858 PEOEESSOE TYNDALL’S CONTEIBUTIONS TO MOLECULAE PHYSICS. 
Here, however, 1 we had carbonic acid mixed with the sulphurous acid of the flame. 
Of the heat radiated by this composite source, the absorption by an atmosphere of 
sulphurous acid amounted to 
60 per cent. 
The gas was sent from its generating retort through drying-tubes of sulphuric acid into 
a glass experimental tube 2-8 feet long. The comparative shortness of the tube, and 
the mixed character of the radiation, rendered the absorption less than it would have 
been had a source of pure sulphurous acid and a tube as long as that used in the other 
experiments been employed. 
I subsequently caused' the radiation from the carbonic-oxide flame to pass through a 
few of our vapours, with the following results : — 
Table XXXY. 
Eadiation through Vapours (tension 05 inch). Source, carbonic-oxide flame. 
Name of vapour. 
Deflection. 
Absorption. 
Bisulphide of Carbon . . 
. 5*5 
9-8 
Chloroform 
. 6-0 
10-7 
Formic Ether 
. 14-5 
25-8 
Sulphuric Ether .... 
. 18-0 
32T 
Total heat 
. 43-0 
100-0 
The same vapours were employed to test the radiation from the hydrogen-flame, 
the following results : — 
Table XXXVI. 
Eadiation through Vapours (tension 0‘5 inch). 
Source, hydrogen-flame. 
Name of vapour. 
Deflection. 
Absorption. 
Bisulphide of Carbon . . 
. 8-8 
11-9 
Chloroform * . 
. 9-9 
13-4 
Sulphuric Ether .... 
. 32-0 
42-2 
Formic Ether 
. 35-0 
49-3 
Total heat 
. 48-5 
100-0 
We here find that, in the case of every one of the four vapours, the synchronism 
with hot aqueous vapour is greater than with hot carbonic acid. The temperature of 
the hydrogen-flame is higher than that of the carbonic oxide ; but the radiation from the 
more intense source is most copiously absorbed. It has been already proved that, for 
waves of slow period, formic ether is more absorbent than sulphuric ether ; while for 
waves of rapid period, the sulphuric ether is the more powerful absorber. For the 
radiation from hot carbonic acid, the absorption of sulphuric ether, as shown in Table 
XXXV., is between 6 and 7 per cent, in excess of that of formic ether ; while for the 
radiation from hot aqueous vapour, the absorption by formic ether, as shown in Table 
XXXVI., is 7 per cent, in excess of that by sulphuric. That the periods of aqueous 
