EADIATION OF HEAT BY OASES AKD VAPOUES. 
25 
The order of absorption is here shown to be the same in both tubes, and the quantity 
absorbed in the bright tube is, in general, about 4^ times that absorbed in the black one. 
In the third column, indeed, I have placed the products of the numbers contained in the 
first column by 4'5. These results completely dissipate the suspicion that the effects 
observed with the bright tube could be due to a change of the reflecting power of its 
inner surface by the contact of the vapours. 
With the blackened tube the order of absorption of the following substances, com- 
mencing with the lowest, stood thus : — 
Alcohol, 
Sulphuric ether. 
Formic ether. 
Propionate of ethyl ; 
whereas with the bright tube they stood thus : — 
Formic ether. 
Alcohol, 
Propionate of ethyl. 
Sulphuric ether. 
As already stated, these differences would in all probability disappear, or be accounted 
for on re-examination. Indeed veiy slight differences in the purity of the specimens 
used, would be more than sufficient to produce the observed differences of absorption*. 
§ 7. Action of 'permanent Gases on Badiant Heat. 
The deportment of oxygen, nitrogen, hydrogen, atmospheric air, and olefiant gas 
has been already recorded. Besides these I have examined carbonic oxide, carbonic 
acid, sulphuretted hydrogen, and nitrous oxide. The action of these gases is so much 
feebler than that of any of the vapours referred to in the last section, that in examining 
the relationship between absorption and density the measures used with the vapours 
were abandoned, and the quantities of gas admitted were measured by the depression of 
the mercurial gauge. 
Table XIX. — Carbonic Oxide. 
Absorption. 
Tension in inches. 
Observed. 
Calculated. 
0-5 
2-5 
2-5 
1-0 
5-6 
5-0 
1-5 
8-0 
7-5 
2-0 
10-0 
10-0 
2-5 
12-0 
12-5 
3-0 
15-0 
15-0 
3-5 
17-5 
17-5 
• In illustration of this I may state, that of two specimens of methylic alcohol with which I was furnished 
by two of my chemical friends, one gave an absorption of 84 and the other of 203. The former specimen 
MDCCCLXI. E 
