  the depth or   
thickness of the beam4 ,this rule allows
 a beam #af feet long to  bend #a_/hth  
of an inch1 and a beam #cb feet long to 
bend #a_/d of an inch4 ,for  cast iron  
beams the square of the diameter of the 
cylinder1 multiplied by  the length     
between the centres1 is equal to the    
square of the depth1  multiplied by the 
thickness4    #ceb4 ,q4--,what law does 
the strength of beams and shafts follow8
    ,a4--,in the case of beams subjected
 to a breaking force1 the strength with 
any given cohesion of the material will 
be proportional to the breadth1         
multiplied by the square of the depth2  
and in the case of revolving shafts     

exposed to a twisting strain1 the       
strength with any given cohesive power  
of  the material will be as the cube of 
the diameter4    #cec4 ,q4--,how is the 
strength of a cast iron shaft to resist 
torsion  determined8                    
,a4--,experiments upon the force        
requisite to twist off cast iron necks  
show that if the cube of the diameter of
 neck in inches be multiplied by  #hhj1 
the product will be the force of torsion
 which will twist them off  when acting 
at #f inches radius2 on this fact the   
following rule is founded3  ,to find the
 diameter of a cast iron fly wheel      
shaft3--multiply the square  of the     
diameter of the cylinder in inches1 by  
the length of the crank in  inches1 and 
extract the cube root of the product1   
which multiply by #j4cjbe1  and the     
result will be the proper diameter of   
the shaft in inches at the  smallest    
part1 when of cast iron4    #ced4       
,q4--,what was ,mr4 ,watt's rule for the
 necks of his crank shafts8             

,a4--,taking the pressure on the piston 
at #ab lbs4 pressure on the square      
inch1 and supposing this force to be    
applied at one foot radius1 divide the  
total pressure of the piston reduced to 
#a foot of radius by #ca4d1 and  extract
 the cube root of the quotient1 which is
 the diameter of the shaft3  or extract 
the cube root of #ac4g times the number 
of cubic feet of steam  required to make
 one revolution1 which is also the      
diameter of the shaft4    #cee4         
,q4--,can you give any rule for the     
strength of the teeth of wheels8        
,a4--,to find the proper dimensions for 
the teeth of a cast iron wheel3--       
multiply the diameter of the pitch      
circle in feet by the number of         
revolutions to be made per minute1 and  
reserve the product for a divisor2      
multiply the number of actual horses    
power to be transmitted by #bdj1 and    
divide the product by the above divisor1
 which will give the strength4 ,if  the 
pitch be given to find the breadth1     

divide the above strength by the  square
 of the pitch in inches2 or if the      
breadth be given1 then to find the      
pitch divide the strength by the breadth
 in inches1 and extract the square  root
 of the quotient1 which is the proper   
pitch in inches4 ,the length of  the    
teeth is usually about #e_/hths of the  
pitch4 ,pinions to work  satisfactorily 
should not have less than #cj or #dj    
teeth1 and where the  speed exceeds #bbj
 feet in the minute1 the teeth of the   
larger wheel should  be of wood1 made a 
little thicker1 to keep the strength    
unimpaired4    #cef4 ,q4--,what was ,mr4
 ,watt's rule for the pitch of wheels8  
,a4--,multiply five times the diameter  
of the larger wheel by the diameter  of 
the smaller1 and extract the fourth root
 of the product1 which is the  pitch4   
,,strength ,,of ,,marine ,,and          
,,locomotive ,,engines4    #ceg4        
,q4--,cannot you give some rules of     
strength which will be applicable       
whatever pressure may be employed8      

,a4--,in the rules already given1 the   
effective pressure may be reckoned at   
from #ah to #bj lbs4 upon every square  
inch of the piston1 as is usual in  land
 engines2 and if the pressure upon every
 square inch of the piston be  made     
twice greater1 the dimensions must just 
be those proper for an engine  of twice 
the area of piston4 ,it will not be     
difficult1 however1 to  introduce the   
pressure into the rules as an element of
 the computation1  whereby the result   
will be applicable both to high and low 
pressure  engines4    #ceh4 ,q4--,will  
you apply this mode of computation to a 
marine engine1 and  first find the      
diameter of the piston rod8    ,a4--,the
 diameter of the piston rod may be found
 by multiplying the  diameter of the    
cylinder in inches1 by the square root  
of the pressure on  the piston in lbs4  
per square inch1 and dividing by #ej1   
which makes the  strain #a_/gth of the  
elastic force4    #cei4 ,q4--,what will 
be the rule for the connecting rod1     

supposing it to be  of malleable iron8  
,a4--,the diameter of the connecting rod
 at the ends1 may be found by           
multiplying #j4jai times the square root
 of the pressure on the piston in  lbs4 
per square inch by the diameter of the  
cylinder in inches2 and the  diameter of
 the connecting rod in the middle may be
 found by the following  rule3--to      
#j4jjce times the length of the         
connecting rod in inches1 add #a1  and  
multiply the sum by #j4jai times the    
square root of the pressure on the      
piston in lbs4 per square inch1         
multiplied by the diameter of the       
cylinder  in inches4 ,the strain is     
equal to #a_/fth of the elastic force4  
#cfj4 ,q4--,how will you find the       
diameter of the cylinder side rods of a 
marine engine8    ,a4--,the diameter of 
the cylinder side rods at the ends may  
be found by  multiplying #j4jabi times  
the square root of the pressure on the  
piston in  lbs4 per square inch by the  
diameter of the cylinder2 and the       

diameter of  the cylinder side rods at  
the middle is found by the following    
rule3--to  #j4jjce times the length of  
the rod in inches1 add #a1 and multiply 
the sum  by #j4jabi times the square    
root of the pressure on the piston in   
lbs4 per  square inch1 multiplied by the
 diameter of the cylinder in inches2 the
  product is the diameter of each side  
rod at the centre in inches4 ,the       
strain upon the side rods is by these   
rules equal to #a_/fth of the elastic   
force4    #cfa4 ,q4--,how do you        
determine the dimensions of the crank8  
,a4--,to find the exterior diameter of  
the large eye of the crank when of      
malleable iron3--to #a4efa times the    
pressure of the steam upon the piston   
in lbs4 per square inch1 multiplied by  
the square of the length of the  crank  
in inches1 add #j4jjdid times the square
 of the diameter of the  cylinder in    
inches1 multiplied by the square of the 
number of lbs4 pressure  per square inch
 on the piston2 extract the square root 

of this quantity2  divide the result by 
#ge4ei times the square root of the     
length of the crank  in inches1 and     
multiply the quotient by the diameter of
 the cylinder in  inches2 square the    
product and extract the cube root of the
 square1 to  which add the diameter of  
the hole for the reception of the shaft1
 and the  result will be the exterior   
diameter of the large eye of the crank  
when of  malleable iron4 ,the diameter  
of the small eye of the crank may be    
found by  adding to the diameter of the 
crank pin #j4jbeba times the square root
 of  the pressure on the piston in lbs4 
per square inch1 multiplied by the      
diameter of the cylinder in inches4     
#cfb4 ,q4--,what will be the thickness  
of the crank web8    ,a4--,the thickness
 of the web of the crank1 supposing it  
to be continued  to the centre of the   
shaft1 would at that point be           
represented by the  following rule3--to 
#a4efa times the square of the length of
 the crank in  inches1 add #j4jjdid     

times the square of the diameter of the 
cylinder in  inches1 multiplied by the  
pressure on the piston in lbs4 per      
square inch2  extract the square root of
 the sum1 which multiply by the diameter
 of the  cylinder squared in inches1 and
 by the pressure on the piston in lbs4  
per  square inch2 divide the product by 
#i1jjj1 and extract the cube root of the
  quotient1 which will be the proper    
thickness of the web of the crank when  
of malleable iron1 supposing the web to 
be continued to the centre of the       
shaft4 ,the thickness of the web at the 
crank pin centre1 supposing it to be    
continued thither1 would be #j4jbb times
 the square root of the pressure on  the
 piston in lbs4 per square inch1        
multiplied by the diameter of the       
cylinder4 ,the breadth of the web of the
 crank at the shaft centre should be    
twice the thickness1 and at the pin     
centre #a-a_/b times the thickness of   
the  web2 the length of the large eye of
 the crank would be equal to the        

diameter of the shaft1 and of the small 
eye #j4jcge times the square root of    
the pressure on the piston in lbs4 per  
square inch1 multiplied by the  diameter
 of the cylinder4    #cfc4 ,q4--,will   
you apply the same method of computation
 to find the  dimensions of a malleable 
iron paddle shaft8    ,a4--,the method  
of computation will be as follows3--to  
find the dimensions  of a malleable iron
 paddle shaft1 so that the strain shall 
not exceed  #e_/fths of the elastic     
force1 or #e_/fths of the force iron is 
capable of  withstanding without        
permanent derangement of structure1     
which in tensile  strains is taken at   
#ag1hjj lbs4 per square inch3 multiply  
the pressure in  lbs4 per square inch on
 the piston by the square of the        
diameter of the  cylinder in inches1 and
 the length of the crank in inches1 and 
extract the  cube root of the product1  
which1 multiplied by #j4jhbfd1 will be  
the  diameter of the paddle shaft       
journal in inches when of malleable     

iron1  whatever the pressure of the     
steam may be4 ,the length of the paddle 
shaft  journal should be #a-a_/d times  
the diameter2 and the diameter of the   
part  where the crank is put on is often
 made equal to the diameter over the    
collars of the journal or bearing4      
#cfd4 ,q4--,how do you find the diameter
 of the crank pin8    ,a4--,the diameter
 of the crank pin in inches may be found
 by multiplying  #j4jbhcf times the     
square root of the pressure on the      
piston in lbs4 per  square inch1 by the 
diameter of the cylinder in inches4 ,the
 length of the  pin is usually about    
#i_/hth times its diameter1 and the     
strain if all thrown  upon the end of   
the pin will be equal to the elastic    
force2 but in ordinary  working1 the    
strain will only be equal to #a_/c;d of 
the elastic force4    #cfe4 ,q4--,what  
are the dimensions of the cross head8   
,a4--,if the length of the cross head be
 taken at #a4d times the diameter of    
the cylinder1 the dimensions of the     

cross head will be as follows3--the     
exterior diameter of the eye in the     
cross head for the reception of the     
piston rod1 will be equal to the        
diameter of the hole1 plus #j4jbhbg     
times  the cube root of the pressure on 
the piston in lbs4 per square inch1     
multiplied by the diameter of the       
cylinder in inches2 and the depth of the
  eye will be #j4jigi times the cube    
root of the pressure on the piston in   
lbs4 per square inch1 multiplied by the 
diameter of the cylinder in inches4     
,the diameter of each cross head journal
 will be #j4jagaf times the square  root
 of the pressure on the piston in lbs4  
per square inch1 multiplied by  the     
diameter of the cylinder in inches--the 
length of the journal being  #i_/hths   
its diameter4 ,the thickness of the web 
at centre will be #j4jbde  times the    
cube root of the pressure on the piston 
in lbs4 per square inch1  multiplied by 
the diameter of the cylinder in inches2 
and the depth of web  at centre will be 

#j4jiagh times the cube root of the     
pressure on the piston  in lbs4 per     
square inch1 multiplied by the diameter 
of the cylinder in  inches4 ,the        
thickness of the web at journal will be 
#j4jabb times the square  root of the   
pressure on the piston in lbs4 per      
square inch1 multiplied by  the diameter
 of the cylinder in inches2 and the     
depth of the web at journal  will be    
#j4jbjc times the square root of the    
pressure upon the piston in  lbs4 per   
square inch1 multiplied by the diameter 
of the cylinder in inches4  ,in these   
rules for the cross head1 the strain    
upon the web is #a_/b4bbe times  the    
elastic force2 the strain upon the      
journal in ordinary working is  #a_/b4cc
 times the elastic force2 and if the    
outer ends of the journals are  the only
 bearing points1 the strain is #a_/a4afe
 times the elastic force1  which is very
 little in excess of the elastic force4 
#cff4 ,q4--,how do you find the diameter
 of the main centre when  proportioned  

according to this rule8    ,a4--,the    
diameter of the main centre may be found
 by multiplying #j4jcfg  times the      
square root of the pressure upon the    
piston in lbs4 per square  inch1 by the 
diameter of the cylinder in inches1     
which will give the  diameter of the    
main centre journal in inches when of   
malleable iron1 and  the length of the  
main centre journal should be #a-a_/b   
times its diameter2  the strain upon the
 main centre journal in ordinary working
 will be about  #a_/b the elastic force4
    #cfg4 ,q4--,what are the proper     
dimensions of the gibs and cutters of an
  engine8    ,a4--,the depth of gibs and
 cutters for attaching the piston rod to
 the  cross head1 is #j4jceh times the  
cube root of the pressure of the steam  
on  the piston in lbs4 per square inch1 
multiplied by the diameter of the       
cylinder2 and the thickness of the gibs 
and cutters is #j4jjg times the cube    
root of the pressure on the piston in   
lbs4 per square inch1 multiplied by  the

 diameter of its cylinder4 ,the depth of
 the cutter through the piston is       
#j4jag times the square root of the     
pressure on the piston in lbs4 per      
square inch1 multiplied by the diameter 
of the cylinder in inches2 and the      
thickness of the cutter through the     
piston is #j4jjg times the square root  
of the pressure on the piston in lbs4   
per square inch1 multiplied by the      
diameter of the cylinder4    #cfh4      
,q4--,are not some of the parts of an   
engine constructed according to  these  
rules too weak1 when compared with the  
other parts8    ,a4--,it is obvious1    
from the varying proportions subsisting 
in the  different parts of the engine   
between the strain and the elastic      
force1  that in engines proportioned by 
these rules--which represent            
nevertheless  the average practice of   
the best constructors--some of the parts
 must  possess a considerable excess of 
strength over other parts1 and it       
appears  expedient that this disparity  

should be diminished1 which may best be 
done  by increasing the strength of the 
parts which are weakest2 inasmuch as the
  frequent fracture of some of the parts
 shows that the dimensions at present   
adopted for those parts are scarcely    
sufficient1 unless the iron of which    
they are made is of the best quality4   
,at the same time it is quite certain1  
that engines proportioned by these rules
 will work satisfactorily where  good   
materials are employed2 but it is       
important to know in what parts good    
materials and larger dimensions are the 
most indispensable4 ,in many of the     
parts1 moreover1 it is necessary that   
the dimensions should be proportioned   
to meet the wear and the tendency to    
heat1 instead of being merely           
proportioned to obtain the necessary    
strength2 and the crank pin is one of   
the parts which requires to be large in 
diameter1 and as long as possible  in   
the bearing1 so as to distribute the    
pressure1 and prevent the  disposition  

to heat which would otherwise exist4    
,the cross head journals  also should be
 long and large2 for as the tops of the 
side rods have little  travel1 the oil  
is less drawn into the bearings than if 
the travel was  greater1 and is being   
constantly pressed out by the punching  
strain4 ,this  strain should therefore  
be reduced as far as possible by its    
distribution  over a large surface4 ,in 
the rules which are contained in the    
answers to  the ten preceding questions 
7#ceh to #cfg7 the pressure on the      
piston in lbs4  per square inch is taken
 as the sum of the pressure of steam in 
the boiler  and of the vacuum2 the      
latter being assumed to be #ae lbs4 per 
square inch4          ,,chapter ,,vii4  
,,constructive ,,details ,,of ,,boilers4
             99       99       99       
99       99      ,,land ,,and ,,marine  
,,boilers4    #cfi4 ,q4--,will you      
explain the course of procedure in the  
construction and  setting of wagon      
boilers8    ,a4--,most boilers are made 

of plates three eighths of an inch      
thick1 and  the rivets are from three   
eighths to three fourths of an inch in  
diameter4  ,in the bottom and sides of a
 wagon boiler the heads of the rivets1  
or the  ends formed on the rivets before
 they are inserted1 should be large and 
placed next the fire1 or on the outside2
 whereas on the top of the boiler  the  
heads should be on the inside4 ,the     
rivets should be placed about two       
inches distant from centre to centre1   
and the centre of the row of rivets     
should be about one inch from the edge  
of the plate4 ,the edges of the  plates 
should be truly cut1 both inside and    
outside1 and after the parts of  the    
boiler have been riveted together1 the  
edges of the plates should be  set up or
 caulked with a blunt chisel about a    
quarter of an inch thick in  the point1 
and struck by a hammer of about three or
 four pounds weight1 one  man holding   
the caulking tool while another strikes4
    #cgj4 ,q4--,is this the usual mode  

of caulking8    ,a4--,no1 it is not the 
usual mode2 but it is the best mode1 and
 is the  mode adopted by ,mr4 ,watt4    
,the usual mode now is for one man to   
caulk the  seams with a hammer in one   
hand and a caulking chisel in the other1
 and in  some of the difficult corners  
of marine flue boilers it is not easy   
for two  men to get in4 ,a good deal of 
the caulking has also sometimes to be   
done  with the left hand4    #cga4      
,q4--,should the boiler be proved after 
caulking8    ,a4--,the boiler should be 
filled with water and caulked afresh in 
any  leaky part4 ,when emptied again1   
all the joints should be painted with a 
solution of sal ammoniac in urine1 and  
so soon as the seams are well rusted    
they should be dried with a gentle fire1
 and then be painted over with a  thin  
putty formed of whiting and linseed oil1
 the heat being continued  until the    
putty becomes so hard that it cannot be 
readily scratched with  the nail1 and   
care must be taken neither to burn the  

putty nor to  discontinue the fire until
 it has become quite dry4    #cgb4      
,q4--,how should the brickwork setting  
of a wagon boiler be built8    ,a4--,in 
building the brickwork for the setting  
of the boiler1 the part  upon which the 
heat acts with most intensity is to be  
built with clay  instead of mortar1 but 
mortar is to be used on the outside of  
the work4 ,old  bars of flat iron may be
 laid under the boiler chime to prevent 
that part  of the boiler from being     
burned out1 and bars of iron should also
 run  through the brickwork to prevent  
it from splitting4 ,the top of the      
boiler  is to be covered with brickwork 
laid in the best lime1 and if the lime  
be  not of the hydraulic kind1 it should
 be mixed with ,dutch terrass1 to make  
it impenetrable to water4 ,the top of   
the boiler should be well plastered     
with this lime1 which will greatly      
conduce to the tightness of the seams4  
,openings into the flues must be left in
 convenient situations to enable the    

flues to be swept out when required1 and
 these openings may be closed with  cast
 iron doors jointed with clay or mortar1
 which may be easily removed  when      
required4 ,adjacent to the chimney a    
slit must be left in the top of  the    
flue with a groove in the brickwork to  
enable the sliding door or  damper to be
 fixed in that situation1 which by being
 lowered into the flue  will obstruct   
the passage of the smoke and moderate   
the draught1 whereby  the chimney will  
be prevented from drawing the flame into
 it before the  heat has acted          
sufficiently upon the boiler4    #cgc4  
,q4--,are marine constructed in the same
 way as land boilers8    ,a4--,there is 
very little difference in the two cases3
 the whole of the  shells of marine     
boilers1 however1 should be double      
riveted with rivets  #aa_/afths of an   
inch in diameter1 and #b-c_/hth inches  
from centre to centre1  the weakening   
effect of double riveting being much    
less than that of single  riveting4 ,the

 furnaces above the line of bars should 
be of the best  ,lowmoor1 ,bowling1 or  
,staffordshire scrap plates1 and the    
portion of each  furnace above the bars 
should consist only of three plates1 one
 for the top  and one for each side1 the
 lower seam of the side plates being    
situated  beneath the level of the bars1
 so as not to be exposed to the heat of 
the  furnace4 ,the tube plates of       
tubular boilers should be of the best   
,lowmoor1  or ,bowling iron1 seven      
eighths to one inch thick3 the shells   
should be of  the best ,staffordshire1  
or ,thornycroft ,s crown iron1 #g_/afths
 of an inch  thick4    #cgd4 ,q4--,of   
what kind of iron should the angle iron 
or corner iron be  composed8            
,a4--,angle iron should not be used in  
the construction of boilers1 as in  the 
manufacture it becomes reedy1 and is apt
 to split up in the direction  of its   
length3 it is much the safer practice to
 bend the plates at the  corners of the 
boiler2 but this must be carefully done1

 without introducing  any more sharp    
bends than can be avoided1 and plates   
which require to be  bent much should be
 of ,lowmoor iron4 ,it will usually be  
found expedient to  introduce a ring of 
angle iron around the furnace mouths1   
though it is  discarded in the other    
parts of the boiler2 but it should be   
used as  sparingly as possible1 and any 
that is used should be of the best      
quality4    #cge4 ,q4--,is it not       
important to have the holes in the      
plates opposite to  one another8        
,a4--,the whole of the plates of a      
boiler should have the holes for the    
rivets punched1 and the edges cut       
straight1 by means of self-acting       
machinery1 in which a travelling table  
carries forward the plate with an  equal
 progression every stroke of the punch  
or shears2 and machinery of  this kind  
is now extensively employed4 ,the       
practice of forcing the parts of        
boilers together with violence1 by means
 of screw-jacks1 and drifts through  the

 holes1 should not be permitted2 as a   
great strain may thus be thrown  upon   
the rivets1 even when there is no steam 
in the boiler4 ,all rivets  should be of
 the best ,lowmoor iron4 ,the work      
should be caulked both within  and      
without wherever it is accessible1 but  
in the more confined situations  within 
the flues the caulking will in many     
cases have to be done with the  hand or 
chipping hammer1 instead of the heavy   
hammer previously prescribed4    #cgf4  
,q4--,how is the setting of marine      
boilers with internal furnaces          
effected8    ,a4--,in the setting of    
marine boilers care must be taken that  
no copper  bolts or nails project above 
the wooden platform upon which they     
rest1 and  also that no projecting      
copper bolts in the sides of the ship   
touch the  boiler1 as the galvanic      
action in such a case would probably    
soon wear the  points of contact into   
holes4 ,the platform may consist of     
three inch  planking laid across the    

keelsons nailed with iron1 nails1 the   
heads of  which are well punched down1  
and caulked and puttied like a deck4    
,the  surface may then be painted over  
with thin putty1 and fore and aft boards
  of half the thickness may then be laid
 down and nailed securely with iron     
nails1 having the heads well punched    
down4 ,this platform must then be       
covered thinly and evenly with mastic   
cement and the boiler be set down  upon 
it1 and the cement must be caulked      
beneath the boiler by means of  wooden  
caulking tools1 so as completely to fill
 every vacuity4 ,coomings of  wood      
sloped on the top must next be set round
 the boiler1 and the space  between the 
coomings and the boiler must be caulked 
full of cement1 and be  smoothed off on 
the top to the slope of the coomings1 so
 as to throw off  any water that might  
be disposed to enter between the        
coomings and the  boiler4    #cgg4      
,q4--,how is the cement used for setting
 marine boilers compounded8             

,a4--,mastic cement proper for the      
setting of boilers is sold in many      
places ready made4 ,hamelin's mastic is 
compounded as follows3--to any given    
weight of sand or pulverized earthenware
 add two thirds such given weight  of   
powdered ,bath1 ,portland1 or other     
similar stone1 and to every #efj lbs4   
weight of the mixture add #dj lbs4      
weight of litharge1 #b lbs4 of powdered 
glass or flint1 #a lb4 of minium1 and #b
 lbs4 of gray oxide of lead2 pass the   
mixture through a sieve1 and keep it in 
a powder for use4 ,when wanted for  use1
 a sufficient quantity of the powder is 
mixed with some vegetable oil  upon a   
board or in a trough in the manner of   
mortar1 in the proportion of  #fje lbs4 
of the powder to #e gallons of linseed1 
walnut1 or pink oil1 and  the mixture is
 stirred and trodden upon until it      
assumes the appearance of  moistened    
sand1 when it is ready for use4 ,the    
cement should be used on the  same day  
as the oil is added1 else it will be set

 into a solid mass4    #cgh4 ,q4--,what 
is the best length of the furnaces of   
marine boilers8    ,a4--,it has already 
been stated that furnace bars should not
 much exceed  six feet in length1 as it 
is difficult to manage long furnaces2   
but it is a  frequent practice to make  
the furnaces long and narrow1 the       
consequence of  which is1 that it is    
impossible to fire them effectually at  
the after end1  especially upon long    
voyages and in stormy weather1 and air  
escapes into  the flues at the after end
 of the bars1 whereby the efficacy of   
the boiler  is diminished4 ,where the   
bars are very long it will generally be 
found that  an increased supply of steam
 and a diminished consumption of coal   
will be  the consequence of shortening  
them1 and the bars should always lie    
with a  considerable inclination to     
facilitate the distribution of the fuel 
over  the after part of the furnace4    
,when there are two lengths of bars in  
the  furnace1 it is expedient to make   

the central cross bar for bearing up the
  ends double1 and to leave a space     
between the ends of the bars so that the
  ashes may fall through between them4  
,the space thus left enables the bars   
to expand without injury on the         
application of heat1 whereas without    
some  such provision the bars are very  
liable to get burned out by bending up  
in  the centre1 or at the ends1 as they 
must do if the elongation of the bars   
on the application of heat be prevented2
 and this must be the effect of         
permitting the spaces at the ends of the
 bars to be filled up with ashes4  ,at  
each end of each bed of bars it is      
expedient to leave a space which the    
ashes cannot fill up so as to cause the 
bars to jam2 and care must be taken     
that the heels of the bars do not come  
against any of the furnace bearers1     
whereby the room left at the end of the 
bars to permit the expansion would  be  
rendered of no avail4    #cgi4          
,q4--,have you any remarks to offer     

respecting the construction and         
arrangement of the furnace bridges and  
dampers of marine boilers8    ,a4--,the 
furnace bridges of marine boilers are   
walls or partitions built  up at the    
ends of the furnaces to narrow the      
opening for the escape of heat  into the
 flues4 ,they are either made of fire   
brick or of plate iron  containing      
water3 in the case of water bridges1 the
 top part of the bridge  should be made 
with a large amount of slant so as to   
enable the steam to  escape freely1 but 
notwithstanding this precaution the     
plates of water  bridges are apt to     
crack at the bend1 so that fire brick   
bridges appear on  the whole to be      
preferable4 ,in shallow furnaces the    
bridges often come too  near the furnace
 top to enable a man to pass over them2 
and it will save  expense if in such    
bridges the upper portion is constructed
 of two or three  fire blocks1 which may
 be lifted off where a person requires  
to enter the  flues to sweep or repair  

them1 whereby the perpetual demolition  
and  reconstruction of the upper part of
 the bridge will be prevented4    #chj4 
,q4--,what is the benefit of bridges8   
,a4--,bridges are found in practice to  
have a very sensible operation in       
increasing the production of steam1 and 
in some boilers in which the brick      
bridges have been accidentally knocked  
down by the firemen1 a very             
considerable diminution in the supply of
 steam has been experienced4 ,their     
chief operation seems to lie in         
concentrating the heat within the       
furnace  to a higher temperature1       
whereby the heat is more rapidly        
transmitted from  the furnace to the    
water1 and less heat has consequently to
 be absorbed by  the flues4 ,in this way
 the bridges render the heating surface 
of a boiler  more effective1 or enable a
 smaller amount of heating surface to   
suffice4    #cha4 ,q4--,are the bridges 
behind the furnaces the only bridges    
used in  steam boilers8    ,a4--,it is  

not an uncommon practice to place a     
hanging bridge1 consisting  of a plate  
of iron descending a certain distance   
into the flue1 at that  part of the flue
 where it enters the chimney1 whereby   
the stratum of hot  air which occupies  
the highest part of the flue is kept in 
protracted  contact with the boiler1 and
 the cooler air occupying the lower part
 of the  flue is that which alone       
escapes4 ,the practice of introducing a 
hanging  bridge is a beneficial one in  
the case of some boilers1 but is not    
applicable universally1 as boilers with 
a small calorimeter cannot be  further  
contracted in the flue without a        
diminution in their evaporating  power4 
,in tubular boilers a hanging bridge is 
not applicable1 but in some  cases a    
perforated plate is placed against the  
ends of the tubes1 which by  suitable   
connections is made to operate as a     
sliding damper which partially  or      
totally closes up the end of every tube1
 and at other times a damper            

constructed in the manner of a venetian 
blind is employed in the same           
situation4 ,these varieties of damper1  
however1 have only yet been used in     
locomotive boilers1 though applicable to
 tubular boilers of every  description4 
#chb4 ,q4--,is it a benefit to keep the 
flues or tubes appertaining to each     
furnace distinct8    ,a4--,in a flue    
boiler this cannot be done1 but in a    
tubular boiler it is  an advantage that 
there should be a division between the  
tubes pertaining  to each furnace1 so   
that the smoke of each furnace may be   
kept apart from  the smoke of the       
furnace adjoining it until the smoke of 
both enters the  chimney1 as by this    
arrangement a furnace only will be      
rendered inoperative  in cleaning the   
fires instead of a boiler1 and the tubes
 belonging to one  furnace may be swept 
if necessary at sea without interfering 
injuriously  with the action of the     
rest4 ,in a steam vessel it is necessary
 at intervals  to empty out one or more 

furnaces every watch to get rid of the  
clinkers  which would otherwise         
accumulate in them2 and it is advisable 
that the  connection between the        
furnaces should be such that this       
operation1 when  being performed on one 
furnace1 shall injure the action of the 
rest as  little as possible4    #chc4   
,q4--,can any constructive precautions  
be taken to prevent the  furnaces and   
tube plates of the boiler from being    
burned by the intensity  of the heat8   
,a4--,the sides of the internal furnaces
 or flues in all boilers should be  so  
constructed that the steam may readily  
escape from their surfaces1 with  which 
view it is expedient to make the bottom 
of the flue somewhat wider  than the    
top1 or slightly conical in the cross   
section2 and the upper  plates should   
always be overlapped by the plates      
beneath1 so that the steam  cannot be   
retained in the overlap1 but will escape
 as soon as it is  generated4 ,if the   
sides of the furnace be made high and   

perfectly vertical1  they will speedily 
be buckled and cracked by the heat1 as a
 film of steam  in such a case will     
remain in contact with the iron which   
will prevent the  access of the water1  
and the iron of the boiler will be      
injured by the high  temperature it must
 in that case acquire4 ,to moderate the 
intensity of the  heat acting upon the  
furnace sides1 it is expedient to bring 
the outside  fire bars into close       
contact with the sides of the furnace1  
so as to  prevent the entrance of air   
through the fire in that situation1 by  
which  the intensity of the heat would  
be increased4 ,the tube plate nearest   
the  furnace in tubular boilers should  
also be so inclined as to facilitate the
  escape of the steam2 and the short    
bent plate or flange of the tube plate1 
connecting the tube plate with the top  
of the furnace1 should be made with  a  
gradual bend1 as1 if the bend be sudden1
 the iron will be apt to crack or  burn 
away from the concretion of salt4 ,where

 the furnace mouths are  contracted by  
bending in the sides and top of the     
furnace1 as is the  general practice1   
the bends should be gradual1 as salt is 
apt to accumulate  in the pockets made  
by a sudden bend1 and the plates will   
then burn into  holes4    #chd4 ,q4--,in
 what manner is the tubing of boilers   
performed8    ,a4--,the tubes of marine 
boilers are generally iron tubes1 three 
inches in  diameter1 and between six and
 seven feet long2 but sometimes brass   
tubes of  similar dimensions are        
employed4 ,when brass tubes are         
employed1 the use of  ferules driven    
into the ends of the tubes is sometimes 
employed to keep  them tight2 but when  
the tubes are of malleable iron1 of the 
thickness of  ,russell's boiler tubes1  
they may be made tight merely by firmly 
driving  them into the tube plates1 and 
the same may be done with thick brass   
tubes4  ,the holes in the tube plate    
next the front of the boiler are just   
sensibly  larger in diameter than the   

holes in the other tube plate1 and the  
holes  upon the outer surfaces of both  
tube plates are very slightly           
countersunk4  ,the whole of the tubes   
are driven through both tube plates from
 the front  of the boiler1--the         
precaution1 however1 being taken to     
drive them in  gently at first with a   
light hand hammer1 until the whole of   
the tubes have  been inserted to an     
equal depth1 and then they may be driven
 up by degrees  with a heavy hammer1    
whereby any distortion of the holes from
 unequal  driving will be prevented4    
,finally1 the ends of the tubes should  
be riveted  up so as to fill the        
countersink2 the tubes should be left a 
little longer  than the distance between
 the outer surfaces of the tube plates1 
so that  the countersink at the ends may
 be filled by staving up the end of the 
tube  rather than by riveting it over2  
and the staving will be best            
accomplished  by means of a mandril with
 a collar upon it1 which is driven into 

the tube  so that the collar rests upon 
the end of the tube to be riveted2 or a 
tool  like a blunt chisel with a recess 
in its point may be used1 as is the more
  usual practice4    #che4 ,q4--,should 
not stays be introduced in substitution 
of some of the  tubes8    ,a4--,it      
appears expedient in all cases that some
 of the tubes should be  screwed at the 
ends1 so as to serve as stays if the    
riveting at the tube  ends happens to be
 burned away1 and also to act as        
abutments to the riveted  tube--or else 
to introduce very strong rods of about  
the same diameter as a  tube1 in        
substitution of some of the tubes2 and  
these stays should have  nuts at each   
end both within and without the tube    
plates1 which nuts should  be screwed   
up1 with white lead interposed1 before  
the tubes are inserted4  ,if the tubes  
are long1 their expansion when the      
boiler is being blown off  will be apt  
to start them at the ends1 unless very  
securely fixed2 and it  is difficult to 

prevent brass tubes of large diameter   
and proportionate  length from being    
started at the ends1 even when secured  
by ferules2 but  the brass tubes        
commonly employed are so small as to be 
susceptible of  sufficient compression  
endways by the adhesion due to the      
ferules to  compensate for the          
expansion1 whereby they are prevented   
from starting at  the ends4 ,in some1 of
 the early marine boilers fitted with   
brass tubes1 a  galvanic action at the  
ends of the tubes was found to take     
place1 and the  iron of the tube plates 
was wasted away in consequence1 with    
rapidity2 but  further experience proved
 the injury to be attributable chiefly  
to  imperfect fitting1 whereby a leakage
 was caused that induced oxidation1 and 
when1 the tubes were well fitted any    
injurious action at the ends of the     
tubes was found to cease4    #chf4      
,q4--,what is the best mode of          
constructing the chimney and the parts  
in connection therewith8    ,a4--,in    

sea-going steamers the funnel plates are
 usually about nine feet  long and      
#c_/afths thick2 and where different    
flues or boilers have their  debouch in 
the same chimney1 it is expedient to run
 division plates up the  chimney for a  
considerable distance1 to keep the      
draughts distinct4 ,the  dampers should 
not be in the chimney but at the end of 
the boiler flue1 so  that they may be   
available for use if the funnel by      
accident be carried  away4 ,the waste   
steam pipe should be of the same height 
as the funnel1 so  as to carry the waste
 steam clear of it1 for if the waste    
steam strikes the  funnel it will wear  
the iron into holes2 and the waste steam
 pipes should  be made at the bottom    
with a faucet joint1 to prevent the     
working of the  funnel1 when the vessel 
rolls1 from breaking the pipe at the    
neck4 ,there  should be two hoops round 
the funnel1 for the attachment of the   
funnel  shrouds1 instead of one1 so that
 the funnel may not be carried overboard

 if  one hoop breaks1 or if the funnel  
breaks at the upper hoop from the       
corrosive action of the waste steam1 as 
sometimes happens4 ,the deck over  the  
steam chest should be formed of an iron 
plate supported by angle iron  beams1   
and there should be a high angle iron   
cooming round the hole in the  deck     
through which the chimney ascends1 to   
prevent any water upon the deck  from   
leaking down upon the boiler4 ,around   
the lower part of the funnel  there     
should be a sheet iron casing to prevent
 any inconvenient dispersion  of heat in
 that situation1 and another short piece
 of casing1 of a somewhat  larger       
diameter1 and riveted to the chimney1   
should descend over the first  casing1  
so as to prevent the rain or spray which
 may beat against the  chimney from     
being poured down within the casing upon
 the top of the  boiler4 ,the pipe for  
conducting away the waste water from the
 top of the  safety valve should lead   
overboard1 and not into the bilge of the

 ship1 as  inconvenience arises from the
 steam occasionally passing through it1 
if it  has its termination in the engine
 room4    #chg4 ,q4--,are not the       
chimneys of some vessels made so that   
they may be  lowered when required8     
,a4--,the chimneys of small river       
vessels which have to pass under bridges
  are generally formed with a hinge1 so 
that they may be lowered backward  when 
passing under a bridge2 and the chimneys
 of some screw vessels are  made so as  
to shut up like a spyglass when the     
fires are put out and the  vessel is    
navigated under sails4 ,in smaller      
vessels1 however1 two lengths  of       
chimney suffice2 and in that case there 
is a standing piece on deck1  which1    
however1 does not project above the     
bulwarks4    #chh4 ,q4--,will you       
explain any further details in the      
construction of  marine boilers which   
occur to you as important8    ,a4--,the 
man-hole and mud-hole doors1 unless put 
on from the outside1 like  a cylinder   

cover1 with a great number of bolts1    
should be put on from the  inside with  
cross bars on the outside1 and the bolts
 should be strong1 and  have coarse     
threads and square nuts1 so that the    
threads may not be  overrun1 nor the    
nuts become round1 by the unskilful     
manipulations of the  firemen1 by whom  
these doors are removed or replaced4 ,it
 is very expedient  that sufficient     
space should be left between the furnace
 and the tubes in  all tubular boilers  
to permit a boy to go in to clear away  
any scale that  may have formed1 and to 
hold on the rivets in the event of      
repair being  wanted2 and it is also    
expedient that a vertical row of tubes  
should be  left out opposite to each    
water space to allow the ascent of the  
steam and  descent of the water1 as it  
has been found that the removal of the  
tubes in  that position1 even in a      
boiler with deficient heating surface1  
has  increased the production of steam1 
and diminished the consumption of fuel4 

,the tubes should all be kept in the    
same vertical line1 so as to permit the 
introduction of an instrument to scrape 
them2 but they may be zig-zagged in  the
 horizontal line1 whereby a greater     
strength of metal will be obtained      
around the holes in the tube plates1 and
 the tubes should not be placed too     
close together1 else their heating      
efficacy will be impaired4              
,,incrustation ,,and ,,corrosion ,,of   
,,boilers4      #chi4 ,q4--,what is the 
cause of the formation of scale in      
marine boilers8    ,a4--,scale is formed
 in all boilers which contain earthy or 
saline  matters1 just in the way in     
which a scaly deposit1 or rock1 as it is
  sometimes termed1 is formed in a tea  
kettle4 ,in sea water the chief         
ingredient is common salt1 which exists 
in solution3 the water admitted to  the 
boiler is taken away in the shape of    
steam1 and the saline matter which  is  
not vaporizable accumulates in process  
of time in the boiler1 until its  amount

 is so great that the water is          
saturated1 or unable to hold any more   
in solution2 the salt is then           
precipitated and forms a deposit which  
hardens by heat4 ,the formation of      
scale1 therefore1 is similar to the     
process of making salt from sea water by
 evaporation1 the boiler being1 in      
fact1 a large salt pan4    #cij4        
,q4--,but is the scale soluble in fresh 
water like the salt in a salt  pan8     
,a4--,no1 it is not2 or if soluble at   
all1 is only so to a very limited       
extent4 ,the several ingredients in sea 
water begin to be precipitated from     
solution at different degrees of        
concentration2 and the sulphate and     
carbonate of lime1 which begin to be    
precipitated when a certain state of    
concentration is reached1 enter largely 
into the composition of scale1 and  give
 it its insoluble character4 ,pieces of 
waste or other similar objects  left    
within a marine boiler appear1 when     
taken out1 as if they had been          

petrified2 and the scale deposited upon 
the flues of a marine boiler  resembles 
layers of stone4    #cia4 ,q_/--,is much
 inconvenience experienced in marine    
boilers from these  incrustations upon  
the flues8    ,a4--,incrustation in     
boilers at one time caused much more    
perplexity than  it does at present1 as 
it was supposed that in some seas it was
 impossible  to prevent the boilers of a
 steamer from becoming salted up2 but it
 has now  been satisfactorily           
ascertained that there is very little   
difference in the  saltness of different
 seas1 and that however salt the water  
may be1 the  boiler will be preserved   
from any injurious amount of            
incrustation by  blowing off1 as it is  
called1 very frequently1 or by          
permitting a  considerable portion of   
the supersalted water to escape at short
 intervals  into the sea4 ,if blowing   
off be sufficiently practised1 the scale
 upon the  flues will never be much     
thicker than a sheet of writing paper1  

and no  excuse should be accepted from  
engineers for permitting a boiler to be 
damaged by the accumulation of          
calcareous deposit4    #cib4 ,q4--,what 
is the temperature at which sea water   
boils in a steam  boiler8    ,a4--,sea  
water contains about #a_/ccrd its weight
 of salt1 and in the open  air it boils 
at the temperature of #bac4b2 if the    
proportion of salt be  increased to     
#b_/ccrds of the weight of the water1   
the boiling point will  rise to #bad4d2 
with #c_/ccrds of salt the boiling point
 will be #bae4e2  #d_/ccrds1 #baf4g2    
#e_/ccrds1 #bag4i2 #f_/ccrds1 #bai2     
#g_/ccrds1 #bbj4b2 #h_/ccrds1  #bba4d2  
#i_/ccrds1 #bbb4e2 #aj_/ccrds1 #bbc4g2  
#aa_/ccrds1 #bbd4i2 and #ab_/ccrds1     
which is the point of saturation1 #bbf4 
,in a steam boiler the boiling  points  
of water containing these proportions of
 salt must be higher1 as the  elevation 
of temperature due to the pressure of   
the steam has to be added  to that due  
to the saltness of the water2 the       

temperature of steam at the  atmospheric
 pressure being #bab1 its temperature1  
at a pressure of #ae lbs4  per square   
inch above the atmosphere1 will be #bej1
 and adding to this #d4g  as the        
increased temperature due to the        
saltness of the water when it  contains 
#d_/ccrds of salt1 we have #bed4g as the
 temperature of the water in  the       
boiler1 when it contains #d_/ccrds of   
salt and the pressure of the steam  is  
#ae lbs4 on the square inch4    #cic4   
,q4--,what degree of concentration of   
the salt water may be safely  permitted 
in a boiler8    ,a4--,it is found by    
experience that when the concentration  
of the salt  water in a boiler is       
prevented from exceeding that point at  
which it  contains #b_/ccrds its weight 
of salt1 no injurious incrustation will 
take  place1 and as sea water contains  
only #a_/ccrd of its weight of salt1 it 
is  clear that it must be reduced by    
evaporation to one half of its bulk     
before  it can contain #b_/ccrds of     

salt2 or1 in other words1 a boiler must 
blow out  into the sea one half of the  
water it receives as feed1 in order to  
prevent  the water from rising above    
#b_/ccrds of concentration1 or #h ounces
 of salt  to the gallon4    #cid4       
,q4--,how do you determine #h ounces to 
the gallon to be equivalent to  twice   
the density of salt water1 or two salt  
waters as it is sometimes  called8      
,a4--,the density of the water of       
different seas varies somewhat4 ,a      
gallon  of fresh water weighs #aj lbs42 
a gallon of salt water from the ,baltic 
weighs #aj4ae lbs42 a gallon of salt    
water from the ,irish ,channel weighs   
#aj4bh lbs42 and a gallon of salt water 
from the ,mediterranean #aj4bi lbs4 ,if 
we take an average saltness represented 
by a weight of #aj4be lbs41 then a      
gallon of water concentrated to twice   
this saltness will weigh #aj4e lbs41  or
 the salt in it will weigh 4#e lbs or #h
 oz41 which is the proportion of #h  oz4
 to the gallon4 ,however1 the proportion

 of #b_/ccrds gives a greater           
proportion than #h oz4 to the gallon1   
for #b_/cc  #a_/af nearly1 and #a_/af of
 #aj  lbs4  #aj oz4 ,by keeping the     
density of the water in a marine boiler 
at the  proportion of #h or #aj oz4 to  
the gallon1 no inconvenient amount of   
scale  will be deposited on the flues or
 tubes4 ,the bulk of water1 it may be   
remarked1 is not increased by putting   
salt in it up to the point of           
saturation1 but only its density is     
increased4    #cie4 ,q4--,is there not a
 great loss of heat by blowing off so   
large a  proportion of the heated water 
from the boiler8    ,a4--,the loss is   
not very great4 ,boilers are sometimes  
worked at a  saltness of #d_/ccrds1 and 
taking this saltness and supposing the  
latent heat  of steam to be at #ajjj at 
the temperature of #bab1 and reckoning  
the sum  of the latent and sensible     
heats as forming a constant quantity1   
the latent  heat of steam at the        
temperature of #bej will be #ifb1 and   

the total heat  of the steam will be    
#abab in the case of fresh water2 but as
 the feed  water is sent into the boiler
 at the temperature of #ajj1 the        
accession of  heat it receives from the 
fuel will be #aaab in the case of fresh 
water1 or  #aaab increased by #c4ih in  
the case of water containing #d_/cc;ds  
of salt--  the #c4ih being the #d4g     
increase of temperature due to the      
presence of  #d_/ccrds of salt1         
multiplied by #j4hdg the specific heat  
of steam4 ,this makes  the total        
accession of heat received by the steam 
in the boiler equal to  #aaae4ih1 or say
 #aaaf1 which multiplied by #c1 as #c   
parts of the water are  raised into     
steam1 gives us #ccdh for the heat in   
the steam1 while the  accession of heat 
received in the boiler by the #a part of
 residual brine  will be #aed4g1        
multiplied by #j4he1 the specific heat  
of the brine1 or  #acj4die2 and #ccdh   
divided by #acj4die is about #a_/bfth4  
,it appears1  therefore1 that by blowing

 off the boiler to such an extent that  
the  saltness shall not rise above what 
answers to #d_/ccrds of salt1 about     
#a_/beth  of the heat is blown into the 
sea2 this is but a small proportion1 and
 as  there will be a greater waste of   
heat1 if from the existence of scale    
upon  the flues the heat can be only    
imperfectly transmitted to the water1   
there  cannot be even an economy of fuel
 in niggard blowing off1 while it       
involves  the introduction of other     
evils4 ,the proportion of #d_/ccrds of  
saltness1  however1 or #af oz4 to the   
gallon1 is larger than is advisable1    
especially  as it is difficult to keep  
the saltness at a perfectly uniform     
point1 and  the working point should1   
therefore1 be #b_/ccrds as before       
prescribed4    #cif4 ,q4--,have no means
 been devised for turning to account the
 heat  contained in the brine which is  
expelled from the boiler8    ,a4--,to   
save a part of the heat lost by the     
operation of blowing off1 the  hot brine

 is sometimes passed through a number of
 small tubes surrounded by  the feed    
water2 but there is no very great gain  
from the use of such  apparatus1 and the
 tubes are apt to become choked up1     
whereby the safety of  the boiler may be
 endangered by the injurious            
concentration of its  contents4 ,pumps1 
worked by the engine for the extraction 
of the brine1 are  generally used in    
connection with the small tubes for the 
extraction of the  heat from the        
supersalted water2 and if the tubes     
become choked the pumps  will cease to  
eject the water1 while the engineer may 
consider them to be  all the while in   
operation4    #cig4,q4--,what is the    
usual mode of blowing off the           
supersalted water from  the boiler8     
,a4--,the general mode of blowing off   
the boiler is to allow the water to     
rise gradually for an hour or two above 
the lowest ,working level1 and then  to 
open the cock communicating with the    
sea1 and keep it open until the  surface

 of the water within the boiler has     
fallen several inches2 but in  some     
cases a cock of smaller size is allowed 
to run water continuously1 and  in other
 cases brine pumps are used as already  
mentioned4 ,in every case in  which the 
supersalted water is discharged from the
 boiler in a continuous  stream1 a      
hydrometer or salt gauge of some        
convenient construction should  be      
applied to the boiler1 so that the      
density of the water may at all times   
be visible1 and immediate notice be     
given of any interruption of the        
operation4 ,various contrivances have   
been devised for this purpose1 the  most
 of which operate on the principle of a 
hydrometer2 but perhaps a more          
satisfactory principle would be that of 
a differential steam gauge1 which  would
 indicate the difference of pressure    
between the steam in the boiler  and the
 steam of a small quantity of fresh     
water enclosed in a suitable  vessel1   
and immerged in the water of the boiler4

    #cih4 ,q4--,what is the advantage of
 blowing off from the surface of the    
water in the boiler8    ,a4--,blowing   
off from a point near the surface of the
 water is more  beneficial than blowing 
off from the bottom of the boiler4      
,solid particles  of any kind1 it is    
well known1 if introduced into boiling  
water1 will lower  the boiling point in 
a slight degree1 and the steam will     
chiefly be  generated on the surface of 
the particles1 and indeed will have the 
appearance of coming out of them2 if the
 particles be small the steam  generated
 beneath and around them will balloon   
them to the surface of the  water1 where
 the steam will be liberated and the    
particles will descend2  and the        
impalpable particles in a marine boiler1
 which by their subsidence  upon the    
flues concrete into scale1 are carried  
in the first instance to  the surface of
 the water1 so that if they be caught   
there and ejected from  the boiler1 the 
formation of scale will be prevented4   

#cii4 ,q4--,are there any plans in      
operation for taking advantage of this  
property of particles rising to the     
surface8    ,a4--,advantage is taken of 
this property in ,lamb's ,scale         
,preventer1 which  is substantially a   
contrivance for blowing off from the    
surface of the  water that in practice  
is found to be very effectual2 but a    
float in  connection with a valve at the
 mouth of the discharging pipe is there 
introduced1 so as to regulate the       
quantity of water blown out by the      
height  of the water level1 or by the   
extent of opening given to the feed     
cock4 ,the  operation1 however1 of the  
contrivance would be much the same if   
the float  were dispensed with2 but the 
float acts advantageously in hindering  
the  water from rising too high in the  
boiler1 should too much feed be         
admitted1  and thereby obviates the risk
 of the water running over into the     
cylinder4  ,in some boilers sheet iron  
vessels1 called sediment collectors1 are

  employed1 which collect into them the 
impalpable matter1 which in ,lamb's     
apparatus is ejected from the boiler at 
once4 ,one of these vessels1 of  about  
the size and shape of a loaf of sugar1  
is put into each boiler with  the apex  
of the cone turned downwards into a pipe
 leading overboard1 for  conducting the 
sediment away from the boiler4 ,the base
 of the cone stands  some distance above
 the water line1 and in its sides       
conical slits are cut1  so as to        
establish a free communication between  
the water within the  conical vessel and
 the water outside it4 ,the particles of
 stony matter  which are ballooned to   
the surface by the steam in every other 
part of the  boiler1 subside within the 
cone1 where1 no steam being generated1  
the water  is consequently tranquil2 and
 the deposit is discharged overboard by 
means  of a pipe communicating with the 
sea4 ,by blowing off from the surface of
  the water1 the requisite cleansing    
action is obtained with less waste of   

heat2 and where the water is muddy1 the 
foam upon the surface of the water  is  
ejected from the boiler--thereby        
removing one of the chief causes of     
priming4    #djj4 ,q4--,what is the     
cause of the rapid corrosion of marine  
boilers8    ,a4--,marine boilers are    
corroded externally in the region of the
 steam  chest by the dripping of water  
from the deck2 the bottom of the boiler 
is  corroded by the action of the bilge 
water1 and the ash pits by the practice 
of quenching the ashes with1 salt water4
 ,these sources of injury1 however1     
admit of easy remedy2 the top of the    
boiler may be preserved from external   
corrosion by covering it with felt upon 
which is laid sheet lead soldered  at   
every joint so as to be impenetrable to 
water2 the ash pits may be  shielded by 
guard plates which are plates fitting   
into the ash pits and  attached to the  
boiler by a few bolts1 so that when worn
 they may be  removed and new ones      
substituted1 whereby any wear upon the  

boiler in that  part will be prevented2 
and there will be very little wear upon 
the bottom  of a boiler if it be        
imbedded in mastic cement laid upon a   
suitable  platform4    #dja4 ,q4--,are  
not marine boilers subject to internal  
corrosion8    ,a4--,yes2 the greatest   
part of the corrosion of a boiler takes 
place in  the inside of the steam chest1
 and the origin of this corrosion is one
 of  the obscurest subjects in the whole
 range of engineering4 ,it cannot be    
from  the chemical action of the salt   
water upon the iron1 for the flues and  
other parts of the boiler beneath the   
water suffer very little from           
corrosion1 and in steam vessels provided
 with ,hall's condensers1 which  supply 
the boiler with fresh water1 not much   
increased durability of the  boiler has 
been experienced4 ,nevertheless1 marine 
boilers seldom last more  than for #e or
 #f years1 whereas land boilers made of 
the same quality of  iron often last #ah
 or #bj years1 and it does not appear   

probable that land  boilers would last a
 very much shorter time if salt water   
were used in  them4 ,the thin film of   
scale spread over the parts of a marine 
boiler  situated beneath the water1     
effectually protect them from corrosion2
 and  when the other parts are          
completely worn out the flues generally 
remain so  perfect1 that the hammer     
marks upon them are as conspicuous as at
 their  first formation4 ,the operation 
of the steam in corroding the interior  
of  the boiler is most capricious--the  
parts which are most rapidly worn away  
in one boiler being untouched in        
another2 and in some cases one side of a
  steam chest will be very much wasted  
away while the opposite side remains    
uninjured4 ,sometimes the iron          
exfoliates in the shape of a black oxide
  which comes away in flakes like the   
leaves of a book1 while in other cases  
the iron appears as if eaten away by a  
strong acid which had a solvent  action 
upon it4 ,the application of felt to the

 outside of a boiler1 has in  several   
cases been found to accelerate sensibly 
its internal corrosion2  boilers in     
which there is a large accumulation of  
scale appear to be more  corroded than  
where there is no such deposit2 and     
where the funnel passes  through the    
steam chest the iron of the steam chest 
is invariably much more  corroded than  
where the funnel does not pass through  
it4    #djb4 ,q4--,can you suggest no   
reason for the rapid internal corrosion 
of  marine boilers8    ,a4--,the facts  
which ,i have enumerated appear to      
indicate that the  internal corrosion of
 marine boilers is attributable chiefly 
to the  existence of surcharged steam   
within them1 which is steam to which an 
additional quantity of heat has been    
communicated subsequently to its        
generation1 so that its temperature is  
greater than is due to its elastic      
force2 and on this hypothesis the       
observed facts relative to corrosion    
become to some extent explicable4 ,felt1

 applied to the outside of a boiler1    
may accelerate its internal corrosion by
 keeping the steam in a surcharged      
state1 when by the dispersion of a part 
of the heat it would cease to be in     
that state2 boilers in which there is a 
large accumulation of scale must  have  
worked with the water very salt1 which  
necessarily produces surcharged  steam2 
for the temperature of steam cannot be  
less than that of the water  from which 
it is generated1 and inasmuch as the    
boiling point of water1  under any given
 pressure1 rises with the saltness of   
the water1 the  temperature of the steam
 must rise with the saltness of the     
water1 the  pressure remaining the same2
 or1 in other words1 the steam must have
 a  higher temperature than is due to   
its elastic force1 or be in the state of
  surcharged steam4 ,the circumstance of
 the chimney flue passing through the   
steam will manifestly surcharge the     
steam with heat1 so that all the        
circumstances which are found to        

accelerate corrosion1 are it appears    
such  as would also induce the formation
 of surcharged steam4    #djc4 ,q4--,is 
it the natural effect of surcharged     
steam to waste away iron8    ,a4--,it is
 the natural effect of surcharged steam 
to oxidate the iron with  which it is in
 contact1 as is illustrated by the      
familiar process for  making hydrogen   
gas by sending steam through a red hot  
tube filled with  pieces of iron2 and   
although the action of the surcharged   
steam in a boiler  is necessarily very  
much weaker than where the iron is red  
hot1 it  manifestly must have some      
oxidizing effect1 and the amount of     
corrosion  produced may be very material
 where the action is perpetual4 ,boilers
 with a  large extent of heating        
surface1 or with descending flues       
circulating  through the cooler water in
 the bottom of the boiler before        
ascending the  chimney1 will be less    
corroded internally than boilers in     
which a large  quantity of the heat     

passes away in the smoke2 and the       
corrosion of the  boiler will be        
diminished if the interior of any flue  
passing through the  steam be coated    
with fire brick1 so as to present the   
transmission of the  heat in that       
situation4 ,the best practice1 however1 
appears to consist in  the transmission 
of the smoke through a suitable passage 
on the outside of  the boiler1 so as to 
supersede the necessity of carrying any 
flue through  the steam at all2 or a    
column of water may be carried round the
 chimney1  into which as much of the    
feed water may be introduced as the heat
 of the  chimney is capable of raising  
to the boiling point1 as under this     
limitation the presence of feed water   
around the chimney in the steam chest   
will fail to condense the steam4        
#djd4 ,q4--,in steam vessels there are  
usually several boilers8    ,a4--,yes1  
in steam vessels of considerable power  
and size4    #dje4 ,q4--,are these      
boilers generally so constructed1 that  

any one of them  may be thrown out of   
use8    ,a4--,marine boilers are now    
generally supplied with stop valves1    
whereby  one boiler may be thrown out of
 use without impairing the efficacy of  
the  remainder4 ,these stop valves are  
usually spindle valves of large size1   
and  they are for the most part set in a
 pipe which runs across the steam       
chests1 connecting the several boilers  
together4 ,the spindles of these  valves
 should project through stuffing boxes  
in the covers of the valve  chests1 and 
they should be balanced by a weighted   
lever1 and kept in  continual action by 
the steam4 ,if the valves be lifted up1 
and be suffered  to remain up1 as is the
 usual practice1 they will become fixed 
by corrosion  in that position1 and it  
will be impossible after some time to   
shut them on  an emergency4 ,these      
valves should always be easily          
accessible from the  engine room2 and it
 ought not to be necessary for the coal 
boxes to be  empty to gain access to    

them4    #djf4 ,q4--,should each boiler 
have at least one safety valve for      
itself8    ,a4--,yes2 it would be quite 
unsafe without this provision1 as the   
stop  valve might possibly jam4         
,sometimes valves jam from a distortion 
in the  shape of the boiler when a      
considerable pressure is put upon it4   
#djg4 ,q4--,how is the admission of the 
water into the boiler regulated8        
,a4--,the admission of feed water into  
the boiler is regulated by hand by  the 
engineer by means of cocks1 and         
sometimes by spindle valves raised and  
lowered by a screw4 ,cocks appear to be 
the preferable expedient1 as they  are  
less liable to accident or derangement  
than screw valves1 and in modern  steam 
vessels they are generally employed4    
#djh4 ,q4--,at what point of the boiler 
is the feed introduced8    ,a4--,the    
feed water is usually conducted from the
 feed cock to a point  near the bottom  
of the boiler by means of an internal   
pipe1 the object of  this arrangement   

being to prevent the rising steam from  
being condensed by  the entering water4 
,by being introduced near the bottom of 
the boiler1 the  water comes into       
contact in the first place with the     
bottoms of the  furnaces and flues1 and 
extracts heat from them which could not 
be  extracted by water of a higher      
temperature1 whereby a saving of fuel is
  accomplished4 ,in some cases the feed 
water is introduced into a casing       
around the chimney1 from whence it      
descends into the boiler4 ,this plan    
appears to be an expedient one when the 
boiler is short of heating surface1  and
 more than a usual quantity of heat     
ascends the chimney2 but in well        
proportioned boilers a water casing     
round the chimney is superfluous4 ,when 
a water casing is used the boiler is    
generally fed by a head of water1 the   
feed water being forced up into a small 
tank1 from whence it descends into  the 
boiler by the force of gravity1 while   
the surplus runs to waste1 as in  the   

feeding apparatus of land engines4      
#dji4 ,q4--,suppose that the engineer   
should shut off the feed water from  the
 boilers while the engine was working1  
what would be the result8    ,a4--,the  
result would be to burst the feed pipes1
 except for a safety  valve placed on   
the feed pipe between the engine and the
 boilers1 which  safety valve opens when
 any undue pressure comes upon the      
pipes1 and allows  the water to escape4 
,there is1 however1 generally a cock on 
the suction  side of the feed pump1     
which regulates the quantity of water   
drawn into the  pump4 ,but there must be
 cocks on the boilers also to determine 
into which  boiler the water shall be   
chiefly discharged1 and these cocks are 
sometimes  all shut accidentally at the 
same time4    #daj4 ,q4--,is there no   
expedient in use in steam vessels for   
enabling the  position of the water     
level in the boiler to determine the    
quantity of feed  water admitted8       
,a4--,in some steam vessels floats have 

been introduced to regulate the  feed1  
but their action cannot be depended on  
in agitated water1 if applied  after the
 common fashion4 ,floats would probably 
answer if placed in a  cylinder which   
communicates with the water in the      
boiler by means of small  holes2 and a  
disc of metal might be attached to the  
end of a rod extending  beneath the     
water level1 so as to resist irregular  
movements from the  motion of the ship  
at sea1 which would otherwise impair the
 action of the  apparatus4    #daa4     
,q4--,how is the proper level of the    
water in the boiler of a steam  vessel  
maintained when1 the engine is stopped  
for some time1 and the boiler  is       
blowing off steam8    ,a4--,by means of 
a separate pump worked sometimes by     
hand1 but usually by  a small separate  
engine called the ,donkey engine4 ,this 
pump1 by the aid of  suitable cocks1    
will pump from the sea into the boiler2 
from the sea upon  deck either to wash  
decks or to extinguish fire2 and from   

the bilge  overboard1 through a suitable
 orifice in the side of the ship4       
,,locomotive ,,boilers4    #dab4        
,q4--,will you recapitulate the general 
features of locomotive  boilers8        
,a4--,locomotive boilers consist of     
three portions 7see fig4 #bi73 the      
barrel ,e1 ,e1 containing the tubes1 the
 fire box ,b1 and the smoke box ,f2 of  
which the barrel smoke box1 and external
 fire box are always of iron1 but  the  
internal fire box is generally made of  
copper1 though sometimes also it  is    
made of iron4 ,the tubes are sometimes  
of iron1 but generally of brass  fixed  
in by ferules4 ,the whole of the iron   
plates of a locomotive boiler  ,which   
are subjected to the pressure of steam1 
should be ,lowmoor or ,bowling  plates  
of the best quality2 and the copper     
should be coarse grained1 rather  than  
rich or soft1 and be perfectly free from
 irregularities of structure  and       
lamination4    #dac4 ,q4--,what are the 
usual dimensions of the barrel8         

