536

GALVANISM.

a\l good conductors of electricity ; for if the fluid were much con-densed at one extremity of the battery, and much rarefied at theother extremity, the condensation would soon be made throughthe pile itself. Indeed, it is difficult to comprehend how thiscompensation does not take place m all cases. Having mentionedabove, that the chargeof a battery mav be communicated to a com-mon electrical battery, it is almost superfluous to observe, that thesame may be communicated to a condenser, or to-a multiplier,and from it to the electrometer. If the battery consist ot twohundred repetitions, the electrometer will be affected- by thesimple contact. The spark, or the discharge of a Galvanic bat-tery, when sent through thin inflammable bodies that.are in con-tact with common or oxygen air, sets them on lire, and consumesthem with wonderful activity. It fires gunpowder, hydrogengas, phosphorus, and other combustibles; it renders red-hot,fuses, and consumes very slender metallic wires and metallicleaves. 'I he mode ot applying the power of the batteryfor such purposes is shewn in lie. 21, where AB represents a pow-t-rlul Galvanic battery; A CD I is a wire which communicateswith the last plate of the batterv at A; BKIHG is another wirewhich communicates with the last plate at B. DE, III, are twoglass-tubes, through which those wires pass, and into which tinw-are fastened sufficiently steady. 1 hose tubes serve to move thewires by ; lor il the operator applies his lingers lo the middlemostparts of those tubes, lie may move the wire, wherever he pleases,without the tear of receiving a shock. If the two extremities F,G, are brought sufficiently near to each other, the spark w ill beseen between them. It is between those extremities that the com-bustible substances, or metallic leaf, &:c. is to be placed, in orderto be fired or consumed. This figure represents, the situation ofthe w ires in the act of inflaming gunpowder. A battery consistingof two hundred pairs ot metallic plates (viz. copper and zinc, eachfive inches square) melted twenty-three inches of very line ironwire. A platina-wire about T ^ T inch in diameter, was melted intoa globule. Fig. 24 is the representation of a compound battery ofthe same kind, fastened together with the conductors a, l>, c. Amore convenient method is, lo fasten the wires to the ends of theuniversal dischargers F, and F, fig. 25, and placing the substancesbetween the points ST on the table 1IG ; also to the ends STmay be adapted spring-sockets for receiving bits of charcoal, orwires of difl’ertnt sorts, &c. \\ hen charcoal is to be deflagrated it

must be prepared with great care from boxwood, lignum vit;e, orbeech, small bits may lutve the outside taken off, and he pulamong sand in a crucible, and heated till the wood be chared, ftis best to let it remain in the sand till it is wanted for use, when apiece may be lixed to each rod of the discharger connected with thebattery. When the contact is made, a most brilliant deflagrationtakes place, and may be continued a considerable time, by movingthe charcoal as it burns. When oils, alcohol, &c. are to be in-flamed, it is best to cover thin metallic substances or charcoal withthem. Under the exhausted receiver of the air-pump, the Gal-vanic battery acts less powerfully than in the open air; but inoxygen air it acts with increased power. The flash of light whichappears before the eye of the experimenter, when the eye itself,or some other part not very remote from it, is put in the circuit ofa Galvanic combination, does not appear much greater when abattery is employed than when two plates are employed in themanner which has been already mentioned ; but when the battervis used, the sensation of a flash maybe produced in various ways.If one hand or both be placed in perfect contact with one extre-mity of the battery, and almost any part of the face brought intocontact with the other extremity of the battery, the flash will ap-pear very distinctly ; the experimenter being in the dark, or keep-ing his eyes shut. This flash appears very strong, when a wirewhich proceeds from one extremity of the battery is held betweenthe teeth, and rests upon the tongue, whilst the other wire is heldin the hand. In this case the lips and the. tongue are convulsed,the flash appears before the eyes, and a very pungent taste is per-ceived in the mouth. If any part of the human body, formingpart of the circuit of a Galvanic battery, be kept some time inthat situation, the irritation or numbness is more or less distinct,and more or less painful, according to the sen-ability of the partsconcerned. This application is likely to prove most .useful as a■remedy in various disorders. It is said that it has already provedbeneficial in deafnesses and in rheumatisms. It highly deserves to

