54 Additional Notes. 



Glass is believed to consist in part of consolidated resinous ether, 

 and thence to attract an electric atmosphere round it, which consists 

 of a greater proportion of vitreous ether compared to the quantity of 

 the resinous, as mentioned in Proposition No. 4. This atmosphere 

 may stand off a line from the surface of the glass, though its attrac- 

 tive or repulsive power may extend to a much greater distance; and 

 a more equally mixed electric atmosphere may stand off about the 

 same distance from the surface of a cushion. 



Now when a cushion is forcibly pressed upon the surface of a glass 

 cylinder or plane, the atmosphere of the cushion is forced within 

 that of the glass, and consequently the vitreous part of it is brought 

 within the sphere of the attraction of the resinous ether combined 

 with the glass, and therefore becomes attracted by it in addition to 

 the vitreous part of the spontaneous atmosphere of the glass; and the 

 resinous part of the atmosphere of the cushion is at the same time 

 repelled by its vicinity to the combined resinous ether of the glass. 

 From both which circumstances a vitreous ether alone surrounds the 

 part of the glass on Avhich the cushion is forcibly pressed ; which does 

 not, nevertheless, resemble an electrised coated jar; as this accumula- 

 tion of vitreous ether on one side of the glass is not so violently con- 

 densed, or so forcibly attracted to the glass by the loose resinous ether 

 on the otlftr side of it, as occurs in the charged coated jar. 



Hence as weak differences of the kinds or quantities of electricity 

 <lo not very rapidly change place, if the cushion be suddenly with- 

 drawn, with or without friction, I suppose an accumulation of vitreous 

 electric ether will be left on the surface of the glass, which \?\\\ diffuse 

 itself on an insulated conductor by the assistance of points, or will 

 gradually be dissipated in the air, probably like odours by the repul- 

 sion of its own particles, or may be conducted away by the surround- 

 ing air as it is repelled from it, or by the moisture or other impurities 

 of the atmosphere. And hence I do not suppose the friction of the 

 glass-globe to be necessary, except for the purpose of more easily re- 

 moving the parts of the surface from the pressure of the cushion to 

 the points of the prime conductor, and to bring them more easily into 

 reciprocal contact. 



