
AND ITS CONNECTION WITH THE THEORY OF HEAT. 433 
fore, for every substance in nature, the mean specific gravity of the atomic atmosphere 
in the theoretical state of perfect gas is inversely proportional to the specific elasticity 
of that atmosphere. 
Real specific heat may also be thus expressed :— 
Vv, AM , 
Oe oma en See te POS 
kM, 3kM 1 
2 | 2 2 fe eM. 
The fitter factor appears to depend on the chemical constitution of the sub- 
stance, being the same for all simple gases. 

in which Y2 epee to ¢ se in my former papers, and 4 
(8.) Total Pressure of Substances in general, expressed in terms of temperature. 
In equation (9) let be put for @: then 


h KG’ K2 Go” 
P=p+f(V)=F(V) + ET G+ {6,5 4 ON _ be, } 


KM 
ps Ni ee { Ay AL AS 
aif (sk a De ae 73 — &e, | ; : (21.) 
where 
—k G’ K? } 3 
A, = G, 3 A, = aay “Rie 
3 
A,=- Gs (G,2— 2G,’ G+”); &e. 
This formula is identical with that which I employed in my former paper, to 
represent the pressure of an imperfect gas, and which I found to agree with M. 
REGNAULT’s experiments, when the coefficients A and the function f (V) had been 
calculated empirically. 
Section Srconp.—Relations between Heat and Expansive Power. 
(9.) Variations of Sensible and Latent Heat: Fundamental Equation of the 
Theory —If the forms, positions, and magnitudes of the paths described by the 
revolving particles of the atomic atmospheres be changed, whether by a variation 
of mean density, or by a variation of temperature, an increase or diminution of 
the vis-viva of their motion, that is to say, of the heat of the body, will take place 
in virtue of that change of the paths of motion; an increase when they are con- 
tracted, and a diminution when they are dilated. 
Let 6 . Q represent, when positive, the indefinitely small quantity of heat which 
must be communicated to unity of weight of a substance, and when negative, 
that which must be abstracted from it, in order to produce the indefinitely small 
variation of temperature 6 7 simultaneously with the indefinitely small variation 
VOL. XX. PART III. 6a 
