DR. A. SCOTT ON THE COMPOSITION OE WATER BY VOLUME. 549 
Before beginning a series of experiments the apparatus was carefully exhausted by 
filling A, B, and C with mercury, as well as the tubes leading to the bulbs No and Nn, 
by having the taps open, and by raising the reservoir M^, closing all the taps 1, 3, 4, 5, 6, 
and 7, then lowering and opening tap 5, which opened communication v/ith the 
General view of apparatus from front, showing catlietometer. 
hydrogen generating apparatus, being lowered until the mercury fell to D. Then 
tap 5 was closed and Mj raised till the air was under more than atmospheric pressure, 
tap 6 opened and the air inside the apparatus expelled by forcing mercury up into 
.the bulb Nfj, This was repeated till no more air could be thus pumped out. A 
little hydrogen was now generated and pumped out, and the process repeated twice. 
Eis’. 4. 
