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5, 1798, at the age of sixty, amid the tears Simon Volta with much labour and inof his friends and the public regret.
genuity successfully opposed the hypothesis GALVANISM, this surprizing branch of of Galvani. He had recourse to those valaphilosophy has been denominated galva- able experiments made by Bennet, by nism, from Galvani, an Italian professor, which to explain the phenomena observed whose experiments led to its discovery. by Galvani. Bennet had some time be
In 1789, some time before he made the fore observed, when plates of different most important discovery, he was by ac metals were brought in contact, that one cident led to the fact, of electricity having of the metals transmitted a portion of its the property of exciting contractions in the electricity to the other, each of which, muscles of animals. Stimulated by the then when separated, being at the same time prevailing idea of electricity being • prin insulated, evinced signs of contrary states ciple inherent in animals, which acting upon of electricity. When the plates, for inthe muscular susceptibility, was the imme- stance, were one of copper and the other 'diate cause of muscular motion, he was in- zinc; the former, while the two were in duced to persevere in the inquiry, during contact, gave a portion of its electricity to the prosecution of which, he brought to light the latter. Hence, when they were sepaother facts, which laid the foundation of rated, and thus presented to the electromethis valuable scientific acquisition.
ter, the copper exhibited signs of negative After having observed that common elec- electricity, and the zinc that of positive. tricity, even that of lightening, produced On this ground it was that Volta objected vivid convulsions in the limbs of recently to the hypothesis of Galvani, and establishkilled animals, he ascertained that metallic ,ed the more plausible idea, that the elecsubstances, by mere contact,under particular tricity was furnished by the disturbance circumstances, excited similar commotions. of that fluid, arising from the covtact of the
He found, that it was essential, that the different metals, and that the convulsions forces of metals employed should be of were excited by the stimulating effect of different kinds. He applied one piece of that active agent. It was in the investiga. metal to the nerve of the part, and the other tion of this experiment, that this truly into the muscle, and afterwards connected genious philosopher was led to the discovery the metals, either by bringing them toge. of the pile, which from its inventor has been ther, or by connecting them by an arch of called the Voltaic pile. This apparatus a metallic substance; every time this con consisted, in combining the effects of a numnection was formed the convulsions took ber of pairs of the different metals, and by place. The diversity in the metals employ. that means constituting a battery in galed in these experiments appeared, in the very vanism, similar in effect to the Leyden early stages of this enquiry, to be connected vial in common electricity. with their respective degrees of oxydability, As silver and zinc had been found in the the one being possessed of tbat property minor experiments to produce the greatest in a great degree, and the other little liable effect, these metals were employed by Volta to the change. Hence zinc, and silver, or in the construction of his battery. The gold; was found to produce the greatest silver plates generally consisted of coins ; muscular contractions.
and the zinc plates were of the same size, The experiments of Galvani were con being frequently cast in moulds made with firmed by many able philosophers, by whom the silver. The same number of pieces of they were repeated. Those who particu- cloth, pasteboard, or leather, of the same larly distinguished themselves by their la- size, and steeped in solution of common salt, bours on the subject were Valli, Volta, Drs. were also provided. The above substances Monro and Fowler.
were formed into a pile, in the following Galvani had theorised upon the phenome- order : zinc, silver, wet cloth; zinc, silver, na which he had observed to a considerable wet cloth; and so on, in the same order, till extent. He conceived, that the convulsions the pile became sufficiently high. If it were produced by a disturbance of the elec were to be elevated to any considerable tricity inherent in animals, which was iden. height, it was usual to support it on the tical with the nervous fluid, and that the sides with three pillars of glass, or varnished metallic substances employed bad not any wood. other effect, than that of transmitting the The pile, thus formed, was found to electricity from the nerve to the muscles unite the effects of as many pairs of plates producing the contractions in question. as might be employed. Previously to
this no otler effect had been produced When bringing the wire from the bottom of than what resulted from the energy of a the pile, in contact with a drop of water at single pair of plates. A pile of 50 pairs of the top, they observed the disengagement plates, with as many corresponding pieces of some gaseous substance, which had the of wet cloth, was found to give a pretty smell of hydrogen. Supposing this effect smart shock, similar to an electric shock, to arise from the decomposition of the waevery time that a communication was made ter, they caused the ends of two brass between the top and bottom of the pile. wires, coming from the two ends of the It was found, however, that little or no pile, to be immersed in water, so that a shock was perceived, when the hands, or portion of that liquid might be exposed beother parts applied, were not previously tween the wires. A disengagement of gas moistened. It was also observed, that the immediately took place from one of the effect was increased when a larger surface wires, while the other became as quickly was exposed to the action of the pile. If tarnished, and oxydated. The former apthe communication were made by touching pearance took place at the silver end of the the pile with the tip of each finger merely, pile, the latter at the zinc end. They asthe effect was not perceived beyond the certained that the effect would not take joint of the knuckle; but if a spoon, or other place when the wires were placed far asın. metallic substance, were grasped in inois- der, and that the effect diminished gradually tened hands, the effect was felt up to the with the distance. They observed also, that shoulder. If the communication be formed when the tincture of litmus was used, instead between any part of the face, particularly of water, the liquid in the vicinity of near the eyes, and another part of the body, the oxydated wire, being that connected a vivid flash of light is perceived before the with the zinc end, became red. When eyes, corresponding with the shock. This they made use of wire of platina instead of phenomenon may be more faintly observed, brass, they observed that the wire from the by placing a piece of silver, as a shilling, be. zinc end of the pile, which when of brass tween the upper lip and the gum, and laying became oxydated, vow gave out bubbles a piece of zinc at the same time upon the of gas, which they found to be oxygen. tongue: upon bringing the two metals in In short, they determined that the gases contact, a faint flash of light is perceived. evolved were oxygen and hydrogen, and in It is singular, that this light is equally vivid proportions fit to constitute water. These in the dark with the strongest light, and discoveries established the chemical nature whether the eyes be shut or open.
