Obfervations in EleBricity. 103 
(fig. 3.) charging it pofitively. The coating b (fig. 3.) 
on the other fide of the glafs throwing off, at the fame 
time, an equal quantity of the electric matter, (vifible in 
the form of a fmall luminous fpark upon the point of the . 
infulated wire f) is thus left in a negative ftate. The 
electricity palling along the infulated wire, flies off from 
the other point of it in a pencil of rays, diverging upon 
the tin-foil coating c (fig. 2.) on the fame fide of the 
glafs, charging it pofitively; while the oppofite coating 
D (fig. 3.) throws off its electricity, which is received in 
a fmall fpark upon the point of the wire (g) oppofed to 
it, and communicating with the earth. Thus, by the 
fame operation of the cylinder, may a pofitive and a ne- 
gative charge of electricity be obtained at the fame time 
upon each furface of the glafs; and by applying two 
curved difcharging rods (which fhould have glafs handles) 
at the fame inftant, fo as to come nearly into contact with 
the coatings upon each furface of the glafs, the whole 
will be difcharged together; or if a pointed wire be pre- 
ferred near to the prime conductor, they will all be dif- 
charged filently, and then the appearances on the points 
of the wires will all be reverfed; that which was a brufh 
or pencil of rays being now a fmall luminous fpark, and 
that which was a luminous fpark being a brufh or pen- 
cil of rays. If the machine be very powerful, the 
rubber 
