340 PROFESSOR TYNDALL’S CONTRIBUTIONS TO MOLECULAR PHYSICS, 
Table XI. — Radiation of heat through Vapours. 
Mass of vapour proportional to 
mass of liquid. 
Tension in parts 
Name of vapour. 
of an inch. 
Deflection. Absorption per 100. 
Bisulphide of Carbon . . 
. 0*48 
I 8 * 4 ) . 
\ 8-5 J 
4-3 
Chloroform 
. 0-36 
P'°) 
6-6 
113-0 J 
Iodide of Methyl . . . 
. 0*46 
{20-0 j 
120-4 J 
10-2 
Iodide of Ethyl .... 
. 0-36 
f 30*6 1 
130-6 J 
15-4 
Benzol ....... 
. 0-32 
if 4 } 
16-8 
133-1 J 
Amylene ...... 
. 0/26 
37-7 
19-0 
Sulphuric Ether . . . 
. 0-28 
f 42-5 1 
21-5 
142-6 J 
Acetic Ether 
. 0-29 
144-0 1 
22-2 
144-0 J 
Formic Ether .... 
. 0-36 
J 44-5 1 
22-5 
144-7 J 
Alcohol 
. 0-50 
{45-01 
22-7 
144-9 J 
Here the discrepancies revealed by 
our former series 
of experiments entirely disappear, 
and it is proved that for heat of the same quality the order of absorption for liquids and 
their vapours is the same. We may therefore safely infer that the position of a vapour 
as an absorber or radiator is determined by that of the liquid from which it is derived. 
Granting the validity of this inference, the position of water fixes 
that of aqueous 
vapour. From the first seven Tables of this memoir, 
, or from the resume of results in 
Table VIII., it will be seen that for all thicknesses water exceeds the other liquids in 
the energy of its absorption. Hence, if no single experiment on the vapour of water 
existed, we should be compelled to conclude, from the deportment of its liquid, that, 
weight for weight, aqueous vapour transcends all others in absorptive power. Add to 
this the direct and multiplied experiments by which the action of this substance on 
radiant heat has been established, and we have before us a body of evidence sufficient, 
I trust, to set this question for ever at rest, and to induce the meteorologist to apply 
without misgiving the radiant and absorbent property of aqueous vapour to the pheno- 
mena of his science. 
§ 5 . 
The order and relative powers of absorption of our vapours, when equal volumes are 
compared, are given in Table X. : the chemical formulae of the substances, and the 
number of atoms which their molecules embrace, are as follows :■ — 
