409 
ELEC T RICI T Y. 
in elcCtricnl difcharges; a new method of fixing circular- 
coloured fpots on the furfaces of metals, and the mod 
probable difference between eleCtrics and cotlduflors, &c. 
The fcience is. alfo greatly indebted to many other per- 
fons, either for their experiments and imprevements of 
it, or for treatifes and other writings upon it; as Mr. 
Henley, to whom we owe feveral curious experiments and 
obfervations on the eleCtrical and conducting quality of 
different fubftances, as chocolate, vapour, See. with the 
reafon of the difference between them; the fufion of pla- 
tina; tire nature of the eleClric fluid, and its ccurfe in a 
dil'charge ; the method of eftimating the quantity of it 
in electrical bodies by an electrometer; the influence of 
points, &c. Alfo Mcffis. van Marunr, van Swinden, 
Fergufon, Cnvallo, lord ,Mabon, Nairne, &c. for their 
feveral treatifes on the fubjeCt of electricity, any of which 
„may be confulted with advantage for the experiments and 
principles of the. fcience.. •• 
It is natural to imagine that a power of fuch efficacy as 
that cf electricity would eventually be applied to medical 
purpofes; efpecially, fince it has been found invariably 
to increafe the fenfible perfpiration, to quicken the cir¬ 
culation of the blood, and to promote the glandular fe- 
cretion : accordingly, many inftances occur in the latter 
period of the hiftcry of this fcience, in which it has been 
applied with confiderable advantage and fuccefs. And 
among the variety of cafes in which it has been tried, 
there are none in which it has been found prejudicial, ex¬ 
cept pregnancy and the venereal difeafe. In mod difor- 
ders, in which it has been itfed with perfeveran.ee, it has 
given at leaft a temporary and partial relief, and in many 
it has effected a total cure. Of which numerous inftances 
maybe feen in the Philof. Tranf. and the writings on this 
fcience by Meffrs. Lovet, Weflley, Fergufon, Cavallo, 
Wilkinfon, &c. 
It is hardly neceffary to recite the ancient hypothefes 
on this fubjeCt, or the numerous controverfies or exploded 
notions relative to electricity ; fuch as that of the fympa- 
thetic powder of the Peripatetics; that of unCluous efflu¬ 
via emitted by excited bodies, arid returning to them 
again, adopted by Gilbert, Gafl’endus, fir Kenelm Digby, 
and others ; or that of the Cartefians, who aferibed elec¬ 
tricity to the globules of the firft elements, difeharged 
through the pores of the rubbed fubftance, and in their 
return carrying with them thofe light bodies, in whofe 
pores they were entangled : tliefe hypothefes were framed 
in the infancy of the fcience, and of pliilofophy in gene¬ 
ral, and have been, wifely given up. In the more ad¬ 
vanced ftate of electricity there have been fuggefted two 
principal theories, each of which has had its advocates. 
The one, is that of two diftinCt elcElric fluids, repulfive 
with refpeft to themfelves, and attractive of one another, 
adopted by M. dn Faye, on difeovering the two oppofite 
fpecies of electricity, viz. the vitreous and rejinous , and fince 
new-modelled by_ Mr. Symmer. It was fuppofed by him 
that thefe two fluids are equally attracted by all bodies, 
and exift in intimate union in their pores; and that in 
this ftate they exhibit no mark of their exiftence. But 
that the friction of an eleCtric by a rubber feparates thefe 
fluids, and caufes the vitreous eleflricity of the rubber 
to pafs to the eleCtric, and then to the prime conductor 
of a machine, while the refihous electricity of the con¬ 
ductor and eleCtric is conveyed to the rubber : and thus 
the quality of th.e eleCtric fluid, po defied by the conduc¬ 
tor and the rubber, is changed, while the quantity re¬ 
mains the fame in each. In this ftate of feparation, lie 
contends that the two eleCtric fluids will exert their re- 
fpeCtive powers ; and any number of bodies charged witi; 
either of them will repel each other, attract thofe bodies 
that have lei's of each particular fluid than themfelve'S, 
and be (till more attracted by bodies that are wholly de- 
ftitute of it, or that are loaded with the contrary. Ac¬ 
cording to this theory, the eleCtric fpark is fuppofed to 
make a double current; one fluid palling to an electrified 
conductor from any fubftance prefented to it. whilft the 
Vol. VI. No. 360, 
fame quantity of the other fluid paffes from it; and when 
each body receives its natural quantity of both fluids, the 
balance of the two powers is reftot'ed, and both..bodies are 
uneleCtrified. For a further account of this theory, fee 
Dr. Prieftley’s Hiftory, vol. ii. left. 3. 
