398 PEOrESSOE BU]S^SE2f AXD DE. H. E. EOSCOE’S PHOTO-CHIDnCAIi EESEAECHES. 
these gases (or one of them), similar to ozonized and common oxygen, can, under certain 
circumstances, be in an active, and under others, in a passive condition *. If this hypo- 
thesis be true, each gas must undergo this peculiar modification vrhen separately exposed 
to the action of light. The following experiments show, however, that this is not the 
case. 
The gases, prepared as usual by electrolysis, were evolved in the dark from two sepa- 
rate porous cells, and each gas allowed to pass through a thin glass tube 3 feet lorrg, 
which was so berrt that its whole length could be placed outside the window-shutter, 
whilst the two ends were retained in the darkened room. The two gases passed 
separately through this bent tube into the dayhght, and then both traversed a commu- 
rricating tube which led them into the instrument. By means of these tubes we were 
able to expose each one of the separated gases to the direct or difiuse sunlight, and to 
examine the effect produced on the serrsibility of the resulting mixture. To begin with, 
the tubes reaching beyond the shutter were carefully protected from the action of lighL 
and the mixture led through the apparatus until the gas had attained the sensibility requi- 
site for the observations. The increase of the induction was then determined in two suc- 
cessive experiments, in the first of which the separate gases were kept in the dark, and 
in the second of which they were previously insolated. In the first of the following 
experiments diffuse daylight was used for the insolation of the separated gases, and in 
the second direct sunlight. Division I. contains the times of observation, Dfrision II. the 
action for each minute corresponding to these times, a for the non-insolated gas, and b 
for the gas which had been exposed to light immediately before. 
Series of Experiments XII. 
1. Experiment with diffuse 
daylight. 
2. Experiment with direct 
sunlight. 
ii. 
II. 
I. 
I. 
a. 
b. 
a. 
b. 
1 
5-5 
8‘5 
1 
0-5 
0-3 
2 
6’0 
8-5 
2 
13-5 
0-3 
3 
6'5 
9-0 
3 
18-0 
190 
4 
11-5 
10-0 
4 
16-0 
33 0 
5 
32-0 
12-0 
5 
29-0 
340 
6 
73-0 
27-0 
6 
38-0 
30-0 
7 
73-0 
7 
53-0 
Although the intensity of the light to which the gases were separately exposed was 
so great that, had the gases been mixed, their combinmg power would have been 
increased to such an extent that explosive combmation would immediately have occurred, 
still the experiment showed no greater difference between the dui’ation of the induction 
of the insolated and non-insolated gas than the errors of obseiTation rendered unavoid- 
able. The experiments, therefore, show that the light does not effect a permanent modi- 
fication, either of the chlorine or of the hydrogen, but that the combination produced by 
* See Dkapee, Pliilosophical Magazine, 1857, vol. xiv. page 161, 
