411 
ELECTRICITY. 
projects by means of a wire. The chain D, connects the 
rubber with the earth, or ground. 
Fig. 4, (hews Mr. Nairne’s patent machine for medical 
purpofes. Its glafs cylinder is about (even inches in dia¬ 
meter, and twelve long, with two prime conductors pa¬ 
rallel to it. The rubber is faflened to the conductor R ; 
and confifts of a cufhion of leather fluffed, having a piece 
of filk glewed to its under part. Thefe conductors are 
of tin covered with black lacker, each of them contain¬ 
ing a large coated glafs jar, and likewife a fmaller one, 
or a coated tube, which are vifible when the caps N N 
are removed. To each conductor is fixed a knob O, tor 
the occafional fufpenfion of a chain to. produce pofitive 
or negative eleCLicity. That part of the winch C, 
which adds as a lever in turning the cylinder, is of glafs. 
Thus every part of the machine is infulated, the cylin¬ 
der itfelf and its brafs caps not excepted ; by which 
means very little of the electric fluid is dillipated, and 
hence of courfe the effe&s are the more powerful. To 
this machine the inventor has adapted flexible conducting 
joints, and a difcharging electrometer, for the more ap¬ 
propriate practice of medical electricity. 
Fig. 5, reprefents the very powerful electrical machine 
invented by the late Mr. George Adams, of Fleet-ftreet, 
London, and improved by Meffrs. W. and S. Jones, in 
I-Iolborn. The cylinder or barrel A B, is fupported by 
two ftrong perpendicular pieces, CD. The axis of one 
cap of the cylinder moves in a fmall hole at the upper 
part of one of the fupports. The oppofite axis paifes 
through the upper part of the other fupport. To this 
axis the winch or handle is fitted. The cufhion, or rub¬ 
ber, is fupported and infulated by a glafs pillar ; the 
lower part of this pillar is fitted into a wooden focket, to 
which a regulating ferew is adapted, to increafe or dimi- 
riifli the preffure of the cufhion againft the cylinder. A 
piece of filk comes from the under edge of the cufhion, 
and lies on the cylinder, puffing between it and the 
cufhion, and proceeding till it nearly meets the collecting 
points of the conductor. The more firongly this filk is 
made to adhere to the cylinder, the (Longer is the degree 
of excitation. Before the cylinder, or oppofite to the 
cufhion, is a metallic tube E F, fupported by a glafs pil¬ 
lar GH. This is the prime conductor, now more fre¬ 
quently called only the conductor. 
The large -electrical machine placed in Teyler’s mu. 
feum at Haerlem, partly deferibed above, has, for the 
electric, two glafs plates of fixty-five inches diameter, 
made of French glafs, as this is found to produce the 
mod electricity next to Englifh flint glafs, which could 
not be made of a fufficient fize: thefe plates are fet on 
the fame horizontal axis, at the diftance of feven inches 
and a half, and are excited by eight rubbers, each fifteen 
inches and a half long; and both fides of the plates are 
covered with a refinous fubftance to the diftance of fix- 
teen inches and a half from the centre, both to (Lengthen 
the plates, and to prevent any electricity from being car¬ 
ried off by the axis. Its battery of jars contains 225 
fquare feet of coated furface, and its effects are aftonifli- 
ingly great, and, without proper care, very dangerous. 