,a4--,the thickness of the plates       
composing the barrel of the boiler      
varies  generally from #e_/afths to     
#c_/hths of an inch1 and the plates     
should run in  the direction of the     
circumference1 so that the fibres of the
 iron may be  in the direction of the   
strain4 ,the diameter of the barrel     
commonly varies  from #c ft4 to #c ft4  
#f inches2 the diameter of the rivets   
should be from  #aa_/afths to #c_/dths  
of an inch1 and the pitch of the rivets 
or distance  between their centres      
should be from #ag_/hth to #b inches4   
#dad4 ,q4--,how are the fire boxes of a 
locomotive constructed8    ,a4--,the    
space between the external and internal 
fire boxes forms a water  space1 which  
must be stayed every #d-a_/b or #e      
inches by means of copper or  iron stay 
bolts1 screwed through the outer fire   
box into the metal of the  inner fire   
box1 and securely riveted within it3    
iron stay bolts are as  durable as      
copper1 and their superior tenacity     

gives them an advantage4  ,sometimes    
tubes are employed as stays4 ,the       
internal and external fire boxes  are   
joined together at the bottom by a      
,n-shaped iron1 and round the fire  door
 they are connected by means of a copper
 ring #a-a_/d in4 thick1 and #b  in4    
broad1--the inner fire box being dished 
sufficiently outward at that  point1 and
 the outer fire box sufficiently inward1
 to enable a circle of  rivets #c_/d of 
an inch in diameter passing through the 
copper ring and the  two thicknesses of 
iron1 to make a water-tight joint4 ,the 
thickness of the  plates composing the  
external fire box is in general #c_/hths
 of an inch if  the fire box is         
circular1 and from #c_/hths to #a_/b    
inch if the fire box is  square2 and the
 thickness of the internal fire box is  
in most cases #g_/afths  if copper1 and 
from #c_/hths to #g_/afths of an inch if
 of iron4 ,circular  internal fire      
boxes1 if made of iron1 should be welded
 rather than riveted1  as the rivet     

heads are liable to be burnt away by the
 action of the fire2  and when the fire 
boxes are square each side should       
consist of a single  plate1 turned over 
at the edges with a radius of #c inches1
 for the  introduction of the rivets4   
#dae4 ,q4--,is there any provision for  
stiffening the crown of the furnace  in 
a locomotive8    ,a4--,the roof of the  
internal fire box1 whether flat as in   
,stephenson's  engines1 or dome shaped  
as in ,bury's1 requires to be stiffened 
with cross  stay bars1 but the bars     
require to be stronger and more numerous
 when  applied to a flat surface4 ,the  
ends of these stay bars rest above the  
vertical sides of the fire box2 and to  
the stay bars thus extending across  the
 crown1 the crown is attached at        
intervals by means of stay bolts4 ,there
  are projecting bosses upon the stay   
bars encircling the bolts at every      
point where a bolt goes through1 but in 
the other parts they are kept clear  of 
the fire box crown so as to permit the  

access of water to the metal2  and1 with
 the view of facilitating the ascent of 
the steam1 the bottom of  each stay bar 
should be sharpened away in those parts 
where it does not  touch the boiler4    
#daf4 ,q4--,is any inconvenience        
experienced from the intense heat in a  
locomotive furnace8    ,a4--,the fire   
bars in locomotives have always been a  
source of trouble1 as  from the         
intensity of the heat in the furnace    
they become so hot as to  throw off a   
scale1 and to bend under the weight of  
the fuel4 ,the best  alleviation of     
these evils lies in making the bars deep
 and thin3 #d or #e  inches deep by five
 eighths of an inch thick on the upper  
side1 and three  eighths of an inch on  
the under side1 are found in practice to
 be good  dimensions4 ,in some          
locomotives a frame carrying a number of
 fire bars is  made so that it may be   
dropped suddenly by loosening a catch2  
but it is  found that any such mechanism
 can rarely be long kept in working     

order1 as  the molten clinker by running
 down between the frame and the boiler  
will  generally glue the frame into its 
place4 ,it is therefore found preferable
  to fix the frame1 and to lift up the  
bars by the dart used by the stoker1    
when any cause requires the fire to be  
withdrawn4 ,the furnace bars of         
locomotives are always made of malleable
 iron1 and indeed for every species  of 
boiler malleable iron bars are to be    
preferred to bars of cast iron1 as  they
 are more durable1 and may if thin be   
set closer together1 whereby the  small 
coal or coke is saved that would        
otherwise fall into the ash pit4 ,the   
ash box of locomotives is made of plate 
iron1 a quarter thick3 it should  not be
 less than #aj in4 deep1 and its bottom 
should be about #i in4 above  the level 
of the rails4 ,the chimney of a         
locomotive is made of plate iron  one   
eighth of an inch thick3 it is usually  
of the same diameter as the  cylinder1  
but is better smaller1 and must not     

stand more than #ad ft4 high  above the 
level of the rails4    #dag4 ,q4--,are  
locomotive boilers provided with a steam
 chest8    ,a4--,the upper portion of   
the external fire box is usually formed 
into a  steam chest1 which is sometimes 
dome shaped1 sometimes semicircular1 and
  sometimes of a pyramidical form1 and  
from this steam chest the steam is      
conducted away by an internal pipe to   
the cylinders2 but in other cases an    
independent steam chest is set upon the 
barrel of the boiler1 consisting of  a  
plate iron cylinder1 #bj inches in      
diameter1 #b feet high1 and three       
eighths of an inch thick1 with a dome   
shaped top1 and with the seam welded    
and the edge turned over to form a      
flange of attachment to the boiler4 ,the
  pyramidical dome1 of the form employed
 in ,stephenson's locomotives1  presents
 a considerable extent of flat surface  
to the pressure of the  steam1 and this 
flat surface requires to be very        
strongly stayed with angle  irons and   

tension rods2 whereas the semiglobular  
dome of the kind employed  in ,bury's   
engines requires no staying whatever4   
,latterly1 however1 these  domes over   
the fire box have been either much      
reduced in size or abandoned            
altogether4    #dah4 ,q4--,is any       
beneficial use made of the surplus steam
 of a locomotive8    ,a4--,to save the  
steam which is formed when the engine is
 stationary1 a  pipe is usually fitted  
to the boiler1 which on a cock being    
turned conducts  the steam into the     
water in the tender1 whereby the feed   
water is heated1  and less fuel is      
subsequently required4 ,this method of  
disposing of the  surplus steam may be  
adopted when the locomotive is          
descending inclines1 or  on any occasion
 where more steam is produced than the  
engine can consume4    #dai4,q4--,what  
means are provided to facilitate the    
inspection and cleaning  of locomotive  
boilers8    ,a4--,the man hole1 or      
entrance into the boiler1 consists of a 

circular or  oval aperture of about #ae 
in4 diameter1 placed in ,bury's         
locomotive at the  apex of the dome1 and
 in ,stephenson's upon the front of the 
boiler1 a few  inches below the level of
 the rounded part2 and the cover of the 
man hole  in ,bury's engine contains the
 safety valve seats4 ,in whatever       
situation  this man hole is placed1 the 
surfaces of the ring encircling the     
hole1 and  of the internal part of the  
door or cover1 should be accurately     
fitted  together by scraping or         
grinding1 so that they need only the    
interposition  of a little red lead to  
make them quite tight when screwed      
together4 ,lead  or canvas joints1 if of
 any considerable thickness1 will not   
long withstand  the action of high      
pressure steam2 and the whole of the    
joints about a  locomotive should be    
such that they require nothing more than
 a little  paint or putty1 or a ring of 
wire gauze smeared with white or red    
lead to  make them perfectly tight4     

,there must be a mud hole opposite the  
edge of  each water space1 if the fire  
box be square1 to enable the boiler to  
be  easily cleaned out1 and these holes 
are most conveniently closed by screwed 
plugs made slightly taper4 ,a cock for  
emptying the boiler is usually fixed  at
 the bottom of the fire box1 and it     
should be so placed as to be  accessible
 when the engine is at work1 in order   
that the engine driver may  blow off    
some water if necessary2 but it must not
 be in such a position as  to send the  
water blown off among the machinery1 as 
it might carry sand or  grit into the   
bearings1 to their manifest injury4     
#dbj4 ,q4--,will you state the          
dimensions of the tube plate1 and the   
means  of securing the tubes in it8     
,a4--,the tube plates are generally made
 from five eighths to three fourths  of 
an inch thick1 but seven eighths of an  
inch thick appears to be  preferable1 as
 when the plate is thick the holes will 
not be so liable to  change their figure

 during the process of feruling the     
tubes3 the distance  between the tubes  
should never be made less than three    
fourths of an inch1  and the holes      
should be slightly tapered so as to     
enable the tubes to hold  the tube      
plates together4 ,the tubes are secured 
in the tube plates by means  of taper   
ferules driven into the ends of the     
tubes4 ,the ferules are for the  most   
part made of steel at the fire box end1 
and of wrought iron at the  smoke box   
end1 though ferules of malleable cast   
iron have in some cases  been used with 
advantage3 malleable cast iron ferules  
are almost as easily  expanded when     
hammered cold upon a mandrel1 as the    
common wrought iron ones  are at a      
working heat4 ,spring steel1 rolled with
 a feather edge1 to  facilitate its     
conversion into ferules1 is supplied by 
some of the  steel-makers of ,sheffield1
 and it appears expedient to make use of
 steel  thus prepared when steel ferules
 are employed4 ,in cases where ferules  

are  not employed1 it may be advisable  
to set out the tube behind the tube     
plate  by means of an expanding mandrel4
 ,there are various forms of this       
instrument4 ,one form is that known as  
,prosser's expanding mandrel1 in which  
there are six or eight segments1 which  
are forced out by means of a  hexagonal 
or octagonal wedge1 which is forced     
forward by a screw4 ,when the  wedge is 
withdrawn1 the segments collapse        
sufficiently to enable them to  enter   
the tube1 and there is an annular       
protuberance on the exterior circle  of 
the segments1 which protuberance1 when  
the mandrel is put into the tube1  just 
comes behind the inner edge of the tube 
plate4 ,when the wedge is  tightened up 
by the screw1 the protuberance on the   
exterior of the segments  composing the 
mandrel causes a corresponding bulge to 
take place in the  tube1 at the back of 
the tube plate1 and the tube is thereby 
brought into  more intimate contact with
 the tube plate than would otherwise be 

the case4  ,there is a steel ring       
indented into the segments of ,prosser's
 mandrel1 to  contract the segments when
 the central wedge is withdrawn4 ,a more
  convenient form of the instrument1    
however1 is obtained by placing the     
segments in a circular box1 with one end
 projecting2 and supporting each        
segment in the box by a tenon1 which    
fits into a mortise in the cylindrical  
box4 ,to expand the segments1 a round   
tapered piece of steel1 like a drift1   
is forced into a central hole1 round    
which the segments are arranged4 ,a     
piece of steel tube1 also slit up to    
enable a central drift to expand it1    
answers very well2 but the thickness of 
that part of the tube in which  there   
requires to be spring enough to let the 
mandrel expand1 requires to  be         
sufficiently reduced to prevent the     
pieces from cracking when the  central  
drift is driven in by a hammer4 ,the    
drift is better when made with  a       
globular head1 so that it may be struck 

back by the hammer1 as well as be       
driven in4 ,an expanding mandrel1 with a
 central drift1 is more rapid in its    
operation than when the expansion is    
produced by means of a screw4    #dba4  
,q4--,will you explain the means that   
are adopted to regulate the  admission  
of steam to the cylinders8    ,a4--,in  
locomotives1 the admission of the steam 
from the boiler to the  cylinders is    
regulated by a valve called the         
regulator1 which is generally  placed   
immediately above the internal fire box1
 and is connected with two  copper      
pipes2--one conducting steam from the   
highest point of the dome down  to it1  
and the other conducting the steam that 
has passed through it along  the boiler 
to the upper part of the smoke box4     
,regulators may be divided  into two    
sorts1 viz41 those with1 sliding valves 
and steam ports1 and those  with conical
 valves and seats1 of which the latter  
kind are the best4 ,the  former kind    
have for the most part consisted of a   

circular valve and face1  with radial   
apertures1 the valve resembling the     
outstretched wings of a  butterfly1 and 
being made to revolve on its central    
pivot by connecting  links between its  
outer edges1 or by its central spindle4 
,in some of  ,stephenson's engines the  
regulator consists of a slide valve     
covering a  port on the top of the valve
 chests4 ,a rod passes from this valve  
through  the smoke box below the boiler1
 and by means of a lever parallel to the
  starting lever1 is brought up to the  
engineer's reach4 ,cocks were at first  
used as regulators1 but were given up1  
as they were found liable to stick      
fast4 ,a gridiron slide valve has been  
used by ,stephenson1 which consists of  
a perforated square moving upon a face  
with an equal number of holes4 ,this    
plan of a valve gives1 with a small     
movement1 a large area of opening4 ,in  
,bury's engines a sort of conical plug  
is used1 which is withdrawn by  turning 
the handle in front of the fire box3 a  

spiral grove of a very large  pitch is  
made in the valve spindle1 in which fits
 a pin fixed to the  boiler1 and by     
turning the spindle an end motion is    
given to it1 which  either shuts or     
opens the steam passage according to the
 direction in which  it is turned4 ,the 
best regulator would probably be a valve
 of the  equilibrium description1 such  
as is used in the ,cornish engine3 there
 would  be no friction in such a        
regulator1 and it could be opened or    
shut with a  small amount of force4     
,such valves1 indeed1 are now sometimes 
employed for  regulators in locomotives4
          ,,chapter ,,viii4             
,,constructive ,,details ,,of ,,engines4
      ,,pumping ,,engines4    #dbb4     
,q4--,will you explain the course of    
procedure in the erection of a  pumping 
engine1 such as ,boulton and ,watt      
introduced into ,cornwall8    ,a4--,the 
best instructions on this subject are   
those of ,mr4 ,watt himself1  which are 
as follows3--,having fixed on the proper

 situation of the pump in  the pit1 from
 its centre measure out the distance to 
the centre of the  cylinder1 from which 
set off all the other dimensions of the 
house1  including the thickness of the  
walls1 and dig out the whole of the     
included  ground to the depth of the    
bottom of the cellar1 so that the bottom
 of the  cylinder may stand on a level  
with the natural ground of the place1 or
  lower1 if convenient1 for the less the
 height of the house above the  ground1 
the firmer it will be4 ,the foundations 
of the walls must be laid at  least two 
feet lower than the bottom of the       
cellar1 unless the foundation  be firm  
rock2 and care must be taken to leave a 
small drain into the pit  quite through 
the lowest part of the foundation of the
 lever wall1 to let  off any water that 
may be spilt in the engine house1 or may
 naturally come  into the cellar4 ,if   
the foundation at that depth does not   
prove good1 you  must either go down to 
a better if in your reach1 or make it   

good by a  platform of wood or piles1 or
 both4    #dbc4 ,q4--,these directions  
refer to the foundations8    ,a44--,yes2
 but ,i will now proceed to the other   
parts4 ,within the house1  low walls    
must be built to carry the cylinder     
beams1 so as to leave  sufficient room  
to come at the holding down bolts1 and  
the ends of these  beams must also be   
lodged in the wall ,the lever wall must 
be built in the  firmest manner1 and run
 solid1 course by course1 with thin lime
 mortar1  care being taken that the lime
 has not been long slaked4 ,if the house
 be  built of stone1 let the stones be  
large and long1 and let many headers be 
laid through the wall3 it should also be
 a rule1 that every stone be laid  on   
the broadest bed it has1 and never set  
on its edge4 ,a course or two  above the
 lintel of the door that leads to the   
condenser1 build into the  wall two     
parallel flat thin bars of iron equally 
distant from each other1  and from the  
outside and inside of the wall1 and     

reaching the whole breadth  of the lever
 wall4 ,about a foot higher in the wall1
 lay at every four feet  of the breadth 
of the front1 other bars of the same    
kind at right angles to  the former     
course1 and reaching quite through the  
thickness of the wall2  and at each     
front corner lay a long bar in the      
middle of the side walls1  and reaching 
quite through the front wall2 if these  
bars are #aj feet or #ab  feet long it  
will be sufficient4 ,when the house is  
built up nearly to the  bottom of the   
opening under the great beam another    
double course of bars is  to be built   
in1 as has been directed4 ,at the level 
of the upper cylinder  beams1 holes must
 be left in the walls for their ends1   
with room to move  them laterally1 so   
that the cylinder may be got in2 and    
smaller holes must  be left quite       
through the walls for the introduction  
of iron bars1 which  being firmly       
fastened to the cylinder beams at one   
end1 and screwed at the  other or outer 

end1 will serve1 by their going through 
both the front and  back walls1 to bind 
the house more firmly together4 ,the    
spring beams or  iron bars fastened to  
them must reach quite through the back  
wall1 and be  keyed or screwed up tight2
 and they must be firmly fastened to the
 lever  wall on each side1 either by    
iron bars1 firm pieces of wood1 or long 
strong  stones1 reaching far back into  
the wall4 ,they must also be bedded     
solidly1  and the residue of the opening
 must be built up in the firmest manner4
    #dbd4 ,q4--,if there be a deficiency
 of water for the purpose of            
condensation1 what course should be     
pursued8    ,a4--,if there be no water  
in the neighborhood that can be employed
 for the  purpose of condensation1 it   
will be necessary to make a pond1 dug in
 the  earth1 for the reception of the   
water delivered by the air pump1 to the 
end  that it may be cooled and used     
again for the engine4 ,the pond may be  
three  or four feet deep1 and lined with

 turf1 puddled1 or otherwise made water 
tight4 ,throwing up the water into the  
air in the form of a jet to cool it1    
has been found detrimental2 as the water
 is then charged with air which         
vitiates the vacuum4    #dbe4 ,q4--,how 
is the piston of a pumping engine       
packed8    ,a4--,to pack the piston1    
take sixty common-sized white or        
untarred  rope-yarns1 and with them     
plait a gasket or flat rope as close and
 firm as  possible1 tapering for        
eighteen inches at each end1 and long   
enough to go  round the piston1 and     
overlapped for that length2 coil this   
rope the thin  way as hard as possible1 
and beat it with a sledge hammer until  
its breadth  answers the place2 put it  
in and beat it down with a wooden drift 
and a  hand mallet1 pour some melted    
tallow all around1 then pack in a layer 
of  white oakum half an inch thick1 so  
that the whole packing may have the     
depth of five to six inches1 depending  
on the size of the engine2 finally1     

screw down the junk ring4 ,the packing  
should be beat solid1 but not too  hard1
 otherwise it will create so great a    
friction as to prevent the easy  going  
of the engine4 ,abundance of tallow     
should be allowed1 especially at  first2
 the quantity required will be less as  
the cylinder grows smooth4 ,in  some of 
the more modern pumping engines1 the    
piston is provided with  metallic       
packing1 consisting for the most part of
 a single ring with a  tongue piece to  
break the joint1 and packed behind with 
hemp4 ,the upper  edge of the metallic  
ring is sharpened away from the inside  
so as to permit  more conveniently the  
application of hemp packing behind it2  
and the junk  ring is made much the same
 as if no metallic packing were         
employed4    #dbf4 ,q4--,will you       
explain the mode of putting the engine  
into operation8    ,a4--,to set the     
engine going1 the steam must be raised  
until the pressure  in the steam pipe is
 at least equal to three pounds on the  

square inch2 and  when the cylinder     
jacket is fully warmed1 and steam issues
 freely from the  jacket cock1 open all 
the valves or regulators2 the steam will
 then  forcibly blow out the air or     
water contained in the eduction pipe1   
and to  get rid of the air in the       
cylinder1 shut the steam valve after    
having blown  through the engine for a  
few minutes4 ,the cold water round the  
condenser  will condense some of the    
steam contained in the eduction pipe1   
and its  place will be supplied by some 
of the air from the cylinder4 ,the steam
  valve must again be opened to blow out
 that air1 and the operation is to be   
repeated until the air is all drawn out 
of the cylinder4 ,when that is the  case
 shut all the valves1 and observe if the
 vacuum gauge shows a vacuum in  the    
condenser2 when there is a vacuum       
equivalent to three inches of  mercury1 
open the injection a very little1 and   
shut it again immediately2  and if this 
produces any considerable vacuum1 open  

the exhausting valve a  very little way1
 and the injection at the same time4 ,if
 the engine does not  now commence its  
motion1 it must be blown through again  
until it moves4 ,if  the engine be      
lightly loaded1 or if there be no water 
in the pumps1 the  throttle valve must  
be kept nearly closed1 and the top and  
exhaustion  regulators must be opened   
only a very little way1 else the engine 
will make  its stroke with violence1 and
 perhaps do mischief4 ,if there is much 
unbalanced weight on the pump end1 the  
plug which opens the steam valve  must  
be so regulated1 that the valve will    
only be opened very slightly2 and  if   
after a few strokes it is found that the
 engine goes out too slowly1 the  valve 
may be then so adjusted as to open      
wider4 ,the engine should always be     
made to work full stroke1 that is1 until
 the catch pins be made to come  within 
half an inch of the springs at each end1
 and the piston should stand  high      
enough in the cylinder when the engine  

is at rest1 to spill over into  the     
perpendicular steam pipe any water which
 may be condensed above it2 for  if     
water remain upon the piston1 it will   
increase the consumption of steam4      
,when the engine is to be stopped1 shut 
the injection valve and secure it1  and 
adjust the tappets so as to prevent the 
exhausting valve from opening  and to   
allow the steam valve to open and remain
 open1 otherwise a partial  vacuum may  
arise in the cylinder1 and it may be    
filled with water from the  injection or
 from leaks4 ,a single acting engine1   
when it is in good order1  ought to be  
capable of going as slow as one stroke  
in ten minutes1 and as  fast as ten     
strokes in one minute2 and if it does   
not fulfil these  conditions1 there is  
some fault which should be ascertained  
and remedied4    #dbg4 ,q4--,your       
explanation has reference to the pumping
 engine as  introduced into ,cornwall by
 ,watt3 have any modifications been     
since made  upon it8    ,a4--,in the    

modern ,cornish engines the steam is    
used very expansively1 and  a high      
pressure of steam is employed4 ,in some 
cases a double cylinder  engine is used1
 in which the steam1 after having given 
motion to a small  piston on the        
principle of a high pressure engine1    
passes into a larger  cylinder1 where it
 operates on the principle of a         
condensing engine2 but  there is no     
superior effect gained by the use of two
 cylinders1 and there  is greater       
complexity in the apparatus4 ,instead of
 the lever walls1 cast  iron columns are
 now frequently used for supporting the 
main beam in  pumping engines1 and the  
cylinder end of the main beam is        
generally made  longer than the pump end
 in engines made in ,cornwall1 so as to 
enable the  cylinder to have a long     
stroke1 and the piston to move quickly1 
without  communicating such a velocity  
to the pump buckets as will make them   
work  with such a shock as to wear      
themselves out quickly4 ,a high pressure

 of  steam1 too1 can be employed where  
the stroke is long1 without involving   
the  necessity of making the working    
parts of such large dimensions as would 
otherwise be necessary2 for the strength
 of the parts of a single acting  engine
 will require to be much the same1      
whatever the length of the stroke  may  
be4    #dbh4 ,q4--,what kind of pump is 
mostly used in draining deep mines8     
,a4--,the pump now universally preferred
 is the plunger pump1 which admits  of  
being packed or tightened while the     
engine is at work2 but the lowest  lift 
of a mine is generally supplied with a  
pump on the suction principle1  both    
with the view of enabling the lowest    
pipe to follow the water with  facility 
as the shaft is sunk deeper1 and to     
obviate the inconvenience of  the valves
 of the pump being rendered inaccessible
 by any flooding in the  mine4 ,the pump
 valves of deep mines are a perpetual   
source of expense and  trouble1 as from 
the pressure of water upon them it is   

difficult to prevent  them from closing 
with violence2 and many expedients have 
been contrived to  mitigate the evil1 of
 which the valve known as ,harvey and   
,west's valve has  perhaps gained the   
widest acceptation4    #dbi4 ,q4--,will 
you describe ,harvey and ,west's pump   
valve8    ,a4--,this valve is a         
compromise between the equilibrium      
valve1 of the kind  employed for        
admitting the steam to and from the     
cylinder in single acting  engines1 and 
the common spindle valve formerly used  
for that purpose2 and  to comprehend its
 action1 it is necessary that the action
 of the  equilibrium valve1 which has   
been already represented fig4 #cd1      
should first  be understood4 ,this valve
 consists substantially of a cylinder   
open at both  ends1 and capable of      
sliding upon a stationary piston fixed  
upon a rod the  length of the cylinder1 
which proceeds from the centre of the   
orifice the  valve is intended to close4
 ,it is clear1 that when the cylinder is

 pressed  down until its edge rests upon
 the bottom of the box containing it1   
the  orifice of the pipe must be closed1
 as the steam can neither escape past   
the edge of the cylinder nor between the
 cylinder and the piston2 and it is     
equally clear1 that as the pressure upon
 the cylinder is equal all around  it1  
and the whole of the downward pressure  
is maintained by the stationary  piston1
 the cylinder can be raised or lowered  
without any further exertion  of force  
than is necessary to overcome the       
friction of the piston and of  the rod  
by which the cylinder is raised4        
,instead of the rubbing surface of  a   
piston1 however1 a conical valve face   
between the cylinder and piston is      
employed1 which is tight only when the  
cylinder is in its lowest position2  and
 there is a similar face between1 the   
edge of the cylinder and the  bottom of 
the box in which it is placed4 ,the     
moving part of the valve1 too1  instead 
of being a perfect cylinder1 is bulged  

outward in the middle1 so as  to permit 
the steam to escape past the stationary 
piston when the  cylindrical part of the
 valve is raised4 ,it is clear1 that if 
such a valve  were applied to a pump1 no
 pressure of water within the pump would
 suffice  to open it1 neither would any 
pressure of water above the valve cause 
it to  shut with violence2 and if an    
equilibrium valve1 therefore1 be used as
 a  pump valve at all1 it must be opened
 and shut by mechanical means4 ,in      
,harvey and ,west's valves1 however1 the
 equilibrium principle is only          
partially adopted2 the lower face is    
considerably larger in diameter than    
the upper face1 and the difference      
constitutes an annulus of pressure1     
which will cause the valve to open or   
shut with the same force as a spindle   
valve of the area of the annulus4 ,to   
deaden the shock still more             
effectually1 the lower face of the valve
 is made to strike upon end wood  driven
 into an annular recess in the pump     

bucket2 and valves thus  constructed    
work with very little noise or tremor2  
but it is found in  practice1 that the  
use of ,harvey and ,west's valve1 or any
 contrivance of a  similar kind1 adds   
materially to the load upon the pump1   
especially in low  lifts where the      
addition of a load1 to the valve makes a
 material addition  to the total        
resistance which the engine has to      
overcome4 ,instead of end  wood driven  
into a recess for the valve to strike   
upon1 a mixture of tin  and lead cast in
 a recess is now frequently used1 and is
 found to be  preferable to the wood4   
#dcj4 ,q4--,is there any other kind of  
pump valve which is free from the       
shocks incidental to the working of     
common valves8    ,a4--,in some cases   
canvass valves are used for pumps1 with 
the effect of  materially mitigating the
 shock2 but they require frequent       
renewal1 and are  of inferior           
eligibility in their action to the slide
 valve1 which might in  many cases be   

applied to pumps without inconvenience4 
#dca4 ,q4--,could not a form of pump be 
devised capable of working without      
valves at all8    ,a44--,it appears     
probable1 that by working a common      
reciprocating pump at  a high speed1 a  
continuous flow of water might be       
maintained through the  pipes in such a 
way as to render the existence of any   
valves superfluous  after once the      
action was begun1 the momentum of the   
moving water acting in  fact as valves4 
,the centrifugal pump1 however1         
threatens to supersede pumps  of every  
other kind2 and if the centrifugal pump 
be employed there will be  no necessity 
for pump valves at all4 ,there is less  
loss of effect by the  centrifugal pump 
than by the common pump4    #dcb4       
,q4--,what is the best form of the      
centrifugal pump8    ,a4--,there are two
 forms in which the centrifugal pump may
 be applied to  mines2--that in which   
the arms diverge from the bottom1 like  
the letter ,v2  and that in which       

revolving arms are set in a tight case  
near the bottom of  the mine1 and are   
turned by a shaft from the surface4     
,such pumps both draw  and force2 and   
either by arranging them in a succession
 of lifts in the  shaft of the mine1 or 
otherwise1 the water may be drawn       
without  inconvenience from any depth4  
,the introduction of the centrifugal    
pump  would obviously extinguish the    
single acting engine1 as rotative       
engines  working at a high speed would  
be the most appropriate form of engine  
where  the centrifugal pump was         
employed4    #dcc4 ,q4--,this would not 
be a heavy deprivation8    ,a4--,the    
single acting engine is a remnant of    
engineering barbarism which  must now be
 superseded by more compendious         
contrivances4 ,the ,cornish  engines1   
though rudely manufactured1 are very    
expensive in production1 as a  large    
engine does but little work2 whereas by 
employing a smaller engine1  moving with
 a high speed1 the dimensions may be so 

far diminished that the  most refined   
machinery may be obtained at less than  
the present cost4    #dcd4 ,q4--,are not
 the ,cornish engines more economical in
 fuel than other  engines8    ,a4--,it  
is a mistake to suppose that there is   
any peculiar virtue in the  existing    
form of ,cornish engine to make it      
economical in fuel1 or that a  less     
lethargic engine would necessarily be   
less efficient4 ,the large duty  of the 
engines in ,cornwall is traceable to the
 large employment of the  principle of  
expansion1 and to a few other causes    
which may be made of  quite as decisive 
efficacy in smaller engines working with
 a quicker speed2  and there is         
therefore no argument in the performance
 of the present  engines against the    
proposed substitution4        ,,various 
,,forms ,,of ,,marine ,,engines4        
#dce4 ,q4--,what species of paddle      
engine do you consider to be the best8  
,a4--,the oscillating engine4    #dcf4  
,q4--,will you explain the grounds of   

that preference8    ,a4--,the engine    
occupies little space1 consists of few  
parts1 is easily  accessible for        
repairs1 and may be both light and      
strong at the same time4  ,in the case  
of large engines the crank in the       
intermediate shaft is a  disadvantage1  
as it is difficult to obtain such a     
forging quite sound4 ,but  by forging it
 in three cranked flat bars1 which are  
then laid together and  welded into a   
square shaft1 a sound forging will be   
more probable1 and the  bars should be  
rounded a little on the sides which are 
welded to allow the  scoriae to escape  
during that operation4 ,it is important 
in so large a  forging not to let the   
fire be too fierce1 else the surface of 
the iron  will be burnt before the heart
 is brought to a welding heat4 ,in some 
cases  in oscillating engines the air   
pump has been wrought by an eccentric1  
and  that may at any time be done where 
doubt of obtaining a sound intermediate 
shaft is entertained2 but the precaution

 must be taken to make the  eccentric   
very wide so as to distribute the       
pressure over a large surface1  else the
 eccentric will be apt to heat4    #dcg4
 ,q4--,have not objections been brought 
against the oscillating engine8         
,a4--,in common with every other        
improvement1 the oscillating engine1 at 
the time of its introduction1           
encountered much opposition4 ,the       
cylinder1 it  was said1 would become    
oval1 the trunnion bearings would be    
liable to heat  and the trunnion joints 
to leak1 the strain upon the trunnions  
would be apt  to bend in or bend out the
 sides of the cylinder2 and the         
circumstance of  the cylinder being     
fixed across its centre1 while the shaft
 requires to  accommodate itself to the 
working of the ship1 might1 it was      
thought1 be  the occasion of such a     
strain upon the trunnions as would      
either break them  or bend the piston   
rod4 ,it is a sufficient reply to these 
objections to say  that they are all    

hypothetical1 and that none of them in  
practice have been  found to exist--to  
such an extent at least as to occasion  
any  inconvenience2 but it is not       
difficult to show that they are         
altogether  unsubstantial1 even without 
a recourse to the disproofs afforded by 
experience4    #dch4 ,q4--,is there not 
a liability in the cylinder to become   
oval from the  strain thrown on it by   
the piston8    ,a4--,there is1 no doubt1
 a tendency in oscillating engines for  
the  cylinder and the stuffing box to   
become oval1 but after a number of      
years'  wear it is found that the amount
 of ellipticity is less than that which 
is  found to exist in the cylinders of  
side lever engines after a similar      
trial4 ,the resistance opposed by       
friction to the oscillation of the      
cylinder is so small1 that a man is     
capable of moving a large cylinder with 
one hand2 whereas in the side lever     
engine1 if the parallel motion be in    
the least untrue1 which is1 at some time

 or other1 an almost inevitable         
condition1 the piston is pushed with    
great force against the side of the     
cylinder1 whereby a large amount of wear
 and friction is occasioned4 ,the       
trunnion bearings1 instead of being     
liable to heat like other journals1 are 
kept down to the temperature of the     
steam by the flow of steam passing      
through them2 and the trunnion packings 
are not liable to leak when the         
packings1 before being introduced1 are  
squeezed in a cylindrical mould4        
#dci4 ,q4--,might not the eduction      
trunnions be immersed in water8         
,a4--,in some cases a hollow1 or lantern
 brass1 about one third or one  fourth  
the length of the packing space1 and    
supplied with steam or water by  a pipe1
 is introduced in the middle of the     
packing1 so that if there be any        
leakage through the trunnion1 it will be
 a leakage of steam or water1 which     
will not vitiate the vacuum2 but in     
ordinary cases this device will not be  

necessary1 and it is not commonly       
employed4 ,it is clear that there can be
  no buckling of the sides of the       
cylinder by the strain upon the         
trunnions1  if the cylinder be made     
strong enough1 and in cylinders of the  
ordinary  thickness such an action has  
never been experienced2 nor is it the   
fact1  that the intermediate shaft of   
steam vessels1 to which part alone the  
motion is communicated by the engine1   
requires to adapt itself to the         
altering forms of the vessel1 as the    
engine and intermediate shaft are       
rigidly connected1 although the paddle  
shaft requires to be capable of such  an
 adaptation4 ,even if this objection    
existed1 however1 it could easily be    
met by making the crank pin of the ball 
and socket fashion1 which would  permit 
the position of the intermediate shaft1 
relatively with that of the  cylinder1  
to be slightly changed1 without throwing
 an undue strain upon any  of the       
working parts4    #ddj4 ,q4--,is the    

trunk engine inferior to the            
oscillating8    ,a4--,a very elegant and
 efficient arrangement of trunk engine  
suitable for  paddle vessels has        
latterly been employed by ,messrs4      
,rennie1 of which all  the parts        
resemble those of ,penn's oscillating   
engine except that the  cylinders are   
stationary instead of being movable2 and
 a round trunk or  pipe set upon the    
piston1 and moving steam tight through  
the cylinder  cover1 enables the        
connecting rod which is fixed to the    
piston to vibrate  within it to the     
requisite extent4 ,but the vice of all  
trunk engines is  that they are         
necessarily more wasteful of steam1 as  
the large mass of  metal entering into  
the composition of the trunk1 moving as 
it does  alternately into the atmosphere
 and the steam1 must cool and condense a
  part of the steam4 ,the radiation of  
heat from the interior of the trunk     
will have the same operation1 though in 
vertical trunk engines the loss  from   

this cause might probably be reduced by 
filling the trunk with oil1 so  far as  
this could be done without the oil being
 spilt over the edge4    #dda4          
,q4--,what species of screw engine do   
you consider the best8    ,a4--,i am    
inclined to give the preference to a    
variety of the horizontal  steeple      
engine1 such as was first used in       
,h4,m4,s4 ,amphion4 ,in this engine  the
 cylinders lie on their sides1 and they 
are placed near the side of the  vessel 
with their mouths pointing to the keel4 
,from each cylinder two long  piston    
rods proceed across the vessel to a     
cross head working in guides2  and from 
this cross head a connecting rod returns
 back to the centre of the  vessel and  
gives motion to the crank4 ,the piston  
rods are so placed in the  piston that  
one of them passes above the crank      
shaft1 and the other below  the crank   
shaft4 ,the cross head lies in the same 
horizontal plane as the  centre of the  
cylinder1 and a lug projects upwards    

from the cross head to  engage one      
piston rod1 and downwards from the cross
 head to engage the  other piston rod4  
,the air pump is double acting1 and its 
piston or bucket  has the same stroke as
 the piston of the engine4 ,the air pump
 bucket  derives its motion from an arm 
on the cross head1 and a similar arm is 
usually employed in engines of this     
class to work the feed and bilge pumps4 
#ddb4 ,q4--,is not inconvenience        
experienced in direct acting screw      
engines  from the great velocity of     
their motion8    ,a4--,not if they are  
properly constructed2 but they require  
to be much  stronger1 to be fitted with 
more care1 and to have the bearing      
surfaces  much larger than is necessary 
in engines moving slowly4 ,the momentum 
of the  reciprocating parts should also 
be balanced by a weight applied to the  
crank or crank shaft1 as is done in     
locomotives4 ,a very convenient         
arrangement for obtaining surface is to 
form the crank of each engine of  two   

cast iron discs cast with heavy sides1  
the excess of weight upon the  heavy    
sides being nearly equal to that of the 
piston and its connections4  ,when the  
piston is travelling in one direction   
the weights are travelling  in the      
opposite2 and the momentum of the piston
 and its attachments1 which  is arrested
 at each reciprocation1 is just balanced
 by the equal and  opposite momentum of 
the weights4 ,one advantage of the      
horizontal engine  is1 that a single    
engine may be employed1 whereby greater 
simplicity of the  machinery and greater
 economy of fuel will be obtained1 since
 there will be  less radiating surface  
in one cylinder than in two4            
,,cylinders1 ,,pistons1 ,,and ,,valves1 
#ddc4 ,q4--,is it a beneficial practice 
to make cylinders with steam  jackets8  
,a4--,in ,cornwall1 where great         
attention is paid to economy of fuel1   
all  the engines are made with steam    
jackets1 and in some cases a flue winds 
spirally round the cylinder1 for keeping

 the steam hot4 ,mr4 ,watt1 in his      
early practice1 discarded the steam     
jacket for a time1 but resumed it       
again1 as he found its discontinuance   
occasioned a perceptible waste of  fuel2
 and in modern engines it has been found
 that where a jacket is used  less coal 
is consumed than where the use of a     
jacket is rejected4 ,the cause  of this 
diminished effect is not of very easy   
perception1 for the jacket  exposes a   
larger radiating surface for the escape 
of the heat than the  cylinder2         
nevertheless1 the fact has been         
established beyond doubt by  repeated   
trials1 that engines provided with a    
jacket are more economical  than engines
 without one4 ,the exterior of the      
cylinder1 or jacket1 should  be covered 
with several plies of felt1 and then be 
cased in timber1 which  must be very    
narrow1 the boards being first dried in 
a stove1 and then  bound round the      
cylinder with hoops1 like the staves of 
a cask4 ,in many of  the ,cornish       

engines the steam is let into casings   
formed in the cylinder  cover and       
cylinder bottom1 for the further        
economisation of the heat1 and  the     
cylinder stuffing box is made very deep1
 and a lantern or hollow brass  is      
introduced into the centre of the       
packing1 into which brass the steam     
gains admission by a pipe provided for  
the purpose2 so that in the event of    
the packing becoming leaky1 it will be  
steam that will be leaked into the      
cylinder instead of air1 which1 being   
incondensable1 would impair the         
efficiency of the engine4 ,a lantern    
brass1 of a similar kind1 is sometimes  
introduced into the stuffing boxes of   
oscillating engines1 but its use  there 
is to receive the lateral pressure of   
the piston rod1 and thus take  any      
strain off the packing4    #ddd4        
,q4--,will you explain the proper course
 to pursue in the production  of        
cylinders8    ,a4--,in all engines the  
valve casing1 if made in a separate     

piece from the  cylinder1 should be     
attached by means of a metallic joint1  
as such a  barbarism as a rust joint in 
such situations is no longer            
permissible4 ,in  the case of large     
engines with valve casings suitable for 
long slides1 an  expansion joint in the 
valve casing should invariably be       
inserted1  otherwise the steam1 by      
gaining admission to the valve casing   
before it can  enter the cylinder1      
expands the casing while the cylinder   
remains unaltered  in its dimensions1   
and the joints are damaged1 and in some 
cases the  cylinder is cracked by the   
great strain thus introduced4 ,the chest
 of the  blow-through valve is very     
commonly cast upon the valve casing2 and
 in  engines where the cylinders are    
stationary this is the most convenient  
practice4 ,all engines1 where the valve 
is not of such a construction as to     
leave the face when a pressure exceeding
 that of the steam is created in  the   
cylinder by priming or otherwise1 should

 be provided with an escape  valve to   
let out the water1 and such valve should
 be so constructed that  the water      
cannot fly out with violence over the   
attendants2 but it should  be conducted 
away by a suitable pipe1 to a place     
where its discharge can  occasion no    
inconvenience4 ,the stuffing boxes of   
all engines which cannot  be stopped    
frequently to be repacked1 should be    
made very deep2 metallic  packing in the
 stuffing box has been used in some     
engines1 consisting in  most instances  
of one or more rings1 cut1 sprung1 and  
slipped upon the  piston rod before the 
cross head is put on1 and packed with   
hemp behind4  ,this species of packing  
answers very well when the parallel     
motion is true1  and the piston rod free
 from scratches1 and it accomplishes a  
material  saving of tallow4 ,in some    
cases a piece of sheet brass1 packed    
behind with  hemp1 has been introduced  
with good effect1 a flange being turned 
over on  the under edge of the brass to 

prevent it from slipping up or down with
 the  motion of the rod4 ,the sheet     
brass speedily puts an excellent polish 
upon  the rod1 and such a packing is    
more easily kept1 and requires less     
tallow  than where hemp alone is        
employed4 ,in side lever marine engines 
the  attachments of the cylinder to the 
diagonal stay are generally made of too 
small an area1 and the flanges are made 
too thick4 ,a very thick flange cast  on
 any part of a cylinder endangers the   
soundness of the cylinder1 by  inducing 
an unequal contraction of the metal2 and
 it is a preferable course  to make the 
flange for the attachment or the framing
 thin1 and the surface  large--the bolts
 being turned bolts and nicely fitted4  
,if from malformation  in this part the 
framing works to an inconvenient extent1
 the best  expedient appears to be the  
introduction of a number of steel       
tapered  bolts1 the holes having been   
previously bored out2 and if the flanges
 be  thick enough1 square keys may also 

be introduced1 half into one flange and 
half into the other1 so as to receive   
the strain4 ,if the jaw cracks or       
breaks away1 however1 it will be best to
 apply a malleable iron hoop around  the
 cylinder to take the strain1 and this  
will in all cases be the  preferable    
expedient1 where from any peculiarities 
of structure there is a  difficulty in  
introducing bolts and keys of sufficient
 strength4    #dde4 ,q4--,which is the  
most eligible species of piston8        
,a4--,for large engines1 pistons with a 
metallic packing1 consisting of a       
single ring1 with the ends morticed into
 one another1 and a piece of metal  let 
in flush over the joint and riveted to  
one end of the ring1 appears to  be the 
best species of piston2 and if the      
cylinder be oscillating1 it will  be    
expedient to chamfer off the upper edge 
of the ring on the inner side1  and to  
pack it at the back with hemp4 ,if the  
cylinder be a stationary one1  springs  
may be substituted for the hemp packing1

 but in any case it will be  expedient  
to make the vertical joints of the ends 
of the ring run a little  obliquely1 so 
as to prevent the joint forming a ridge 
in the cylinder4 ,for  small pistons two
 rings may be employed1 made somewhat   
eccentric internally  to give a greater 
thickness of metal in the centre of the 
ring2 these rings  must be set one above
 the other in the cylinder1 and the     
joints1 which are  oblique1 must be set 
at right angles with one another1 so as 
to obviate any  disposition of the      
rings1 in their expansion1 to wear the  
cylinder oval4  ,the rings must first be
 turned a little larger than the        
diameter of the  cylinder1 and a piece  
is then to be cut out1 so that when the 
ends are  brought together the ring will
 just enter within the cylinder4 ,the   
ring1  while retained in a state of     
compression1 is then to be put in the   
lathe  and turned very truly1 and       
finally it is to be hammered on the     
inside with  the small end of the       

hammer1 to expand the metal1 and thus   
increase the  elasticity4    #ddf4      
,q4--,the rings should be carefully     
fitted to one another laterally8        
,a4--,the rings are to be fitted        
laterally to the piston1 and to one     
another1 by scraping--a steady pin being
 fixed upon the flange of the  piston1  
and fitting into a corresponding hole in
 the lower ring1 to keep  the lower ring
 from turning round2 and a similar pin  
being fixed into the  top edge of the   
lower ring to prevent the upper ring    
from turning round2  but the holes into 
which these pins fit must be made       
oblong1 to enable the  rings to press   
outward as the rubbing surfaces wear4   
,in most cases it will  be expedient to 
press the packing rings out with springs
 where they are not  packed behind with 
hemp1 and the springs should be made    
very strong1 as the  prevailing fault of
 springs is their weakness4 ,sometimes  
short bent  springs1 set round at       
regular intervals between the packing   

rings and body  of the piston1 are      
employed1 the centre of each spring     
being secured by a  steady pin or bolt  
screwed into the side of the piston2 but
 it will not  signify much what kind of 
springs is used1 provided they have     
sufficient  tension4 ,when pistons are  
made of a single ring1 or of a          
succession of  single rings1 the        
strength of each ring should be tested  
previously to its  introduction into the
 piston1 by means of a lever loaded by a
 heavy weight4    #ddg4 ,q4--,what kind 
of piston is employed by ,messrs4 ,penn8
    ,a4--,messrs4 ,penn's piston for    
oscillating engines has a single packing
  ring1 with a tongue piece1 or mortice 
end1 made in the manner already         
described4 ,the ring is packed behind   
with hemp packing1 and the piece of     
metal which covers the joint is a piece 
of thick sheet copper or brass1 and  is 
indented into the iron of the ring1 so  
as to offer no obstruction to the       
application of the hemp4 ,the ring is   

fitted to the piston only on the under  
edge2 the top edge is rounded to a point
 from the inside1 and the junk ring     
does not bear upon it1 but the junk ring
 squeezes down the hemp packing  between
 the packing ring and the body of the   
piston4    #ddh4 ,q4--,how should the   
piston rod be secured to the piston8    
,a4--,the piston rod1 where it fits into
 the piston1 should have a good  deal of
 taper2 for if the taper be too small   
the rod will be drawn through  the hole1
 and the piston will be split asunder4  
,small grooves are sometimes  turned out
 of the piston rod above and below the  
cutter hole1 and hemp is  introduced in 
order to make the piston eye tight4     
,most piston rods are  fixed to the     
piston by means of a gib and cutter1 but
 in some cases the  upper portion of the
 rod within the eye is screwed1 and it  
is fixed into  the piston by means of an
 indented nut4 ,this nut is in some     
cases  hexagonal1 and in other cases the
 exterior forms a portion of a cone     

which  completely fills a corresponding 
recess in the piston2 but nuts made in  
this way become rusted into their seat  
after some time1 and cannot be  started 
again without much difficulty4 ,messrs4 
,miller1 ,ravenhill  ,co4 fix  in their 
piston rods by means of an indented     
hexagonal nut1 which may be  started by 
means of an open box key4 ,the thread of
 the screw is made flat  upon the one   
side and much slanted on the other1     
whereby a greater strength  is secured1 
without creating any disposition to     
split the nut4 ,in side  lever engines  
it is a judicious practice to add a nut 
to the top of the  piston rod1 in       
addition to the cutter for securing the 
piston rod to the  cross head4 ,in a    
good example of an engine thus provided1
 the piston rod is  #g in4 in diameter1 
and the screw #e in42 the part of the   
rod which fits into  the cross head eye 
is #a ft4 #e-a_/b in4 long1 and tapers  
from #f-a_/b in4 to  #f-ac_/af in4      
diameter4 ,this proportion of taper is a

 good one2 if the taper  be less1 or if 
a portion of the piston rod within the  
cross head eye be  left untapered1 as is
 sometimes the case1 it is very         
difficult to detach  the parts from one 
another4    #ddi4 ,q4--,which is the    
most beneficial construction of slide   
valve8    ,a4--,the best construction of
 slide valve appears to be that adopted 
by  ,messrs4 ,penn for their larger     
engines1 and which consists of a three  
ported  valve1 to the back of which a   
ring is applied of an area equal to that
 of  exhaustion port1 and which1 by     
bearing steam tight against the back of 
the  casing1 so that a vacuum may be    
maintained within the ring1 puts the    
valve  in equilibrium1 so that it may be
 moved with an inconsiderable exercise  
of  force4 ,the back of the valve casing
 is put on like a door1 and its internal
  surface is made very true by scraping4
 ,there is a hole through the valve so  
as to conduct away any steam which may  
enter within the ring by leakage1  and  

the ring is kept tight against the back 
of the casing by means of a  ring       
situated beneath the bearing ring1      
provided with four lugs1 through  which 
bolts pass tapped into bosses on the    
back of the valve2 and1 by  unscrewing  
these bolts1--which may be done by means
 of a box key which  passes through     
holes in the casing closed with screwed 
plugs1--the lower  ring is raised       
upwards1 carrying the bearing ring      
before it4 ,the rings must  obviously be
 fitted over a boss upon the back of the
 valve2 and between the  rings1 which   
are of brass1 a gasket ring is          
interposed to compensate by its         
compressibility for any irregularity of 
pressure1 and each of the bolts is      
provided with a ratchet collar to       
prevent it from turning back1 so that   
the  engineer1 in tightening these      
bolts1 will have no difficulty in       
tightening  them equally1 if he counts  
the number of clicks made by the        
ratchet4 ,where  this species of valve  

is used1 it is indispensable that large 
escape valves  be applied to the        
cylinder1 as a valve on this            
construction is unable to  leave the    
face4 ,in locomotive engines1 the valve 
universally employed is  the common     
three ported valve4    #dej4 ,q4--,might
 not an equilibrium valve be so         
constructed by the  interposition of    
springs1 as to enable it to leave the   
cylinder face when  an internal force is
 applied8    ,a4--,that can no doubt be 
done1 and in some engines has been done4
 ,in the  screw steamer ,azof1 the valve
 is of the equilibrium construction1 but
 the  plate which carries the packing on
 which the top ring rests1 is an        
octagon1  and fits into an octagonal    
recess on the back of the valve4 ,below 
each side  of the octagon there is a    
bent flat spring1 which lifts up the    
octagonal  plate1 and with it the       
packing ring against the back of the    
valve casing2  and should water get into
 the cylinder1 it escapes by lifting the

 valve1  which is rendered possible by  
the compressibility of the springs4 ,an 
equivalent arrangement is shown in figs4
 #ci and #dj1 where the ring is  lifted 
by spiral springs4      ,illustration3  
,fig4 #ci4 ,,equilibrium ,,gridiron     
,,slide ,,valve4 ,longitudinal          
,section4 ,scale #c_/d inch  #a foot4   
#dea4 ,q4--,what species of valve is    
that shown in figs4 #ci and #dj8        
,illustration3 ,fig4 #dj4 ,,equilibrium 
,,gridiron ,,slide ,,valve4 ,back ,view 
with  ,ring removed4 ,scale #c_/d inch  
#a foot4    ,a4--,it is an equilibrium  
gridiron valve2 so called because it    
lets the  steam in and out by more than 
one port4  ,a ,a are the ordinary steam 
passages to the top and bottom of the   
cylinder2 ,b ,b is the ring which rubs  
against the back of the valve casing1   
and ,d is the eduction passage1 ,s ,s ,s
  ,s shows the limits of the steam      
space1 for the steam penetrates to the  
central chamber ,s ,s by the sides of   
the valve4 ,when the valve is opened    

upon the steam side1 the cylinder       
receives steam through both ports at    
that  end of the cylinder1 and both     
ports at the other end of the cylinder  
are at  the same time open to the       
eduction4 ,the benefit of this species  
of valve  is1 that it gives the same    
opening of the valve that is given in   
ordinary  engines1 with half the amount 
of travel2 or if three ports were made  
instead of two1 then it would give the  
same area of opening that is given  in  
common engines with one third the amount
 of travel4 ,for direct acting  screw   
engines this species of valve is now    
extensively used4    #deb4 ,q4--,will   
you describe the configuration and mode 
of attachment of  the eccentric by which
 the valve is moved8    ,a4--,in marine 
engines1 whether paddle or screw1 if    
moving at a slow rate  of speed1 the    
eccentric is generally loose upon the   
shaft1 for the purpose  of backing1 and 
is furnished with a back balance and    
catches1 so that it  may stand either in

 the position for going ahead1 or in    
that for going  astern4 ,the body of the
 eccentric is of cast iron1 and it is   
put on the  shaft in two pieces4 ,the   
halves are put together with rebated    
joints to  keep them from separating    
laterally1 and they are prevented from  
sliding  out by round steel pins1 each  
ground into both halves2 square keys    
would  probably be preferable to round  
pins in this arrangement1 as the pins   
tend  to wedge the jaws of the eccentric
 asunder4 ,in some cases the halves of  
the  eccentric are bolted together by   
means of flanges1 which is1 perhaps1 the
  preferable practice4 ,the eccentric   
hoop in marine and land engines is      
generally of brass2 it is expedient to  
cast an oil cup on the eccentric  hoop1 
and1 where practicable1 a pan should be 
placed beneath the eccentric  for the   
reception of the oil droppings4 ,the    
notch of the eccentric rod for  the     
reception of the pin of the valve shaft 
is usually steeled1 to prevent          

inconvenient wear2 for when the sides of
 the notch wear1 the valve movement  is 
not only disturbed1 but it is very      
difficult to throw the eccentric rod    
out of gear4 ,it is found to be         
preferable1 however1 to fit this notch  
with  a brass bush1 for the wear is then
 less rapid1 and it is an easy thing to 
replace this bush with another when it  
becomes worn4 ,the eccentric catches  of
 the kind usually employed in marine    
engines1 sometimes break off at the     
first bolt hole1 and it is preferable to
 have a bolt in advance of the  catch   
face1 or to have a hoop encircling the  
shaft with the catches welded  on it1   
the hoop itself being fixed by bolts or 
a key4 ,this hoop may either  be put on 
before the cranks in one piece or       
afterwards in two pieces4    #dec4      
,q4--,are such eccentrics used in direct
 acting screw engines8    ,a4--,no2     
direct acting screw engines are usually 
fitted with the link  motion and two    
fixed eccentrics4        ,,air ,,pump   

,,and ,,condenser4    #ded4 ,q4--,what  
are the details of the air pump8        
,a4--,the air pump bucket and valves are
 all of brass in modern marine  engines1
 and the chamber of the pump is lined   
with copper1 or made wholly  of brass1  
whereby a single boring suffices4 ,when 
a copper lining is used1  the pump is   
first bored out1 and a bent sheet of    
copper is introduced1  which is made    
accurately to fill the place1 by        
hammering the copper on the  inside4    
,air pump rods of ,muntz's metal or     
copper are much used4 ,iron rods        
covered with brass are generally wasted 
away where the bottom cone fits  into   
the bucket eye1 and if the casing be at 
all porous1 the water will  insinuate   
itself between the casing and the rod   
and eat away the iron4 ,if  iron rods   
covered with brass be used1 the brass   
casing should come some  distance into  
the bucket eye2 the cutter should be of 
brass1 and a brass  washer should cover 
the under side of the eye1 so as to     

defend the end of  the rod from the salt
 water4 ,rods of ,muntz's metal are     
probably on the  whole to be preferred4 
,it is a good practice to put a nut on  
the top of the  rod1 to secure it more  
firmly in the cross head eye1 where that
 plan can be  conveniently adopted4 ,the
 part of the rod which fits into the    
cross head  eye should have more taper  
when made of copper or brass1 than when 
made of  iron2 as1 if the taper be      
small1 the rod may get staved into the  
eye1  whereby its detachment will be    
difficult4    #dee4 ,q4--,what species  
of packing is used in air pumps8        
,a4--,metallic packing has in some      
instances been employed in air pump     
buckets1 but its success has not been   
such as to lead to its further          
adoption4 ,the packing commonly employed
 is hemp4 ,a deep solid block of  metal1
 however1 without any packing1 is often 
employed with a satisfactory  result2   
but this block should have circular     
grooves cut round its edge to  hold     

water4 ,where ordinary packing is       
employed1 the bucket should always be   
made with a junk ring1 whereby the      
packing may be easily screwed down at   
any time with facility4 ,in slow moving 
engines the bucket valve is  generally  
of the spindle or pot-lid kind1 but     
butterfly valves are  sometimes used4   
,the foot and delivery valves are for   
the most part of the  flap or hanging   
kind4 ,these valves all make a          
considerable noise in  working1 and are 
objectionable in many ways4 ,valves on  
,belidor's  construction1 which is in   
effect that of a throttle valve hung off
 the  centre1 were some years ago       
proposed for the delivery and foot      
valves2 and  it appears probable that   
their operation would be more           
satisfactory than  that of the valves   
usually employed4    #def4 ,q4--,where  
is the delivery valve usually situated8 
,a4--,some delivery valve seats are     
bolted into the mouth of the air pump1  
whereby access to the pump bucket is    

rendered difficult3 but more commonly   
the delivery valve is a flap valve      
exterior to the pump4 ,if delivery valve
  seats be put in the mouth of the air  
pump at all1 the best mode of fixing    
them appears to be that adopted by      
,messrs4 ,maudslay4 ,the top of the pump
  barrel is made quite fair across1 and 
upon this flat surface a plate          
containing the delivery valve is set1   
there being a small ledge all round  to 
keep it steady4 ,between the bottom of  
the stuffing box of the pump cover  and 
the eye of the valve seat a short pipe  
extends encircling the pump rod1  its   
lower end checked into the eye of the   
valve seat1 and its upper end  widening 
out to form the bottom of the stuffing  
box of the pump cover4 ,upon  the top of
 this pipe some screws press1 which are 
accessible from the top  of the stuffing
 box gland1 and the packing also aids in
 keeping down the  pipe1 the function of
 which is to retain the valve seat in   
its place4 ,when  the pump bucket has to

 be examined the valve seat may be slung
 with the  cover1 so as to come up with 
the same purchase4 ,for the bucket      
valves of  such pumps ,messrs4 ,maudslay
 employ two or more concentric ring     
valves with  a small lift4 ,these valves
 have given a good deal of trouble in   
some cases1  in consequence of the      
frequent fracture of the bolts which    
guide and  confine the rings2 but this  
is only a fault of detail which is      
easily  remedied1 and the principle     
appears to be superior to that of any of
 the  other metallic air pump valves at 
present in common use4    ,illustration3
 ,fig4 #da4 ,,trunk ,,air ,,pump4 ,scale
 #c_/d inch to #a foot4    #deg4        
,q4--,are not air pump valves now very  
generally made of india rubber8         
,a4--,they are almost invariably so made
 if the engines are travelling  fast1 as
 in the case of direct acting screw     
engines1 and they are very  often made  
of large discs or rings of india rubber1
 even when the engines  travel slowly4  

,a very usual and eligible arrangement  
for many purposes is  that shown in fig4
 #da1 where both foot and delivery      
valves are situated in  the ends of the 
pump1 and they1 as well as the valve in 
the bucket are made  of india rubber    
rings closing on a grating4 ,the trunk  
in the air pump  enables guide rods to  
be dispensed with4    ,illustration3    
,fig4 #db4 ,,penn',s ,,disk ,,valve     
,,for ,,air ,,pump4 ,section4           
,illustration3 ,fig4 #dc4 ,,penn',s     
,,disk ,,valve ,,for ,,air ,,pump4      
,ground ,plan4    ,illustration3 ,fig4  
#dd4 ,,maudslay',s ,,disc ,,valve ,,for 
,,air ,,pump4 ,section4    #deh4        
,q4--,the air pump1 when double acting1 
has of course inlet and outlet  valves  
at each end8    ,a4--,yes2 and the      
general arrangement of the valves of    
double acting air  pumps1 such as are   
usual in direct acting screw engines1 is
 that  represented in the figure of     
,penn's trunk engine already described  
in  ,chapter ,i4 ,each inlet and outlet 

valve consists of a number of india     
rubber  discs set over a perforated     
brass plate1 and each disc is bound down
 by a  bolt in the middle1 which bolt   
also secures a brass guard set above the
  disc to prevent it from rising too    
high4 ,the usual configuration of those 
valves is that represented in figs4 #db1
 #dc1 and #dd2 figs4 #db and #dc being a
  section and ground plan of the species
 of valve used by ,messrs4 ,penn1 and   
fig4 #dd being a section of that used by
 ,messrs4 ,maudslay4 ,it is important   
in these valves to have the india rubber
 thick1--say about an inch thick  for   
valves eight inches in diameter4 ,it is 
also advisable to make the  central     
bolts with a nut above and a nut below1 
and to form the bolt with a  counter    
sunk neck1 so that it will not fall down
 when the top nut is  removed4 ,the     
lower point of the bolt should be       
riveted over on the nut to  prevent it  
from unscrewing1 and the top end should 
have a split pin through  the point for 

the same purpose4 ,the hole through     
which the bolt passes  should be tapped1
 though the bolt is not screwed into it1
 so that if a bolt  breaks1 a temporary 
stud may be screwed into the hole       
without the necessity  of taking out the
 whole plate4 ,the guard should be      
large1 else the disc may  stretch in the
 central hole until it comes over it2   
but the guard should  not permit too    
much lift of the valve1 else a good deal
 of the water and  air will return into 
the pump at the return stroke before the
 valve shuts4  ,penn's guard is rather  
small1 and ,maudslay's permits too much 
lift4    #dei4 ,q4--,what is the proper 
area through the valve gratings8        
,a4--,the collective area should be at  
least equal to the area of the pump     
piston1 and the lower edges of the      
perforations should be rounded off to   
afford more free ingress or egress to   
the water4    #dfj4 ,q4--,is there much 
strain thrown on the plates in which the
 valves  are set8    ,a4--,a good deal  

of strain2 and in the earlier direct    
acting screw engines  these plates were 
nearly in every case made too light4    
,they should be made  thick1 have strong
 feathers upon them1 and be very        
securely bolted down  with split pins at
 the points of the bolts1 to prevent    
them from  unscrewing4 ,the plate will  
be very apt to be broken should some of 
the  bolts become loose4 ,of course all 
the bolts and split pins1 as well as the
  plates and guards1 must be of brass4  
#dfa4 ,q4--,how are the plates to be    
taken out should that become necessary8 
,a4--,they are usually taken out through
 a door in the top of the hot well      
provided for that purpose1 which door   
should be as large as the plates        
themselves2 and it is a good precaution 
to cast upon this door--which will  be  
of cast iron--six or eight stout        
projecting feet which will press upon   
the top of the outlet or delivery valve 
plate when the door is screwed  down4   
,the upper or delivery valve plate and  

the lower or foot valve plate  should   
have similar feet4 ,a large part of the 
strain will thus be  transferred from   
the plates to the door1 which can easily
 be made strong  enough to sustain it4  
,it is advisable that the plates should 
lie at an  angle so that the shock of   
the water may not come upon the whole   
surface at  once4    #dfb4 ,q4--,does   
the double acting air pump usual in     
direct acting screw  engines1 produce as
 good a vacuum as the single acting air 
pump usual in  paddle engines8          
,a4--,it will do so if properly         
constructed2 but ,i do not know of any  
case  of a double acting air pump1 with 
india rubber valves1 which has been     
properly constructed4    #dfc4          
,q4--,what is the fault of such pumps8  
,a4--,the pump frequently works by      
starts1 as if at times it did not draw  
at all1 and then again on a sudden      
gorged itself with water1 so as to throw
  a great strain upon the working parts4
 ,the vacuum1 moreover1 is by no means  

so good as it should be1 and it is a    
universal vice of direct acting screw   
engines that the vacuum is defective4 ,i
 have been at some pains to  investigate
 the causes of this imperfection2 and in
 a sugar house engine  fitted with pumps
 like those of a direct acting screw    
engine to maintain a  vacuum in the     
pans1 ,i found that a better vacuum was 
produced when the  engine was going     
slowly than when it was going fast2     
which is quite the  reverse of what was 
to have been expected1 as the hot water 
which had to be  removed by the         
condensation of the steam proceeding    
from the pan1 was a  constant quantity4 
,in this engine1 too1 which was a high  
pressure one1 the  irregularities of the
 engine consequent upon the fitful      
catching of the  water by the pump1 was 
more conspicuous1 as the working of this
 vacuum pump  was the only work that the
 engine had to perform4    #dfd4        
,q4--,and were you able to discover the 
cause of these irregularities8          

