xxviii Of the Method of rendering very fenftble 
condenfer, fo that when the faicl metal plate is afterwards fepa- 
rated from its proper plane, the electricity in it appears much 
condenfed and vigorous ; fo when the fame metal plate con-? 
tains a fmall quantity of electricity, and fuch as cannot give a 
fpark or afreCl an electrometer, that electricity may be rendered 
very confpicuous by communicating it to another fmall metal 
plate or condenfer. 
Mr. cavallo was the firft who thought of this improve- 
ment, which he derived by reafoning upon my experiments. 
He actually made a fmall metal plate not exceeding the fize of a 
fhilling: this fecond condenfer is certainly of great ufe in many 
cafes, in which the eleCtricity is fo fmall as not to be at all, or 
not dearly, obfervable by my method or a firft condenfer only, 
as has been evidently proved by forne experiments we made 
together. Sometimes the ufual metal plate of my condenfer 
acquired fo fmall a quantity of eleCtricity, that being after- 
wards taken up from the inferior plane, and prefented to ail 
extremely fenlible electrometer of Mr. cavallo’s conftruCtion, 
it did not affeCt it. In this cafe, if the faid metal plate, thus 
weakly electrified, was made to touch the other fmall plate 
properly fituated, and that was afterwards brought near an 
electrometer, the eleCtricity was then generally ftronger than 
what would have been fufficient to afcertain its quality. 
Now, if by the help of both condenfers the intenfity of the 
eleCtricity has been augmented 1000 times, which is by no 
means an exaggeration, how weak muft’ then be the eleCtricity 
of the body examined ? how fmall muft that eleCtricity be 
which is produced by rubbing a piece of metal with one’s 
hand, fince when this eleCtricity is condenfed by both con- 
denlers, and then is communicated to an eleftrometer, it can 
hardly affedt that inftrument ? Yet it is fufficient to afford con- 
viCtion, that the metal can be electrified by the fridtion of a 
perfon’s hand. Some years ago, viz. before the difcovery of 
our condenfer, and of Mr. cavallo’s fenfible electrometer, 
we were very far from being able to difcover fuch weak excita- 
tions ; whereas, at prcfent, we can obferve a quantity of elec- 
tricity incomparably fmaller than the fmalleft obfervable at 
thofe times. 
5 
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