0 
4 g6 'ELECT 
III. Some conductors are more perfect than others; 
and the electric fluid will always pafs through that which 
is moft perfeCt. Hence the fluid will pat's through a wire 
held in the hand.—The following bodies are conductors 
and electrics, put down in the order cf their degrees of 
perfection: Conductors; gold, (liver, copper, by.ifs, iron, 
tin, quickfilver, lead, the other metals, ores, charcoals, 
water, ice, fnow, falts,"toft (tones, fmoke, (team: Non¬ 
conductors, or eleCtrics; glafs, and all vitrifications, even 
tliofe of metals; precious (tones, refins, gums, amber, 
fulplnir, baked wood, bituminous fubftances, wax, (ilk, 
cotton, feathers, wool, hair, paper, air, oil, hard (tones. 
Many eleCtrics become conductor? when heated, and all , 
when moiltened. 
An exh.aufted glafs veftel, on being rubbed, fliews no 
figns of electricity upon its external furface. But the 
eleCtric power cf a glafs cylinder is the ftrongeft when 
the air within is a little rarefied. If the air be con- 
dertfed, or the cylinder he filled with Come conducting 
fubftance, it is incapable of being excited. Neverthelefs, 
a folid (tick of glafs, fealing-wax, fulpliur, &c. may be 
excited. The Tame fubftance, by different preparations, 
is fometimes a conductor, and at others an eleCtric. A 
piece of wood juft cut from a tree is a good conductor; 
le(, it be baked, and it becomes an electric ; burn it to 
charcoal, and it is a good conductor again ; laftly, let 
this coal be reduced to allies, and thefe will be impervious 
to electricity. Such changes are alfo obfervable in many 
other bodies; and very likely in all fubftances there is a 
gradation from the beft conductors to the bed non-con- 
duttors of electricity. 
IV. Non-conduClors retain the fluid on a fmall part of 
their furface where the friCtion has acted ; conductors 
diffufe it over all their furface, and therefore cannot con¬ 
fine it, unlefs they be furrounded entirely by non-con- 
duCtors, that is, be infulated. This is conftantly feen from 
the partial diftribution of the fluid on an excited eleCtric, 
and its univerfal diffufion over a conductor. If a finger, 
or any other conductor, be prefented to an excited glafs, 
cylinder, tube, &c. it will receive a fpark, and in that 
fpark, a fmall part only of the eleCtricity of the eleCtric; 
becqtife the excited eleCtric, being a non-conductor, can¬ 
not convey the eleCtricity of all its furface to that point 
to which the conductor lias been prefented. But if any 
conducting fubftance be brought to a charged metallic 
conductor, it will receive in one fpark nearly the whole 
of the eleCtricity accumulated upon it. The fmall part 
which remains is very trifling in comparifon of the firft 
fpark, and is called the reji'duum. —It was ftated above 
that a body is faid to be pojitively eleCtriJied, when it has 
excited or thrown upon it a greater quantity of the elec¬ 
tric fluid than its natural (hare; and that a body is nega- 
■tively electrified, when it has a lels quantity of the eleCtric 
matter titan is natural to it. 
V. The eleCtric fluid may be excited by rubbing, by 
pouring a melted eleCtric into another fubftance, by heat¬ 
ing and cooling, and by evaporation.—In working the 
eleCtrical machine, the fluid is excited by friCtion. Rub¬ 
bing is the general mean by which all eleCtric fubftances 
that are at all excitable may be excited. Whether they 
be rubbed with eleCtrics of a different fort, or conduc¬ 
tors, they always (hew figns of eleCtricity, and in general 
ftnonger when rubbed with conductors, and weaker when 
rubbed with eleCtrics.—When fulpliur is melted into an 
earthen veftel, if the velfel be fupported by a conducting 
fubftance, the fulpliur, when cold and feparated from 
the velfel, is ftrongly eleCtrical, and will attract light 
bodies.—If fulpliur be melted into glafs veflels, when 
cold, the glafs, whether fupported by eleCtrics or not, 
will be pofitively eleCtrical, and the fulpliur negative.— 
Melted fealing-wax, when poured into fulpliur, becomes 
pofitively electrified, and the fulpliur negative.—Melted 
fealing-wax poured into glafs cups acquires a negative 
eleCtricity ; upon being feparated, the glafs is pofitive.— 
Sulphur melted into metal cups, (hews ao figns of deo¬ 
il I C I T Y. 
tricity till it is feparated from the cup ; then the cup is 
negative, and the (ulpliur is pofitive.—If a ftick of feal¬ 
ing-wax be broken into two pieces, the extremities that 
were contiguous will be found electrified, one pofitively, 
and the other negatively. 
