534

GALVANISM.

between the zinc and the gold ; the activity of the circle will notbe altered. Hence it appears that the action of a Galvanic circlemay be conveyed through extraneous conductors to a considerabledistance; but it must be observed, that the activity is weakenedby the great length of the conductors, especially it they are of animperfect nature. 4. When the three bodies which tonu a Gal-vanic circle of the first order are laid one upon the other, but thelower and the upper one do not touch each other; thenthese two extremes are in opposite electric states, viz. the extre-mity which is next to that metallic surface that touches the bodyof the second class, is positive, and the opposite extremity is nega-tive. Thus let copper, zinc, and moistened leather, be laid oneupon the other, as in fig. 12, and the upper end \V, viz. the w ettedleather, will be found possessed of positive electricity ; whilst thelower end C, or the copper, will be found negative. 5. 'Hie Gal-vanic effects may be increased to almost any degree, by connect-ing several of the above-mentioned active combinations, or by arepetition of the same simple Galvanic combination (.the most ac-tive simple combinations forming the most powerful batteries,and vice versa) provided the simple combinations are disposed soas not to counteract each other. Those batteries are said to be ofthe first or of the second order, according as the simple combina-tions, of which they consist, are of the first or of the second order.Thus, if a piece of zinc is laid upon a piece of copper, and a pieceof moistened card upon the zinc; then a similar arrangement ofthree other such pieces laid upon them, and a third arrangementupon this, &c. all in the same order; the w hole will form a batteryof the first order. But if the arrangement be made by connecting apiece of copper with a piece of cloth moistened with water ; the latter with a piece of cloth moistened with a solution of sulphurate ofpotass, and this again with another piece of copper, &c. the wholewill form a battery of the second order. The above-mentionedrestriction, viz. that the parts of a battery must not counteracteacii other, will be easily understood by considering that everysimple, but interrupted Galvanic combination, lias a positive anda negative end; or that in every complete Galvanic circle, theelectric fluid circulates in one way only. Thus, if two simplecombinations are disposed as in tig. 14, this arrangement will nothave any Galvanic power, because the actions of the two simplecombinations, or the two currents of electricity, are opposed toeach other; the two positive ends being called p, and the two ne-gative ends n. But if those fixed bodies are disposed as in fig. 15,then the combination will be very active; because, according tothe hypothesis, the direction of the electric 11 uid in each simplearrangement tends the same way, and probably the one acceleratesthe other. \\ hat has been said above of the arrangement of twosimple Galvanic combinations, must be likewise understood tohold good with respect to the connection of any number of thesame ; viz. that they must not counteract each other; or if a cer-tain number of them counteract each other, then the remainingonly form the active part of the battery. For instance, if a batteryconsists of 40 simple combinations, and if 12 of them are placedin a direction contrary to the others; then these 12 will counter-act 12 others, and of course the whole battery will have no morepow er than if it consisted of l(i simple combinations properly dis-posed. 'I bis points out a method of comparing tire powers oftwo batteries; for if those batteries are connected in an invertedorder, viz. the positive end of one to touch lire negative end of theother; then, on connecting the two other extremities, or on ap-plying them to proper instruments, the whole power will be anni-hilated, it the separate batteries had equal power ; otherwise thepower of the whole will be the excess of the power of the mostpowerful battery above that of the weakest; and the direction, viz.its being positive or negative, will shew to which battery it be-longs. It must be observed, with respect to the inactive arrange-ment of fig. 14, that if one of the separate bodies Z, is removed,then the remaining five bodies will form an active combination ;for in that case, AV, W, become one body, and S, S, likewise actas one body. It is almost superfluous to observe, that (as hasbeen said with respect to simple circles) in a Galvanic battery theinterposition of conductors that Itave no particular action, or ofthe conductors of the same class as 'the adjoining bodies, does notalter the effect of the battery. These simple arrangements beingwell understood, the effect of uniting two or more simple Gal-anic circles, it will be easy to construct the battery several ways.

