320 Proceedings of Royal Society of Edinburgh. [sess. 
Sensitiveness of the Electrometer 136 scale divisions jper volt. 
Flame. 
Distance 
of top of 
Flame 
below the 
Plates in 
Centi- 
metres. 
Metal 
connected 
to Insul- 
ated Ter- 
minal of 
Electro- 
meter. 
Difference 
between 
Fumes 
Zero and 
Metallic 
Zero in 
Scale 
Divisions. 
Potential 
in Volts. 
Spirit lamp 
23 
Copper 
81 pos. 
0-60 
>5 ... 
5 5 
Zinc 
101 neg. 
074 
5 5 • 
11 
Copper 
53 pos. 
0-39 
5 5 • » • 
Paraffin lamp without glass 
yy 
Zinc 
76 neg. 
0-56 
funnel .... 
7 
Copper 
141 pos. 
D04 
55 .... 
5 5 
Zinc 
138 neg. 
1*01 
y 5 • • • 
15 
Copper 
90 pos. 
0-66 
55 .... 
5 5 
Zinc 
103 neg. 
0-76 
55 .... 
23 
Copper 
108 pos. 
0-79 
5 5 
5 y 
Zinc 
112 neg. 
0-82 
yy • 
30 
Copper 
83 pos. 
0*61 
yy .... 
yy 
Zinc 
83 neg. 
0-61 
§ 11. To observe the leakage between two parallel metal plates, 
the zinc plate was removed, and a polished copper plate, equal and 
similar to the other copper plate, was substituted for it. The 
distance between their parallel planes was 0’9 cm. The experi- 
ments were conducted as follows : One pair of quadrants of the 
electrometer, with one of the copper plates in metallic connection 
with it, was insulated. There was now no deviation from metallic 
zero. A small charge, positive or negative, was given to it, pro- 
ducing a deflection of about 450 scale divisions. This corresponds 
to over 9 volts, as the sensitiveness of the electrometer now used 
was 48 *2 scale divisions per volt. In two or three minutes the 
ordinary leakage of the arrangement was observed. This did not 
amount to more than one division, or at most two divisions, per 
minute. Then the flame was lit, and readings were taken every 
half-minute. This was done with the variations in the funnel 
described in the last column of the following table, and illustrated 
by fig. 3. Tor comparison, the numbers in the following table 
show the leakage for two minutes after the reading was 300 scale 
divisions (6 - 2 volts) from metallic zero. This gives us the leakage 
