ELECTRIFICATION OF ATR, VAPOUR OF WATER/AND OTHER GASES. 223 



insulated standard filter connected with the electrometer ; but, again, no evidence of 

 electrification on the filter could be detected on the electrometer. It thus appears as 

 if the porous ball itself had withdrawn the electric charge from the gas which passed 

 through the ball. 



COMMUNICATION OF ELECTRICITY FROM ELECTRIFIED STEAM TO AIR ( 77-81). 



77. Steam was generated in a kettle, A, and electrified by brush discharge from a 

 needle point, B, attached to the lower end of a long copper rod, CB. The rod was 

 kept central and insulated in the brass tube, D, by two rubber corks. The upper 

 end of the rod was connected to the insulated terminal of a voltmeter, E, and of a 

 Voss electric machine, F (fig. 12). 



78. To preserve the insulating properties of the corks during the experiments it 

 was found necessary to keep a current of air passing in the tube between the corks, 

 and to surround the lower part of the tube with a jacket of oil kept at a temperature 

 of 235 F. 



79. The electrified steam from the kettle passed up into a vertical tube, G, where 

 it mixed with air drawn, by an air-pump shown on the right-hand side of the 

 drawing 1 , from a bottle into which the lower end of the tube was fitted. Air to take 



cV 



the place of that drawn from the bottle entered by a long pipe from outside a window 

 of the laboratory. The mixed steam and air passed from G into a LIEBIG'S condenser, 

 H, where the steam was condensed. The water thus formed dropped into a WOULFF'S 

 bottle, and the air was drawn from another neck of the bottle through a drying tube, 

 K, containing sulphuric pumice. From this it passed direct through an electric 

 filter, L, insulated by two paraffin tunnels, and thence to the air-pump. The filter was 

 connected to the insulated terminal of a quadrant electrometer, whose constant was 

 117 divisions per volt. 



80. When the air-pump and the electric machine were worked, with the kettle 

 cold, the electrometer showed no electrification. It also showed no electrification 

 when the kettle was boiling and the air-pump worked, but the electric machine 

 stopped. 



81. When the kettle was kept boiling, and the electric machine and air-pump 

 both worked, strong electrification, positive or negative, according as the machine was 

 positive or negative, was observed, 52 divisions per minute being our largest value. 

 This, with the known capacity of the electrometer, corresponds to O'll C.G.S. 

 electrostatic unit taken per minute from the air by the filter. 



ELECTRIFICATION OF AIR AT DIFFERENT AIR-PRESSURES AND AT DIFFERENT 

 ELECTRIC POTENTIALS. MEASUREMENT OF CURRENT ( 82-88). 



82. In February, March, and April, 1896, we made experiments on the electri- 

 fication of air at different air-pressures, using for this purpose the apparatus repre- 



