340 Prof. Clausius on the Application of the Mechanical 

 The second^ for machiues without oondenseFs^ is- - m . 



"^aoao^'^ • • • • (^^*^ 



which is most correct between 2 and 6 atmospheres, though the 

 range of its applicability extends from about I5 to ]0 atmo- 

 spheres. • i!'»;ii // k'-,<Ki>ai 8HiJ .^ txli h 



30. The magnitudes dependerit ti^on the dimensions of the 

 steam-engine, which enter into the determination of the work, 

 shall be here^ somewhat differently from Pambour's method, 

 represented in the following manner. Let vf be the whole space 

 left free to the vapour during a stroke in the piston, the vicious 

 space being also included. Let the vicious space form a frac- 

 tional part € of the whole space, so that this space itself will be 

 represented by et/, and that described by the surface of the pis- 

 ton by (1— e)r'. Further, let the part of the whole space left 

 free to the vapour up to the moment of disconnecting the cylinder 

 and boiler (also inclusive of vicious space) be represented by ei/. 

 Consequently the space described by the surface of the piston 

 during the entrance of the vapour will be expressed by {e—e)vf, 

 and that described by the same during expansion will be (1 —e)v^. 



In order to determine, in the next place, the amount of work 

 done dunng the entrance of the vapour, the pressure acting in 

 the cylinder during this time must be known. This is at any 

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

 of vapour could occur ; but the magnitude of the difference can- 

 not in general be stated ; for it depends not only upon the con- 

 struction of the engine, but also upon the engine-driver, how 

 far he has opened the valve in the tube leading from the boiler, 

 and with what velocity he drives the machine. These things 

 being changed, the above difference may vary between wide 

 limits. Further, the pressure in the cylinder need not be con- 

 stant during the whole time of influx, because the velocity of the 

 piston may vary, as well as the magnitude of the influx orifice left 

 free by the valve or the slide. 



With respect to the last circumstance, Pambour assumes that 

 the mean pressure to be brought into calculation in determining 

 the work may, with sufficient accuracy, be set equal to that which 

 exists in the cylinder at the end of the influx, and at the moment 

 of disconnexion from the boiler. Although I do not think it 

 advisable to introduce such an assumption — which is only adopted 

 for numerical calculation in the absence of more certain data — at 

 once into the general formulae, yet here, whilst explaining his 

 theory, I must adopt his method." —y.^' 



Pambour determines the pressure existing in the cylinder at 

 the moment of disconnexion by means of the relation, established 



