Mr. R. H. M. Bosanquet on the Theory of Sound. 277 



cannot at present account for, just as we cannot decompose it 

 chemically*? 



I suppose, however, that the principal objection would have 

 been that the experimental data were not consistent with the 

 hypothesis. In answer it seems to be enough to look at the 

 Table at the beginning of this note ; we can say without hesi- 

 tation that, giving due weight to Regnault's experiments, it is 

 impossible to conclude with any certainty whether the true 

 value of the ratio of specific heats lies above or below 1'40. 



At the same time, since there must be internal work done 

 in the atoms in some way that we do not comprehend, though 

 it is probably very small, we may regard such a value as Reg- 

 nault's (1-3945) as compatible with a possible explanation, 

 since with such a value the total vis viva is slightly greater 

 than that due to the 5 degrees of freedom. 



The admission of the number 1*40 as a working constant 

 involves relations between the mechanical equivalent of heat 

 and the specific heat of air at constant pressure. 



The following numbers indicate the nature of the relation, 

 the ratio of specific heats of air being taken at 1*40: — 



Mechanical 



Specific heat at constant 



equivalent. 

 431 

 429 

 424 (Joule) 



pressure. 

 •2377 (Regnault)f 

 •2389 (Wiedemann) 

 •2416 



Regnault's own computation of the mechanical equivalent 

 gives 436*1. 



A comment of Professor Foster on recent determinations in 

 the Supplement to Watts's ' Dictionary of Chemistry (1872, 

 p. 687), after noticing the general accordance of modern 

 results in values higher than Joule's original number (424), 

 proceeds: — " Joule's new result (429*3) is the lowest of three 

 values obtained in distinct sets of observations ; but it is 

 adopted by him as the result of the investigation, in conse- 

 quence of more complete precautions to ensure accuracy having 

 been taken in the set of experiments from which it was deduced 



* There is nothing to prevent us from forming the conception of very 

 small amounts of energy existing in some way or other within an atom 

 (regarding this as already complex in a manner which we do not under- 

 stand), though we are unable to give any accurate account of the way in 

 which the movement is originated or maintained. 



t .Regnault's determinations varied from -23536 to *23890, Wiede- 

 mann's from -2374 to -2414 (Pogg. Ann. vol. clvii. p. 21). This last limit 

 comes very near the number required by Joule's value of the equivalent. 



