430 
ELECTRICITY, 
a communication being made from one fide to the other 
by fome conductor, the plane, or veffel, will be fuddenly 
difcharged, with an explofion.—There is a (Irong attrac¬ 
tion (compare Prop. XII. and XV.) between the fluids 
on oppofite Tides of the glafs, or the fluid which is accu¬ 
mulated on one fide makes a powerful effort towards the 
other fide where the fluid is deficient ; but the fubftance 
of the glafs itfelf being "impervious to tlie electric fluid, 
the accumulated fluid cannot pafs to the deficient fide 
till a communication is made between them by fome con¬ 
ducting fubftance. When fuch a communication is made, 
becaufe tlie metallic coating touches the whole furface 
of the electrified glafs, the whole quantity of redundant 
fluid eafily patfes from the fide which was pofitively elec¬ 
trified to the other. 
Let a plate of glafs, coated with tin-foil (except about 
one inch and a half from the edge), be charged, as de- 
fcribed Prop. XV. Upon making a communication from 
one fide to the other by the difcharging-rod, there will 
be a hidden difcharge. The fame may be done with the 
Leyden phial, ©barge ajar coated on the infide with wa¬ 
ter, ftiot, or brafs duft, and held on the outfide by the 
hand, then difcharge it in a dark room. 
If two equal circular brafs plates, one of which is fuf- 
pended by a long metallic rod from the conductor paral¬ 
lel to the horizon, and the otlier, fupported by a'conduc- 
tor, is placed parallel and oppofite to the firft, be electri¬ 
fied ; the plate of air between them will be charged by 
the brafs plates. 
Let one coated jar be fufpended by a wire under ano¬ 
ther; let the upper jar be charged by taking fparks from 
the conductor ; the lower uninfulated jar will be charged 
with the eleCtric fluid which paffes from the fide nega¬ 
tively eleCtrified of the upper jar.—A coated jar cannot 
be charged unlefs its outer furface be connected with 
fome conductor. For without fuch a conductor, the 
eleCtric fluid cannot pafs from or to the outer furface, 
which is neceffary in order to charge the jar. 
When a coated glafs veffel is charged, the charge of 
eleCtric fluid is in the glafs, and not in the coating.—Lay 
a plate of glafs between two metallic plates, as deferibed 
Prop. XV. Having charged the plate of glafs, remove 
the upper plate of metal by a glafs handle, with fome 
non-conduCting fubftance, as filk; remove the eleCtrified 
glafs plate, and place it between two other plates of me¬ 
tal uneleCtrified and infulated ; the plate of glafs thus 
coated afrefh will ftill be charged. 
The difcharge of a plate of glafs, Leyden phial, &c. 
is made by reftoring the equilibrium which was deftroyed 
by the charging; and it is effected by forming a commu¬ 
nication between the overloaded and the exhaufted fide; 
and if the communication be made by metal, or other 
good conductors, the equilibrium will be reftored with 
violence, the redundant electricity on one fide will rufti 
with great rapidity through the metallic communication 
to the exhaufted fide, and a large explofion will be made, 
that is, the flafh of eleCtric light will be very vifible, and 
the report will be very loud. 
XVIII. If the conductor be eleCtrified pofitively, that 
fide of the jar with which it has a communication will be 
eleCtrified pofitively, the other, negatirely.—Charge one 
Leyden jar on the infide pofitively, and another negative¬ 
ly, and obferve, in a dark room, the different appearances 
of the eleCtric fluid upon the point of a wire brought near 
to the ball which is connected with the inner fide of each 
jar : when the point is prefented to the jar pofitively 
eleCtrified on the inner fide, it will exhibit the appear¬ 
ance of a ftar; when prefented to the other, that of a 
pencil.—Obferve the different appearances, in a dark 
room, when with the fame charged jar the point is pre¬ 
fented towards the fide pofitively, and towards the fide 
negatively, eleCtrified. 