of the galvanic action in England; and they Another variety of galvanic battery was soon spread over all Enrope, also contrived by Volta. The pairs of The above experiments were repeated plates were soldered to each end of a bit
by Mr. Cruickshauk, of Woolwich. He of wire, which was afterwards went into an employed a glass tube filled with water, arch, so that the plates became parallel to having a cork at each end, through which each other. A number of glass cups were wires of silver were passed, the points of also provided, and filled with a solution of which were separated from each other by culinary salt. The glasses being arranged a stratum of the liquid. Upon the wires side by side, the metallic arcs were so being communicated with the two ends of placed, that the silver plate was immersed the piles, the same appearauces took place in one glass, and the zinc in another; and which were observed by Messrs. Nicholson also that a silver and zinc plate of different and Carlisle: the silver wire, however, conares should be placed in each glass. This nected with the zinc-end of the pile, bearrangement was found to be similar to the came oxydated, the oxide forming a white pile, the water in the cups being substituted cloud round the wire: he also, instead of for the disks of cloth.
water, introduced into the tube an intusion Soon after the discovery of the pile, in' of Brazil-wood. During the galvanic ac1800, it was communicated by Volta him tion, the colour in the vicinity of the wire self to the Royal Society, London. The first of the zinc-end, became very pale', while experiments made in this country upon the
that about the wire of the silver-end of the Voltaic pile, were made jointly by Messrs. pile, appeared of a purple colour. When a Nicholson and Carlisle. After observing the metallic solution was placed in the tube, phenomena already described by Volta, they Mr. Cruickshank observed, that, instead of observed an important fact which had es. hydrogen gas being evolved from the wire, caped the notice of that acute philosopher, which connected the silver- end of the pile,
as in the former experiments, the metal be which he succeeded in decomposing the sulcame revived.
phuric and the nitric acids, and ammonia. He next caused the galvanic current to Mr. Davy, professor of chemistry at the pass through solutions of the muriates of Royal Institution, made a number of expelime and soda. In these experiments, he riments, the most particular of which were found the oxygen evolved from the wire of those, in which he ascertained, that the disthe zinc-end very deficient, and a smell of similarity of metals was not absolately esoxy-muriate produced. When gold wires sential to the galvanic process. He sucwere employed, the gold was dissolved by ceeded first in exciting this energy by the oxy-muriatic acid. Aqua ammoniæ be. means of one metal, the two sides of which ing operated upon in a similar way, both were separated from each other. An oxythe water and the alkali underwent decom- dating liquid, such as an acid, was placed position, producing the gases of hydrogen, on one side of the plate, and a liquid havnitrogen, and oxygen.
ing a contrary effect on the other. He afterIt is to the ingenious author of the above wards produced an effect thongh more faintexperiments, that we are indebted for the ly, by treating plates of charcoal in a similar invention of the galvanic trough, a disco. way. Hence it would appear, from these very which very soon superseded the use of results, that the dissimilarity of the metals the pile, as being more mauageable, and at. was only necessary to the furnishing two tended with less trouble to the operator. surfaces of different degrees of oxydability. It consists of a wooden box, or trough, the Hitherto it was not generally admitted, depth and breadth of which corresponds that the fluids of galvanism, and electricity, with the size of the plates. It is of such a were identical. Dr. Wollaston made a length, in general, as to contain tifty plates, number of experiments, which seem to have allowing a space of about three-eighths of completely settled this point. He succeed. an inch, between each pair of plates. The ed in decomposing water, by means of a spaces between the plates are formed by current from the common electric machine. grooves, which are to receive the plates.The This effect, which had been performed with plates are first soldered together in pairs, so much facility with the galvanic apparatus, one of copper or silver, and one of zinc.
was previously not known to be able to be The trough being lined with a cement, produced by common electricity, and had formed of bees'-wax and resin, the plates, bitherto appeared the most striking differwhich are previously warmed, are pressed ence between the two principles, into the grooves, in such order, that the zinc
This ingenious experimentalist, made a side of each compound-plate may face one number of other experiments, tending to way, and the copper or silver the other. throw much light on the means of ex
It will be easily perceived, that there is citing and appreciating galvanic phenome. the strictest analogy between the trough na. He immersed each extremity of a and the pile, in point of arrangement. See piece of zinc and silver in dilute muriatic fig. 1.
or sulphuric acid. The zinc, as would be The pair of plates of zinc and silver, expected, immediately caused the disenwhich, in the pile, are simply laid upon gagement of hydrogen gas, while no apeach other, are, in the trough, soldered to pearance took place upon the silver. As gether, and cemented into the grooves; and soon, however, as the two metals were the cavity or cells formed by the spaces be- made to touch each other at the opposite tween each pair of plates, in the trough, be- extremities, bubbles of hydrogen were coing filled with a solution of salt or other ap- piously given out by the silver wire. Any propriate liquid, stands in the stead of the other metal, capable of being acted upon pieces of moistened cloth, between the by the acid, being substituted for the zinc, plates of the pile.
produced with the silver a similar effect. Several powerful troughs were soon after When gold was employed with silver, iron, constructed, the effects of which were or copper, in the dilute nitric acid, the same strikingly evinced in producing other phe effect was produced; the gold being the nomenon, not as yet observed. Very small same with the silver in the first experiwires and foils of metal being exposed in ment. their circuit, were deflagrated with great He made similar experiments, using me. brilliancy.
tallic solutions instead of the dilute acid. A number of galvanic experiments were Instead, however, of silver or gold giving made by Dr. Henry, of Manchester, in out hydrogen gas, on the contact being