Tlie tourmalin, a (tone which is generally of a deep 
red, or purple colour, about the fize of a walnut, and 
found in the Eaft Indies, while kept in the fame degree 
cf heat, (hews no figns of eleCtricity, but will become 
eleCtrical by increafing or dlminiftiing its heat, and ftronger 
in the latter than in the former cafe. Its eleCtricity does 
not appear all over its furface, but only on two oppofite 
fides, which, may be called its poles, and th*by are always 
in one right line with the center of the (tone, and in the 
direction of the ftrata; in which direction the (tone is 
abfolufely opaque, though on the other fide it is femi- 
tranfparent. Whilft the tourmalin is heating, one of its 
fides, (which vvewill call A,) iseleCtrified plus; the other, 
(called B,) minus. But when it is cooling A is minus, 
and B is plus. If this (tone be excited by friCtion, then 
both its fides at once may be made pofitive. If a tour¬ 
malin be cut into feveral parts, each piece will have its 
pofitive.and negative poles', correfponding to the pofitive 
and negative fides of the (tone from which it was cut.— 
Thefe properties are now found to belong to feveral hard 
and precious (tones as well as to the tourmalin. 
EleCtricity may be produced by the evaporation of 
water in this manner : upon an infulating (tand, as a wine 
glafs, place an earthen veftel, as a crucible, a bafin, See. 
and put into it three or four lighted coals. Let a wire 
be put with one end among the coals, and with the other 
let it touch a very fenfible pith-ball or Cantoivs electro* 
meter. Then pour in a fpoonful of water at once upon 
the coals, which will occafion a quick evaporation ; and 
at the fame time the electrometer will diverge. 
VI. The eleCtric fluid may be lodged in eleCtrics, or 
in infulated conductors, in a greater quantity than natu¬ 
rally belongs to them ; that is, they may be pojitively 
electrified.—In working the eleCtrical machine, tlie cy¬ 
linder acquires more than its natural quantity of fluid by 
excitation; the conductor, by communication : for,while 
there is a free conveyance of eleCtric fluid from the earth 
to tlie rubber, by means of a conducting fupporter, the 
condftCtor will be highly electrified. Tlie eleCtric mat¬ 
ter with which the prime conductor is loaded, is not pro¬ 
duced by the friCtion of the cylinder agaiuft the rubber. 
It is only collected by that operation from theYubber, and 
all the bodies that are contiguous to it. If, therefore, 
the rubber be well infulated, the friCtion of the cylinder 
will produce but little eleCtricity ; for in that cafe the 
rubber can only part with its own (hare, which is very 
inconfiderable. In this (ituation, if the finger be prefented 
to the rubber, fparks will be feen to dart from it to the 
rubber, to fupply the place of that eleCtric matter which 
had pafted from it to the cylinder: if the conductor be 
alfo infulated, thefe fparks will ceale as foon as it is fully 
loaded. 
VII. The eleCtric fluid being accumulated on any bo¬ 
dy, will pafs to any conductor brought near to that body: 
if it pafs from, or be received by, pointed wires, it will be 
conveyed in a continued ftream ; if it pafs from, or be 
received by, a furface which has no (harp points, it will 
be difeharged with an inftantaneous,explo(ion or fpark..—- 
Let the fluid be received from the conductor upon a 
pointed wire, and upon a brafs ball, and this refult ap¬ 
pears. The .eleCtric fluid will alfo be diffufed through 
the furrounding atmofphere, by wires placed upon the 
conductor. Hence arifes tlie neceftity of keeping the 
whole furface of the conductor free from points. When 
a conductor is eleCtrifled by communication, its whole 
eleCtric power is difeharged at once, on the near approach 
of a conductor communicating with the earth; whereas 
an excited eleCtric, in the fame circumftances, lofes its 
eleCtric power only in the parts near to the conductor. 
VIII. If conductors be infulated, they will retain a 
geeate 
