W. A. Norton—Force of Effective Molecular Action. 448 
occupied by the same number of molecules when the distance 
etween their centers is 1. 
If now we take account of the attractive impulses answering 
to the attractive term in equ. (1), it is plain that by a similar 
investigation we shall obtain for the diminution, d, of the elastic 
pressure at O, d=2H’. Accordingly for the actual pressure on 
an elementary area at O, we have 
py Age ae et deg 
where T” denotes the entire energy of the attractive waves 
that occupy at any instant a hemisphere described around O 
with the radius 1. It may be shown that unless the number 
of atmospheres of pressure be great, f(V)=const. (V)’, approx- 
imately. This expression for P is, essentially, the counterpart 
to the value of p given in the equation of Clausius (p. 441). 
are entirely inapplicable to the present theory. : 
For calculating the gaseous pressure in atmospheres I obtain 
the formula 
kg(34- 
eee a( ai gt 288-°5 42° 
P=1X¢(1— cna Ss Car) 
3\2 3\e 
12,924(1455) (+8) 
in which == ratio of the volume, in the case of an ideal gas 
for which £=0 and ae = os answering to the assumed value 
of u, to the volume at the pressure of one atmosphere, and the 
mean temperature, 15° c. occupied by the same number of 
molecules; ° = temperature above the mean taken as a zero 
point, k = ratio of coefficients of attraction and repulsion, as 
efore, for the gas and temperature considered. The value of 
k varies with the temperature. We have already seen (p. 439) 
