600 
ELECTRICITY. 
philosophical to reject an hypothesis, which 
explains some facts greatly to our satisfaction, 
merely because it lias not as yet explained 
„ every thing. 
But leaving theories, especially in the pre- 
sent very imperfect state of this science, let 
us endeavour to keep our attention on those 
facts which are well known, and generally 
and most consistent with the design of this 
work, only to specify and describe those 
parts of the apparatus which are most in use, 
and essential to the performance of the 
experiments which are already before the 
public. 
The instruments commonly employed in 
this branch of science, may be classed under 
six heads: 1st. The instruments used for 
admitted. The following statement seems to 
comprise the general principles on which this 1 exciting electricity, viz. glass tubes, plates, 
wonderful fluid is known to act. It is ex- 1 a ‘ ul cylinders. 2d. d hose for conducting 
tracted from M. Brisson, a French writer of j * lc Gectric matter, which are cnieiiy of 
deserved reputation, and it is such as a few 
easy. experiments will serve to confirm. 
The electric fluid is probably the same in 
essence with that of light and heat, but com- 
bined with a substance which affects the or- 
gans of scent. 
metal. 3d. Those intended for accumula- 
ting the fluid, or, in technical language, 
for receiving a charge, such as coated bottles 
or jars, commonly called Leyden phials. 
4th. Those which are intended to produce 
j more formidable effects, such as electric bat- 
1 teries. 5th. The instruments employed for 
W hen bodies are electrified by glass, they ascertaining the quantity of electricity", called 
burnish tufts or pencils of light ; but it elec- electrometers ; and lastly, those employed 
trdiecl by sulphur, or resinous substances, for retaining the electric power, 
t-hey only produce points, or sparks of light ; J. Of the first class of these instruments it 
bodies presented to those electrified bv glass, | was necessary to treat, in explaining the first 
produce only luminous points ; while those principles of electricity ; anil there is nothing 
which are presented to bodies which are elec- that can be added in further illustration of the 
tntied by sulphur, produce beautiful pencils, ; nature of electrical machines, 
or tufts ot light. | [f. The nature and uses of such conduc- 
Bodies are electrified either by friction or- tors as are attached to the machine, have 
communication, i o electrify bodies by com- been also explained; but any instrument 
munication, it is necessary to insulate them ; which serves to convey the electrical in- 
and th *2 substances the most proper for in- 1 fluence from one bodv to another, may be 
sulating others are those which electrify the regarded as a conductor. With this view, 
.best by friction. i wires and chains are employed to form a 
(Bass, however, though it electrifies very communication between different bodies ; and 
well by friction, electrifies also by comfnurn- under this head we may also class the corn- 
cation, even without any preliminary pre- mon discharging rod, the principle of which 
pa ration ; yet it is very proper for insula- consists in a rod of metal, sometimes with 
! knobs at the ends, which is furnished with a 
The electrical matter is not produced en- glass handle, to prevent the shock from pas's- 
tiiely from the bodies upon which the elec- ing through the bodv of the operator. In 
tiihing machine acts; the adjacent bodies, plate, fig. 5, is the jointed discharging rod, 
oi substances, contribute towards its produc- which is m st commonly used. D is the 
! glass handle cemented into the brass socket C ; 
The energy of the electric virtue is aug- j and ef are the brass wires, which are curved, 
mooted, in conductors, more by an increase j and may be opened bv the joint to any ex- 
°f surface, than by an augmentation of the | tent that may be required. The wires are 
. _ j pointed, as it is sometimes necessary to draw 
Electrified bodies adhere one to another, j off a charge in that way; and the knobs a b 
so that, on some occasions, they cannot be > are made to screw, or sometimes only to fit 
separated without a considerable effort. 
Electricity accelerates the evaporation of 
liquors, an<l the perspiration of amnia's, 
I he pencils or tufts of light, which are 
seen at the extremities or angles of electrified 
bodies, are always composed of divergent 
rays when they pass through the air ; but if a 
non-electric, or conducting body, is presented 
to them, they lose a great deal of their diver- 
gency ; their rays sometimes become even 
convergent, in order that they may approach 
towards that body which is more permeable 
than the air ; and if they are made to pass 
into a vacuum, they will assume the form of 
a large branch of light nearly cylindrical, or 
in the form of a spindle. 
