lO CLARKE 



our study of all the available data, but we may for present 

 purposes assign to it the rounded-off magnitude of 13700 

 calories, which is close enough for preliminary application. 

 This is the commonly accepted value of the neutralization 

 constant. 



Let us now recur to the typical equation for methane, 



X -\- 2y — 2z — r = 191 084 calories, 



and analyze it in terms of henotherms. 



a:'= 12 henotherms. 

 2jy = 6 X 2 henotherms. 

 — 2z = — 2 henotherms. 

 — r = — 8 henotherms. 



Sum = 14 henotherms = 191 800 calories. 



This quantity exceeds Thomsen's average, as given above, by 

 only 0.37 per cent. But Thomsen's separate determinations 

 vary among themselves by 0.99 per cent., so that the agree- 

 ment between measurement and calculation is most satisfactory. 

 The Berthelot value, as already cited, is even closer, being, for 

 gaseous substances throughout, 191 554 calories. Other com- 

 parisons between observation and theory will be given later in 

 this memoir, when the magnitude of the henotherm shall have 

 been more definitely fixed. Meanwhile, we may take the fol- 

 lowing absolute heats of combination as approximately estab- 

 lished, in order that we may apply them to future use : 



These follow from the general formula in the manner already 

 indicated ; but they differ in some respects from the estimates of 

 previous computers. Thus Thomsen ^ finds, for the heat of 

 combustion of an isolated carbon atom, the value 135 340 calo- 



1 Therm. Unt., vol. iv, pp. 257-260. 



