in Electricity. 667 
As the quantity of electricity excited upon glafs is 
nearly in the proportion of the furface expofed to fric- 
tion ; and as glaffes of a great fize are very precious, and 
liable to accidents, I conceived, that inftead of a disk of 
flat glafs one might fubftitute one of pafte-board, 
thoroughly imbibed with copal or amber varnifli. 
To try how this would anfwer, about feven years ago 
I ordered three pafte-board disks to be made, of four 
feet in diameter, the diftance of fix inches from the cen- 
ter being the fitted: to give the whole a proper fupport in 
whirling it round. When thefe disks were thoroughly 
dried and heated, I poured upon them a varnifli made of 
amber diflolved in linfeed oil. After they had taken in as 
much of the varnifli as they could imbibe, I covered 
them with a thick coat of the fame varnifli,. and dried 
them by the heat of a German ftove. 
When the varnifli was very hard, I found, that even 
a flight friction with a cat’s skin or hare’s skin excited a 
ftrong electricity upon them. 
I then made a frame to place them in, and to whirl 
them round; which frame was fo contrived, that it could 
contain about twelve fuch disks, whirling all round on 
the fame center. It confided of two fquare pillars of 
wood, about five feet high, and three inches broad; 
joined together at top and bottom by a tranfverfe piece 
of 
