45 
1897-98.] Leakage from Electrified Metal Plates. 
the insulation of the electrometer is made practically perfect by 
coating its vulcanite insulators with paraffin) the following numbers 
were obtained : — 
I. Glass Plate 18 eras, by 19 eras, by 0’3 cm. 
Distance of 
Time of fall from 
flame above 
3000 to 2000 
Remarks. 
point 
volts 
Cms. 
Min. Sec. 
— 
5 30 
Insulation test, with no flame. 
12 
2 5 
Flame lit : no intervening plate. 
3 3 
4 7 
,, ,, glass plate between. 
II. Mica Sheet 18 eras, by 9 cms. by 0*1 cm. 
6 46 
Insulation test, with no flame. 
12 
1 56 
Flame lit : no intervening plate. 
3 3 
3 50 
,, ,, mica sheet between. 
III. 
Paraffin Plate 11 cms. by 11 cms. and 075 cm. thick. 
6 40 
No flame. Insulation test. 
12 
1 53 
Flame lit : no intervening plate. 
3 3 
2 20 
,, ,, paraffin plate between. 
We hope to return to the investigation with the insulation of 
the electrometer perfected ; and to determine by special experi- 
ment, how much of the fall of potential in the electrometer in each 
case is due to the electricity of opposite kind induced on the upper- 
most surface of the non-conducting plate, and how much, if any, is 
due to leakage through the air to the metal disc or point below. 
§ 9. To test the quality of the electrification of both sides of the 
non-conducting plates of glass and paraffin, a thin copper sheet, C, 
was fixed to one of the terminals of a quadrant electrometer, as 
represented in fig. 4, where A is the plan of the plate C, and B 
is the plate of paraffin or glass under test. 
In the primary experiment (fig. 3) the non-conducting plate was 
fixed in a horizontal position one centimetre above the electrified 
metal (point or disc), and eleven centimetres below the flame. A 
charge was given to the metal, to raise its potential to about 3500 
