334 
PROFESSOR W. G. ADAMS AND MR. R. E. DAY ON THE 
In all these experiments we found that on closing the box the deflection was almost 
instantly reduced to zero. 
On another occasion, when the electrodes of the same piece were connected with the 
galvanometer, exposure to the light of burning magnesium ribbon produced a deflection 
of 90 divisions. The needle came back to zero as the light died away. 
Tube No. 11 was then put in circuit with the galvanometer, and a gas-burner was 
placed at different distances from it. The selenium was then exposed, the deflection 
when steady of the galvanometer-needle noted, and then the light was screened off, when 
in all cases the deflection came back at once to zero. The results were as follows : — 
Distance of burner. Deflection. 
9 inches 1 
3 „ 6 
li „ 14 
These deflections were in the same direction whichever side or end of the selenium 
was exposed to the light. 
On another occasion, with the same tube, exposure to the gas-flame at 8 inches 
distance produced a current of 4, while exposure to the light of burning magnesium 
ribbon at the same distance produced a current of 27. 
No. 15 was then tried in the same manner with the light from a gas-burner placed 
at different distances. 
Distance of light. 
18 inches 
13 
7 „ 
3 „ 
The light from the burner was very variable, so that in the case of the higher deflec- 
tions the needle oscillated a good deal. The above values were the mean deflections. 
On another occasion, when No. 15 had its electrodes connected immediately with the 
galvanometer, exposure to the light of the gas-flame at a distance of 8 inches produced 
a deflection of 90 divisions, while exposure to the light of burning magnesium ribbon 
at the same distance produced a deflection of 85 with the 10th shunt in the galvano- 
meter in the same direction as before. On again exposing to the gas-flame at the same 
distance, the deflection was equal to 72 divisions in the same direction. In each case 
the deflection came back at once to zero on screening off the light. 
Action of Light on Selenium through which no Electric Current has passed. 
All the pieces of selenium hitherto used had repeatedly been subjected to the action 
of currents passing through them, and it therefore seemed desirable to examine the 
effects of exposure on pieces through which no electrical current had previously been sent. 
Deflection. 
11 
20 
64 
225 
