Mr. W. J. M. Raukino on ike Mechanical Action of Heat. i253 



(44.) This approximation having been adopted, I believe it 

 will be found that the formula (66), although very different in 

 appearance from that arrived at by Professor Thomson, gives 

 nearly the same numerical results. For example : let the machine 

 work between the temperatures 140° and 30° Centigrade; then 

 T, =414^-6, T„=304"-6, and 



•^=0-2653. 

 ill 



Professor Thomson has informed me, that for the same tem- 

 peratures he finds this ratio to be 0"2713*. 



(45.) To make a steam-engine work according to the con- 

 ditions of maximum effect here laid down, the steam must enter 

 the cylinder from the boiler without diminishing in pressure, 

 and must be worked expansively down to the pressure and tem- 

 perature of condensation. It must then be so far liquefied by 

 conduction alone, that on the liquefaction being completed by 

 compression, it may be restored to the temperature of the boiler 

 by means of that compression alone. These conditions are un- 

 attainable in steam-engines as at present constructed, and dif- 

 ferent from those which form the basis of the formulae and tables 

 in the fourth Section of this paper ; hence it is found, both by 

 experiment and by calculation from those formulae, that the pro- 

 portion of tlie total heat converted into power in any possible 

 steam-engine is less than that indicated by equation (66). 



The annexed table illustrates this : — 



