GALVANOPLASTIC MANIPULATIONS. HISTORICAL FACTS RELATING TO ELECTRO-METALLURGY. THE value of the galvanic current as an agent for effecting the dissociation of chemical compounds was established by Sir Humphry Davy as long ago as the year 1808, when with its aid he succeeded in proving that soda, potash, lime, etc., were metallic oxides, and not elementary substances, as had previously been the universal belief. It was not, however, until many years after this that the decomposing power of the battery was applied to useful purposes in the arts. It was, however, soon observed that metals deposited by its agency, from their solutions, assumed various fantastical forms, which so closely resembled the growths of vegetation that they were not inaptly styled galvanic trees. But these observations might still have remained of no utility save to awaken the interest of students of chemistry by their beauty as philosophical experiments, had it not been for an accidental discovery by Professors Wagner and Jacobi in the year 1830, that the metallic deposits thus obtained might be used for plating and for copying. The history of this interesting discovery is briefly as follows: These investigators were endeavoring to solve the enticing problem of utilizing electro-magnetism as a motive power in place of steam. Jacobi employed in these investigations the Daniell battery, which will be presently described, and which is distinguished for its constant and regular action. When this battery is working, the sulphate of copper solution employed is slowly decomposed, depositing metallic copper, which, after a certain quantity of it has accumulated, interferes with the action of the battery and must be removed. Once when Jacobi was busied in removing such a deposit from his battery, he noticed that there were several layers of copper, each having the form of the sides of his vessel. The fact that the disposition of these layers imitated, in a remarkably perfect manner, the shape of the surfaces of the vessel to which they adhered, suggested to Jacobi the idea that this troublesome phenomenon might be turned to profit by employing it for reproducing effects in metal. Meantime, several important observations bearing upon the same subject were made by other investigators. Mr. De la Rue, for example (in 1836), noticed,* that the deposit of copper precipitated upon the copper plate of a peculiar form of Daniell's battery that he had devised, "was covered with a coating of metallic copper which is continually being deposited, and so perfect is the sheet of copper thus formed that, on being stripped off, it has the polish and even a counterpart of every scratch of the plate on which it is deposited." The following year Dr. Golding Bird succeeded in decomposing, with the battery, solutions of the chlorides of sodium, potassium, and * Mr. W. De la Rue, "On Voltaic Electricity, and on the Effects of a Battery charged with Sulphate of Copper." Lond. and Edinb. Philos. Mag., ix. (1836), p. 484 et seq. ammonium, and deposited these metals on a negative pole of mercury.* These observations, however, were followed by no practical results; and it remained for Prof. Jacobi, to whom the idea of utilizing his observations first occurred, to give them practical form. This noteworthy event took place in 1838, when he communicated to the Academy of Sciences of St. Petersburg, a description of his discovery of the utility of galvanic electricity as a means of reproducing objects in metals. This galvanoplastic process was claimed to be a method of converting any line, however fine, engraved on copper, into a relief by galvanic process, applicable to copper-plate engravings, medals, stereotype plates, ornaments, and to making calico-printing blocks, and patterns for paper hangings. The merit of having been the first to apply the electro-deposition of metals to useful purposes, and of having originated the galvanoplastic art, appears, therefore, to be due unquestionably to Jacobi. His discovery attracted at the time such attention that the Emperor Nicholas, after satisfying himself of its great value, gave its author the means of making the new art the common property of the world. In the year 1839, Mr. C. J. Jordan described (Mechanic's Magazine, June 8, 1839) a series of experiments for the purpose of obtaining by galvanic means casts in copper from various metals; in which reference is made to Jacobi's earlier work in this field. Mr. T. Spencer read a paper before the Liverpool Polytechnic Society on the " Electrotype Process," in the same year in which, among other things, he describes a method * Golding Bird, F.L.S., F.G.S., etc., "Observations on the Electro-Chemical Influence of Long-continued Electric Currents of Low Tension." Philos. Transactions, 1837, p. 37. of depositing "a metallic surface on a model of clay, wood, or other non-metallic body," by coating the surfaces of these models with a thin coating of mastic varnish, rendered conductive by means of bronze powder, and by means of which he was enabled to deposit a surface of copper on the prepared surface of the mould by the voltaic method. About the year 1840, Prof. Boettger succeeded in producing handsome relief plates of copper with the aid of the battery, and employed this apparatus also for gilding silver, copper, and brass. About the same time, Mr. John Wright, of Birmingham (Gore, Electro-metallurgy, 1877, p. 19), was engaged in experiments with the view of obtaining, with gold and silver, similar results to those already obtained by Jacobi, Spencer, and Jordan with copper, viz., thick deposits of firm, coherent metal, bright, and of good color. Led thereto by a suggestion of Scheele's, respecting the solubility of the cyanides of copper, silver, and gold, this experimenter made the important observation that a solution of the cyanides of gold and silver in the alkaline cyanides was capable of yielding a solid, coherent deposit of these metals by electrolytic action. Shortly after this (1841) Prof. Boettger succeeded in making a copy of one of Felsing's copper-plates (the Ecce Homo of Guido Reni, 12×9 inches) which proved to be so perfect that the engraver admitted that proofs printed with it were not to be distinguished from those taken from the original. Meantime, in 1840. M. de Roulz, a French electrodepositor (Gore, Electro-metallurgy, 21 et seq.), had taken out a patent in France for electro-gilding and silvering by means of solutions of the double cyanides and ferro-cyanides. His patent also included the use of similar solutions for the electro-deposition of platinum, copper, lead, tin, cobalt, nickel, and zinc (Encyclopædie, Roret, Galvanoplastie, tome ii. p. 114). From this time forward the galvanoplastic art made rapid progress. American experimentalists appear to have been among the earliest in the field in applying the new art to letter-press printing, a branch of the art to which the name of electrotyping is generally given. In 1842, Daniel Davis, of Boston, made and used electrotype plates of the engravings and letter-press of his Manual of Magnetism. In the previous year, Mr. Joseph A. Adams, of New York, is credited with having reproduced and printed an engraving in a magazine published by James J. Mapes, of that city; and in 1843, he electrotyped the various borders around the larger engravings in Harper's Illustrated Bible. From these beginnings the galvanoplastic art has developed into an industry of inestimable value to the printer, the publisher, the engraver, the artist, and the antiquarian. Its employment in reproducing copies of engravings and letter-press, coins, medals, etc. is almost universal, it is even successfully employed for the reproduction, in copper, of works of art of great size. In another direction, also, the galvanoplastic art has originated a great industry, the value of which, from the vast variety, popularity, and utility of its products, it would be difficult to over-estimate. Reference is made, in this connection, to the electroplating of artistic and useful articles of every conceivable description with gold, silver, copper, bronze, nickel, etc., to enhance their beauty and artistic value, or to protect the underlying surfaces from the action of destructive agencies. The developement of this branch of the art has of late been simply enormous, and it has placed within the reach of all classes objects of utility and beauty of the most artistic designs, which rival in |