198 LORD RAYLEIGH AND PROFESSOR W. RAMSAY ON ARGON, 
per hour, or 30 times as fast as CAVENDISH could work with the electrical machine 
of his day. 
To take an example, one experiment of this kind started with 50 cub. centims. of air. 
To this, oxygen was gradually added until, oxygen being in excess, there was no 
perceptible contraction during an hour’s sparking. The remaining gas was then 
transferred at the pneumatic trough to a small measuring vessel, sealed by mercury, © 
Fig. 1. 

































































PMI 

a 
in which the volume was found to be 1:0 cub. centim. On treatment with alkaline 
pyrogallate, the gas shrank to 32 cub. centim. That this small residue could not be 
nitrogen was argued from the fact that it had withstood the prolonged action of the 
spark, although mixed with oxygen in nearly the most favourable proportion. 
The residue was then transferred to the test-tube with an addition of another 
50 cub. centims. of air, and the whole worked up with oxygen as before. The residue 
was now 2°2 cub. centims., and, after removal of oxygen, ‘76 cub. centim. 
