431 
ELECTRICITY. 
increafing the furface of the coated gfiafs. A battery be¬ 
ing charged, a fine metallic wire brought into the circuit 
of the fiiock will be melted.—If a plain piece of metal 
be placed upon one of the rods of the difcharger, and 
upon the other a needle with the point oppofite to the 
furface of the metal; upon difcharging the battery, the 
furface of the piece of metal will be marked with co¬ 
loured circles, occafioned by thin laminae of metal railed 
in the explofion.—If a piece of leaf gold be put between 
two pieces of glafs, and the whole faft bound together, 
the metal will be melted, and a metallic (lain will be 
feen on both glades.—If a (hock be fent through a nee¬ 
dle, it will give it magnetic polarity.—An animal, or 
plant, may be killed, by being placed in the circuit of a 
bat-tery. 
Perfons not thoroughly converfant in electricity, (hould 
be very cautious in ufing large batteries; they (hould be 
fare that they are perfeCt matters of a fmall force, before 
they meddle with a greater. Such a force of electricity 
as may be accumulated in batteries is not to be trifled 
with, (ince the confequences, if not fatal, may be great 
and lading. A large (hock, taken through the arms 
and bread, which an operator is mod in danger of receiv¬ 
ing, might poflibly injure the lungs, or fome other vital 
part : and if the fliock were taken through the head, 
which may eafiiy happen when a perfon is (looping over 
the apparatus in order to adjud it, it might affeCt his 
intellects for the remainder of life. The ingenious pro- 
felfor Richmann, of the imperial academy of St. Peterf- 
burgh, was thus indantaneoufly killed by an accidental 
ftroke from his large eledtrical battery. 
XXI. If the circuit be interrupted, the eledtric fluid 
will become vifible ; and where it paffes, it will leave an 
impreffion upon any intermediate body..—Let the fluid 
pafs through a chain, or through any metallic bodies 
placed at fmall didances from each other; the fluid, in a 
dark room, will be vifible between the links of the chain, 
or between the metallic bodies. 
If the circuit be interrupted by feveral folds of paper, 
a perforation will be made through it, and each of the 
leaves will be protruded by the ftroke from the middle 
towards the outward leaves. Let a card be placed un¬ 
der wires which form the circuit, where the circuit is 
interrupted for the (pace of an inch : the card will be 
difcoloured. If one of the wires be placed under the 
card, and the other above it, the direction of the fluid 
may be leen.—Spirits of wine, or gunpowder, being made 
part of the circuit, maybe fired.—1 nflamqiable air may 
alfo be fired by an eleCtric gun. Many ingenious expe¬ 
riments of this kind have been lately made by von Hauch, 
inventor of the balance difcharging electrometer. “ We 
fee, by fuch experiments, (fays this philofopher,) the 
wonderful advances which have been made in the fcience 
of electricity within the lad forty years, from the time of 
the invention of Haufen’s glafs globes, to the ereCtion of 
the eleCtrical machine now in theTeylerian mufeum at Ha- 
erlem. The former was fcarcely fufficient to attradl the 
lighted bodies ; whereas the latter approaches near to 
nature in its drength, in its awful and wonderful effedts; 
and feems to favour the poffibility of the idea, that there are 
natural powers capable of impelling heavy bodies with 
prodigious force; and which, connedfed by the hand of 
cultivated and enlightened man, may, fome centuries 
hence, banifh the ufe of gunpowder, as the latter, a few 
centuries ago, banifhed the ufe of bows and arrows.” 
XXII. The atmofphere is electrified, fometimes poji- 
tively, and fometimes negative .—Let a kite be fent up 
into the air with cord confiding oTcopper thread twifted 
with twine ; let the lower end of the cord be infulated 
by a (ilk line : a metallic condudtor fufpended from the 
lower end of the cord will be politively or negatively 
eledtrified. The air at fome didance from houfes, trees, 
mads of (hips, See. is generally eledtrified pofitively ; par¬ 
ticularly in frofly, clear, and foggy, weather. 
