GALVANISM.
when they are first completed or filled with the llukl; and it de-clines in proportion as the metal is oxidated, or the liuid loses itspower. Hence, after a certain lime, not only the fluid must bechanged, but the metallic pieces must be cleaned by removingthe oxidated surface ; which is done either by filing or by rubbingthem with sand or sand-paper, or by immersing them for a shorttime iu diluted muriatic acid, and then wiping them with a coarsecloth. The metallic pieces of the battery, fig. 19, may be cleanedthe last method, and may be wiped by introducing a stickwith a rag into the cells. When experiments are to be made allthe cells of the trough must be filled, within about half an inch ofthe top, with a liquid, composed of water, witli about one twenty-fifth part of the muriatic or the nitric acid. The plates of thetrough are shorter than the depth of the trough, by about three-fourths of an inch; so that the trough may be leaned on one side|n the filling, for the purpose of letting the liquid rim equally>nto all the cells. If a number of troughs are to be connectedtogether, the communication must he made by pieces of metal,which are inserted into the liquid of one cell of each trough, asrepresented in fig. 24, at a, b, c. In making the connection, it isto be observed, that the zinc-surface of one trough must corres-pond with the copper one of another, and the zinc of the latterwith copper of a third, and so on, for the connecting metals arcsof strong wire answer very well. After all the troughs are con-tiected together, let the two unconnected ends, at which the ex-periments are to be made, be as near together as possible.A connection being now formed between the two ends, one°f which we shall term the zinc-end, and the other the cop-per-end, the united energy' of the whole will be transmittedthrough the connecting medium. We may now proceed tonotice some of the more striking effects of these combinations.The chemical action of bodies upon each other is increased by theGal vanic arrangement so much, that some of them are by thatCleans enabled to act upon bodies that otherwise they would haveno action upon. Fig. 3, represents a glass-tube about four inchesJong. Two corks are thrust into its apertures A and B. An ob-long piece of zinc, CD, is fixed into one of the corks, and is madef° project within and without the tube. EFG is a silver wire,ydiich being fixed into the other cork, projects with the extremityF, within the tube; and its other extremity is bent so as to come"ear the projecting part of the zinc C. Kemove one of thoseooeks, and fill the tube with water, in which you must mix adrop or two of muriatic acid ; then replace the cork, and you willn*id that the zinc is acted upon by the diluted acid, is oxidated“>• it, and bubbles of gas are evolved from it; but the silver wireF remains untouched, and no gas whatever is evolved from it.Aow, if you bend the silver wire, FG, so that i‘s end G maytnuch the zinc at C, then the Galvantic circle of silver, zinc, anddiluted acid is completed, in consequence of which the diluted® c "ul is enabled to act stronger upon the zinc D. which is mani-Jested by the more copious evolution of sras, and is besides ena-bled to act upon the silver wire; for now you will observe the® v oIu(ion of gas from the silver E also. Break the contact l>e-‘Wecn G and C, and the silver E will cease to yield gas. Form ita §ain, and gas will again proceed from the silver. Instead of sil-Ver > zinc^and diluted muriatic acid, you may in the same man-*'. er use gold, tin, ami diluted nitric acid ; and by completing thec jrcle, the acid will be enabled to act upon the gold. It has beenobserved, that whenever an oxidating influence is exerted atoneI die places of contact of the perfect and imperfect conductors, aIJfoxidating action appears to be produced at the other place,thus when iron, which oxidates rapidly when tormina a circle"’ith silver and common water, is arranged with zinc ami common"’•'ter, it remains perfectly unaltered, whilst the zinc is rapidlyat ted upon. Fig. 2, represents a more convenient method of per-Jtfniing this experiment. The muscular parts ot animals recently<le ad, and making part of the circuit, will be convulsed as aboveescribed. The effects thus produced by a single galvanic circle,e come abundantly more striking and interesting from the properCombination of several that is from the action of the Galvanic bat-er y . The battery not only convulses the prepared limbs of aJJ°8> or produces the appearances of a Hash of light before the hu-man eye ; but it shews all the phenomena of electricity in a veryconsiderable degree. It gives the shock ; it affects the electrome-® r ; shews a luminous spark, accompanied with an audible report;