,a4--,the main cause of them ,i found to
 be the largeness of the space left     
between the valve plates in this class  
of pumps1 and out of which there is     
nothing to press the air or water which 
may be lying there4 ,it consequently    
happens1 that if there be the slightest 
leakage of air into the pump1 this  air 
is merely compressed1 and not expelled1 
by the advance of the air pump  piston4 
,it expands again to its former bulk on 
the return of the pump  piston1 and     
prevents the water from entering until  
there is such an  accumulation of       
pressure in the condenser as forces the 
water into the  pump1 when the air being
 expelled by the water1 causes a good   
vacuum to be  momentarily formed in the 
pump when it gorges itself by taking a  
sudden  gulp of water4 ,so soon1        
however1 as the pressure falls in the   
condenser and  some more air leaks into 
the pump1 the former imperfect action   
recurs and  is again redressed in the   
same violent manner4    #dfe4 ,q4--,is  

this irregular action of the pump the   
cause of the imperfect  vacuum8         
,a4--,it is one cause4 ,sometimes one   
end of the pump will alone draw and  the
 other end will be inoperative1 although
 it is equally open to the  condenser1  
and this will chiefly take place at the 
stuffing box end1 where  a leakage of   
air is more likely to occur4 ,i find1   
however1 that even when  both ends of   
the pump are acting equally and there is
 no leakage of air at  all1 the vacuum  
maintained by a double acting horizontal
 pump with india  rubber valves1 is not 
so good as that maintained by a single  
acting pump of  the kind usual in old   
engines4    #dff4 ,q4--,will you specify
 more precisely what were the results   
you  obtained8    ,a4--,when the vacuum 
pan was exhausted by the pumps without  
any boiling  being carried on in the    
pan1 but only a little cold water being 
let into  it1 and also into the pumps to
 enable them to act in their best       
manner1 it  was found that whereas with 

the old pump a vacuum of #aad on the    
sugar  boiler's gauge could be readily  
obtained1 equal to about #bi-a_/b inches
 of  mercury1 the lowest that could     
possibly be got with the new horizontal 
pump  was #abb degrees of the sugar     
boiler's gauge1 or #bi inches of        
mercury1 and  to get that the engine    
must not go faster than #aj or #ab      
strokes per minute4  ,the proper speed  
of the engine was #ge strokes per       
minute1 but if allowed to  go at that   
speed the vacuum fell to #acj of the    
sugar maker's gauge1 or  #bh-a_/b inches
 of mercury4 ,when the steam was let    
into the worms of the pan  so as to boil
 the water in it1 the vacuum was #acd at
 #ge revolutions of the  engine1 and    
went down to #acb at #dj revolutions1   
but rose again to #ace1  equal to about 
#bh-a_/d inches of mercury1 at #bj      
revolutions4    #dfg4 ,q4--,to what do  
you attribute the circumstance of a     
better vacuum  being got at low speeds  
than at high speeds8    ,a4--,it is     

difficult to assign the precise reason1 
but it appears to be a  consequence of  
the largeness of the vacant space       
between the valve plates4  ,when the    
piston of the air pump is drawn back1   
the air contained in this  large        
collection of water will cause it to    
boil up like soda water2 and  when the  
piston of the pump is forced forward1   
this air1 instead of being  expelled1   
will be again driven into the water4    
,there will consequently be a  quantity 
of air in the pump which cannot be got  
rid of at all1 and which  will impair   
the vacuum as a matter of course4       
#dfh4 ,q4--,what expedient did you adopt
 to improve the vacuum in the engine  to
 which you have referred8    ,a4--,i put
 blocks of wood on the air pump piston1 
which at the end of its  stroke         
projected between the valve plates and  
forced the water out4 ,i also           
introduced a cock of water at each end  
of the pump between the valve  plates1  
to insure the presence of water at each 

end of the pump to force  the air out4  
,with these ameliorations the pump      
worked steadily1 and the  vacuum        
obtained became as good as in the old   
pump4 ,i had previously  introduced an  
injection cock into each end of the air 
pump in steam  vessels1 from which ,i   
had obtained advantageous results2 and  
in all  horizontal air pumps ,i would   
recommend the piston and valve plates to
 be so  constructed that the whole of   
the water will be expressed by the      
piston4 ,i  would also recommend an     
injection cock to be introduced at each 
end of the  pump4          ,,pumps1     
,,cocks1 ,,and ,,pipes4    #dfi4        
,q4--,will you explain the arrangement  
of the feed pump8    ,a4--,in steam     
vessels1 the feed pump plunger is       
generally of brass1 and  the barrel of  
the pump is sometimes of brass1 but     
generally of cast iron4  ,there should  
be a considerable clearance between the 
bottom of the plunger  and the bottom of
 the barrel1 as otherwise the bottom of 

the barrel may be  knocked out1 should  
coal dust or any other foreign substance
 gain  admission1 as it probably would  
do if the injection water were drawn at 
any  time from the bilge of the vessel1 
as is usually done if the vessel springs
  a leak4 ,the valves of the feed pump  
in marine engines are generally of the  
spindle kind1 and are most conveniently 
arranged in a chest1 which may be       
attached in any accessible position to  
the side of the hot well4 ,there are    
two nozzles upon this chest1 of which   
the lower one leads to the pump1 and    
the upper one to the boiler4 ,the pipe  
leading to the pump is a suction pipe   
when the plunger ascends1 and a forcing 
pipe when the plunger descends4 ,the    
plunger in ascending draws the water out
 of the hot well through the lowest  of 
the valves1 and in descending forces it 
through the centre valve into  the space
 above it1 which communicates with the  
feed pipe4 ,should the feed  cock be    
shut so as to prevent any feed water    

from passing through it1 the  water will
 raise the topmost valve1 which is      
loaded to a pressure  considerably above
 the pressure of the steam1 and escape  
into the hot well4  ,this arrangement is
 neater and less expensive than that of 
having a  separate loaded valve on the  
feed pipe with an overflow through the  
ship's  side1 as is the more usual      
practice4    #dgj4 ,q4--,will you       
describe what precautions are to be     
observed in the  construction of the    
cocks used in engines8    ,a4--,all the 
cocks about an engine should be provided
 with bottoms and  stuffing boxes1 and  
reliance should never be placed upon a  
single bolt  passing through a bottom   
washer for keeping the plug in its      
place1 in the  case of any cock         
communicating with the boiler2 for a    
great strain is  thrown upon that bolt  
if the pressure of the steam be high1   
and if the plug  be made with much      
taper2 and should the bolt break1 or the
 threads strip1  the plug will fly out1 

and persons standing near may be scalded
 to death4  ,in large cocks1 it appears 
the preferable plan to cast the bottoms 
in2 and  the metal of which all the     
cocks about a marine engine are made1   
should be  of the same quality as that  
used in the composition of the brasses1 
and  should be without lead1 or other   
deteriorating material4 ,in some cases  
the  bottoms of cocks are burnt in with 
hard solder1 but this method cannot be  
depended upon1 as the solder is softened
 and wasted away by the hot salt  water1
 and in time the bottom leaks1 or is    
forced out4 ,the stuffing box of  cocks 
should be made of adequate depth1 and   
the gland should be secured by  means of
 four strong copper bolts4 ,the taper of
 blow-off cocks is an  important element
 in their construction2 as1 if the taper
 be too great1 the  plugs will have a   
continual tendency to rise1 which1 if   
the packing be  slack1 will enable grit 
to get between the faces1 while1 if the 
taper be  too little1 the plug will be  

liable to jam1 and a few times grinding 
will  sink it so far through the shell  
that the waterways will no longer       
correspond4 ,one eighth of an inch      
deviation from the perpendicular for    
every inch in height1 is a common angle 
for the side of the cock1 which         
corresponds with one quarter of an inch 
difference of diameter in an inch  of   
height2 but perhaps a somewhat greater  
taper than this1 or one third of  an    
inch difference in diameter for every   
inch of height1 is a preferable         
proportion4 ,the bottom of the plug must
 be always kept a small distance  above 
the bottom of the shell1 and an adequate
 surface must be left above  and below  
the waterway to prevent leakage4 ,cocks 
formed according to these  directions   
will be found to operate satisfactorily 
in practice1 while they  will occasion  
perpetual trouble if there be any       
malformation4    #dga4 ,q4--,what is the
 best arrangement and configuration of  
the blow-off  cocks8    ,a4--,the       

blow-off cocks of a boiler are generally
 placed some distance  from the boiler2 
but it appears preferable that they     
should be placed quite  close to it1 as 
there are no means of shutting off the  
water from the pipe  between the        
blow-off cock and the boiler1 should    
fracture or leakage there  arise4 ,every
 boiler must be furnished with a        
blow-off cock of its own1  independently
 of the main blow-off cocks on the      
ship's sides1 so that the  boilers may  
be blown off separately1 and may be shut
 off from one another4  ,the preferable 
arrangement appears to be1 to cast upon 
each blow-off cock a  bend for attaching
 the cock to the bottom of the boiler1  
and the plug  should stand about an inch
 in advance of the front of the boiler1 
so that  it may be removed1 or          
re-ground1 with facility4 ,the general  
arrangement of  the blow-off pipes is to
 run a main blow-off pipe beneath the   
floor plates1  across the ship1 at the  
end of the engines1 and into this pipe  

to lead a  separate pipe1 furnished with
 a cock1 from each boiler4 ,the main    
blow-off  pipe1 where it penetrates the 
ship's side1 is furnished with a cock3  
and in  modern steam vessels ,kingston's
 valves are also used1 which consist of 
a  spindle or plate valve1 fitted to the
 exterior of the ship1 so that if the   
internal pipe or cock breaks1 the       
external valve will still be operative4 
,some expedient of this kind is almost  
necessary1 as the blow-off cocks        
require occasional regrinding1 and the  
sea cocks cannot be re-ground  without  
putting the vessel into dock1 except by 
the use of ,kingston's  valves1 or some 
equivalent expedient4    #dgb4          
,q4--,what is the proper construction   
and situation of the injection  cocks1  
and waste water valves8    ,a4--,the sea
 injection cocks are usually made in the
 same fashion as the sea  blow-off      
cocks1 and of about the same size1 or   
rather larger4 ,the injection  water is 
generally admitted to the condenser by  

means of a slide valve1 but  a cock     
appears to be preferable1 as it is more 
easily opened1 and has not  any         
disposition to shut of its own accord4  
,in paddle vessels the sea  injection   
pipes should be put through the ship's  
sides in advance of the  paddles1 so    
that the water drawn in may not be      
injuriously charged with  air4 ,the     
waste water pipe passing from the hot   
well through the vessel's  side is      
provided with a stop valve1 called the  
discharge valve1 which is  usually made 
of the spindle kind1 so as to open when 
the water coming from  the air pump     
presses against it4 ,in some cases this 
valve is a sluice  valve1 but the hot   
well is then almost sure to be split1 if
 the engine be  set on without the valve
 having been opened4 ,the opening of the
 waste water  pipe should always be     
above the load water line1 as it will   
otherwise be  difficult to prevent      
leakage through the engine into the ship
 when the  vessel is lying in harbor4   

#dgc4 ,q4--,what is the best arrangement
 of gauge cocks and glass gauges8       
,a4--,gauge cocks are generally very    
inartificially made1 and occasion       
needless annoyance4 ,they are rarely    
made with bottoms1 or with stuffing     
boxes1 and are consequently1 for the    
most part1 adorned with stalactites of  
salt after a short period of service4   
,the water discharged from them1 too1   
from the want of a proper conduit1      
disfigures the front of the boiler1 and 
adds to the corrosion in the ash pits4  
,it would be preferable to combine  the 
gauge cocks appertaining to each boiler 
into a single upright tube1  connected  
suitably with the boiler1 and the water 
flowing from them could  be directed    
downward into a funnel tube             
communicating with the bilge4 ,the      
cocks of the glass tubes1 as well as of 
the gauge cocks1 should be  furnished   
with stuffing boxes and with bottoms1   
unless the water enters  through the    
bottom of the plug1 which in gauge cocks

 is sometimes the case4  ,the glass     
gauge tubes should always be fitted with
 a cock at each neck  communicating with
 the boiler1 so that the water and steam
 may be shut off  if the tube breaks2   
and the cocks should be so made as to   
admit of the  tubes being blown through 
with steam to clear them1 as in muddy   
water they  will become so soiled that  
the water cannot be seen4 ,the gauge    
cocks  frequently have pipes running up 
within the boiler1 to the end that a    
high  water level may be made consistent
 with an easily accessible position of  
the gauge cocks themselves4 ,with the   
glass tubes1 however1 this species of   
arrangement is not possible1 and the    
glass tubes must always be placed in    
the position of the water level4        
#dgd4 ,q4--,what is the proper material 
of the pipes in steam vessels8          
,a4--,most of the pipes of marine       
engines should be made of copper4 ,the  
steam  pipes may be of cast iron1 if    
made very strong1 but the waste water   

pipes  should be of copper4 ,cast iron  
blow-off pipes have in some cases been  
employed1 but they are liable to        
fracture1 and are dangerous4 ,the       
blow-off  and feed pipes should be of   
copper1 but the waste steam pipe may be 
of  galvanized iron4 ,every pipe passing
 through the ship's side1 and every pipe
  fixed at both ends1 and liable to be  
heated and cooled1 should be furnished  
with a faucet or expansive joint2 and in
 the case of the cast iron pipes1  the  
part of the pipe fitting into the faucet
 should be turned4 ,in the  distribution
 of the faucets of the pipes exposed to 
pressure1 care must be  taken that they 
be so placed that the parts of the pipe 
cannot be forced  asunder1 or turned    
round by the strain1 as serious         
accidents have occurred  from the       
neglect of this precaution4    #dge4    
,q4--,what is the best mode of making   
pipes tight where they penetrate  the   
ship's side8    ,a4--,in wooden vessels 
the pipes where they pierce the ship's  

side1 should  be made tight1 as         
follows3--the hole being cut1 a short   
piece of lead pipe1  with a broad flange
 at one end1 should be fitted into it1  
the place having  been previously       
smeared with white lead1 and the pipe   
should then be beaten  on the inside1   
until it comes into close contact all   
around with the wood4  ,a loose flange  
should next be slipped over the         
projecting end of the lead  pipe1 to    
which it should be soldered1 and the    
flanges should both be nailed  to the   
timber with scupper nails1 white lead   
having been previously spread           
underneath4 ,this method of procedure1  
it is clear1 prevents the possibility   
of leakage down through the timbers2 and
 all1 therefore1 that has to be  guarded
 against after this precaution1 is to   
prevent leakage into the ship4  ,to     
accomplish this object1 let the pipe    
which it is desired to attach be  put   
through the leaden hause1 and let the   
space between the pipe and the  lead be 

packed with gasket and white lead1 to   
which a little olive oil has  been      
added4 ,the pipe must have a flange upon
 it to close the hole in the  ship's    
side2 the packing must then be driven in
 from the outside1 and be  kept in by   
means of a gland secured with bolts     
passing through the ship's  side4 ,if   
the pipe is below the water line the    
gland must be of brass1 but  for the    
waste water pipe a cast iron gland will 
answer4 ,this method of  securing pipes 
penetrating the side1 however1 though   
the best for wooden  vessels1 will1 it  
is clear1 fail to apply to iron ones4   
,in the case of iron  vessels1 it       
appears to be the best practice to      
attach a short iron nozzle1  projecting 
inward from the skin1 for the attachment
 of every pipe below the  water line1 as
 the copper or brass would waste the    
iron of the skin if the  attachment were
 made in the usual way4        ,,details
 ,,of ,,the ,,screw ,,and ,,screw       
,,shaft4    #dgf4 ,q4--,what is the best

 method of fixing the screw upon the    
shaft8    ,a4--,the best way is to cut  
two large grooves in the shaft coming up
 to a  square end1 and two corresponding
 grooves or key seats in the screw boss 
opposite the arms4 ,fit into the grooves
 on the shaft keys with heads1 the      
length of which is equal to half the    
depth of the boss1 and with the ends  of
 the keys bearing against the ends of   
the grooves in the shaft4 ,then ship  on
 the propeller1 and drive other keys of 
an equal length from the other  side of 
the boss1 so that the points of the keys
 will nearly meet in the  middle2 next  
burr up the edge of the grooves upon the
 heads of the keys1 to  prevent them    
from working back2 and finally tap a    
bolt into the side of the  boss to      
penetrate the shaft4 ,propellers so     
fitted will never get slack4    #dgg4   
,q4--,what is the best way of fitting in
 the screw pipe at the stern8           
,a4--,it should have projecting rings1  
which should be turned2 and cast  iron  

pieces with holes in them1 bored out to 
the sizes of these rings1  should be    
secured to the stern frames1 and the    
pipe be then shipped through  all4      
,before this is done1 however1 the stern
 post must be bored out by a  template  
to fit the pipe1 and the pipe is to be  
secured at the end to the  stern post   
either by a great external nut of cast  
iron1 or by bolts passing  through the  
stern post and through lugs on the pipe4
 ,the pipe should be  bored throughout  
its entire length1 and the shaft should 
be turned so as to  afford a very long  
bearing which will prevent rapid wear4  
#dgh4 ,q4--,how is the hole formed in   
the deadwood of the ship in which the   
screw works8    ,a4--,a great frame of  
malleable iron1 the size of the hole1 is
 first set  up1 and the plating of the  
ship is brought to the edge of this     
hole1 and is  riveted through the frame4
 ,it is important to secure this frame  
very firmly  to the rest of the ship1   
with which view it is advisable to form 

a great  palm1 like the palm of a vice1 
on its inner superior corner1 which1    
projecting into the ship1 may be secured
 by breast-hook plates to the  sides1   
whereby the strain which the screw      
causes will be distributed over  the    
stern1 instead of being concentrated on 
the rivets of the frame4    #dgi4       
,q4--,are there several lengths of screw
 shaft8    ,a4--,there are4    #dhj4    
,q4--,how then are these secured to one 
another8    ,a4--,the best mode of      
securing the several lengths of shaft   
together is by  forging the shafts with 
flanges at the ends1 which are connected
 together  by bolts1 say six strong     
bolts in each1 accurately fitted to the 
holes4    ,illustration3 ,fig #dd4 ,end 
of the ,screw ,shaft of ,correo1 showing
 the mode  of receiving the ,thrust4 ,a1
 discs2 ,b1 tightening wedge4    #dha4  
,q4--,how is the thrust of the shaft    
usually received8    ,a4--,in some cases
 it is received on a number of metal    
discs set in a box  containing oil2 and 

should one of these discs stick fast    
from friction1 the  others will be free 
to revolve4 ,this arrangement1 which is 
represented in  fig4 #dd1 is used pretty
 extensively and answers the purpose    
perfectly4 ,it  is of course necessary  
that the box in which the discs ,a are  
set1 shall be  strong enough to         
withstand the thrust which the screw    
occasions4 ,another  arrangement still  
more generally used1 is that represented
 in figs4 #ee and  #ef1 p4 #cca4 ,it is 
a good practice to make the thrust      
plummer block with a  very long sole in 
the direction of the shaft1 so as to    
obviate any risk of  canting or         
springing forward when the strain is    
applied1 as such a  circumstance1 if    
occurring even to a slight extent1 would
 be very likely to  cause the bearing to
 heat4    #dhb4 ,q4--,are there not     
arrangements existing in some vessels   
for enabling  the screw to be lifted out
 of the water while the vessel is at    
sea8    ,a4--,there are2 but such       

arrangements are not usual in merchant  
vessels4  ,in one form of apparatus the 
screw is set on a short shaft in the    
middle of  a sliding frame1 which can be
 raised or lowered in grooves like a    
window  and the screw shaft within the  
ship can be protruded or withdrawn by   
appropriate mechanism1 so as to engage  
or leave free this short shaft as  may  
be required4 ,when the screw has to be  
lifted1 the screw shaft is drawn  into  
the vessel1 leaving the short shaft free
 to be raised up by the  sliding frame1 
and the frame is raised by long screws  
turned round by a  winch purchase on    
deck4 ,a chain or rope1 however1 is     
better for the purpose  of raising this 
frame1 than long screws2 but the frame  
should in such case  be provided with   
pall catches like those of a windlass1  
which1 if the rope  should break1 will  
prevent the screw from falling4         
,,details ,,of ,,the ,,paddles ,,and    
,,paddle ,,shaft4    #dhc4 ,q4--,what   
are the most important details of the   

construction of  paddle wheels8         
,a4--,the structure of the feathering   
wheel will be hereafter described in    
connection with an account of the       
oscillating engine2 and it will be      
expedient now to restrict any account of
 the details to the common radial       
paddle1 as applied to ocean steamers4   
,the best plan of making the paddle     
centres is with square eyes1 and each   
centre should be secured in its place   
by means of eight thick keys4 ,the shaft
 should be burred up against the  head  
of these keys with a chisel1 so as to   
prevent the keys from coming  back of   
their own accord4 ,if the keys are      
wanted to be driven back1 this  burr    
must be cut off1 and if made thick1 and 
of the right taper1 they may  then be   
started without difficulty4 ,the shaft  
must of course be forged with  square   
projections on it1 so as to be suitable 
for the application of  centres with    
square eyes4 ,messrs4 ,maudslay  ,co4   
bore out their paddle  centres1 and turn

 a seat for them on the shaft1 afterward
 fixing them on  the shaft with a single
 key4 ,this plan is objectionable for   
the two  reasons1 that it is insecure   
when new1 and when old is irremovable4  
,the  general practice among the ,london
 engineers is to fix the paddle arms at 
the centre to a plate by means of bolts1
 a projection being placed upon the     
plates on each side of the arm1 to      
prevent lateral motion2 but this method 
is inferior in durability to that       
adopted in the ,clyde1 in which each arm
  is fitted into a socket by means of a 
cutter--a small hole being left         
opposite to the end of each arm1 whereby
 the arm may be forced back by a  drift4
    #dhd4 ,q4--,how are the arms        
attached to the outside rings8          
,a4--,some engineers join the paddle    
arms to the outer ring by means of      
bolts2 but unless very carefully fitted1
 those bolts after a time become  slack 
sideways1 and a constant working of the 
parts of the wheel goes on in           

consequence4 ,sometimes the part of the 
other ring opposite the arm is  formed  
into a mortise1 and the arms are wedged 
tight in these holes by  wedges driven  
in on each side2 but the plan is an     
expensive one1 and not  satisfactory1 as
 the wedges work loose even though      
riveted over at the  point4 ,the best   
mode of making a secure attachment of   
the arms to the ring1  consists in      
making the arms with long ,t heads1 and 
riveting the cross piece  to the outer  
ring with a number of rivets1 not of the
 largest size1 which  would weaken the  
outer ring too much4 ,the best way of   
securing the inner  rings to the arms is
 by means of lugs welded on the arms1   
and to which the  rings are riveted4    
#dhe4 ,q4--,what are the scantlings of  
the paddle floats8    ,a4--,the paddle  
floats are usually made either of elm or
 pine2 if of the  former1 the common    
thickness for large sea-going vessels is
 about #b-a_/b  inches2 if of the       
latter1 #c inches4 ,the floats should   

have plates on both  sides1 else the    
paddle arms will be very liable to cut  
into the wood1 and  the iron of the arms
 will be very rapidly wasted4 ,when the 
floats have been  fresh put on they must
 be screwed up several times before they
 come to a  bearing4 ,if this be not    
done1 the bolts will be sure to get     
slack at sea1  and all the floats on the
 weather side may be washed off4 ,the   
bolts for  holding on the paddle floats 
are made extra strong1 on account of the
  corrosion to which they are subject2  
and the nuts should be made large1 and  
should be square1 so that they may be   
effectually tightened up1 even though   
their corners be worn away by corrosion4
 ,it is a good plan to give the  thread 
of the paddle bolts a nick with a       
chisel1 after the nut has been  screwed 
up1 which will prevent the nut from     
turning back4 ,paddle floats1  when     
consisting of more than one board1      
should be bolted together edgeways1  by 
means of bolts running through their    

whole breadth4 ,the floats should  not  
be notched to allow of their projection 
beyond the outer ring1 as1 if  the sides
 of the notch be in contact with the    
outer ring1 the ring is soon  eaten away
 in that part1 and the projecting part  
of the float1 being  unsupported1 is    
liable to be broken off4    #dhf4       
,q4--,do not the wheels jolt sideways   
when the vessel rolls8    ,a4--,it is   
usual to put a steel plate at each end  
of the paddle shafts  tightened with a  
key1 to prevent end play when the vessel
 rolls1 but the  arrangement is         
precarious and insufficient4 ,messrs4   
,maudslay make their  paddle shaft      
bearings with very large fillets in the 
corner1 with the view  of diminishing   
the evil2 but it would be preferable to 
make the bearings of  the crank shafts  
spheroidal2 and1 indeed1 it would       
probably be an  improvement if most of  
the bearings about the engine were to be
 made in the  same fashion4 ,the loose  
end of the crank pin should be made not 

spheroidal1  but consisting of a portion
 of a sphere2 and a brass bush might    
then be  fitted into the crank eye1 that
 would completely encase the ball of the
  pin1 and yet permit the outer end of  
the paddle shaft to fall without        
straining the pin1 the bush being at the
 same time susceptible of a slight  end 
motion4 ,the paddle shaft1 where it     
passes through the vessel's side1 is    
usually surrounded by a lead stuffing   
box1 which will yield if the end of  the
 shaft falls2 this stuffing box prevents
 leakage into the ship from the  paddle 
wheels3 but it is expedient1 as a       
further precaution1 to have a  small    
tank on the ship's side immediately     
beneath the stuffing box1 with a  pipe  
leading down to the bilge to catch and  
conduct away any water that may  enter  
around the shaft4    #dhg4 ,q4--,how is 
the outer bearing of the paddle wheels  
supplied with  tallow8    ,a4--,the     
bearing at the outer end of the paddle  
shaft is sometimes  supplied with       

tallow1 forced into a hole in the       
plummer block cover1 as in  the case of 
water wheels2 but for vessels intended  
to perform long voyages1  it is         
preferable to have a pipe leading down  
to the oil cup above the  journal from  
the top of the paddle box1 through which
 pipe oil may at any  time be supplied4 
#dhh4 ,q4--,will you explain the method 
of putting engines into a steam  vessel8
    ,a4--,as an illustration of this    
operation it may be advisable to take   
the  case of a side lever engine1 and   
the method of proceeding is as          
follows3--  ,first measure across from  
the inside of paddle bearers to the     
centre of the  ship1 to make sure that  
the central line1 running in a fore and 
aft  direction on the deck or beams1    
usually drawn by the carpenter1 is      
really  in the centre4 ,stretch a line  
across between the paddle bearers in the
  direction of the shaft2 to this line1 
in the centre of the ship where the     
fore and aft mark has been made1 apply a

 square with arms six or eight feet     
long1 and bring a line stretched        
perpendicularly from the deck to the    
keelson1 accurately to the edge of the  
square3 the lower point of the line     
where it touches the keelson will be    
immediately beneath the marks made  upon
 the deck4 ,if this point does not come 
in the centre of the keelson1 it  will  
be better to shift it a little1 so as to
 bring it to the centre1  altering the  
mark upon the deck correspondingly1     
provided either paddle  shaft will admit
 of this being done--one of the paddle  
brackets being  packed behind with wood1
 to give it an additional projection    
from the side  of the paddle bearer4    
,continue the line fore and aft upon the
 keelson as  nearly as can be judged in 
the centre of the ship2 stretch another 
line  fore and aft through the mark upon
 the deck1 and look it out of winding   
with the line upon the keelson4 ,fix    
upon any two points equally distant     
from the centre1 in the line stretched  

transversely in the direction of the    
shaft2 and from those points1 as        
centres1 and with any convenient radius1
  sweep across the fore and aft line to 
see that the two are at right angles2   
and1 if not1 shift the transverse line a
 little to make them so4 ,from the      
transverse line next let fall a line    
upon each outside keelson1 bringing  the
 edge of the square to the line1 the    
other edge resting on the keelson4  ,a  
point will thus be got on each outside  
keelson1 perpendicularly beneath  the   
transverse line running in the direction
 of the shaft1 and a line drawn  between
 those two points will be directly below
 the shaft4 ,to this line the  line of  
the shaft marked on the sole plate has  
to be brought1 care being  taken1 at the
 same time1 that the right distance is  
preserved between the  fore and aft line
 upon the sole plate1 and the fore and  
aft line upon the  central keelson4     
#dhi4 ,q4--,of course the keelsons have 
first to be properly prepared8          

,a4--,in a wooden vessel1 before any    
part of the machinery is put in1 the    
keelsons should be dubbed fair and      
straight1 and be looked out of winding  
by means of two straight edges4 ,the art
 of placing engines in a ship is  more a
 piece of plain common sense than any   
other feat in engineering1 and  every   
man of intelligence may easily settle a 
method of procedure for  himself4 ,plumb
 lines and spirit levels1 it is obvious1
 cannot be employed  on board a vessel1 
and the problem consists in so placing  
the sole plates1  without these aids1   
that the paddle shaft will not stand    
awry across the  vessel1 nor be carried 
forward beyond its place by the framing 
shouldering  up more than was expected4 
,as a plumb line cannot be used1        
recourse must be  had to a square2 and  
it will signify nothing at what angle   
with the deck  the keelsons run1 so long
 as the line of the shaft across the    
keelsons is  square down from the shaft 
centre4 ,the sole plates being fixed1   

there is no  difficulty in setting the  
other parts of the engine in their      
proper places  upon them4 ,the paddle   
wheels must be hung from the top of the 
paddle box to  enable the shaft to be   
rove through them1 and the cross stays  
between the  engines should be fixed in 
when the vessel is afloat4 ,to try      
whether the  shafts are in a line1 turn 
the paddle wheels1 and try if the       
distance  between the cranks is the same
 at the upper and under1 and the two    
horizontal centres2 if not1 move the end
 of the paddle shaft up or down1        
backward or forward1 until the distance 
between the cranks at all the four      
centres is the same4    #dij4 ,q4--,in  
what manner are the engines of a steam  
vessel secured to the  hull8            
,a4--,the engines of a steamer are      
secured to the hull by means of bolts   
called holding down bolts1 and in wooden
 vessels a good deal of trouble is      
caused by these bolts1 which are        
generally made of iron4 ,sometimes they 

go  through the bottom of the ship1 and 
at other times they merely go through   
the keelson1--a recess being made in the
 floor or timbers to admit of the       
introduction of a nut4 ,the iron1       
however1 wears rapidly away in both     
cases1  even though the bolts are       
tinned2 and it has been found the       
preferable  method to make such of the  
bolts as pass through the bottom1 or    
enter the  bilge1 of ,muntz's metal1 or 
of copper4 ,in a side lever engine1 four
 ,muntz's  metal bolts may be put       
through the bottom at the crank end of  
the framing  of each engine1 four more  
at the main centre1 and four more at the
  cylinder1 making twelve through bolts 
to each engine2 and it is more          
convenient to make these bolts with a   
nut at each end1 as in that case the    
bolts may be dropped down from the      
inside1 and the necessity is obviated of
  putting the vessel on very high blocks
 in the dock1 in order to give room  to 
put the bolts up from the bottom4 ,the  

remainder of the holding down  bolts may
 be of iron1 and may1 by means of a     
square neck1 be screwed into  the timber
 of the keelsons as wood screws--the    
upper part being furnished  with a nut  
which may be screwed down upon the sole 
plate1 so soon as the  wood screw       
portion is in its place4 ,if the        
cylinder be a fixed one it  should be   
bolted down to the sole plate by as many
 bolts as are employed to  attach the   
cylinder cover1 and they should be of   
copper or brass1 in any  situation that 
is not easily accessible4    #dia4      
,q4--,if the engines become loose1 how  
do you refix them8    ,a4--,it is       
difficult to fix engines effectually    
which have once begun to  work in the   
ship1 for in time the surface of the    
keelsons on which the  engines bear     
becomes worn uneven1 and the engines    
necessarily rock upon it4  ,as a general
 rule1 the bolts attaching the engines  
to the keelsons are too  few and of too 
large a diameter3 it would be preferable

 to have smaller  bolts1 and a greater  
number of them4 ,in addition to the     
bolts going through  the keelsons or the
 vessel's bottom1 there should be a     
large number of wood  screws securing   
the sole plate to the keelson1 and a    
large number of bolts  securing the     
various parts of the engine to the sole 
plate4 ,in iron  vessels1 holding down  
bolts passing through the bottom are not
 expedient2  and there the engine has   
merely to be secured to the iron plate  
of the  keelsons1 which are made hollow 
to admit of a more effectual attachment4
    #dib4 ,q4--,what are the proper     
proportions of bolts8    ,a4--,in well  
formed bolts1 the spiral groove         
penetrates about one twelfth  of the    
diameter of the cylinder round which it 
winds1 so that the diameter  of the     
solid cylinder which remains is five    
sixths of the diameter over the  thread4
 ,if the strain to which iron may be    
safely subjected in machinery is  one   
fifteenth of its utmost strength1 or    

#d1jjj lbs4 on the square inch1  then   
#b1ahj lbs4 may be sustained by a screw 
an inch in diameter1 at the  outside of 
the threads4 ,the strength of the       
holding down bolts may easily  be       
computed1 when the elevating force of   
the piston or main centre is  known2 but
 it is expedient very much to exceed    
this strength in practice1  on account  
of the elasticity of the keelsons1 the  
liability to corrosion1  and other      
causes4          ,,the ,,locomotive     
,,engine4    #dic4 ,q4--,what is the    
amount of tractive force requisite to   
draw carriages  on railways8            
,a4--,upon well formed railways with    
carriages of good construction1 the     
average tractive force required for low 
speeds is about #g-a_/b lbs4 per ton1   
or #a_/cjjth of the load1 though in some
 experimental cases1 where particular   
care was taken to obtain a favorable    
result1 the tractive force has been     
reduced as low as #a_/ejjth of the load4
 ,at low speeds the whole of the        

tractive force is expended in overcoming
 the friction1 which is made up  partly 
of the friction of attrition in the     
axles1 and partly of the rolling        
friction1 or the obstruction to the     
rolling of the wheels upon the rail4    
,the rolling friction is very small when
 the surfaces are smooth1 and in the    
case of railway carriages does not      
exceed #a_/ajjjth4 of the load2 whereas 
the draught on common roads of good     
construction1 which is chiefly made up  
of the rolling friction1 is as much as  
#a_/cfth of the load4    #did4,q4--,in  
reference to friction you have already  
stated that the  friction of iron       
sliding upon brass1 which has been oiled
 and then wiped  dry1 so that no film of
 oil is interposed1 is about #a_/aath of
 the pressure1  but that in machines in 
actual operation1 where there is a film 
of oil  between the rubbing surfaces1   
the friction is only about one third of 
this  amount1 or #a_/cc;d of the weight4
  ,how then can the tractive resistance 

of  locomotives at low speeds1 which you
 say is entirely made up of friction1   
be so little as #a_/ejjth4 of the       
weight8    ,a4--,i did not state that   
the resistance to traction was #a_/ejjth
 of the  weight upon an average--to     
which condition the answer given to a   
previous  question must be understood to
 apply--but ,i stated that the average  
traction was about #a_/cjjth of the     
load1 which nearly agrees with my former
  statement4 ,if the total friction be  
#a_/cjjth of the load1 and the rolling  
friction be #a_/ajjjth of the load1 then
 the friction of attrition must be      
#a_/dbith of the load2 and if the       
diameter of the wheels be #cf in41 and  
the  diameter of the axles be #c in41   
which are common proportions1 the       
friction  of attrition must be increased
 in the proportion of #cf to #c1 or #ab 
times1  to represent the friction of the
 rubbing surface when moving with the   
velocity of the carriage1 #ab_/dbiths   
are about #a_/ceth of the load1 which   

does not differ much from the proportion
 of #a_/cc;d as previously determined4  
#die4 ,q4--,what is the amount of       
adhesion of the wheels upon the rails8  
,a4--,the adhesion of the wheels upon   
the rails is about #a_/eth of the       
weight when the rails are clean1 or     
either perfectly wet or perfectly dry2  
but when the rails are half wet or      
greasy1 the adhesion is not more than   
#a_/ajth or #a_/abth of the weight or   
pressure upon the wheels4 ,the weight of
 a  locomotive of modern construction   
varies from #bj to #be tons4    #dif4   
,q4--,and what is its cost and average  
performance8    ,a4--,the cost of a     
common narrow gauge locomotive1 of      
average power1  varies from #a1ijj to   
#b1bjj2 it will run on an average #acj  
miles per day1  at a cost for repairs of
 #b-a_/b;d4 per mile2 and the cost of   
locomotive  power1 including repairs1   
wages1 oil1 and coke1 does not much     
exceed #f;d4  per mile run1 on          
economically managed railways4 ,this    

does not include a  sinking fund for the
 renewal of the engines when worn out1  
which may be  taken as equivalent to #aj
 per cent4 on their original cost4      
#dig4 ,q4--,does the expense of traction
 increase much with an increased  speed8
    ,a4--,yes2 it increases very        
rapidly1 partly from the undulation of  
the  earth when a heavy train passes    
over it at a high velocity1 but chiefly 
from the resistance of the atmosphere   
and blast pipe1 which constitute the    
greatest of the impediments to motion at
 high speeds4 ,at a speed of #cj  miles 
an hour1 the atmospheric resistance has 
been found in some cases to  amount to  
about #ab lbs4 a ton2 and in side winds 
the resistance even  exceeds this       
amount1 partly in consequence of the    
additional friction  caused from the    
flanges of the wheels being forced      
against the rails1 and  partly because  
the wind catches to a certain extent the
 front of every  carriage1 whereby the  
efficient breadth of each carriage1 in  

giving motion  to the air in the        
direction of the train1 is very much    
increased4 ,at a  speed of #cj miles an 
hour1 an engine evaporating #bjj cubic  
feet of water in  the hour1 and         
therefore exerting about #bjj horses    
power1 will draw a load  of #aaj tons4  
,taking the friction of the train at    
#g-a_/b lbs4 per ton1 or #hbe  lbs4     
operating at the circumference of the   
driving wheel--which1 with #e ft4  #f   
in4 wheels1 and #ah in4 stroke1 is      
equivalent to #d1geg lbs4 upon the      
piston--and taking the resistance of the
 blast pipe at #f lbs4 per square  inch 
of the pistons1 and the friction of the 
engine unloaded at #a lb4 per  square   
inch1 which1 with pistons #ab in4 in    
diameter1 amount together to  #a1ehb    
lbs41 and reckoning the increased       
friction of the engine due to the  load 
at #a_/gth of the load1 as in some cases
 it has been found  experimentally to   
be1 though a much less proportion than  
this would  probably be a nearer        

average1 we have #gjah4d lbs4 for the   
total load upon  the pistons4 ,at #cj   
miles an hour the speed of the pistons  
will be #deg4h  feet per minute1 and    
#gjah4d lbs4 multiplied by #deg4h ft4   
per minute1 are  equal to #cbacjbc4e    
lbs4 raised one foot high in the minute1
 which1 divided  by #cc1jjj1 gives #ig4c
 horses power as the power which would  
draw #aaj tons  upon a railway at a     
speed of #cj miles an hour1 if there    
were no atmospheric  resistance4 ,the   
atmospheric resistance is at the rate of
 #ab lbs4 a ton1  with a load of #aaj   
tons1 equal to #a1cbj lbs41 moving at a 
speed of #cj miles  an hour1 which1 when
 reduced1 becomes #aje4h horses power1  
and this1 added  to #ig4c1 makes #bjc4a1
 instead of #bjj horses power1 as       
ascertained by a  reference to the      
evaporative power of the boiler4 ,this  
amount of  atmospheric resistance1      
however1 exceeds the average1 and in    
some of the  experiments for            
ascertaining the atmospheric resistance1

 a part of the  resistance due to the   
curves and irregularities of the line   
has been  counted as part of the        
atmospheric resistance4    #dih4        
,q4--,is the resistance per ton of the  
engine the same as the  resistance per  
ton of the train8    ,a4--,no2 it is    
more1 since the engine has not merely   
the resistance of the  atmosphere and of
 the wheels to encounter1 but the       
resistance of the  machinery besides4   
,according to ,mr4 ,gooch's experiments 
upon a train  weighing #ajj tons1 the   
resistance of the engine and tender at  
#ac4a miles  per hour was found by the  
indicator to be #ab4ch lbs42 the        
resistance per  ton of the train1 as    
ascertained by the dynamometer1 was at  
the same speed  #g4eh lbs41 and the     
average resistance of locomotive and    
train was #i4jd lbs4  ,at #bj4b miles   
per hour these resistances respectively 
became #ai4j1 #h4ai1  and #ab4b lbs4 ,at
 #dda miles per hour the resistances    
became #cd4j1 #ba4aj1 and  #be4e lbs41  

and at #eg4d miles an hour they became  
#ce4e1 #ag4ha1 and #bc4h lbs4    #dii4  
,q4--,is it not maintained that the     
resistance of the atmosphere to  the    
progress of railway trains increases as 
the square of the velocity8    ,a4--,the
 atmospheric resistance1 no doubt1      
increases as the square of the          
velocity1 and the power1 therefore1     
necessary to overcome it will increase  
as the cube of the velocity1 since in   
doubling the speed four times1 the      
power must be expended in overcoming the
 atmospheric resistance in half the     
time4 ,at low speeds1 the resistance    
does not increase very rapidly2 but at  
high speeds1 as the rapid increase in   
the atmospheric resistance causes the   
main resistance to be that arising from 
the atmosphere1 the total  resistance   
will vary nearly as the square of the   
velocity4 ,thus the  resistance of a    
train1 including locomotive and tender1 
will1 at #ae miles  an hour1 be about   
#i4c lbs4 per ton2 at #cj miles an hour 

it will be #ac4b  lbs4 per ton2 and at  
#fj miles an hour1 #bi lbs4 per ton4 ,if
 we suppose the  same law of progression
 to continue up to #abj miles an hour1  
the resistance  at that speed will be   
#ib4b lbs4 per ton1 and at #bdj miles an
 hour the  resistance will be #cdd4h    
lbs4 per ton4 ,thus1 in doubling the    
speed from #fj  to #abj miles per hour1 
the resistance does not fall much short 
of being  increased fourfold1 and the   
same remark applies to the increase of  
the  speed from #abj to #bdj miles an   
hour4 ,these deductions and other       
deductions  from ,mr4 ,gooch's          
experiments on the resistance of railway
 trains1 are fully  discussed by ,mr4   
,clark1 in his ,treatise on railway     
machinery1 who gives the  following rule
 for ascertaining the resistance of a   
train1 supposing the  line to be in good
 order1 and free from curves3--,to find 
the total  resistance of the engine1    
tender1 and train in pounds per ton1 at 
any given  speed4 ,square the speed in  

miles per hour2 divide it by #aga1 and  
add #h to  the quotient4 ,the result is 
the total resistance at the rails in    
lbs4 per  ton4    #ejj4,q4--,how comes  
it1 that the resistance of fluids       
increases as the  square of the         
velocity1 instead of the velocity       
simply8    ,a4--,because the height     
necessary to generate the velocity with 
which the  moving object strikes the    
fluid1 or the fluid strikes the object1 
increases  as the square of the         
velocity1 and the resistance or the     
weight of a  column of any fluid varies 
as the height4 ,a falling body1 as has  
been  already explained1 to have        
acquired twice the velocity1 must have  
fallen  through four times the height2  
the velocity generated by a column of   
any  fluid is equal to that acquired by 
a body falling through the height of the
  column2 and it is therefore clear1    
that the pressure due to any given      
velocity must be as the square of that  
velocity1 the pressure being in  every  

case as twice the altitude of the       
column4 ,the work done1 however1 by  a  
stream of air or other fluid in a given 
time1 will vary as the cube of  the     
velocity2 for if the velocity of a      
stream of air be doubled1 there will    
not only be four times the pressure     
exerted per square foot1 but twice the  
quantity of air will be employed2 and in
 windmills1 accordingly1 it is  found1  
that the work done varies nearly as the 
cube of the velocity of the  wind4 ,if1 
however1 the work done by a given       
quantity of air moving at  different    
speeds be considered1 it will vary as   
the squares of the speeds4    #eja4     
,q4--,but in a case where there is no   
work done1 and the resistance  varies as
 the square of the speed1 should not the
 power requisite to  overcome that      
resistance vary as the square of the    
speed8    ,a4--,it should if you        
consider the resistance over a given    
distance1 and  not the resistance during
 a given time4 ,supposing the resistance

 of a  railway train to increase as the 
square of the speed1 it would take four 
times the power1 so far as atmospheric  
resistance is concerned1 to  accomplish 
a mile at the rate of #fj miles an hour1
 that it would take to  accomplish a    
mile at #cj miles an hour2 but in the   
former case there would  be twice the   
number of miles accomplished in the same
 time1 so that when  the velocity of the
 train was doubled1 we should require an
 engine that was  capable of overcoming 
four times the resistance at twice the  
speed1 or in  other words1 that was     
capable of exerting eight times the     
power1 so far as  regards the element of
 atmospheric resistance4 ,we know by    
experience1  however1 that it is easier 
to attain high speeds on railways than  
in steam  vessels1 where the resistance 
does increase nearly as the square of   
the  speed4    #ejb4 ,q4--,will you     
describe generally the arrangement of a 
locomotive  engine8    ,a4--,the boiler 
and engine are hung upon a framework set

 on wheels1 and1  together with this    
frame or carriage1 constitute what is   
commonly called  the locomotive4 ,behind
 the locomotive runs another carriage1  
called the  tender1 for holding coke and
 water4 ,a common mode of connecting the
 engine  and tender is by means of a    
rigid bar1 with an eye at each end      
through  which pins are passed4 ,between
 the engine and tender1 however1 buffers
  should always be interposed1 as their 
pressure contributes greatly to  prevent
 oscillation and other irregular motions
 of the engine4    #ejc4 ,q4--,how is   
the framing of a locomotive usually     
constructed8    ,a4--,all locomotives   
are now made with the framing which     
supports the  machinery situated within 
the wheels2 but for some years a        
vehement  controversy was maintained    
respecting the relative merits of       
outside and  inside framing1 which has  
terminated1 however1 in the universal   
adoption of  the inside framing4 ,it is 
difficult1 in engines intended for the  

narrow  gauge1 to get cylinders within  
the framing of sufficient diameter to   
meet  the exigencies of railway         
locomotion2 by casting both cylinders in
 a piece1  however1 a considerable      
amount of room may be made available to 
increase  their diameters4 ,it is very  
desirable that the cylinders of         
locomotives  should be as large as      
possible1 so that expansion may be      
adopted to a large  extent2 and with any
 given speed of piston1 the power of an 
engine either  to draw heavy loads1 or  
achieve high velocities1 will be        
increased with  every increase of the   
dimensions of the cylinder4 ,the framing
 of  locomotives1 to which the boiler   
and machinery are attached1 and which   
rests upon the springs situated above   
the axles1 is formed generally of       
malleable iron1 but in some engines the 
side frames consist of oak with  iron   
plates riveted on each side4 ,the guard 
plates are in these cases  generally of 
equal length1 the frames being curved   

upward to pass over the  driving axle4  
,hard cast iron blocks are riveted      
between the guard plates to  serve as   
guides for the axle bushes4 ,the side   
frames are connected across  the ends1  
and cross stays are introduced beneath  
the boiler to stiffen the  frame        
sideways1 and prevent the ends of the   
connecting or eccentric rods  from      
falling down if they should be broken4  
#ejd4 ,q4--,what is the nature and      
arrangement of the springs of           
locomotives8    ,a4--,the springs are of
 the ordinary carriage kind1 with plates
 connected  at the centre1 and allowed  
to slide on each other at their ends4   
,the upper  plate terminates in two     
eyes1 through each of which passes a    
pin1 which  also passes through the jaws
 of the bridle1 connected by a double   
threaded  screw to another bridle1 which
 is jointed to the framing2 the centre  
of the  spring rests upon the axle box4 
,sometimes the springs are placed       
between  the guard plates1 and below the

 framing which rests upon their         
extremities4  ,one species of springs   
which has gained a considerable         
introduction1  consists of a number of  
flat steel plates with a piece of metal 
or other  substance interposed between  
them at the centre1 leaving the ends    
standing  apart4 ,it would be           
preferable1 perhaps1 to make the plates 
of a common  spring with different      
curves1 so that the leaves1 though in   
contact at the  centre1 would not be in 
contact with the ends with light loads1 
but would  be brought into contact      
gradually1 as the strain conies on3 a   
spring would  thus be obtained that was 
suitable for all loads4    #eje4        
,q4--,what is the difference between    
inside and outside cylinder  engines8   
,a4--,outside cylinders are so          
designated when placed upon the outside 
of  the framing1 with their connecting  
rods operating upon pins in the driving 
wheels2 while the inside cylinders are  
situated within the framing1 and the    

connecting rods attach themselves to    
cranks in the driving axle4    #ejf4    
,q4--,whether are inside or outside     
cylinder engines to be preferred8       
,a4--,a diversity of opinion obtains as 
to the relative merits of outside  and  
inside cylinders4 ,the chief objection  
to outside cylinders is1 that  they     
occasion a sinuous motion in the engine 
which is apt to send the train  off the 
rails2 but this action may be made less 
perceptible or be remedied  altogether1 
by placing a weight upon one side of the
 wheels1 the momentum  of which will    
just balance the momentum of the piston 
and its connections4  ,the sinuous or   
rocking motion of locomotives is        
traceable to the arrested  momentum of  
the piston and its attachments at every 
stroke of the engine1  and the effect of
 the pressure thus created will be more 
operative in  inducing oscillation the  
farther it is exerted from the central  
line of the  engine4 ,if both cylinders 
were set at right angles in the centre  

of the  carriage1 and the pistons were  
both attached to a central crank1 there 
would be no oscillation produced2 or the
 same effect would be realized by       
placing one cylinder in the centre of   
the carriage1 and two at the sides--    
the pistons of the side cylinders moving
 simultaneously3 but it is  impossible  
to couple the piston of an upright      
cylinder direct to the axle  of a       
locomotive1 without causing the springs 
to work up and down with every  stroke  
of the engine3 and the use of three     
cylinders1 though adopted in  some of   
,stephenson's engines1 involves too much
 complication to be a  beneficial       
innovation4    #ejg4 ,q4--,whether are  
four-wheeled or six-wheeled engines     
preferable8    ,a4--,much controversial 
ingenuity has been expended upon the    
question of  the relative merits of the 
four and six-wheeled engines2 one party 
maintaining that four-wheeled engines   
are most unsafe1 and the other that     
six-wheeled engines are unmechanical1   

and are more likely to occasion         
accidents4 ,the four-wheeled engines1   
however1 appear to have been charged    
with faults that do not really attach to
 them when properly constructed2  for it
 by no means follows that if the axle of
 a four-wheeled engine  breaks1 or even 
altogether comes away1 that the engine  
must fall down or  run off the line2    
inasmuch as1 if the engine be properly  
coupled with the  tender1 it has the    
tender to sustain it4 ,it is obvious    
enough1 that such a  connection may be  
made between the tender and the engine1 
that either the  fore or hind axle of   
the engine may be taken away1 and yet   
the engine will  not fall down1 but will
 be kept up by the support which the    
tender affords2  and the arguments      
hitherto paraded against the            
four-wheeled engines are1 so  far as    
regards the question of safety1 nothing 
more than arguments against  the        
existence of the suggested connection4  
,it is no doubt the fact1 that          

locomotive engines are now becoming too 
heavy to be capable of being borne  on  
four wheels at high speeds without      
injury to the rails2 but the  objection 
of damage to the rails applies with at  
least equal force to most  of the       
six-wheeled engines hitherto            
constructed1 as in those engines the    
engineer has the power of putting nearly
 all the weight upon the driving        
wheels2 and if the rail be wet or       
greasy1 there is a great temptation to  
increase the bite of those wheels by    
screwing them down more firmly upon  the
 rails4 ,a greater strain is thus thrown
 upon the rail than can exist in  the   
case of any equally heavy four-wheeled  
engine2 and the engine is made  very    
unsafe1 as a pitching motion will       
inevitably be induced at high  speeds1  
when an engine is thus poised upon the  
central driving wheels1 and  there will 
also be more of the rocking or sinuous  
motion4 ,locomotives1  however1 intended
 to achieve high speeds or to draw heavy

 loads1 are now  generally made with    
eight wheels1 and in some cases the     
driving wheels are  placed at the end of
 the engine instead of in the middle4   
#ejh4 ,q4--,as the question of the      
locomotive boiler has been already      
disposed of in discussing the question  
of boilers in general1 it now only      
remains to inquire into the subject of  
the engine1 and we may commence with    
the cylinders4 ,will you state the      
arrangement and construction of the     
cylinders of a locomotive and their     
connections8    ,a4--,the cylinders are 
placed in the same horizontal plane as  
the axle of  the driving wheels1 and the
 connecting rod which is attached to the
 piston  rod engages either a crank in  
the driving axle or a pin in the driving
  wheel1 according as the cylinders are 
inside or outside of the framework4     
,the cylinders are generally made an    
inch longer than the stroke1 or there   
is half an inch of clearance at each end
 of the cylinder1 to permit the  springs

 of the vehicle to act without causing  
the piston to strike the top  or bottom 
of the cylinder4 ,the thickness of metal
 of the cylinder ends is  usually about 
a third more than the thickness of the  
cylinder itself1 and  both ends are     
generally made removable4 ,the priming  
of the boiler1 when it  occurs1 is very 
injurious to the cylinders and valves of
 locomotives1  especially if the water  
be sandy1 as the grit carried over by   
the steam  wears the rubbing surfaces   
rapidly away4 ,the face of the cylinder 
on which  the valve works is raised a   
little above the metal around it1 both  
to  facilitate the operation of forming 
the face and with the view of enabling  
any foreign substance deposited on the  
face to be pushed aside by the valve    
into the less elevated part1 where it   
may lie without occasioning any  further
 disturbance4 ,the valve casing is      
sometimes cast upon the cylinder1  and  
it is generally covered with a door     
which may be removed to permit the      

inspection of the faces4 ,in some valve 
casings the top as well as the back  is 
removable1 which admits of the valve and
 valve bridle being removed with        
greater facility4 ,a cock is placed at  
each end of locomotive cylinders1 to    
allow the water to be discharged which  
accumulates in the cylinder from        
priming or condensation2 and the four   
cocks of the two cylinders are  usually 
connected together1 so that by turning a
 handle the whole are  opened at once4  
,in ,stephenson's engines1 however1 with
 variable expansion1  there is but one  
cock provided for this purpose1 which is
 on the bottom of  the valve chest4     
#eji4 ,q4--,what kind of piston is used 
in locomotives8    ,a4--,the variety of 
pistons employed in locomotives is very 
great1 and  sometimes even the more     
complicated kinds are found to work very
  satisfactorily2 but1 in general1 those
 pistons which consist of a single  ring
 and tongue piece1 or of two single     
rings set one above the other1 so  as to

 break joint1 are preferable to those   
which consist of many pieces4 ,in       
,stephenson's pistons the screws were at
 one time liable to work slack1 and  the
 springs to break4    #eaj4 ,q4--,will  
you explain the connection of the piston
 rod with the  connecting rod8          
,a4--,the piston rods of all engines are
 now generally either case hardened     
very deeply1 or are made of steel2 and  
in locomotive engines the diameter  of  
the piston rod is about one seventh of  
the diameter of the cylinder1 and  it is
 formed of tilted steel4 ,the cone of   
the piston rod1 by which it is  attached
 to the piston1 is turned the reverse   
way to that which is adopted  in common 
engines1 with the view of making the    
cutter more accessible from  the bottom 
of the cylinder1 which is made to come  
off like a door4 ,the top  of the piston
 rod is secured with a cutter into a    
socket with jaws1 through  the holes of 
which a cross head passes1 which is     
embraced between the jaws  by the small 

end of the connecting rod1 while the    
ends of the cross head  move in guides4 
,between the piston rod clutch and the  
guide blocks1 the  feed pump rod joins  
the cross head in some engines4    #eaa4
 ,q4--,what kind of guides is employed  
for the end of the piston rod8          
,a4--,the guides are formed of steel    
plates attached to the framing1  between
 which work the guide blocks1 fixed on  
the ends of the cross head1  which have 
flanges bearing against the inner edges 
of the guides4 ,steel or  brass guides  
are better than iron ones3 ,stephenson  
and ,hawthorn attach  their guides at   
one end to a cross stay1 at the other to
 lugs on the  cylinder cover2 and they  
are made stronger in the middle than at 
the ends4  ,stout guide rods of steel1  
encircled by stuffing boxes on the ends 
of the  cross head1 would probably be   
found superior to any other arrangement4
 ,the  stuffing boxes might contain     
conical bushes1 cut spirally1 in        
addition to  the packing1 and a ring1   

cut spirally1 might be sprung upon the  
rod and  fixed in advance of the        
stuffing box1 with lateral play to wipe 
the rod  before entering the stuffing   
box1 to prevent it from being scratched 
by the  adhesion of dust4    #eab4      
,q4--,is any provision made for keeping 
the connecting rod always of  the same  
length8    ,a4--,in every kind of       
locomotive it is very desirable that the
 length of  the connecting rod should   
remain invariable1 in spite of the wear 
of the  brasses1 for there is a danger  
of the piston striking against the cover
 of  the cylinder if it be shortened1 as
 the clearance is left as small as      
possible in order to economize steam4   
,in some engines the strap encircling   
the crank pin is fixed immovably to the 
connecting rod by dovetailed keys1  and 
a bolt passes through the keys1 rod1 and
 strap1 to prevent the  dovetailed keys 
from working out4 ,the brass is         
tightened by a gib and  cutter1 which is
 kept from working loose by three       

pinching screws and a  cross pin or     
cutter through the point4 ,the effect of
 this arrangement is to  lengthen the   
rod1 but at the cross head end of the   
rod the elongation is  neutralized by   
making the strap loose1 so that in      
tightening the brass the  rod is        
shortened by an amount equal to its     
elongation at the crank pin end4  ,the  
tightening here is also effected by a   
gib and cutter1 which is kept  from     
working loose by two pinching screws    
pressing on the side of the  cutter4    
,both journals of the connecting rod are
 furnished with oil cups1  having a     
small tube in the centre with siphon    
wicks4 ,the connecting rod is  a thick  
flat bar1 with its edges rounded4       
#eac4 ,q4--,how is the cranked axle of  
locomotives constructed8    ,a4--,the   
cranked axle of locomotives is always   
made of wrought iron1 with  two cranks  
forged upon it toward the middle of its 
length1 at a distance  from each other  
answerable to the distance between the  

cylinders4 ,bosses  are made on the axle
 for the wheels to be keyed upon1 and   
bearings for the  support of the        
framing4 ,the axle is usually forged in 
two pieces1 which are  afterward welded 
together4 ,sometimes the pieces for the 
cranks are put on  separately1 but the  
cranks so made are liable to give way4  
,in engines with  outside cylinders the 
axles are made straight-the crank pins  
being inserted  in the naves of the     
wheels4 ,the bearings to which the      
connecting rods are  attached are made  
with very large fillets in the corners1 
so as to  strengthen the axle in that   
part1 and to obviate side play in the   
connecting rod4 ,in engines which1 have 
been in use for some time1 however1     
there is generally a good deal of end   
play in the bearings of the axles       
themselves1 and this slackness          
contributes to make the oscillation of  
the  engine more violent2 but this evil 
may be remedied by making the bearings  
spheroidal1 whereby end play becomes    

impossible4    #ead4 ,q4--,how are the  
bearings of the axles arranged8         
,a4--,the axles bear only against the   
top of the axle boxes1 which are        
generally of brass2 but a plate extends 
underneath the bearing1 to prevent  sand
 from being thrown upon it4 ,the upper  
part of the box in most engines  has a  
reservoir of oil1 which is supplied to  
the journal by tubes with  siphon wicks4
 ,stephenson uses cast iron axle boxes  
with brasses1 and grease  instead of    
oil2 and the grease is fed upon the     
journal by the heat of the  bearing     
melting it1 whereby it is made to flow  
down through a hole in the  brass4 ,any 
engines constructed with outside        
bearings have inside bearings  also1    
which are supported by longitudinal     
bars1 which serve also in some  cases to
 support the piston guides2 these       
bearings are sometimes made so as  not  
to touch the shafts unless they break4  
#eae4 ,q4--,how are the eccentrics of a 
locomotive constructed8    ,a4--,in     

locomotives the body of the eccentric is
 of cast iron1 in inside  cylinder      
engines the eccentrics are set on the   
axle between the cranks1 and  they are  
put on in two pieces held together by   
bolts2 but in straight axle  engines the
 eccentrics are cast in a piece1 and are
 secured on the shaft by  means of a    
key4 ,the eccentric1 when in two pieces1
 is retained at its  proper angle on the
 shaft by a pinching screw1 which is    
provided with a jam  nut to prevent it  
from working loose4 ,a piece is left out
 of the eccentric  in casting it to     
allow of the screw being inserted1 and  
the void is  afterward filled by        
inserting a dovetailed piece of metal4  
,stephenson and  ,hawthorn leave holes  
in their eccentrics on each side of the 
central arm1  and they apply pinching   
screws in each of these holes4 ,the     
method of fixing  the eccentric to the  
shaft by a pinching screw is scarcely   
sufficiently  substantial2 and cases are
 perpetually occurring1 when this method

