ELECTRIFICATION OF AIR, VAPOUR OF WATER, AND OTHER GASES. 201 



NON-ELECTRIFIED Am PASSED OVER HOT COPPER AND HOT CHARCOAL ( 40). 



40. Passing air through the apparatus without first electrifying it, but keeping 

 the glass tube at a high temperature, we found no deflection on the electrometer. 

 But on repeating this experiment with copper foil in the tube an electrification of 

 9 volts positive for 200 strokes was observed. Replacing the copper foil by charcoal, 

 with temperature high enough to keep the charcoal visibly burning, we found a 

 negative electrification of 7 volts for 1 60 strokes. 



u 



Fig. G. 





1 



J 







SD 



ELECTRIFICATION PRODUCED BY SHAKING AIR AND OTHER GASES WITH WATER 

 AND WITH SOLUTIONS OF DIFFERENT SUBSTANCES ( 41-46). 



41. An ordinary Winchester glass bottle, A, fig. 6, of capacity 2500 cub. centims., 

 has two broad strips of tin foil cemented on its outer surface on opposite sides, from 

 VOL. cxci. A. 2 D 



