the earth ; but it is necessary that the jar 
charging negatively should be insulated, be- 
cause the tluid is, in the first instance, con- 
v.eved to the coaling, and would be imme- 
diately carried to the earth if it was not pre- 
vented bv the interposition of an electric 
substance. 
'Fite most usual forms of the Leyden phial, 
or electrical jar, are represented in ligs. 6, 9, 
and 10, and its nature may be exemplified 
by the following easy experiments. 
' Place the jar (fig. 6) on a table, or any 
other non-electric body which communicates 
with the earth, and let the ball on the top be 
about one-eighth of an inch from the ball of 
the conductor i/. If the machine is turned, 
sparks may be perceived passing from the 
ball of the conductor to the ball of the jar. 
When this effect ceases, and no more sparks 
arc perceived to pass from the conductor, 
the jar may be considered as charged, the 
inside positively, and the .outside negatively. 
To discharge the jar, all that is necessary is 
to form a communication between the outer 
and the inner coating of the jar or phial, that 
the surplus electricity mav be conveyed from 
the one to the other. To avoid the painful 
sensation which is the consequence of the 
shock, this is usually performed with the 
discharging rod, see ligs. 5 and 6. The ope- 
rator then holds the rod by the glass handle 1), 
and all that is necessary is to place one knob 
close to the outer coating, and then bring the 
other knob near the ball of the jar, when it 
will be discharged with an explosion propor- 
tioned to the quantity of electricity it lias 
received. If, when the jar is charged, a 
person touches the outside with one hand, 
and brings the oilier near the knob of tin* jar, 
he will then receive the shock. A chain is 
sometimes concealed under the carpet, con- 
nected with the outside coating, and another 
is connected with the top of the jar; if then 
a person standing on the one, is induced to 
! )ut his hand incautiously on the other chain, 
ie will receive a shock, ‘to his groat surprise 
and the entertainment of the company: but 
care should be taken that the shock should 
not, in this case, be too strong. Mr. Canton 
used to amuse himself in this way, by elec.- 
' trifving the latch of his door, which was 
insulated, and giving a shock to the venders 
of old clothes, whom he allured by a well 
known signal, to the. magic ground. An 
optician in London, some years ago, being 
teazed by an impertinent neighbour, who 
amused himself with knocking at his door, 
contrived to insulate the knocker, which was 
connected, by a wire, with a charged jar, 
and, on the unfortunate, adventurer attempt- 
ing to repeat his accustomed intrusion, he 
received a charge, which, it is reported, felled 
him to the ground. 
To illustrate further the nature of the 
Leyden phial, place the same jar, fig. 6, on 
an insulated stand ; bring the coating in con- 
tact with the conductor; turn the. machine, 
and, after a few turns, remove the phial from 
the conductor; then form a communication 
between the outside and the inside of the 
phial, by means of the discharging rod ; in 
this case’, there will be no explosion, because, 
both sides being insulated, the bottle was not 
charged ; but if a chain is suspended from 
the brass ball of the phial to the table, and the 
coating brought in contact with the conductor, 
after a few turns of die machine, remove 
VOL. I. 
ELECTRICITY. 
the phial as before ; then if the discharger 
is applied, an explosion will, be .heard, and 
the bottle will be discharged ; because, in this 
case, the insulation of the inside is destroyed 
bv the chain, and the phial becomes capable 
of receiving a charge. 
That the charge of a coated jar resides in 
the glass, and not in the coating, is proved in 
the following manner: Set a plate of glass 
between two metallic plates, about two inches 
in diameter, smaller than the plate of glass; 
charge the glass, and then remove the upper 
metallic plate by an insulated handle ; take 
up the glass plate, and place it between two 
other plates of metal un electrified and in- 
sulated, and the plate of glass thus coated 
afresh will still be charged. The following 
experiments are further illustrative ot the 
nature of the Leyden phial. 
A cork ball, or an artificial spider made of 
burnt cork, with legs of linen thread, sus- 
pended bv silk, will play between the knobs 
of two -bottles, one of which is charged posi- 
tively, the other negatively, ami will, in a 
little time, discharge them. See fig. 10. 
A ball suspended on silk, and placed be- 
tween two brass balls, one proceeding from 
the outside, the other from the inside of a 
I .eyden jar, when the bottle is charged, will 
fly from one knob to the other, and by thus 
conveying the fluid from the inside to the 
outside of the bottle will soon discharge it. 
An insulated cork ball, after having re- 
ceived a spark, will not play between, but be 
equally repelled by two bottles, which are 
charged with the same power. 