The other theory, now generally received, is di ft in- 
guiflied under the denomination of pojitive and negative 
electricity, being firft fuggefted by Dr. Watfon, but di- 
gefted, illuftrated, and confirmed, by Dr. Franklin; and 
fince that it lias been known by the appellation of the 
Franklinian hypothefis. It is here fuppofed that all the 
phenomena of electricity depend on one fluid, fui generis, 
extremely fubtile and elaftic, difperfed through the pores 
of all bodies, by which the particles of it are as flrongly 
attracted as they are repelled by one another. When 
bodies pofTefs their natural fliare of this fluid, or fuch a 
quantity.as they can retain by their non-attraCtion, it is 
then laid they are in an uneleCtrified ftate; but when the 
equilibrium is difturbed, and they either acquire an addi¬ 
tional quantity from other bodies, or lofe part of their 
own natural fliare by communication to other bodies, they 
exhibit eleCtrical appearances. In the forrrier cafe it is 
faid th.ey are electrified pofitively, or plus-, and in the other 
negatively, or minus. This eleCtric fluid, it is fuppofed, 
moves with great eafe in thofe bodies that are called con¬ 
ductors, but with extreme difficulty and flownefs in the 
pores of eleCtrics; whence it comes to pafs, that all 
electrics are impermeable to it. It is farther fuppofed 
that eleCtrics contain always an equal quantity of this 
fluid, f'o that there can be no furchurge or increafe' on 
one fide without a proportionable deereafe or lofs 011 the 
other, and vice verfa ; and ® the eleCtric does not admit 
the paflage of the fluid through its pores, tiiere will be 
an accumulation on one fide, and a correfponding defi¬ 
ciency on the other. Then when both tides are connect¬ 
ed together by proper conductors, the equilibrium will 
be reftored by the ruffling of the redundant fluid from 
th.e overcharged furface to the exhaufted one. Thus 
alfo, if an eleCtric be rubbed by a conducting fubftance, 
the electricity is only conveyed from one to the other, 
the one giving what the other receives ; and if one be 
electrified pofitively, the other will be electrified nega¬ 
tively, unlefs the lofs be fupplied by other bodies con¬ 
nected with it, as in the cafe of the eleCtric and infulated 
rubber of a machine. This theory ferves likewife to il- 
luftrate the other phenomena and operations in th.e fcience 
of eleCtricity. Thus, bodies differently electrified will 
naturally attraCt each other, till they mutually give and 
receive an equal quantity of the eleCtric fluid, and the' 
equilibrium is reftored between them'. Beccaria fttppofes, 
that this effeCt is produced by the eleCtric matter making 
a vacuum in its paflage, and the contiguous air afterwards 
collapfing, and fo pufliing the bodies together. 
The influence of points, in drawing or throwing off 
the eleCtric fluid, a moft curious phenomenon, is fup¬ 
pofed to depend on the lefs refiftance it finds to enter or 
pafs off through fewer particles than through a greater 
number, whofe refiftance is united in flat or round fur- 
faces. The electric light is fuppofed to be part of the 
eleCtric fluid, which appears when it is properly agitated; 
and the found of an explofion is produced by vibrations, 
occafioned by the air’s being difplaced by the eleCtric 
fluid, and again fuddenly collapfing. 
Mr. Cavendifli lias published an attempt to deduce and 
explain fome of the principal phenomena of electricity 
in a mathematical and fyftematic manner, from the na¬ 
ture of the eleCtric fluid, confidered as competed of par¬ 
ticles that repel each other, and attraCt the particles of 
all other matter, with a force inverfely as fome lefs power 
of the diftance than the cube, whilft the particles of all 
other matter repel each other, and attraCt thofe of the 
eleCtric fluid, according to the fame law. Philof. Tranf. 
vol. lxi. p. 584-677.—And a fimilar hypothefis arid me¬ 
thod of reafoning has been propofed by M. vEpinus, in 
his Tcntaniai thnoria Eledridtalis & Magnetfvii, 
5 M Of 
