ioo Mr. henly’s Experiments and 
this purpofe a pretty large jar was coated and furnifhed : 
as in fig. i. a is the jar; bb the tin-foil coating; c a tin- 
ftand which fupports the jar; d a focket of metal which 
fupports a rod of glafs e ; F a curved wire or plate of 
metal with points, not very fharp ; this wire or plate of 
metal is fattened to the end of a brafs rod g, which rod 
is moveable at pleafure in a fpring tube h, that tube being 
fixed by a focket upon the top of the glafs rod e. The 
charging wire of the jar communicates with both parts of 
the infide coating of the jar by horizontal wires (the ends 
of which are bent a little downwards) fixed at right an- 
gles to each other, in order to prevent fhaking and ratling. 
THE USE OF THE DOUBLE COATED JAR. 
According to Dr. franklin’s theory, the fame quantity 
of the eleftric matter which is thrown upon one of the 
furfaces of glafs in the operation of charging it, is at the 
fame time repelled or driven out from the other furface, 
and thus one of the furfaces becomes charged plus, the 
other minus ; and that this is really the cafe is, I think,, 
fatisfattorily proved by this contrivance. For example, 
place the jar as ufual, with the knob in contact with the 
prime conductor ; then work the machine, and the appa- 
ratus being perfectly dry and in good order, a fmall lu- 
minous fpark will appear upon the upper point of the 
wire f (a plain indication that the point is then receiving 
6 electricity 
