57 
Ordinary Meeting, February 18th, 1873. 
E. W. Binney, F.RS., F.G.S., Vice-President, in the Chair. 
Dr, Joule, F.RS., gave some 
further account of the improve- 
ments he had made in his air 
exhausting apparatus. As 
stated in the last Proceedings, 
he had substituted a caout- 
chouc tube attached to the 
neck of a glass vessel, for the 
original perpendicular pipe 
v u j '^op-cock. This is 
seen in the "ng sketch c 
and d. The fitions, viz. 
when b is being led, and 
when it is being emptied, are 
shown by the full and the dot- 
ted drawing. It is convenient 
to introduce no air into d ex- 
cept that required to act as a 
cushion to avoid a shock when 
filled in the lower position. 
Sulphuric acid may be intro- 
duced into the receiver to be 
exhausted, but it is perhaps 
more convenient to place it 
over the mercury in a, whence 
it may occasionally be drawn 
into 6, to effect the drying of 
the internal parts of the appa- 
ratus. Dr. Joule has met with 
some difficulty in using mer- 
cury gauges to ascertain the 
residual pressure, inasmuch as 
Proceedings — Lit. & Phil. Society. — Yol. XII. — Xo. 7. — Session 1S72-3. 
