12 
PEOFESSOE TYNDALL ON THE ABSOEPTION .AND 
Table, expresses the absorption ; the third column contains the absorption, calculated on 
the supposition that it is proportional to the density. 
Table II. — Olefiant Gas. 
Unit-measure ^^th of a cubic inch. 
Absorption. 
Measures of gas. 
Observed. 
^ 
Calculated. 
1 
2-2 
2-2 
2 
4-5 
4-4 
3 
6-6 
6-6 
4 
8-8 
8-8 
5 
11-0 
11-0 
G 
12-0 
13-2 
7 
14-8 
15-4 
8 
16-8 
17-6 
9 
19-8 
19-8 
10 
, 22-0 
22-0 
11 
24-0 
24-2 
12 
25-4 
26-4 
13 
29-0 
28-6 
14 
30-2 
29-8 
15 
33-5 
33-0 
This Table shows the correctness of the foregoing surmise, and proves that for small 
quantities of gas the absorption is exactly proportional to the density. 
Let us now estimate the tensions of the quantities of gas Avith Avhich we have here 
operated. The length of the experimental tube is 48 inches, and its diameter 2-4 inches ; 
its volume is therefore 218 cubic inches. Adding to this the contents of the cocks and 
other conduits Avhich led to the tube, we may assume that each fiftieth of a cubic inch of 
the gas had to diffuse itself through a space of 220 cubic inches. The tension, therefore, 
of a single measure of the gas thus diffused would be ri.i'odth of an atmosphere, — a 
tension capable of depressing the mercurial column connected Avith the pump a-^yth of 
an inch, or about ly-th of a millimetre ! 
But the absorptive energy of olefiant gas, extraordinary as it is shoAvn to be by the 
aboA'e experiments, is far exceeded by that of some of the vapours of volatile liquids. A 
glass flask Avas provided with a brass cap furnished with an interior thread, by means of 
which a stopcock could be screwed air-tight on to the flask. Sulphuric ether being placed 
in the latter, the space aboA’e the liquid Avas completely freed of air by means of a second 
air-pump. The flask, with its closed stopcock, was now attached to the experimental 
tube ; the latter Avas exhausted and the needle brought to zero. The cock Avas then 
turned on so that the ether-vapour slowly entered the experimental tube. An assistant 
observed the gauge of the air-pump, and when it had sunk an inch, the stopcock Avas 
