MACHINE, 
on any mass of electric matter presented 
fronj witlrout, must be the excess of the 
attractive force of the body over the repul- 
sive force of the electricity it contains. 
Whence a given conductor will attract the 
electric matter the most powerfully when 
the quantity it already possesses is the least 
possible, and its attractive force will de- 
crease as it becomes more saturated with 
electricity. Let tw'o equal conductors, com- 
posed of like matter, be brought within a 
small distance of qach other, then if the 
quantities of electricity they contain be 
equal, the attractions they mutually exert 
on those quantities will be equal, and it will 
remain undisturbed in each body. But if 
one conductor, A, contain more electricity 
than the other, B, the attractive power of 
B will be greatest, and will draw the elec- 
tric matter from A, till an equilibrium is 
obtained. It follows also, that in a number 
of conducting bodies, communicating with 
each other, thq electric matter will be every 
where of the same density, if tlie greatest 
attractive force of the bodies be supposed 
equal ; but if ditferent bodies be supposed 
to attract the electric matter with different 
forces, as is most probable, the densities 
must vary with the forces. This may be 
called the natural state. 
To apply this to the particular instance 
above recited, suppose the end of an insu- 
lated conductor to be brought near the 
prime conductor in a positive state, the 
attractive power of the first mentioned con- 
ductor is greater than that of the prime 
conductor, yet, not being sufficient to draw 
sparks, at the given distance, the only effect 
it can produce is to make the electric mat- 
ter accumulate, and become more dense in 
that part of the prime conductor, near 
which it is presented ; by which accumula- 
tion the rest of the prime conductor be- 
comes less electrified, as experience testifies. 
This accumulated body of electricity repels, 
and consequently rarities the electric mat- 
ter naturally contained in that end of the 
conductor, which is presented to the prime 
conductor ; the rest of the fluid becomes 
more dense, and the other parts of the con- 
ductor which is presented, exhibit signs of 
electricity ; yet, as this conductor in the 
whole contains no more tlian its natural 
quantity, if the electric state be taken oft' 
by drawing the spark, and it be afterwards 
removed from the vicinity of the prime con- 
ductor, it becomes negative throughout, by 
reason of the loss of the spark. If a con- 
ductor be presented to the prime conductor 
ELECTRIC. 
in a negative state, the effects are reversed, 
the attraction being strongest at the prime 
conductor, and the accumulation being in 
the conductor which is presented, it exhi- 
bits a negative state, which being destroy- 
ed, upon removal it becomes positive, by 
reason of the spark which was given to it 
when apparently negative. 
These effects are more considerable the 
less the distance is between the two con- 
ductors ; and the intereedent electric body 
is peculiarly affected : the manner of which 
may be better understood by observing the 
phenomena of non-electrics, separated by 
electrics which are less liable to allow the 
passing of the spark than the air is. 
Upon an insulated horizontal plate of 
metal^ lay a plate of glass, considerably lar- 
ger, so that there may be a rim of three or 
four inches projecting beyond the metal on, 
every side. Upon the glass lay another 
plate of metal, of the same size as the for- 
mer, so as precisely to cover it. Electrify 
the upper plate, and the lower will exhibit 
signs of electricity. Continue the electri- 
zation, and the lower plate will emit spai’ks 
to an uninsulated body for a time, and after- 
wards cease. Separate the plates from the 
glass without uninsulating them, and the 
glass will appear to be possessed of the 
contrary electricities on the opposite sides. 
That side which communicated with the 
prime conductor, during the electrization, 
will have a like electricity, and the other 
the contrary. Take off the electricity of 
the plates of metal, and carefully replace 
the glass on the lower, without destroying 
the insulation, and also replace the upper 
plate with the same precaution. Then, 
with one end of an insulated wire, not 
pointed, but knobbed at the ends, touch 
one of the plates, and bring the other end 
near the other plate : the consequence will 
be that a strong and loud spark will pass 
between it and the wire, the electricity of 
the glass will be discharged, and the plates 
and the wire will exhibit few or no signs of 
electricity. 
An electric body, the surfaces of which 
are thus possessed of the contrary electri- 
cities, is said to be charged. The insulation 
of the lower metallic plate, and of the dis- 
charging wire is not necessary, except for 
the purpose of drawing inferences, respect- 
ing the manner of charging the electric 
plate. If the electricity of the prime con- 
ductor be strong, aij,d the glass thick, the 
discharge will often be made by a spark 
from the one metallic plate to the other. 
