20 Mr. cavallo’s Account of fome 
Powder of rolin, whether it be let fall from paper, 
glafs, or a metal fpoon, electrifies the plate ltrongly ne- 
gative; the fpoon, if infulated, remaining ftrongly pofi- 
tive. Flower of fulphur produces the fame effeCt, but in 
a lefs degree. 
Pounded glafs, let fall from a piece of paper, made dry 
and warm, electrifies the plate negatively, but not in fo 
ftrong a degree as rofin. If it is let fall from a brafs cup, 
it electrifies the plate pofitively, but in a very fmall 
degree. 
Steel filings, let fall either from a glafs phial or paper, 
electrified the plate negatively ; but brafs filings, treated 
in the fame manner, electrified the plate pofitively. 
The amalgam of tin-foil and quickfilver, gunpowder, 
or very fine emery, eleCtrify the plate negatively when 
they are let fall upon it from a glafs phial. 
Quickfilver poured from a glafs phial electrifies the 
plate pofitively. 
Soot from the chimney, or allies from common pit 
coals mixed with fmall cinders, eleCtrify the plate nega- 
tively, when they are let fall from a piece of paper. 
i- S. ^ 
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