Small Quantities of Electricity. p 
only, and is furnifhed with an infulating handle, which is per- 
pendicular to its upper furface. 
This apparatus is ufed in the following manner. The plate 
B being laid upon the plate A, the fmall quantity of electricity, 
which is required to be multiplied, is communicated to the 
under part of the plate A, and at the fame time the upper part of 
B is touched with a finger ; then the finger is fird removed ; 
the plate B is afterwards removed from over the plate A. The 
plate C is now laid upon B, and its upper furface is touched, for 
a fhort time, with a finger. By this operation it is clear, that if 
the eleClricity communicated to the plate A is pofitive, the plate 
B mud; have acquired a negative electricity, and the plate C muff 
have acquired the pofitive, viz. the fame of the plate A. Now 
the plate B, being feparated from C, is laid as before upon A ; 
the edge of C is brought into contaCt with the under part of 
the plate A, and at the fame time the upper part of B is 
touched with a finger, by which means the plate B, being 
aCled upon by the atmofpheres of both the plates A and C, 
will acquire nearly twice as much eleCtricity as it did the fird 
time, and of courfe will render the plate C, when that is laid 
upon it, proportionably more electrified than before : thus, by 
repeating this operation, the eleClricity may be increafed to any 
required degree. 
The varnifh on thofe furfaces of the plates which are to lie 
contiguous to each other ferves to prevent the metal of one 
touching the metal of the other; for in that cafe, in dead of 
one plate canting a contrary electricity in the other, the elec- 
tricity of the fird would be gradually communicated to the 
others, and would be difiipated. 
As loon as 1 underdood the principle of this contrivance, I 
hadened to condruCl fuch an apparatus, in order to try feveral 
Vol. LXXVIIf. C ' expe- 