 of  attachment is adopted1 of          
eccentrics shifting from their place4   
,in the  modern engines the eccentrics  
are forged on the axles4    #eaf4       
,q4--,how are the eccentric straps      
constructed8    ,a4--,the eccentric     
hoops are generally of wrought iron1 as 
brass hoops are  found liable to break4 
,when formed of malleable iron1 one half
 of the strap  is forged with the rod1  
the other half being secured to it by   
bolts1 nuts1  and jam nuts4 ,pieces of  
brass are1 in some cases1 pinned within 
the  malleable iron hoop2 but it appears
 to be preferable to put brasses within 
the hoop to encircle the eccentric1 as  
in the case of any other bearing4  ,when
 the brass straps are used1 the lugs    
have generally nuts on both sides1  so  
that the length of the eccentric rod may
 be adjusted by their means to  the     
proper length2 but it is better for the 
lugs of the hoops to abut  against the  
necks of the screws1 and1 if any        
adjustment be necessary from  the wear  

of the straps1 washers can be           
interposed4 ,in some engines the        
adjustment is effected by screwing the  
valve rod1 and the cross head  through  
which it passes has a nut on either side
 of it1 by which its  position upon the 
valve rod is determined4    #eag4       
,q4--,will you describe the eccentric   
rod and valve levers8    ,a4--,in the   
engines in use before the introduction  
of the link motion1 the  forks of the   
eccentric rod were of steel1 and the    
length of the eccentric  rod was the    
distance between the centre of the crank
 axle and the centre of  the valve      
shaft2 but in modern engines the use of 
the link motion is  universal4 ,the     
valve lever in locomotives is usually   
longer than the  eccentric lever1 to    
increase the travel of the valve1 if    
levers are  employed2 but it is better  
to connect the valve rod to the link of 
the link  motion without the            
intervention of levers4 ,the pins of the
 eccentric lever  in the old engines    

used to wear quickly2 ,stephenson used  
to put a ferule of  brass on these pins1
 which being loose1 and acting like a   
roller1  facilitated the throwing in and
 out of gear1 and when worn could easily
 be  replaced1 so that there was no     
material derangement of the motion of   
the  valve from play in this situation4 
#eah4 ,q4--,what is the arrangement of a
 starting lever8    ,a4--,the starting  
lever travels between two iron segments1
 and can be  fixed in any desired       
position4 ,this is done by a small catch
 or bell crank1  jointed to the bottom  
of the handle at the end of the lever1  
and coming up  by the side of the       
handle1 but pressed out from it by a    
spring4 ,the smaller  arm of this bell  
crank is jointed to a bolt1 which shoots
 into notches1  made in one of the      
segments between which the lever moves4 
,by pressing the  bell crank against the
 handle of the lever the bolt is        
withdrawn1 and the  lever may be shifted
 to any other point1 when1 the spring   

being released1  the bolt flies into the
 nearest notch4    #eai4 ,q4--,in what  
way does the starting handle act on the 
machinery of the  engine to set it in   
motion8    ,a4--,its whole action lies  
in raising or depressing the link of the
 link  motion relatively with the valve 
rod4 ,if the valve rod be attached to   
the  middle of the link1 the valve will 
derive no motion from1 it at all1 and   
the engine will stop4 ,if the attachment
 be slipped to one end of the link  the 
engine will go ahead1 and if slipped to 
the other end it will go  astern4 ,the  
starting handle merely achieves this    
change of position4    #ebj4 ,q4--,will 
you explain the operation of setting the
 valve of a  locomotive8    ,a4--,in    
setting the valves of locomotives1 place
 the crank in the position  answerable  
to the end of the stroke of the piston1 
and draw a straight  line1 representing 
the centre line of the cylinder1 through
 the centres of  the crank shaft and    
crank pin4 ,from the centre of the shaft

 describe a  circle with the diameter   
equal to the throw of the valve2 another
 circle to  represent the crank shaft2  
and a third circle to represent the path
 of the  crank pin4 ,from the centre of 
the crank shaft1 draw a line            
perpendicular to  the centre line of the
 cylinder and crank shaft1 and draw     
another  perpendicular at a distance    
from the first equal to the amount of   
the lap  and the lead of the valve3 the 
points in which this line intersects the
  circle of the eccentric are the points
 in which the centre of the eccentric   
should be placed for the forward and    
reverse motions4 ,when the eccentric    
rod is attached directly to the valve1  
the radius of the eccentric1 which      
precedes the crank in its revolution1   
forms with the crank an obtuse angle2   
but when1 by the intervention of levers1
 the valve has a motion1 opposed to     
that of the eccentric rod1 the angle    
contained by the crank and the radius   
of the eccentric must be acute1 and the 

eccentric must follow the crank3 in     
other words1 with a direct attachment to
 the valve the eccentric is set  more   
than one fourth of a revolution in      
advance of the crank1 and with an       
indirect attachment the eccentric is set
 less than one fourth of a circle       
behind the crank4 ,if the valve were    
without lead or lap the eccentric would 
be exactly one fourth of a circle in    
advance of the crank or behind the      
crank1 according to the nature of the   
valve connection2 but as the valve      
would thus cover the port by the amount 
of the lap and lead1 the eccentric  must
 be set forward so as to open the port  
to the extent of the lap and  lead1 and 
this is effected by the plan just       
described4    #eba4 ,q4--,in the event  
of the eccentrics slipping round upon   
the shaft1  which you stated sometimes  
happens1 is it necessary to perform the 
operation of setting the valve as you   
have just described it8    ,a4--,if the 
eccentrics shift upon the shaft1 they   

may be easily refixed by  setting the   
valve open the amount of the lead1      
setting the crank at the end  of the    
stroke1 and bringing round the eccentric
 upon the shaft till the  eccentric rod 
gears with the valve4 ,it would often be
 troublesome in  practice to get access 
to the valve for the purpose of setting 
it1 and this  may be dispensed with if  
the amount of lap on the valve and the  
length of  the eccentric rod be known4  
,to this end draw upon a board two      
straight  lines at right angles to one  
another1 and from their point of        
intersection  as a centre describe two  
circles1 one representing the circle of 
the  eccentric1 the other the crank     
shaft2 draw a straight line parallel to 
one  of the diameters1 and distant from 
it the amount of the lap and the lead3  
the points in which his parallel        
intersects the circle of the eccentric  
are  the positions of the forward and   
backward eccentrics4 ,through these     
points  draw straight lines from the    

centre of the circle1 and mark the      
intersection of these lines with the    
circle of the crank shaft2 measure  with
 a pair of compasses the chord of the   
arc intercepted between either of  these
 points1 and the diameter which is at   
right angles with the crank1 and  the   
diameters being first marked on the     
shaft itself1 then by transferring  with
 the compasses the distance found in the
 diagram1 and marking the  point1 the   
eccentric may at any time be adjusted   
without difficulty4    ,illustration3   
,fig4 #de4    #ebb4 ,q4--,will you      
describe the structure and arrangement  
of the feed  pumps of locomotive        
engines8    ,a4--,the feed pumps of     
locomotives are generally made of brass1
 but the  plungers are sometimes made of
 iron1 and are generally attached to the
  piston1 cross head1 though in         
,stephenson's engines they are worked by
 rods  attached to eyes on the eccentric
 hoops4 ,there is a ball valve1 fig4    
#de1  between the pump and the tender1  

and two usually in the pipe leading from
  the pump to the boiler1 besides a cock
 close to the boiler1 by which the  pump
 may be shut off from the boiler in case
 of any accident to the valves4  ,the   
ball valves are guided by four branches1
 which rise vertically1 and  join       
together at the top in a hemispherical  
form4 ,the shocks of the ball  against  
this cap have in some cases broken it   
after one week's work1 from  the top of 
the cage having been flat1 and the      
branches not having had their  junction 
at the top properly filleted4 ,these    
valve guards are attached in  different 
ways to the pipes2 when one occurs at   
the junction of two pieces  of pipe it  
has a flange1 which along with the      
flanges of the pipes and that  of the   
valve seat are held together by a union 
joint4 ,it is sometimes  formed with a  
thread at the under end1 and screwed    
into the pipe4 ,the balls  are cast     
hollow to lessen the shock1 as well as  
to save the metal4 ,in some  cases where

 the feed pump plunger has been attached
 to the cross head1 the  piston rod has 
been bent by the strain2 and that must  
in all cases occur1  if the             
communication between the pump and      
boiler be closed when the engine  is    
started1 and there be no escape valve   
for the water4    #ebc4 ,q4--,are none  
but ball valves used in the feed pump8  
,a4--,spindle valves have in some cases 
been used instead of ball valves1  but  
they are more subject to derangement2   
but piston valves1 so contrived  as to  
shut a portion of water in the cage when
 about to close1 might be  adopted with 
a great diminution of the shock4 ,slide 
valves might be  applied1 and would     
probably be found preferable to any of  
the expedients at  present in use4 ,in  
all spindle valves opened and shut      
rapidly1 it is  advisable to have the   
lower surface conical1 to take off the  
shock of the  water2 and a large lift of
 the valve should be prevented1 else    
much of the  water during the return    

stroke of the pump will flow out before 
the valve  shuts4    #ebd4 ,q4--,at what
 part of the boiler is the feed water   
admitted8    ,a4--,the feed pipe of most
 locomotive engines enters the boiler   
near the  bottom and about the middle of
 its length4 ,in ,stephenson's engine   
the water  is let in at the smoke box   
end of the boiler1 a little below the   
water  level2 by this means the heat is 
more fully extracted from the escaping  
smoke1 but the arrangement is of        
questionable applicability to engines of
  which the steam dome and steam pipe   
are at the smoke box end1 as in that    
case the entering cold water would      
condense the steam4    #ebe4 ,q4--,how  
are the pipes connecting the tender and 
locomotive  constructed1 so as to allow 
of play between the engine and tender   
without  leakage8    ,a4--,the pipes    
connecting the tender with the pumps    
should allow access to  the valves and  
free motion to the engine and tender4   
,this end is attained  by the use of    

ball and socket joints2 and1 to allow   
some end play1 one  piece of the pipe   
slides into the other like a telescope1 
and is kept tight  by means of a        
stuffing box4 ,any pipe joint between   
the engine and tender  must be made in  
this fashion4    #ebf4 ,q4--,have you   
any suggestion to make respecting the   
arrangement of  the feed pump8          
,a4--,it would be a material improvement
 if a feed pump was to be set in  the   
tender and worked by means of a small   
engine1 such as that now used in  steam 
vessels for feeding the boilers4 ,the   
present action of the feed pumps  of    
locomotives is precarious1 as1 if the   
valves leak in the slightest  degree1   
the steam or boiling water from the     
boiler will prevent the pumps  from     
drawing4 ,it appears expedient1         
therefore1 that at least one pump       
should be far from the boiler and should
 be set among the feed water1 so  that  
it will only have to force4 ,if a pump  
was arranged in the manner  suggested1  

the boiler could still be fed regularly1
 though the locomotive  was standing    
still2 but it would be prudent to have  
the existing pumps  still wrought in the
 usual way by the engine1 in case of    
derangement of the  other1 or in case   
the pump in the tender might freeze4    
#ebg4 ,q4--,will you explain the        
construction of locomotive wheels8      
,a4--,the wheels of a locomotive are    
always made of malleable iron4 ,the     
driving wheels are made larger to       
increase the speed2 the bearing wheels  
also are easier on the road when large4 
,in the goods engines the driving       
wheels are smaller than in the passenger
 engines1 and are generally coupled     
together4 ,wheels are made with much    
variety in their constructive details3  
sometimes they are made with cast iron  
naves1 with the spokes and rim of       
wrought iron2 but in the best modern    
wheels the nave is formed of the ends   
of the spokes welded together at the    
centre4 ,when cast iron naves are       

adopted1 the spokes are forged out of   
flat bars with ,t-formed heads1 and  are
 arranged radially in the founder's     
mould1 the cast iron1 when fluid1  being
 poured among them4 ,the ends of the ,t 
heads are then welded together  to      
constitute the periphery of the wheel or
 inner tire2 and little  wedge-form     
pieces are inserted where there is any  
deficiency of iron4 ,in  some cases the 
arms are hollow1 though of wrought iron2
 the tire of wrought  iron1 and the nave
 of cast iron2 and the spokes are turned
 where they are  fitted into the nave1  
and are secured in their sockets by     
means of cutters4  ,hawthorn makes his  
wheels with cast iron naves and wrought 
iron rims and  arms2 but instead of     
welding the arms together1 he makes     
palms on their  outer end1 which are    
attached by rivets to the rim4 ,these   
rivets1 however1  unless very carefully 
formed1 are apt to work loose2 and it   
would probably  be found an improvement 
if the palms were to be slightly        

indented into the  rim1 in cases in     
which the palms do not meet each other  
at the ends4 ,when  the rim is turned it
 is ready for the tire1 which is now    
made of steel4    #ebh4 ,q4--,how do you
 find the length of bar necessary for   
forming a tire8    ,a4--,to find the    
proper length of bar requisite for the  
formation of a  hoop of any given       
diameter1 add the thickness of the bar  
to the required  diameter1 and the      
corresponding circumference in the table
 of  circumferences of circles is the   
length of the bar4 ,if the iron be bent 
edgewise the breadth of the bar must be 
added to the diameter1 for it is  the   
thickness of the bar measured radially  
that is to be taken into  consideration4
 ,in the tires of railway wheels1 which 
have a flange on one  edge1 it is       
necessary to add not only the thickness 
of the tire1 but also  two thirds of the
 depth of the flange2 generally1        
however1 the tire bars  are sent from   
the forge so curved that the plain edge 

of the tire is  concave1 and the flange 
edge convex1 while the side which is    
afterward to  be bent into contact with 
the cylindrical surface of the wheel is 
a plane4  ,in this case the addition of 
the diameter of two thirds of the depth 
of the  flange is unnecessary1 for the  
curving of the flange edge has the      
effect of  increasing the real length of
 the bar4 ,when the tire is thus curved1
 it is  only necessary to add the       
thickness of the hoop to the diameter1  
and then  to find the circumference from
 a table2 or the same result will be    
obtained  by multiplying the diameter   
thus increased by the thickness of the  
hoop by  #c4adaf4    #ebi4 ,q4--,how are
 the tires attached to the wheels8      
,a4--,the materials for wheel tires are 
first swaged separately1 and then       
welded together under the heavy hammer  
at the steel works2 after which they    
are bent to the circle1 welded1 and     
turned to certain gauges4 ,the tire is  
now heated to redness in a circular     

furnace2 during the time it is getting  
hot1 the iron wheel1 turned to the right
 diameter1 is bolted down upon a  face  
plate or surface2 the tire expands with 
the heat1 and when at a cherry  red1 it 
is dropped over the wheel1 for which it 
was previously too small1  and it is    
also hastily bolted down to the surface 
plate2 the whole mass is  then quickly  
immersed by a swing crane in a tank of  
water five feet deep1  and hauled up and
 down till nearly cold2 the tires are   
not afterward  tempered4 ,the tire is   
attached to the rim with rivets having  
countersunk  heads1 and the wheel is    
then fixed on its axle4    #ecj4        
,q4--,is it necessary to have the whole 
tire of steel8    ,a4--,it is not       
indispensable that the whole tire should
 be of steel2 but a  dovetail groove1   
turned out of the tire at the place     
where it bears most on  the rail1 and   
fitted with a band of steel1 will       
suffice4 ,this band may be  put in in   
pieces1 and the expedient appears to be 

the best way of repairing  a worn tire2 
but particular care must be taken to    
attach these pieces very  securely to   
the tire by rivets1 else in the rapid   
revolution of the wheel  the steel may  
be thrown out by the centrifugal force4 
,in aid of such  attachment the steel1  
after being introduced1 is well         
hammered1 which  expands it sideways    
until it fills the dovetail groove4     
#eca4 ,q4--,is any arrangement adopted  
to facilitate the passage of the        
locomotive round curves8    ,a4--,the   
tire is turned somewhat conical1 to     
facilitate the passage of the  engine   
round curves--the diameter of the outer 
wheel being virtually  increased by the 
centrifugal force of the engine1 and    
that of the inner  wheel being          
correspondingly diminished1 whereby the 
curve is passed without  the resistance 
which would otherwise arise from the    
inequality of the  spaces passed over by
 wheels of the same diameter fixed upon 
the same axle4  ,the rails1 moreover1   

are not set quite upright1 but are      
slightly inclined  inward1 in           
consequence of which the wheels must be 
either conical or  slightly dished1 to  
bear fairly upon the rails4 ,one benefit
 of inclining  the rails in this way1   
and coning the tires1 is that the flange
 of the  wheels is less liable to bear  
against the sides of the rail1 and with 
the  same view the flanges of all the   
wheels are made with large fillets in   
the  corners4 ,wheels have been placed  
loose upon the axle1 but they have less 
stability1 and are not now much used4   
,nevertheless this plan appears to be  a
 good one if properly worked out4       
#ecb4 ,q4--,are any precautions taken to
 prevent engines from being thrown  off 
the rails by obstructions left upon the 
line8    ,a4--,in most engines a bar is 
strongly attached to the front of the   
carriage on each side1 and projects     
perpendicularly downward to within a    
short distance of the rail1 to clear    
away stones or other obstructions that  

might occasion accidents if the engine  
ran over them4          ,,chapter ,,ix4 
,,steam ,,navigation4           99      
99       99       99       99           
,,resistance ,,of ,,vessels ,,in        
,,water4    #ecc4 ,q4--,how do you      
determine the resistance encountered by 
a vessel  moving in water8    ,a4--,the 
resistance experienced by vessels moving
 in water varies as the  square of the  
velocity of their motion1 or nearly so2 
and the power  necessary to impart an   
increased velocity varies nearly as the 
cube of such  increased velocity4 ,to   
double the velocity of a steam vessel1  
therefore1  will require four times the 
amount of tractive force1 and as that   
quadrupled force must act through twice 
the distance in the same time1 an       
engine capable of exerting eight times  
the original power will be  required4#a 
#ecd4 ,q4--,in the case of a board      
moving in water in the manner of a      
paddle  float1 or in the case of moving 
water impinging on a stationary board1  

what  will be the pressure produced by  
the impact8    ,a4--,the pressure       
produced upon a flat board1 by striking 
water at right  angles to the surface of
 the board1 will be equal to the weight 
of a column  of water having the surface
 struck as a base1 and for its altitude 
twice  the height due to the velocity   
with which the board moves through the  
water4 ,if the board strike the water   
obliquely1 the resistance will be  less1
 but no very reliable law has yet been  
discovered to determine its  amount4    
#ece4 ,q4--,will not the resistance of a
 vessel in moving through the water  be 
much less than that of a flat board of  
the area of the cross section8          
,a4--,it will be very much less1 as is  
manifest from the comparatively  small  
area of paddle board1 and the small area
 of the circle described by  the screw1 
relatively with the area of the immersed
 midship section of the  vessel4 ,the   
absolute speed of a vessel1 with any    
given amount of power1  will depend very

 much upon her shape4    #ecf4 ,q4--,in 
what way is it that the shape of a      
vessel influences her  speed1 since the 
vessels of the same sectional area must 
manifestly put in  motion a column of   
water of the same magnitude1 and with   
the same velocity8    ,a4--,a vessel    
will not strike the water with the same 
velocity when the  bow lines are sharp  
as when they are otherwise2 for a very  
sharp bow has  the effect of enabling   
the vessel to move through a great      
distance1 while  the particles of water 
are moved aside but a small distance1 or
 in other  words1 it causes the velocity
 with which the water is moved to be    
very  small relatively with the velocity
 of the vessel2 and as the resistance   
increases as the square of the velocity 
with which the water is moved1 it  is   
conceivable enough in what way a sharp  
bow may diminish the resistance4        
#ecg4 ,q4--,is the whole power expended 
in the propulsion of a vessel  consumed 
in moving aside the water to enable the 

vessel to pass8    ,a4--,by no means2   
only a portion1 and in well-formed      
vessels only a small  portion1 of the   
power is thus consumed4 ,in the majority
 of cases1 the  greater part of the     
power is expended in overcoming the     
friction of the  water upon the bottom  
of the vessel2 and the problem chiefly  
claiming  consideration is1 in what way 
we may diminish the friction4    #ech4  
,q4--,does the resistance produced by   
this friction increase with the         
velocity8    ,a4--,it increases nearly  
as the square of the velocity4 ,at two  
nautical  miles per hour1 the thrust    
necessary to overcome the friction      
varies as the  #a4hbc power of the      
velocity2 and at eight nautical miles   
per hour1 the  thrust necessary to      
overcome the friction varies as the     
#a4gac power of the  velocity4 ,it is   
hardly proper1 perhaps1 to call this    
resistance by the name  of friction2 it 
is partly1 perhaps mainly1 due to the   
viscidity or adhesion  of the water4    

#eci4 ,q4--,perhaps at high velocities  
this resistance may become less8        
,a4--,that appears very probable4 ,it   
may happen that at high velocities the  
adhesion is overcome1 so that the water 
is dragged off the vessel1 and the      
friction thereafter follows the law     
which obtains in the case of solid      
bodies4 ,but any such conclusion is mere
 speculation1 since no experiments      
illustrative of this question have yet  
been made4    #edj4 ,q4--,will a vessel 
experience more resistance in moving in 
salt water  than in moving in fresh8    
,a4--,if the immersion be the same in   
both cases a vessel will experience     
more resistance in moving in salt water 
than in moving in fresh1 on account  of 
the greater density of salt water2 but  
as the notation is proportionably       
greater in the salt water the resistance
 will be the same with the same  weight 
carried4    #eda4 ,q4--,discarding for  
the present the subject of friction1 and
 looking  merely to the question of bow 

and stern resistance1 in what manner    
should  the hull of a vessel be formed  
so as to make these resistances a       
minimum8    ,a4--,the hull should be so 
formed that the water1 instead of being 
away  driven forcibly from the bow1 is  
opened gradually1 so that every particle
  of water may be moved aside slowly at 
first1 and then faster1 like the ball   
of a pendulum1 until it reaches the     
position of the midship frame1 at which 
point it will have come to a state of   
rest1 and then again1 like a  returning 
pendulum1 vibrate back in the same way1 
until it comes to rest at  the stern4   
,it is not difficult to describe        
mechanically the line which the  water  
should pursue4 ,if an endless web of    
paper be put into uniform motion1  and a
 pendulum carrying a pencil or brush be 
hung in front of it1 then such  pendulum
 will trace on the paper the proper     
water line of the ship1 or the  line    
which the water should pursue in order  
that no power may be lost  except that  

which is lost in friction4 ,it is found1
 however1 in practice1  that vessels    
formed with water lines on this         
principle are not much  superior to     
ordinary vessels in the facility with   
which they pass through  the water3 and 
this points to the conclusion that in   
ordinary vessels of  good form1 the     
amount of power consumed in overcoming  
the resistance due to  the wave at the  
bow and the partial vacuity at the stern
 is not so great as  has heretofore been
 supposed1 and that1 in fact1 the main  
resistance is  that due to the friction4
    #a ,this statement supposes that    
there is no difference of level between 
the water at the bow and the water at   
the stern4 ,in the experiments on the   
steamer ,pelican1 the resistance was    
found to vary1 as the #b4bhth power of  
the velocity1 but the deviation from the
 recognized law was imputed to a        
difference in the level of the water at 
the bow and stern4                      
,,experiments ,,on ,,the ,,resistance   

,,of ,,vessels4    #edb4 ,q4--,have     
experiments been made to determine the  
resistance which  steam vessels         
experience in moving through the waters8
    ,a4--,experiments have been made    
both to determine the relative          
resistance  of different classes of     
vessels1 and also the absolute          
resistance in pounds  or tons4 ,the     
first experiments made upon this subject
 were conducted by  ,messrs4 ,boulton   
and ,watt1 and they have been numerous1 
long continued1 and  carefully          
performed4 ,these experiments were made 
upon paddle vessels4    #edc4 ,q4--,will
 you recount the chief results of these 
experiments8    ,a4--,the purpose of the
 experiments was to establish a         
coefficient of  performance1 which with 
any given class of vessel would enable  
the speed1  which would be obtained with
 any given power1 to be readily         
predicted4 ,this  coefficient was       
obtained by multiplying the cube of the 
velocity of the  vessels experimented   

upon1 in miles per hour1 by the         
sectional area of the  immersed midship 
section in square feet1 and dividing by 
the numbers of  nominal horses power1   
and this coefficient will be large in   
the proportion  of the goodness of the  
shape of the vessel4    #edd4 ,q4--,how 
many experiments were made altogether8  
,a4--,there were five different sets of 
experiments on five different  classes  
of vessels4 ,the first set of           
experiments was made in #ahbh1 upon the 
vessels ,caledonia1 ,diana1 ,eclipse1   
,kingshead1 ,moordyke1 and              
,eagle-vessels  of a similar form and   
all with square bilges and flat floors2 
and the  result was to establish the    
number #ibe as the coefficient of       
performance of  such vessels4 ,the      
second set of experiments was made upon 
the superior  vessels ,venus1           
,swiftsure1 ,dasher1 ,arrow1 ,spitfire1 
,fury1 ,albion1 ,queen1  ,dart1 ,hawk1  
,margaret1 and ,hero-all vessels having 
flat floors and round  bilges1 where the

 coefficient became #aafj4 ,the third   
set of experiments was  made upon the   
vessels ,lightning1 ,meteor1 ,james     
,watt1 ,cinderella1 ,navy  ,meteor1     
,crocodile1 ,watersprite1 ,thetis1      
,dolphin1 ,wizard1 ,escape1 and         
,dragon-all vessels with rising floors  
and round bilges1 and the coefficient   
of performance was found to be #adcj4   
,the fourth set of experiments was made 
in #ahcd1 upon the vessels ,magnet1     
,dart1 ,eclipse1 ,flamer1 ,firefly1     
,ferret1  and ,monarch1 when the        
coefficient of performance was found to 
be #aehj4 ,the  fifth set of experiments
 was made upon the ,red ,rover1 ,city of
 ,canterbury1  ,herne1 ,queen1 and      
,prince of ,wales1 and in the case of   
those vessels the  coefficient rose to  
#beej4 ,the velocity of any of these    
vessels1 with any  power or sectional   
area1 may be ascertained by multiplying 
the coefficient  of its class by the    
nominal horse power1 dividing by the    
sectional area in  square feet1 and     

extracting the cube root of the         
quotient1 which will be  the velocity in
 miles per hour2 or the number of       
nominal horse power  requisite for the  
accomplishment of any required speed may
 be ascertained  by multiplying the cube
 of the required velocity in miles per  
hour1 by the  sectional area in square  
feet1 and dividing by the coefficient3  
the  quotient is the number of nominal  
horse power requisite to realize the    
speed4    #ede4 ,q4--,seeing1 however1  
that the nominal power does not         
represent an  invariable amount of      
dynamical efficiency1 would it not be   
better to make  the comparison with     
reference to the actual power8          
,a4--,in the whole of the experiments   
recited1 except in the case of one or   
two of the last1 the pressure of steam  
in the boiler varied between #b-c_/d    
lbs4 and #d lbs4 per square inch1 and   
the effective pressure on the piston    
varied between #aa lbs4 and #ac lbs4 per
 square inch1 so that the average  ratio

 of the nominal to the actual power may 
be easily computed2 but it  will be     
preferable to state the nominal power of
 some of the vessels1 and  their actual 
power as ascertained by experiment4     
#edf4 ,q4--,then state this4    ,a4--,of
 the ,eclipse1 the nominal power was    
#gf1 and the actual power #add4d        
horses2 of the ,arrow1 the nominal power
 was #fj1 and the actual #aai4e2        
,spitfire1 nominal #dj1 actual #fd2     
,fury1 nominal #dj1 actual #fe4f2       
,albion1  nominal #hj1 actual #ace4d2   
,dart1 nominal #ajj1 actual #aeb4d2     
,hawk1 nominal  #dj1 actual #gc2 ,hero1 
nominal #ajj1 actual #aga4d2 ,meteor1   
nominal #ajj1 actual  #afj2 ,james      
,watt1 nominal #abj1 actual #bjd2       
,watersprite1 nominal #gf1 actual       
#aeg4f2 ,dolphin1 nominal #adj1 actual  
#bch2 ,dragon1 nominal #hj1 actual #aca2
  ,magnet1 nominal #adj1 actual #bch2   
,dart1 nominal #abj1 actual #bcg2       
,flamer1  nominal #abj1 actual #bcd2    
,firefly1 nominal #eb1 actual #hf4f2    

,ferret1 nominal  #eb1 actual #hh2      
,monarch1 nominal #bjj1 actual #cgh4 ,in
 the case of swift  vessels of modern   
construction1 such as the ,red ,rover1  
,herne1 ,queen1 and  ,prince of ,wales1 
the coefficient appears to be about     
#beej2 but in these  vessels there is a 
still greater excess of the actual over 
the nominal  power than in the case of  
the vessels previously enumerated1 and  
the  increase in the coefficient is     
consequent upon the increased pressure  
of  the steam in the boiler1 as well as 
the superior form of the ship4 ,the     
nominal power of the ,red ,rover1       
,herne1 and ,city of ,canterbury is1 in 
each  case1 #abj horses1 but the actual 
power of the ,red ,rover is #bid1 of the
  ,herne #ced1 and of the ,city of      
,canterbury #cjf1 and in some vessels   
the  excess is still greater2 so that   
with such variations it becomes         
necessary  to adopt a coefficient       
derived from the introduction of the    
actual instead  of the nominal power4   

#edg4 ,q4--,what will be the average    
difference between the nominal and      
actual powers in the several classes of 
vessels you have mentioned and the      
respective coefficients when corrected  
for the actual power8    ,a4--,in the   
first class of vessels experimented     
upon1 the actual power  was about #a4f  
times greater  than the nominal power2  
in the second class1 #a4fg times        
greater2 in the  third class1 #a4g times
  greater2 and in the fourth1 #a4if     
times greater2 while in such vessels as 
the ,red ,rover and ,city of            
,canterbury1 it is #b4fe times greater2 
so that if we adopt the actual  instead 
of the nominal power in  fixing the     
coefficients1 we shall have #eed as the 
first coefficient1 #fid  as the second1 
#hcb for the  third1 and #hjf for the   
fourth1 instead of #ibe1 #aafj1 #adcj1  
and #aehj as  previously specified2     
while  for such vessels as the ,red     
,rover1 ,herne1 ,queen1 and ,prince of  
,wales1 we  shall have #ifb instead of  

#beej4 ,these smaller coefficients1     
then1 express the relative merits of    
the different vessels without  reference
 to any difference of efficacy in the   
engines1 and it appears  preferable1    
with such a  variable excess of the     
actual over the nominal power1 to employ
 them  instead of those first referred  
to4 ,from the circumstance of the third 
of the new coefficients being  greater  
than the fourth1 it  appears that the   
superior result in the fourth set of    
experiments arose  altogether from a    
greater  excess of the actual over the  
nominal power4    #edh4 ,q4--,these     
experiments1 you have already stated1   
were all made on  paddle vessels4 ,have 
similar coefficients of performance been
 obtained in  the case of screw vessels8
    ,a4--,the coefficients of a greater 
number of screw vessels have been       
obtained and recorded1 but it would     
occupy too much time to enumerate them  
here4 ,the coefficient of performance of
 the ,fairy is #dfd4h2 of the ,rattler  

#fgf4h2 and of the ,frankfort #gib4c4   
,this coefficient1 however1 refers to   
nautical and not to statute miles4 ,if  
reduced to statute miles for the        
purpose of comparison with the previous 
experiments1 the coefficients will      
respectively become #gjc1 #ajcc1 and    
#abab2 which indicate that the          
performance of screw vessels is equal to
 the performance of paddle vessels1  but
 some of the superiority of the result  
may be imputed to the superior  size of 
the screw vessels4        ,,influence   
,,of ,,the ,,size ,,of ,,vessels ,,upon 
,,their ,,speed4    #edi4 ,q4--,will    
large vessels attain a greater speed    
than small1 supposing  each to be       
furnished with the same proportionate   
power8    ,a4--,it is well known that   
large vessels furnished with the same   
proportionate power1 will attain a      
greater speed than small vessels1 as    
appears from the rule usual in yacht    
races of allowing a certain part of  the
 distance to be run to vessels which are

 of inferior size4 ,the velocity        
attained by a large vessel will be      
greater than the velocity attained by a 
small vessel of the same mould and the  
same proportionate power1 in the        
proportion of the square roots of the   
linear dimensions of the vessels4 ,a    
vessel therefore with four times the    
sectional area and four times the  power
 of a smaller symmetrical vessel1 and   
consequently of twice the  length1 will 
have its speed increased in the         
proportion of the square root  of #a to 
the square root of #b1 or #a4d times4   
#eej4 ,q4--,will you further illustrate 
this doctrine by an example8            
,a4--,the screw steamer ,fairy1 if      
enlarged to three times the size while  
retaining the same form1 would have     
twenty-seven times the capacity1 nine   
times the sectional area1 and nine times
 the power4 ,the length of such a       
vessel would be #dcd feet2 her breadth  
#fc feet #d-a_/b inches2 her draught of 
water #af-a_/b feet2 her area of        

immersed section #gbi square feet2 and  
her  nominal power #ajhj horses4 ,now as
 the lengths of the ,fairy and of the   
new  vessel are in the proportion of #a 
to #c1 the speeds will be in the        
proportion of the square root of #a to  
the square root of #c2 or1 in other     
words1 the speed of the large vessel    
will be #a4gc times greater than the    
speed of the small vessel4 ,if therefore
 the speed of the ,fairy be #ac knots1  
the speed of the new vessel will be     
#bb4di knots1 although the proportion of
  power to sectional area1 which is     
supposed to be the measure of the       
resistance1 is in both cases precisely  
the same4 ,if the speed of the ,fairy   
herself had to be increased to #bb4bi   
knots1 the power would have to be       
increased in the proportion of the cube 
of #ac to the cube of #bb4di1 or #e4b   
times1 which makes the power necessary  
to propel the ,fairy at that speed      
equal to #fbd nominal horses power4     
,,structure ,,and ,,operation ,,of      

,,paddle ,,wheels4    #eea4 ,q4--,will  
you describe the configuration and mode 
of action of the  paddle wheels in      
general use8    ,a4--,there are two     
kinds of paddle wheels in extensive use1
 the one being  the ordinary radial     
wheel1 in which the floats are fixed on 
arms radiating  from the centre2 and the
 other the feathering wheel1 in which   
each float is  hung upon a centre1 and  
is so governed by suitable mechanism as 
to be  always kept in nearly the        
vertical position4 ,in the radial wheel 
there is  some loss of power from       
oblique action1 whereas in the          
feathering wheel  there is little or no 
loss from this cause2 but in every kind 
of paddle  there is a loss of power from
 the recession of the water from the    
float  boards1 or the slip as it is     
commonly called2 and this loss is the   
necessary condition of the resistance   
for the propulsion of the vessel  being 
created in a fluid4 ,the slip is        
expressed by the difference between  the

 speed of the wheel and the speed of the
 vessel1 and the larger this  difference
 is the greater the loss of power from  
slip must be--the  consumption of steam 
in the engine being proportionate to the
 velocity of  the wheel1 and the useful 
effect being proportionate to the speed 
of the  ship4    #eeb4 ,q4--,the        
resistance necessary for propulsion will
 not be situated at  the circumference  
of the wheel8    ,a4--,in the feathering
 wheel1 where every part of any one     
immerged float  moves forward with the  
same horizontal velocity1 the pressure  
or resistance  may be supposed to be    
concentrated in the centre of the float2
 whereas1 in  the common radial wheel   
this cannot be the case1 for as the     
outer edge of  the float moves more     
rapidly than the edge nearest the centre
 of the wheel1  the outer part of the   
float is the most effectual in          
propulsion4 ,the point  at which the    
outer and inner portions of the float   
just balance one another  in propelling 

effect1 is called the centre of         
pressure2 and if all the  resistances   
were concentrated in this point1 they   
would have the same  effect as before in
 resisting the rotation of the wheel4   
,the resistance  upon any one moving    
float board totally immersed in the     
water will1 when  the vessel is at rest1
 obviously vary as the square of its    
distance from  the centre of motion--the
 resistance of a fluid varying with the 
square of  the velocity2 but1 except    
when the wheel is sunk to the axle or   
altogether  immersed in the water1 it is
 impossible1 under ordinary             
circumstances1 for  one float to be     
totally immersed without others being   
immersed partially1  whereby the arc    
described by the extremity of the paddle
 arm will become  greater than the arc  
described by the inner edge of the      
float2 and  consequently the resistance 
upon any part of the float will increase
 in a  higher ratio than the square of  
its distance from the centre of         

motion--the  position of the centre of  
pressure being at the same time         
correspondingly  affected4 ,in the      
feathering wheel the position of the    
centre of pressure of  the entering and 
emerging floats is continually changing 
from the lower  edge of the float--where
 it is when the float is entering or    
leaving the  water--to the centre of the
 float1 which is its position when the  
float is  wholly immerged2 but in the   
radial wheel the centre of pressure can 
never  rise so high as the centre of the
 float4    #eec4 ,q4--,all this relates 
to the action of the paddle when the    
vessel is  at rest3 will you explain its
 action when the vessel is in motion8   
,a4--,when the wheel of a coach rolls   
along the ground1 any point of its      
periphery describes in the air a curve  
which is termed a cycloid2 any point    
within the periphery traces a prolate or
 protracted cycloid1 and any point      
exterior to the periphery traces a      
curtate or contracted cycloid--the      

prolate cycloid partaking more of the   
nature of a straight line1 and the      
curtate cycloid more of the nature of a 
circle4 ,the action of a paddle  wheel  
in the water resembles in this respect  
that of the wheel of a  carriage running
 along the ground3 that point in the    
radius of the paddle  of which the      
rotative speed is just equal to the     
velocity of the vessel  will describe a 
cycloid2 points nearer the centre1      
prolate cycloids1 and  points further   
from the centre1 curtate cycloids4 ,the 
circle described by  the point whose    
velocity equals the velocity of the     
ship1 is called the  rolling circle1 and
 the resistance due to the difference of
 velocity of  the rolling circle and    
centre of pressure is that which        
operates in the  propulsion of the      
vessel4 ,the resistance upon any part of
 the float1  therefore1 will vary as the
 square of its distance from the rolling
 circle1  supposing the float to be     
totally immerged2 but1 taking into      

account the  greater length of time     
during which the extremity of the paddle
 acts1  whereby the resistance will be  
made greater1 we shall not err far in   
estimating the resistance upon any point
 at the third power of its distance     
from the rolling circle in the case of  
light immersions1 and the #b4e power  in
 the case of deep immersions4    #eed4  
,q4--,how is the position of the centre 
of pressure to be determined8           
,a4--,with the foregoing assumption1    
which accords sufficiently with         
experiment to justify its acceptation1  
the position of the centre of  pressure 
may be found by the following           
rule3--from the radius of the wheel     
substract the radius of the rolling     
circle2 to the remainder add the depth  
of the paddle board1 and divide the     
fourth power of the sum by four times   
the depth2 from the cube root of the    
quotient subtract the difference        
between the radii of the wheel and      
rolling circle1 and the remainder will  

be the distance of the centre of        
pressure from the upper edge of the     
paddle4    #eee4 ,q4--,how do you find  
the diameter of the rolling circle8     
,a4--,the diameter of the rolling circle
 is very easily found1 for we have  only
 to divide #e1bhj times the number of   
miles per hour1 by #fj times the  number
 of strokes per minute1 to get an       
expression for the circumference of  the
 rolling circle1 or the following rule  
may be adopted3--divide #hh times  the  
speed of the vessel in statute miles per
 hour1 by #c4adaf times the  number of  
strokes per minute2 the quotient will be
 the diameter in feet of  the rolling   
circle4 ,the diameter of the circle in  
which the centre of  pressure moves or  
the effective diameter of the wheel     
being known1 and also  the diameter of  
the rolling circle1 we at once find the 
excess of the  velocity of the wheel    
over the vessel4    #eef4 ,q4--,will you
 illustrate these rules by an example8  
,a4--,a steam vessel of moderately good 

shape1 and with engines of #bjj  horses 
power1 realises1 with #bb strokes per   
minute1 a speed of #aj4fb miles  per    
hour4 ,to find the diameter of the      
rolling circle1 we have #hh times       
#aj4fb1 equal to #icd4ff1 and #bb times 
#c4adaf1 equal to #fi4aaeb2 then #icd4ff
  divided by #fi4aaeb is equal to #ac4eb
 feet1 which is the diameter of the     
rolling circle4 ,the diameter of the    
wheel is #ai ft4 #d in41 so that the    
diameter of the rolling circle is about 
#b_/c;ds of the diameter of the wheel1  
and this is a frequent proportion4 ,the 
depth of the paddle board is #b feet1   
and the difference between the diameters
 of the wheel and rolling circle  will  
be #e4hacc1 which will make the         
difference of their radii #b4ijfg2 and  
adding to this the depth of the paddle  
board1 we have #d4ijfg1 the fourth      
power of which is #egi4fd1 which1       
divided by four times the depth of the  
paddle board1 gives us #gb4dee1 the cube
 root of which is #d4afhi1 which1       

diminished by the difference of the     
radii of the wheel and rolling circle1  
leaves #a4bfbb feet for the distance of 
the centre of pressure from the  upper  
edge of the paddle board in the case of 
light immersions4 ,the radius  of the   
wheel being #i4fffg1 the distance from  
the centre of the wheel to the  upper   
edge of the float is #g4fffg1 and adding
 to this #a4bfbb1 we get #h4ibii  feet  
as the radius1 or #ag4heih feet as the  
diameter of the circle in which  the    
centre of pressure revolves4 ,with #bb  
strokes per minute1 the velocity  of the
 centre of pressure will be #bj4egc feet
 per second1 and with #aj4fb  miles per 
hour for the speed of the vessel1 the   
velocity of the rolling  circle will be 
#ae4egf feet per second4 ,the effective 
velocity will be the  difference between
 these quantities1 or #d4iig feet per   
second4 ,now the  height from which a   
body must fall by gravity1 to acquire a 
velocity of  #d4iig feet per second1 is 
about 4#fb feet2 and twice this height1 

or #a4bd  feet1 multiplied by #fb-a_/b1 
which is the number of ,lbs4 weight in a
 cubic  foot of water1 gives #gg-a_/b   
,lbs4 as the pressure on each square    
foot of the  vertical paddle boards4 ,as
 each board is of #bj square feet of    
area1 and  there is a vertical board on 
each side of the ship1 the total        
pressure on  the vertical paddle boards 
will be #bijj ,lbs4    #eeg4 ,q4--,what 
pressure is this equivalent to on each  
square inch of the  pistons8    ,a4--,a 
vessel of #bjj horses power will have   
two cylinders1 each #ej inches          
diameter1 and #e feet stroke1 or        
thereabout4 ,the area of a piston of #ej
  inches diameter is #aifc4e square     
inches1 so that the area of the two     
pistons is #cibg square inches1 and the 
piston will move through #aj feet  every
 revolution2 and with #bb strokes per   
minute this will be #bbj feet per       
minute1 or #c4ff feet per second4 ,now1 
if the effective velocity of the  centre
 of pressure and the velocity of the    

pistons had been the same1 then  a      
pressure of #bijj ,lbs4 upon the        
vertical paddles would have been        
balanced  by an equal pressure on the   
pistons1 which would have been in this  
case  about 4#ge ,lbs4 per square inch2 
but as the effective velocity of the    
centre  of pressure is #d4iig feet per  
second1 while that of the pistons is    
only  #c4ff feet per second1 the        
pressure must be increased in the       
proportion of  #d4iig to #c4ff to       
establish an equilibrium of pressure1   
or1 in other words1  it must be #a4jb   
,lbs4 per square inch4 ,it follows from 
this investigation1  that1 in radial    
wheels1 the greater part of the engine  
power is distributed  among the oblique 
floats4    #eeh4 ,q4--,how comes this to
 be the case8    ,a4--,to understand how
 it happens that more power is expended 
upon the  oblique than upon the vertical
 floats1 it is necessary to remember    
that the  only resistance upon the      
vertical paddle is that due to the      

difference of  velocity of the wheel and
 the ship2 but if the wheel be supposed 
to be  immersed to its axle1 so that the
 entering float strikes the water       
horizontally1 it is clear that the      
resistance on such float is that due to 
the whole velocity of rotation2 and that
 the resistance to the entering  float  
will be the same whether the vessel is  
in motion or not4 ,the  resistance      
opposed to the rotation of any float    
increases from the position  of the     
vertical float-where the resistance is  
that due to the difference of  velocity 
of the wheel and vessel--until it       
reaches the plane of the axis1          
supposing the wheel to be immersed so   
far1 where the resistance is that due   
to the whole velocity of rotation2 and  
although in any oblique float the  total
 resistance cannot be considered        
operative in a horizontal direction1    
yet the total resistance increases so   
rapidly on each side of the vertical    
float1 that the portion of it which is  

operative in the horizontal  direction1 
is in all ordinary cases of immersion   
very considerable4 ,in the  feathering  
wheel1 where there is little of this    
oblique action1 the  resistance will be 
in the proportion of the square of the  
horizontal  velocities of the several   
floats1 which may be represented by the 
horizontal distances between them2 and  
in the feathering wheel1 the  vertical  
float having the greatest horizontal    
velocity will have the  greatest        
propelling effect4    #eei4 ,q4--,should
 the floats in feathering wheels enter  
and leave the water  vertically8        
,a4--,the floats should be so governed  
by the central crank or eccentric1  that
 the entering and emerging floats have a
 direction intermediate between  a      
radius and a vertical line4    #efj4    
,q4--,can you give any practical rules  
for proportioning paddle  wheels8       
,a4--,a common rule for the pitch of the
 floats is to allow one float for  every
 foot of diameter of the wheel2 but in  

the case of fast vessels a  pitch of    
#b-a_/b feet1 or even less1 appears     
preferable1 as a close pitch  occasions 
less vibration4 ,if the floats be put   
too close1 however1 the  water will not 
escape freely from between them1 and if 
set too far apart  the stroke of the    
entering paddle will occasion an        
inconvenient amount of  vibratory       
motion1 and there will also be some loss
 of power4 ,to find the  proper area of 
a single float3--divide the number of   
actual horses power of  both engines by 
the diameter of the wheel in feet2 the  
quotient is the area  of one paddle     
board in square feet proper for sea     
going vessels1 and the  area multiplied 
by #j4f will give the length of the     
float in feet4 ,in very  sharp vessels1 
which offer less resistance in passing  
through the water1  the area of paddle  
board is usually one-fourth less than   
the above  proportion1 and the proper   
length of the float may in such case be 
found by  multiplying the area by #j4g4 

,in sea going vessels about four floats 
are  usually immersed1 and in river     
steamers only one or two floats4 ,there 
is  more slip in the latter case1 but   
there is also more engine power exerted 
in the propulsion of the ship1 from the 
greater speed of engine thus  rendered  
possible4    #efa4 ,q4--,then is it     
beneficial to use small floats8         
,a4--,quite the contrary4 ,if to permit 
a greater speed of the engine the       
floats be diminished in area instead of 
being raised out of the water1 no       
appreciable accession to the speed of   
the vessel will be obtained2 whereas    
there will be an increased speed of     
vessel if the accelerated speed of the  
engine be caused by diminishing the     
diameter of the wheels4 ,in vessels     
intended to be fast1 therefore1 it is   
expedient to make the wheels small1  so 
as to enable the engine to work with a  
high velocity2 and it is  expedient to  
make such wheels of the feathering kind1
 to obviate loss of  power from oblique 

action4 ,in no wheel must the rolling   
circle fall below  the water line1 else 
the entering and emerging floats will   
carry masses of  water before them4 ,the
 slip is usually equal to about         
one-fourth of the  velocity of the      
centre of pressure in well proportioned 
wheels2 but it is  desirable to have the
 slip as small as is possible           
consistently with the  observance of    
other necessary conditions4 ,the speed  
of the engine and also  the speed of the
 vessel being fixed1 the diameter of the
 rolling circle  becomes at once        
ascertainable1 and adding to this the   
slip1 we have the  diameter of the      
wheel4        ,,configuration ,,and     
,,action ,,of ,,the ,,screw4    #efb4   
,q4--,will you describe more in detail  
than you have yet done1 the             
configuration and mode of action of the 
screw propeller8    ,a4--,the ordinary  
form of screw propeller is represented  
in figs4 #df and  #dg2 fig4 #df being a 
perspective view1 and fig4 #dg an end   

view1 or view such  as is seen when     
looking upon the end of the shaft4 ,the 
screw here  represented is one with two 
arms or blades4 ,some screws have three 
arms1  some four and some six2 but the  
screw with two arms is the most usual1  
and  screws with more than three arms   
are not now much employed in this       
country4  ,the screw on being put into  
revolution by the engine1 preserves a   
spiral  path in the water1 in which it  
draws itself forward in the same way as 
a  screw nail does when turned round in 
a piece of wood1 whereas the paddle     
wheel more resembles the action of a cog
 wheel working in a rack4               
,illustration3 ,fig4 #df4 ,fig4 #dg4    
,,ordinary ,,form ,,of ,,screw          
,,propeller4    #efc4 ,q4--,but the     
screw of a steam vessel has no          
resemblance to a screw  nail8           
,a4--,it has in fact a very close       
resemblance if you suppose only a very  
short piece of the screw nail to be     
employed1 and if you suppose1 moreover1 

the thread of the screw to be cut nearly
 into the centre to prevent the  wood   
from stripping4 ,the original screw     
propellers were made with several       
convolutions of screw1 but it was found 
advantageous to shorten them1 until     
they are now only made one-sixth of a   
convolution in length4    #efd4         
,q4--,and the pitch you have already    
explained to be the distance in  the    
line of the shaft from one convolution  
to the next1 supposing the screw  to    
consist of two or more convolutions8    
,a4--,yes1 that is what is meant by the 
pitch4 ,if a thread be wound upon a     
cylinder with an equal distance between 
the convolutions1 it will trace a  screw
 of a uniform pitch2 and if the thread  
be wound upon the cylinder with  an     
increasing distance between each        
convolution1 it will trace a screw of   
an increasing pitch4 ,but two or more   
threads may be wound upon the cylinder  
at the same time1 instead of a single   
thread4 ,if two threads be wound upon   

it they will trace a double-threaded    
screw2 if three threads be wound upon   
it they will trace a treble-threaded    
screw2 and so of any other number4 ,now 
if the thread be supposed to be raised  
up into a very deep and thin spiral     
feather1 and the cylinder be supposed to
 become very small1 like the newel  of a
 spiral stair1 then a screw will be     
obtained of the kind proper for         
propelling vessels1 except that only a  
very short piece of such screw must  be 
employed4 ,whatever be the number of    
threads wound upon a cylinder1 if  the  
cylinder be cut across all the threads  
will be cut4 ,a slice cut out of  the   
cylinder will therefore contain a piece 
of each thread4 ,but the  threads1 in   
the case of a screw propeller1 answer to
 the arms1 so that in  every screw      
propeller the number of threads entering
 into the composition  of the screw will
 be the same as the number of arms4 ,an 
ordinary screw with  two blades is a    
short piece of a screw of two threads4  

#efe4 ,q4--,in what part of the ship is 
the screw usually placed8               
,illustration3 ,fig4 #dh    ,a4--,in    
that part of the run of the ship called 
the dead wood1 which is a  thin and     
unused part of the vessel just in       
advance of the rudder4 ,the usual       
arrangement is shown in fig4 #dh1 which 
represents the application to a  vessel 
of a species of screw which has the arms
 bent backwards1 to  counteract the     
centrifugal motion given to the water   
when there is a  considerable amount of 
slip4    #eff4 ,q4--,how is the slip in 
a screw vessel determined8    ,a4--,by  
comparing the actual speed of the vessel
 with the speed due to the  pitch and   
number of revolutions of the screw1 or1 
what is the same thing1  the speed which
 the vessel would attain if the screw   
worked in a solid nut4  ,the difference 
between the actual speed and this       
hypothetical speed1 is the  slip4       
#efg4 ,q4--,in well formed screw        
propellers what is the amount of slip   

found  to be8    ,a4--,if the screw be  
properly proportioned to the resistance 
that the  vessel has to overcome1 the   
slip will not be more than #aj per      
cent41 but in  some cases it amounts to 
#cj per cent41 or even more than this4  
,in other  cases1 however1 the slip is  
nothing at all1 and even less than      
nothing2 or1  in other words the vessel 
passes through the water with a greater 
velocity  than if the screw were working
 in a solid nut4    #efh4 ,q4--,then it 
must be by the aid of the wind or some  
other extraneous  force8    ,a4--,no2 by
 the action of the screw alone4    #efi4
 ,q4--,but how is such a result         
possible8    ,a4--,it appears to be     
mainly owing to the centrifugal action  
of the screw1  which interposes a film  
or wedge of water between the screw     
itself and the  water on which the screw
 reacts4 ,this negative slip1 as it is  
called1  chiefly occurs when the pitch  
of the screw is less than its diameter1 
and  when1 consequently1 the velocity of

 rotation is greater than if a coarser  
pitch had been employed4 ,there is1     
moreover1 in all vessels passing through
  the water with any considerable       
velocity1 a current of water following  
the  vessel1 in which current1 in the   
case of a screw vessel1 the screw will  
revolve2 and in certain cases the       
phenomenon of negative slip may be      
imputable in part to the existence of   
this current4    #egj4 ,q4--,is the     
screw propeller as effectual an         
instrument of propulsion  as the radial 
or feathering paddle8    ,a4--,in all   
cases of deep immersion it appears to be
 quite as effectual as  the radial      
paddle1 indeed1 more so2 but it is      
scarcely as effectual as the  feathering
 paddle1 with any amount of immersion1  
and scarcely as effectual  as the common
 paddle in the case of light immersions4
        ,,comparative ,,advantages ,,of 
,,paddle ,,and ,,screw ,,vessels4       
#ega4 ,q4--,whether do you consider     
paddle or screw vessels to be on the    

whole the most advantageous8            
,a4--,that is a large question1 and can 
only receive a qualified answer4 ,in    
some cases the use of paddles is        
indispensable1 as1 for example1 in the  
case of river vessels of a limited      
draught of water1 where it would not be 
possible to get sufficient depth below  
the water surface to enable a screw  of 
a proper diameter to be got in4    #egb4
 ,q4--,but how does the matter stand in 
the case of ocean vessels8    ,a4--,in  
the case of ocean vessels1 it is found  
that paddle vessels fitted  with the    
ordinary radial wheels1 and screw       
vessels fitted with the ordinary  screw1
 are about equally efficient in calms   
and in fair or beam winds with  light   
and medium immersions4 ,if the vessels  
are loaded deeply1 however1 as  vessels 
starting on a long voyage and carrying  
much coal must almost  necessarily be1  
then the screw has an advantage1 since  
the screw acts in  its best manner when 
deeply immersed1 and the paddles in     

their worst4 ,when  a screw and paddle  
vessel1 however1 of the same model and  
power are set to  encounter head winds1 
the paddle vessel it is found has in all
 cases an  advantage1 not in speed1 but 
in economy of fuel4 ,for whereas in a   
paddle  vessel1 when her progress is    
resisted1 the speed of the engine       
diminishes  nearly in the proportion of 
the diminished speed of ship1 it happens
 that  in a screw vessel this is not    
so1--at least to an equal extent1--but  
the  engines work with nearly the same  
rate of speed as if no increase of      
resistance had been encountered by the  
ship4 ,it follows from this             
circumstance1 that whereas in paddle    
vessels the consumption of steam1 and   
therefore of fuel1 per hour is          
materially diminished when head winds   
occur1  in screw vessels a similar      
diminution in the consumption of steam  
and fuel  does not take place4    #egc4 
,q4--,but perhaps under such            
circumstances the speed of the screw    

vessel will be the greater of the two8  
,a4--,no2 the speed of the two vessels  
will be the same1 unless the  strength  
of the head wind be so great as to bring
 the vessels nearly to a  state of rest1
 and on that supposition the screw      
vessel will have the  advantage4 ,such  
cases occur very rarely in practice2 and
 in the case of the  ordinary           
resistances imposed by head winds1 the  
speed of the screw and  paddle vessel   
will be the same1 but the screw vessel  
will consume most  coals4    #egd4      
,q4--,what is the cause of this         
peculiarity8    ,a4--,the cause is1 that
 when the screw is so proportioned in   
its length as  to be most suitable for  
propelling vessels in calms1 it is too  
short to be  suitable for propelling    
vessels which encounter a very heavy    
resistance4 ,it  follows1 therefore1    
that if it is prevented from pursuing   
its spiral course  in the water1 it will
 displace the water to a certain extent 
laterally1 in  the manner it does if the

 engine be set on when the vessel is at 
anchor2  and a part of the engine power 
is thus wasted in producing a useless   
disturbance of the water1 which in      
paddle vessels is not expended at all4  
#ege4 ,q4--,if a screw and paddle vessel
 of the same mould and power be tied    
stern to stern1 will not the screw      
vessel preponderate and tow the paddle  
vessel astern against the whole force of
 her engines8    ,a4--,yes1 that will be
 so4    #egf4 ,q4--,and seeing that the 
vessels are of the same mould and power1
 so  that neither can derive an         
advantage from a variation in that      
condition1  does not the preponderance  
of the screw vessel show that the screw 
must be  the most powerful propeller8   
,a4---,no1 it does not4    #egg4        
,q4--,seeing that the vessels are the   
same in all respects except as  regards 
the propellers1 and that one of them    
exhibits a superiority1 does  not this  
circumstance show that one propeller    
must be more powerful than  the other8  

,a4--,that does not follow necessarily1 
nor is it the fact in this  particular  
case4 ,all steam vessels when set into  
motion1 will force  themselves forward  
with an amount of thrust which1 setting 
aside the loss  from friction and from  
other causes1 will just balance the     
pressure on the  pistons4 ,in a paddle  
vessel1 as has already been explained1  
it is easy to  tell the tractive force  
exerted at the centre of pressure of the
 paddle  wheels1 when the pressure      
urging the pistons1 the dimensions of   
the wheels  and the speed of the vessel 
are known2 and that force1 whatever be  
its  amount1 must always continue the   
same with any constant pressure on the  
pistons4 ,in a screw vessel the same law
 applies1 so that with any given        
pressure on the pistons and discarding  
the consideration of friction1 it  will 
follow that whatever be the thrust      
exerted by a paddle or a screw  vessel1 
it must remain uniform whether the      
vessel is in motion or at rest1  and    

whether moving at a high or a low       
velocity through the water4 ,now to     
achieve an equal speed during calms in  
two vessels of the same model1 there    
must be the same amount of propelling   
thrust in each2 and this thrust1        
whatever be its amount1 cannot afterward
 vary if a uniform pressure of  steam be
 maintained4 ,the thrusts1 therefore1   
caused by their respective  propelling  
instruments1 when a screw and paddle    
vessel are tied stern to  stern1 must be
 the same as at other times2 and as at  
other times those  thrusts are equal1 so
 must they be when the vessels are set  
in the  antagonism supposed4    #egh4   
,q4--,how comes it then that the screw  
vessel preponderates8    ,a4--,not by   
virtue of a larger thrust exerted by the
 screw in pressing  forward the shaft   
and with it the vessel1 but by the      
gravitation against  the stern of the   
wave of water which the screw raises by 
its rapid  rotation4 ,this wave will    
only be raised very high when the       

progress of the  vessel through the     
water is nearly arrested1 at which time 
the centrifugal  action of the screw is 
very great2 and the vessel under such   
circumstances  is forced forward partly 
by the thrust of the screw1 and partly  
by the  hydrostatic pressure of the     
protuberance of water which the         
centrifugal  action of the screw raises 
up at the stern4    #egi4 ,q4--,can you 
state any facts in corroboration of this
 view8    ,a4--,the screw vessel will   
not preponderate if a screw and paddle  
vessel  be tied bow to bow and the      
engines of each be then reversed4 ,in1  
some screw  vessels the amount of thrust
 actually exerted by the screw under all
 its  varying circumstances1 has been   
ascertained by the application of a     
dynamometer to the end of the shaft4 ,by
 this instrument--which is formed by  a 
combination of levers like a weighing   
machine for carts--a thrust or  pressure
 of several tons can be measured by the 
application of a small  weight2 and it  

has been found1 by repeated experiment  
with the dynamometer1  that the thrust  
of the screw in a screw vessel when     
towing a paddle vessel  against the     
whole force of her engines1 is just the 
same as it is when the  two vessels are 
maintaining an equal speed in calms4    
,the preponderance of  the screw vessel 
must1 therefore1 be imputable to some   
other agency than to  a superior thrust 
of the screw1 which is found by         
experiment not to exist4    #ehj4       
,q4--,has the dynamometer been applied  
to paddle vessels8    ,a4--,it has not  
been applied to the vessels themselves1 
as in the case of  screw vessels1 but it
 has been employed on shore to ascertain
 the amount of  tractive force that a   
paddle vessel can exert on a rope4      
#eha4 ,q4--,have any experiments been   
made to determine the comparative       
performances of screw and paddle vessels
 at sea8    ,a4--,yes1 numerous         
experiments2 of which the best known are
 probably those  made on the screw      

steamer ,rattler and the paddle steamer 
,alecto1 each  vessel of the same model1
 size1 and power1--each vessel being of 
about #hjj  tons burden and #bjj horses 
power4 ,subsequently another set of     
experiments  with the same object was   
made with the ,niger screw steamer and  
the ,basilisk  paddle steamer1 both     
vessels being of about #ajjj tons burden
 and #djj horses  power4 ,the general   
results which were obtained in the      
course of these  experiments are those  
which have been already recited4        
#ehb4 ,q4--,will you recapitulate some  
of the main incidents of these  trials8 
,a4--,i may first state some of the     
chief dimensions of the vessels4 ,the   
,rattler is #agf feet #f inches long1   
#cb feet #h-a_/b inches broad1 #hhh tons
  burden1 #bjj horses power1 and has an 
area of immersed midship section of     
#chj square feet at a draught of water  
of #aa feet #e-a_/b inches4 ,the ,alecto
  is of the same dimensions in every    
respect1 except that she is only of #hjj

  tons burden1 the difference in this   
particular being wholly owing to the    
,rattler having been drawn out about #ae
 feet at the stern1 to leave abundant   
room for the application of the screw4  
,the ,rattler was fitted with a         
dynamometer1 which enabled the actual   
propelling thrust of the screw shaft  to
 be measured2 and the amount of this    
thrust1 multiplied by the distance      
through which the vessel passed in a    
given time1 would determine the amount  
of power actually utilized in propelling
 the ship4 ,both vessels were fitted    
with indicators applied to the          
cylinders1 so as to determine the amount
 of  power exerted by the engines4      
#ehc4 ,q4--,how many trials of the      
vessels were made on this occasion8     
,a4--,twelve trials in all2 but ,i need 
not refer to those in which similar  or 
identical results were only repeated4   
,the first trial was made under  steam  
only1 the weather was calm and the water
 smooth4 ,at #ed minutes past #d  in the

 morning both vessels left the ,nore1   
and at #cj-a_/b minutes past #b the     
,rattler stopped her engines in         
,yarmouth ,roads1 where in #bj-a_/b     
minutes  afterward she was joined by the
 ,alecto4 ,the mean speed achieved by   
the  ,rattler during this trial was #i4b
 knots per hour2 the mean speed of the  
,alecto was #h4h knots per hour4 ,the   
slip of the screw was #aj4b per cent4   
,the  actual power exerted by the       
engines1 as shown by the indicator1 was 
in the  case of the ,rattler #ccd4f     
horses1 and in the case of the ,alecto  
#bha4b  horses2 being a difference of   
#ec4d horses in favor of the ,rattler4  
,the  forward thrust upon the screw     
shaft was #c tons1 #ag cwt41 #c qrs41   
and #ad  lbs4 ,the horse power of the   
shaft--or power actually                
utilized--ascertained  by multiplying   
the thrust in pounds by the space passed
 through by the  vessel in feet per     
minute1 and dividing by #cc1jjj1 was    
#bdg4h horses power4  ,this makes the   

ratio of the shaft to the engine power  
as #a to #a4c1 or1 in  other words1 it  
shows that the amount of engine power   
utilized in  propulsion was #gg per     
cent4 ,in a subsequent trial made with  
the vessels  running before the wind1   
but with no sails set and the masts     
struck1 the  speed realized by the      
,rattler was #aj knots per hour4 ,the   
slip of the screw  was #aa4b per cent4  
,the actual power exerted by the engines
 of the ,rattler  was #cfh4h horses4    
,the actual power exerted by the engines
 of the ,alecto was  #bia4g horses4 ,the
 thrust of the shaft was equal to a     
weight of #d tons1 #d  cwt41 #a qr41 #a 
lb4 ,the horse power of the shaft was   
#bij4b horses1 and the  ratio of the    
shaft to the engine power was #a to     
#a4b4 ,here1 therefore1 the  amount of  
the engine power utilized was #hd per   
cent4    #ehd4 ,q4--,if in any screw    
vessel the power of the engine be       
diminished by  shutting off the steam or
 otherwise1 you will then have a larger 

screw  relatively with the power of the 
engine than before8    ,a4--,yes4       
#ehe4 ,q4--,was any experiment made to  
ascertain the effect of this            
modification8    ,a4--,there was2 but   
the result was not found to be better   
than before4 ,the  experiment was made  
by shutting off the steam from the      
engines of the  ,rattler until the      
number of strokes was reduced to #ag in 
the minute4 ,the  actual power was then 
#abf4g horses2 thrust upon the shaft #b 
tons1 #b cwt41 #c  qrs41 #ad lbs2 horse 
power of shaft #hh4d horses2 ratio of   
shaft to engine  power #a to #a4d2 slip 
of the screw #ah4g per cent4 ,in this   
experiment the  power utilized was #ga  
per cent4    #ehf4 ,q4--,was any        
experiment made to determine the        
relative performances  in head winds8   
,a4--,the trial in which this relation  
was best determined lasted for seven    
hours1 and was made against a strong    
head wind and heavy head sea4 ,the      
speed of the ,rattler by patent log was 

