KADIATION OF HEAT BY GASEOUS AND LIQUID MATTEK. 
207 
was always kept filled with perfectly dry air, while either or both of the other chambers 
could be filled at pleasure with the gas or vapour to he examined. For the sake of 
convenience I will call the compartment of the tube nearest to the front chamber the 
first chamber, the compartment nearest to the pile the second chamber; the term 
‘ front chamber’ being, as before, restricted to that nearest to the source. The arrange- 
ment is sketched in outline in fig. 2. 
The entire length of the tube was 49-4 inches, and this was maintained throughout the 
whole of the experiments. The only change consisted in the shifting of the plate of salt 
S' which formed the partition between the first and second chambers. Commencing with 
a first chamber of 2*8 inches long, and a second chamber 46 - 4 inches long, the former was 
gradually augmented, and the latter equally diminished. The experiments were executed 
in the following manner : — The first and second chambers were thoroughly cleansed and 
exhausted, and the needle brought to zero by the equalization of the radiations falling 
upon the opposite faces of the pile. Into the first chamber the gas or vapour to be 
examined was introduced, and its absorption determined. The first chamber was then 
cleansed, and the gas or vapour was introduced into the second chamber, its absorption 
there being also determined. Finally, the absorption exerted by the two chambers 
acting together was determined, both of them being occupied by the gas or vapour. 
The combination here described enabled me to check the experiments, and also to trace 
the influence of the first chamber on the quality of the radiation. In it the heat was 
more or less sifted, and it entered the second chamber deprived of certain constituents 
which it possessed on its entrance into the first. On this account the quantity absorbed 
in the second chamber when the first chamber is full of gas, must always be less than it 
would be if the rays had entered without first traversing the gas of the first chamber. 
From this it follows that the sum of the absorptions of the two chambers, taken sepa- 
rately, must always exceed the absorption of the tube taken as a whole. This may be 
briefly and conveniently expressed by saying that the sum of the absorptions exceeds the 
absorption of the sum. 
Table VI. — Carbonic Oxide. 
Leng 
A 
th. 
Absorption per 100. 
vV 
r 
1st Chamber. 
2nd Chamber. 
r 
1st Chamber. 
v 
2nd Chamber. Both Chambers. 
2-8 
46-6 
6-8 
12-9 
12-9 
8-0 
41-4 
9-6 
12-2 
12*9 
12-2 
37-2 
10-7 
12-2 
12-9 
15*4 
34-0 
10-9 
12-2 
13*4 
17-8 
31-6 
111 
12-0 
13-3 
36-3 
13-1 
12-6 
10-3 
13-4 
mdccclxiv. 2 F 
