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Justead, therefore, of the glass-cylinder, com ductor, conted jar; &o., used in electrical ex: periments, the Galvanie pilt, or trough, is now preferred...
Ods...The common exhibition of electrical ell'ects, is in attractions and repulsions, in which masses of matter are concerne la copilace, operate, in a manner, in small
but there are other effects, in which, the apneas of tiine imperceptibly, and in which, the etfects are produced upon the chemioal arrangements of bodies.
If a piece of zinc and a piece of copper be brought in contact with each other, they will form a weak electrical combination of which, the zinc will be positive, the copper, negative: this may be learnt by the use of a des licate condensing electrometer; or by ponring zinc-filings through holes, in a plate of copper, upon a commou electrometer, but the power of the combination may be most distinctly exhibited, 'ia the experiments, called Gal, vante experiments; by connecting the two metals, which must be la contact with each other, with a nerve and musele in the limb of an animal recently deprived of life,-a fog, for instances at the moment the contact in completed, or the circuit made, one metal touching the muscle,
the other the nerve, violent contractions of the limb will be occasioned,
543. The Galvanic apparatus consists of anarrow trough of earthenware, with grooves at cer, tain distances, into which are slid alternately, plates of king and copper; and between each division, is poured a mixture of acid and water.
If one hand be put to the plate of copper at the end of the trough, ayd another be put to the plate of zinc at the other end, a smart shock will be felt, and will be continued for a great
'16! Obs. 1.---The above represents an earthenware trough with its plates, of separation, consisting, alternately el copper and sing. A wire is fixed to each end, for the purpose of conveying the stroke to the dat plate, or for any other desired purpose.
$. -The most powerful combination that cristo, in whieh pumber of alteragtious is combined with extent of surface, is that constructed by the subscriptions of a few zealous oultivators and patrons of science, in the lado ratory of the Royal Institution. It consists of twa hans dred instruments, connected together in regular order, each composed of ten double plates, arranged in cells el porcelain, and containing in each plate thirty-two'square inches, so that the whole number of double plates is 2,000, and the whole surface 198,000 square daches, This battery, when the celle were killed with 60 parta a water mixed with one part of nitric acid, and one part of sulphuric acid, aforded a series of brilliant and in pressive effects. When pieces of chareoul, about aw ibek long and one-sixth of an inel in diameters were brought pear each other (within the thirtieth er fortieth part of an inch.) a bright spark was produced, and more thaa hall the volume of the churroni became igaited to white ness; and, by withdrawing the point from each other, a constant discharge took place through the heated ainin a space equal at least to four inches, produciuk anest brilliant ascending areh of light, broad and conical, ia form in the middlo, Wheu any substance was introduced into this arch, it instantly became ignited; platinas melted as readily in it as wax'in tlie Annie of a commaa candle: quarts, the sapphire, magnesia, lime, all entered imto fusiou ; fragments of diamond, and pojasa, of char
soal and plumbago, rapidly disappeared, and seemed to evaporate in it. Such are the decomposing powers of electricity, that not even insoluble compounds are capable of resisting their energy ; for event glass, sulphate of baryta, duor spar, &c., when inoistened and placed in contact with electrified surfaces from the Galvanic apparatus, are slowly acted upon, and the alkaline, carthy or acid matter, carried to the poles in the common order, Not even the most solid aggregates, nor the firmest compounds, are capable of resisting this mode of attack s its operation is slow, but the results are certains and sooner on later, by means of it, bodies are resolved into simpler forms of matter. -DAVY, # 544. It is ascertained, that during these shocks an oxydation of the metallic plates takes place; and, after their surfaces become tarnished, the shock diminishes; but, ou being wipéd, its force is renewed.
A combination of these troughs forms a galvanic battery, the force of which has prod&ced the most surprising effects; and, by disturbing the close affinity of the constituent parts of many hodies, has led to the analysis of substances, laitberto deemed simple and elementary,
Obs-some fishes, as the torpedo, the gymnotus elecIricus, and the silarus electricos, when touched, commuDichteshocks to, the human body like those of electri. eity rhot as there is no circuit for the Quid, in these casesc nu adequate solution has yet been found of this strange phenoinenon, Jon 6-13. Since the identity of lightning and electric matter has been ascertained, philosophers have been led to seek the explication of aërial profeurs in principles of electricity: and there is nord babt, that the greater part of them, and especially the aurora borealis, are electrical, or gaseous phenomena.
It has been observed, that the aurora borealis produces a very sensible fluctuation in the eage nelie medle; and that the flashes Imve been at tended with various rumbling and lioning sounds
Now black, and deep, the night begins to fall,
190WSON 646. Earthquakes, the most dreadful phenomena of nature, have been aneribed, by some naturalists, to water, fire, team, and electricity: cach of these powerful agents being supposed to operate in the bowels of the earth.
Subterraneous fire, and steam generated from it, are supposed to be the true causes of earth. quuken. The elasticity of steam, and its expan sive forer, are every way capable of producing the stupendous effects attributed to earthquakes; the force of steam being 20 times greater than that of gunpowder
Can the poor, brittle tenements of man Withstand the drrad eonvulstou? Their dear homeo. (With shaking, fottering, erashing. bursting, fall) l'he boldest fly i and, on the open plain, Appallid, in apoy, the moment whe, When, with disrupture vast, the waving earth Shall 'whelm them in her seadingorging women
Nov, lem offrighted, are the bestial kind :-
aHOMSON, 647. The most remarkable changes in the form and constitution of the earth, since the deluge, have probably been produced by subterraneous fires in volcanoes, and by earthquakes; by which plains are converted into mountains, the ocean into islands, and dry land into pools.
Obs. Half a pound of steel filings, half a pound of brimstone, and a pint of water, will, when well mixed, acquire heat enough to make the mass take fire: and it appears, that volcanic mountains abound in such mixtures, which are ignited, no doubt, by rain' falling into their craters, or by the aca communicating with their bases and lower cavities.
The tuid lake that works below,
Is torn with agonizing throes. At once,
MALLET. 648. The eruptions of volcanoes exhibit dreadful phenomena, in prodigious inundations of liquid fire, which bear inevitable destruction with them.
The name of lava is given to these fiery streams, consisting of a mixture of stones, sand,