be tried by medical persons. The most extraordinary plucnomeniiof a Galvanic battery are the chemical edicts and the modifica-tions which are produced by it upon the bodies concerned, orupon such as are placed in tiie circuit, some of which we shall hereexhibit. AB, iig. 22, represents a glass-tube, full of distilled wa-ter, and-having a cork at each extremity. EF is a brass or cop-per wire, which proceeds from one extremity of a Galvanic bat-tery, and, passing through the cork A, projects within the lube. IlGis a similar wire, whieli proceeds from the other extremity of thebattery, and comes with its extremity G within the distance of aboutail inch or two from the wire F. In this situation of things, you willfind that bubbles of gas proceed in a constant stream from the sixface G of the wire which proceeds from the negative end of thebattery ; theSe bubbles of gas, ascending to the upper part of thetube, accumulate by degrees. This gas is pure hydrogen, andmay be inflamed. At the same time the other wir l' 1 di posits anoxide in the torm of a sin. am or cloud, which gradual!) accumu-lates in a greenish form in the water, or on the i-.ies of tiie tube,and is a perfect oxide of the brass. The w ire F is readily disco-loured and corroded. If you interrupt the circuit, the productionof gas and of oxide ceases in;mediately. Complete ihe circuit,and tiie production of.gu.-. re-appears. 'Ibis production ol gas nmyhe observed even where the battery consists of not mme than sixor eight repetitions of silver, zinc, and water. In short, it thepower of the battery he sutli'ient to oxidate one of the wires ofcommunication, the other wire will afford hydrogen ga. ; bothextremities ot the wires b -mg in water. In tills experiment itseems that the hydrogen is separated from the water, and is con-verted into a gaseous slate by the wire connected witli the nega-tive extremity ol the baiter) ; whilst the oxygen unites with andoxidates the wire connected with the positive end of the battery-If you connect the positive end of the battery with the lower wireof the tube, and the negative witli the upper, then the hydrogen^proceeds from the upper wire, and the lower wire is oxidated. Iftwo w ires of gold or platinum are med, which are not oxidable;then the stream of gas issues from each, the water is diminished,and the collected gas is found to be a mixture of hydrogen andoxygen. It explodes violently. A little hole must be made intiie lower cork B, to let out the water as the gas evolves. A moresuitable apparatus for these experiments, is shewn in lig. 23. AB isa glass-cup, having two platina-wircs. IT and F, c, passing throughtwo perforations in the bottom of die vessel AB; this vessel ispartly filled with water, and there is introduced tiie tube D, doseut the top, and filled with water, in some other vessel from whichit is transterred, with the mouth downward, by means of a small cupcontaining water ; this is then put over the wires z and fin the vesselAB, and die whole put on the stand GUI, which has a glass-topGil, made to receive AB, and having two note-lies at m, and n toreceive the wires F z and Ec. These wires being connected witlithe two ends of the battery, the gas will be given out by the wires,and collected in the tube D ; it a tube be placed over each, the-gases will be obtained separately. Or vessels may be suspendedover a cup ot water, they being filled with water. See lig. 27-in all the batteries ot the first order, when the connection is completed, changes take place, which denote tiie evolution of influ-ences capable of producing from common water oxygen and hy-drogen, acid and alkali, in different parts of the body. Thus mtiie battery with a scries of. zinc-plates, silver-wires, and commonwater, oxide of zinc is formed on all the plates ot zinc, whilst hy-drogen is produced from the silver-wires; and if the water in con-tact with them be tinged with red cabbage-juice, it becomes green-And in the battery with silver, gold, and weak nitric acid, the sil-ver is dissolved, whilst the acid becomes given, and slowly evolve*gas at it- points of contact with the gold. The chemical agenciesexerted in the compound batteries of the first order can be bestobserved by the substitution of single metallic w ires lor some otthe plates ; for, in this case, the changes taking place in Ihe st "ries witli wires, will be exactly analogous to those produced n m. 0series with plates; silver, and all the more ox'idalde metals, oxi-dating in water, in the usual place, and gold and platina evolvingoxygen gas. Thus, when into two small glass tubes, connects'by a moist animal substance, and filled with distilled water, 1"°gold wires are introduced from a large battery in the proper order*oxygen is produced in one quantity ot water, and hydrogen in 1 I**"other, nearly in the proportions in which they are required <-