254 PROCEEDINGS OF SECTION A. 
the light was applied. In these cases no change of deflection 
was ever noticed. 
The voltage used was varied from that given by one Clark cell to 
that of forty cells, acccording to the conductivity. The deflections 
varied from 30 to over 150 mm., and as a variation of a couple of 
divisions could be certainly measured, the experiments show that, 
with sulphur in the form in which we have used it, light cannot 
aftect the conductivity to the extent of more than 1 per cent. 
SECTION III.—CONDUCTION IN SULPHUR OF HIGH INSOLUBILITY. 
As has been already stated in experimenting upon the effect of 
light upon the conductivity of sulphur, all the ordinary phenomena 
of sulphur conduction were obtained, some of them in an appar- 
ently exaggerated form. As considerable insolubility was obtained 
in these experiments, the method used appeared well adapted for 
extending the qualitative results obtained for the electric conduc- 
tivity of sulphur of large solubility to sulphur of much less 
solubility. 
The form of sulphur conductor was, of course, made in the first 
instance with a view to obtain as much conductivity as possible 
in a sulphur cell that could be exposed to light without difficulty. 
Various methods of winding platinum upon mica, &e., and covering 
with sulphur were tried, in imitation of the cells made by Adams, 
Bidwell, and others in the study of selenium. These cells were 
finally rejected in favour of cells made in the way already described, 
which were used throughout in the experiments with light. 
On account of the possibility of contamination, however, the 
results given by the cells made in the fashion described cannot be 
relied upon as accurate. The general character of the phenomena 
observed may, however, be given. 
The different cells made differed widely in conductivity, with 
some of them a single cell was sufticient to send the light spot the 
whole length of the scale, while with others the whole battery of 
forty cells was used, and the deflection then obtained was small. 
The following facts appeared to be true of all the cells :— 
1. The deflection which was obtained when the current was 
first passed gradually diminished all the time the current 
was running. 
2. After this decrease of conductivity, if the direction of the 
current through the sulphur was reversed, the deflection 
was increased considerably. 
3. When the number of cells in the battery was increased 
the conductivity increased, some minutes elapsing gener- 
ally before the maximum current was obtained. The 
deflection then began to decrease again as usual. 
