People regard Charles Lamb's story of the discovery of roast pig as a most extravagant and impossible fiction; but, really, Professor Galvani comported himself very much in the manner of that great discoverer. It was no more necessary to employ the frog's nerves in the production of the electricity, than it was necessary to burn down a house in roasting pig for dinner. The poor frog contributed nothing to it but his dampness,—as every boy in a telegraph office now perceives. He was merely the wet in the small galvanic battery. Professor Galvani, however, exulting in his discovery, leaped to the conclusion that this electricity was not the same as that produced by friction. He thought he had discovered the long-sought something by which the muscles move obedient to the will. "All creatures," he wrote, "have an electricity inherent in their economy, which resides specially in the nerves, and is by the nerves communicated to the whole body. It is secreted by the brain. The interior substance of the nerves is endowed with a conducting power for this electricity, and facilitates its movement and its passage from one part of the nervous system to another; while the oily coating of these organs hinders the dissipation of the fluid, and permits its accumulation." He also thought that the muscles were the Leyden jars of the animal system, in which the electricity generated by the brain and conducted by the nerves was hoarded up for use. When a man was tired, he had merely used his electricity too fast; when he was fresh, his Leyden jars were all full.
The publication of these experiments in 1791, accompanied by Galvani's theory of animal electricity, produced a sensation in scientific circles only inferior to that caused by Franklin's demonstration of the identity of lightning with electricity, thirty years before. The murder of innocent frogs extended from the marshes of Bologna to the swamps of all Christendom. "Wherever," says a writer of the time, "frogs were to be found and two different metals could be procured, every one was anxious to see the mangled limbs of frogs brought to life in this wonderful way." Or, as Lamb says, in the dissertation upon Roast Pig: "The thing took wing, and now there was nothing to be seen but fire in every direction." At first the facts and the theory of Galvani were equally accepted; and a grateful world insisted upon styling the new science, as it was deemed, "Galvanism." Thus a word was added to all the languages, which has been found useful in its literal sense, and forcible in its figurative. Whatever we may think of Galvani's philosophy, we cannot deny that he immortalized his name. He died a few years after, fully satisfied with his theory, but having no suspicion of the many, the peculiar, the marvellous results that were to flow from the chance discovery of the fact, that a moist frog placed between two different metals was a kind of electrical machine.
Among the Italians who caught at Galvani's discovery, the most skilful and learned was Professor Volta, of Como, who had been an ardent electrician from his youth. Many of our readers have seen this year the colossal statue of that great man, which adorns his native city on the southern shore of the lake. The statue was worthily decreed, because the matt who contributes ever so little to a grand discovery in science—provided that little is essential to it—ranks among the greatest benefactors of his species. And what did the admirable Volta discover? Reducing the labors of his long life to their simplest expression, we should say that his just claim to immortality consists in this,—he found out that the frog had nothing to do with the production of electricity in Galvani's experiment, but that a wet card or rag would do as well. This discovery was the central fact of his scientific career of sixty-four years. It took all of his familiar knowledge of electricity, acquired in twenty-seven years of entire devotion to the study, to enable him to interpret Galvani's apparatus so far as to get rid of the frog; and he spent the remaining thirty-seven years of his existence in varying the experiment thus freed from that "demd, damp, moist, unpleasant body." It was a severe affliction to the followers of Galvani and to the University of Bologna to have their darling theory of the nervous electricity so rudely yet so unanswerably refuted. "I do not need your frog!" exclaimed the too impetuous Volta. "Give me two metals and a moist rag, and I will produce your animal electricity. Your frog is nothing but a moist conductor, and in this respect is not as good as a wet rag." This was a decisive fact, and it silenced all but a few of the disciples of the dead Galvani.
Volta was led to discard the frog by observing that no electric results followed when the two plates were of the same metal. Suspecting from this that the frog was merely a conductor (instead of the generator) of the electric fluid, he tried the experiment with a wet card placed between two pairs of plates, and thus discovered that the secret lay in the metals being heterogeneous. But it cost thousands of experiments to reach this result, and ten years of ceaseless thought and exertion to arrive at the invention of the "pile," which merely consists of many pairs of heterogeneous plates, each separated by a moist substance. The weight of so much metal squeezed the wet cloth dry, and this led to various contrivances for keeping it wet, resulting at last in the invention of the familiar "trough-battery," now employed in all telegraph offices and manufactories of electro-anything. Instead of Galvani's frog or Volta's wet rag, the conductor is a solution of sulphuric acid, which Volta himself suggested and employed. The negative electricity is conveyed to the earth by a wire, and the positive is conducted from pair to pair, increasing as it goes, until, if the battery is large enough, it may have the force to send a message round the world. And the current is continuous. The galvanic battery is an electrical machine that goes without turning a handle. By the galvanic battery, electricity is made subservient to man. Among other things, it sends his messages, faces his type with copper, silvers his coffee-pot, and coats the inside of his baby's silver mug with shining gold.
