336 PROFESSOR TYNDALL’S CONTRIBUTIONS TO MOLECULAR PHYSICS. 
off and the permanent deflection of the needle noted. Knowing the total heat, the 
absorption in lOOths of the entire radiation could be at once deduced from the deflec- 
tion. The following Table contains the results of the first series of experiments made 
with the platinum spiral as source. 
Table IX. — Kadiation of heat through Vapours. Source, red-hot platinum spiral 
Tension, 0*5 of an inch. 
Name of vapour. 
Deflection. 
Absorption per ] 
Bisulphide of Carbon . . 
. 17-0 
4-7] 
v Mean. 
[4-7 
Bisulphide of Carbon . . 
. 16-8 
4-6J 
Chloroform 
. 22-5 
6*2| 
J- 6-3 
Chloroform 
. 22-8 
6-3J 
Iodide of Methyl .... 
. 34*0 
9-7'j 
[ 9-7 
Iodide of Methyl .... 
. 34-0 
9-7J 
Iodide of Ethyl .... 
. 46-0 
18*0] 
tl7*8 
Iodide of Ethyl .... 
. 45-5 
17-6J 
Benzol . 
. 48-5 
20-4] 
j-20-4 
Benzol ....... 
. 48-5 
20-4J 
Amylene 
. 56-3 
27*3] 
j>27*3 
Amylene ...... 
. 56-2 
27-2J 
Total heat 
. 78-3 
100-0 
The absence of all caprice or uncertainty in the measurements is, I think, demon- 
strated by the foregoing Table, which is simply an average sample of the degree of coin- 
cidence obtained in separate measurements. Two determinations were made in each 
case ; and it will be seen that while, in some instances, the second experiment yielded 
the same result as the first, in one instance only does the difference amount to half a 
degree of the galvanometer. 
The foregoing measurements were executed on the 5th of October. On the 7th they 
were in part repeated, with the following results. 
Table X. 
Name of vapour. 
Deflection. 
Absorption. 
Bisulphide of Carbon . 
. . 16° 5 
4-7 
Chloroform .... 
. . 22-8 
6-5 
Iodide of Methyl . . . 
. . 33-0 
9-6 
Iodide of Ethyl . . . 
. . 45-0 
17-7 
Benzol 
. . 48-0 
20-6 
Amylene 
. . 55-3 
27-5 
Alcohol 
. . 55-7 
28-1 
Formic Ether .... 
. . 58-2 
31-4 
Sulphuric Ether . . . 
. . 58-5 
31-9 
Acetic Ether .... 
. . 59-9 
34-6 
Total heat 
. . 78-0 
100-0 
