Prof. Thomson on the Dynamical Theory of Heat. 175 



pears in equation (33), except h, is known with tolerable accuracy 

 for saturated steam through a wide range of temperatm-e ; and 

 we may therefore use this equation to find h, which has never 

 yet been made an object of experimental research. Thus we have 



, 7— A, dp ((TL \ 



For the value of 7 the best data regarding the density of satu- 

 rated steam that can be had must be taken. If for different 

 temperatm-es we use the same values for the density of satm-ated 

 steam (calculated according to the gaseous laws, and Regnault^s 

 observed pressm-e from -—r^, taken as the density at 100°), the 

 values obtained for the first term of the second member of the 

 preceding equation are the same as if we take the form 



--¥-(§-) 



derived from (34), and use the values of fx. shown in Table I. of 

 my former paper. The values of — ^ in the second column in 

 the following table have been so calculated, with, besides, the 

 following data afforded by Regnault from his observations on 

 the total heat of steam, and the specific heat of water 



^+c=-805. 

 at 



L = 606-5 + -305^ - (-00002/2 + -0000003/3) . 



The values of —h shown in the third column are those derived 

 by Clausius from an equation which is the same as what (34) 



would become if J 



E 



1+E/ 



were substituted for yu,. 



59. From these results it appears, that through the whole 

 range of temperatures at which observations have been made, 

 the value of h is negative ; and, therefore, if a quantity of satu- 

 rated vapour Ijc compressed in a vessel containing no liquid 

 water, heat must be continuously abstracted from it in order 