A wire is sometimes fixed to the under part 
of the insulated coated phial (fig. 13) ; and b c 
is another wire fitted to the former, and at 
right angles with it; a brass fly (fig. 14) is 
placed on the point o^ this wire; change the 
bottle, and all the time the bottle is charging 
the fly will turn round ; when it is charged the 
motion will cease. If the top of the bottle is 
touched with the finger, or any other con- 
ducting substance, the flv will turn again till 
the bottle is discharged. The fly will electrify 
a pair of balls positively while the bottle is 
charging, and negatively when it is dis- 
charging. 
When a Leyden phial, positively charged, 
is insulated, it will give a spark from its knob 
to an excited stick of wax, but not a spark 
will pass at that time between it and an ex- 
cited glass tube. 
An additional quantity of the fluid may be 
thrown on one side of the jar, if, by any con- 
trivance, an equal quantity be made to es- 
cape from the other, and not otherwise. 
jV. Electricians, in order to increase the 
force of the electric explosion, connect several 
jars, or Leyden phials, together in a box ; 
and this is called an electrical battery. 
Fig. 12 is a battery composed of twelve 
jars, coated in the inside and outside with tin- 
foil, which altogether contain about twelve 
feet of coated glass. About the middle of 
each of these jars is a cork that sustains a wire, 
which, at the top, is fastened round, or sol- 
dered to the wire, knobbed at each end; 
which connects the inside coatings of three 
jars ; and by four wires, such as C, D, E, F, 
the inside coatings of all the twelve jars may 
be connected together. 
The square box that contains these jars is 
of wood, lined at the bottom with tin-foil, and 
has -two ha mil es .on two opposite sides, by 
4 G 
'(M 
which it may be easily removed. In one side 
of the btix is a hole,' through this an iron 
hook passes, which communicates with the, 
metallic lining of the box, arid consequently 
with the outside coating of all the jars. To 
this hook is fastened a wire, the other end of 
which is connected with the discharging rod.' 
The battery represented in the plate, is a 
small one, in comparison to those now fre- 
quently used, and much too weak for the • 
purpose of some experiments. But it is suf- 
ficient to give an idea of its construction ; and' 
when a large batterjy is to be constructed, it 
is better to "make two, three, or more small 
ones, as represented in the plate, than a single 
large battery, which is heavy, and, on several 
accounts, inconvenient. The force of several 
small batteries may be easily united by a wire 
or chain ; and thus they may be made to art 
in every respect like a large one. 1 he best 
construction of a battery is to have a wire 
from everv jar, connected" with a ball at the 
top, in form of a win -cage. 
The force of accumulated electricity, great 
as it appears by the experiments performed 
with a single coated jar, is very small when 
compared with that which is produced by a 
number of jars connected together ; and it 
the effects of a single jar are surprising, the 
prodigious force of a large battery is certainly 
astonishing. Experiments of this kind should 
be conducted with great caution;, and the 
operator ought to be attentive not only to 
the business in hand, but also to the persons, 
who may happen to be near him, prohibiting 
their touching, or even coming too near any 
part of the apparatus : for it a mistake i« 
performing other experiments may be dis- 
agreeable, those in the -discharge of a large 
battery may be attended with dangerous con- 
sequences. 
When a battery is to be charged, instead 
of a large prime conductor, a small one is 
much more convenient: for, in this case, the 
dissipation of the electricity is not so con- 
siderable. The quadrant electrometer, here- 
after to be described, which shews the height 
of the charge in the battery, may be fixed 
either upon the prime conductor, or upon the 
battery ; in which case, it should be fixed 
upon a rod proceeding from the wires of the 
jars; and if the battery is very large, it 
should be elevated two or three feet above 
them. 
The index to the electrometer, in charging 
a large battery, will seldom rise so high as 90, 
because the machine cannot charge a battery 
so high in proportion as a single jar. Its limits 
are often about 60° or 70°, more or less, in pro* 
portion to the size of the battery and the force 
of the machine. 
Every broken jar in a battery must be taken 
away, before it is possible to charge the rest. 
It lias been recommended, not to discharge 
a battery through a good conductor, it the 
circuit is not at least five feet long; but it 
must be observed, that in proportion to the 
lengthening of the circuit the force of the 
shock will be lessened. 
Jars made of the green glass manufactur- 
ed at Newcastle, are said to endure an ex- 
plosion without a probability of breaking. 
If the spark from the explosion is con- 
centrated, by causing it to pass through 
small circuits of non-conducting substances', 
the force of the battery will be considerably 
increased, For this purpose, cause the sparks 