#d4b knots2 and at the conclusion of    
the trial the ,alecto had the advantage 
by about half a mile4 ,owing to an      
accidental injury to the indicator1 the 
power exerted by the engines of the     
,rattler in this trial could not be     
ascertained2 but judging from the power 
exerted in other experiments with the   
same number of revolutions1 it  appears 
probable that the power actually exerted
 by the ,rattler was about  #cjj horses4
 ,the number of strokes per minute made 
by the engines of the  ,rattler was #bb1
 whereas in the ,alecto the number of   
strokes per minute was  only #ab2 so    
that while the engines of the ,alecto   
were reduced1 by the  resistance        
occasioned by a strong head wind1 to    
nearly half their usual  speed1 the     
engines of the ,rattler were only       
lessened about one twelfth of  their    
usual speed4 ,the mean thrust upon the  
screw shaft during this  experiment1 was
 #d tons1 #g cwt41 #j qr41 #af lbs4 ,the
 horse power of the shaft  was #abe4i   

horses1 and the slip of the screw was   
#ef per cent4 ,taking the  power        
actually exerted by the ,rattler at #cjj
 horses1 the power utilized in  this    
experiment is only #db per cent4        
#ehg4 ,q4--,what are the dimensions of  
the screw in the ,rattler8              
,a4--,diameter #aj feet1 length #a foot 
#c inches1 pitch #aa feet4 ,the         
foregoing experiments show that with a  
larger screw a better average           
performance would be obtained4 ,the best
 result arrived at1 was when the  vessel
 was somewhat assisted by the wind1     
which is equivalent to a  reduction of  
the resistance of the hull1 or to a     
smaller hull1 which is  only another    
expression for a larger proportionate   
screw4    #ehh4 ,q4--,when you speak of 
a larger screw1 what increase of        
dimension do  you mean to express8      
,a4--,an increase of the diameter4 ,the 
amount of reacting power of the  screw  
upon the water is hot measured by the   
number of square feet of  surface of the

 arms1 but by the area of the disc or   
circle in which the  screw revolves4    
,the diameter of the screw of the       
,rattler being #aj feet1 the  area of   
its disc is #gh4e square feet2 and with 
the amount of thrust already  mentioned 
as existing in the first experiment1    
viz4 #hgbb lbs41 the reacting  pressure 
on each square foot of the screw's disc 
will be #ajh-a_/b lbs4 ,the  immersed   
midship section being #chj square feet1 
this is equivalent to #bc  lbs4 per     
square foot of immersed midship section 
at a speed of #i4b knots  per hour4     
#ehi4 ,q4--,in smaller vessels of       
similar form1 will the resistance per   
square foot of midship section be more  
than this8    ,a4--,it will be          
considerably more4 ,in the ,pelican1 a  
vessel of #aji-c_/d  square feet of     
midship section1 ,i estimate the        
resistance per square foot  of midship  
section at #cj lbs41 when the speed of  
the vessel is #i4g knots  per hour4 ,in 
the ,minx with an immersed midship      

section of #hb square feet1  the        
resistance per square foot of immersed  
midship section was found by the        
dynamometer to be #da lbs4 at a speed of
 #h-a_/b knots2 and in the ,dwarf1 a    
vessel with #fj square feet of midship  
section1 ,i estimate the resistance  per
 square foot of midship section at #df  
lbs4 at a speed of #i knots per  hour1  
which is just double the resistance per 
square foot of the ,rattler4  ,the      
diameter of the screw of the ,minx is   
#d-a_/b feet1 so that the area of  its  
disc is #ae4i square feet1 and the area 
of immersed midship section is  about #e
 times greater than that of the screw's 
disc4 ,the diameter of the  screw of the
 ,dwarf is #e feet #h inches1 so that   
the area of its disc is  #be4bb square  
feet1 and the area of immersed midship  
section is #b4d times  greater than that
 of the screw's disc4 ,the pressure per 
square foot of the  screw's disc is #bad
 lbs4 in the case of the ,minx1 and     
#aji-a_/b lbs4 in the  case of the      

,dwarf4    #eij4 ,q4--,from the greater 
proportionate resistance of small       
vessels1 will  not they require larger  
proportionate screws than large vessels8
    ,a4--,they will4    #eia4 ,q4--,is  
there any ready means of predicting what
 the amount of thrust  of a screw will  
be8    ,a4--,when we know the amount of 
pressure on the pistons1 and the        
velocity  of their motion relatively    
with the velocity of advance made by the
 screw1  supposing it to work in a solid
 nut1 it is easy to tell what the thrust
 of  the screw would be if it were      
cleared of the effects of friction and  
other  irregular sources of disturbance4
 ,the thrust1 in fact1 would be at once 
found by the principle of virtual       
velocities2 and if we take this         
theoretical thrust and diminish it by   
one fourth to compensate for friction   
and lateral slip1 we shall have a near  
approximation to the amount of  thrust  
that will be actually exerted4#a      #a
 ,see ,treatise on the ,screw           

,propeller1 by ,j4 ,bourne1 ,c4 ,e4     
,,comparative ,,advantages ,,of         
,,different ,,screws4    #eib4          
,q4--,what species of screw do you      
consider the best8    ,a4--,in cases in 
which a large diameter of screw can be  
employed1 the  ordinary screw or helix  
with two blades seems to be as effective
 as any  other1 and it is the most      
easily constructed4 ,if1 however1 the   
screw is  restricted in diameter1 or if 
the vessel is required to tow1 or will  
have  to encounter habitually strong    
head winds1 it will be preferable to    
employ  a screw with an increasing      
pitch1 and also of such other           
configuration that  it will recover from
 the water some portion of the power    
that has been  expended in slip4        
#eic4 ,q4--,how can this be done8       
,a4--,there are screws which are        
intended to accomplish1 this object     
already in actual use4 ,when there is   
much slip a centrifugal velocity is     
given to the water1 and the screw1      

indeed1 if the engine be set on when the
  vessel is at rest1 acts very much as a
 centrifugal fan would do if placed  in 
the same situation4 ,the water projected
 outward by the centrifugal force       
escapes in the line of least resistance1
 which is to the surface2 and if  there 
be a high column of water over the      
screw1 or1 in other words1 if the  screw
 is deeply immersed1 then the           
centrifugal action is resisted to a     
greater extent1 and there will be less  
slip produced4 ,the easiest  expedient1 
therefore1 for obviating loss by slip is
 to sink the screw  deeply in the water2
 but as there are obvious limits to the 
application of  this remedy1 the next   
best device is to recover and render    
available for  propulsion some part of  
the power which has been expended in    
giving motion  to the water4 ,one device
 for doing this consists in placing the 
screw well  forward in the dead wood1 so
 that it shall be overhung by the stern 
of the  ship4 ,the water forced upward  

by the centrifugal action of the screw  
will1  by impinging on the overhanging  
stern1 press the vessel forward in the  
water1 just in the same way as is done  
by the wind when acting on an  oblique  
sail4 ,i believe1 the two revolving     
vanes without any twist or  obliquity on
 them at all1 would propel a vessel if  
set well forward in the  dead wood or   
beneath the bottom1 merely by the ascent
 of the water up the  inclined plane of 
the vessel's run2 and1 at all events1 a 
screw so placed  would1 in my judgment1 
aid materially in propelling the vessel 
when her  progress was resisted by head 
winds4    #eid4 ,q4--,but you said there
 are some kinds of screws which profess 
to  accomplish this8    ,illustration3  
,fig4 #di4 ,,the ,,earl ,,of            
,,dundonald',s ,,propeller4             
,a4--,there are screws which profess to 
counteract the centrifugal velocity     
given to the water by imparting to it an
 equal centripetal force1 the           
consequence of which will be1 that the  

water projected backward by the  screw1 
instead of taking the form of the       
frustum of a cone1 with its small  end  
next the screw1 will take the form of a 
cylinder4 ,one of these forms of  screw 
is that patented by the ,earl of        
,dundonald in #ahdc1 and which is       
represented in fig4 #di4 ,another is the
 form of screw already represented in   
fig4 #dh1 and which was patented by ,mr4
 ,hodgson in #ahdd4 ,mr4 ,hodgson bends 
the arms of his propellers backward1 not
 into the form of a triangle1 but  into 
the form of a parabola1 to the end that 
the impact of the screw on the          
particles of the water may cause them to
 converge to a focus1 as the rays  of   
light would do in a parabolic reflector4
 ,but this particular  configuration is 
not important1 seeing that the same     
convergence which is  given to the      
particles of the water1 with a screw of 
uniform pitch bent  back into the form  
of a parabola1 will be given with a     
screw bent back into  the form of a     

triangle1 if the pitch be suitably      
varied between the centre  and the      
circumference4    #eie4 ,q4--,then the  
pitch may be varied in two ways8        
,a4--,yes3 a screw may have a pitch     
increasing in the direction of the      
length1 as would happen in the case of a
 spiral stair1 if every successive  step
 in the ascent was thicker than the one 
below it2 or it may increase  from the  
centre to the circumference1 as would   
happen in the case of a  spiral stair1  
if every step were thinner at the centre
 of the lower than at  its outer wall4  
,when the pitch of a screw increases in 
the direction of its  length1 the       
leading edge of the screw enters the    
water without shock or  impact1 as the  
advance of the leading edge per         
revolution will not be  greater than the
 advance of the vessel4 ,when the pitch 
of a screw increases  in the direction  
of its diameter1 the central part of the
 screw will  advance with only the same 
velocity as the water1 so that it cannot

  communicate any centrifugal velocity  
to the water2 and the whole slip1 as    
well as the whole propelling pressure1  
will occur at the outer part of the     
screw blades4    #eif4 ,q4--,is there   
any advantage derived from these forms  
of screws8    ,a4--,there is a slight   
advantage1 but it is so slight as hardly
 to balance  the increased trouble of   
manufacture1 and1 consequently1 they are
 not  generally or widely adopted4      
#eig4 ,q4--,what other kinds of screw   
are there proposing to themselves the   
same or similar objects8    ,a4--,there 
is the corrugated screw1 the arms of    
which are corrugated1 so  as it were to 
gear with the water during its          
revolution1 and thereby  prevent it from
 acquiring a centrifugal velocity4 ,then
 there is ,griffith's  screw1 which has 
a large ball at its centre1 which1 by   
the suction it  creates at its hinder   
part1 in passing through the water1     
produces a  converging force1 which     
partly counteracts the divergent action 

of the  arms4 ,finally1 there is ,holm's
 screw1 which has now been applied to a 
good  number of vessels with success4   
#eih4 ,q4--,will you describe the       
configuration and action of ,holm's     
screw8    ,a4--,first1 then1 the screw  
increases in the direction of its       
length1 and  this increase is very rapid
 at the following edge1 so that1 in     
fact1 the  following edge stands in the 
plane of the shaft1 or in the vertical  
longitudinal plane of the vessel4 ,then 
the ends of the arms are bent over  into
 a curved flange1 the edge of which     
points astern1 and the point where  this
 curved flange joins the following edge 
of the screw is formed1 not  into an    
angle1 but into a portion of a sphere1  
so that this corner  resembles the bowl 
of a spoon4 ,when the screw is put into 
revolution1 the  water is encountered by
 the leading edge of the screw without  
shock1 as its  advance is only equal to 
the advance of the vessel1 and before   
the screw  leaves the water it is       

projected directly astern4 ,at the same 
time1 the  curved flange at the rim of  
the screw prevents the dispersion of the
 water  in a radial direction1 and it   
consequently assumes the form of a      
column or  cylinder of water1 projected 
backward from the ship4    #eii4        
,q4--,what is the nature of ,beattle's  
screw8    ,a4--,beattie's screw is an   
arrangement of the screw propeller      
whereby it  is projected beyond the     
rudder1 and the main object of the      
arrangement is  to take away the        
vibratory motion at the stern1--an      
intention which it  accomplishes in     
practice4 ,there is an oval eye in the  
rudder1 to permit the  screw shaft to   
pass through it4    #fjj4 ,q4--,when the
 diameter of the cylinder of water      
projected backward by  a screw1 and the 
force urging it into motion are known1  
may not the  velocity it will acquire be
 approximately determined8    ,a4--,that
 will not be very difficult2 and ,i will
 take for illustration the  case of the 

,minx1 already referred to1 which will  
show how such a  computation is to be   
conducted4 ,the speed of this vessel1 in
 one of the  experiments made with her1 
was #h4dde knots2 the number of         
revolutions of  the screw per minute1   
#bca4cb2 and the pressure on each square
 foot of area  of the screw's disc1 #bad
 lbs4 ,if a knot be taken to be #fjge4f 
feet1 then  the distance advanced by the
 vessel1 when the speed is #h4dde knots1
 will be  #c4g feet per revolution1 and 
this advance will be made in about 4#bf 
of a  second of time4 ,now the distance 
which a body will fall by gravity1 in   
4#bf  of a second1 is #a4jhg feet2 and a
 weight of #bad lbs4 put into motion by 
gravity1 or by a pressure of #bad lbs41 
would1 therefore1 acquire a velocity  of
 #a4jhg feet during the time one        
revolution of the screw is being        
performed4 ,the weight to be moved1     
however1 is #c4g cubic feet of water1   
that being the new water seized by the  
screw each revolution for every  square 

foot of surface in the screw's disc2 and
 #c4g cubic feet of water  weigh #bca4e 
lbs41 so that the urging force of #bad  
lbs4 is somewhat less  than the force of
 gravity1 and the velocity of motion    
communicated to the  water will be      
somewhat under #a4jhg feet per          
revolution1 or we may say it  will be in
 round numbers #a foot per revolution4  
,this1 added to the progress  of the    
vessel1 will make the distance advanced 
by the screw through the  water #d4g    
feet per revolution1 leaving the        
difference between this and the  pitch1 
namely #a4ac feet1 to be accounted for  
on the supposition that the  screw      
blades had broken laterally through the 
water to that extent4 ,it  would be     
proper to apply some correction to this 
computation1 which would  represent the 
increased resistance due to the         
immersion of the screw in the  water2   
for a column of water cannot be moved in
 the direction of its axis  beneath the 
surface1 without giving motion to the   

superincumbent water1 and  the inertia  
of this superincumbent water must1      
therefore1 be taken into the  account4  
,in the experiment upon the ,minx1 the  
depth of this superincumbent  column was
 but small4 ,the total amount of the    
slip was #cf4ec per cent42 and  there   
will not be much error in setting down  
about one half of this as due  to the   
recession of the water in the direction 
of the vessel's track1 and  the other   
half as due to the lateral penetration  
of the screw blades4    #fja4 ,q4--,is  
it not important to make the stern of   
screw vessels very  fine1 with the view 
of diminishing the slip1 and increasing 
the speed8    ,a4--,it is most          
important4 ,the ,rifleman1 a vessel of  
#dhf tons1 had  originally engines of   
#bjj horses power1 which propelled her  
at a speed of #h  knots an hour4 ,the   
,teazer1 a vessel of #bif tons1 had     
originally engines of  #ajj horses      
power1 which propelled her at a speed of
 #f-a_/b knots an hour4  ,the engines of

 the ,teazer were subsequently          
transferred to the ,rifleman1  and new  
engines of #dj horse power were put into
 the ,teazer4 ,both vessels  were       
simultaneously sharpened at the stern1  
and the result was1 that the  #ajj horse
 engines drove the ,rifleman1 when      
sharpened1 as fast as she had           
previously been driven by the #bjj horse
 engines2 and the #dj horse engines     
drove the ,teazer1 when sharpened1 a    
knot an hour faster than she had        
previously been driven by the #ajj horse
 engines4 ,the immersion of both        
vessels was kept unchanged in each case2
 and the #ajj horse engines of the      
,teazer1 when transferred to the        
,rifleman1 drove that vessel1 after she 
had  been sharpened1 #b knots an hour   
faster than they had previously driven a
  vessel not much more than half the    
size4 ,these are important facts for    
every one to be acquainted with who is  
interested in the success of screw      
vessels1 and who seeks to obtain the    

maximum of efficiency with the minimum  
of expense4#a      #a ,see ,treatise on 
the ,screw ,propeller1 by ,john ,bourne1
 ,c4 ,e4        ,,proportions ,,of      
,,screws4    #fjb4 ,q4--,in fixing upon 
the proportions of a screw proper to    
propel any  given vessel1 how would you 
proceed8    ,a4--,i would first compute 
the probable resistance of the vessel1  
and ,i  would be able to find the       
relative resistances of the screw and   
hull1 and  in every case it is advisable
 to make the screw as large in diameter 
as  possible4 ,the larger the screw is1 
the greater will be the efficiency of   
the engine in propelling the vessel2 the
 larger will be the ratio of the  pitch 
to the diameter1 which produces a       
maximum effect2 and the smaller  will be
 the length of the screw or the fraction
 of a convolution to produce  a maximum 
effect4    #fjc4 ,q4--,will you         
illustrate this doctrine by a practical 
example8    ,a4--,the ,french screw     
steamer ,pelican was fitted successively

 with two  screws of four blades1 but   
the diameter of the first screw was     
#ih4db  inches1 and the diameter of the 
second #ed inches4 ,if the efficiency of
 the  first screw by represented by #a1 
that of the second screw will be        
represented by 4#hbc1 or1 in other      
words1 if the first screw would give a  
speed of #aj knots1 the second would    
give little more than #h4 ,the most     
advantageous ratio of pitch to diameter 
was found to be #b4b in the case of  the
 large screw1 and #a4chd in the case of 
the small4 ,the fraction of a           
convolution which was found to be most  
advantageous was 4#bha in the case of   
the large screw1 and 4#dej in the case  
of the small screw4    #fjd4 ,q--,were  
screws of four blades found to be more  
efficient than screws  with two8        
,a--,they were found to have less slip1 
but not to be more  efficient1 the      
increased slip in those of two blades   
being balanced by the  increased        
friction in those of four4 ,screws of   

two blades1 to secure a  maximum        
efficiency1 must have a finer pitch than
 screws of four4    #fje4 ,q4--,are the 
proportions found to be most suitable in
 the case of the  ,pelican applicable to
 the screws of other vessels8           
,a4--,only to those which have the same 
relative resistance of screw and  hull4 
,taking the relative resistance to be   
the area of immersed midship  section1  
divided by the square of the screw's    
diameter1 it will in the case  of the   
,rattler be #chj_/ajj or #c4h4 ,from the
 experiments made by ,,mm4 ,bourgois    
and ,moll on the screw steamer ,pelican1
 they have deduced the proportions of   
screws proper for all other classes of  
vessels1 whether the screws are of  two1
 four1 or six blades4    #fjf4          
,q4--,will you specify the nature of    
their deductions8    ,a4--,i will first 
enumerate those which bear upon screws  
with two blades4  ,when the relative    
resistance is #e4e the ratio of pitch to
 diameter should  be #a4jjf1 and the    

fraction of the pitch or proportion of  
one entire  convolution should be       
#j4ded4 ,when the relative resistance is
 #e1 the ratio  of pitch to diameter    
should be #a4jfi1 and fraction of pitch 
#j4dbh2 relative  resistance #d4e1 pitch
 #a4ace1 fraction #j4djb2 relative      
resistance #d1 pitch  #a4bje1 fraction  
#j4cgh2 relative resistance #c4e1 pitch 
#a4bgi1 fraction  #j4cee2 relative      
resistance #c1 pitch #a4ceg1 fraction   
#j4ccd2 relative  resistance #b4e1 pitch
 #a4dej1 fraction #j4cac2 relative      
resistance #b1 pitch  #a4efj1 fraction  
#j4bid2 relative resistance #a4e1 pitch 
#a4fhb1 fraction  #j4bge4 ,the relative 
resistance of #d is that which is usual 
in an auxiliary  line of battle ship1   
#c4e in an auxiliary frigate1 #c in a   
high speed line of  battle ship1 #b4e in
 a high speed frigate1 #b in a high     
speed corvette1 and  #a4e in a high     
speed despatch boat4    #fjg4 ,q4--,what
 are the corresponding proportions of   
screws of four blades8    ,a4--,the     

ratios of the pitches to the diameter   
being for each of the  relative         
resistances enumerated above1 #a4cdb1   
#a4dbe1 #a4eac1 #a4fjg1 #a4gje1  #a4haj1
 #a4icc1 #b4jhj1 and #b4bdc1 the        
respective fractions of pitch or        
fractions of a whole convolution will be
 #j4dee1 #j4dbh1 #j4djb1 #j4cgh1 #j4cee1
  #j4ccd1 #j4cac1 #j4bid1 and #j4bge4   
#fjh4 ,q4--,and what are the            
corresponding proportions proper for    
screws of  six blades8                  
,a4--,beginning with the relative       
resistance of #e4e as before1 the proper
  ratio of pitch to diameter for that   
and each of the successive resistances  
in the case of screws with six blades1  
will be #a4fgg1 #a4gga1 #a4hia1 #a4bjji1
  #b4aca1 #b4bfb1 #b4daf1 #b4fjj1       
#b4hjd2 and the respective fractions of 
pitch  will be #j4gid1 #j4gdi1 #j4gjc1  
#j4ffa1 #j4fba1 #j4ehe1 #j4edh1 #j4eae1 
and #j4dha4  ,these are the proportions 
which will give a maximum performance in
 every  case4#a      #a ,in my ,treatise

 on the ,screw ,propeller ,i have gone  
into these various  questions more fully
 than would consort with the limits of  
this  publication4        ,,screw       
,,vessels ,,with ,,full ,,and           
,,auxiliary ,,power4    #fji4 ,q4--,do  
you consider that the screw propeller is
 best adapted for  vessels of full      
power1 or for vessels with auxiliary    
power8    ,a4--,it is1 in my opinion1   
best adapted for vessels with auxiliary 
power1  and it is a worse propeller than
 paddle wheels for vessels which have   
habitually to encounter strong head     
winds4 ,screw vessels are but ill       
calculated--at least as constructed     
heretofore--to encounter head winds1    
and the legitimate sphere of the screw  
is in propelling vessels with  auxiliary
 power4    #faj4 ,q4--,does the screw   
act well in conjunction with sails8     
,a4--,i cannot say it acts better than  
paddles1 except in so far as it is  less
 in the way and is less affected by the 
listing or heeling over of the  ship4 ,a

 small steam power1 however1 acts very  
advantageously in aid of  sails1 for not
 only does the operation of the sails in
 reducing the  resistance of the hull   
virtually increase the screw's diameter1
 but the  screw1 by reducing the        
resistance which has to be overcome by  
the sails and  by increasing the speed  
of the vessel1 enables the sails to act 
with  greater efficiency1 as the wind   
will not rebound from them with as great
 a  velocity as it would otherwise do1  
and a larger proportion of the power of 
the wind will also be used up4 ,in the  
case of beam winds1 moreover1 the       
action of the screw1 by the larger      
advance it gives to the vessel will     
enable the sails to intercept a larger  
column of wind in a given time4 ,it     
appears1 therefore1 that the sails add  
to the efficiency of the screw1 and     
that the screw also adds to the         
efficiency of the sails4    #faa4       
,q4--,what is the comparative cost of   
transporting merchandise in  paddle     

steamers of full power1 in screw        
steamers of auxiliary power1 and in     
sailing ships8    ,a4--,that will depend
 very much upon the locality where the  
comparison is  made4 ,in the case of    
vessels performing distant ocean        
voyages1 in which  they may reckon upon 
the aid of uniform and constant winds1  
such as the  trade winds or the monsoon1
 sailing ships of large size will be    
able to  carry more cheaply than any    
other species of vessel4 ,but where the 
winds  are irregular and there is not   
much sea room1 or for such circumstances
 as  exist in the ,channel or           
,mediterranean trades1 screw vessels    
with auxiliary  power will constitute   
the cheapest instrument of conveyance4  
#fab4 ,q4--,are there any facts recorded
 illustrative of the accuracy of  this  
conclusion8    ,a4--,a full paddle      
vessel of #ajjj tons burden and #cej    
horses power1 will  carry about #djj    
tons of cargo1 besides coal for a voyage
 of #ejj miles1 and  the expense of such

 a voyage1 including wear and tear1     
depreciation1 c41  will be about #aijl4 
,the duration of the voyage will be     
about #de-a_/b  hours4 ,a screw vessel  
of #djj tons burden and #ajj horses     
power1 will carry  the same amount of   
cargo1 besides her coals1 on the same   
voyage1 and the  expense of the voyage1 
including wear and tear1 depreciation1  
c41 will be  not much more than #fjl4   
,an auxiliary screw vessel1 therefore1  
can carry  merchandise at one third of  
the cost of a full-powered paddle       
vessel4 ,by  similar comparisons made   
between the expense of conveying        
merchandise in  auxiliary screw steamers
 and sailing ships on coasting voyages1 
it appears  that the cost in screw      
steamers is about one third less than in
 the sailing  ships2 the greater        
expedition of the screw steamers much   
more than  compensating for the expense 
which the maintenance of the machinery  
involves4          ,,screw ,,and        
,,paddles ,,combined4      #fac4        

,q4--,would not a screw combined with   
paddles act in a similarly  advantageous
 way as a screw or paddles when aided by
 the wind8    ,a4--,if in any given     
paddle vessel a supplementary screw be  
added to  increase her power and speed1 
the screw will act in a more beneficial 
manner than if it had the whole vessel  
to propel itself1 and for a like  reason
 the paddles will act in a more         
beneficial manner4 ,there will be less  
slip both upon the paddles and upon the 
screw than if either had been  employed 
alone2 but the same object would be     
attained by giving the vessel  larger   
paddles or a larger screw4    #fad4     
,q4--,have any vessels been constructed 
with combined screw and  paddles8       
,a4--,not any that ,i know of1 except   
the great vessel built under the        
direction of ,mr4 ,brunel4 ,the ,bee    
many years since was fitted with both   
screw and paddles1 but this was for the 
purpose of ascertaining the  relative   
efficiency of the two modes of          

propulsion1 and not for the purpose  of 
using both together4    #fae4 ,q4--,what
 would be the best means of accelerating
 the speed of a  paddle vessel by the   
introduction of a supplementary screw8  
,a4--,if the vessel requires new        
boilers1 the best course of procedure   
would be to work a single engine giving 
motion to the screw with high  pressure 
steam1 and to let the waste steam from  
the high pressure engine  work the      
paddle engines4 ,in this way the power  
might be doubled without any  increased 
expenditure of fuel per hour1 and there 
would be a diminished  expenditure per  
voyage in the proportion of the         
increased speed4    #faf4 ,q4--,what    
would the increased speed be by doubling
 the power8    ,a4--,the increase would 
be in the proportion of the cube root of
 #a to the  cube root of #b1 or it would
 be #a4be times greater4 ,if1 therefore1
 the  existing speed were #aj miles1 it 
would be increased to #ab-a_/b miles by 
doubling the power1 and the vessel would

 ply with about a fourth less coals  by 
increasing the power in the manner      
suggested4    #fag4 ,q4--,is not high   
pressure steam dangerous in steam       
vessels8    ,a4--,not necessarily so1   
and it has now been introduced into a   
good number  of steam vessels with      
satisfactory results4 ,in the case of   
locomotive  engines1 where it is used so
 widely1 very few accidents have        
occurred2 and  in steam vessels the only
 additional source of danger is the     
salting of the  boiler4 ,this may be    
prevented either by the use of fresh    
water in the  boiler1 or by practising a
 larger amount of blowing off1 to insure
 which it  should be impossible to      
diminish the amount of water sent into  
the boiler  by the feed pump1 and the   
excess should be discharged overboard   
through a  valve near the water level of
 the boiler1 which valve is governed by 
a  float that will rise or fall with the
 fluctuating level of the water4 ,if    
the float be a copper ball1 a little    

water should be introduced into it      
before it is soldered or brazed up1     
which will insure an equality of        
pressure within and without the ball1   
and a leakage of water into it will     
then be less likely to take place4 ,a   
stone float1 however1 is cheaper1 and   
if properly balanced will be equally    
effective4 ,all steam vessels should    
have a large excess of boiling feed     
water constantly flowing into the       
boiler1 and a large quantity of water   
constantly blowing off through the      
surface valves1 which being governed by 
floats will open and let the            
superfluous water escape whenever the   
water level rises too high4 ,in this    
way the boiler will be kept from        
salting1 and priming will be much less  
likely to occur4 ,the great problem of  
steam navigation is the economy of      
fuel1 since the quantity of fuel        
consumed by a vessel will very much     
determine whether she is profitable or  
otherwise4 ,notwithstanding the         

momentous nature of this condition1     
however1 the consumption of fuel in     
steam vessels is a point to which very  
little attention has been paid1 and  no 
efficient means have yet been adopted in
 steam vessels to insure that  measure  
of economy which is known to be         
attainable1 and which has been  attained
 already in other departments of        
engineering in which the benefits  of   
such economy are of less weighty import4
 ,it needs nothing more than the        
establishment of an efficient system of 
registration in steam vessels1 to       
insure a large and rapid economy in the 
consumption of fuel1 as this  quality   
would then become the test of an        
engineer's proficiency1 and would       
determine the measure of his fame4 ,in  
the case of the ,cornish engines1 a     
saving of more than half the fuel was   
speedily effected by the introduction   
of the simple expedient of registration4
 ,in agricultural engines a like        
economy has speedily followed from a    

like arrangement2 yet in both of these  
cases the benefits of a large saving are
 less eminent than they would be in  the
 case of steam navigation2 and it is to 
be hoped that this expedient of         
improvement will now be speedily        
adopted4          ,,chapter ,x4         
,,examples ,,of ,,engines4           99 
99       99       99       99           
,,oscillating ,,paddle ,,engines4       
#fah4 ,q4--,will you describe the       
structure of an oscillating engine as   
made  by ,messrs4 ,penn8    ,a4--,to do 
this it will be expedient to take an    
engine of a given power1  and then the  
sizes may be given as well as an account
 of the configuration  of the parts3 we 
may take for an example a pair of       
engines of #ba-a_/b inches  diameter of 
cylinder1 and #bb inches stroke1 rated  
by ,messrs4 ,penn at #ab  horses power  
each4 ,the cylinders of this oscillating
 engine are placed  beneath the cranks1 
and1 as in all ,messrs4 ,penn's smaller 
engines1 the  piston rod is connected to

 the crank pin by means of a brass cap1 
provided  with a socket1 by means of    
which it is cuttered to the piston rod4 
,there is  but one air pump1 which is   
situated within the condenser between   
the  cylinders1 and it is wrought by    
means of a crank in the intermediate    
shaft--this crank being cut out of a    
solid piece of metal as in the          
formation of the cranked axles of       
locomotive engines4 ,the steam enters   
the  cylinder through the outer         
trunnions1 or the trunnions adjacent to 
the  ship's sides1 and enters the       
condenser through the two midship       
trunnions--a  short three ported valve  
being placed on the front of the        
cylinder to  regulate the flow of steam 
to and from the cylinder in the proper  
manner4  ,the weight of this valve on   
one side of the cylinder is balanced by 
a  weight hung upon the other side of   
the cylinder2 but in the most recent    
engines this weight is discarded1 and   
two valves are used1 which balance  one 

another4 ,the framing consists of an    
upper and lower frame of cast iron1     
bound together by eight malleable iron  
columns3 upon the lower frame the       
pillow blocks rest which carry the      
cylinder trunnions1 and the condenser   
and the bottom frame are cast in the    
same piece4 ,the upper frame supports   
the paddle shaft pillow blocks2 and     
pieces are bolted on in continuation of 
the upper frame to carry the paddle     
wheels1 which are overhung from the     
journal4    #fai4 ,q4--,what are the    
dimensions and arrangement of the       
framing8    ,a4--,the web1 or base plate
 of the lower frame is #c_/d of an ,inch
 thick1  and a cooming is earned all    
round the cylinder1 leaving an opening  
of  sufficient size to permit the       
necessary oscillation4 ,the cross       
section of  the upper frame is that of a
 hollow beam #f inches deep1 and about  
#c-a_/b  inches wide1 with holes at the 
sides to take out the core2 and the     
thickness of the metal is #ac_/afths of 

an inch4 ,both the upper and the lower  
frame is cast in a single piece1 with   
the exception of the continuations of   
the upper frame1 which support the      
paddle wheels4 ,an oval ring #c inches  
wide is formed in the upper frame1 of   
sufficient size to permit the working   
of the air pump crank2 and from this    
ring feathers run to the ends of the    
cross portions of the frame which       
supports the intermediate shaft         
journals4  ,the columns are #a-a_/b     
inches in diameter2 they are provided   
with collars at  the lower ends1 which  
rest upon bosses in the lower frame1 and
 with collars  at the upper ends for    
supporting the upper frame2 but the     
upper collars of  two of the corner     
columns are screwed on1 so as to enable 
the columns to be  drawn up when it is  
required to get the cylinders out4 ,the 
cross section of  the bottom frame is   
also of the form of a hollow beam1 #g   
inches deep1  except in the region of   
the condenser1 where it is1 of course1  

of a  different form4 ,the depth of the 
boss for the reception of the columns is
 a  little more than #g inches deep on  
the lower frame1 and a little more than 
#f  inches deep on the upper frame2 and 
the holes through them are so cored     
out1 that the columns only bear at the  
upper and lower edges of the hole1      
instead of all through it--a formation  
by which the fitting of the columns  is 
facilitated4    #fbj4 ,q4--,what are the
 dimensions of the condenser8           
,a4--,the condenser1 which is cast upon 
the lower frame1 consists of an  oval   
vessel #bb-a_/b inches wide1 by #b feet 
#d-a_/d inches long1 and #a foot        
#aj-a_/b inches deep2 it stands #i      
inches above the upper face of the      
bottom  frame1 the rest projecting      
beneath it2 and it is enlarged at the   
sides by  being carried beneath the     
trunnions4    #fba4 ,q4--,what are the  
dimensions of the air pump8    ,a4--,the
 air pump1 which is set in the centre of
 the condenser1 is #ae-a_/d  inches in  

diameter1 and has a stroke of #aa       
inches4 ,the foot valve is  situated in 
the bottom of the air pump1 and its seat
 consists of a disc of  brass1 in which 
there is a rectangular flap valve1      
opening upwards1 but  rounded on one    
side to the circle of the pump1 and so  
balanced as to enable  the valve to open
 with facility4 ,the balance weight1    
which is formed of  brass cast in the   
same piece as the valve itself1 operates
 as a stop1 by  coming into contact with
 the disc which constitutes the bottom  
of the pump2  the disc being recessed   
opposite to the stop to enable the valve
 to open  sufficiently4 ,this disc is   
bolted to the barrel of the pump by     
means of an  internal flange1 and before
 it can be removed the pump must be     
lifted out  of its place4 ,the air pump 
barrel is of brass to which is bolted a 
cast  iron mouth piece1 with a port for 
carrying the water to the hot well2     
within the hot well the delivery valve1 
which consists of a common flap  valve1 

is situated4 ,the mouth piece and the   
air pump barrel are made tight  to the  
condenser1 and to one another1 by means 
of metallic joints carefully  scraped to
 a true surface1 so that a little white 
or red lead interposed  makes an air    
tight joint4 ,the air pump bucket is of 
brass1 and the valve of  the bucket is  
of the common pot lid or spindle kind4  
,the injection water  enters through a  
single cock in front of the             
condenser--the jet striking  against the
 barrel of the air pump4 ,the air pump  
rod is maintained in its  vertical      
position by means of guides1 the lower  
ends of which are bolted to  the mouth  
of the pump1 and the upper to the oval  
in the top frame1 within  which the air 
pump crank works2 and the motion is     
communicated from this  crank to the    
pump rod by means of a short connected  
rod4 ,the lower frame is  not set       
immediately below the top frame1 but    
#b-a_/b inches behind it1 and  the air  
pump and condenser are #b-a_/b inches   

nearer one edge of the lower  frame than
 the other4    #fbb4 ,q4--,what are the 
dimensions of the cylinder8    ,a4--,the
 thickness of the metal of the cylinder 
is #i_/afths of an inch2 the  depth of  
the belt of the cylinder is #i-a_/b     
inches1 and its greatest  projection    
from the cylinder is #b-a_/b inches4    
,the distance from the lower  edge of   
the belt to the bottom of the cylinder  
is #aa-a_/b inches1 and from  the upper 
edge of the belt to the top flange of   
the cylinder is #i inches4  ,the        
trunnions are #g-a_/d inches diameter in
 the bearings1 and #c-a_/b inches  in   
width2 and the flanges to which the     
glands are attached for screwing in  the
 trunnion packings are #a-a_/b inch     
thick1 and have #g_/hths of an inch of  
projection4 ,the width of the packing   
space round the trunnions is #e_/hths of
  an inch1 and the diameter of the pipe 
passing through the trunnion            
#d-e_/hths1 which leaves #aa_/afths for 
the thickness of the metal of the       

bearing4 ,above and below each trunnion 
a feather runs from the edge of the     
belt or bracket between #c and #d inches
 along the cylinder1 for the sake of    
additional support2 and in large engines
 the feather is continued through  the  
interior of the belt1 and cruciform     
feathers are added for the sake of      
greater stiffness4 ,the projection of   
the outer face of the trunnion flange   
from the side of the cylinder is #f-a_/b
 inches2 the thickness of the flange    
round the mouth of the cylinder is #c_/d
 of an inch1 and its projection #a-c_/h 
inch2 the height of the cylinder        
stuffing box above the cylinder cover is
  #d-a_/h inches1 and its external      
diameter #d-c_/h inches--the diameter of
 the  piston rod being #b-a_/h inches4  
,the thickness of the stuffing box      
flange is  #a-a_/h inch4    #fbc4       
,q4--,will you describe the nature of   
the communication between the  cylinder 
and condenser8    ,a4--,the pipe leading
 to the condenser from the cylinder is  

made somewhat  bell mouthed where it    
joins the condenser1 and the gland for  
compressing  the packing is made of a   
larger internal diameter in every part  
except at  the point at which the pipe  
emerges from it1 where it accurately    
fits the  pipe so as to enable the gland
 to squeeze the packing4 ,by this       
construction  the gland may be drawn    
back without being jammed upon the      
enlarged part of  the pipe2 and the     
enlargement of the pipe toward the      
condenser prevents the  air pump barrel 
from offering any impediment to the free
 egress of the  steam4 ,the gland is    
made altogether in four pieces3 the ring
 which presses  the packing is made     
distinct from the flange to which the   
bolts are  attached which force the     
gland against the packing1 and both ring
 and  flange are made in two pieces1 to 
enable them to be got over the pipe4    
,the  ring is half checked in the       
direction of its depth1 and is          
introduced  without any other support to

 keep the halves together1 than what is 
afforded by the interior of the stuffing
 box2 and the flange is half  checked in
 the direction of its thickness1 so that
 the bolts which press  down the ring by
 passing through this half-checked part1
 also keep the  segments of the flange  
together4 ,the bottom of the trunnion   
packing space  is contracted to the     
diameter of the eduction pipe1 so as to 
prevent the  packing from being squeezed
 into the jacket2 but the eduction pipe 
does not  fit quite tight into this     
contracted part1 but1 while in close    
contact on  the lower side1 has about   
#a_/cbnd of an inch of space between the
 top of the  pipe and the cylinder1 so  
as to permit the trunnions to wear to   
that extent  without throwing a strain  
upon the pipe4 ,the eduction pipe is    
attached to  the condenser by a flange  
joint1 and the bolt holes are all made  
somewhat  oblong in the perpendicular   
direction1 so as to permit the pipe to  
be  slightly lowered1 should such an    

operation be rendered necessary by the  
wear of the trunnion bearings2 but in   
practice the wear of the trunnion       
bearings is found to be so small as to  
be almost inappreciable4    #fbd4       
,q4--,will you describe the valve and   
valve casing8    ,a4--,the length of the
 valve casing is #af-a_/b inches1 and   
its projection  from the cylinder is    
#c-a_/b inches at the top1 #d-a_/d      
inches at the centre1  and #b-a_/b      
inches at the bottom1 so that the back  
of the valve casing is not  made flat1  
but is formed in a curve4 ,the width of 
the valve casing is #i  inches1 but     
there is a portion of the depth of the  
belt #a-a_/b inch wider1  to permit the 
steam to enter from the belt into the   
casing4 ,the valve  casing is attached  
to the cylinder by a metallic joint2 the
 width of the  flange of this joint is  
#a-a_/d inch1 the thickness of the      
flange on the  casing #a_/b inch1 and   
the thickness of the flange on the      
cylinder #e_/hths of  an inch4 ,the     

projection from the cylinder of the     
passage for carrying the  steam upwards1
 and downwards1 from the valve to the   
top and bottom of the  cylinder1 is     
#b-a_/d inches1 and its width externally
 #h-e_/h inches4 ,the valve  is of the  
ordinary three ported description1 and  
both cylinder and valve  faces are of   
cast iron4    #fbe4 ,q4--,what          
description of piston is used8          
,a4--,the piston is packed with hemp1   
but the junk ring is made of  malleable 
iron1 as cast iron junk rings have been 
found liable to break3  there are four  
plugs screwed into the cylinder cover1  
which1 when removed1  permit a box key  
to be introduced1 to screw down the     
piston packing4 ,the  screws in the junk
 ring are each provided with a small    
ratchet1 cut in a  washer fixed upon the
 head1 to prevent the screw from turning
 back2 and the  number of clicks given  
by these ratchets1 in tightening up the 
bolts1  enables the engineer to know    
when they have all been tightened       

equally4 ,in  more recent engines1 and  
especially in those of large size1      
,messrs4 ,penn  employ for the piston   
packing a single metallic ring with     
tongue piece and  indented plate behind 
the joint2 and this ring is packed      
behind with hemp  squeezed by the junk  
ring as in ordinary hemp-packed pistons4
    #fbf4 ,q4--,will you describe the   
construction of the cap for connecting  
the  piston rod with the crank pin8     
,a4--,the cap for attaching the piston  
rod to the crank pin1 is formed         
altogether of brass1 which brass serves 
to form the bearing of the crank  pin4  
,the external diameter of the socket by 
which this cap is attached to  the      
piston rod is #c-e_/af inches4 ,the     
diameter of the crank pin is #c inches1 
and the length of the crank pin bearing 
#c-g_/h inches4 ,the thickness of the   
brass around the crank pin bearing is #a
 inch1 and the upper portion of the     
brass is secured to the lower portion1  
by means of lugs1 which are of such  a  

depth that the perpendicular section    
through the centre of the bearing  has a
 square outline measuring #g inches in  
the horizontal direction1 #c-g_/h       
inches from the centre of the pin to the
 level of the top of the lugs1 and      
#b-a_/b inches from the centre of the   
pin to the level of the bottom of the   
lugs4 ,the width of the lugs is #b      
inches1 and the bolts passing through   
them  are #a-a_/d inch in diameter4 ,the
 bolts are tapped into the lower portion
 of  the cap1 and are fitted very       
accurately by scraping where they pass  
through  the upper portion1 so as to act
 as steady pins in preventing the cover 
of  the crank pin bearing from being    
worked sideways by the alternate thrust 
on  each side4 ,the distance between the
 centres of the bolts is #e inches1 and 
in the centre of the cover1 where the   
lugs1 continued in the form of a web1   
meet one another1 an oil cup #a-e_/h    
inch in diameter1 #a-a_/h inch high1 and
  provided with an internal pipe1 is    

cast upon the cover1 to contain oil for 
the lubrication of the crank pin        
bearing4 ,the depth of the cutter for   
attaching the cap to the piston rod is  
#a-a_/d inch and its thickness is       
#c_/hths of an inch4    #fbg4 ,q4--,will
 you describe the means by which the air
 pump rod is  connected with the crank  
which works the air pump8               
,illustration3 ,fig4 #ej4 ,,air ,,pump  
,,connecting ,,rod ,,and ,,cross ,,head4
  ,messrs4  ,penn4    ,a4--,a similar   
cap to that of the piston rod attaches  
the air pump crank  to the connecting   
rod by which the air pump rod is moved1 
but in this  instance the diameter of   
the bearing is #e inches1 and the length
 of the  bearing is about #c inches4    
,the air pump connecting rod and cross  
head are  shown in perspective in fig4  
#ej4 ,the thickness of the brass        
encircling the  bearing of the shaft is 
three fourths of an inch upon the edge1 
and #a-a_/h  inch in the centre1 the    
back being slightly rounded2 the width  

of the lugs  is #a-e_/h inch1 and the   
depth of the lugs is #b inches upon the 
upper brass1  and #b inches upon the    
lower brass1 making a total depth of #d 
inches4 ,the  diameter of the bolts     
passing through the lugs is #a inch1 and
 the bolts are  tapped into the lower   
brass1 and accurately fitted into the   
upper one1 so  as to act as steady pins1
 as in the previous instance4 ,the lower
 eye of the  connecting rod is forked1  
so as to admit the eye of the air pump  
rod2 and  the pin which connects the two
 together is prolonged into a cross     
head1 as  shown in fig4 #ej4 ,the ends  
of this cross head move in guides4 ,the 
forked  end of the connecting rod is    
fixed upon the cross head by means of a 
feather1 so that the cross head partakes
 of the motion of the connecting  rod1  
and a cap1 similar to that attached to  
the piston rod1 is attached to  the air 
pump rod1 for connecting it with the    
cross head4 ,the diameter of  the air   
pump rod is #a-a_/b inch1 the external  

diameter of the socket  encircling the  
rod is #b-a_/h inches1 and the depth of 
the socket #d-a_/b  inches from the     
centre of the cross head4 ,the depth of 
the cutter for  attaching the socket to 
the rod is #a inch1 and its thickness   
#e_/af inch4 ,the  breadth of the lugs  
is #a-c_/h inch1 the depth #a-a_/d inch1
 making a total  depth of #b-a_/b       
inches2 and the diameter of the bolts   
seven eighths of an  inch4 ,the diameter
 of the cross head at the centre is #b  
inches1 the  thickness of each jaw      
around the bearing #a inch1 and the     
breadth of each  #i_/af inch4    #fbh4  
,q4--,what are the dimensions of the    
crank shaft and cranks8    ,a4--,the    
diameter of the intermediate shaft      
journal is #d-c_/af inches1 and  of the 
paddle shaft journal #d-c_/h inches2 the
 length of the journal in each  case is 
#e inches4 ,the diameter of the large   
eye of the crank is #g inches1  and the 
diameter of the hole through it is      
#d-c_/h inches2 the diameter of  the    

small eye of the crank is #e-a_/d       
inches1 the diameter of the hole        
through it being #c inches4 ,the depth  
of the large eye is #d-a_/d inches1 and 
of the small eye #c-c_/d inches2 the    
breadth of the web is #d inches at the  
shaft end1 and #c inches at the pin end1
 and the thickness of the web is        
#b-e_/h inches4 ,the width of the notch 
forming the crank in the intermediate   
shaft for working the air pump is       
#c-a_/b inches1 and the width of each of
  the arms of this crank is #c-ae_/af   
inches4 ,both the outer and inner       
corners  of the crank are chamfered     
away1 until the square part of the crank
 meets  the round of the shaft4 ,the    
method of securing the cranks pins into 
the  crank eyes of the intermediate     
shaft consists in the application of a  
nut  to the end of each pin1 where it   
passes through the eye1 the projecting  
end  of the pin being formed with a     
thread upon which the nut is screwed4   
#fbi4 ,q4--,will you describe the       

eccentric and eccentric rod8            
,illustration3 ,fig4 #ea4 ,,eccentric   
,,and ,,rod4 ,messrs4 ,penn4            
,a4--,the eccentric and eccentric rod   
are shown in fig4 #ea4 ,the eccentric   
is put on the crank shaft in two halves1
 joined in the diameter of largest      
eccentricity by means of a single bolt  
passing through lugs on the central     
eye1 and the back balance is made in a  
separate piece five eighths of an  inch 
thick1 and is attached by means of two  
bolts1 which also help to bind  the     
halves of the eccentric together4 ,the  
eccentric strap is half an inch  thick1 
and #a-a_/d inch broad1 and the flanges 
of the eccentric1 within which  the     
strap works1 are each three eighths of  
an inch thick4 ,the eccentric rod  is   
attached to the eccentric hoop by means 
of two bolts passing through  lugs upon 
the rod1 and tapped into a square boss  
upon the hoop2 and pieces  of iron1 of a
 greater or less thickness1 are         
interposed between the  surfaces in     

setting the valve1 to make the eccentric
 rod of the right  length4 ,the         
eccentric rod is kept in gear by the    
push of a small horizontal  rod1        
attached to a vertical blade spring1 and
 it is thrown out of gear by  means of  
the ordinary disengaging apparatus1     
which acts in opposition to  the spring1
 as1 in cases where the eccentric rod is
 not vertical1 it acts  in opposition to
 the gravity of the rod4    #fcj4       
,q4--,will you explain in detail the    
construction of the valve  gearing1 or  
such parts of it as are peculiar to the 
oscillating engine8    ,a4--,the        
eccentric rod is attached by a pin1 #a  
inch in diameter1 to an  open curved    
link or sector with a tail projecting   
upward and passing  through an eye to   
guide the link in a vertical motion4    
,the link is formed  of iron            
case-hardened1 and is #b-c_/d inches    
deep at the middle1 and #b-c_/h  inches 
deep at the ends1 and #a inch broad4    
,the opening in the link1 which  extends

 nearly its entire length1 is #a-e_/af  
inch broad2 and into this  opening a    
brass block #b inches long is truly     
fitted1 there being a hole  through the 
block #c_/d inch diameter1 for the      
reception of the pin of the  valve shaft
 lever4 ,the valve shaft is #a-c_/d inch
 diameter at the end next  the link or  
segment1 and diminishes regularly to the
 other end1 but its  cross section      
assumes the form of an octagon in its   
passage round the  cylinder1 measuring  
mid-way #a-a_/d inch deep1 by about     
#c_/d inch thick1 and  the greatest     
depth of the finger for moving the valve
 is about #a inch4 ,the  depth of the   
lever for moving the valve shaft is #b  
inches at the broad1 and  #a-a_/d inch  
at the narrow end4 ,the internal breadth
 of the mortice in which  the valve     
finger moves is #e_/af inch1 and its    
external depth is #a-c_/d inch1  which  
leaves three eighths of an inch as the  
thickness of metal round the  hole2 and 
the breadth1 measuring in the direction 

of the hole1 is #a-a_/b  inch4 ,the     
valve rod is three fourths of an inch in
 diameter1 and the  mortice is connected
 to the valve rod by a socket #a inch   
long1 and #a-a_/h  inch diameter1       
through which a small cutter passes4 ,a 
continuation of the  rod1 eleven        
sixteenths of an inch diameter1 passes  
upward from the mortice1  and works     
through an eye1 which serves the purpose
 of a guide4 ,in addition  to the guide 
afforded to the segment by the ascending
 tail1 it is guided at  the ends upon   
the columns of the framing by means of  
thin semicircular  brasses1 #d inches   
deep1 passing round the columns1 and    
attached to the  segment by two #c_/h   
inch bolts at each end1 passing through 
projecting  feathers upon the brasses   
and segment1 three eighths of an inch in
  thickness4 ,the curvature of the      
segment is such as to correspond with   
the  arc swept from the centre of the   
trunnion to the centre of the valve     
lever  pin when the valve is at half    

stroke as a radius2 and the operation of
 the  segment is to prevent the valve   
from being affected by the oscillation  
of  the cylinder1 but the same action1  
would be obtained by the employment of a
  smaller eccentric with more lead4 ,in 
some engines the segment is not formed  
in a single piece1 but of two curved    
blades1 with blocks interposed at the   
ends1 which may be filed down a little1 
to enable the sides of the slot to  be  
brought nearer1 as the metal wears away4
    #fca4 ,q4--,what kind of plummer    
blocks are used for the paddle shaft    
bearings8    ,a4--,the paddle shaft     
plummer blocks are altogether of brass1 
and are  formed in much the same manner 
as the cap of the piston rod1 only that 
the  sole is flat1 as in ordinary       
plummer blocks1 and is fitted between   
projecting lugs of the framing1 to      
prevent side motion4 ,in the bearings   
fitted on this plan1 however1 the upper 
brass will generally acquire a good     
deal of play after some amount of wear4 

,the bolts are worked slack in the      
holes1 though accurately fitted at      
first2 and it appears expedient1        
therefore1 either to make the bolts very
 large1 and the sockets through  which  
they pass very deep1 or to let one brass
 fit into the other4    #fcb4 ,q4--,how 
are the trunnion plummer blocks made8   
,a4--,the trunnion plummer blocks are   
formed in the same manner as the  crank 
shaft plummer blocks2 the nuts are kept 
from turning back by means of  a        
pinching screw passing through a        
stationary washer4 ,it is not expedient 
to cast the trunnion plummer blocks upon
 the lower frame1 as is sometimes  done2
 for the cylinders1 being pressed from  
the steam trunnions by the  steam1 and  
drawn in the direction of the condenser 
by the vacuum1 have a  continual        
tendency to approach one another2 and as
 they wear slightly  toward midships1   
there would be no power of readjustment 
unless the plummer  blocks were movable4
 ,the flanges of the trunnions should   

always fit tight  against the plummer   
block sides1 but there should be a      
little play sideways  at the necks of   
the trunnions1 so that the cylinder may 
be enabled to  expand when heated1      
without throwing an undue strain upon   
the trunnion  supports4    #fcc4        
,q4--,what kind of paddle wheel is      
supplied with these oscillating         
engines8    ,a4--,the wheels are of the 
feathering kind1 #i feet #h inches in   
diameter1  measuring to the edges of the
 floats2 and there are #aj floats upon  
each  wheel1 measuring #d feet #f inches
 long each1 and #ah-a_/b inches broad4  
,there  are two sets of arms to the     
wheel1 which converge to a cast iron    
centre1  formed like a short pipe with  
large flanges1 to which the arms are    
affixed4  ,the diameter of the shaft1   
where the centre is put on1 is #d-a_/b  
inches1 the  external diameter of the   
pipe is #h inches1 and the diameter of  
the flanges  is #bj inches1 and their   
thickness #a-a_/d inch4 ,the flanges are

 #ab inches  asunder at the outer edge1 
and they partake of the converging      
direction of  the arms4 ,the arms are   
#b-a_/d inches broad and half an inch   
thick2 the heads  are made conical1 and 
each is secured into a recess upon the  
side of the  flange by means of three   
bolts4 ,the ring which connects together
 the arms1  runs round at a distance of 
#c feet #f inches from the centre1 and  
the  projecting ends of the arms are    
bent backward the length of the lever   
which  moves the floats1 and are made   
very wide and strong at the point where 
they  cross the ring1 to which they are 
attached by four rivets4 ,the feathering
  action of the floats is accomplished  
by means of a pin fixed to the  interior
 of the paddle box1 set #c inches in    
advance of the centre of the  shaft1 and
 in the same horizontal line4 ,this pin 
is encircled by a cast  iron collar1 to 
which rods are attached #a-c_/h inch    
diameter in the centre1  proceeding to  
the levers1 #g inches long1 fixed on the

 back of the floats in  the line of the 
outer arms4 ,one of these rods1 however1
 is formed of nearly  the same          
dimensions as one of the arms of the    
wheel1 and is called the  driving arm1  
as it causes the cast iron collar to    
turn round with the  revolution of the  
wheel1 and this collar1 by means of its 
attachments to  the floats1 accomplishes
 the feathering action4 ,the            
eccentricity in this  wheel is not      
sufficient to keep the floats in the    
vertical position1 but in  the position 
between the vertical and the radial4    
,the diameter of the pins  upon which   
the floats turn is #a-c_/h inch1 and    
between the pins and paddle  ring two   
stud rods are set between each of the   
projecting ends of the arms1  so as to  
prevent the two sets of arms from being 
forced nearer or further  apart2 and    
thus prevent the ends of the arms from  
hindering the action of  the floats1 by 
being accidentally jammed upon the sides
 of the joints4  ,stays1 crossing one   

another1 proceed from the inner flange  
of the centre to  the outer ring of the 
wheel1 and from the outer flange of the 
centre to the  inner ring of the wheel1 
with the view of obtaining greater      
stiffness4 ,the  floats are formed of   
plate iron1 and the whole of the joints 
and joint pins  are steeled1 or formed  
of steel4 ,for sea-going vessels the    
most approved  practice is to make the  
joint pins of brass1 and also to bush   
the eyes of  the joints with brass2 and 
the surface should be large to diminish 
wear4    #fcd4 ,q4--,can you give the   
dimensions of any other oscillating     
engines8    ,a4--,in ,messrs4 ,penn's   
#ej horse power oscillating engine1 the 
diameter of  the cylinder is #c feet #d 
inches1 and the length of the stroke #c 
feet4 ,the  thickness of the metal of   
the cylinder is #a inch1 and the        
thickness of the  cylinder bottom is    
#a-c_/d inch1 crossed with feathers1 to 
give it additional  stiffness4 ,the     
diameter of the trunnion bearings is #a 

foot #b inches1 and  the breadth of the 
trunnion bearings #e-a_/b inches4       
,messrs4 ,penn1 in their  larger        
engines1 generally make the area of the 
steam trunnion less than  that of the   
eduction trunnion1 in the proportion of 
#cb to #cg2 and the  diameter of the    
eduction trunnion is regulated by the   
internal diameter of  the eduction pipe1
 which is about #a_/eth of the diameter 
of the cylinder4  ,but a somewhat larger
 proportion than this appears to be     
expedient3 ,messrs4  ,rennie make the   
area of their eduction pipes1 in        
oscillating engines1 #a_/bb;d  of the   
area of the cylinder4 ,in the           
oscillating engines of the ,oberon1 by  
,messrs4 ,rennie1 the cylinder is #fa   
inches diameter1 and #a-a_/b inch thick 
above and below the belt1 but in the    
wake of the belt it is #a-a_/d inch     
thick1 which is also the thickness of   
metal of the belt itself4 ,the  internal
 depth of the belt is #b feet #f inches1
 and its internal breadth is  #d inches4

