28 Mr. Ben net's Defcription of 
The pofitive eleCtricity of the chalk, thus blown, is commu* 
nicated becaufe part of the powder flicks to the cap ; but the 
negative is not communicated, the leaf gold collapfing as loon 
as the cloud of chalk is difperfed. 
adly, A piece of chalk drawn over a brufh, or powdered 
chalk put into the brufh, and projected upon the cap, eleCtrifics 
it negatively ; but its eleCtricity is not communicated. Fig. 4. 
^dly, Powdered chalk blown with the mouth or bellows 
from a metal plate placed upon the cap, electrifies it perma- 
nently pofitive. Fig. 5. Or if the chalk is blown from the 
plate, either infulated or not, fo that the powder may pafs 
over the cap, if not too far off, it is alib pofitive. Or if a 
brufh is placed upon the cap, and a piece of chalk drawn over 
it, when the hand is withdrawn the leaf gold gradually opens 
with pofitive electricity as the cloud of chalk difperfes. 
4thly, Powdered chalk falling, from one plate, to another 
placed upon the inftrument, eleCtrifies it negatively. Fig. 6. 
Other methods of producing eleCtricity with chalk and 
other powders have been tried ; as projecting chalk from a 
goofe wing, chalking the edges of books and clapping the 
book fuddenly together, alfo fifting the powder upon the cap ; 
all which eleCtrified it negatively : but the inftrument being 
placed in a dufty road, and the duff {truck up with a flick near 
it, eleCtrihed it pofitively. Breaking the glafs tear upon a book 
eleCtrified it negatively, probably by friction in the aCt of 
fhivering, for when broken in water it did not eleCtrify it. 
Wheat flour, and red lead, are ftrongly negative in all 
cafes where the chalk is pofitive. The following powders were 
like chalk : red ochre and yellow, rofin, coal afhes, powdered 
crocus metallorum, aurum mofaicum, black-lead, lampblack 
(which was only fenfible in the two firft methods), powdered 
quick- 