Between two jars, charged one negatively and the other 
pofitively, fufpend by a filken firing a cork ball, from 
which ftiort threads hang freely ; the ball will pafs with 
a rapid motion from one to the other, and, being firft at¬ 
tracted towards the jar pofitively eleCtrified, then towards 
the other, it will receive the fluid from the former, and 
communicate it to the latter, till both are difcharged. IT 
both be charged in the fame manner, the cork will re¬ 
main at reft.—If, after a jar is charged, the uncoated 
part of the jar be moiftened by the breath, or by fleam, 
the jar placed upon a conductor will be gradually dif¬ 
charged, and the fluid will be feen, in a dark room, to 
flafh ftrongly front one fide to the other: if the jar be in¬ 
fulated, the flufnes will be greateft on the fide pofitively 
eleCtrified.—Let a difeharging rod be applied without its 
balls to a charged jar, in fuch manner as to difcharge the 
jar gradually : the point which approaches towards the 
fide pofitively eleCtrified, will, in a dark room, exhibit 
ftar; the other point, a cone or pencil. 
Within the receiver of an air-pump place two well-po- 
lifiied brafs balls, the lower fupported on a brafs ftem by 
the plate of the pump, the other fixed on a ftem which is 
moveable in the neck of the receiver : let the balls be 
brought within the diftance of four or five inches from 
one another; then let the upper ball be connected with 
the conductor, and eleCtrified pofitively : a lucid atmo- 
fphere will, in a dark room, appear on the lower furface 
of the upper ball ; whereas if the upper ball be nega¬ 
tively eleCtrified, the lucid atmofphere will be feen on 
the lower ball.—This laft experiment eftablifhes the the¬ 
ory of a Jingle eleCtric fluid : for if there were two contrary 
fluids, there mult in this experiment be an atmofphere 
about each ball, attracting each other. 
XIX. The electric fluid can be conveyed through an 
infulated conductor of any length, and its paffage from 
one fide of a charged jar to the other, is apparently in- 
ftantaneous, through whatever length of a metallic or 
other good conductor it is conveyed.—Let a long wite, 
palling round a room, fufpended by filk cords, be a part 
of the circuit of communication from one fide of a charged 
jar to the other, the difcharge will be apparently at the 
fame inftant in which the communication from one fide 
to the other is completed. Let any number of perfons 
make a part of the circuit of communication ; the fluid 
will pafs inftantaneoufly through the whole circuit.—The 
ftiock of the Leyden jar has been tranfmitted through 
wires of feveral miles in length, without taking any fen'- 
lible fpace of time. Dr. Prieftley relates feveral curious 
experiments made with a view of afeertaining this point 
foon after the difeovery of the Leyden phial. See Priejl~ 
ley’s Hijl. of EleBricity. 
XX. The hidden difcharge of a charged jar gives a 
painful fenfation to any animal placed in the circuit of 
communication, called the elcBric /hock. —The difeovery 
of the effeCts of electricity, as exhibited by the Leyden 
jar, immediately raffed the attention of all the philofo- 
phers in Europe. The account which fome of them gave 
of the firft experiments to their friends, border very much 
on the ludicrous. M. Mufchenbroek, who tried the expe¬ 
riment with a glafs bowl, told M. Reaumur, in a letter 
written foon after the experiment, that he felt himfelf 
(truck in his arms, (houlder, and bread, fo that he loft 
his breath ; and was two days before he recovered from 
the effefts of the blow and the terror. He added, that 
he would not take a fecond fliock for the whole kingdom 
of France.—M. Allqmand, who made the experiment 
with a common beer-glafs, faid, that he loft his brea h 
for fome moments, and then felt fuch an intenfe pain all 
along his right arm, that he was apprehenfive of bad 
conlcqiiences; but it foon went off without any inconve¬ 
nience.—Notvvithftanding the parade made by thefe pbi- 
lofophers, the ftiock was probably not, by any means, 
ftronger than what many children of (ix or feven years 
old would bear without the fmalleft hefitatiop. Their 
deferiptions mull have arifen through terror impreffed on 
the mind by the novelty of the phenomenon, or the love 
of the marvellous. 
The force of the eleCtric fliock may be increafed, by 
z increafing 
