PROFESSOR THOMSON ON THE SPECIFIC HEATS OF ^IR. 
82 . 
The very accurate observations which have been made on the velocity of sound in 
air, taken in connection with the results of Regnault’s observations on its density, 
&c., lead to the value T410 for h, which is probably true in three if not in four of 
its figures. Now, h being known, the preceding equations enable us to determine 
the absolute values of the two specific heats (A:N, and N) according to the hypo- 
theses used in {a) and in (a') respectively ; and we thus find. 
Specific heat of air under Specific heat of air in 
constant pressure (^N). constant volume (N). 
for t— 0, ... . ’2431 . . 
for #=10, .... -2410 . . 
Or, for all temperatures, *2374 . ' . 
T 724,1 according to the tabulated 
*1709,/ values of Carnot’s function. 
1684 I according to Mayer’s hy- 
) pothesis. 
By the adoption of hypotheses involving that of Mayer, and taking 1389'6 and T4 
as the values of J and k, respectively, Mr. Rankine finds '2404 and '1717 as the 
values of the two specific heats. 
Hence it is probable that the values of the specific heat of air under constant 
pressure, found by Suermann (*3046), and by De la Roche and Berard ('2669), 
are both considerably too great ; and the true value, to two significant figures, is 
probably *24. 
Glasgow College, 
February 19, 1852. 