The old methods of covering metals with a plating of silver were so difficult and laborious, that durable ware could never have been produced by them except at an expense which would have defeated the object. In those slow and costly ways plated articles were made as late as the year 1840; and thus they might be made at the present moment, if Signora Galvani had been looking the other way when the student touched the frog with his knife. More than fifty years elapsed before that chance discovery was made available in the art we are considering. For many years the discoveries of Galvani and Volta did not appear to add much to the resources of man, though they excited his "special wonder," Elderly readers can perhaps remember the appalling accounts that used to be published, forty years ago or more, of the galvanizing of criminals after execution. In 1811, at Glasgow, a noted chemist tried the effect of a voltaic "pile" of two hundred and seventy pairs of plates upon the body of a murderer. As the various parts of the nervous system were subjected to the current, the most startling results followed. The whole body shuddered as with cold; one of the legs nearly kicked an attendant over; the chest heaved, and the lungs inhaled and exhaled. At one time, when all the power of the instrument was exerted, we are told that "every muscle of the countenance was simultaneously thrown into fearful action. Rage, horror, despair and anguish, and ghastly smiles, united their hideous expression on the murderer's face, surpassing far the wildest representations of a Fuseli or a Kean. At this period several of the spectators were obliged to leave the room from terror or sickness, and one gentleman fainted." The bodies of horses, oxen, and sheep were galvanized, with results the most surprising. Five men were unable to hold the leg of a horse subjected to the action of a powerful battery.
So far as we know, nothing of much importance has yet been inferred from such experiments as these. Davy and Faraday, however, and their pupils, did not confine their attention to these barren wonders. Sir Humphry Davy took the "pile" as invented by Volta, in 1800, and founded by its assistance what may be styled a new science, and developed it to the point where it became available for the arts and utilities of man. The simple and easy process by which silver and gold are decomposed, and then deposited upon metallic surfaces, is only one of many ways in which the galvanic battery ministers to our convenience and pleasure. If the reader will step into a manufactory of plated ware, he will see, in the plating-room, a trough containing a liquid resembling tea as it comes from the teapot. Avoiding scientific terms, we may say that this liquid is a solution of silver, and contains about four ounces of silver to a gallon of water. There are also thin plates of silver hanging along the sides of the trough into the liquid. The galvanic battery which is to set this apparatus in motion is in a closet near by. The vessels to be plated, after being thoroughly cleaned and exactly weighed, are suspended in the liquid by a wire running along the top of the trough. When all is ready, the current of electricity generated by the small battery in the closet is made to pass through the trough, and along all the metallic surfaces therein contained. When this has been done, the spectator may look with all his eyes, but he cannot perceive that anything is going on. There is no bubbling, nor fizzing, nor any other noise or motion. The long row of vessels hang silently at their wire, immersed in their tea, and nobody appears to pay any attention to them. And so they continue to hang for hours,—for five or six or seven hours, if the design is to produce work which will answer some other purpose than selling. All this time a most wonderful and mysterious process is going on. That gentle current of electricity, noiseless and invisible as it is, is taking the silver held in the solution, and laying it upon the surfaces of those vessels, within and without; and at the same time it is decomposing the plates of silver hanging along the sides of the trough in such a way as to keep up the strength of the solution. We cannot recover from the wonder into which the contemplation of this process threw us. There are some things which the outside and occasional observer can never be done marvelling at. For our part, we never hear the click of a telegraphic apparatus without experiencing the same spasm of astonishment as when we were first introduced to that mystery. The beautiful manner, too, in which this silvering work is done! The most delicate brush in the most sympathetic hand could not lay on the colors of the palette so evenly, nor could a crucible melt the metals into a completer oneness.
