224 
PROFESSOR TYNDALL ON THE ABSORPTION AND 
column from 34 inches to 13-1 causes a fall in the case of nitrous oxide only from 23 0, 3 
to 17 0, 5, the same amount of shortening causes benzol vapour to fall from 34° to 15°*1 — 
a much greater diminution. So also as regards olefiant gas, a shortening of the radiating 
column from 34 inches to 13-1 inches causes a fall in the deflection only from 68° to 
65°; the same diminution produces with sulphuric ether a fall from 68° to 36°-5; and 
with acetic ether from 73° - 9 to 41°. In the long column acetic ether vapour beats 
olefiant gas, but in the short column the gas beats the vapour. 
One of the earliest series of experiments of this nature which were executed last 
autumn, though not free from irregularities, is nevertheless worth recording. The expe- 
riments were made with a brass tube, slightly tarnished within, the tube being 49-4 
inches long, and divided into two equal compartments, each 24*7 inches in length, by a 
partition of rock-salt placed at the centre of the tube. 
Table L.— 
-Dynamic radiation of Vapours. 
Deflection. 
A. 
r 
By 1st Chamber. 
2nd Cham, empty. 
By 1st Chamber. 
Vapour in 2nd Cham. 
By 2nd Chamber. 
Bisulphide of carbon 
. 8-2 
5-8 
21-2 
Benzol 
. 20-0 
12-4 
45-9 
Chloroform . . . 
. 24-3 
10-9 
55-2 
Iodide of ethyl . . 
. 27*5 
14-7 
55-3 
Alcohol .... 
. 42-7 
22*3 
69-0 
Sulphuric ether . 
. 46-3 
21-7 
80-5 
Formic ether . . . 
. 47-5 
19-8 
79-5 
Propionate of ethyl . 
. 49-8 
25-0 
82*3 
Acetic ether . . . 
. 53-3 
30*0 
82-1 
To ascertain whether the absorption by the vapours bears any significant relation to 
the absorption by the liquids from which these vapours were derived, the transmission of 
radiant heat through those liquids was examined. The open flame of an oil-lamp was 
used, and the liquids were enclosed in rock-salt cells. Thus the total radiation from 
the lamp, with the exception of the minute fraction absorbed by the rock-salt, was 
brought to bear upon the liquid. 
In the following Table the liquids are arranged in the order of their powers of 
transmission. 
