366 



R. Clausius on the Application of the 



free for the steam up to the moment of cutting off the cylinder 

 from the boiler, including also the injurious space, be denoted by 

 ev'. Hence the space described by the surface of the piston, 

 during the entrance of the steam will be expressed by (e—e)v' 

 and the space described during the expansion by (1— e)v'. 



In order now, in the first place, to determine the work done, 

 during the admission of the steam, the active pressure in the 

 cylinder during this time must be known. This is, in any event, 

 smaller than the pressure in the boiler, since otherwise no influx 

 of steam would take place ; it cannot however be generally 

 stated how great this difference is, since it not only depends upon 

 the arrangement of the machine, but also upon how wide the 

 engineer has opened the valve in the steam pipe, and upon the 

 velocity with which the machine moves. This difference may 

 vary between wide limits by changing these conditions. The 

 pressure in the cylinder also is not necessarily constant during 

 the whole time of the influx, because both the velocity of the 

 piston and the magnitude of the influx opening left free by the 

 steam valve pr slide valve are variable. 



Pambour assumes with reference to the last condition, that the 

 mean pressure which is to be brought into the calculation in de- 

 termining the work, can with sufficient accuracy be supposed 

 equal to the pressure which is exerted in the cylinder at the end 

 of the influx, at the moment of cutting off from the boiler. 

 Though I do not consider it advantageous to introduce directly 

 into the general formulas such an assumption, which is made 

 only for the sake of numerical calculation in the absence of more 

 certain data, yet I must here follow his process in setting forth 

 his theory. 



Pambour determines the pressure which takes place in the 

 cylinder at the moment of the cut-off by means of the relation 

 established by him between volume and pressure, inasmuch as 

 he thereby supposes that the quantity of steam passing into the 

 cylinder, during the unit of time and consequently also, during 

 one stroke of the piston, is known by special observations. We 

 will as before denote by M the whole mass which enters the cyl- 

 inder during a stroke of the piston, and that portion of it which 

 is in the form of steam by m. As this mass, of which Pambour 

 only considers the portion which is in the form of steam, fills the 

 space ev' at the moment of the cut-off, we have, if we denote the 

 pressure at this moment by p 2 according to equation, (29) 



m.B 



ev'zz , 



whence we have 



('> 0 -) p 2 =— r --b. 