And here is the opportunity for fraud. In five minutes an article is coated with silver in every part, inside and out; and that mere "blush" of silver, as the platers term it, will receive as brilliant a polish, and look as well (for a month) as if it were solid plate. Nay, it will look rather better; since the silver deposited by this exquisite process is perfectly pure, while the silver employed in solid ware is of the coin standard,—one tenth alloy. The plater can deposit upon his work as little silver as he chooses, either by weakening his solution, or by leaving the articles in it for a very short time; and no man can detect the cheat with certainty except by an expensive and troublesome process. Nor will it suffice for the operator to attend to the strength of his solutions, and keep his eye upon the clock. As in certain conditions of the atmosphere we can scarcely get a spark from the electrical machine, so there are times when the galvanic battery works feebly, and when the silvering goes on much more slowly than usual. To guard against errors from this cause, there is no sure resource but a system of careful weighings. In such establishments as that of the Gorham Company of Providence, Tiffany's or Haughwout's of New York, Bailey's of Philadelphia, and Bigelow Brothers and Kennard's, or Palmer and Batchelder's, of Boston, each article is weighed before it is immersed in the solution, its weight is recorded, and it is allowed to remain in the solution until it has taken on the whole of the precious metal it was designed to receive.
There was a lawsuit the other day in New York, which turned upon the quantity of silver deposited upon sundry gross of forks and spoons. The plater agreed to put upon them twelve ounces of silver to the gross, which is about as much as is ever deposited upon spoons or forks. If he had performed his contract, he would have spread over each table-spoon about as much silver as there is in a ten-cent piece; and such is the nature of silver that these spoons would have worn well for five or six years. In fact, there are no better plated spoons yet in use than these were designed to be. The plater meant to comply with the usages of the trade. He meant to put upon those spoons the quantity of silver which, in the trade, stands for twelve ounces to the gross, which is about ten ounces to the gross. Such, was probably his virtuous intention, and he supposed he had carried out that intention. But when the spoons were put to the test, it was discovered that upon one hundred and forty-four table-spoons there were but three ounces and a half of silver. It came out on the trial that the plater never weighed his work, and trusted wholly to the length of time he left it in the solution. He appeared to be honestly indignant at the testimony showing that his spoons, which had been left four hours subject to the action of the battery, had acquired only a film of silver. To the eye of the purchaser, these spoons would have presented precisely the same appearance as the best plated ware in existence. For two or three months, or even for six months, they would have retained their brilliancy. What their appearance would have been at the end of a year or two we need not say, for most readers have encountered the spectacle in their pilgrimage through a world which is said to resemble plated articles of this quality in being "all a fleeting show."
Every one is familiar with the gold lining that is now so generally seen in silver vessels. This is laid on by the same process as that which covers the outside with silver. The vessel is filled with a solution of gold, and in this solution a thin plate of gold is suspended. The electric current being made to pass through the interior thus prepared, the liquid bubbles up like soda-water, and in three or four minutes enough gold is deposited upon the inside surface for the purpose designed. When this is accomplished, nothing remains but to polish the vessel, within and without, and we have a piece of ware which is silver when we look at it, and golden when we drink from it.
The obstacle to the introduction of the superior plated ware now made by the Gorham Company is its costliness. The best plated ware costs five times as much as the worst, and one fourth as much as solid silver. We saw the other day three large salvers, which, at a distance of six feet, looked very nearly alike. All of them bore a most brilliant polish, and all were elaborately decorated. One of them was a trashy article, made of an alloy of lead and tin, covered with a "blush" of silver. It had been stamped out and shaped at one blow by a stamping-machine, and left in the silver solution subject to the action of the battery for perhaps fifteen minutes. It was very heavy, and when it was suspended and struck it gave forth a dull leaden sound. The price of this abomination was thirty-seven dollars and a half, and it would last, with careful occasional usage, for a year. Daily use would disclose its real quality in a few weeks. Another of these salvers was of solid silver, to which no objection could be made except that its price was nine hundred and fifty dollars. The third was of that superior plated ware introduced recently by the Gorham Company of Providence. The base of this article was the metal now called nickel silver,—a mixture of copper, nickel, and zinc,—3 very hard and ringing compound, perfectly white, and capable of a high polish. Upon this hard surface as much silver had been deposited as upon the best Sheffield plated ware, which is about as much as can be smoothly put upon it by the electro-plating process. When this salver was struck, it rang like a bell, and it would not bend under the weight of a man. Such a salver, used continually, will retain its lustre for a whole generation, and when, after that long period, it begins to lose its silver coating, it can be re-silvered and made as good as ever. But the price of this article was two hundred dollars,—more than five times the cost of the leaden trash, and a fourth of the price of the solid salver. Nevertheless, plated ware of this quality is the only kind which it is good economy to buy. There are few more extravagant purchases we can make in housekeeping than lead and brass ware, covered with a film of silver so thin that one ounce of the precious metal can actually be spread over two acres of it.