it burns metallic and oilier combustible bodies; and continues inaction for a very long time, viz. until the chemical action be-tween the component parts of the battery is quite exhainled.The following contain a more particular, yet concise, enumerationof those wonderful effects. When the Galvanic battery of the firstorder consists of twenty repetitions of simple combinations, ,f yontouch with one hand one extremity of the battery, as at b, in anyone of the above described batteries (see figs. 17, 18, 19), andapply your other hand to the other extremity of the battery, as ata, you will feel a very slight shock, like that which is communi-cated by a Leyden phial weakly charged, and it will be hardlyfelt beyond the fingers, or at most the wrists. This shock is feltas often as you renew the contact. If you continue the hands in-contact with the extremities b and a, you will perceive a slight butcontinued irritation; and, when the hand or other part of thebody, which touches the extremity of the battery, is excoriated orwounded, this sensation is disagreeable, and rather painful. Thedry skin of the human body is seldom capable of conducting thisshock; therefore the touching finger should be well moistenedwith water, or salt and water. It will be better to immerse a wirethat proceeds from one extremity of the battery, in a bason, ofwater, wherein you may plunge one of your hands ; then graspingwith your other hand well moistened a large piece of metal,, for.instance, a large silver spoon, touch the other end oi the batterywith it, and the shock will be felt more distinctly. By this meansthe shock lias been felt when the battery consisted of less thantwenty repetitions. Instead of one person, several persons mayjoin hands (which must be well moistened with, water,) and oncompleting the circuit, they will all feel the shock at the same in-stant. But the strength of the shock is much diminished by itspassing through the several persons, or, in general, by passingthrough less perfect conductors. The shock from a battery con-sisting of fifty or sixty repetitions of the most aedve combinationsof the first order may be felt as far as the elbows; and the com-bined force of five or six such batteries will give a shock perhapsmuch stronger than most men would be willing to receive. The-prepared limbs of a frog or other animal are violently convulsed,,but soon exhausted of their irritability by' the action of a Galvanic battery. This shock is similar to that of a large common electri-cal battery weakly charged, and not to that of a small Leyden phialfully discharged. The difierence consists iir this, viz. that thelatter contains a small quantity of electric fluid highly condensed ;;hence its discharge will force its wav through perhaps an inch of airwhereas the former contains a vast quantity of electricity, but littlecondensed ; hence its spark, viz. its course through the air, is sovery short, that the fingers must be brought almost into perfectcontact in order to receive the shock ; and such is the case with theGalvanic battery ; for the shock from a very powerful battery ofthis sort will hardly ever force its way through the air, when theextremities of the circle of communication are more than the forticlh of an inch distant, even when those extremities consist of per-fect conductors. In this case a small, but very vivid, spark isseen at that extremity, accompanied with an audible, but notstrong, leport. There is no perceptible difference of appearance-between the spark of the positive and that of the negative end ofthe battery. The first effect of the shock, seems to be proportionalto the number of plates nearly, without regard to their size. Thusif the number of plates be the same, the first perceptible action isnearly the same, though the plates of the one battery be several,times huger than the other; but, in the latter case,, the effect iscontinued with less interruption, as the plates are larger, till atlength a constant tremor is produced. If a wire, proceeding fromone extremity of a pretty strong battery, be made to communi-cate with the inside coating, and a wire, which proceeds from theother extremity of the battery, be made to communicate with the-outside coating of a common large jar or electrical battery; thelatter will become weakly, but almost instantaneously,, charged,,m the same manner as if it bad been charged by a few turns of acommon electrical machine; and with that charge you may eithergive the shock or affect the electrometer, &c. From tins andseveral other experiments it appears- that a Galvanic batteryproduces a vast quantity of electric fluid, but which is littlecondensed; and indeed it cannot be supposed that the elec-tric fluid could proceed in a very condensed state from an ar-rangement of bodies, which, whether more or less, are, however,.
alii