 ,the piston rod is #f-c_/d inches in   
diameter1 and the total depth  of the   
cylinder stuffing box is #b feet #d     
inches1 of which #ah inches  consists of
 a brass bush--this depth of bearing    
being employed to prevent  the stuffing 
box or cylinder from wearing oval4      
#fce4 ,q4--,can you give any other      
examples8    ,a4--,the diameter of      
cylinder of the oscillating engines of  
the steamers  ,pottinger1 ,ripon1 and   
,indus1 by ,miller  ,ravenhill1 is #gf  
inches1 and the  length of the stroke #g
 feet4 ,the thickness of the metal of   
the cylinder is  #a-aa_/af inch2        
diameter of the piston rod #h-c_/d      
inches2 total depth of  cylinder        
stuffing box #c feet2 depth of bush in  
stuffing box #d inches2 the  rest of the
 depth1 with the exception of the space 
for packing1 being  occupied with a very
 deep gland1 bushed with brass4 ,the    
internal diameter  of the steam pipe is 
#ac inches2 diameter of steam trunnion  
journal #be  inches2 diameter of        

eduction trunnion journal #be inches2   
thickness of metal  of trunnions #b-a_/d
 inches2 length of trunnion bearings #aa
 inches2  projection of cylinder jacket1
 #h inches2 depth of packing space in   
trunnions1 #aj inches2 width of packing 
space in trunnions1 or space round  the 
pipes1 #a-a_/b inch2 diameter of crank  
pin #aj-a_/d inches2 length of  bearing 
of crank pin #ae-a_/b1 inches4 ,there   
are six boilers on the tubular  plan in 
each of these vessels2 the length of    
each boiler is #aj feet #f  inches1 and 
the breadth #h feet2 and each boiler    
contains #fb tubes #c inches  in        
diameter1 and #f feet #f inches long1   
and two furnaces #f feet #d-a_/b inches 
long1 and #c feet #a-a_/b inch broad4   
#fcf4 ,q4--,is it the invariable        
practice to make the piston rod cap of  
brass in the way you have described8    
,a4--,in all oscillating engines of any 
considerable size1 the cover of the     
connecting brass1 which attaches the    
crank pin to the connecting rod1 is     

formed of malleable iron2 and the socket
 also1 which is cuttered to the end  of 
the piston rod1 is of malleable iron1   
and is formed with a ,t head1  through  
which bolts pass up through the brass1  
to keep the cover of the  brass in its  
place4    #fcg4 ,q4--,is the piston of  
an oscillating engine made deeper than  
in  common engines8    ,a4--,it is      
expedient1 in oscillating engines1 to   
form the piston with a  projecting rim  
round the edge above and below1 and a   
corresponding recess  in the cylinder   
cover and cylinder bottom1 whereby the  
breadth of bearing  of the solid part of
 the metal will be increased1 and in    
many engines this  is now done4    #fch4
 ,q4--,would any difficulty be          
experienced in keeping the trunnions    
tight in a high pressure oscillating    
engine8    ,a4--,it is very doubtful    
whether the steam trunnions of a high   
pressure  oscillating engine will       
continue long tight if the packing      
consists of  hemp2 and it appears       

preferable to introduce a brass ring1 to
 embrace the  pipe1 cut spirally1 with  
an overlap piece to cover the cut1 and  
packed  behind with hemp4    #fci4      
,q4--,how is the packing of the         
trunnions usually effected8    ,a4--,the
 packing of the trunnions1 after being  
plaited as hard as  possible1 and cut to
 the length to form one turn round the  
pipe1 is dipped  into boiling tallow1   
and is then compressed in a mould1      
consisting of two  concentric cylinders1
 with a gland forced down into the      
annular space by  three to six screws in
 the case of large diameters1 and one   
central screw  in the case of small     
diameters4 ,unless the trunnion packings
 be well  compressed1 they will be      
likely to leak air1 and it is1          
therefore1  necessary to pay particular 
attention to this condition4 ,it is also
 very  important that the trunnions be  
accurately fitted into their brasses by 
scraping1 so that there may not be the  
smallest amount of play left upon  them2

 for if any upward motion is permitted1 
it will be impossible to  prevent the   
trunnion packings from leaking4         
,,direct ,,acting ,,screw ,,engine4     
#fdj4 ,q4--,will you describe the       
configuration and construction of a     
direct  acting screw engine8    ,a4--,i 
will take as an example of this species 
of engine1 the engine  constructed by   
,messrs4 ,john ,bourne  ,co41 for the   
screw steamer ,alma1 a  vessel of #ejj  
tons burden4 ,this engine is a single   
steeple engine laid on  its side1 and in
 its general features it resembles the  
engines of the  ,amphion already        
described1 only that there is one       
cylinder instead of two4  ,the cylinder 
is of #db inches diameter and #db inches
 stroke1 and the vessel  has been       
propelled by this single engine at the  
rate of fourteen miles an  hour4        
#fda4 ,q4--,is not a single engine      
liable to stick upon the centre so that 
it cannot be started or reversed with   
facility8    ,a4--,a single engine is no

 doubt more liable to stick upon the    
centre than  two engines1 the cranks of 
which are set at right angles with one  
another2  but numerous paddle vessels   
are plying successfully that are        
propelled by a  single engine1 and the  
screw offers still greater facility than
 paddles for  such a mode of            
construction4 ,in the screw engine      
referred to1 as the  cylinder is laid   
upon its side1 there is no unbalanced   
weight to be lifted  up every stroke1   
and the crank1 whereby the screw shaft  
is turned round1  consists of two discs 
with a heavy side intended to balance   
the momentum of  the piston and its     
connections2 but these counter-weights  
by their  gravitation also prevent the  
connecting rod and crank from continuing
 in  the same line when the engine is   
stopped1 and in fact they place the     
crank  in the most advantageous position
 for starting again when it has to be   
set  on4    #fdb4 ,q4--,will you explain
 the general arrangement of the parts of

 this  engine8    ,a4--,the cylinder    
lies on its side near one side of the   
vessel1 and from  the end of the        
cylinder two piston rods extend to a    
cross head sliding  athwartships1 in    
guides1 near the other side of the      
vessel4 ,to this cross  head the        
connecting rod is attached1 and one end 
of it partakes of the  motion of the    
cross head or piston1 while the other   
end is free to follow  the revolution of
 the crank on the screw shaft4    #fdc4 
,q4--,what is the advantage of two discs
 entering into the composition  of the  
crank instead of one8    ,a4--,a double 
crank1 such as two discs form with the  
crank pin1 is a much  steadier          
combination than would result if only   
one disc were employed with  an         
over-hung pin4 ,then the friction on the
 neck of the shaft is made one  half    
less by being divided between the two   
bearings1 and the short  prolongation of
 the shaft beyond the journal is        
convenient for the  attachment of the   

eccentrics to work the valves4    #fdd4 
,q4--,will you enumerate some of the    
principal dimensions of this  engine8   
,a4--,the bottom frame1 on which also   
the condenser is cast1 forms the base   
of the engine3 on one end of it the     
cylinder is set2 on the other end are   
the guides for the cross head1 and in   
the middle are the bearings for the     
crank shaft4 ,the part where the        
cylinder stands is two feet high above  
the  engine platform1 and the elevation 
to the centre of the guides or the      
centre of the shaft is #aj inches higher
 than this4 ,the metal both of the  side
 frames and bottom flange is #a-a_/d    
inch thick4 ,the cylinder has flanges   
cast on its sides1 upon which it rests  
on the bottom frame1 and it is sunk     
between the sides of the frame so as to 
bring the centre of the cylinder in  the
 same plane as the centre of the screw  
shaft4 ,the opening left at the  guides 
for the reception of the guide blocks is
 #f inches deep1 and the  breadth of the

 bearing surface is #aa inches4 ,the    
cover of the guides is #h  inches deep  
at the middle1 and about half the depth 
at the ends1 and holes  are cored       
through the central web for two oil cups
 on each guide4 ,the brass  for each of 
the crank shaft bearings is cut into    
four pieces so that it may  be tightened
 in the up and down direction by the    
bolts1 which secure the  plummer block  
cap1 and tightened in the athwartship   
direction1 which is the  direction of   
the strain1 by screwing up a            
wedge-formed plate against the  side of 
the brass1 a parallel plate being       
applied to the other side of the  brass1
 which may be withdrawn to get out the  
wedge piece when the shaft  requires to 
be lifted out of its place4 ,the air    
pump is bolted to one side  of the      
bottom frame1 and a passage is cast on  
it conducting from the  condenser to the
 air pump4 ,in this passage the inlet   
and outlet valves at  each end of the   
air pump are situated1 and appropriate  

doors are formed  above them to make    
them easily accessible4 ,the outlet     
passage leading from  the air pump      
communicates with the waste water pipe1 
through which the  water expelled by the
 air pump is discharged overboard4      
#fde4 ,q4--,is the cylinder of the usual
 strength and configuration8            
,a4--,the cylinder is formed of cast    
iron in the usual way1 and is #a-a_/h   
inch thick in the barrel4 ,the ends are 
of the same thickness1 but are each     
stiffened with six strong feathers4 ,the
 piston is cast open4 ,the bottom of  it
 is #e_/hths of an inch thick1 and it is
 stiffened by six feathers #c_/d of  an 
inch thick2 but the feather connecting  
the piston rod eyes is #a-a_/d inch     
thick1 and the metal round the eyes is  
#b inches thick4 ,the piston is closed  
by a disc or cover #e_/hths of an inch  
thick1 secured by #ae bolts1 and this   
cover answers also the purpose of a junk
 ring4 ,the piston packing consists  of 
a single cast iron ring #c-a_/b inches  

broad1 and #a_/b inch thick1 packed     
behind with hemp4 ,this ring is formed  
with a tongue piece1 with an indented   
plate behind the cut2 and the cut is    
oblique to prevent a ridge forming in   
the cylinder4 ,the total thickness of   
the piston is #e-a_/b inches4 ,the      
piston  rods are formed with conical    
ends for fitting into the piston1 but   
are  coned the reverse way as in        
locomotives1 and are secured in the     
piston by  nuts on the ends of the rods1
 these nuts being provided with ratchets
 to  prevent them from unscrewing       
accidentally4    #fdf4 ,q4--,what       
species of slide valve is employed8     
,a4--,the ordinary three ported valve1  
and it is set on the top of the         
cylinder4 ,the cylinder ports are       
#d-a_/b inches broad by #bd inches long2
 and  to relieve the valve from the     
great friction due to the pressure on so
  large a surface1 a balance piston is  
placed over the back of the valve1 to   
which it is connected by a strong link2 

and the upward pressure on this  piston 
being nearly the same as the downward   
pressure on the valve1 it  follows that 
the friction is extinguished1 and the   
valve can be moved with  great case with
 one hand4 ,the balance piston is #ba   
inches in diameter4 ,in  the original   
construction of this balance piston two 
faults were committed4  ,the passage    
communicating between the condenser and 
the top of the balance  piston was too  
small1 and the pins at the ends of the  
link connecting the  valve and balance  
piston were formed with an inadequate   
amount of bearing  surface4 ,it followed
 from this misproportion that the       
balance piston1 being  adjusted to take 
off nearly the whole of the pressure1   
lifted the valve off  the face at the   
beginning of each stroke4 ,for the      
escape of the steam into  the eduction  
passage momentarily impaired the vacuum 
subsisting there1 and  owing to the     
smallness of the passage leading to the 
space above the  balance piston1 the    

vacuum subsisting in that space could   
not be impaired  with equal rapidity4   
,the balance piston1 therefore1 rose by 
the upward  pressure upon it momentarily
 predominating over the downward        
pressure on  the valve2 but this fault  
was corrected by enlarging the          
communicating  passage between the top  
of the balance piston and the eduction  
pipe4 ,the  smallness of the pins at the
 ends of the link connecting the valve  
and  balance piston1 caused the surfaces
 to cut into one another1 and to wear   
very rapidly1 and the pins and eyes in  
this situation should be large in       
diameter1 and as long as they can be    
got1 as they are not so easily          
lubricated as the other bearings about  
the engine1 and are moreover kept at  a 
high temperature by the steam4 ,the     
balance piston is packed in the same    
way as the main piston of the engine4   
,its cylinder1 which is only a few      
inches in length1 is set on the top of  
the valve casing1 and a trunk  projects 

upwards from its centre to enable the   
connecting link to rise up  in it to    
attain the necessary length4            
,illustration3 ,fig #eb4 ,,connecting   
,,rod4 ,messrs4 ,bourne  ,co4    #fdg4  
,q4--,what is the diameter of the piston
 rods and connecting rod8    ,a4--,the  
piston rods1 which are two in number1   
are #c inches diameter1 and  #ab feet   
#aj inches long over all4 ,they were1   
however1 found to be rather  small1 and 
have since been made half an inch       
thicker4 ,the connecting rod  consists  
of two rods1 which are prolongations of 
the bolts that connect the  sides of the
 brass bushes which encircle the crank  
pin and cross head4 ,the  connecting rod
 is shown in perspective in fig4 #eb4   
,the rods composing it  are each #b-c_/d
 inches in diameter4    #fdh4 ,q4--,will
 you describe the configuration of the  
cross head4    ,a4--,the cross head1    
exhibited in fig4 #ec1 is a round piece 
of iron like a  short shaft1 with two   
unequal arms keyed upon it1 the longer  

of which b  works the air pump1 and the 
shorter c works the feed pump4 ,the     
piston  rods enter these arms at a ,a4  
,the cross head is #h inches diameter   
where  it is embraced by the connecting 
rod at e1 and #g inches diameter where  
the air pump and feed pump arms are     
fixed on4 ,the ends of the cross head d 
d1 for a length of #ab inches1 are      
reduced to #c inches diameter where they
  fit into round holes in the centre of 
the guide blocks4 ,those blocks are of  
cast iron #f inches deep1 #aa inches    
wide1 and #ad inches long1 and they are 
formed with flanges #a inch thick on the
 inner sides of the blocks4 ,the        
projection of the air pump lever from   
the centre of the cross head is #a  foot
 #i inches1 and it is bent #e-c_/d      
inches to one side to enable it to      
engage the air pump rod4 ,the eye of    
this arm is #f inches broad and about #b
  inches thick4 ,at the part where one  
of the piston rods passes through it1   
the arm is #h inches deep and #f inches 

wide2 but the width thereafter  narrows 
to #c inches1 and finally to #b inches2 
and the depth of the web of  the arm    
reduces from #h inches at the piston    
rod1 to #d inches at the eye1  which    
receives the end of the air pump rod4   
,the feed pump arm is only #c  inches   
thick1 and has #i inches of projection  
from the centre of the cross  head2 but 
the eye attached to it on the opposite  
side of the cross head for  the         
reception of the other piston rod is of 
the same length as that part of  the air
 pump arm which one of the piston rods  
passes through4 ,the piston  rods have  
strong nuts on each side of each of     
these arms to attach them to  the arms1 
and also to enable the length of the    
piston rods to be suitably  adjusted1 to
 leave equal clearance between the      
piston and each end of the  cylinder at 
the termination of the stroke4          
,illustration3 ,fig4 #ec4    ,,cross    
,,head ,,and ,,pump ,,arms4 ,messrs4    
,bourne  ,co4    #fdi4 ,q4--,will you   

recapitulate the main particulars of the
 air pump8    ,a4--,the air pump is made
 of brass #ab-a_/b inches diameter and  
#db inches  stroke1 and the metal of the
 barrel is #i_/afths of an inch thick4  
,the air  pump bucket is a solid piston 
of brass1 #f-a_/b inches deep at the    
edge1 and  #g inches deep at the eye2   
and in the edge three grooves are turned
 to hold  water which answers the       
purpose of packing4 ,the inlet and      
outlet valves of  the air pump consist  
of brass plates #a_/b inch with strong  
feathers across  them1 and in each plate
 there are six grated perforations      
covered by india  rubber discs #g inches
 in diameter4 ,these six perforations   
afford  collectively an area for the    
passage of the water equal to the area  
of the  pump4 ,the air pump rod is of   
brass1 #b-a_/b inches diameter4    #fej4
 ,q4--,what are the constructive        
peculiarities of the discs and crank    
pin8    ,a4--,the discs1 which are #fd  
inches diameter1 are formed of cast     

iron1 and  are #b-a_/b inches thick in  
the body1 and #e inches broad at the    
rim4 ,the  crank shaft is #h-a_/b inches
 diameter1 and the central boss of the  
disc  which receives the shaft measures 
#aj inches through the eye1 and the     
metal  of the eye is #c inches thick4   
,in the part of the disc opposite to the
 crank  pin1 the web is thickened to #aj
 inches for nearly the whole semicircle1
  with the view of making that side of  
the disc heavier than the other side2   
and when the engine is stopped1 the     
gravitation of this heavy side raises   
the crank pin to the highest point it   
can attain1 whereby it is placed in  mid
 stroke1 and cannot rest with the piston
 rods and connecting rod in a           
horizontal line4 ,the crank pin is      
#h-a_/b inches diameter1 and the length 
of  the bearing or rubbing part of it is
 #af inches4 ,it is secured at the ends 
to the discs by flanges #ah inches      
diameter1 and #b inches thick4 ,these   
flanges are indented into thickened     

parts of the discs1 and are each        
attached to its corresponding disc by   
six bolts #b inches diameter1           
countersunk in the back of the disc1 and
 tapped into the malleable iron  flange4
 ,besides this attachment1 each end of  
the pin1 reduced to #d-a_/b  inches     
diameter1 passes through a hole in its  
corresponding disc1 and the  ends of the
 pin are then riveted over4 ,the crank  
pin is perforated through  the centre by
 a small hole about #c_/d of an inch in 
diameter1 and three  perforations       
proceed from this central hole to the   
surface of the pin4 ,each  crank shaft  
bearing is similarly perforated1 and    
pipes are cast in the  discs connecting 
these perforations together4 ,the result
 of this  arrangement is1 that a large  
part of the oil or water fed into the   
bearings  of the shaft is driven by the 
centrifugal action of the discs to the  
surface of the crank pin1 and in this   
way the crank pin may be oiled or       
cooled with water in a very effectual   

manner4 ,to intercept the water or oil  
which the discs thus drive out by their 
centrifugal action1 a light paddle  box 
or splash board of thin sheet brass is  
made to cover the upper part of  each of
 the discs1 and an oil cup with         
depending wick is supported by the  tops
 of these paddle boxes1 which wick is   
touched at each revolution of the  crank
 by a bridge standing in the middle of  
an oil cup attached to the  crank pin4  
,the oil is wiped from the wick by the  
projecting bridge at each  revolution1  
and subsides into the cup from whence it
 proceeds to lubricate  the crank pin   
bearing4 ,this is the expedient commonly
 employed to oil the  crank pins of     
direct acting engines2 but in the engine
 now described1 there  are over and     
above this expedient1 the communicating 
passages from the  shaft bearings to the
 surface of the pin1 by which means any 
amount of  cooling or lubrication can be
 administered to the crank pin bearing1 
without the necessity of stopping or    

slowing the engine4    ,illustration3   
,fig4 #ed4 ,,double ,,disc ,,crank4     
,messrs4 ,bourne  ,co4    #fea4         
,q4--,what is the diameter of the screw 
shaft8    ,a4--,the screw shaft is      
#g-a_/b inches diameter1 but the        
bearings on each  side of the disc are  
#h-a_/b inches diameter1 and #af inches 
long4 ,between the  side of the disc and
 the side of the contiguous bearings    
there is a short  neck extending #d-c_/d
 inches in the length of the shaft1 and 
hollowed out  somewhat to permit the    
passage of the piston rod2 for one      
piston rod passes  immediately above the
 shaft on the one side of the discs1 and
 the other  piston rod passes           
immediately below the shaft on the other
 side of the  discs4 ,a short piece of  
one piston rod is shown in fig4 #ed4    
,illustration3 ,fig4 #ee4 ,,thrust      
,,bearing4 ,messers4 ,bourne  ,co4      
,illustration3 ,fig4 #ef4 ,,coupling    
,,cranks4 ,messers4 ,bourne  ,co4       
#feb4 ,q4--,how is the thrust of the    

screw shaft received8    ,a4--,the      
thrust of the screw shaft is received   
upon #g collars1 each #a inch  thick1   
and with #a inch of projection above the
 shaft4 ,the plummer block for          
receiving the thrust of the shaft is    
shown in fig4 #ee1 and the coupling to  
enable the screw propeller to be        
disconnected from the engine1 so that it
  may revolve freely when the vessel is 
under sail1 is shown in fig4 #ef4 ,when 
it is required to disengage the         
propeller from the engine1 the pins     
passing  through the opposite eyes shown
 fig4 #ef1 are withdrawn by means of    
screws  provided for that purpose1 and  
the propeller and the engine are        
thenceforth  independent of one another4
    ,illustration3 ,fig4 #eg4 ,,link    
,,motion4 ,messrs4 ,bourne  ,co4        
#fec4 ,q4--,will you describe the       
arrangement of the valve gearing8       
,a4--,the end of the screw shaft1 after 
emerging from the bearing beside  the   
disc1 is reduced to a diameter of #d    

inches1 and is prolonged for #d-a_/b    
inches to give attachment to the cam or 
curved plate which gives motion to  the 
expansion valve4 ,this plate is #c-a_/b 
inches thick1 and a stud #c-a_/b  inches
 diameter is fixed in the plate at a    
distance of #e inches from the  centre  
of the shaft4 ,to this stud an arm is   
attached which extends to a  distance of
 #b inches from the centre of the shaft 
in the opposite  direction1 and the end 
of this arm carries a pin of #b-a_/b    
inches diameter4  ,from the pin most    
remote from the centre of the shaft1 a  
rod #b-a_/b inches  broad and #a inch   
thick extends to the upper end of the   
link of the link  motion2 and from the  
pin least remote from the centre of the 
shaft1 a  similar rod extends to the    
lower end of the link of the link       
motion4 ,this  link1 which is           
represented in fig4 #eg1 is #b-a_/d     
inches broad1 #a inch thick1  and is    
capable of being raised or lowered #be  
inches in all4 ,in the open  part of the

 link is a brass block1 which1 by       
raising or lowering the link1  takes    
either the position in which it is      
represented at the centre of the  link1 
or a position at either end of it4      
,through the hole in the brass  block a 
pin passes to attach the brass to the   
end of a lever fixed on the  valve      
shaft2 so that whatever motion is       
imparted to the brass block is          
communicated to the valve through the   
medium of this lever4 ,if the brass     
block be set in the middle of the link1 
no motion is communicated to it1  and   
the valve being consequently kept       
stationary and covering both ports1  the
 engine stops4 ,if the link be lowered  
until the brass block comes to the      
upper end of the link1 the valve        
receives the motion of the eccentric for
  going ahead1 and the engine moves     
ahead2 whereas if the link be raised    
until the brass block comes to the lower
 end of the link1 the valve  receives   
the motion of the backing eccentric1 and

 the engine moves astern4  ,instead of  
eccentrics1 however1 pins at the end of 
the shaft are employed  in this engine1 
the arrangement partaking of the nature 
of a double crank2  but the backing pin 
has less throw than the going ahead pin1
 whereby the  efficient length of the   
link for going ahead is increased2 and  
the  operation of backing1 which does   
not require to be performed at the      
highest  rate of speed1 is sufficiently 
accommodated by about half the throw    
being  given to the valve that is given 
in going ahead4 ,a valve shaft extends  
across the end of the cylinder with two 
levers standing up1 which engage        
horizontal side rods extending from a   
small cross head on the end of the      
valve rod4 ,a lever extends downwards   
from the end of the valve shaft1 which  
is connected by a pin to the brass block
 within the link2 and the link is  moved
 up or down by the starting handle1     
which1 by means of a spring bolt        
shooting into a quadrant1 holds the     

starting handle at any position in      
which it may be set4    #fed4 ,q4--,what
 is the diameter and pitch of the screw 
propeller8    ,a4--,the diameter is #g  
feet and the pitch #ad feet4 ,the       
propeller is ,holm's  conchoidal        
propeller4 ,its diameter is smaller than
 is advisable1 being  limited by the    
draught of water of the vessel2 and the 
vessel was required  to have a small    
draught of water to go over a bar4 ,this
 engine makes1 under  favorable         
circumstances1 #ajj strokes per minute4 
,the speed of piston with  this number  
of strokes is #gjj feet per minute1 and 
the engine works  steadily at this      
speed1 the shock and tremor arising from
 the arrested  momentum of the moving   
parts being taken away by the           
counterbalance applied  at the discs4   
,,locomotive ,,engine4    #fee4         
,q4--,will you describe the principal   
features of a modern locomotive  engine8
    ,a4--,i will take for this purpose  
the locomotive ,snake1 constructed by   

,john ,v4 ,gooch for the ,london and    
,south ,western ,railway1 as an example 
of a  modern locomotive of good         
construction1 adapted for the narrow    
gauge4 ,the  length of the wheel base of
 this engine is #ab feet #h-a_/b inches4
 ,there are  two cylinders1 each        
#ad-a_/d inches diameter and #ba inches 
stroke4 ,the total  weight of the engine
 is #ai tons2 and this weight is so     
distributed on the  wheels as to throw  
#h tons on the leading wheels1 #f tons  
on the driving  wheels1 and #e tons on  
the hind wheels4 ,the engine is made    
with outside  cylinders1 and the        
cylinders are raised somewhat out of the
 horizontal line  to enable them better 
to clear the leading wheels4    #fef4   
,q4--,what are the dimensions of the    
boiler8    ,a4--,the interior of the    
fire box is #c feet #g-a_/d inches wide 
by #c feet  #e-a_/b inches long1        
measuring in the direction of the rails4
 ,the area of the  fire grate is        
consequently #ab4d square feet4 ,the    

bars are somewhat lower on  the side    
next the fire door than at the side next
 the tubes1 and the mean  height of the 
crown of the fire box above the bars is 
#c feet #aj inches4 ,the  top edge of   
the fire door is about #g inches lower  
than the crown of the  fire box4 ,the   
fire box is divided transversely by a   
corrugated feather or  bridge of plate  
iron1 containing water1 about #c-a_/b   
inches wide1 and of  about one-third of 
the height of the fire box in the centre
 of the feather1  and about two-thirds  
the height of the fire box at the sides 
where it joins  the sides of the fire   
box4 ,the internal shell of the fire box
 tapers  somewhat upwards to facilitate 
the disengagement of the steam4 ,it is  
about  #b inches narrower and shorter at
 the top than at the bottom2 the water  
space between the external and internal 
shell of the fire box being #b  inches  
at the bottom and #c inches at the top4 
#feg4 ,q4--,of what material is the fire
 box composed8    ,a4--,the external    

shell of the fire box is formed of iron 
plates #c_/hths of  an inch thick1 and  
the internal shell is formed of copper  
plates #a_/d inch  thick1 but the tube  
plate is #c_/d inch thick4 ,the fire    
grate is rectangular1  and the internal 
and external shells are tied together by
 iron stay bolts  #c_/d inch diameter1  
and pitched about #d inches apart4 ,the 
roof of the fire  box is stiffened by   
six strong bars extending from side to  
side of the fire  box like beams1 and   
the top of the fire box is secured to   
these bars1 so  that it cannot be forced
 down without breaking or bending them4 
#feh4 ,q4--,what are the dimensions of  
the barrel of the boiler8    ,a4--,the  
barrel of the boiler is #c feet #g-a_/b 
inches in diameter1 and #aj  feet long4 
,it is formed of iron plates #c_/hths of
 an inch thick1 riveted  together4 ,it  
is furnished with #aha brass tubes      
#a-g_/h inch diameter and #aj  feet     
long1 secured at the ends by ferules4   
,the tube plate at the smoke box  end is

 #e_/hths of an inch thick1 and the tube
 plates above the tubes are  tied       
together by eight iron rods #g_/hths of 
an inch thick1 extending from  end to   
end of the boiler4 ,the metal of the    
tubes is somewhat thicker at the  end   
next the fire1 being #ac wire gauge at  
fire box end1 and #ad wire gauge  at    
smoke box end4 ,the rivets of the boiler
 are #c_/d inch diameter and #a-a_/b    
inch pitch4 ,the plating of the ash pan 
is #e_/afths of an inch thick1 and the  
plating of the smoke box is #c_/afths of
 an inch thick4    #fei4 ,q4--,will you 
describe the structure of the framework 
on which the  boiler and its attachments
 rest1 and in which the wheels are set8 
,a4--,the framework or framing consists 
of a rectangular structure of plate     
iron circumscribing the boiler1 with    
projecting lugs or arms for the         
reception of the axles of the wheels4   
,in this engine the sides of the        
rectangle are double1 or1 as far as     
regards the sides1 there are virtually  

two framings1 one for the reception of  
the driving axles1 and the other for    
the reception of the axles not connected
 with the engine4 ,the whole of the     
parts of the outer and inner framings   
are connected together by knees at  the 
corners1 and the double sides are       
elsewhere connected by intervening      
brackets and stays1 so as to constitute 
the whole into one rigid structure4     
,the whole of the plating of the inside 
frame is #c_/d inch thick and #i inches 
deep4 ,the plating of the outside frame 
is of the same thickness and depth  at  
the fore part1 until it reaches abaft   
the position of the cylinders and       
guides1 where it reduces to #a_/b inch  
thick4 ,the axle guard of the leading   
wheels is formed of #c_/d plate bolted  
to the frame with angle iron guides4    
,the axle guards of the trailing wheels 
are formed of two #a_/b inch plates1    
with cast iron blocks between them to   
serve as guides4 ,the ends of the       
rectangular frame are formed of plates  

#c_/d thick1 and at the front end  there
 is a buffer beam of oak #d-a_/b inches 
thick and #ae inches deep4 ,the  draw   
bolt is #b inches diameter4 ,there are  
two strong stays on each side1  joining 
the barrel of the boiler to the inside  
framing1 and one angle iron  on each    
side joining the bottom of the smoke box
 to the inside framing4    #ffj4        
,q4--,of what construction are the      
wheels8    ,a4--,the wheels and axles   
are of wrought iron1 and the tires of   
the wheels  are of steel4 ,the driving  
wheels are #f feet #f-a_/b inches in    
diameter1 and  the diameter of crank pin
 is #c-a_/b inches4 ,the diameter of the
 smaller  wheels is #dh-a_/b inches4    
,the axle boxes are of cast iron with   
bushes of  ,fenton's metal1 and the     
leading axle has four bearings4 ,the    
springs are  formed of steel plates1 #c 
feet long1 #d inches broad1 and #ab inch
 thick4  ,the axle of the driving wheel 
has two eccentrics1 forged solid upon   
it1 for  working the pumps4    #ffa4    

,q4--,will you specify the dimensions of
 the principal parts of the  engine8    
,a4--,each of the cylinders which is    
#ad-a_/d inches diameter1 has the valve 
casing cast upon it4 ,the steam ports   
are #ac inches long and #a-e_/h inches  
broad1 and the exhaust port is #b-a_/b  
inches broad4 ,the travel of the valve  
is #d-a_/h inches1 the lap #a inch1 and 
the lead #a_/d inch4 ,the piston is #d  
inches thick3 its body is formed of     
brass with a cover of cast iron1 and    
between the body and the cover two      
flanges1 forged on the piston rod1 are  
introduced to communicate the push and  
pull of the piston to the rod4 ,the     
piston rod is of iron1 #b-a_/b inches   
diameter4 ,the guide bars for guiding   
the top of the piston rod are of steel1 
#d inches broad1 fixed to rib iron      
bearers1 with hard wood #a_/d of an inch
 thick1 interposed4 ,the connecting  rod
 is #f feet long between the centres1   
and is fitted with bushes of white      
metal4 ,the eccentrics are formed of    

wrought iron1 and have #d-a_/h inches of
  throw4 ,the link of the link motion is
 formed of wrought iron4 ,it is hung by 
a link from a pin attached to the       
framing2 and instead of being           
susceptible  of upward and downward     
motion1 as in the case of the link      
represented in  fig4 #eg a rod          
connecting the valve rod with the       
movable block in the link1  is          
susceptible of this motion1 whereby the 
same result is arrived at as if  the    
link were moved and the block was       
stationary4 ,one or the other  expedient
 is preferable1 according to the general
 nature of the  arrangements adopted4   
,the slide valve is of brass1 and the   
regulator  consists of two brass slide  
valves worked over ports in a chest in  
the  steam pipe1 set in the smoke box4  
,the steam pipe is of brass1 ,no4 #ad4  
wire  gauge1 perforated within the      
boiler barrel with holes #a_/abth of an 
inch in  diameter along its upper side4 
,the blast pipe1 which is of copper1 has

 an  orifice of #d-a_/d inches diameter4
 ,there is a damper1 formed like a      
,venetian  blind1 with the plates       
running athwartships at the end of the  
tubes4    ,illustration3 ,fig4 #eh4     
,,safety ,,valve4 ,gooch4    #ffb4      
,q4--,of what construction is the safety
 valve8    ,a4--,there are two safety   
valves1 consisting of pistons #a-c_/af  
inch in  diameter1 and which are kept   
down by spiral springs placed           
immediately over  them4 ,a section of   
this valve is given in fig4 #eh4        
#ffc4 ,q4--,what are the dimensions of  
the feed pumps8    ,a4--,the feed pumps 
are of brass1 with plungers #d inches   
diameter and  #c-a_/d inches stroke4    
,the feed pipe is of copper1 #b inches  
diameter4 ,a good  deal of trouble has  
been experienced in locomotives from the
 defective  action of the feed pump1    
partly caused by the leakage of steam   
into the  pumps1 which prevented the    
water from entering them1 and partly    
from the  return of a large part of the 

water through the valves at the return  
stroke  of the pump1 in consequence of  
the valve lifting too high4 ,the pet    
cock--a  small cock communicating with  
the interior of the pump--will allow any
  steam to escape which gains admission1
 and the air which enters by the cock   
cools down the barrel of the pump1 so   
that in a short time it will be in a    
condition to draw4 ,the most ordinary   
species of valve in the feed pumps of   
locomotives1 is the ball valve4         
,notwithstanding the excellent          
performance of the best examples of     
locomotive engines1 it is quite certain 
that there is still much room for       
improvement2 and indeed various sources 
of economy are at present visible1      
which1 if properly developed1 would     
materially reduce the expense of the    
locomotive power4 ,in all engines the   
great source of expense is the fuel2    
and although the consumption of fuel has
 been greatly reduced within the  last  
ten or fifteen years1 it is capable of  

being still further reduced by  certain 
easy expedients of improvement1 which   
therefore it is important  should be    
universally applied4 ,one of these      
expedients consists in heating  the feed
 water by the waste steam2 and the feed 
water should in every case  be sent into
 the boiler boiling hot1 instead of     
being quite cold1 as is  at present     
generally the case4 ,the ports of the   
cylinders should be as  large as        
possible2 the expansion of the steam    
should be carried to a  greater extent2 
and in the case of engines with outside 
cylinders1 the  waste steam should      
circulate entirely round the cylinders  
before escaping  by the blast pipe4 ,the
 escape of heat from the boiler should  
be more  carefully prevented2 and the   
engine should be balanced by weights on 
the  wheels to obviate a waste of power 
by yawing on the rails4 ,the most       
important expedient of all1 however1    
lies in the establishment of a system   
of registering the performance of all   

new engines1 in order that  competition 
may stimulate the different constructors
 to the attainment of  the utmost       
possible economy2 and under the stimulus
 of comparison and  notoriety1 a large  
measure of improvement would speedily   
ensue4 ,the  benefits consequent on     
public competition are abundantly       
illustrated by the  rapid diminution of 
the consumption of fuel in the case of  
agricultural  engines1 when this        
stimulus was presented4                 
,,chapter ,,xi      ,,of ,,various      
,,forms1 ,,applications1 ,,and          
,,appliances ,,of ,,the ,,steam         
,,engine4      ,in the ,english edition 
of this work1 the first part of this    
chapter is  devoted to examples of      
,portable and fixed ,agricultural       
engines1 of  different makers and styles
 of workmanship1 but not in sufficient  
detail1  nor illustrated on large enough
 scale to be of practical value as      
models1  forming rather in fact an      
illustrated catalogue of the            

manufacturer1 than a  study for the     
mechanic4 ,on this account1 they have   
been entirely omitted1  and their place 
supplied by a few illustrations from    
,american workmanship1  not only of     
,steam ,engines1 of various forms and   
applications1 but also of  various      
machines1 or appliances1 connected with 
the working of engines1 as  for the     
determination1 or regulation of         
pressure1 of the boilers2 for the       
supply or feed of the boilers1 the      
regulation of the speed of the engine1  
and the like4    ,the ,gauges used in   
this country to show the pressures of   
steam in boilers  are of various        
constructions1 but perhaps the most     
common is the ,bourdon1  or1 as it is   
known here1 the ,ashcroft gauge1 from   
the party introducing it1  and holding  
the patent4 ,fig4 #ei represents its    
interior construction4 ,it  consists of 
a thin metallic tube1 a1 bent into      
nearly a complete circle  closed at one 
end1 the steam being introduced at the  

other1 at b4 ,the  effect of the        
pressure of the steam on the interior of
 the tube is to  expand the circle1 more
 or less according to the pressure1 the 
elasticity  of the metal returning the  
circle to its original position1 when   
the  pressure is removed4 ,the free or  
closed end of the tube is connected by a
  link c with a lever d1 at the opposite
 end of which is segmental gear1  in    
gear with a pinion1 on which is a hand1 
which marks the pressure on a  dial4    
,the dial and hand are not shown on the 
cut1 but are on the exterior  case      
removed to show the construction4       
,illustration3 ,fig4 #ei4               
,illustration3 ,fig4 #fj4    ,fig4 #fj  
is an elevation of a boiler with        
,clark's ,patent ,steam and ,fire       
,regulator attached1 for the control of 
the draft of the chimney by the         
pressure of steam in the boiler4 ,it    
consists of a chamber1 a1 with a        
flexible diaphragm or cover on top1 in  
communication with the boiler4 ,on  this

 diaphragm rests a plunger or piston1   
which is held down like a safety  valve1
 by a lever and weight1 b4 ,the end of  
the lever is connected with a  balanced 
damper1 c1 in the chimney4 ,the weight1 
b1 is placed at any  required position  
on the lever1 and when the pressure of  
steam in the  boiler1 exerted on the    
diaphragm1 becomes sufficient to raise  
the weight1  the lever rises1 and the   
damper begins to close1 and to check the
 draft in  the chimney4 ,when properly  
adjusted1 the machine works on a        
variation of  from1 one to two pounds   
between the extremes of motion4 ,when   
the dampers  are very large1 say #c feet
 or over1 they should be set on rollers1
 like  common grindstone rollers2 the   
regulator should be attached directly to
 the  damper1 the length of the pipe    
connecting the regulator with the boiler
  being of no account4    ,illustration3
 ,fig4 #fa4    ,porter's ,patent        
,governor1 fig4 #fa1 is a modification  
of the ordinary  centrifugal governor4  

,very small balls are employed1 from    
#b-a_/d to #b-e_/h  inches in diameter4 
,these swing from a single joint at the 
axis of the  spindle1 which is the most 
sensitive arrangement1 and make from    
#cjj to #cej  revolutions per minute1 at
 which speed their centrifugal force    
lifts the  counterpoise4 ,the lower arms
 are jointed to the upper ones at the   
centres  of the balls1 and connect with 
the slide by joints about two inches    
apart4  ,the counterpoise may be        
attached to the slide in any manner2 for
 the sake  of elegance1 it is put in the
 form of a vase rising between the arms1
 its  stem forming the slide4 ,the vase 
is hollow and filled with lead1 and     
weighs  from #fj lbs4 to #age lbs4 ,it  
moves freely on the spindle1 through    
nearly  twice the vertical distances    
traversed by the balls1 and is capable  
of  rising from #b-a_/b to #c inches1   
before its rim will touch the arms4 ,it 
is  represented in the figure as lifted 
through about one half of its range of  

action4    ,the standard is bored out of
 the solid1 forming a long and perfect  
bearing  for the spindle2 the arms and  
balls are of gun metal1 the joint pins  
of  steel2 every part of the governor is
 finished bright1 except the bracket    
carrying the lever1 and the square base 
of the standard1 which are painted4     
,the pulley is from #c to #aj inches in 
diameter1 and makes in the larger  sizes
 about #abe revolutions1 and in the     
smaller #bcj revolutions per minute2    
the higher speed of the governor being  
got up by gearing4    ,mr4 ,porter      
warrants the following action in this   
governor1 operating any  regulating     
valve or cut-off which is in reasonably 
good order4 ,the engine  should be run  
with the stop-valve wide open1 and1     
except the usual oiling1  will require  
no attention from the engineer1 under   
any circumstances1 after  it is started1
 until it is to be stopped4 ,no increase
 in the pressure of  steam will affect  
its motion perceptibly4 ,the extreme    

possible variation in  the speed1       
between that at which the regulating    
valve will be held wide  open1 and that 
at which it will be closed1 is from #c  
to #e per cent41 being  least in the    
largest governors4 ,this is less than   
#a_/f of the variation  required by the 
average of ordinary governors1 and is   
with difficulty  detected by the senses4
 ,the entire load which the engine is   
capable of  driving may be thrown on or 
off at once1 and one watching the       
revolutions  cannot tell when it is     
done4 ,the governor will be sensibly    
affected by a  variation in the motion  
of the engine of #a revolution in #hjj4 
,notwithstanding this extreme           
sensitiveness1 or rather by reason of   
it1 it  will not oscillate1 but when the
 load is uniform will stand quite1 or   
nearly1 motionless4    ,for the supply  
of the water to the boiler1 in many     
positions1 it is very  convenient to    
have a pump unconnected with the engine4
 ,on this account it  is very usual in  

this country to have what are called    
donkey pumps or  engines independent of 
the main engines1 which can be used to  
feed the  boilers1 or for supplying     
water for many other purposes4    ,fig4 
#fb is a longitudinal section of the    
,worthington ,steam ,pump1 the first  of
 its kind1 and for many years in        
successful operation4    ,the general   
arrangement is that of a ,steam         
,cylinder1 the piston rod of  which1    
carried through into the water cylinder 
and attached directly to the  water     
plunger1 works back and forth without   
rotary motion1 and of course  without   
using either crank or fly wheel4        
,illustration3 ,fig4 #fb4    ,in the    
figures1 a is the ,steam ,cylinder--b1  
the ,steam ,chest--d1 a  handle for     
regulating the steam valve--f1 the      
starting bar g1 g1  tappets attached to 
the valve rod1 which is moved by the    
contact of the arm  e1 on the piston rod
 with said tappets--h1 the double-acting
 water  plunger working through a       

packing ring--o1 o1 force valves--o'1   
o'1  suction valves4 ,the pump piston is
 represented as moving from right to    
left1 the arrows indicating the course  
of the water through the passages4  ,the
 suction valves o'1 on the right side1  
and the force valves o1 on  the left    
side1 are show open2 x1 is an air       
chamber made of copper2 s1  the suction 
pipe terminating in a vacuum chamber2   
made by prolonging the  suction pipe1   
and closing it perfectly tight at the   
top1 the connection  being made to the  
pump by a branch as shown2 m1 m1 are    
hand-hole plates1  affording easy access
 to the water valves2 n1 n1 small holes 
through the  plunger1 which relieve the 
pressure near the end of the stroke1 to 
give  momentum to throw the valves when 
working at slow speed4    ,illustration3
 ,fig4 #fc4    ,fig4 #fc is a           
perspective view of ,h4,r4              
,worthington's ,duplex ,steam ,pump4    
,the  prominent peculiarity of this pump
 is its valve motion4 ,as seen in the   

cut1  two steam pumps are placed side by
 side 7or end to end1 if desired74 ,each
  pump1 by a rock shaft connected with  
its piston rod1 gives a constant and    
easy motion to the steam valve of the   
other4 ,each pump therefore gives  steam
 to and starts its neighbor1 and then   
finishes its own stroke1 pausing  an    
instant till its own steam valve1 being 
opened by the other pump1 allows  it to 
make the return stroke4    ,this        
combined action produces a perfectly    
positive valve motion without  dead     
points1 great regularity and ease of    
motion1 and entire absence of  noise or 
shock of any kind4 ,both kinds of pumps 
are made by ,mr4  ,worthington1 of      
various size according to the           
requirements1 the duplex  being used for
 boiler feed and for the supply of      
cities with water4    ,fig4 #fd is a    
side elevation of the ,woodward ,steam  
,pump4 ,the pump is direct  acting4 ,the
 steam and water piston being on the    
same rod1 but momentum is  obtained to  

throw the valves by means of a fly      
wheel1 placed beyond the  pump1 and     
connected with the piston rod by a cross
 head and a yoke4 ,the  machine is      
simple in its construction and action1  
and is extensively used4    ,giffard's  
,injector1 both in ,europe and this     
country1 is quite extensively  used to  
supply the place of a pump1 as          
independent feed for all classes of     
boilers4 ,it is represented in elevation
 and section1 figs4 #fe and #ff4        
,illustration3 ,fig4 #fd4               
,illustration3 ,fig4 #fe4               
,illustration3 ,fig4 #ff4      ,a1 steam
 pipe leading from the boiler4 ,b1 a    
perforated tube or  cylinder1 through   
which the steam passes into the space b4
 ,c screwed  rod for regulating the     
passage of steam through the annular    
conical space  c1 and worked by the     
handle d_/4 ,e1 suction pipe1 leading   
from the  tank or hot well to small     
chamber m4 ,f1 annular conical opening  
or  discharge pipe1 the size of which is

 regulated by the movement of the tube  
or cylinder ,b4 ,g1 hand wheel for      
actuating the cylinder ,b4 ,h1  opening1
 in connection with the atmosphere1     
intervening between discharge  pipe ,f  
and the receiving pipe through which the
 water is forced4 ,i1  tube through     
which the water passes to the boiler4   
,k1 valve for  preventing the return of 
the water from the boiler when the      
injector is not  working4 ,l1 waste or  
overflow pipe4 ,m1 nut to tighten the   
packing rings  g and upper packing i in 
cylinder ,b4 ,n1 lock nut to hold ,m4   
,the pipe ,a is connected with the steam
 space of the boiler at its highest     
part1 to obtain as dry steam as         
possible4 ,the passage of the steam into
 ,a  is controlled by a cock1 as is also
 the feed pipe to the boiler4 ,in       
working1 both are opened1 the steam     
passes through ,a into the space b1  and
 issuing through the nozzle c with the  
pressure due to its head1 and a  partial
 vacuum by its contact with the feed    

water1 it drives this water in          
connection with the jet through the pipe
 ,f into the pipe ,i in  connection with
 the water space of the boiler4         
,method of ,working4--,turn the wheel so
 as to permit a small quantity of  water
 to flow to the instrument4 ,open the   
steam cock connecting the  apparatus    
with the boiler4 ,turn slightly the     
handle1 which will admit a  small       
quantity of steam to the apparatus2 a   
partial vacuum is thus  produced1       
causing the water to enter through the  
supply pipe4 ,as soon as  this happens1 
which can be observed at the overflow   
pipe1 the supply of  steam or water may 
be increased as required1 up to the     
capacity of the  instrument1 regulating 
either by means of the wheel and handle1
 so as to  prevent any overflow4 ,the   
quantity of water delivered into the    
boiler1 may  be varied by means of the  
stop cocks on the steam and water pipes1
 without  altering the handles on the   
injector2 a graduated cock on the water 

supply  pipe is very convenient for this
 purpose4    ,the machines are          
manufactured by ,wm4 ,sellers  ,co4     
,philadelphia4    ,as an example of     
,portable ,steam ,engines1 of which     
there are large numbers  in this country
 of different manufacturers1 we give the
 representation  7fig4 #fg7 of one made 
by ,j4,c4 ,hoadley1 of ,lawrence1 ,mass4
    ,illustration3 ,fig4 #fg4    ,in    
these machines1 the rules and           
proportions of the locomotive engine are
  adapted to the requirements of        
stationary power1 for all purposes under
  forty horse power4 ,the leading ideas 
are3 high velocity1 high pressure1  good
 valve motion1 large fire-box1 numerous 
and short flues1 and steam  blast4 ,the 
characteristic features are3 great      
strength of boiler1 fully  adequate to  
bear with safety #bjj4 lbs4 pressure per
 sq4 in41 great  compactness and        
simplicity1 large and adjustable wearing
 surfaces1 and the  entire absence of   
all finish1 or polish1 for mere show4   

,the cylinder is placed over the centre 
of the boiler1 at the fire-box end1  so 
that the strain due to the engine is    
central to the boiler 7which serves  as 
bed plate72 the starting valve is under 
the hand of the engineer when at  the   
fire door2 and both ends of the crank   
shaft are available for driving         
pulleys4    ,for the sake of            
compactness1 the cylinders are set low1 
by means of a  depression in the boiler 
between the stands of the crank shaft1  
to admit of  the play of the crank and  
connecting rod4 ,all the parts are      
attached to the  boiler1 which is made  
of sufficient strength to bear all extra
 strain due  to the working of the      
engine4    ,they have feed water heater1
 force pumps1 ,jackson's governor and   
valve1  belt for governor1 belt pulley1 
turned on the face1 steam gauge2        
everything1 in short1 necessary to the  
convenient working of a steam  engine4  
,all engines are fired up and tried     
before they leave the shop1 and  they   

are warranted tight1 safe1 and complete4
    ,a strong and convenient running    
gear1 so arranged as to be easily       
attached  and detached at pleasure1 is  
furnished1 if desired2 forming1 when    
separate1  a useful wagon4              
,illustration3 ,fig4 #fh4    ,fig4 #fh  
is a compact vertical engine1 as built  
by ,r4 ,hoe  ,co41 of this  city4 ,it is
 intended to drive printing presses1 but
 is adapted to any kind  of work1 and is
 especially suited to such places as    
require economy of  space4 ,although the
 value of expansion has been called in  
question by some  of the engineers of   
the ,united ,states ,navy1 and under an 
appropriation from  ,congress is now to 
be made the subject of experiment2 yet1 
in almost all  the manufactories and    
workshops of the ,united ,states1 no    
matter what the  form of steam engine1  
or the purposes to which it is applied1 
whether  stationary1 locomotive1 or     
marine1 some form of cut-off1 by which  
expansion  of the steam can be availed  

of1 is considered indispensable4 ,many  
varieties  are in use1 but those engines
 are most popular in which the cut-off  
is  applied directly to the valves on   
the cylinder1 opening them quickly and  
shutting off almost instantly1 avoiding 
all wire drawing of the steam at  the   
ports1 and regulating the speed of the  
engine promptly4 ,of this class  of     
engines1 those manufactured by the      
,corliss ,steam ,engine ,company1 of    
,providence1 ,r4,i41 are perhaps the    
widest known1 not only for their        
extensive introduction1 but also from   
having1 by a long and successful        
litigation1 established the claims of   
the patentee1 ,mr4 ,george ,h4 ,corliss4
    ,illustration3 ,fig4 #gj4    ,fig4  
#gj is a section of the cylinder and    
valve chests of a horizontal  ,corliss  
engine4 ,s is the steam connection1 and 
,e the exhaust2 there are  two distinct 
sets of valves1 the steam s1 s'1 and the
 exhaust e1 e'1  operated independently 
of each other4 ,in their construction   

the valves may  be considered           
cylindrical plugs1 of which portions    
near the ports are cut  away to admit   
the steam and reduce the bearing        
surface2 the valves are  fitted on the  
lathe and the seats by boring4 ,the     
motion given to the valves  is rocking1 
but it will be observed that the valves 
are not firmly  connected to the rocking
 shaft or cylinder2 in the figure the   
valves are  shown shade lined1 and the  
shaft or stem plain2 in this way the    
valves are  not affected by the packing 
of the valve stem1 but always rest upon 
the  face of the ports4 ,in the figure  
the piston is just about to commence its
  outstroke1 the movement of the steam  
is supposed to be represented by the    
arrows2 the inner steam valve s1 and the
 outer exhaust e'1 are just  beginning  
to open4 ,it will be observed that the  
outer steam s' is fully  closed1 whilst 
the inner exhaust valve e is but barely 
so1 showing that  there has been a      
cut-off on the steam valve1 but no lead 

to the exhaust1  that it was left fully 
open till the completion of the stroke4 
,illustration3 ,fig4 #ga4    ,fig4 #ga  
is a side elevation of the cylinder1    
with the valve connections  with the    
governor4 ,s is the steam pipe2 s1 s'   
handles to the steam  valves1 and e1 e' 
to the exhaust valves1 shown in dotted  
line in fig4 #gj4  ,the handles to the  
exhaust valves are connected directly to
 a rocking plate  ,r1 to which motion is
 given by a connection x1 with an       
eccentric on the  engine shaft4 ,when   
once set1 therefore the movement of the 
exhaust valves  is constant1 and they   
will always be opened and closed at the 
same point of  the stroke4 ,connected   
with the rocking plate ,r1 and on       
opposite sides of  its centre1 the same 
as the exhaust valve connections1 there 
are two  levers1 vibrating on a centre  
c1 of which one only is shown1 as it    
covers  the other2 to the upper ends of 
these levers pawls are attached1 one end
 of  which rests on the stems or rods   

connected with the handles s1 s'1 of the
  steam valves2 on these stems there are
 notches against which the pawls        
strike1 and as the levers vibrate inward
 they push back the stems and  thereby  
open the valves1 and this continues for 
the whole length of the  inward motion  
of the levers1 or till the outer        
extremities of the pawls  come in       
contact with the end of the short lever 
l1 which1 pushing down  the outer end of
 the pawls1 relieves the stems at the   
other ends1 and the  valve stem returns 
to its place through the force of       
springs attached to  the outer          
extremities of the valve stems a1 are   
cylindrical guides to the  valve stems1 
at the inner extremities of which are   
air cushions4 ,the lever  l is connected
 directly with the governor4 ,as the    
balls rise1 they  depress the extremity1
 which comes in contact with the pawls  
sooner1 and  thereby shut the valves    
earlier2 and on the contrary when the   
balls are  depressed1 the valves remain 

open longer2 as the pawls come in       
contact with  the stems always at one   
point1 the steam valves open constantly1
 but are  closed at any point by the    
relief of the pawls1 according to the   
speed of  the governor4    ,fig4 #ga    
represents1 partly in section and partly
 in plan1 the cylinder1  steam chests1  
valves1 c41 of one of the ,woodruff     
,beach high pressure  ,engines1         
,wright's patent4    ,fig4 #gb          
represents1 in elevation1 the cam shaft1
 to the upper end of which1  not shown  
in the drawing1 is attached the ordinary
 centrifugal governor4  ,the cylinder1  
steam chests1 valves1 c41 being similar 
to those of other  engines1 need no     
special notice2 but the cam for opening 
and closing the  steam valves1 fig4 #gb1
 requires particular attention1 as it   
embodies a  beautiful and simple device 
for cutting off the steam with certainty
 at any  part of the stroke1 the motion 
being produced automatically by the     
action  of the governor on this cam1    

throwing it more or less out of centre  
with  the spindle of the governor1 as   
the rotation of the balls is less or    
more  rapid1 the eccentricity of the cam
 determining the amount of steam        
admitted  to the working cylinder of the
 engine4 ,to produce this effect the cam
 is  made as follows3    ,c is a hollow 
cylinder or shell1 with a part of one   
end formed into a cam  proper4          
,throughout the whole length of this    
piece1 upon the inside1 there  is a     
spiral groove cut to receive one end of 
a feather1 by which its pitch  or       
eccentricity is regulated4 ,c' is also a
 hollow cylinder or shell1 of  the same 
length and diameter as ,c1 with a       
similar spiral groove cut on  the       
inside1 the outside being perfectly     
smooth and plain1 upon which the  toe   
7t7 for closing the valves is fastened4 
,the inside piece consists of  two hubs 
,d1 ,d'1 eccentric with each other1 and 
made in one piece1 ,d  being turned to  
exactly fit the inside of the shell ,c1 

and ,d' to fit  the shell ,c'1 the hub  
,d' having a socket 7c7 into which the  
spindle  7s7 of the governor is screwed2
 the end 7d7 of the hub ,d forming a    
journal or bearing1 with a bevel wheel  
on its extremity to convey motion  from 
the crank-shaft gearing to the governor 
and cut-off4 ,there is a hole           
throughout the length of the inside hubs
 ,d and ,d'1 which is continued  through
 the spindle of the governor1 and       
contains the rod 7r7 that  connects the 
cam with the governor4 ,this hole is    
eccentric to the outside  surface of the
 hub ,d1 as well as to the shell ,c1 and
 concentric with  the hub ,d' and shell 
,c'1 and with the governor rod 7r74     
,the shell ,c and hub ,d1 and shell ,c' 
and hub ,d'1 are connected  together by 
feathers2 one piece of each feather is  
of a spiral form1 and  the other a      
straight or rectangular piece1 the two  
being connected together  by a stub on  
the rectangular piece1 which fits into a
 hole or bearing in  the other or spiral

 piece1 so that the latter can turn on  
the stub and  accommodate itself to the 
groove in which it has to work4 ,the    
spiral part  of each feather works in   
the spiral groove on the inside of its  
corresponding shell ,c and ,c'          
respectively1 and the rectangular pieces
  work in a straight groove cut in the  
hubs ,d and ,d'1 the inner parts of  the
 rectangular pieces being fastened to   
the governor rod 7r71 so that  the      
feathers are permanently connected with 
the governor4    ,the shell ,c' revolves
 inside of two yokes 7y7 and 7y'71 one  
attached  to each steam-valve toe1 7a7  
and 7a'7 respectively4    ,on the inside
 of each yoke1 and opposite to its      
valve-toe1 is a raised  piece1 against  
which the closing piece 7t7 on the shell
 7,c'7 acts to  close the valves4       
,this shell 7,c'71 as before noticed1   
has a spiral groove on its inside1      
similar in all respects to that in the  
cam-shell 7,c72 and being acted  upon in
 the same manner and through the same   

rod by the governor1 it is  evident that
 the closing piece 7t7 on its outside   
will always hold the  same relation to  
the opening toe on the lower or         
cam-shell 7,c72 and  whatever alteration
 is made in the one1 a corresponding    
alteration takes  place in the other1   
thereby insuring the closing of the     
valves at the  proper time at every     
point of the variation of the cut-off4  
,when the several pieces above described
 are put together1 the apparatus for    
opening and closing the valves and      
producing the cut-off is complete1 as   
shown in fig4 #gb1 and it operates as   
follows3    ,illustration3 ,fig4 #ga4   
,illustration3 ,fig4 #gb4      ,motion  
is communicated by gearing from the     
crank-shaft to the bevel wheel  on the  
piece 7d7 on the end of the hub ,d1 and 
is communicated to the  spindle of the  
governor1 which is screwed into the     
socket on ,d'4 ,as the  balls rise or   
fall1 through change of centrifugal     
force due to the  variation in the speed

 of rotation1 they raise or depress the 
governor-rod1  which passes through the 
spindle and the hubs ,d' and ,d1 and is 
attached  to the feathers1 thereby      
raising or depressing the feathers1     
which1 acting  on their respective      
spiral grooves1 instantly alters the    
lift of the cam on  the shell 7,c71 and 
brings the closing toe 7t7 on the shell 
7,c'7 into  proper position for closing1
 and so regulates the amount of steam   
admitted  to the cylinder4              
,illustration3 ,fig4 #ga4               
,consequently1 any speed may be selected
 at which the load of the engine is  to 
move1 and any variation from that will  
be instantly felt by the  governor1 and 
corrected by this simple and beautiful  
device4 ,there is no  jar in the working
 of the parts2 the feathers move        
noiselessly in their  grooves2 the      
governor rod moves up and down through  
the spindle and the  hubs ,d and ,d'1   
and can be regulated by hand to give any
 required  opening of the steam ports to

 suit the work to be done4 ,any change  
in the  amount of work will then alter  
the speed of the engine1 and so affect  
the  governor and cam1 as before said4  
,it is unnecessary to insist on the     
great economy attained by using steam   
with a well-regulated cut-off1 for      
practical men know now that the         
essential points of excellence in the   
steam engine are a good boiler1 which   
generates the greatest quantity of steam
 for the least consumption of fuel2     
and1 secondly1 a reliable cut-off1 which
 uses the steam to the best  advantage1 
by admitting the proper quantity for the
 work required4    ,,steam ,,fire       
,,engines4--,portable engines for the   
extinguishment of fires1 are  an        
,american invention1 and to ,messrs4    
,a4,b4  ,e4 ,latta1 of ,cincinnati1     
working on the right principles1 is due 
the credit which they claim in  their   
circular1 as follows3    ,we claim to be
 the original and first projectors of   
the first  successful steam fire engine 

in the world's history4 ,there have been
 many  attempts at making a machine of  
such construction as would answer to    
extinguish fires2 but none of them      
proved to be available in a sufficiently
  short space of time to warrant their  
use as a fire apparatus4 ,we hold that  
a steam fire engine should be of such   
nature as to be brought into            
requisition in as short a space of time 
as is necessary to get the machine  on  
the ground1 and the hose laid and ready 
to work3 that is1 supposing the  fire to
 be within one square of the place where
 the steamer is located4 ,the  object in
 locating a machine at any point is to  
protect that immediate  vicinity2 and it
 is therefore absolutely necessary to   
have it available in  the shortest space
 of time1 and that with unerring        
certainty4 ,we think that  reliability  
is of the greatest importance to the    
protection of a city from  fire1 as     
everything is dependent on the working  
of such apparatus in  time2 and for this

 reason no expense should be spared on  
this kind of  machinery4    ,fig4 #gc is
 a representation of one of the ,messrs4
 ,latta's fire engines1 of  which there 
are many of different classes1 according
 to the requirements2  they say that    
they can furnish engines as low as      
#a1jjj1 and have made some  for #aj1jjj4
    ,the first peculiar feature of this 
engine is the boiler2 it differs        
entirely from all boilers now in use4   
,illustration3 ,fig4 #gc4    ,the fire  
box or furnace is simply a square box or
 furnace of any required  dimensions2 it
 is nothing more than a water space     
surrounding the fire1  stay-bolted as   
all water spaces are4 ,it is made of    
boiler plate in the  usual manner4 ,the 
water space extends only #b_/c of the   
height1 the balance  being a single     
sheet4 ,the bottom of this fire box is  
crossed by grate bars  to support the   
fuel2 in its rear side are fire doors1  
inserted for firing4  ,the internal     
arrangements of the boiler are composed 

of a large number of  tubes1 lying      
across in a horizontal position1 put    
together in sections with  return bends 
resembling the coils for heating        
buildings4 ,these coils are of  small   
pipe 7say one inch in diameter71 and as 
numerous as may be necessary4  ,they    
give the required amount of steam4 ,they
 are secured to wrought-iron  plates at 
each end by rivets4 ,these plates lie   
close to the box1 and are  secured to   
it1 top and bottom4 ,these tubes are    
wrought iron1 firmly screwed  into the  
bends1 so as to prevent any possible    
breaking4    ,the box has a hole through
 both sheets1 in the same manner as a   
hollow  stay-bolt1 through which the    
coil pipe passes1 having no connection  
with  the box4 ,after passing into the  
box it divides into two pipes1 then     
subdivides into four1 and so on1 until  
its numbers equal the number of  coils  
in the box1 and to which each limb is   
attached4 ,the upper ends of  these     
coils are the same in number1 and are   

carried through at the top or  nearly   
the top of the box4 ,they then run down 
outside to the steam chamber1  or rather
 water space1 as the box is both steam  
chamber and water space4  ,these pipes  
empty their contents into the box1 steam
 and water1 as it may  come1 all        
together4 ,it will be observed that     
these coils of tube are  sufficiently   
separated to allow the fire to pass     
between them freely1 and  cover their   
whole surface4    ,the mode of operation
 of this boiler is this3 ,the fire box  
is filled #b_/c  full of water4 ,the    
coils are dry at starting2 the space for
 fuel being  filled with good wood1 the 
fire is lighted1 and in a few moments   
the  engineer moves his hand pump1 which
 takes its water from the box to which  
it is attached1 and forces it through   
the coils4 ,by this means steam is      
generated in from #c to #e minutes1 so  
as to start the engine4    ,it will be  
seen that the water performs a complete 
circuit2 it is taken  from the box and  

passed through the coils2 what is steam 
remains in the  steam chamber1 and what 
is not 7if any7 drops back into the box 
from where  it started4 ,hence it will  
be seen that a large surface is exposed 
to a  small quantity of water1 and in a 
way that it is entirely controllable4   
,all  the engineer has to do to         
surcharge his steam1 is to reduce the   
speed of  the pump 7which is independent
 of the main engine74 ,by raising the   
heat and  quantity of water1 any degree 
of elasticity can be given to the steam1
 and  that1 too1 with the least amount  
of waste heat in giving a natural draft4
  ,hence the great economy of this      
boiler4    ,the next feature of this    
engine is1 it has no wood work about it 
to perish  with the heat and roughness  
of the streets4 ,all the wheels are     
wrought  iron2 and1 as yet1 these are   
the only ones that have stood a steam   
fire  engine4 ,the frame is wrought     
iron2 truck1 on which the front wheel is
 hung1  wrought iron4 ,the axles are    

cast steel4 ,the engine and pump is a   
double-acting piston pump direct1       
without any rotary motion2 with a       
perfect balance valve1 it is balanced at
 all times1 and hence the engine        
remains quiet without blocking1 when at 
work4 ,the engine is mounted on  three  
wheels1 which enables it to be turned in
 a very short space4    ,many engines   
have been constructed by the ,messrs4   
,latta for the fire  companies1 of      
different cities1 and have been in      
successful competition  with other      
engines2 the farthest throw ever made by
 one of their  first-class engines was  
#caj feet from a #a-e_/h inch nozzle2   
steaming time1  starting from cold      
water1 #c-a_/b minutes4                 
,illustration3 ,fig4 #gd ,,amoskeag     
,,steam ,,fire ,,engine4    ,fig4 #gd is
 a representation of one class of steam 
fire engine1 as built by  the ,amoskeag 
,manufacturing ,company1 at ,manchester1
 ,n4,h4 ,the boiler is an  upright      
tubular boiler1 of a peculiar           

construction1 the patent right to  which
 is vested in the ,amoskeag             
,manufacturing ,company4 ,this boiler is
 very  simple in its combination1 and   
for safety1 strength1 durability1 and   
capacity for generating steam is        
unsurpassed4 ,no fan or artificial      
blower  is ever used or needed1 the     
natural draft of the boiler being always
  sufficient4 ,starting with cold water 
in the boiler1 a working head of steam  
can be generated in less than five      
minutes from the time of kindling the   
fire4 ,the engine ,amoskeag1 owned by   
the city of ,manchester1 has played  two
 streams in three minutes and forty     
seconds after touching the match1  at   
the same time drawing her own water4    
,the boilers are made and proved so  as 
to be safely run at a steam pressure of 
#adj to #aej lbs4 to the square  inch2  
but the engines are constructed so as to
 give the best streams at a  pressure of
 about #ajj lbs4 to the square inch1 and
 for service at fires a  steam pressure 

of about #fj lbs4 to the square inch is 
all that is required4    ,the various   
styles of engine are all vertical in    
their action1 and in all  the pumps and 
steam cylinders are firmly and directly 
fastened to the  boiler1 the steam      
cylinders being attached directly to the
 steam dome4 ,this  arrangement obviates
 the necessity of carrying steam to the 
cylinders  through pipes of considerable
 length1 and the machine has very little
  vibratory motion when in operation--so
 little that it is not necessary to     
block its wheels to keep it in its      
place1 or to take the weight off the    
springs before commencing work4    ,the 
pumps are placed on the engines as near 
the ground as they can be with  safety1 
and are arranged so as to attach the    
suction and leading hose to  either or  
both sides of the machine1 as may be    
most convenient or  desirable1 so that  
less difficulty will be found in placing
 an engine for  work1 and when required 
to draw its own water1 it has only to   

draw it the  shortest possible distance4
    ,each engine has two feed pumps for 
supplying the boiler1 and also a        
connection between the main forcing     
pumps and the boiler1 so that it can be 
supplied from that source if desirable4 
,the tank which carries the water  for  
supplying the boiler is so placed that  
the water in it is always above  the    
feed pumps1 an advantage that insures   
the almost certain working of  these    
pumps4 ,these pumps are of brass1 the   
best locomotive pattern1 and one  of    
them running with the engine1 when at   
work1 furnishes an ample supply of      
water to the boiler4    ,illustration3  
,fig4 #ge4    ,the engines are          
exceedingly portable2 they can be turned
 about or placed  for service in as     
contracted a space as any hand engine1  
and two good  horses will draw a        
first-class engine with the greatest    
ease1 carrying at  the same time water  
for the boiler1 a supply of fuel        
sufficient to run the  engine two hours1

 the driver1 the engineer1 and the      
fireman4    ,fig4 #ge is a              
representation of the class of steam    
fire engine built by  ,silsbee1         
,mynderse  ,co41 ,seneca ,falls1 ,n4 ,y4
 under ,holly's patent4    ,the boiler  
is vertical1 with vertical water tubes  
passing directly through  the fire4     
,these tubes are closed at the bottom   
and open at the top1 where  they pass   
through a water-tight plate1 and        
communicate with the water in  the      
boiler4 ,the arrangement of the tubes   
causes a constant current1 the  water   
rising on the outside of the tubes as   
they are heated1 and its place  being   
supplied by a current flowing downward  
through the tube to the  boiler4 ,the   
smoke and flame pass among the tubes up 
through flues4    ,both engine and pump 
are rotary1 and of the same type4 ,they 
consist  essentially of two elliptical  
rotary pistons1 cogged and working into 
one  another in an air-tight case4 ,the 
pistons fit close to the inside of the  

case1 and gear into each on the line of 
their conjugate diameters4 ,the  action 
is somewhat similar to the old-fashioned
 rotary pump1 consisting of  two cog    
wheels in gear with1 each other1 the    
spaces at the side of the case  being   
filled with water1 which at the centre  
are occupied by the teeth in  gear4 ,in 
,holly's pump1 instead of uniform teeth1
 and depending on the fit  of the teeth 
with the side of the case and with each 
other for the packing1  there are two   
large teeth in each piston opposite each
 other1 which have  slide pistons1 and  
intermediate with these large teeth are 
small cogs1  which continue the motion  
of the rotary pistons4 ,the machine     
works very  smoothly1 and performs the  
work necessary1 in ordinary service1    
under a  pressure of #ej to #fj lbs4    
,there are many other makers of fire    
engines in this country2 but sufficient 
examples are given to illustrate the    
class2 so successful have they been1    
that they are fast superseding hand     

engines1 even in the smaller cities4    
,under a paid department1 the following 
is1 in the city of ,boston1 ,mass41  the
 comparative cost of running the two    
kinds of engines1 viz43                 
,,steam ,,fire ,,engine4  #a            
engineer44444444444444444444444444444444
44444444444   #gbj #jj  #a              
fireman444444444444444444444444444444444
44444444444    #fjj #jj  #a             
driver4444444444444444444444444444444444
44444444444    #fjj #jj  #a foreman of  
hose444444444444444444444444444444444444
    #aej #jj  #h hosemen1 at #abe       
each444444444444444444444444444444      
#cge #jj  --                            
--------  #g                            
men4444444444444444444444444444444444444
44444444444 #b1dde #jj  ,keeping of #b  
horses4444444444444444444444444444444444
    #cae #jj                            
--------                                
,total4444444444444444444444444444444444
4444444 #b1gfj #jj                      
,,hand ,,engine4  #a                    

foreman444444444444444444444444444444444
44444444444   #aej #jj  #a assistant    
foreman444444444444444444444444444444444
4    #abe #jj  #a                       
clerk44444444444444444444444444444444444
44444444444    #abe #jj  #a             
steward444444444444444444444444444444444
44444444444    #abe #jj  #c leading     
hosemen1 at #abe                        
each4444444444444444444444    #cge #jj  
#cc men1 at #ajj                        
each444444444444444444444444444444444   
#c1cjj #jj  --                          
---------  #dj                          
men4444444444444444444444444444444444444
4444444444 #d1bjj #jj    ,here the      
engineer1 fireman1 and driver are       
constantly employed1 the hosemen  have  
other employment in the neighborhood1   
but all the company sleep in the  engine
 house4    ,in the city of ,manchester1 
,n4,h41 a steam fire engine company is  
composed of  fourteen men1 all told1 one
 of whom1 acting as driver and steward1 
is  constantly employed1 remaining at   

the engine house with a pair of horses  
always ready to run out with the engine 
in case of an alarm of fire4 ,the  other
 members of the company have other      
employments1 and turn out only on  an   
alarm of fire4                          
,,steam ,,fire ,,engines4  ,amoskcag1   
,expenditures444444444444444444444 #hfd 
#cb  ,fire ,king1                       
444444444444444444444  #hee #gh  ,e4,w4 
,harrington1                            
444444444444444444444  #dif #ji    ,the 
above expense includes pay of members1  
team expenses1 cost of gas1  wood1 coal1
 and all necessities incident to        
service4 ,the ,e4,w4 ,harrington  is a  
second-class engine1 stationed in the   
outskirts of the city1 and was  run     
cheaper from the fact that no horses    
were kept for it by the city4    ,a     
first-class hand-engine company is      
allowed to number1 all told1 fifty  men1
 and the members of the company are paid
 as follows3                            
,,first-,,class ,,hand-,,engine         

