RADIANT HEAT, AND ITS CONVERSION THEREBY INTO SOUND. 313 
Table II. 
Polished tube. 
Blackened tube. 
r 
Spiral 
Spiral 
Spiral 
(dull). 
(bright). 
(dull). 
Bisulphide of Carbon . 
. 3-0 
2-4 
3-0 
Chloroform. 
. 7-0 
4-6 
5-0 
Benzol. 
. 9-4 
7-5 
10-0 
Iodide of Ethyl . . . . . 
. 13-6 
8-6 
12-3 
Iodide of Methyl..... 
. 15-6 
10-7 
13-8 
Amylene. 
. 20*6 
14-3 
17-5 
Sulphuric Ether. 
. 27'0 
21‘0 
23-8 
Acetic Ether. 
. 33-0 
23-0 
29-0 
Formic Ether. 
. 38-0 
23-0 
30-0 
The vapour pressures here are the same as those employed in Table I. The order 
of absorption is the same in both tables ; but its amount is diminished. This was to 
be expected from the difference in quality of the heat. We are dealing with trans¬ 
parent vapours—in other words, vapours pervious to the luminous rays ; and the 
greater the proportion of these rays in the calorific beam, the less will be the absorp¬ 
tion. This is well illustrated by the second column in the table, which shows the fall 
of the absorption when the spiral is raised from a dull red to almost a white heat. 
The polished tube was used in both these cases. 
The third column of figures in Table II. shows the results obtained when the 
experimental tube was coated within with lampblack. The absorptions are in the 
same order, and almost of the same amount as those of the first column. The case is 
representative and might be multiplied to any extent. It is incompatible with the 
notion that my results were due to films collected on the polished interior surface of 
my experimental tube. 
Placing the substances recently experimented on in the order of their absorption, 
and also in the order which they exhibited in 1864, we have the following two 
columns:— 
1880. 
Bisulphide of Carbon 
Chloroform 
Benzol 
Iodide of Ethyl 
Iodide of Methyl 
Amylene 
Sulphuric Ether 
Acetic Ether 
Formic Ether 
1864. 
Bisulphide of Carbon 
Chloroform 
Iodide of Methyl 
Iodide of Ethyl 
Benzol 
Amylene 
Sulphuric Ether 
Acetic Ether 
Formic Ether 
In 1864, therefore, the iodide of methyl proved itself more diathermanous than the 
mdccclxxxii. 2 s 
