452 TRANSACTIONS OF SECTION A. 
vapour-pressure curve in the univariant system of a vapour in contact with its 
own liquid, and is analogous to it in form. 
Ramsay and Young’s law for the ratios of absolute temperatures of two 
vapours at the same pressure was then applied to these results in the form 
where T, T,’ are the absolute temperatures, read from one of the isostere curves, 
corresponding to two pressures, and T,, T,,’ the absolute temperatures of any other 
vapour taken as standard, at the same two pressures. Water, oxygen, and argon 
were successively taken as standards, and the equation was found to hold for all 
concentrations. A series of straight lines, one for each ccncentration, was thus 
obtained. 
It has been shown by Professor Porter that Ramsay and Young’s law 
n 
may be directly derived from Bertrand’s vapour-pressure formula P=G ra 
provided that the constant is the same for all vapours. For a large range of 
vapours it is found that if »=50 very good correspondence is obtained, and this 
was found also to be the case with the results of the present experiments. 
Values of the other constants a and g were calculated for each concentration 
as well as for argon vapour itself. 
An attempt hae been made to correlate these constants with the numbers repre- 
senting the actual concentrations, and, in order to introduce the argon-vapour 
constants at a finite concentration, these were calculated in terms of weight of 
argon in 100 gms. of the mixture—a method frequently used in the case of 
solutions. The concentrations experimentally reached varied from 0°317 to 7-089 
per cent., the vapour in the absence of charcoal being represented by 100 per cent. 
For convenience, the logarithms of the concentrations were plotted against 
values of a and G respectively, and a smooth curve was obtained terminating at 
100 per cent. in the constants for argon. 
Kquations were then obtained which express with considerable accuracy these 
curves, and when introduced into Bertrand’s equation the corresponding tempera- 
tures or pressures calculated for any concentration are in very fair agreement with 
those experimentally found, except for exceedingly small concentrations. 
These equations are 
Poet Soe » 100 
a=13 1243 { log + 
100 
log g= "1085-0124 log 10 
9 ye OF 
where g=(G)°° 
The values 13:12 and 0:1085 are the values respectively of a and log g for argon 
vapour. The equations given in this paper are in much better agreement with 
observation than the usually applied logarithmic or exponential equations for the 
isothermals. 
3. Report of the Seismological Committee.—See Reports, p. 83. 
4. The Density of the Ether. By Sir Ottver Lover, F.R.S. 
1. The theory that an electric charge must possess the equivalent of inertia 
was clearly established by J. J. Thomson in the ‘ Phil. Mag.’ for April 1881. 
2. The discovery of masses smaller than atoms was made experimentally by 
J. J. Thomson, and communicated to Section A at Dover in 1889. 
3. The thesis that the corpuscles so discovered consisted wholly of electric 
charges was sustained by many people, and was clinched by the experiments of 
Kaufmann in 1902, 
