an ekclrical Injlrument, 405 
explain the a&ion of the prefent inftrument. When the plates 
A and B are oppofite each other, the two fixed plates A and C 
may be confidered as one mafs ; and the revolving plate B, toge- 
ther with the ball D, will conftitute another mafs. Ail the 
experiments yet made concur to prove, that thefe two mafles 
will not poflefs the fame electric fiate ; but that, with refpeCt 
to each other, their electricities will be plus and minus. Thefe 
Hates would be fimple and without any compenfation, if 
the mafles were remote from each other ; but as that is not 
the cafe, a part of the redundant ele&ricity will take the form 
of a charge in the oppofed plates A and B. From other expe- 
riments I find that the effeCt of the compenfation on plates 
oppofed to each other, at the difiance of one-fortieth part of 
an inch, is fuch that they require, to produce a given inten- 
lity, at leafb one hundred times the quantity of eleClricity that 
would have produced it in either, fingly and apart. The re- 
dundant eledricities in the mafles under conlideration will 
therefore be unequally diflributed : the plate A will have about 
ninety-nine parts, and the plate C one; and, for the fame rea- 
fon, the revolving plate B will have ninety nine parts of the 
oppofite eleClricity, and the ball D one. The rotation, by de- 
firoying the contaCts, preferves this unequal difiribution, and 
carries B from A to C, at the fame time that the tail K 
connects the ball with the plate C. In this fituation, the elec- 
tricity in B r.Cts upon that in C, and produces the contrary 
Hate, by virtue of the communication between C and the 
ball ; which lafl: muft therefore acquire an eleCtricity of the 
fame kind with that of the revolving plate. But the rotation 
again deflroys the contaCl, and reftores B to its firfi fituation 
•oppofite A. Here, if we attend to the effeCt of the whole 
H h h z re vo- 
