582 MR W. J. M. RANKINE ON THE 
Com. log 2 = 21101845 ; log 1°. “= 3:4017950; 
0 
and these values suit any scale of temperatures. 
In calculating, for use in these formule, the densities = from the observed 
pressures, it is sufficiently near the truth, in the case of air, to use the approxi- 
mate equation 
—_— = ” - P (m atmospheres). 
The common logarithm of r,, the absolute temperature of melting ice, for the 
centigrade scale, is 24387005. 
The constant N for atmospheric air is 0°4 nearly; therefore 
Com. log (N x hyp. log 10) = 1-9642757. 
The following, therefore, is the approximate value of the formula (103), to be 
used (with the numerical constants already given) in reducing the experiments of 
Mr Joune and Professor THomson on atmospheric air, so as to obtain approximate 
values of the absolute temperature of total privation of heat :— 
p= { INP Ge : (=) eae : ()—20 (7) " A -@) —(—Art) } 
T 

— N hyp. log 10 x A . com. log = : . - : : (108.) 
In using this formula, the mean absolute temperature should be taken as the 
value of r. 
The following table shews the values of the quantity x, computed from ten 
mean experimental data, taken respectively from the first ten series of experi- 
ments described in the recent paper of Messrs JouLE and Tuomson, in the supple- 
mentary number of the Philosophical Magazine for December 1852. The tempe- 
ratures in the table, for the sake of convenience, are reduced to the centigrade 
scale, because that scale has been used throughout the previous sections of this 
paper. 
The final pressure in each case was that of the atmosphere. 
Vs 
