192 MR W. J. M. RANKINE ON THE 

Speciric HeAtT OF ATMOSPHERIC AIR AS COMPARED WITH Liquip WATER.—(Section IT 
Article 14.) 
The dynamical values of the specific heat of atmospheric air are calculated 
independently from the velocity of sound, without reference to the specific heat 
of liquid water; and from the closeness of the agreement of the experiments of 
M.M. Bravais and Martins, Mott and Van Berek, STaAmprer and Myrpacn, 
Werruerm and others, it is clear that the limits of error are about 335 for the 
velocity of sound, 735 for the ratio, and from 75 to go for the dynamical values of 
the specific heat of air, at constant volume and constant pressure. Those values, 
as given by Equation 27, are— i 
Real specific heat,— 
k =238-66 feet =72°74 metres per centigrade degree. 
=132'6 feet per degree of Fahrenheit. 
Apparent specific heat under constant pressure,— 
K,=3834 feet =101°8 metres per centigrade degree. 
=185'6 feet per degree of Fahrenheit. 
The ratio of these two quantities being taken as 
= if eNi== ed 
The dynamical equivalent of the specific heat of liquid water, as determined 
by Mr Jou xe, is 
Ky =1889°6 feet =423:54 metres per centigrade degree. 
=772 feet per degree of Fahrenheit. 
The specific heat of air, that of liquid water being taken as unity, has there- 
fore the following values :— 
Real specific heat,— 
132°6 
K, =D, => 0 vale 
Apparent specific heat under constant pressure,— 
K, _ 185°6 
Sy WE 
This last quantity, according to DE La Rocue and BERARD, is 
0:2669 

The discrepancy being, ; ; 0:0265 
or one-ninth of the value according to Mr Jounn’s equivalent. 
Sprciric Heat or STEAM. (Section III. Art. 20.) 
The apparent specific heat of steam (Eq. 34 and 36) as a gas under constant 