The next principal article of the electrical apparatus, 
is the Leyden phial. This is nothing more than a glafs 
bottle or jar, coated both within and without with tin 
foil, or fome other conducting fubftance, that it may be 
charged and employed in a variety of ufeful and inte- 
refting experiments. Or even flat glafs, or any other 
form, fo coated and ufed, has received the fame denomi¬ 
nation. Aifo a vacuum produced in fuch a jar, &c. lias 
been named the Leyden vacuum. The Leyden phial was 
fo called, becaufe it is faid that M. Cunaeus, a native of 
Leyden, firft contrived, about the clofe of the year 1745, 
to accumulate the eleCtric fluid in glafs. But Dr. Prieft- 
ley afferts that this difeovery jwas firft made by Von 
Kleift, dean of the cathedral in Camin; who, on the 4th 
of November 1745, fent an account of it to Dr. Lieber- 
kuhn at Berlin ; however, thofe to whom Kleifl’s account 
was communicated, could not fucceed in performing his 
experiments. The chief circumftances of this difeovery 
are ftated by Dr. Prieftley in the following manner : 
Profeffor Muffchenbrcek and his friends, obferving that 
electrified bodies, when expofed to the common atinc- 
fphere, which is always replete with conducting particles 
of various kinds, foon loft the mod part of their electri¬ 
city, imagined, that if the electrified bodies could be ter¬ 
minated on all Tides by original eleCLics, they might be 
capable of receiving a (Longer power, and retaining it a 
longer time. Glafs being the molt convenient electric 
for this purpofe, and water tlie mod convenient non-elec¬ 
tric, they at firft made thefe experiments with water in 
common glafs bottles : but no confiderable difeovery was 
made, till M. Cunteus, happening to hold his glafs veffel 
in one hand, containing water, which had a communica¬ 
tion with the prime conductor by means of a wire; and 
with the other hand difengaging it from the conductor, 
when he fuppofed the water had received as much elec¬ 
tricity as the machine could give it, was furprifed by a 
hidden and unexpected (hock in his arms and bread. 
This experiment was repeated with the fame effeCt ; and 
the fird accounts of it were publilhed in Holland by 
Mcffrs. Allumand and Muffchenbroek ; by the abbe 
Nollet and M. Monnier, in France ; and by Meffrs. Gra- 
lath and Rugger, in Germany. M, Gralath contrived to 
increafe the (Length of the (hock, by altering the fliape 
and fize of the phial, and alfo by charging feveral phials 
at the fame time, fo as to form what is now called the 
elcEtrical battery. Fie likewife made the fiiock to pafs 
through a number of perfons connected in a circuit from 
the outfide to the infide of the phial. He alfo obferved 
that a cracked phial would not receive a charge : and he 
difeovered what is now called the refiduum of a charge. 
Dr. Watfon, about this time, obferved a circumdance 
attending the operation of charging the phial, which, if 
purfued, might have led him to the difeovery which was 
afterwards made by Dr. Franklin. He fays, that when 
the phial is well eleCti ified, and the hand applied to it, 
the eleCtric fluid will flafh from the outfide of the glafs, 
wherever touched, and will crackle in the hand. He alfo 
obferved, that when a Angle wire only was faflened about 
a phial, properly filled with warm water, and charged ; 
upon the inflant of its explolion, the electrical corrufca- 
tions were feen to dart from the wire, and to illuminate 
the water contained in the phial. Fie likewife found that 
the flroke, in the difeharge of the phial, was, cateris pa¬ 
ribus, as the points of contaCl of the non-eleCLics of the 
outfide of the glafs; which lead to the method of coat¬ 
ing glafs : in confequence of which he made experiments, 
from whence he concluded, that the effeCt of the Leyden 
phial was greatly increafed by, if not chiefly owing to, 
the number of points of non-eleCLics in contaCl with the 
glafs, and the denfity of the matter of which thefe points 
confided ; provided the matter was, in its own nature, a 
ready conductor of eleClricity. He farther obferved, that 
the explofion was greater from hot water inclofed in 
glaffes, than from cold, and from his coated jars warmed, 
than when cold. 
Mr. Wilfon, in 1746, difeovered a method of giving 
the fiiock, by the Leyden phial, to any particular part of 
the body, without affeCling the red. Fie alfo increafed 
the flrength of the fiiock by plunging the phial in water, 
which gave it a coat of water on the outfide as high as it 
was filled within. He likewife found that the law of ac¬ 
cumulation of the eleCLic fluid in the Leyden phial, was 
always in proportion to the fhinnefs of the glafs, the fur- 
face of the glafs, and that of the non-eleCLics in contaCl 
with its outfide and infide. 
Mr. Canton found, that when a charged phial was 
placed upon eleClrics, the wire and coating would give 
a (park or two alternately, and that by a continuance of 
the operation the phial would be difeharged ; though he 
did not obferve that thefe alternate fparks proceeded from 
the two contrary electricities difeovered by Dr. Frank- 
