GASES BY THE ACTION OF EONTGEN BAYS AND OTHER AGENTS. 
435 
the small indiarubber stopper closing the upright tube at the top of the ap]3aratuS; 
The lower surface of the zinc was freshly polished, and the upper surface was covered 
with wet filter paper, to diminish as far as possible the production of cloud nuclei l^y 
the zinc. The thickness of the layer of air could 1)e increased or diminished by 
ruimiug water out, or drawing water in, through the tube pointing downwards on the 
left. Any desired difference of potential could be maintained between the zinc and 
the water by means of a battery of small secondary cells. 
The actual experimental numbers are given in the tables which follow. 
Polished Zinc PlcUe in Air. 
Ultra-violet light from zinc-spark 30 centims. below the cpiartz plate. Depth of 
water over the quartz = 2'8 centims. Thickness of air-layer — 0‘8 centim. 
Gauge reading 
(in millims.) = -p. 
\ 
E.M.E., in volts. 
Result of 
expansion. 
Zinc positive. 
Zinc negative. 
151 
9 
0 
0 
159 
9 
0 
Slight fog 
167 
9 
0 
Fog 
! 173 
9 
0 
Fog 
1 181 
9 
Slight fog 
Dense fog 
161 
32 
0 
Fog 
! 157 
32 
0 
Fog 
177 
40 
0 
Fog 
; 177 
80 
0 
Fog 
1 177 
240 
0 
Fog 
153 
240 
0 
0 
■ 153 
80 
0 
0 
1 183 
240 
Fog 
Fog 
No difference could be observed between the results without any E.M.F., and those 
obtained with the same expansion when the zinc was positive. 
Zinc plate freshly polished ; zinc-sjiark 54 centims. below the quartz ; depth of water 
over quartz = 2'3 centims. ; thickness of air layer —- 1'6 centims. ; barometer 
= 766 ; temperature = 15*^ C., tt — 13 millims. 
Gauge reading 
(in millims.) = p. 
E.M.F. in 
volts. 
Result of expansion. 
Zinc uncharged. 
Zinc positive. 
Zinc negative. 
163 
240 
Shower 
Shower 
Fog 
153 
240 
Very few drops 
Very few drops 
Very dense shower 
151 
80 
Very few drops 
Very few drops 
Distinct shower 
149 
80 
Very few drops 
Very few drops 
Very few droj^s 
149 
120 
Very few drops 
Very few drops 
Very few drops 
139 
120 
Very few drops 
Very few drops 
Very few drops 
3 K 2 