The following general laws have been deduced by Mr, 
Cavallo, from a great number of experiments made during 
two years in alrnod every degree of the atmofphere, from 
15° to 8o° of Fahrenheit’s thermometer : 1. The air ap¬ 
pears to be eledtrified at all times ; its eledtricity is con- 
dantly pofitive, and much dronger in frofly than in warm 
weather; but it is by no means lefs in the night than in 
the day-time. 2. The prefence of the clouds generally 
leflens the eledtricity of the kite. 3. When it rains, the 
electricity of the kite is generally negative, and very fel- 
dom pofitive. 4. The aurora borealis feems not to affedt 
the eledtricity of the kite. 5. The electrical fpark, taken 
from the flring of the kite, or from any infulated conduc¬ 
tor connected with it, efpecially if it docs not rain, is very 
feldom longer than a quarter of an inch, but it is exceed¬ 
ingly pungent. When the index of the eledtrometer is 
not higher than 20°, the perfon that takes fpark will feel 
the effedt of it in his legs; it appearing more like the 
difeharge of an eledtric jar, than the fpark taken from a 
prime condudtor. 6. The eledtricity of the kite is in 
general dronger or weaker, according as the flring is 
longer or (liorter; but it does nod keep any exact pro¬ 
portion to it. The eledtricity, for indance, brought down 
by a firing of a hundred yards, may raife the index of the 
eledtrometer to 20°, when, with double that length of 
that firing, the index of the electrometer will not go 
higher than 25 0 . 7. When the weather is damp, and tlie 
eledtricity is pretty ftrong, the index of the eledtrometer, 
after taking a fpark from the firing, or prefenting the 
knob of a coated phial to it, rifes furprifingly quick to 
its ufual plage, but in dry and warm weather it rifes ex¬ 
ceedingly (low. 
XXIII. The eledtric fluid and lightning are the fame 
fubdance : their properties and effedts are condantly ob- 
ferved to be the fame.—Flafhes of lightning are gene¬ 
rally feen to form irregular lines in the air; the eiedtric 
fpark, when ftrong, has the fame appearance. Lightning 
(trikes the higheft and mod pointed objedts; feizes in 
its courfe the bed condudtors; fets fire to bodies; dif- 
folves metals ; rends to pieces fome bodies ;' deftroys ani¬ 
mal life ; in all which it agrees (as has been (hewn) with 
the phenomena of eledtric fluid : both caufes have the 
fame power of making iron magnetic. Lightning has 
been known to (trike men with blindnefs. Dr. Franklin 
produced a fimilar effedt on a pigeon by the eledtrical 
fluid. Ladly, the lightning being brought from the 
clouds to an eledtrical apparatus, by a kite or wire, will 
exhibit all the appearances of the eledtric fluid. 
Take a Leyden phial, five inches in diameter, and thir¬ 
teen inches in height; on the infide let the coating rife 
till its upper edge be two inches and a half from the 
rim of the veffel ; on the outfide let the coating rife no> 
higher than one inch from the bottom. .Wlien the phial 
is thus coated, let it be charged, and a fpark will pafs 
from the tin-foil on the outfide to that on the inlide ; 
but its form will refemble that of a tree, whofe trunk, 
will increafe in magnitude and brilliancy, and conie- 
quently in power, as it approaches the edge, owing to 
ramifications which it collects from all parts of the glafs. 
Within two inches of the edge, it becomes one body, or 
ftream, and along that interval its greateft force acts.—• 
When two clouds, or the two correfpondent parts of a 
cloud, have their equilibrium reflored by a difeharge, 
the appearances are exadtly fimilar to thofe of the pre¬ 
ceding experiment. Each extremity of the flafli is formed 
by a multitude of little dreams, which gather into one 
body, whofe power is undivided in that interval only 
which feparates the pofitive from the negative. 
XXIV. Buildings may be fecured from the effects of 
lightning, by projecting a pointed iron rod higher than 
any part of the building, and continuing it, without inter¬ 
ruption, to the ground, or the neared water.—The elec¬ 
tric fluid will, by means of the pointed rod, be gradually 
conveyed from the cloud to the earth by a continued 
dream, and thus prevent the effeCts of a fudden and vio¬ 
lent explolion. 
Let 
