« PreviousContinue »
To trace the history of the art of working in metals by the galvanic fluid, we have not to extend our enquiry into remote periods, for truly it may be said that this art belongs to our own time, and is a characteristic of the present age. Whilst however, we pursue our investigations into the history of this subject, we find that it has had by no means a sudden origin, for by degrees, at different periods, various persons have worked out one fact after another, till the comprehensive science has been developed, of which this volume is but a brief epitome. The art may be said to have had its origin in the discovery of the constant battery by Professor Daniell, for there the copper was continually reduced upon the negative plate. In his first experiment, this distinguished author observed, on removing a piece of the reduced copper from a platina electrode, that scratches on the latter were copied with accuracy on the copper. In this experiment we have the electrotype; but the author, in this paper, had devoted all his attention, and centered all his energies to the construction of the battery itself, and this valuable fact attracted but little of his notice.
It was not a long time after the discovery of this battery, that Mr. De la Rue experimented on its properties. paper printed in the Philosophical Magazine for 1836, after describing a peculiar form of battery which he adopts, the following remarkable passage is found: "The copper plate is also covered with a coating of metallic copper, which is continually being deposited; and so perfect is the sheet of copper thus formed, that being stripped off, it has the counterpart of every scratch of the plate on which it is deposited." This paper appears to have attracted very little attention; and what appears still more singular, the author, although well qualified, from his scientific attainments, to have applied these facts, never thought of any practical benefit to which this experiment might lead.
In this state the subject remained till October, 1838, when Professor Jacobi first announced that he could employ the reduction of copper, by galvanic agency, for the purposes of the arts. His process was called galvano plastic. Immediately upon his discovery being announced in this country in 1839, Mr. Spencer stated that he had executed some medals in copper, to which the public afterwards gave the name of electrotypes or voltatypes.
Now what is the precise value of the discovery of these productions over the facts already described?—for we have seen that the reduction of the copper, as a perfect plate, taking the exact form of the negative metal on which it was deposited, had been already noticed. Why, it is simply the idea of the application of these facts; but that idea has been everything. The only apparatus which Mr. Spencer employed, was in fact, a simple Daniell's battery. He employed various metals for the reception of the precipitated metal, which however, was nothing new; but he does not seem to have succeeded with any non-conducting substances. He executed medals, and perhaps duplicate copper plates; but he does not give any details, as to the different methods for the reduction of the copper in different states, neither did he succeed with the
reduction of any other metal. However, to Mr. Spencer the British public are principally indebted for the idea of the electrotype; and perhaps the idea, as far as relates to its application in Great Britain, originated entirely with
Mr. Spencer's first paper was printed in the journal of the Polytechnic Institution of Liverpool, in 1839; but the author complains, that by mismanagement it was prevented from being read at the British Association. Any discouragement of science in the present time is greatly to be lamented, and the more especially when we see that the Germans are already taking the lead, not only in chemistry, but also in physiology. Every well-wisher of science must hope that an over anxiety to prevent the publication of what is old, will not cause the referees of our learned societies to omit what is new. However, we are not so much behindhand, but that a little zeal on the part of those who have an established reputation for scientific acquirements, joined to the effect which encouragement would have on the junior members of the country, will enable the British to keep the foremost rank in science among the European nations. There are many now working zealously and ardently for the sake of obtaining truth, struggling against the most disheartening opposition: let that opposition be changed for assistance, and great indeed will be the results.
Perhaps in this place I may call the attention of scientific men to the fact, that persons are actually employed by great continental powers to find out every thing new that is discovered in this country, which, in a very few hours can be conveyed to any part of Europe. This hint is thrown out, not to deter Englishmen from generously giving their discoveries to all countries, but to cause them to be cautious not to mention their processes till they have appeared in some British publication, and thus vindicated the scientific character of our own country. This is the more necessary, as the English receive only the pleasure which the consciousness of being useful must afford, whilst the foreigner receives pecuniary emolument,
which singularly increases his desire of being acquainted with the inventions of other countries.
I may further notice, in order to confirm what I have already stated, that the galvano-plastics of Jacobi, and the electrotype of Spencer, is not a science which is the result of inductive reasoning and laborious research, like Professor Wheatstone's electro-telegraph, but merely an application of a fact formerly known to Daniell, recorded particularly by De la Rue, and observed by hundreds of others, that both Spencer and Jacobi could work only in copper, and in no other metal; whilst, had they prosecuted their subject as a science, they would have seen that the same laws regulate the reduction of all the metals.
The next discovery, which is fully equal in value to the idea of the electrotype itself, was made by Mr. Murray. He found out that non-conducting substances might have metallic copper thrown down upon them, by previously applying black lead. His process is extremely simple, and absolutely perfect. The first application of this invention was made in January, 1840; but it is to be lamented that he did not further extend its application and publish his researches, for his method was communicated orally, in the conversaziones of the Royal Institution, and not by any paper. I lay particular stress upon the value and perfection of plumbago, because some have denied its applicability; and the reader will find, in many parts of the work, that I have extended the use of this substance, to the benefit of the public, and to the fame of the inventor. I have made very extensive enquiries, in order to ascertain who really first used plumbago for this purpose, and I have the testimony of several authorities that it was Mr. Murray, whose claim therefore to this invention is rendered quite indisputable.
Other authors, as Mr. Solly and Mr. Spencer, subsequently gave processes for obtaining a metallic coating; but these are far inferior to that of Mr. Murray, besides being more troublesome and expensive.
Up to April, 1840, the single-cell apparatus was invariably used, but then Mr. Mason very ingeniously devised another mode by which the reduction might be effected. He used the single-cell apparatus as a Daniell's battery, which he connected with another cell, to reduce another metal. In the second cell he used a copper positive electrode, which was dissolved during the action. By this means he made two medals by one pound of zinc, or in other words, obtained two equivalents of copper for one of zinc.
However, up to that time, no laws had been determined for the reduction of the metals in different cases, notwithstanding a short paper which I sent to the philosophical magazine, accompanied by an engraving multiplied by my galvanic battery. This was the first electrotype plate that ever had one thousand copies printed from it.
The laws regulating the reduction of all metals in different states are given in this work, as the result of my own discoveries. By these we can throw down gold, silver, platinum, palladium, copper, and many other metals in three states, namely, as a black powder, as a crystalline deposit, or as a flexible plate. These laws appear to me at once to raise the isolated facts known as the electrotype into a science, and to add electro-metallurgy to the noble arts of this country.
The number of experiments, I may even say the thousands, that have been tried to elucidate these laws (for this book is not a detail of experiments, but rather a digest of them) could never have been executed had I not first discovered my galvanic battery; for its simplicity alone enabled me, without any assistance, to undergo the laborious undertaking. I am fully aware that some may disagree with me as to the superiority of my battery over all others for experimental and manufacturing purposes. I shall not flinch upon this account from stating its advantages, especially as they appear to me likely to contribute to general benefit.
The value of the battery process over all others, is its applicability to all cases; moreover, when we use a single cell of