1 8 Mr. cavallo’s Account of fotne 
meter diverge with a very manifeft degree of negative 
electricity, anfvvering my expectations exaCtly. 
The explanation of the ingenious Profeffor lichten- 
berg’s experiment now became very eafy and natural; 
for the powder of rofin, being actually electrified nega- 
tively, could not be attracted, except by thofe parts of the 
eleCtrophorus, which are in a contrary flate, that is, elec- 
trified pofitively. 
It is obferved, that powder of rofin anfwers better for 
this experiment than the powders of other fubftances; 
and accordingly I find, that this powder, when fhaken 
upon the infulated brafs plate, fhews a ftronger degree 
of electricity than the other powders. Indeed the elec- 
tricity of the powder of rofin, not only when fhaken 
upon the brafs plate in the manner above mentioned, but 
fimply let fall upon it from a piece of paper, a fpoon, 
&c. is remarkably great ; half an ounce of it being fuf- 
ficient to make the threads of the electrometer diverge 
as much as they poffibly can. 
This difcovery not only affords an eafy explanation of 
Profeflor lichtenberg’s experiment upon the eleCtro- 
phorus, but fhews a method of exciting powders, which 
has long been a desideratum in the fcience of electricity. 
The method is as follows; infulate a metal plate upon an. 
eleCtric ftand, and connect withit a cork-ball electrometer; 
3 then 