,,company4  #a                          
foreman444444444444444444444444444444444
444444444 #ce #jj  #a assistant         
foreman4444444444444444444444444444444  
#bh #jj  #a                             
clerk44444444444444444444444444444444444
44444444   #bh #jj  #a                  
steward444444444444444444444444444444444
4444444    #fh #jj  #df men1 at #ah     
each44444444444444444444444444444444    
#hbh #jj                                
--------  #ej men4                      
,total444444444444444444444444444444    
#ihg #jj    ,by this it will be seen1   
that in a city like ,manchester1 with   
from twenty  to twenty-five thousand    
inhabitants1 a first-class steam fire   
engine can be  run at an expense not to 
exceed that of a first-class hand       
engine1 while in  service it will do at 
least four times the work4 ,the cost of 
repairs is  found by experience to be no
 greater on the steam fire engines than 
on hand  engines4    ,the ,excavator1   
fig4 #gf1 is the invention of the late  

,mr4 ,otis1 an  application of the spoon
 dredging machine of the docks to       
railway purposes1  with very important  
modifications4 ,the machine consists of 
a strong truck1  ,a1 ,a1 mounted on     
railway wheels1 on which is placed the  
boiler ,c1 the  crane ,e1 and the       
requisite gearing4 ,the excavator or    
shovel1 ,d1 is a  box of wrought iron1  
with strong points in front to act as   
picks in  loosening the earth1 and its  
bottom hung by a hinge at d1 so that1 by
  detaching a catch1 it may fly open and
 discharge the material raised4 ,to     
operate the machine1 suppose the shovel 
,d to be in the position shown in  the  
cut2 it is lowered by the chains o1 o1  
and thrown forward or  backward1 if     
necessary1 by the drum ,b1 and handle   
,s1 till the picks in  the front of the 
shovel are brought in proper contact    
with the face of the  cut2 motion       
forward is now given to the shovel by   
the drum ,b and handle  ,s1 and at the  
same time it is raised by the chains o1 

o4 ,these two  motions can be so        
adjusted to each other1 as to give      
movement to the shovel  to enable it to 
loosen and scrape up a shovelful of     
earth4 ,the handle ,s  is now left free1
 and the shovel ,d is raised vertically 
by the chains  o1 o4 ,the crane is now  
turned round1 till the shovel comes over
 a rail  car on a side track2 the bottom
 of the shovel is opened1 and the dirt  
deposited in the car4 ,all these motions
 are performed by the aid of a steam    
engine1 and are controlled by a man who 
stands on a platform at f4              
,illustration3 ,fig #gf4    #fib4       
,q4--,having now described the most     
usual and approved forms of  engines    
applicable to numerous miscellaneous    
purposes for which a moderate  amount of
 steam power is required1 will you      
briefly recapitulate what  amount of    
work of different kinds an engine of a  
given power will perform1  so that any  
one desiring to employ an engine to     
perform a given amount of  work1 will be

 able to tell what the power of such    
engine should be8    ,a4--,it will of   
course be impossible to recapitulate all
 the purposes to  which engines are     
applicable1 or to specify for every case
 the amount of  power necessary for the 
accomplishment of a given amount of     
work2 but some  examples may be given   
which will be applicable to the bulk of 
the cases  occurring in practice4       
#fic4 ,q4--,beginning1 then1 with the   
power necessary for threshing1--a #d    
horse power engine1 with cylinder #f    
inches diameter1 pressure of steam #de  
lbs41 per square inch1 and making #adj  
revolutions per minute1 will thresh  out
 #dj quarters of wheat in #aj hours with
 a consumption of #c cwt4 of coals4     
,a4--,although this may be done1 it is  
probably too much to say that it can  be
 done on an average1 and about three    
fourths of a quarter of wheat per  horse
 power would probably be a nearer       
average4 ,the amount of power  consumed 
varies with the yield4    ,messrs4      

,barrett1 ,exall1 and ,andrewes give the
 following table as  illustrative of the
 work done1 and the fuel consumed by    
their portable  engines2 but this must  
be regarded as a maximum performance3-- 
,number of   ,weight of  ,quarters of   
,quantity of     ,quantity of  ,horse   
,power4  ,engine4   ,corn thrashed      
,coals consumed ,water required         
in #aj ,hours4  in #aj ,hours4   for #aj
 ,hours                                 
in ,gallons4                            
----------------------------------------
---------------------------             
,tons4 ,cwts4                   ,cwts4  
#d       #b     #j         #dj          
#c             #cfj        #e       #b  
#e         #ej            #d            
#chj        #f       #b    #aj          
#fj            #e             #dfj      
#g       #b    #ae         #gj          
#f             #edj        #h       #c  
#j         #hj            #g            
#fbj       #aj       #c    #aj          
#ajj            #i             #ghj     

----------------------------------------
-------------------------------    #fid4
 ,q4--,in speaking of horses power1 ,i  
suppose you mean indicator horse  power8
    ,a4--,yes2 or rather the dynamometer
 horse power1 which is the same1        
barring the friction of the engine4 ,at 
the shows of the ,royal ,agricultural   
,society1 the power actually exerted by 
the different engines is ascertained  by
 the application of a friction wheel or 
dynamometer4    #fie4 ,q4--,can you give
 any other examples of the power        
necessary for  grinding corn8           
,a4--,an engine exerting #bc-a_/c horses
 power by the indicator works two  pairs
 of flour stones of #d feet #h inches   
diameter1 two pairs of stones  grinding 
oatmeal of #d feet #h inches diameter1  
one dressing machine1 one  pair of      
fanners1 one dust screen1 and one       
sifting machine4 ,one of the flour      
stones makes #he1 and the other #ij     
revolutions in the minute4 ,one of the  
oatmeal stones makes #abj1 and the other

 #adj revolutions in the minute4 ,to    
take another case3--,an engine exerting 
#bf-a_/b indicator horses power works   
two pairs of flour stones1 one dressing 
machine1 two pairs of stones  grinding  
oatmeal1 and one pair of shelling       
stones4 ,the flour stones1 one  pair of 
the oatmeal stones1 and shelling stones1
 are #d feet #h inches  diameter4 ,the  
diameter of the other pair of oatmeal   
stones is #c feet #h  inches4 ,the      
length of the cylinder of the dressing  
machine is #g feet #f  inches4 ,the     
flour stones make #hg revolutions in the
 minute1 and the larger  oatmeal stone  
#aaa revolutions1 but the smaller       
oatmeal stone and the  shelling stone   
revolve faster than this4 ,at the time  
the indicator diagram  was taken1 each  
pair of flour stones was grinding at the
 rate of #e bushels  an hour2 each pair 
of oatmeal stones about #bd bushels an  
hour2 and the  shelling stones were     
shelling at the rate of about #ed       
bushels an hour4 ,the  fanners and      

screen were also in operation4    #fif4 
,q4--,have you any other case to        
enumerate8    ,a4--,i may mention one in
 which the power of the same engine was 
increased  by giving it a larger supply 
of steam4 ,the engine when working with 
#h4fe  horses power1 gives motion to one
 pair of oatmeal stones of #d feet #f   
inches  diameter1 and one pair of flour 
stones #d feet #h inches diameter4 ,the 
oatmeal stone makes #ajj revolutions in 
the minute1 and the flour stone #hi4    
,the oatmeal stones grind about #cf     
bushels in the hour1 and the flour      
stones  #e bushels in the hour4 ,the    
engine when working to #ab horses power 
drives  one pair of flour stones1 #d    
feet #h inches diameter1 at #hi         
revolutions per  minute and one pair of 
stones of the same diameter at #aje     
revolutions1  grinding beans for cattle4
 ,the flour mill stones with this       
proportion of  power1 being more largely
 fed1 ground #f bushels per hour1 and   
the other  stones also ground #f bushels

 per hour4 ,when the power was increased
 to #ah  horses1 and the engine was     
burdened in addition with a dressing    
machine  having a cylinder of #ai inches
 diameter1 the speed of the flour stone 
fell  to #he1 and of the beans stone to 
#ajj revolutions per minute1 and the    
yield  was also reduced4 ,the dressing  
machine dressed #bd bushels per hour4   
#fig4 ,q4--,what is the power necessary 
to work a sugar mill such as is used  to
 press the juice from canes in the ,west
 ,indies8    ,a4--,twenty horses power  
will work a sugar mill having rollers   
about #e  feet long and #bh inches      
diameter2 the rollers making #b-a_/c    
turns in a  minute4 ,if the rollers be  
#bf inches diameter and #d-a_/b feet    
long1 #ah horses  power will suffice to 
work them at the same speed1 and #af    
horses power if  the length be reduced  
to #c feet #h inches4 #ab horses power  
will be required  to work a sugar mill  
with rollers #bd inches diameter and #d 
feet #b inches  long2 and #aj horses    

power will suffice if the rollers be #c 
feet #aj inches  long and #bc inches    
diameter4 ,the speed of the surface of  
sugar mill rollers  should not be       
greater than #af feet per minute1 to    
allow time for the canes  to part with  
their juice4 ,in the old mills the speed
 was invariably too  great4 ,the        
quantity of juice expressed will not be 
increased by increasing  the speed of   
the rollers1 but more of the juice will 
pass away in the  begass or woody refuse
 of the cane4    #fih4 ,q4--,what is the
 amount of power necessary to drive     
cotton mills8    ,a4--,an indicator or  
actual horse power will drive #cje hand 
mule spindles1  with proportion of      
preparing machinery for the same2 or    
#bcj self-acting  mule spindles with    
preparation2 or #ajd throstle spindles  
with preparation2  or #aj-a_/b power    
looms with common sizing4 ,the throstles
 referred to are the  common throstles  
spinning #cd's twist for power loom     
weaving1 and the  spindles make #djjj   

turns per minute4 ,the self-acting mules
 are ,robert's1  about one half spinning
 #cf's weft1 and spindles revolving     
#dhjj turns per  minute2 and the other  
half spinning #cf's twist1 with the     
spindles revolving  #ebjj times per     
minute4 ,half the hand mules were       
spinning #cf's weft1 at #dgjj           
revolutions1 and the other half #cf's   
twist at #ejjj revolutions per minute4  
,the average breadth of the looms was   
#cg inches1 weaving #cg inch cloth1     
making #abc picks per minute1--all      
common calicoes about #fj reed1         
,stockport  count1 and #fh picks to the 
inch4 ,to take another example in the   
case of a  mill for twisting cotton yarn
 into thread3--,in this mill there are  
#bg  frames with #if common throstle    
spindles in each1 making in all #beib   
spindles4 ,the spindles turn #bbjj times
 in a minute2 the bobbins are #a-g_/h   
inches diameter1 and the part which     
holds the thread is #b-c_/af inches     
long4  ,in addition to the twisting     

frames the steam engine works #d turning
 lathes1  #c polishing lathes1 #b       
,american machines for turning small    
bobbins1 two  circular saws1 one of #bb 
and the other of #ad inches diameter1   
and #bd bobbin  heads or machines for   
filling the bobbins with finished       
thread4 ,the power  required to drive   
the whole of this machinery is #bh-a_/b 
horses4 ,when all  the machinery except 
the spindles is thrown off1 the power   
required is #ba  horses1 so that #beib1 
the total number of spindles1 divided by
 #ba1 the  total power1 is the number of
 twisting spindles worked by each actual
 horse  power4 ,the number is #abb4hd4  
#fii4 ,q4--,what work will be done by a 
given engine in sawing timber1  pressing
 cotton1 blowing furnaces1 driving      
piles1 and dredging earth out of        
rivers8    ,a4--,a high pressure        
cylinder #aj inches diameter1 #d feet   
stroke1 making #ce  revolutions with    
steam of #ij to #ajj lbs4 on the square 
inch1 supplied by  three cylindrical    

boilers #cj inches diameter and #bj feet
 long1 works two  vertical saws of #cd  
inches stroke1 which are capable of     
cutting #cj feet of  yellow pine1 #ah   
inches deep1 in the minute4 ,a high     
pressure cylinder #ad  inches diameter  
and #d feet stroke1 making #fj strokes  
per minute with steam  of #dj lbs4 on   
the square inch1 supplied by three      
cylindrical boilers  without flues1 #cj 
inches diameter and #bf feet long1 with 
#cb square feet of  grate surface1 works
 four cotton presses geared #f to #a1   
with two screws in  each1 of #g-a_/b    
inches diameter and #a-e_/h pitch1 which
 presses will screw  #ajjj bales of     
cotton in the twelve hours4 ,also one   
high pressure cylinder  of #aj inches   
diameter and #c feet stroke1 making #de 
to #fj revolutions per  minute1 with    
steam of #de to #ej lbs4 per square     
inch1 with two hydraulic  presses having
 #ac inch rams of #da feet stroke1 and  
force pumps #b inches  diameter and #f  
inches stroke1 presses #cj bales of     

cotton per hour4 ,one  condensing engine
 with cylinder #ef inches diameter1 #aj 
feet stroke1 and  making #ae strokes per
 minute with steam of #fj lbs4 pressure 
per square  inch1 cut off at #a_/dth of 
the stroke1 supplied by six boilers1    
each #e feet  diameter1 and #bd feet    
long1 with a #bb-;inch double-return    
flue in each1 and  #aih square feet of  
fire grate1 works a blast cylinder of   
#abf inches  diameter1 and #aj feet     
stroke1 at #ae strokes per minute4 ,the 
pressure of the  blast is #d to #e lbs4 
per square inch2 the area of pipes #bcjj
 square inches1  and the engine blows   
four furnaces of #ad feet diameter1 each
 making #ajj  tons of pig iron per week4
 ,two high pressure cylinders1 each of  
#f inches  diameter and #ah inches      
stroke1 making #fj to #hj strokes per   
minute1 with  steam of #fj ,lbs4 per    
square inch1 lift two rams1 each        
weighing #ajjj lbs41  five times in a   
minute1 the leaders for the lift being  
#bd feet long4 ,one  high pressure      

cylinder of #ab inches diameter and #e  
feet stroke1 making #bj  strokes per    
minute1 with steam of #fj to #gj lbs4   
pressure per square inch1  lifts #f     
buckets full of dredging per minute from
 a depth of #cj feet below  the water1  
or lifts #aj buckets full of mud per    
minute from a depth of #ah  feet below  
the water4          ,,chapter ,,xii4    
,,manufacture ,,and ,,management ,,of   
,,steam ,,engines4      ,,construction  
,,of ,,engines4    #gjj4 ,q4--,what are 
the qualities which should be possessed 
by the iron of  which the cylinder of   
steam engines are made8    ,a4--,the    
general ambition in making cylinders is 
to make them sound and  hard2 but it is 
expedient also to make them tough1 so as
 to approach as  nearly as possible to  
the state of malleable iron4 ,this may  
be done by  mixing in the furnace as    
many different kinds of iron as         
possible2 and it  may be set down as a  
general rule in iron founding1 that the 
greater the  number of the kinds of     

metal entering into the composition of  
any casting1  the denser and tougher it 
will be4 ,the constituent atoms of the  
different  kinds of iron appear to be of
 different sizes1 and the mixture of    
different  kinds maintains the          
toughness1 while it adds to the density 
and cohesive  power4 ,hot blast iron was
 at one time generally believed to be   
weaker than  cold blast iron1 but it is 
now questioned whether it is not the    
stronger of  the two4 ,the cohesive     
strength of unmixed iron is not in      
proportion to its  specific gravity1 and
 its elasticity and power to resist     
shocks appear to  become greater as the 
specific gravity becomes less4 ,nos4 #c 
and #d are the  strongest irons4 ,in    
most cases1 iron melted in a cupola is  
not so strong as  when remelted in an   
air furnace1 and when run into green    
sand it is not  reckoned so strong as   
when run into dry sand1 or loam4 ,the   
quality of the  fuel1 and even the state
 of the weather1 exerts an influence on 

the quality  of the iron3 smelting      
furnaces1 on the cold blast principle1  
have long been  known to yield better   
iron in winter than in summer1 probably 
from the  existence of less moisture in 
the air2 and it would probably be found 
to  accomplish an improvement in the    
quality of the iron if the blast were   
made  to pass through a vessel          
containing muriate of lime1 by which the
 moisture  of the air would be          
extracted4 ,the expense of such a       
preparation would not  be considerable1 
as1 by subsequent evaporation1 the salt 
might be used over  and over again for  
the same purpose4    #gja4 ,q4--,will   
you explain the process of casting      
cylinders8    ,a4--,the mould into which
 the metal is poured is built up of     
bricks and  loam1 the loam being clay   
and sand ground together in a mill1 with
 the  addition of a little horse-dung to
 give it a fibrous structure and prevent
  cracks4 ,the loam board1 by which the 
circle of the cylinder is to be swept1  

is attached to an upright iron bar1 at  
the distance of the radius of the       
cylinder1 and a cylindrical shell of    
brick is built up1 which is plastered   
on the inside with loam1 and made quite 
smooth by traversing the  perpendicular 
loam board round it4 ,a core is then    
formed in a similar  manner1 but so much
 smaller as to leave a space between the
 shell and the  core equal to the       
thickness of the cylinder1 and into this
 space the melted  metal is poured4     
,whatever nozzles or projections are    
required upon the  cylinder1 must be    
formed by means of wooden patterns1     
which are built into  the shell1 and    
subsequently withdrawn2 but where a     
number of cylinders of  the same kind   
are required1 it is advisable to make   
these patterns of iron1  which will not 
be liable to warp or twist while the    
loam is being dried4  ,before the iron  
is cast into the mould1 the interior of 
the mould must be  covered with finely  
powdered charcoal--or blackening1 as it 

is technically  termed2 and the secret  
of making finely skinned castings lies  
in using  plenty of blackening4 ,in loam
 and dry sand castings the charcoal     
should be  mixed with thick clay water1 
and applied until it is an eighth of an 
inch  thick1 or more2 the surface should
 be then very carefully smoothed or     
sleeked1 and if the metal has been      
judiciously mixed1 and the mould        
thoroughly dried1 the casting is sure to
 be a fine one4 ,dry sand and loam      
castings should be1 as much as possible1
 made in boxes2 the moulds may  thereby 
be more rapidly and more effectually    
dried1 and better castings  will be got 
with a less expense4    #gjb4 ,q4--,will
 you explain the next operation which a 
cylinder undergoes8    ,a4--,the next   
stage is the boring2 and in boring      
cylinders of #gd inches  diameter1 the  
boring bar must move so as to make one  
revolution in about  #d-a_/b minutes1 at
 which speed the cutters will move at   
the rate of about  #e feet per minute4  

,in boring brass1 the speed must be     
slower2 the common  rate at which the   
tool moves in boring brass air pumps is 
about #c feet per  minute4 ,if this     
speed be materially exceeded the tool   
will be spoiled1 and  the pump made     
taper4 ,the speed proper for boring a   
cylinder will answer for  boring the    
brass air pump of the same engine4 ,a   
brass air pump of #cf-a_/b  inches      
diameter requires the bar to make one   
turn in about three minutes1  which is  
also the speed proper for a cylinder #fj
 inches in diameter4 ,to  bore a brass  
air pump #cf-a_/b inches in diameter    
requires a week1 an iron  one requires  
#dh hours1 and a copper one #bd hours4  
,in turning a malleable  iron shaft     
#ab-c_/d inches in diameter1 the shaft  
should make about five  turns per       
minute1 which is equivalent to a speed  
in the tool of about #af  feet per      
minute2 but this speed may be exceeded  
if soap and water be  plentifully run on
 the point of the tool4 ,a boring mill1 

of which the speed  may be varied from  
one turn in six minutes to twenty-five  
turns in one  minute1 will be suitable  
for all ordinary wants that can occur in
 practice4    #gjc4 ,q4--,are there any 
precautions necessary to be observed in 
order that  the boring may be truly     
effected8    ,a4--,in fixing a cylinder 
into the boring mill1 great care must be
 taken  that it is not screwed down     
unequally2 and indeed it will be        
impossible to  bore a large cylinder in 
a horizontal mill without being oval1   
unless the  cylinder be carefully gauged
 when standing on end1 and be set up by 
screws  when laid in the mill until it  
again assumes its original form4 ,a     
large  cylinder will inevitably become  
oval if laid upon its side2 and if while
  under the tension due to its own      
weight it be bored round1 it will become
  oval again when set upon end4 ,if the 
bottom be cast in1 the cylinder will  be
 probably found to be round at one end  
and oval at the other1 unless a         

vertical boring mill be employed1 or the
 precautions here suggested be  adopted4
    #gjd4 ,q4--,does the boring tool    
make the cylinder sufficiently smooth   
for  the reception of the piston8       
,a4--,many engine makers give no other  
finish to their cylinders2 but  ,messrs4
 ,penn grind their cylinders after they 
are bored1 by laying them on  their     
side1 and rubbing a piece of lead1 with 
a cross iron handle like that  of a     
rolling stone1 and smeared with emery   
and oil1 backward and forward--  the    
cylinder being gradually turned round so
 as to subject every part  successively 
to the operation4 ,the lead by which    
this grinding is  accomplished is cast  
in the ,cylinder1 whereby it is formed  
of the right  curve2 but the part of the
 cylinder in which it is cast should be 
previously heated by a hot iron1 else   
the metal may be cracked by the  sudden 
heat4    #gje4 ,q4--,how are the parts  
of a piston fitted together so as to be 
perfectly steam tight8    ,a4--,the old 

practice was to depend chiefly upon     
grinding as the means of  making the    
rings tight upon the piston or upon one 
another2 but scraping is  now chiefly   
relied on4 ,some makers1 however1 finish
 their steam surfaces by  grinding them 
with powdered ,turkey stone and oil4 ,a 
slight grinding1 or  polishing1 with    
powdered ,turkey stone and oil1 appears 
to be expedient in  ordinary cases1 and 
may be conveniently accomplished by     
setting the piston  on a revolving      
table1 and holding the ring stationary  
by a cross piece of  wood while the     
table turns round4 ,pieces of wood may  
be interposed between  the ring and the 
body of the piston1 to keep the ring    
nearly in its right  position2 but these
 pieces of wood should be fitted so     
loosely as to give  some side play1 else
 the disposition would arise to wear the
 flange of the  piston into a groove4   
#gjf4 ,q4--,what kind of tool is used   
for finishing surfaces by scraping8     
,a4--,a flat file bent1 and sharpened at

 the end1 makes an eligible scraper  for
 the first stages2 or a flat file       
sharpened at the end and used like a    
chisel for wood4 ,a three-cornered file1
 sharpened at all the corners1 is  the  
best instrument for finishing the       
operation4 ,the scraping tool should  be
 of the best steel1 and should be       
carefully sharpened at short intervals  
on a ,turkey stone1 so as to maintain a 
fine edge4    #gjg4 ,q4--,will you      
explain the method of fitting together  
the valve and  cylinder faces8          
,a4--,both faces must first be planed1  
then filed according to the  indications
 of a metallic straight edge1 and       
subsequently of a thick  metallic face  
plate1 and finally scraped very         
carefully until the face  plate bears   
equally all over the surface4 ,in       
planing any surface1 the  catches which 
retain the surface on the planing       
machine should be relaxed  previously to
 the last cut1 to obviate distortion    
from springing4 ,to  ascertain1 whether 

the face plate bears equally1 smear it  
over with a  little red ochre and oil1  
and move the face plate slightly1 which 
will fix  the color upon the prominent  
points4 ,this operation is to be        
repeated  frequently2 and as the work   
advances1 the quantity of coloring      
matter is to  be diminished1 until      
finally it is spread over the face plate
 in a thin  film1 which only dims the   
brightness of the plate4 ,the surfaces  
at this  stage must be rubbed firmly    
together to make the points of contact  
visible1  and the higher points will    
become slightly clouded1 while the other
 parts  are left more or less in shade4 
,if too small a quantity of coloring    
matter  be used at first1 it will be    
difficult to form a just conception of  
the  general state of the surface1 as   
the prominent points will alone be      
indicated1 whereas the use of a large   
quantity of coloring matter in the      
latter stages would destroy the delicacy
 of the test the face plate  affords4   

,the number of bearing points which it  
is desirable to establish on  the       
surface of the work1 depends on the use 
to which the surface is to be  applied2 
but whether it is to be finished with   
great elaboration1 or  otherwise1 the   
bearing points should be distributed    
equally over the  surface4 ,face plates1
 or planometers1 as they are sometimes  
termed1 are  supplied by most of the    
makers of engineering tools4 ,every     
factory should  be abundantly supplied  
with them1 and also with steel straight 
edges2 and  there should be a master    
face plate1 and a master straight edge1 
for the  sole purpose of testing1 from  
time to time1 the accuracy of those in  
use4    #gjh4 ,q4--,is the operation of 
surfacing1 which you have described1    
necessary in the case of all slide      
valves8    ,a4--,yes2 and in fitting the
 faces of a ,d valve1 great care must1  
in  addition1 be taken that the valve is
 not made conical2 for unless the back  
be exactly parallel with the face1 it   

will be impossible to keep the  packing 
from being rapidly cut away4 ,when the  
valve is laid upon the face  plate1 the 
back must be made quite fair along the  
whole length1 by draw  filing1 according
 to the indications of a straight edge2 
and the distance  from the face to the  
extreme height of the back must be made 
identical at  each extremity4    #gji4  
,q4--,when you described the operation  
of boring the cylinder1 you  stated that
 the cylinder1 when laid upon its side1 
became oval2 will not  this change of   
figure distort the cylinder face8       
,a4--,it is not only in the boring of   
the cylinder that it is necessary to  be
 careful that there is no change of     
figure1 for it will be impossible to    
face the valves truly in the case of    
large cylinders1 unless the cylinder  be
 placed on end1 or internal props be    
introduced to prevent the collapse  due 
to the cylinder's weight4 ,it may be    
added1 that the change of figure is  not
 instantaneous1 but becomes greater     

after some continuance of the strain    
than it was at first1 so that in gauging
 a cylinder to ascertain the  difference
 of diameter when it is placed on its   
side1 it should have lain  some days    
upon its side to ensure the accuracy of 
the operation4    #gaj4 ,q4--,how is any
 flaw in the valve or cylinder face     
remedied8    ,a4--,should a hole occur  
either in the valve1 in the cylinder1 or
 any  other part where the surface      
requires to be smooth1 it may be plugged
 up  with a piece of cast iron1 as      
nearly as possible of the same texture4 
,bore  out the faulty part1 and         
afterward widen the hole with an        
eccentric drill1  so that it will be of 
the least diameter at the mouth4 ,the   
hole may go more  than half through the 
iron3 fit then a plug of cast iron      
roughly by filing1  and hammer it into  
the hole1 whereby the plug will become  
riveted in it1  and its surface may then
 be filed smooth4 ,square pieces may be 
let in after  the same fashion1 the hole

 being made dovetailed1 and the pieces  
thus  fitted will never come out4       
#gaa4 ,q4--,when cylinders are faced    
with brass1 how is the face attached to 
the cylinder8    ,a4--,brass faces are  
put upon valves or cylinders by means of
 small brass  screws tapped into the    
iron1 with conical necks for the        
retention of the  brass3 they are       
screwed by means of a square head1      
which1 when the screw is  in its place1 
is cut off and filed smooth4 ,in some   
cases the face is made  of extra        
thickness1 and a rim not so thick runs  
round it1 forming a step or  recess for 
the reception of brass rivets1 the heads
 of which are clear of  the face4       
#gab4 ,q4--,what is the best material   
for valve faces8    ,a4--,much trouble  
is experienced with every modification  
of valve face2  but cast iron working   
upon cast iron is1 perhaps1 the best    
combination yet  introduced4 ,a usual   
practice is to pin brass faces on the   
cylinder1  allowing the valve to retain 

its cast iron face4 ,some makers employ 
brass  valves1 and others pin brass on  
the valves1 leaving the cylinder with a 
cast iron face4 ,if brass valves are    
used1 it is advisable to plane out two  
grooves across the face1 and to fill    
them up with hard cast iron to prevent  
rutting4 ,speculum metal and steel have 
been tried for the cylinder faces1  but 
only with moderate success4 ,in some    
cases the brass gets into ruts2 but  the
 most prevalent affection is a          
degradation of the iron1 owing to the   
action of the steam1 and the face       
assuming a granular appearance1         
something  like loaf sugar4 ,this action
 shows itself only at particular spots1 
and  chiefly about the angles of the    
port or valve face4 ,at first the action
 is  slow2 but when once the steam has  
worked a passage for itself1 the cutting
  away becomes very rapid1 and1 in a    
short time1 it will be impossible to    
prevent the engine from heating when    
stopped1 owing to the leakage of steam  

through the valve into the condenser4   
,copper steam pipes seem to have some   
galvanic action on valve faces1 and     
malleable iron pipes have sometimes     
been substituted2 but they are speedily 
worn out by oxidation1 and the  scales  
of rust which are carried on by the     
steam scratch the valves and  cylinders1
 so that the use of copper pipes is the 
least evil4    #gac4 ,q4--,will you     
explain in what manner the joints of an 
engine are  made8    ,a4--,rust joints  
are not now much used in engines of any 
kind1 yet it is  necessary that the     
engineer should be acquainted with the  
manner of their  formation4 ,one ounce  
of sal-ammoniac in powder is mingled    
with #ah ounces or  a pound of borings  
of cast iron1 and a sufficiency of water
 is added to wet  the mixture           
thoroughly1 which should be done some   
hours before it is wanted  for use4     
,some persons add about half an ounce of
 flowers of brimstone to  the above     
proportions1 and a little sludge from   

the grindstone trough4 ,this  cement is 
caulked into the joints with a caulking 
iron1 about three  quarters of an inch  
wide and one quarter of an inch thick1  
and after the  caulking is finished the 
bolts of the joints may be tried to see 
if they  cannot be further tightened4   
,the skin of the iron must1 in all      
cases1 be  broken where a rust joint is 
to be made2 and1 if the place be greasy1
 the  surface must be well rubbed over  
with nitric acid1 and then washed with  
water1 till no grease remains4 ,the oil 
about engines has a tendency to  damage 
rust joints by recovering the oxide4    
,coppersmiths staunch the edges  of     
their plates and rivets by means of a   
cement formed of pounded  quicklime1    
with serum of blood1 or white of egg2   
and in copper boilers such  a substance 
may be useful in stopping the impalpable
 leaks which sometimes  occur1 though   
,roman1 cement appears to be nearly as  
effectual4    #gad4 ,q4--,will you      
explain the method of case hardening the

 parts of  engines8    ,a4--,the most   
common plan for case hardening consists 
in the insertion of  the articles to be 
operated upon among horn or leather     
cuttings1 hone dust1  or animal         
charcoal1 in an iron box provided with a
 tight lid1 which is then  put into a   
furnace for a period answerable to the  
depth of steel required4  ,in some cases
 the plan pursued by the gunsmiths may  
be employed with  convenience4 ,the     
article is inserted in a sheet iron case
 amid bone dust1  often not burned2 the 
lid of the box is tied on with wire1 and
 the joint  luted with clay2 the box is 
heated to redness as quickly as possible
 and  kept half an hour at a uniform    
heat3 its contents are then suddenly    
immersed in cold water4 ,the more       
unwieldy portions of an engine may be   
case  hardened by prussiate of potash--a
 salt made from animal substances1      
composed of two atoms of carbon and one 
of nitrogen1 and which operates on  the 
same principle as the charcoal4 ,the    

iron is heated in the fire to a  dull   
red heat1 and the salt is either        
sprinkled upon it or rubbed on in a     
lump1 or the iron is rubbed in the salt 
in powder4 ,the iron is then  returned  
to the fire for a few minutes1 and      
finally immersed in water4 ,by  some    
persons the salt is supposed to act     
unequally1 as if there were greasy      
spots upon the iron which the salt      
refused to touch1 and the effect under  
any circumstances is exceedingly        
superficial2 nevertheless1 upon all     
parts  not exposed to wear1 a sufficient
 coating of steel may be obtained by    
this  process4    #gae4 ,q4--,what kind 
of iron is most suitable for the working
 parts of an  engine8    ,a4--,in the   
malleable iron work of engines scrap    
iron has long been used1  and considered
 preferable to other kinds2 but if the  
parts are to be case  hardened1 as is   
now the usual practice1 the use of scrap
 iron is to be  reprehended1 as it is   
almost sure to make the parts twist in  

the case  hardening process4 ,in case   
hardening1 iron absorbs carbon1 which   
causes it  to swell2 and as some kinds  
of iron have a greater capacity for     
carbon than  other kinds1 in case       
hardening they will swell more1 and any 
such unequal  enlargement in the        
constituent portions of a piece of iron 
will cause it to  change its figure4 ,in
 some cases1 case hardening has caused  
such a twisting  of the parts of an     
engine1 that they could not afterward be
 fitted  together2 it is preferable1    
therefore1 to make such parts as are to 
be case  hardened to any considerable   
depth of ,lowmoor1 ,bowling1 or ,indian 
iron1  which being homogeneous will     
absorb carbon equally1 and will not     
twist4    #gaf4 ,q4--,what is the       
composition of the brass used for engine
 bearings8    ,a4--,the brass bearings  
of an engine are composed principally of
 copper  and tin4 ,a very good brass for
 steam engine bearings consists of old  
copper  #aab lbs41 tin #ab-a_/b lbs41   

zinc #b or #c oz42 and if new tile      
copper be used1  there should be #ac    
lbs4 of tin instead of #ab-a_/b lbs4 ,a 
tough brass for  engine work consists of
 #a-a_/b lb4 tin1 #a-a_/b lb4 zinc1 and 
#aj lbs4 copper2  a brass for heavy     
bearings1 #b-a_/b oz4 tin1 #a_/b oz4    
zinc1 and #a lb4 copper4  ,there is a   
great difference in the length of time  
brasses wear1 as made by  different     
manufacturers2 but the difference arises
 as much from a different  quantity of  
surface1 as from a varying composition  
of the metal4 ,brasses  should always be
 made strong and thick1 as when thin    
they collapse upon the  bearing and     
increase the friction and the wear4     
#gag4 ,q4--,how is ,babbitt's metal for 
lining the bushes of machinery          
compounded8    ,a4--,babbitt's patent   
lining metal for bushes has been largely
 employed in  the bushes of locomotive  
axles and other machinery3 it is        
composed of #a lb4  of copper1 #a lb4   
regulus of antimony1 and #aj lbs4 of    

tin1 or other similar  proportions1 the 
presence of tin being the only material 
condition4 ,the  copper is first melted1
 then the antimony is added1 with a     
small proportion  of tin-charcoal being 
strewed over the surface of the metal in
 the crucible  to prevent oxidation4    
,the bush or article to be lined1 having
 been cast  with a recess for the soft  
metal1 is to be fitted to an iron mould1
 formed  of the shape and size of the   
bearing or journal1 allowing a little in
 size  for the shrinkage4 ,drill a hole 
for the reception of the soft metal1 say
  #a_/b to #c_/d inch diameter1 wash the
 parts not to be tinned with a clay wash
  to prevent the adhesion of the tin1   
wet the part to be tinned with alcohol1 
and sprinkle fine sal-ammoniac upon it2 
heat the article until fumes arise  from
 the ammonia1 and immerse it in a kettle
 of ,banca tin1 care being taken  to    
prevent oxidation4 ,when sufficiently   
tinned1 the bush should be soaked  in   
water1 to take off any particles of     

ammonia that may remain upon it1 as  the
 ammonia would cause the metal to blow4 
,wash with pipe clay1 and dry2  then    
heat the bush to the melting point of   
tin1 wipe it clean1 and pour in  the    
metal1 giving it sufficient head as it  
cools2 the bush should then be  scoured 
with fine sand1 to take off any dirt    
that may remain upon it1 and  it is then
 fit for use4 ,this metal wears for a   
longer time than ordinary  gun metal1   
and its use is attended with very little
 friction4 ,if the  bearing heats1      
however1 from the stopping of the oil   
hole or otherwise1 the  metal will be   
melted out4 ,a metallic grease1         
containing particles of tin in  the     
state of an impalpable powder1 would    
probably be preferable to the  lining of
 metal just described4    #gah4         
,q4--,can you state the composition of  
any other alloys that are used  in      
engine work8    ,a4--,the ordinary range
 of good yellow brass that files and    
turns well1 is  about #d-a_/b to #i     

ounces of zinc to the pound of copper4  
,flanges to stand  brazing may be made  
of copper #a lb41 zinc #a_/b oz41 lead  
#c_/h oz4 ,brazing  solders when stated 
in the order of their hardness          
are3-three parts copper  and one part   
zinc 7very hard71 eight parts brass and 
one part zinc 7hard71  six parts brass1 
one part tin1 and one part zinc 7soft72 
a very common  solder for iron1 copper1 
and brass1 consists of nearly equal     
parts of  copper and zinc4 ,muntz's     
metal consists of forty parts zinc and  
sixty of  copper2 any proportions       
between the extremes of fifty parts of  
zinc and  fifty parts copper1 and       
thirty-seven zinc and sixty-three       
copper1 will roll  and work at a red    
heat1 but forty zinc to sixty copper are
 the proportions  preferred4 ,bell      
metal1 such as is used for large bells1 
consists of #d-a_/b  ounces to #e ounces
 of tin to the pound of copper2 speculum
 metal consists  of from #g-a_/b ounces 
to #h-a_/b ounces of tin to the pound of

 copper4        ,,erection ,,of         
,,engines4    #gai4 ,q4--,will you      
explain the operation of erecting a pair
 of side lever  engines in the workshop8
    ,a4--,in beginning the erection of  
side lever marine engines in the        
workshop1  the first step is to level   
the bed plate lengthways and across1 and
 strike  a line up the centre1 as near  
as possible in the middle1 which indent 
with  a chisel in various places1 so    
that it may at any time be easily found 
again4 ,strike another line at right    
angles with this1 either at the         
cylinder or crank centre1 by drawing a  
perpendicular in the usual manner4  ,lay
 the other sole plate alongside at the  
right distance1 and strike a line  at   
the cylinder or crank centre of it also1
 shifting either sole plate a  little   
endways until these two transverse lines
 come into the same line1  which may be 
ascertained by applying a straight edge 
across the two sole  plates4 ,strike the
 rest of the centres across1 and drive a

 pin into each  corner of each sole     
plate1 which file down level1 so as to  
serve for points  of reference at any   
future stage2 next1 try the cylinder1 or
 plumb it on  the inside roughly1 and   
see how it is for height1 in order to   
ascertain  whether much will be required
 to be chipped off the bottom1 or       
whether more  requires to be chipped off
 the one side than the other4 ,chip the 
cylinder  bottom fair2 set it in its    
place1 plumb the cylinder very carefully
 with a  straight edge and silk thread1 
and scribe it so as to bring the        
cylinder  mouth to the right height1    
then chip the sole plate to suit that   
height4  ,the cylinder must then be     
tried on again1 and the parts filed     
wherever they  bear hard1 until the     
whole surface is well fitted4 ,next1    
chip the place for  the framing2 set up 
the framing1 and scribe the horizontal  
part of the jaw  with the scriber used  
for the bottom of the cylinder1 the     
upright part  being set to suit the     

shaft centres1 and the angular flange of
 cylinder1  where the stay is attached1 
having been previously chipped plumb and
 level4  ,the stake wedges with which   
the framing is set up preparatorily to  
the  operation of scribing1 must be set 
so as to support equally the            
superincumbent weight1 else the framing 
will spring from resting unequally1  and
 it will be altogether impossible to fit
 it well4 ,these directions  obviously  
refer exclusively to the old description
 of side lever engine  with cast iron   
framing2 but there is more art in       
erecting an engine of that  kind with   
accuracy1 than in erecting one of the   
direct action engines1  where it is     
chiefly turned or bored surfaces that   
have to be dealt with4    #gbj4         
,q4--,how do you lay out the positions  
of the centres of a side lever  engine8 
,a4--,in fixing the positions of the    
centres in side lever engines1 it       
appears to be the most convenient way to
 begin with the main centre4 ,the       

height of the centre of the cross head  
at half stroke above the plane of  the  
main centre is fixed by the drawing of  
the engine1 which gives the  distance   
from the centre of cross head at half   
stroke to the flange of the  cylinder2  
and from thence it is easy to find the  
perpendicular distance  from the        
cylinder flange to the plane of the main
 centre1 merely by putting  a straight  
edge along level1 from the position of  
the main centre to the  cylinder1 and   
measuring from the cylinder flauge down 
to it1 raising or  lowering the straight
 edge until it rests at the proper      
measurement4 ,the  main centre is in    
that plane1 and the fore and aft        
position is to be found  by plumbing up 
from the centre line on the sole plate4 
,to find the paddle  shaft centre1 plumb
 up from the centre line marked on the  
edge of the sole  plate1 and on this    
line lay off from the plane of the main 
centre the  length of the connecting    
rod1 if that length be already fixed1 or

 otherwise  the height fixed in the     
drawing of the paddle shaft above the   
main centre4  ,to fix the centre for the
 parallel motion shaft1 when the        
parallel bars are  connected with the   
cross head1 lay off from the plane of   
main centre the  length of the parallel 
bar from the centre of the cylinder1    
deduct the  length of the radius crank1 
and plumb up the central line of motion 
shaft2  lay off on this line1 measuring 
from the plane of main centre1 the      
length  of the side rod2 this gives the 
centre of parallel motion shaft when the
  radius bars join the cross head1 as is
 the preferable practice where  parallel
 motions are used4 ,the length of the   
connecting rod is the distance  from the
 centre of the beam when level1 or the  
plane of the main centre1 to  the centre
 of the paddle shaft4 ,the length of the
 side rods is the distance  from the    
centre line of the beam when level1 to  
the centre of the cross  head when the  
piston is at half stroke4 ,the length of

 the radius rods of  the parallel motion
 is the distance from the point of      
attachment on the  cross head or side   
rod1 when the piston is at half stroke1 
to the extremity  of the radius crank   
when the crank is horizontal2 or in     
engines with the  parallel motion       
attached to the cross head1 it is the   
distance from the  centre of the pin of 
the radius crank when horizontal to the 
centre of the  cylinder4 ,having fixed  
the centre of the parallel motion shaft 
in the  manner just described1 it only  
remains to put the parts together when  
the  motion is attached to the cross    
head2 but when the motion is attached to
  the side rod1 the end of the parallel 
bar must not move in a perpendicular    
line1 but in an arc1 the versed sine of 
which bears the same ratio to that  of  
the side lever1 that the distance from  
the top of the side rod to the  point of
 attachment bears to the total length of
 the side rod4    #gba4 ,q4--,how do you
 ascertain the accuracy of the parallel 

motion8    ,a4--,the parallel motion    
when put in its place should be tested  
by raising  and lowering the piston by  
means of the crane4 ,first1 set the     
beams level1  and shift in or out the   
motion shaft plummer blocks or bearings1
 until the  piston rod is upright4 ,then
 move the piston to the two extremes of 
its  motion4 ,if at both ends the cross 
head is thrown too much out1 the stud in
  the beam to which the motion side rod 
is attached is too far out1 and must  be
 shifted nearer to the main centre2 if  
at the extremities the cross head  is   
thrown too far in1 the stud in the beam 
is not out far enough4 ,if the  cross   
head be thrown in at the one end1 and   
out equally at the other1 the  fault is 
in the motion side rod1 which must be   
lengthened or shortened to  remedy the  
defect4    #gbb4 ,q4--,will you describe
 the method pursued in erecting         
oscillating  engines8    ,a4--,the      
columns here are of wrought iron1 and in
 the case of small  engines there is a  

template made of wood and sheet iron1 in
 which the holes  are set in the proper 
positions1 by which the upper and lower 
frames are  adjusted2 but in the case of
 large engines1 the holes are set off by
 means  of trammels4 ,the holes for the 
reception of the columns are cast in the
  frames1 and are recessed out          
internally3 the bosses encircling the   
holes  are made quite level across1 and 
made very true with a face plate1 and   
the  pillars which have been turned to a
 gauge are then inserted4 ,the top frame
  is next put on1 and must bear upon the
 collars of the columns so evenly1  that
 one of the columns will not be bound by
 it harder than another4 ,if  this point
 be not attained1 the surfaces must be  
further scraped1 until a  perfect fit is
 established4 ,the whole of the bearings
 in the best  oscillating engines are   
fitted by means of scraping1 and on no  
other mode  of fitting can the same     
reliance be placed for exactitude4      
#gbc4 ,q4--,how do you set out the      

trunnions of oscillating engines1 so    
that  they shall be at right angles with
 the interior of the cylinder8          
,a4--,having bored the cylinder1 faced  
the flange1 and bored out the hole      
through which the boring bar passes1 put
 a piece of wood across the mouth  of   
the cylinder1 and jam it in1 and put a  
similar piece in the hole through  the  
bottom of the cylinder4 ,mark the centre
 of the cylinder upon each of  these    
pieces1 and put into the bore of each   
trunnion an iron plate1 with a  small   
indentation in the middle to receive the
 centre of a lathe1 and  adjusting      
screws to bring the centre into any     
required position4 ,the  cylinder must  
then be set in a lathe1 and hung by the 
centres of the  trunnions1 and a        
straight edge must be put across the    
cylinder mouth and  levelled1 so as to  
pass through the line in which the      
centre of the  cylinder lies4 ,another  
similar straight edge1 and similarly    
levelled1 must  be similarly placed     

across the cylinder bottom1 so as to    
pass through the  central line of the   
cylinder2 and the cylinder is then to be
 turned round  in the trunnion          
centres-the straight edges remaining    
stationary1 which will  at once show    
whether the trunnions are in the same   
horizontal plane as the  centre of the  
cylinder1 and if not1 the screws of the 
plates in the  trunnions must be        
adjusted until the central point of the 
cylinder just  comes to the straight    
edge1 whichever end of the cylinder is  
presented4 ,to  ascertain whether the   
trunnions stand in a transverse plane1  
parallel to  the cylinder flange1 it is 
only necessary to measure down from the 
flange  to each trunnion centre2 and if 
both these conditions are satisfied1 the
  position of the centres may be        
supposed to be right4 ,the trunnion     
bearings  are then turned1 and are      
fitted into blocks of wood1 in which    
they run  while the packing space is    
being turned out4 ,where many           

oscillating engines  are made1 a lathe  
with four centres is used1 which makes  
the use of  straight edges in setting   
out the trunnions superfluous4    #gbd4 
,q4--,will you explain how the slide    
valve of a marine engine is set8        
,a4--,place the crank in the position   
corresponding to the end of the  stroke1
 which can easily be done in the shop   
with a level1 or plumb line2  but in a  
steam vessel another method becomes     
necessary4 ,draw the transverse  centre 
line1 answering to the centre line of   
the crank shaft1 on the sole  plate of  
the engine1 or on the cylinder mouth if 
the engine be of the  direct action     
kind2 describe a circle of the diameter 
of the crank pin upon  the large eye of 
the crank1 and mark off on either side  
of the transverse  centre line a        
distance equal to the semi-diameter of  
the crank pin4 ,from  the point thus    
found1 stretch a line to the edge of the
 circle described on  the large eye of  
the crank1 and bring round the crank    

shaft till the crank  pin touches the   
stretched line2 the crank may thus be   
set at either end of  its stroke4 ,when 
the crank is thus placed at the end of  
the stroke1 the  valve must be adjusted 
so as to have the amount of lead1 or    
opening on the  steam side1 which it is 
intended to give at the beginning of the
 stroke2  the eccentric must then be    
turned round upon the shaft until the   
notch in  the eccentric rod comes       
opposite the pin on the valve lever1 and
 falls into  gear3 mark upon the shaft  
the situation of the eccentric1 and put 
on the  catches in the usual way4 ,the  
same process must be repeated for going 
astern1 shifting round the eccentric to 
the opposite side of the shaft1  until  
the rod again falls into gear4 ,in      
setting valves1 regard must of  course  
be had to the kind of engine1 the       
arrangements of the levers1 and  the    
kind of valve employed2 and in any      
general instructions it is  impossible  
to specify every modification in the    

procedure that  circumstances may render
 advisable4    #gbe4 ,q4--,is a similar 
method of setting the valve adopted when
 the link  motion is employed4          
,a4--,each end of the link of the link  
motion has the kind of motion           
communicated to it that is due to the   
action of the particular eccentric  with
 which that end is in connection4 ,in   
that form of the link motion in  which  
the link itself is moved up or down1    
there is a different amount of  lead for
 each different position of the link1   
since to raise or lower the  link is    
tantamount to turning the eccentric     
round on the shaft4 ,in that  form of   
the link motion in which the link itself
 is not raised or lowered1  but is      
susceptible of a motion round a centre  
in the manner of a double  ended lever1 
the lead continues uniform4 ,in both    
forms of the link motion1  as the stroke
 of the valve may be varied to any      
required extent while the  lap is a     
constant quantity1 the proportion of the

 lap relatively to the  stroke of the   
valve may also be varied to any required
 extent1 and the  amount of the lap     
relatively with the stroke of the valve 
determines the  amount of the expansion4
 ,in setting the valve when fitted with 
the link  motion1 the mode of procedure 
is much the same as when it is moved by 
a  simple eccentric4 ,the first thing is
 to determine if the eccentric rods are 
of the proper length1 and this is done  
by setting the valve at half stroke  and
 turning round the eccentric1 marking   
each extremity of the travel of  the end
 of the rod4 ,the valve attachment      
should be midway between these          
extremes2 and if it is not so1 it must  
be made so by lengthening or  shortening
 the rod4 ,the forward and backward     
eccentric rods are to be  adjusted in   
this way1 and this being done1 the      
engine is to be put to the  end of the  
stroke1 and the eccentric is to be      
turned round until the amount  of lead  
has been given that is desired4 ,the    

valve must be tried by turning  the     
engine round to see that it is right at 
both centres1 for going ahead  and also 
for going astern4 ,in some examples of  
the link motion1 one of the  eccentric  
rods is made a little longer than the   
other1 and the position of  the point of
 suspension or point of support         
powerfully influences the  action of the
 link in certain cases1 especially if   
the link and this point  are not in the 
same vertical line4 ,to reconcile all   
the conditions proper  to the           
satisfactory operation of the valve in  
the construction of the link  motion1 is
 a problem requiring a good deal of     
attention and care for its  satisfactory
 solution2 and to make sure that this   
result is attained1 the  engine must be 
turned round a sufficient number of     
times to enable us to  ascertain if the 
valve occupies the desired position1    
both at the top and  bottom centres1    
whether the engine is going ahead or    
astern4 ,this should  also be tried with

 the starting handle in the different   
notches1 or1 in  other words1 with the  
sliding block in the slot or opening of 
the link in  different positions4       
,,management ,,of ,,marine ,,boilers4   
#gbf4 ,q4--,you have already stated that
 the formation of salt or scale in      
marine boilers is to be prevented by    
blowing out into the sea at frequent    
intervals a portion of the concentrated 
water4 ,will you now explain how the    
proper quantity of water to be blown out
 is determined8    ,a4--,by means of the
 salinometer1 which is an instrument for
 determining  the density of the water1 
constructed on the principle of the     
hydrometer  for telling the strength of 
spirits4 ,some of the water is drawn off
 from  the boiler from time to time1 and
 the salinometer is immersed in it after
  it has been cooled4 ,by the           
graduations of the salinometer the      
saltness of  this water is at once      
discovered2 and if the saltness exceeds 
#h ounces of  salt in the gallon1 more  

water should be blown out of the boiler 
to be  replenished with fresher water   
from the sea1 until the prescribed limit
 of  freshness is attained4 ,should the 
salinometer be accidentally broken1 a   
temporary one may be constructed of a   
phial weighted with a few grains of     
shot or other convenient weight4 ,the   
weighted phial is first to be floated   
in fresh water1 and its line of         
floatation marked2 then to be floated in
  salt water1 and its line of floatation
 marked2 and another mark of an equal   
height above the salt water mark will be
 the blow off point4    #gbg4 ,q4--,,how
 often should boilers be blown off in   
order to keep them free  from           
incrustation8    ,a4--,flue boilers     
generally require to be blown off about 
twice every  watch1 or about twice in   
the four hours2 but tubular boilers may 
require to  be blown off once every     
twenty minutes1 and such an amount of   
blowing off  should in every case be    
adopted1 as will effectually prevent any

 injurious  amount of incrustation4     
#gbh4 ,q4--,in the event of scale       
accumulating on the flues of a boiler1  
what is the best way of removing it8    
,a4--,if the boilers require to be      
scaled1 the best method of performing   
the operation appears to be the         
following3--,lay a train of shavings    
along  the flues1 open the safety valve 
to prevent the existence of any pressure
  within the boiler1 and light the train
 of shavings1 which1 by expanding       
rapidly the metal of the flues1 while   
the scale1 from its imperfect           
conducting power1 can only expand       
slowly1 will crack off the scale2 by    
washing down the flues with a hose1 the 
scale will be carried to the bottom  of 
the boiler1 or issue1 with the water1   
from the mud-hole doors4 ,this  method  
of scaling must be practised only by the
 engineer himself1 and must  not be     
intrusted to the firemen who1 in their  
ignorance1 might damage the  boiler by  
overheating the plates4 ,it is only     

where the incrustation upon  the flues  
is considerable that this method of     
removing it need be  practised2 in      
partial cases the scale may be chipped  
off by a hatched faced  hammer1 and the 
flues may then be washed down with the  
hose in the manner  before described4   
#gbi4 ,q4--,should the steam be let out 
of the boiler1 after it has blown  out  
the water1 when the engine is stopped8  
,a4--,no2 it is better to retain the    
steam in the boiler1 as the heat and    
moisture it occasions soften any scale  
adhering to the boiler1 and cause it  to
 peel off4 ,care must1 however1 be taken
 not to form a vacuum in the  boiler2   
and the gauge cocks1 if opened1 will    
prevent this4    #gcj4 ,q4--,are tubular
 boilers liable to the formation of     
scale in certain  places1 though        
generally free from it8    ,a4--,in     
tubular boilers a good deal of care is  
required to prevent the  ends of the    
tubes next the furnace from becoming    
coated with scale4 ,even  when the      

boiler is tolerably clean in other      
places the scale will collect  here2 and
 in many cases where the amount of      
blowing off previously found to  suffice
 for flue boilers has been adopted1 an  
incrustation five eighths of  an inch in
 thickness has formed in twelve months  
round the furnace ends of  the tubes1   
and the stony husks enveloping them have
 actually grown together  in some parts 
so as totally to exclude the water4     
#gca4 ,q4--,when a tubular boiler gets  
incrusted in the manner you have        
described1 what is the best course to be
 adopted for the removal of the  scale8 
,a4--,when a boiler gets into this state
 the whole of the tubes must be  pulled 
out1 which may be done by a ,spanish    
windlass combined with a pair of        
blocks2 and three men1 when thus        
provided1 will be able to draw out from 
#ej  to #gj tubes per day1--those tubes 
with the thickest and firmest           
incrustations being1 of course1 the most
 difficult to remove4 ,the act of       

drawing out the tubes removes the       
incrustation2 but the tubes should      
afterward be scraped by drawing them    
backward and forward between the old    
files1 fixed in a vice1 in the form of  
the letter ,v4 ,the ends of the tube    
should then be heated and dressed with  
the hammer1 and plunged while at a      
blood heat into a bed of sawdust to make
 them cool soft1 so that they may  be   
riveted again with facility4 ,a few of  
the tubes will be so far damaged  at the
 ends by the act of drawing them out1 as
 to be too short for  reinsertion3 this 
result might be to a considerable extent
 obviated by  setting the tube plates at
 different angles1 so that the several  
horizontal  rows of tubes would not be  
originally of the same length1 and the  
damaged  tubes of the long rows would   
serve to replace the short ones2 but the
  practice would be attended with other 
inconveniences4    #gcb4 ,q4--,is there 
no other means of keeping boilers free  
from scale than  by blowing off8        