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We sliall here describe the two methods first used and invented byVolta, fig. 16 and 17, and that of Mr. Cruiekshank now generallyemployed, fig. 19. The construction, fig. It), Volta denominates, acouronne de tasses, consisting of glass-tumblers, or china-cups,partly tilled with water, or salt and water, &c. and two plates un-connected with each other, viz. a plate ot zinc and a plate ot sil-ver, are plunged in the fluid of each cup, excepting the first andlast cups ; hut each of those plates must have a sort ol tail or pro-longation, by which they are so connected that the silver plate ofone cup communicates with the zinc-plate ot the next, and so on ;or they may he connected by some other conductor. The bat-tery, lig. 17, consists of pieces of silver, about as big as halt-crowns, pieces of zinc, of an equal size to those of silver, andpieces of card, or doth, or leather, or other bibulous substance, alittle smaller in diameter than the metallic pieces, and soaked inwater or in other proper fluid. Those pieces are disposed in theorder of silver, zinc, and wet doth, Arc. as indicated by the let-ters, S, Z, vV. The pieces of card, or doth, &c. mus’t be wellsoaked in the fluid ; but before they are applied, they should besqueezed, in order that the superfluous fluid may not run downthe outside of the pile, or insinuate itself between the contiguouspieces of silver and zinc. Those pieces, especially if soaked inplain water, lose their moisture pretty soon, so (hat they canhardly serve longer than for a day or two; after which lime the_pile must be decomposed, the imtallic pieces ( leaned, those otdoth or card soaked again, and the whole arranged as before, 'i hethree rods 11, II, H, are of glass or of baked wood ; and the pieceof wood, O, slides freely up, or down the rods. This serves toprevent the falling of the pieces. M hen such battery is to he verypowerful, viz. is to consist of numerous pieces, the best way isto lorm two or three or more piles, and to join them by pieces ofmetal, as cc in fig. IS, where two piles are joined together, sothat a is the negative extremity, and b is the other or positive ex-tremity of the whole arrangement, or of the two piles consideredas one. The battery, fig, 19, consists of a wooden box, or trough,the depth and breadth of which corresponds with the size of theplates. It is of such a length, in general, as to contain fifty plates,allowing a space of about three-eighths of an inch, between eachpair of plates. The spaces between the plates are formed bygrooves, which are to receive the plates. The plates'tire first sol-dered together in pairs, one of copper or silver, and the other otzinc, making one plate of the two. The trough being lined witha cement, formed of hees’-wax and resin, the plates which are pre-viously wanned, are pressed into the grooves, in such order, thatthe zinc-side of each compound-plate may face one way, and thecopper or silver the other. The pair of plates of zinc and silver,which, in the pile, are simply laid upon each other, are in thetrough, soldered together, and cemented into the grooves; andthe cavity or cells formed by the spaces between each pair otplates, in the trough, being filled with a solution of salt or other ap-propriate liquid, stands in the stead of the pieces of moistenedcloth, between the plates of the pile. Two or more of such bat-teries may be joined, as lias been said of the preceding battery*See fig, 24. It need hardlv he observed, that instead of zinc, cop-per, and water, other combinations may lie made according to tin 5table. At present the last-described batteries are constructed w ithcopper, zinc, and water mixed with a small proportion of nitric ofmuriatic acid. For the construction of such batteries it is minis-terial whether the metals ar<-quite pure or slightly alloyed. '1 hewood of which the trough is made should lie the olde-t and hardestmahogany that can he procured, as being less liable to warp, andit ought to lie well put together to prevent leaking. The platesshould he of copper and zinc, for though silver lie somewhat betterthan copper, it is not so in proportion to the price. The zi"'-"plates mar be cut out of sheds oi malleable zinc, and the copped,plates may lieso thin as one ounce to twenty-four square inches o>surface.They may be made a little larger than the zinc to lap overthe edge at the top, where it may more conveniently he soldered'the other edges need not be soldered, tlx y being sufficiently st !”cured bv the cement in the grooves. The length of a trougi*should lie about two feet ; they become unwieldy when large’*’After the plates arc inserted by wanning them se.llicienlly to i" c ^the cement in the grooves, and the whole is polished up, by ;l P.plying a hot iron, the parts may be varnished with copal, orcommon spirit varnish. The action of all these batteries is greats

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