Obfervations in EleSIricity. 105 
which the wire pafies ; after a few turns of the globe, 
this fpark becomes a fine brufh, darting out from the 
cork, and gradually lengthening, till it forms a beautiful 
arch, the end of it regularly extending downward, 
till it reaches the edge of the coating and refts upon it 
(fee fig. 5.). I remember, when I firfl: fhewed thefe 
experiments to my fincerely refpeCted and worthy friend 
the late ingenious Mr. ferguson, f. it. s. he exprefled 
great fatisfaflion ; and allured me, that he thought 
them fome of the molt convincing he had ever feen 
exhibited for the purpofe. If the bottle be dry, it will, 
in both cafes, be difcharged fpontaneoully ; but if the 
uncoated part of the glafs be then breathed upon, the 
appearances may be produced at pieafure. I have lately 
prepared another bottle for this purpofe, the infide of 
which is coated in the ufual manner; but the out fide is 
covered with fquare pieces of tin-foil about a quarter of 
an inch broad, and about three-fixteenths of an inch 
diftant from each other; the bottom is compleatly co- 
vered with the coating (fig. 4.). If in charging this bot- 
tle, the electricity pafled abfolutely through the glafs, it 
would find a ready conveyance by the coated bottom into 
the table (and then indeed it could never be charged at 
all) ; but the truth is, that this bottle does not become 
charged till ftrong flafhes of electricity have pafled, 
Vol. LX VII. P diverging 