,a4--,muriatic acid1 or muriate of      
ammonia1 commonly called sal-ammoniac1  
introduced into a boiler1 prevents scale
 to a great extent2 but it is  liable to
 corrode the boiler internally1 and also
 to damage the engine1 by  being carried
 over with the steam2 and the use of    
such intermixtures does  not appear to  
be necessary1 if blowing off from the   
surface of the water is  largely        
practised4 ,in old boilers1 however1    
already incrusted with scale1  the use  
of muriate of ammonia may sometimes be  
advantageous4      #gcc4 ,q4--,are not  
the tubes of tubular boilers liable to  
be choked up by  deposits of soot8      
,a4--,the soot which collects in the    
inside of the tubes of tubular boilers  
is removed by means of a brush1 like a  
large bottle brush2 and the             
carbonaceous scale1 which remains       
adhering to the interior of the tubes1  
is  removed by a circular scraper4      
,ferules in the tubes interfere with the
  action of this scraper1 and in the    

case of iron tubes ferules are now      
generally discarded2 but it will        
sometimes be necessary to use ferules   
for  iron tubes1 where the tubes have   
been drawn and reinserted1 as it may be 
difficult to refix the tubes without    
such an auxiliary4 ,tubes one tenth of  
an inch in thickness are too thin3 one  
eighth of an inch is a better           
thickness1 and such tubes will better   
dispense with the use of ferules1 and   
will not so soon wear into holes4       
#gcd4 ,q4--,if the furnace or flue of a 
boiler be injured1 how do you  proceed  
to repair it8    ,a4--,if from any      
imperfection in the roof of a furnace or
 flue a patch  requires to be put upon  
it1 it will be better to let the patch  
be applied  upon the upper1 rather than 
upon the lower1 surface of the plate2 as
 if  applied within the furnace a recess
 will be formed for the lodgment of     
deposit1 which will prevent the rapid   
transmission of the heat in that  part2 
and the iron will be very liable to be  

again burned away4 ,a crack in  a plate 
may be closed by boring holes in the    
direction of the crack1 and  inserting  
rivets with large heads1 so as to cover 
up the imperfection4 ,if  the top of the
 furnace be bent down1 from the boiler  
having been  accidentally allowed to get
 short of water1 it may be set up again 
by a  screw jack1--a fire of wood having
 been previously made beneath the       
injured  plate2 but it will in general  
be nearly as expeditious a course to    
remove  the plate and introduce a new   
one1 and the result will be more        
satisfactory4    #gce4 ,q4--,in the case
 of the chimney being carried away by   
shot or  otherwise1 what course would   
you pursue8    ,a4--,in some cases of   
collision1 the funnel is carried away   
and lost  overboard1 and such cases are 
among the most difficult for which a    
remedy  can be sought4 ,if flame come   
out of the chimney when the funnel is   
knocked  away1 so as to incur the risk  
of setting the ship on fire1 the uptake 

of  the boiler must be covered over with
 an iron plate1 or be sufficiently      
covered to prevent such injury4 ,a      
temporary chimney must then be made of  
such materials as are on board the ship4
 ,if there are bricks and clay or  lime 
on board1 a square chimney may be built 
with them1 or1 if there be  sheet iron  
plates on board1 a square chimney may be
 constructed of them4 ,in  the absence  
of such materials1 the awning stanchions
 may be set up round  the chimney1 and  
chain rove in through among them in the 
manner of wicker  work1 so as to make an
 iron wicker chimney1 which may then be 
plastered  outside with wet ashes mixed 
with clay1 flour1 or any other material 
that  will give the ashes cohesion4 ,war
 steamers should carry short spare      
funnels1 which may easily be set up     
should the original funnel be shot      
away2 and if a jet of steam be let into 
the chimney1 a very short and small     
funnel will suffice for the purpose of  
draught4        ,,management ,,of       

,,marine ,,engines4    #gcf4 ,q4--,what 
are the most important of the points    
which suggest  themselves to you in     
connection with the management of marine
 engines8    ,a4--,the attendants upon  
engines should prepare themselves for   
any  casualty that may arise1 by        
considering possible cases of           
derangement1 and  deciding ,in what way 
they would act should certain accidents 
occur4 ,the  course to be pursued must  
have reference to particular engines1   
and no  general rules can therefore be  
given2 but every marine engineer should 
be  prepared with the measures to be    
pursued in the emergencies in which he  
may  be called upon to act1 and where   
everything may depend upon his energy   
and  decision4    #gcg4 ,q4--,what is   
the first point of a marine engineer's  
duty8    ,a4--,the safe custody of the  
boiler4 ,he must see that the feed is   
maintained1 being neither too high nor  
too low1 and that blowing out the       
supersalted water is practised          

sufficiently4 ,the saltness of the water
 at  every half hour should be entered  
in the log book1 together with the      
pressure of steam1 number of revolutions
 of the engine1 and any other           
particulars which have to be recorded4  
,the economical use of the fuel is      
another matter which should receive     
particular attention4 ,if the coal is   
very small1 it should be wetted before  
being put on the fire4 ,next to the     
safety of the boiler1 the bearings of   
the engine are the most important       
consideration4 ,these points1 indeed1   
constitute the main parts of the duty   
of an engineer1 supposing no accident to
 the machinery to have taken place4     
#gch4 ,q4--,if the eccentric catches or 
hoops were disabled1 how would you  work
 the valve8    ,a4--,if the eccentric   
catches or hoops break or come off1 and 
the damage  cannot readily be repaired1 
the valve may be worked by attaching the
 end of  the starting handle to any     
convenient part of the other engine1 or 

to some  part in connection with the    
connecting rod of the same engine4 ,in  
side  lever engines1 with the starting  
bar hanging from the top of the diagonal
  stay1 as is a very common arrangement1
 the valve might be wrought by  leading 
a rope from the side lever of the other 
engine through blocks so as  to give a  
horizontal pull to the hanging starting 
bar1 and the bar could be  brought back 
by a weight4 ,another plan would be1 to 
lash a piece of wood to  the cross tail 
butt of the damaged engine1 so as to    
obtain a sufficient  throw for working  
the valve1 and then to lead a piece of  
wood or iron1 from  a suitable point in 
the piece of wood attached to the cross 
tail1 to the  starting handle1 whereby  
the valve would receive its proper      
motion4 ,in  oscillating engines it is  
easy to give the required motion to the 
valve1 by  deriving it from the         
oscillation of the cylinder4    #gci4   
,q4--,what would you do if a crank pin  
broke8    ,a4--,if the crank pin breaks 

in a paddle vessel with two engines1 the
  other engine must be made to work one 
wheel4 ,in a screw vessel the same      
course may be pursued1 provided the     
broken crank is not the one through     
which the force of the other engine is  
communicated to the screw4 ,in such a   
case the vessel will be as much disabled
 as if she broke the screw shaft or     
screw4    #gdj4 ,q4--,will the unbroken 
engine1 in the case of disarrangement of
 one  of the two engines of a screw or  
paddle vessel1 be able of itself to turn
  the centre8    ,a4--,it will sometimes
 happen1 when there is much lead upon   
the slide  valve1 that the single       
engine1 on being started1 cannot be got 
to turn the  centre if there be a strong
 opposing wind and sea2 the piston going
 up to  near the end of the stroke1 and 
then coming down again without the crank
  being able to turn the centre4 ,in    
such cases1 it will be necessary to turn
  the vessel's head sufficiently from   
the wind to enable some sail to be set2 

and if once there is weigh got upon the 
vessel the engine will begin to  work   
properly1 and will continue to do so    
though the vessel be put head to  wind  
as before4    #gda4 ,q4--,what should be
 done if a crack shows itself in any of 
the shafts  or cranks8    ,a4--,if the  
shafts or cranks crack1 the engine may  
nevertheless be worked  with moderate   
pressure to bring the vessel into port2 
but if the crack be  very bad1 it will  
be expedient to fit strong blocks of    
wood under the ends  of the side levers1
 or other suitable part1 to prevent the 
cylinder bottom  or cover from being    
knocked out1 should the damaged part    
give way4 ,the same  remark is          
applicable when flaws are discovered in 
any of the main parts of  the engine1   
whether they be malleable or cast iron2 
but they must be  carefully watched1 so 
that the engines may be stopped if the  
crack is  extending further4 ,should    
fracture occur1 the first thing         
obviously to be  done is to throw the   

engines out of gear2 and should there be
 much weigh on  the vessel1 the steam   
should at once be thrown on the reverse 
side of the  piston1 so as to counteract
 the pressure of the paddle wheel4      
#gdb4 ,q4--,have you any information to 
offer relative to the lubrication of    
engine bearings8    ,a4--,a very useful 
species of oil cup is now employed in a 
number of steam  vessels1 and which1 it 
is said1 accomplishes a considerable    
saving of oil1  at the same time that it
 more effectually lubricates the        
bearings4 ,a  ratchet wheel is fixed    
upon a little shaft which passes through
 the side of  the oil cup1 and is put   
into slow revolution by a pendulum      
attached to its  outside and in         
revolving it lifts up little buckets of 
oil and empties them  down a funnel upon
 the centre of the bearing4 ,instead of 
buckets a few  short pieces of wire are 
sometimes hung on the internal revolving
 wheel1  the drops of oil which adhere  
on rising from the liquid being         

deposited4  upon a high part set upon   
the funnel1 and which1 in their         
revolution1 the  hanging wires touch4   
,by this plan1 however1 the oil is not  
well supplied at  slow speeds1 as the   
drops fall before the wires are in      
proper position for  feeding the        
journal4 ,another lubricator consists of
 a cock or plug inserted  in the neck of
 the oil cup1 and set in revolution by a
 pendulum and ratchet  wheel1 or any    
other means4 ,there is a small cavity in
 one side of the plug1  which is filled 
with oil when that side is uppermost1   
and delivers the oil  through the bottom
 pipe when it comes opposite to it4     
#gdc4 ,q4--,what are the prevailing     
causes of the heating of bearings8      
,a4--,bad fitting1 deficient surface1   
and too tight screwing down4  ,sometimes
 the oil hole will choke1 or the syphon 
wick for conducting the  oil from the   
oil cup into the central pipe leading to
 the bearing will  become clogged with  
mucilage from the oil4 ,in some cases   

bearings heat from  the existence of a  
cruciform groove on the top brass for   
the distribution  of the oil1 the effect
 of which is to leave the top of the    
bearings dry4 ,in  the case of revolving
 journals the plan for cutting a        
cruciform channel for  the distribution 
of the oil does not do much damage2 but 
in other cases1 as  in beam journals1   
for instance1 it is most injurious1 and 
the brasses  cannot wear well wherever  
the plan is pursued4 ,the right way is  
to make a  horizontal groove along the  
brass where it meets the upper surface  
of the  bearing1 so that the oil may be 
all deposited on the highest point of   
the  journal1 leaving the force of      
gravity to send it downward4 ,this      
channel  should1 of course1 stop short a
 small distance from each flange of the 
brass1 otherwise the oil would run out  
at the ends4    #gdd4 ,q4--,if a bearing
 heats1 what is to be done8    ,a4--,the
 first thing is to relax the screws1    
slow or stop the engine1 and  cool the  

bearing with water1 and if it is very   
hot1 then hot water may be  first       
employed to cool it1 and then cold4 ,oil
 with sulphur intermingled is  then to  
be administered1 and as the parts cool  
down1 the screws may be  again          
cautiously tightened1 so as to take any 
jump off the engine from the  bearing   
being too slack4 ,the bearings of direct
 acting screw engines  require constant 
watching1 as1 if there be any           
disposition to heat  manifested by them1
 they will probably heat with great     
rapidity from the  high velocity at     
which the engines work4 ,every bearing  
of a direct acting  screw engine should 
have a cock of water laid on to it1     
which may be  immediately opened wide   
should heating occur2 and it is         
advisable to work  the engine           
constantly1 partly with water1 and      
partly with oil applied to  the         
bearings4 ,the water and oil are mixed  
by the friction into a species of  soap 
which both cools and lubricates1 and    

less oil moreover is used than if  water
 were not employed4 ,it is proper to    
turn off the water some time  before the
 engine is stopped1 so as to prevent the
 rusting of the bearings4               
,,management ,,of ,,locomotives4        
#gde4 ,q4--,what are the chief duties of
 the engine driver of a locomotive8     
,a4--,his first duties are those which  
concern the safety of the train2 his    
next those which concern the safety and 
right management of the engine and      
boiler4 ,the engine driver's first      
solicitude should be relative to the    
observation and right interpretation of 
the signals2 and it is only after  these
 demands upon his attention have been   
satisfied1 that he can look to  the     
state of his engine4    #gdf4 ,q4--,as  
regards the engine and boiler1 what     
should his main duties  be8    ,a4--,the
 engineer of a locomotive should        
constantly be upon the foot board  of   
the engine1 so that the regulator1 the  
whistle or the reversing handle  may be 

used instantly1 if necessary2 he must   
see that the level of the  water in the 
boiler is duly maintained1 and that the 
steam is kept at a  uniform pressure4   
,in feeding the boilers with water1 and 
the furnaces with  fuel1 a good deal of 
care and some tact are necessary1 as    
irregularity in  the production of steam
 will often occasion priming1 even      
though the water  be maintained at a    
uniform level2 and an excess of water   
will of itself  occasion priming1 while 
a deficiency is a source of obvious     
danger4 ,the  engine is generally       
furnished with three gauge cocks1 and   
water should  always come out of the    
second gauge cock1 and steam out of the 
top one when  the engine is running3 but
 when the engine is at rest1 the water  
in the  boiler is lower than when in    
motion1 so that when the engine is at   
rest1  the water will be high enough if 
it just reaches to the middle gauge     
cock4  ,in all boilers which generate   
steam rapidly1 the volume of the water  

is  increased by the mingled steam1 and 
in feeding with cold water the level at 
first falls2 but it rises on opening the
 safety valve1 which causes the  steam  
in the water to swell to a larger       
volume4 ,in locomotive boilers1 the     
rise of the water level due to the rapid
 generation of steam is termed  false   
water4 ,to economize fuel1 the variable 
expansion gear1 if the  engine has one1 
should be adjusted to the load1 and the 
blast pipe should  be worked with the   
least possible contraction2 and at      
stations the damper  should be closed to
 prevent the dissipation of heat4       
#gdg4 ,q4--,in starting from a station1 
what precautions should be observed     
with respect to the feed8    ,a4--,in   
starting from a station1 and also in    
ascending inclined planes1  the feed    
water is generally shut off2 and        
therefore before stopping or  ascending 
inclined planes1 the boiler should be   
well filled up with water4  ,in         
descending inclined planes an extra     

supply of water may be introduced  into 
the boiler1 and the fire may be fed1 as 
there1 is at such times a  superfluity  
of steam4 ,in descending inclined planes
 the regulator must be  partially       
closed1 and it should be entirely closed
 if the plane be very  steep4 ,the same 
precaution should be observed in the    
case of curves1 or  rough places on the 
line1 and in passing over points or     
crossings4    #gdh4 ,q4--,in approaching
 a station1 how should the supply of    
water and  fuel be regulated8           
,a4--,the boiler should be well filled  
with water on approaching a station1  as
 there is then steam to spare1 and      
additional water cannot be  conveniently
 supplied when the engine is stationary4
 ,the furnace should be  fed with small 
quantities of fuel at a time1 and the   
feed should be turned  off just before a
 fresh supply of fuel is introduced4    
,the regulator may1 at  the same time1  
be partially closed2 and if the blast   
pipe be a variable  one1 it will be     

expedient to open it widely while the   
fuel is being  introduced1 to check the 
rush of air in through the furnace door1
 and then  to contract it very much so  
soon as the furnace door is closed1 in  
order to  recover the fire quickly4 ,the
 proper thickness of coke upon the grate
  depends upon the intensity of the     
draught2 but in heavily loaded engines  
it  is usually kept up to the bottom of 
the fire door4 ,care1 however1 must be  
taken that the coke does not reach up to
 the bottom row of tubes so as to  choke
 them up4 ,the fuel is usually disposed 
on the grate like a vault2 and  if the  
fire box be a square one1 it is heaped  
high in the corners1 the  better to     
maintain the combustion4    #gdi4       
,q4--,how can you tell whether the feed 
pumps are operating properly8           
,a4--,to ascertain whether the pumps are
 acting well1 the pet cock must be      
turned1 and if any of the valves stick  
they will sometimes be induced to  act  
again by working with the pet cock open1

 or alternately open and shut4  ,should 
the defect arise from a leakage of steam
 into the pump1 which  prevents the pump
 from drawing1 the pet cock remedies the
 evil by  permitting the steam to       
escape4    #gej4 ,q4--,what precautions 
should be taken against priming in      
locomotives8    ,a4--,should priming    
occur from the water in the boiler being
 dirty1 a  portion of it may be blown   
out2 and should there be much boiling   
down  through the glass gauge tube1 the 
stop cock may be partially closed4 ,the 
water should be wholly blown out of     
locomotive boilers three times a week1  
and at those times two mud-hole doors at
 opposite corners of the boiler  should 
be opened1 and the boiler be washed     
internally by means of a hose4  ,if the 
boiler be habitually fed with dirty     
water1 the priming will be a  constant  
source of trouble4    #gea4 ,q4--,what  
measures should the locomotive engineer 
take1 to check the  velocity of the     
train1 on approaching a station where he

 has to stop8    ,a4--,on approaching a 
station the regulator should be         
gradually closed1  and it should be     
completely shut about half a mile from  
the station if the  train be a very     
heavy one3 the train may then be brought
 to rest by means  of the breaks4 ,too  
much reliance1 however1 must not be put 
upon the breaks1  as they sometimes give
 way1 and in frosty weather are nearly  
inoperative4  ,in cases of urgency the  
steam may be thrown upon the reverse    
side of the  piston1 but it is desirable
 to obviate this necessity as far as    
possible4  ,at terminal stations the    
steam should be shut off earlier than at
 roadside  stations1 as a collision will
 take place at terminal stations if the 
train  overshoots the place where it    
ought to stop4 ,there should always be a
 good  supply of water when the engine  
stops1 but the fire may be suffered     
gradually to burn low toward the        
conclusion of the journey4    #geb4     
,q4--,what is the duty of an engine man 

on arriving at the end of his  journey8 
,a4--,so soon as the engine stops it    
should be wiped down1 and be then       
carefully examined3 the brasses should  
be tried1 to see whether they are  slack
 or have been heating2 and1 by the      
application of a gauge1 it should  be   
ascertained occasionally whether the    
wheels are square on their axles1  and  
whether the axles have end play1 which  
should be prevented4 ,the  stuffing     
boxes must be tightened1 and the valve  
gear examined1 and the  eccentrics be   
occasionally looked at to see that they 
have not shifted on  their axles1 though
 this defect will be generally intimated
 by the  irregular beating of the       
engines4 ,the tubes should also be      
examined and  cleaned out1 and the ashes
 emptied out of the smoke box through   
the small  ash door at the end4 ,if the 
engine be a six-wheeled one1 with the   
driving  wheels in the middle1 it will  
be liable to pitch1 and oscillate if too
 much  weight be thrown upon the driving

 wheels2 and where such faults are found
  to exist1 the weight upon the drivings
 wheels should be diminished4 ,the      
practice of blowing off the boiler by   
the steam1 as is always done in  marine 
boilers1 should not be permitted as a   
general rule in locomotive  boilers1    
when the tubes are of brass and the fire
 box of copper2 but when  the tubes and 
fire boxes are of iron1 there will not  
be an equal risk of  injury4 ,before    
starting on a journey1 the engine man   
should take a summary  glance beneath   
the engine--but before doing so he ought
 to assure himself  that no other engine
 is coming up at the time4 ,the         
regulator1 when the  engine is standing1
 should be closed and locked1 and the   
eccentric rod be  fixed out of gear1 and
 the tender break screwed down2 the     
cocks of the oil  vessels should at the 
same time be shut1 but should all be    
opened a short  time before the train   
starts4    #gec4 ,q4--,what should be   
done if a tube bursts in the boiler8    

,a4--,when a tube bursts1 a wooden or   
iron plug must be driven into each  end 
of it1 and if the water or steam be     
rushing out so fiercely that the  exact 
position of the imperfection cannot be  
discovered1 it will be  advisable to    
diminish the pressure by increasing the 
supply of feed water4  ,should the leak 
be so great that the level of the water 
in the boiler  cannot be maintained1 it 
will be expedient to drop the bars and  
quench the  fire1 so as to preserve the 
tubes and fire box from injury4    #ged4
 ,q4--,if any of the working parts of a 
locomotive break or become  deranged1   
what should be done8    ,a4--,should the
 piston rod or connecting rod break1 or 
the cutters fall  out or be clipped     
off--as sometimes happens to the piston 
cutter when the  engine is suddenly     
reversed upon a heavy train--the parts  
should be  disconnected1 if the         
connection cannot be restored1 so as to 
enable one  engine to work2 and of      
course the valve of the faulty engine   

must be kept  closed4 ,if one engine has
 not power enough to enable the train to
 proceed  with the blast pipe full open1
 the engine may perhaps be able to take 
on a  part of the carriages1 or it may  
run on by itself to fetch assistance4   
,the  same course must be pursued if any
 of the valve gearing becomes deranged1 
and the defects cannot be rectified upon
 the spot4    #gee4 ,q4--,what are the  
most usual causes of railway collisions8
    ,a4--,probably fogs and inexactness 
in the time kept by the trains4         
,collisions have sometimes occurred from
 carriages having been blown from a     
siding on to the rails by a high wind2  
and the slippery state of the rails1  or
 the fracture of a break1 has sometimes 
occasioned collisions at terminal       
stations4 ,collision has also repeatedly
 taken place from one engine having     
overtaken another1 from the failure of a
 tube in the first engine1 or from  some
 other slight disarrangement2 and       
collision has also taken place from  the

 switches having been accidentally so   
left as to direct the train into a      
siding1 instead of continuing it on the 
main line4 ,every train now carries  fog
 signals1 which are detonating packets1 
which are fixed upon the rails  in      
advance or in the rear of a train which1
 whether from getting off the  rails or 
otherwise1 is stopped upon the line1 and
 which are exploded by the  wheels of   
any approaching train4    #gef4         
,q4--,what other duties of an           
engine-driver are there deserving       
attention8    ,a4--,they are too various
 to be all enumerated here1 and they    
also vary  somewhat with the nature of  
the service4 ,one rule1 however1 of     
universal  application1 is for the      
driver to look after matters himself1   
and not  delegate to the stoker the     
duties which the person in charge of the
 engine  should properly perform4       
,before leaving a station1 the          
engine-driver should  assure himself    
that he has the requisite supply of coke

 and water4 ,besides  the firing tools  
and rakes for clearing the tubes1 he    
should have with him  in the tender a   
set of signal lamps and1 torches1 for   
tunnels and for  night1 detonating      
signals1 screw keys1 a small tank of    
oil1 a small cask of  tallow1 and a     
small box of waste1 a coal hammer1 a    
chipping hammer1 some  wooden and iron  
plugs for the tubes1 and an iron tube   
holder for inserting  them1 one or two  
buckets1 a screw jack1 wooden and iron  
wedges1 split wire  for pins1 spare     
cutters1 some chisels and files1 a pinch
 bar1 oil cans and  an oil syringe1 a   
chain1 some spare bolts1 and some cord1 
spun yarn1 and  rope4          ,,index4 
,accidents in steam vessels1 proper     
preparation for4  ,admiralty rule for   
horse power4  ,adhesion of wheels of    
locomotives to rails4  ,air1 velocity   
of1 entering a vacuum1    required for  
combustion of coal2    law of expansion 
of1 by heat2  ,air pump1 description of1
    action of2    proper dimensions of4 

,air pump of marine engines1 details of4
  ,air pump of oscillating engine4  ,air
 pump of direct acting screw engines4   
,air pumps made both single and double  
acting1    difference of1 explained4    
,air pumps1 double acting valves of1    
bad vacuum in2    causes and remedy4    
,air pump rods1 brass or copper1 in     
marine engines4  ,air pump bucket1      
valves of4  ,air pump1 connecting rod   
and cross head of oscillating engine4   
,air pump rod of oscillating engine4    
,air pump arm4  ,air vessels applied to 
suction side of pumps4  ,alma1 engine   
of1 by ,messrs4 ,john ,bourne  ,co4     
,amphion1 engines of4  ,amoskeag steam  
fire engine4  ,angle iron in boilers1   
precautions respecting4  ,apparatus for 
raising screw propeller4  ,atmospheric  
valve4  ,atmospheric resistance to      
railway trains4  ,auxiliary power1 screw
 vessels with4  ,axle bearings of       
locomotives4  ,axle guards4  ,axles and 
wheels of modern locomotives4  ,azof1   
slide valve of4    ,babbitt's metal1 how

 to compound4  ,balance piston to take  
pressure off slide valve4  ,ball valves4
  ,barrel of boiler of modern           
locomotives4  ,beam1 working of land    
engine1    main or working strength     
proper for4  ,bearings of engines or    
other machinery1    rule for determining
 proper surface of4  ,bearings1 heating 
of1 how to prevent or remedy1           
journals should always bottom1 as1 if   
they grip      on the sides1 the        
pressure is infinite4  ,beattie's screw4
  ,belidor's valves might be used for   
foot and delivery valves4  ,bell-metal1 
composition of4  ,blast pipe of         
locomotives1 description of4  ,blast in 
locomotives1 exhaustion produced by1    
proper construction of the blast pipe2  
the blast pipe should be set below the  
root of      the chimney so much that   
the cone of escaping steam shall just   
fill the      chimney4  ,blast pipe with
 variable orifice1 at one time much     
used4  ,blow-off cock of locomotives4   
,blow-off cocks of marine boilers1      

proper construction of4  ,blow-off      
cocks1 description of4  ,blowing off    
supersalted water from marine boilers4  
,blowing off1 estimate of heat lost by1 
mode of4  ,blow through valve1          
description of4  ,blowing furnaces1     
power necessary for4  ,bodies1 falling1 
laws of4  ,bodmer1 expansion valve by4  
,boilers1 general description of3 the   
wagon boiler1    the ,cornish boiler2   
the marine flue boiler2    the marine   
tubular boiler2    locomotive           
boiler--see ,locomotives4  ,boilers     
proportions of3 heating surface of1     
fire grate1 surface of2    consumption  
of fuel on each square foot of fire bars
 in wagon1      ,cornish1 and locomotive
 boilers2    calorimmeter and vent of   
boilers2    comparison of proportions of
 wagon1 flue1 and tubular boilers2      
evaporative power of boilers2    power  
generated by evaporation of a cubic foot
 of water2    proper proportions of     
modern marine boilers both flue and     
tubular2    modern locomotive boilers2  

exhaustion produced by blast in         
locomotives2    increased evaporation   
from increased exhaustion2    strength  
of boilers2    experiments on1 by       
,franklin ,institute2    by ,mr4        
,fairbairn2    mode of computing        
strength of boilers2    staying of4     
,boilers1 marine1 prevented from salting
 by blowing off1    early locomotive and
 contemporaneous marine boilers         
compared2    chimneys of land2    rules 
for proportions of chimneys2    chimneys
 of marine boilers4  ,boilers1          
constructive details of3 riveting and   
caulking of land boilers1    proving of2
    seams payed with mixture of whiting 
and linseed oil2    setting of wagon    
boilers2    riveting of marine boilers2 
precautions respecting angle iron2      
how to punch the rivet holes and shear  
edges of plates2    setting of marine   
boilers in wooden vessels2    mastic    
cement for setting marine boilers2      
composition of mastic cement2    best   
length of furnace2    configuration of  

furnace bars2    advantages and         
construction of furnace bridges2        
various forms of dampers2    precautions
 against injury to boilers from intense 
heat2    tubing of boilers2    proper   
mode of staying tube plates2    proper  
mode of constructing steamboat chimneys2
    waste steam-pipe and funnel casing2 
telescope chimneys2    formation of     
scale in marine boilers2    injury of   
such incrustations2    amount of salt in
 sea water2    saltness permissible in  
boilers2    amount of heat lost by      
blowing off2    mode of discharging the 
supersalted water2    ,lamb's scale     
preventer2    internal corrosion of     
marine boilers2    causes of internal   
corrosion2    surcharged steam produced 
from salt water2    stop valves between 
boilers2    safety or escape valve on   
feed pipe2    locomotive boilers consist
 of the fire box1 barrel for            
holding tubes1 and smoke box2           
dimensions of the barrel and thickness  
of plates2    mode of staying fire box  

and furnace crown2    fire bars1 ash    
box1 and chimney2    steam dome used    
only in old engines2    manhole1        
mudholes1 and blow-oft cock2    tube    
plate1 and mode of securing tubes2      
expanding mandrels2    various forms of 
regulator4  ,boilers of modern          
locomotives4  ,boiler1 the1 proper care 
of1 the first duty of the engineer4     
,bolts1 proper proportions of4  ,boring 
of cylinders4  ,boulton and ,watt's     
rules for fly wheel1    proportions of  
marine flue boilers2    rule for        
proportions of chimneys of land boilers2
    of marine boilers2    experiments on
 the resistance of vessels in water4    
,bourdon's steam and vacuum gauges4     
,bourne1 expansion valves by4  ,bourne1 
,messrs4 ,j4  ,co41 direct acting screw 
engines by4  ,brass for bearings1       
composition of4  ,brazing solders4      
,bridges in furnaces1 benefits of4      
,burning of boilers1 precautions        
against4  ,bursting velocity of fly     
wheel1    and of railway wheels4        

,bursting of boilers1    causes of2     
precautions against2    may be caused by
 accumulations of salt4  ,butterfly     
valves of air pump4    ,cabrey1         
expansion valve by4  ,calorimeter of    
boilers1 definition of4  ,cams1 proper  
forms of4  ,cast iron1 strength of1     
proportions of cast iron beams2         
effects of different kinds of strains on
 beams2    strength to resist shocks not
 proportional to strength to resist     
strains2    to attain maximum strength  
should be combined with wrought iron4   
,casting of cylinders4  ,case-hardening1
 how to accomplish4  ,cataract1         
explanation of nature and uses of4      
,caulking of land boilers4  ,cement1    
mastic1 for setting marine boilers4     
,central forces4  ,centre of pressure of
 paddle wheels4  ,centres of gravity1   
gyration and oscillation4  ,centres for 
fixing arms of paddle wheel4  ,centres  
of an engine1 how to lay off4           
,centrifugal force1 nature of1    rule  
for determining2    bursting velocity of

 fly wheel2    and of railway wheels4   
,centrifugal pump will supersede common 
pump4  ,centripetal force1 nature of4   
,chimney of locomotives4  ,chimney of   
steam vessels1 what to do if carried    
away4  ,chimneys of land boilers1       
,boulton and ,watt's rule for           
proportions of2    of marine boilers4   
,chimneys1 exhaustion produced by1      
high and wide chimneys in locomotives   
injurious4  ,chimneys of steamboats1    
telescope4  ,clark's patent steam fire  
regulator4  ,coal1 constituents of1     
combustion of air required for2         
evaporative efficacy of2    of wood1    
turf1 and coke4  ,cocks1 proper         
construction of4  ,cog wheels for screw 
engines4  ,coke1 evaporative efficacy   
of4  ,cold water pump1 description of1  
rule for size of4  ,combustion1 nature  
of4  ,combustion of coal1 air required  
for4  ,combustion1 slow and rapid1      
comparative merits of1    rapid         
combustion necessary in steam vessels1  
and enables less heating1    surface in 

the boiler to suffice4  ,conchoidal     
propeller4  ,condensation of steam1     
water required for4  ,condenser1        
description of1    action of2    proper 
dimensions of4  ,condenser of           
oscillating engine4  ,condenser of      
direct acting screw engine4  ,condensing
 engine1 definition of4  ,condensing    
water1 how to provide when deficient4   
,conical pendulum or governor4          
,connecting rod1 description of1        
strength proper for4  ,connecting rod of
 direct acting screw engines1    of     
locomotives4  ,consumption of fuel on   
each square foot of fire bars in wagon1 
,cornish1      and locomotive boilers4  
,copper1 strength of4  ,corliss's steam 
engine4  ,corrosion produced by         
surcharged steam4  ,corrosion of marine 
boilers1    causes of4  ,cost of        
locomotives4  ,cotton spinning1 power   
necessary for4  ,counter for counting   
strokes of an engine4  ,crank1          
description of1    unequal leverage of1 
corrected by fly wheel2    no power lost

 by2    action of2    strength proper   
for4  ,crank of direct acting screw     
engines4  ,crank pin1 strength proper   
for4  ,crank pin of direct acting screw 
engines4  ,cranked axle of locomotives4 
,cross head1 description of1    strength
 proper for4  ,cross head of direct     
acting screw engines4  ,cross tail1     
description of4  ,cylinder1 description 
of1    strength proper for4  ,cylinder  
of oscillating engine1    of direct     
acting screw engine4  ,cylinders should 
have a steam jacket1 and be felted and  
planted1    should have escape valves4  
,cylinders of locomotives should be     
large1    proper arrangement of4        
,cylinders1 how to cast1    how to bore2
    how to grind4  ,cylinder jacket1    
advantages of4    ,damper4  ,dampers1   
various forms of4  ,deadwood1 hole in1  
for screw4  ,delivery valve1 description
 of4  ,delivery or discharge valves1    
proper dimensions of4  ,delivery valves 
might be made on ,belidor's plan4       
,delivery valves in mouth of air pump1  

of india rubber4  ,direct acting screw  
engines should be balanced4  ,direct    
acting screw engine by ,messrs4 ,john   
,bourne 1 ,co41      cylinder2          
discs2      guides2      screw shaft    
brasses2      air pump2      slide      
valve2      balance piston2             
connecting rod2      piston rods2       
cross head2      air pump arm2      feed
 pump2      crank pin2      screw shaft2
      thrust plummer block2      link   
motion2      screw propeller4           
,discharge valves4  ,disc valves of     
india rubber for air pumps4  ,discs of  
direct acting screw engine instead of   
crank4  ,dodds1 expansion valve by4     
,double acting engines1 definition of4  
,double acting air pumps1    valves of2 
faults of4  ,draw bolt4  ,dredging earth
 out of rivers1 power necessary for4    
,driving wheels of locomotives4         
,driving piles1 power necessary for4    
,duplex pump1 ,worthington's4           
,dundonald1 ,earl of1 screw by4  ,duty  
of engines and boilers1    how the duty 

is ascertainable4  ,dynamometer1        
description of4  ,dynamometric power of 
screw vessels4    ,eccentric1           
description of1    sometimes made loose 
for backing4  ,eccentric and eccentric  
rod of oscillating engine4  ,eccentric  
notch should be fitted with a brass     
bush4  ,eccentric straps of locomotives1
    rods of locomotives4  ,eccentrics of
 locomotives1    how to readjust4       
,economy of fuel in steam vessels4      
,edwards1 expansion valve by4           
,elasticity1 limits of4  ,engine1 high  
pressure1 definition of1    low         
pressure1 definition of4  ,engines1     
classification of1    rotative1         
definition of2    rotatory1 definition  
of2    single acting1 definition of2    
double acting1 definition of2    mode of
 erecting in a vessel2    how to refix  
if they have become loose4  ,engineers  
of steam vessels should make proper     
preparation for accidents4  ,equilibrium
 slide valve1    grid-iron valve4       
,erecting engines in a vessel4          

,erection of engines in the workshop4   
,escape valve on feed pipe4  ,escape    
valves for letting water out of         
cylinders4  ,evaporative efficacy of    
coal1    of wood1 turf1 and coke4       
,evaporative power of boilers1    power 
generated by evaporation of a cubic foot
 of water2    increase of evaporation   
due to increased exhaustion in          
locomotives4  ,excavator1 ,otis's4      
,exhaustion produced by chimneys1    by 
the blast in locomotives2    increased  
evaporation from increased exhaustion4  
,expanding mandrels for tubing boilers4 
,expansion of air by heat4  ,expansion  
of surcharged steam by heat4  ,expansion
 of steam1    pressure of steam         
inversely as the space occupied2    law 
of expansion2    rule for computing the 
increase of efficiency produced by      
working      expansively2    necessity  
of efficient provisions against         
refrigeration in working                
expansively2    advantages of steam     
jacket2    ,forms of apparatus for      

working expansively3 lap on the slide   
valve      wire drawing the steam2      
,cornish expansion valve1      in       
rotative engines worked by a cam2       
mode of varying the degree of expansion2
      proper forms of cams2      the    
link motion2      expansion valves1 by  
,cabrey1 ,fenton1 ,dodds1 ,farcot1      
,edwards1        ,lavagrian1 ,bodmer1   
,meyer1 ,hawthorn1 ,gonzenbach1 and     
,bourne4  ,expansion joint in valve     
casing4  ,expansion valves1 ,cornish1   
the link motion2    by ,cabrey1 ,fenton1
 ,dodds1 ,farcot1 ,edwards1 ,lavagrian1 
,bodmer1 ,meyer1      ,hawthorn1        
,gouzenbach1 and ,bourne4  ,explosions  
of boilers1    causes of explosions2    
precautions against2    dangers of      
accumulations of salt4    ,face plates  
or planometers4  ,falling bodies1 laws  
of4  ,farcot1 expansion valve by4       
,feathering paddle wheels1 description  
of1    details of4  ,feed pump1         
description of1    action of2    proper 
dimensions of2    rule for              

proportioning4  ,feed pump plunger1     
and valves4  ,feed pumps of locomotives1
 details of4  ,feed pumps of direct     
acting screw engines4  ,fenton1         
expansion valve by4  ,fire bars of      
locomotives4  ,fire box of locomotives1 
mode of staying4  ,fire box of modern   
locomotives4  ,fire engines1 cost of    
running4  ,fire grate surface of        
boilers4  ,fire grate in locomotives    
should be of small area1    coke proper 
to be burned per hour on each square    
foot of bars4  ,firing furnaces1 proper 
mode of4  ,flaws in valves or cylinders1
 how to remedy4  ,float for regulating  
water level in boilers4  ,floats of     
paddle4  ,floats of paddle wheels1      
increased resistance of1 if oblique1    
floats should be large4  ,fly wheel     
corrects unequal leverage of crank1     
proper energy for2    ,boulton and      
,watt's rule for2    bursting velocity  
of2    description of2    action of1 in 
redressing irregularities of motion4    
,foot valve1 description of1    proper  

dimensions of4  ,foot valves might be   
made on ,belidor's plan1    of india    
rubber4  ,frame at stern for holding    
screw propeller4  ,framing of           
locomotives4  ,framing of oscillating   
engine4  ,franklin ,institute1          
experiments on steam by4  ,french       
,academy1 experiments on steam by4      
,friction1 nature of1    does not vary  
as the rubbing surfaces1 but as the     
retaining pressure2    does not increase
 with the velocity per unit of distance1
 but increases      with the velocity   
per unit of time2    measures of        
friction2    effect of unguents2    kind
  of unguent should vary with the       
pressure2    ,morin's experiments2      
rule for determining proper surfaces of 
bearings2    friction of rough surfaces4
  ,friction of the water the main cause 
of the resistance of vessels of good    
shape4  ,fuel burnt on each square foot 
of fire bars in wagon1 ,cornish1 and    
locomotive boilers1    economy of1 in   
steam vessels4  ,funnel casing4         

,funnel1 what to do if carried away4    
,funnels of steam boats4 ,see ,chimneys4
  ,furnaces1 proper mode of firing1     
smoke burning3 ,williams's argand2      
,prideaux's2    ,boulton and ,watt's    
dead plate2    revolving crate2         
,juckes's2    ,maudslay's2    ,hull's1  
,coupland's1   ,godson's1 ,robinson's1  
,stevens's1 ,hazeldine's1      c44      
,furnaces of marine boilers1 proper     
length of4  ,furnace bridges1 benefits  
of4  ,fusible metal plugs useless as    
antidotes to explosions4    ,gauges1    
vacuum1    steam2    gauge cocks and    
glass tubes for showing level of water  
in boiler1      description of4  ,gauge 
cocks for showing level of water in     
boiler4  ,gearing for screw engines4    
,gibs and cutters1 strengths proper for4
  ,giffard's injector4  ,glass tubes for
 showing water level in boilers4  ,glass
 tube cocks4  ,gonzeubach1 expansion    
valve by4  ,gooch's indicator4  ,gooch's
 locomotive4  ,governor or conical      
pendulum1    description of4  ,governor1

 ,porter's patent4  ,gravity1 centre of4
  ,great ,western1 boilers of1 by       
,messrs4 ,maudslay4  ,gridiron valve4   
,griffith's screw4  ,grinding corn1     
power necessary for4  ,grinding of      
cylinders4  ,gudgeons1 strength proper  
for4  ,guides of locomotives4  ,guides  
of direct acting screw engine4  ,gun    
metal1 strength of4  ,gyration1 centre  
of4    ,harvey and ,west's pump valves4 
,hawthorn1 expansion valve by4  ,heat1  
latent1 definition of4  ,heat1 specific1
 definition of4  ,heat1 ,regnault's     
experiments on4  ,heat1 loss of1 by     
blowing off marine boilers4  ,heating   
surface of boilers4  ,heating surface   
per square foot of fire bars in         
locomotives1    a cubic foot of water   
evaporates by five square feet of       
heating surface4  ,heating of bearings1 
causes of1    bearings should always be 
slack at the sides1 else the pressure is
      infinite4  ,high pressure engine1 
definition of4  ,high pressure engines1 
power of4  ,high speed engines1         

arrangements proper for high speeds4    
,hoadley's portable engine4  ,hodgson's 
screw4  ,hoe  ,co4's steam engine4      
,holding down bolts of marine engines1  
or bolts for securing engines to hull4  
,holms's screw propeller4  ,horses      
power1 definition of1    nominal horse  
power2    actual power ascertained by   
the indictator2    ,admiralty rule for4 
,hot water or feed pump1 description of4
  ,hot well1 description of4            
,increasing pitch of screw4             
,incrustation in boilers4 ,see also     
,salt4  ,india rubber valves for air    
pump4  ,indicator1 description of the1  
by ,mc,naught1 structure and mode of    
using2    ,gooch's continuous indicator4
  ,injection cock4  ,injection cocks of 
marine engines at ship's sides4         
,injection orifice1 proper area of4     
,injector1 ,giffard's4  ,injection      
valve4  ,inside cylinder locomotives4   
,iron1 strength of1    limits of        
elasticity of2    proper strain to be   
put upon iron in engines and machines2  

aggravation of strain by being          
intermittent2    increase of strain due 
to deflection2    strength of pillars   
and tubes1      combination of malleable
 and cast iron4  ,iron1 cast1 strength  
of1    cast iron beams2    may be strong
 to resist strains1 but not strong to   
resist shocks2    should be combined    
with wrought iron to obtain maximum     
strength4  ,iron1 if to be case         
hardened1 should be homogeneous4        
,jacket of cylinder1 advantages of4     
,joints1 rust1 how to make4             
,kingston's valves4    ,lamb's scale    
preventer4  ,lantern brass in stuffing  
boxes4  ,lap and lead of the valve1     
meaning of4  ,large vessels have least  
proportionate resistance4  ,latent heat1
 definition of4  ,latta's steam fire    
engine4  ,lavagrian1 expansion valve by4
  ,lead and lap of the valve1 meaning   
of4  ,lead of the valve1 benefits of4   
,lever1    futility of plans for        
deriving power from a lever4  ,lifting  
apparatus for screw propeller4  ,limits 

of elasticity4  ,links1 main description
 of4    ,link motion of direct acting   
screw engine4  ,link motion1 how to set4
  ,locomotive engines1    general       
description of the locomotive2          
,stephenson's locomotive2    ,gooch's   
locomotive for the wide gauge2          
,crampton's locomotive for the narrow   
gauge4  ,locomotives1 adhesion of wheels
 of1    cost and performance of2        
framing of2    cylinders of2    springs 
of2    outside and inside cylinders2    
sinuous motion of2    rocking motion of2
    pitching motion of2    pistons2     
piston rods2    guides2    cranked axle2
    axle bearings2    eccentrics2       
eccentric rod2    starting handle2      
link motion2    valves1 how to set2     
eccentrics1 how to readjust2    feed    
pumps2    connection of engine and      
tender1    driving wheels2    wheel     
tires4  ,locomotive engine of modern    
construction1 example of1    fire box2  
barrel of boiler2    tubes2    tube     
plate2    framing2    axle guards2      

draw bolt2    wheels and axles2         
cylinders2    valve2    piston2         
piston rod2    guides2    connecting    
rod2    eccentrics2    link motion2     
regulator2    blast pipe2    safety     
valve2    feed pump2    tendencies of   
improvement in locomotives4             
,locomotives1 management of4            
,locomotive boilers1 examples of modern 
proportions4  ,locomotive boilers1      
details of4  ,low pressure or condensing
 engine1 definition of4  ,lubrication of
 rubbing surfaces1    the friction      
depends mainly on the nature of         
lubricant2    oil forced out of         
bearings1 if the pressure exceeds #hjj  
lbs4 per square inch longitudinal       
section2    water a good lubricant if   
the surfaces are large enough4          
,lubrication of engine bearings4        
,mc,naught's indicator4  ,main beam1    
strength proper for4  ,main centre1     
description of1    strength proper for4 
,main links1 description of1    strength
 proper for4  ,mandrels1 expanding1 for 

tubing boilers4  ,manhole door4         
,manhole of locomotives4  ,marine flue  
boilers1 proportions of4      ,see also 
,boilers4  ,marine boilers of modern    
construction1 proper proportions of4    
,marine engines4 ,see ,steam ,engines1  
marine4  ,mastic cement for setting     
marine boilers4  ,maudslay1 ,messrs41   
boilers of ,retribution and ,great      
,western1 by1  ,mechanical powers1      
misconceptions respecting4  ,mechanical 
power1 definition of1    indestructible 
and eternal2    the sun the source of   
mechanical power4  ,metallic packing for
 pistons4  ,metallic packing for        
stuffing boxes4  ,meyer1 expansion valve
 by4  ,miller1 ,ravenhill  ,co4's mode  
of fixing piston rod to piston4  ,modern
 locomotives4  ,momentum1 or vis viva4  
,morin1 experiments on friction by4     
,mudholes of locomotives4  ,muntz's     
metal1 composition of4    ,niger and    
,basilisk1 trials of4  ,nile1 boilers of
 the1 by ,boulton and ,watt4  ,notch of 
eccentric should be fitted with brass   

bush4    ,oils for lubrication4 ,see    
,lubrication4  ,oscillation1 centre of4 
,oscillating paddle engine1 description 
of4  ,oscillating engine1 advantages of1
    futility of objections to2          
details of cylinder2    framing2        
condenser2    air pump2    trunnions2   
valve and valve casing2    piston2      
piston rod2    air pump connecting rod  
and cross head2    air pump rod2        
eccentric and eccentric rod2    valve   
gear2    valve sector2    shaft plummer 
blocks2    trunnion plummer blocks2     
feathering paddle wheels2    packing of 
trunnions4  ,oscillating engines1 how to
 erect4  ,otis's excavator4  ,outside   
and inside cylinder locomotives4        
,packing for stuffing box of ,watt's    
engine4  ,packing of piston of pumping  
engines1 how to accomplish4  ,packing of
 trunnions4  ,paddle bolts1 proper mode 
of forming4  ,paddle centres4  ,paddle  
floats4  ,paddle shaft1 description of4 
,paddle shaft1 details of4  ,paddle     
shaft plummer blocks of oscillating     

engines4  ,paddle wheels1 details of1   
structure and operation of2    slip of2 
centre of pressure of2    rolling       
circle2    action of oblique floats2    
rule for proportioning paddle wheels2   
benefits of large floats4  ,paddle      
wheels1 feathering1 description of2     
details of4  ,paddles and screw         
combined4  ,parallel motion1 description
 of1    how to lay off centres of4      
,pendulum1    cause of vibrations of2   
relation of vibrations of pendulum to   
velocity of falling bodies2    conical  
pendulum or governor4  ,penn1 ,messrs41 
engines of ,great ,britain1 by1         
direct acting screw engines by2    trunk
 engines by4  ,performance of           
locomotives4  ,pillars1 hollow1 strength
 of1    law of strength varies with     
thickness of metal4  ,pipe for receiving
 screw shaft4  ,pipes of marine engines4
  ,piston1 description of1    how to    
pack with hemp4  ,pistons1 metallic     
packing for4  ,pistons for oscillating  
engines4  ,pistons1 how to fit and      

finish4  ,pistons of locomotives4       
,piston rod1 description of1    strength
 proper for4  ,piston rods of           
locomotives4  ,piston rod of oscillating
 engine4  ,piston rods of direct acting 
screw engine4  ,pitch of the screw4     
,pitch1 increasing or expanding4        
,pitching motion in locomotives4        
,planometers1 or face plates4  ,plummer 
blocks of shafts and trunnions of       
oscillating engines4  ,plummer blocks   
for receiving thrust of screw propeller4
  ,plunger of feed pump4  ,portable     
engine1 ,hoadley's4  ,porter's patent   
governor4  ,ports of the cylinder1 area 
of4  ,pot-lid valves of air pump4       
,powers1 mechanical1    misconception   
respecting4  ,power1 horses1 definition 
of1    nominal and actual power2        
power of high pressure engines4  ,power 
necessary for thrashing and grinding    
corn1 working sugar mills1      spinning
 cotton1 sawing timber1 grossing cotton1
 blowing furnaces1      driving piles1  
and dredging earth out of rivers4       

,pressing cotton1 power necessary for4  
,priming1 nature and causes of4         
,priming1 if excessive1 may occasion    
explosion4  ,propeller1 screw1          
description of4  ,proportions of screws 
with1 two1 four1 and six blades4        
,proving of boilers4  ,prussiate of     
potash for case hardening4  ,pumping    
engines1 mode of erecting1    mode of   
starting4  ,pumps1 loss of effect in1 at
 high speed and with hot water1         
causes of this loss2    remedy for4     
,pumps used for mines4  ,pump1 air1     
description1 of1    action of4  ,pumps1 
air1 proper proportions of1    single   
and double acting4  ,pump1 centrifugal1 
better than common pump4  ,pump1 cold   
water1 description of4  ,pump1 feed1    
description of1    action of2    proper 
dimensions of2    rule for              
proportioning2    plunger of2    valves 
of2    independent4  ,pump valves for   
mines1 c4  ,punching and shearing boiler
 plates4    ,railway wheels1 bursting   
velocity of4  ,railway trains1          

resistance of4  ,rarefaction or         
exhaustion produced by chimneys4        
,rattler and ,alecto1 trials of4        
,registration1 benefits of4  ,regnault1 
experiments on heat by4  ,regulator1 a  
valve for regulating the admission of   
steam in locomotives1    description of2
    various forms of4  ,regulator1      
,clark's1 patent steam and fire4        
,rennie1 experiments on friction by4    
,resistance1 experienced by railway     
trains4  ,resistance of vessels in      
water1    mainly made up of friction2   
experiments on4  ,resistance and speed  
of vessels influenced by their size4    
,retribution1 boilers of1 by ,messrs4   
,mandslay4  ,riveting and caulking of   
land boilers4  ,rocking motion of       
locomotives4  ,rolling circle of paddle 
wheels4  ,rotatory engines1 definition  
of4  ,rotative engines1 definition of4  
,rust joints1 how to make4    ,safety   
valve1 area of1 in low pressure engines1
    in locomotives4  ,salinometer1 or   
salt gauge1 how to use1    how to       

construct4  ,salt1 accumulation of1     
prevented in marine boilers by blowing  
off1   if allowed to accumulate in      
boilers may occasion explosion2         
amount of1 in sea water4  ,salt water   
produces surcharged steam4  ,salting of 
boilers1 what to do if this takes place4
  ,sawing timber1 power necessary for4  
,scale in marine boilers4 ,see also     
,salt4  ,scale preventer1 ,lamb's4      
,scrap iron1 unsuitable for case        
hardening4  ,scraping tools for metal   
surfaces4  ,screw4  ,screw engine1      
geared oscillating1 description of1     
direct acting1 description of4  ,screw  
engine1 direct acting1 by ,messrs4 ,john
 ,bourne  ,co4  ,screw engines1 best    
forms of4  ,screw frame in deadwood4    
,screw propeller1 description of4       
,screw propeller1 mode of fixing on     
shaft1    modes of receiving thrust2    
apparatus for lifting2    configuration 
of2    action of2    pitch of the screw2
    screws of increasing or expanding   
pitch2    slip of the screw2    positive

 and negative slip2    screw and paddles
 compared2    test of the dynamometer2  
trials of ,rattler and ,alecto1 and     
,niger and ,basilisk2    indicator and  
dynamometer power2    loss of power in  
screw vessels in head winds2    the     
screw should be deeply immersed2        
screws of the ,earl of ,dundonald1      
,hodgson1 ,griffith1 ,holm1 and         
,beattie2    lateral and retrogressive  
slip2    sterns of screw vessels should 
be sharp2    proportions of screws with 
two1 four1 and six blades2    screw     
vessels with auxiliary power2    screw  
and paddles combined2    economy of fuel
 in steam vessels2    benefits of       
registration4  ,screw  propeller1       
,holm's conchoidal4  ,screw shaft1      
details of4  ,screw shaft pipe at stern4
  ,screw shaft brasses of direct acting 
screw engines4  ,sea water1 amount of   
salt in4  ,sea injection cocks4         
,setting of wagon boilers1    of marine 
boilers4  ,setting the valves of        
locomotives4  ,shaft1 paddle1 details   

of4  ,shaft of screw propeller1 details 
of4  ,shafts1 strength of4  ,shank's    
steam gauge4  ,shocks may not be well   
resisted by iron that can well resist   
strains1    effect of inertia in        
resisting shocks4  ,side levers or      
beams1 description of4  ,side lever     
marine engines1 description of4  ,side  
lever engines1 how to erect4  ,side     
rods1 description of1    strength proper
 for4  ,silsbee1 ,mynderse  ,co4's steam
 fire engine4  ,single acting engines1  
definition of4  ,single acting or       
pumping engines1    mode of erecting2   
mode of starting4  ,sinuous motion of   
locomotives4  ,slide valve1    various  
forms of2    long ,d and three ported   
valve1 description of2    action of the 
slide valve2    lead and lap of the     
valve2    rules for determining the     
proportions of valves2    advantages of 
lead in swift moving engines4  ,slide   
valve1 equilibrium4  ,slide valve with  
balance piston of direct acting screw   
engine4  ,slide valve1 how to finish4   

,slide valves of marine engines1 how to 
set4  ,slip of paddle wheels4  ,slip of 
the screw1    positive and negative     
slip2    lateral and retrogressive slip4
  ,smoke1 modes of consuming4  ,smoke   
burning furnaces1    ,williams's argand2
    ,prideaux's2    ,boulton and ,watt's
 dead plate2    revolving grate2        
,juckes's2    ,maudslay's2    ,hall's1  
,coupland's1 ,godson's1 ,robinson's1    
,stevens's1 ,hazeldine's1 c4      ,snake
 locomotive4  ,southern1    experiments 
on friction by2    experiments on steam 
by4  ,specific heat1 definition of4     
,speed of vessels influenced by their   
size4  ,spheroidal condition of water in
 boilers4  ,springs of locomotives4     
,stand pipe for low pressure boilers4   
,starting handle of locomotives4        
,staying of boilers4  ,staying tube     
plates1 mode of4  ,staying fire boxes of
 locomotives4  ,steam1 experiments on by
 ,southern1 ,french ,academy1 ,franklin 
,institute1      and ,m4 ,regnault4     
,steam pump1    ,worthington's2         

,woodward's4  ,steam and water1 relative
 bulks of4  ,steam1    expansion of2    
pressure of2    inversely as space      
occupied2    ,see also ,expansion of    
,steam4  ,steam engine1 applications and
 appliances of the4  ,steam engine1     
general description of ,watt's double   
acting engine2    ,r4 ,hoe  ,co4's2     
,corliss's2    ,woodruff  ,beach's4     
,steam engine1    various forms of1 for 
propelling vessels2    paddle engines   
and screw engines2    principal         
varieties of paddle engines2            
different kinds of paddle wheels2    the
 side lever engine2    description of   
the side lever engine2    oscillating   
paddle engine2    description of        
feathering paddle wheels2    direct     
acting screw engine4  ,steam dome of    
locomotives4  ,steam fire engine1       
,latta's4    ,amoskeag4    ,silsbee1    
,mynderse  ,co4's4  ,steam gauge1       
,bourdon's2    ,shank's4  ,steam jacket1
 benefits of2  ,steam passages1 area of2
  ,steam room in boilers2  ,steam1      

surcharged1 law of expansion by heat2   
,steel1 strength of2  ,stephenson1 link 
motion by2  ,stop valves between        
boilers2  ,straight edges2  ,strains    
subsisting in machines2  ,strain proper 
to be put upon iron in engines2         
,strains in machines1    vary inversely 
as the velocity of the part to which the
 strain is  applied4    aggravated by   
being intermittent4    increase of      
strain due to deflection4    effects of 
alternate strains in opposite           
directions4  ,strength of materials4    
,strength of hollow pillars1    law of2 
strength varies with thickness of metal4
  ,strength of cast iron to resist      
shocks does not vary as the strength    
to resist strains1    increase of       
strength by combination with cast iron4 
,strength of boilers1    experiments on1
 by ,franklin ,institute2    by ,mr4    
,fairbairn2    mode of computing2       
mode of staying for strength4  ,strength
 of engines3 cylinder1    trunnions2    
piston rod2    main links2    connecting

 rod2    studs of the beam2    gudgeons2
    working beam2    cast iron shaft2   
malleable iron shaft2    teeth of       
wheels2    side rods2    crank2    crank
 pin2    cross head2    main centre2    
gibs and cutter4  ,studs1 strength      
proper for4  ,stuffing box1 description 
of4  ,stuffing boxes with metallic      
packing1    with sheet brass packed     
behind with hemp2    sometimes fitted   
with a lantern1 brass4  ,sugar mills1   
power necessary to work4  ,summers'     
experiments on the friction of rough    
surfaces4  ,surcharged steam1 law of    
expansion of1 by heat4  ,surcharged     
steam produced by salt water1           
corrosive action of4  ,surfaces1 how to 
make true4  ,sweeping the tubes of      
boilers clean of soot4    ,teeth of     
wheels4  ,telescope chimneys4  ,tender  
of a locomotive1 description of1        
attachment of1 to engine4  ,thrashing   
corn1 power necessary for4  ,throttle   
valve1 description of4  ,thrust of the  
screw propeller1 modes of receiving4    

,thrust plummer block4  ,tires of       
locomotive wheels4  ,traction on        
railways4  ,trunk engine by ,messrs4    
,rennie1 disadvantages of4  ,trunk      
engines by ,messrs4 ,penn4  ,trunnions  
of oscillating engines1 description of1 
strength proper for2    details of4     
,trunnion packing4  ,trunnion plummer   
blocks4  ,tube plates1 mode of staying4 
,tube plates of modern locomotives4     
,tubes of modern locomotive boilers4    
,tubes of boilers1 how to sweep clean of
 soot4  ,tubing of boilers4  ,tubing    
locomotive boilers4    ,valve1          
atmospheric4  ,valve casing1 description
 of4  ,valve casing should have         
expansion joint4  ,valve and valve      
casing of oscillating engine4  ,valve   
delivery1 description of1    action of  
,valve1 equilibrium slide4  ,valve1     
foot1 description of1    action of4     
,valve gear of ,watt's engine1    action
 of4  ,valve gear of oscillating engine4
  ,valve1 gridiron4  ,valve1 slide4 ,see
 ,slide ,valve4  ,valve1 slide1 how to  

finish4  ,valves1 ball1    ,belidor's   
might be used for foot and delivery     
valves2    butterfly1 of air pump2      
concentric ring1 for air pump bucket4   
,valves1 equilibrium4  ,valves1 escape1 
for cylinders4  ,valves1 expansion4 ,see
 ,expansion ,valves4  ,valves of feed   
pumps4  ,valves1 india rubber1 for air  
pump4  ,valves1 ,kingston's4  ,valves of
 locomotives1 how to set4  ,valves1     
pot-lid1 of air pump4  ,vacuum1 meaning 
of1    nature and uses of2    how       
maintained in engines4  ,vacuum         
sometimes occurs in boilers1    evils of
 a vacuum in boilers4  ,vacuum1 velocity
 with which air rushes into a4  ,vacuum 
gauge1    ,bourdon's4  ,velocity of air 
entering a vacuum4  ,velocity of falling
 bodies4  ,vent of boilers1 definition  
of4  ,vessels1 resistance of1    mainly 
made up of friction in good forms2      
experiments on2    influence of size4   
,vis viva1 or mechanical power4         
,waste steam pipe4  ,waste water pipe4  
,water required for condensation1       

pumps for supplying4  ,watt's double    
acting engine1 description of4  ,wedge4 
,wheels1 toothed1 for screw engines4    
,wheels1 teeth of4  ,wheels of          
locomotives1 adhesion of4  ,wheels1     
driving1 of locomotives4  ,wheel tires4 
,wheels and axles of modern locomotives4
  ,wood1 experiments on friction by4    
,wood1 evaporative efficacy of4         
,woodman's steam pump4  ,woodruff       
,beach's steam engine4  ,working beam of
 land engine1 description of4           
,worthington's steam pump1    duplex    
pump4      ,,the ,,end4