872 
PEOFESSOE W. A. MILLEE ON THE PHOTOGEAPHIC 
When the vapour of a volatile liquid was to be examined, a few drops of it were gene- 
rally allowed to fall into the tube filled with air, through which the vapour was allowed 
to diffuse itself at the ordinary temperature. The action of such vapours was therefore 
compared at a gi’eat disadvantage with that of the various gases, particularly where the 
volatility of the liquid was rather low. The results, however, even under these disad- 
vantageous circumstances, were well marked, as maybe seen by examining the subjoined 
Table of gases and vapours submitted to experiment, in which the comparative lengths 
of' the different spectra are shown in the second column of figures. 
Table III. — Absorbent action of Gases and Vapours on the Chemical Eays. 
Length of column of gas 2 feet. 
Name of gas. 
Termination 
of spectrum. 
Relative 
lengths of 
spectra. 
Atmo.spheric Air 
I70-5 
74-0 
Hydrogen 
170*5 
74-0 
Carbonic Acid 
170-5 
74-0 
Carbonic O.xide 
170*5 
74-0 
Olefiant Gas 
162-5 
66-0 
Mar-li-gas 
159-5 
63-0 
Coal-gas 
133-5 
37*0 
Proto.xide of Nitrogen 
159-5 
63*0 
Cyanogen 
1 59-5 
63-0 
Ammonia 
170-5 
74*0 
Sulphurous Acid 
110-5 
14-0 
Sulphuretted Hydrogen 
110-5 
14-0 
Bisulphide of Carbon 
101*5 
6*0 
Bichloride of Sulphur 
108 
10 
Benzol 
131-5 
35-0 
Oil of Turpentine 
152-0 
55-5 
Chloroform 
152-0 
55-5 
Ether 
163-5 
67-0 
Terchloride of Phosphorus 
131-5 
35 
O.Kychloride of Phosphorus 
141-5 
45 
Hydrochloric Acid 
151*5 
55-0 
; Hydrobromic Acid 
119-5 
23 
Hydriodic Acid 
111*5 
15 
j Peroxide of Nitrogen 
0 
0 
i Peroxide of Chlorine 
0 
0 
Remarks. 
Cut off abruptly. 
Cut off abruptly. j 
Cut off abruptly. | 
f A lew of the strongest lines between 140 and j 
I 152 are seen. 
Faint beyond Ill’S. 
Very feeble spectrum. 
Fades out very gradually. 
Cut off abruptly. 
Cut off abruptly. 
18. The absorbent action disclosed by the foregoing experiments on the colourless 
gases and vapours is very interesting, as it proves that differences exist in the diactinic 
power of these substances quite as marked as in the case of liquids and solids. Some of 
the elementary gases, oxygen, hydrogen, and nitrogen, appear to possess a diactinic capa- 
city greater than any solid or liquid body. Many com'pound gases, such as ammonia, 
carbonic acid, and carbonic oxide, appear to rival them. Olefiant gas, cyanogen, and 
hydrochloric acid exhibit a decided but not great absorptive power, with which that of 
the vapours of ether, chloroform, and oil of turpentine at the atmospheric tension, and 
when diffused through air, may be compared. Doubtless if these vapours were tried at 
a tension of 30 inches, they would exhibit greater absorptive power. The absorptive 
