RADIATION OF HEAT BY OASES AND VAPOURS. 
11 
Table I. — Olefiant Gas. 
Tensions in inches. 
Deflection. 
Absorption. 
1 
0 
56 
90 
2 
58-2 
123 
3 
59-3 
142 
4 
60-0 
157 
5 
60-5 
168 
6 
61-0 
177 
7 
61-4 
182 
8 
61-7 
186 
9 
62-0 
190 
10 
62-2 
192 
20 
66-0 
227 
No definite relation between the density of the gas and its absorption is here exhi- 
bited. We see that an augmentation of the density seven times about doubles the 
amount of the absorption ; while gas of 20 inches tension effects only 2-| times the 
absorption of gas possessing 1 inch of tension. 
But here the following reflections suggest themselves : it is evident that olefiant gas 
of 1 inch tension, producing so large a deflection as 56°, must extinguish a large propor- 
tion of the rays which are capable of being absorbed by the gas, and hence the succeed- 
ing measures having a less and less amount of heat to act upon must produce a continu- 
ally smaller effect. But supposing the quantity of gas first introduced to be so incon- 
siderable that the number of rays extinguished by it is a vanishing quantity compared 
with the total number capable of absorption, we might reasonably expect that in this 
case a double quantity of gas would produce a double effect, a treble quantity a treble 
effect, or in general terms, that the absorption would, for a time, be proportional to the 
density. 
To test this idea, a portion of the apparatus, which was purposely omitted in the 
description already given, was made use of: 0 0, Plate I., is a graduated glass tube, the 
end of which dips into the basin of water B. The tube can be stopped above by means 
of the stopcock r ; d d is a tube containing fragments of chloride of calcium. The tube 
0 0 being first filled with water to the cock r, had this water displaced by olefiant gas ; 
and afterwards the tube S S', and the entire space between the cock r and the experi- 
mental tube, was exhausted. The cock n being now closed and r' left open, the cock r 
at the top of the tube O O was carefully turned on and the gas permitted to enter the 
tube S S' with extreme slowness. The wnter rose in O O, each of whose smallest divi- 
sions represents a volume of sijth of a cubic inch. Successive measures of this capacity 
were admitted into the tube and the absorption in each case determined. 
In the following Table the first column contains the quantity of gas admitted into the 
tube ; the second contains the corresponding deflection, which, within the limits of the 
c2 
