1896 - 97 .] Electrical Properties of Fumes from Charcoal. 315 
from the plates passed between them and round them; and (3) to 
observe the leakage between two parallel metal plates with any 
difference of electric potential when the fumes from flames and 
burnings were allowed to pass between them. 
§ 3. To test the electrification of fumes from different flames 
and burnings, the arrangement shown diagrammatically in fig. 1 
was used. The flame is kept burning at the mouth of a large 
vertical iron funnel A, closed at its upper end ; and the heated air, 
along with the products of combustion, is drawn off by an air-pump 
through a small aperture, B, near the upper end. Before reaching 
the pump the air has to pass through three circular pieces of brass 
wire gauze, D, 1 centimetre apart, which are fixed across the 
funnel about 5 centimetres below the exit tube B ; and through a 
worm of block-tin pipe, 90 centimetres long, which is kept sur- 
rounded by cold water in a vessel C. The electrification was 
tested by a quadrant electrometer (sensitiveness of the electrometer 
111 scale divisions per volt), and an electric filter F. The filter F 
was of block-tin tube, 5 centimetres long and 1 centimetre bore, 
and full of fine brass filings kept in position by a plug of cotton 
wool and a piece of brass wire gauze at each end. Between the 
filter and the air-pump is a T-shaped piece of glass tubing with 
lower end of the vertical tube dipping into a basin of mercury. 
This served as a pressure gauge to indicate the difference of air 
pressures on the two sides of the filter when the air-pump was 
worked. The flame, the iron funnel, the worm, and the case of 
the electrometer are all metallically connected. 
§ 4. The following flames and burnings were tried : — 
(1) Candle. 
(2) Paraffin lamp. 
(3) Spirit flame. 
(4) Portable electrometer matches. 
(5) Coal-gas (Bunsen flame). 
(6) Hydrogen flame. 
(7) Glowing charcoal. 
(8) Glowing coal. 
§ 5. The method of experimenting was to place the burning 
substance in position at the bottom of the funnel, to insulate the 