The spark which shines between two bodies 
is capable of setting combustible matters on 
fire. ' 
Electrical instruments, or apparatus ., — The 
experiments in electricity are so v.tV'^ns, that 
the apparatus may be increased almost agree- 
ably to every man’s fancy ; and, in general, 
he who wishes to make new experiments, 
will find it necessary to make an addition 
suited to the object of his inquiry. It will be, 
on to the ends of the wires. It is most fre- 
quently usee, with the knobs, particularly in 
discharging large jars and batteries. See 
rig. 6. 
Henley’s universal discharger consists of 
two wires, supported by glass feet, with a 
small table between them to support any 
thing that may be the object of the experi- 
ment. It is found to be a very useful instru- 
ment for a variety of purposes, and is com- 
posed of the following parts: A (fig. 7.) is a 
flat board, about fifteen indies long, four 
broad, and ofte thick. BB are two glass pil- 
lars, cemented in two holes upon the borad A, 
and furnished at top with brass caps, each of 
which lias a turning joint, and supports a 
spring tube, through which the wires Dl) 
slide. Each of the caps is composed of three 
pieces of brass, connected so that the wires 
L) D, besides their sliding through the sock- 
ets, have a horizontal and vertical motion. 
Each ot the wires D D is furnished with an 
open ring at one end, and at the other it has 
a brass, ball, which, by a short spring socket, 
is slipt upon the pointed extremity, and may 
: be removed. E is a circular piece of wood, 
therefore, proper, on the present occasion, ^having oh its surface a slip of ivory inlaid, 
and furnished with a foot, which is fastened 
in the middle of the bottom A. 
There is another part of an electrical 
apparatus, originally of German invention, 
which, before we conclude this branch of the 
subject, it may not be improper to notice, as 
it is chiefly illustrative of the electrical attrac- 
tion. This apparatus consists of three small 
bells, (fig. 8.) suspended from a narrow plate 
J of metal ; the two outermost by chains, and 
; that in the middle (from which a chain y KS 
{ passes to the floor) by a silken string. Two 
! small knobs of brass are also hung, bv silken 
! strings, on each side of the bell m the mid- 
dle, which serve for c appers, 
j If an apparatus of this kind is joined to one 
I of 'those conducting rods, erected to protect 
| buildings from the effects of lightning, it will 
1 serve to give notice of tiie approach and pas- 
sage of an electrical cloud. 
111. In the infancy of every science, the 
inventions are simple. The first telescope 
was formed of two spectacle-glasses fixed 
upon a board ; the first electrical bottle was 
a common apothecaries’ phial, with an iron 
nail in the inside, which was afterwards 
changed for a wire. The artist who framed 
the one, did not expect that his discovery 
would enable future philosophers to explore 
and measure -the face of a planet, or to count 
the host ot heaven ; nor did the inventor of 
the other, probably, suppose that his little 
phial, in the hands of future operators, would 
enable human power to vie with the most 
formidable of nature’s efforts, to melt the 
hardest metals, and even to deprive plants 
and animals of life. 
It would be an error, however, to suppose 
that on the form of the glass depends the 
success of the experiment. If any piece of 
glass, of whatever form, cylindrical or other- 
wise, is coated with a conducting substance, 
it may be made to accumulate the electrical 
matter. In this case, one side of the glass, 
if it does not exceed a given thickness, will 
be positively electrified, and the other ne- 
gatively. 
As, however, flat plates are neither neces- 
sary nor convenient for this purpose, jars, or 
bottles with wide necks, are usually em- 
ployed. These are made of various shapes 
and magnitudes, but the most useful are thin 
cylindrical glass vessels, about four inches in 
diameti r, and fourteen in height, coated with- 
in and without (except about two or three 
inches from the top) with tin-foil, or any other 
conducting substance. 
If one side of this jar is electrified, while 
the other side communicates with the earth, 
it is said to be charged. 
When a communication is formed from 
one side of the jar to the other by a conduct- 
ing substance, after it lias been charged, an 
explosion will take place, and this is called 
discharging the jar. The jar, however, is 
incapable of being charged when it is insu- 
lated; that is, when neither side commu- 
nicates with the earth. When it is charged, 
the two sides are in contrary states ; the one 
being positively, the other negatively elec- 
trified. 
A jar is said to be positively electrified, 
when the inside receives the fluid from the 
conductor, and the outside is connected with 
the earth. It is negatively electrified when 
the outside receives the fluid from the con- 
ductor, and the inside communicates with 
