1896-97.] Conductive Effect in Air toy Rdntgen Bays. 
411 
electrometer readings after the two pairs of quadrants were 
insulated and the ultra-violet light shining (which we shall here- 
after refer to as the ultra-violet-light-zero ) was observed. 
The insulated metal was afterwards charged positively, and then 
negatively. The rate of discharge was observed until the ultra- 
violet-light-zero was reached. 
With polished zinc as the insulated metal the following results 
were obtained. 
The insulation was first tested. When no ultra-violet light was 
used it was found that the electrometer reading remained the same 
whether the two pairs of quadrants were in metallic connection or 
not. With the ultra-violet light shining the reading with the 
quadrants in metallic connection was the same as before, the read- 
ings with the quadrants disconnected were : — 
January 14. 
3h. 41m. p.m. 
- 25 sc. divs. from metallic zero after 15 secs. 
- 45 
- 59 
- 67 
3 3 
3 3 
5 3 
3 3 
3 3 
3 3 
3 ? 
3 3 
30 „ 
45 „ 
1 min, 
- 80 
- 89 
- 99 
-101 
33 33 33 
33 33 33 
33 33 33 
33 33 33 
n „ 
2 „ 
3 „ 
Afterwards steady. 
[Sensibility of electrometer, 140 sc. divs. per volt.] 
The difference thus found, between the metallic zero and the 
ultra-violet-light-zero, is-101or-0*72ofa volt. 
3h. 47m. Zinc charged positively to 219 scale divisions from the metallic 
zero. 
Reading from metallic zero with ultra-violet light shining : — 
Time. 
+ 124 
* 
after 15 secs. 
+ 64 
• 
3 3 
30 „ 
+ 23 
3 3 
45 „ 
- 13 
3 3 
1 min. 
- 55 
3 3 
n „ 
- 79 
3 3 
2 „ 
- 93 
3 3 
24 „ 
-100 
3 3 
34 „ 
-103 
3 3 
4 „ 
Afterwards steady. 
