THE APPLICATION OF THE INVENTION.

But before we proceed to the immediate object before us, it will be desirable to answer a question, which will, no doubt, be proposed by many of our readers. "To what purposes can the invention be applied?" Mr. Spencer has given a cautious, and we believe, a correct reply to this interrogation.

"I entertain no very sanguine notions as to the future general application of this method of operating upon the metals, more especially copper. This must be entirely left to the practical engraver and printer.

"The question will then be-Is it cheaper and better than the methods in common use? It may now be answered, Give it a fair trial: the way is pointed out, practice will no doubt enable you to improve upon the methods which suggested themselves during the experimental investigation detailed in the following pages; and most probably may realize an extended field of practical utility for the peculiar mode of operation which has been the result.

"I feel assured, however, that in the arcana of many trades and branches of art, this process will be found an important addition; supplying, as it does, a means of producing a cast or a die in hard metal, without the agency of heat or pressure, and in extreme perfection and well defined sharpness. Nor, I need hardly observe, is its application confined to copper only.

"In addition to the applicability of this process, in procuring fac-similes of coins or medals, with all the lineal sharpness of the original; perfect copies may be obtained of bronzed figures, nor do they require chasing when taken out, nor do I apprehend inconvenient limitation as regards their size.

Assuming it to be advantageous to publishers of music to have their plates in relief; by this process they will be enabled, in the original engraving, to have them so.

"I have seen nothing in wood engraving that might not be produced in copper, in relief, by this means; the chemical plates might possibly require retouching to a small extent: but, with careful manipulation, twenty or thirty plates might be taken from one mould.

"I may mention that the advantage of being able to produce a given effect from a plate in relief would be very considerable, as ten printed impressions

may frequently be taken in the time occupied by producing one by the ordinary method from a copper-plate. Plates in relief might also frequently be printed off in the body of the work, which, in point of economy, would be a very considerable advantage.

"In the formation of that important implement in the manufacture of printing types, the matrix or mould, advantages in the adoption of this operation appear to present themselves. And I am assured by the printers of this pamphlet, that it gives fair promise to supply several important desiderata in the art of printing, and in its attendant operations, more particularly in the stereotype process.

"In general, I feel convinced that it exhibits many promising indications of utility, should no obstacles in a pecuniary point of view present themselves, on occasion of attempts to extend the application of the discovery."

Such are the prospects entertained of the advantages to be derived from the use of voltaic electricity in taking metallic impressions, forming moulds and in other ways working upon metals.

HISTORY OF THE INVENTION.

With the voltaic, or as it is sometimes called, the galvanic battery, many of our readers must be acquainted, either from having seen or used it. It consists of plates of the two metals copper and zinc, acted upon by some liquid. The form commonly employed in the present day is that represented in the accompanying diagram. c is a cylin

Z

Z C

der of copper and z of zinc contained in an earthenware jar. The copper is inserted in a bladder, and is acted upon by a solution of the sulphate of that metal. The zinc which is thus shut out from any immediate contact or communi

"There was one important, and to me discouraging circumstance," says Mr. Spencer, "attending these experiments, which was, that when I heated the plates to get off the covering of cement, the meshes of copper net work" (for it was in the form of net work that he was depositing the metal) "invariably came off with it. I at one time imagined this difficulty insuperable, as it appeared to me that I had cleared the cement entirely from the surface of the copper I meant to have exposed; but that there was a difference in the molecular arrangement of copper prepared by heat, and that prepared by voltaic action, which prevented their chemical combination. However, I then determined, should this prove so, to turn it to account in another manner."

It happened, however, that upon the examination of the results of one experiment, a part of the copper deposition formed upon a coin adhered so tenaciously that it could not be removed; "indeed a chemical combination had apparently taken place. This," says the discoverer, "was only in one or two spots, on the prominent parts of the coin. I immediately recollected that on the day I put the experiment in action, I had been using nitric acid for another purpose, on the table I was operating on; and that in all probability the coin might have been laid down, where a few drops of the acid had accidentally fallen. I then took a piece of copper, coated it with cement, made a few scratches on its surface until the copper appeared, and immersed it for a short time in dilute nitric acid, until I perceived by an elimination of nitrous gas, that the exposed portions were acted upon sufficiently to be slightly corroded. I then washed the copper in water, and put it in action as before described. In forty-eight hours I examined it, and found the lines were entirely filled with copper. I applied heat, and then spirits of turpentine, to get off the cement; and to my satisfaction I found, that the voltaic copper had completely combined itself with the sheet on which it was deposited."

One other quotation from Mr. Spencer's paper, read before the Liverpool Polytechnic Society, we must be allowed to extract, as it will be found to contain a valuable hint to those who may attempt a certain class of the experiments we shall have occasion here

after to describe. "I then gave a plate a coating of cement, to a considerable thickness, and sent it to an engraver ; but when it was returned, I found the lines were cleared out so as to be wedgeshaped, leaving a hair line of the copper exposed at the bottom, and a broad space near the surface; and where the turn of the letters took place, the top edges of the lines were galled, and rendered rugged by the action of the graver. This, of course, was an important objection, which I have since been able to remedy, in some respects, by an alteration in the shape of the graver, which should be made of a shape more resembling a narrow parallelogram than those in common use: some engravers have many of their tools so made. I did not put this plate in action, as I saw that the lines, when in relief, would have been broad at the top and narrow at the bottom. I took another plate, gave it a coating of the wax, and had it written on with a mere point. I deposited copper on the lines, and afterwards had it printed from."

We have already mentioned an experiment in which a piece of copper (on which had been drawn lines in the form of net work) was used. Much difficulty was experienced in forming this design upon the copper, so as to expose the metal; for when the cement was soft, the lines were pushed into each other, and when of a harder texture, the intervening squares broke away from the surface of the plate. One difficulty, therefore, still remained, and it was the discovery of a proper cement or etching ground, one 66 which should be capable of being cut to the required depth, without raising what is technically called a burr, and at the same time of sufficient toughness to adhere to the plate, when reduced to a small isolated point, which would necessarily occur in the operation, which wood engravers term cross hatching."

Mr. Spencer, in his endeavour to obtain a suitable compound, tried a variety of experiments upon different compositions formed of wax, resins, varnishes and earth, and also with metallic oxides. At last he obtained one which for all his purposes seemed to be admirably suited; it was formed of virgin wax, resin, and carbonate of lead. With this cement, two plates, five inches by seven, were covered, and portions of maps engraven on them. This being done, they

were dipped in dilute nitric acid, a pro- | cess found in other instances so beneficial, and then introduced into the voltaic arrangement. The intention was to have formed metallic casts fit for printing, more especially with the view of presenting them and the printed sheets to the British Association. When the process had been continued sufficiently long, heat was applied to the plate to remove the cement but to the amazement of the experimenter the voltaic copper pealed off with the etching ground. The cause of this it was at first difficult to determine; but on cleaning the plate, a delicate tracing of lead was found on the line drawn on the cement previous to the immersion in the dilute acid. "The cause of this failure," says Mr. Spencer, was at once obvious; the carbonate of lead I had used to compound the etching ground, had been decomposed by the dilute nitric acid, and the metallic lead, thus set free, had deposited itself on the exposed portions of the copper plates, preventing the voltaic copper from chemically_combining with the sheet copper. I was now obliged with regret to give up this compound; although, under other circumstances, I have no doubt it may be rendered available."

The cement which was ultimately adopted by Mr. Spencer, was formed of bees' wax, common whiting, resin, a small portion of gum, and plaster of Paris. This compound, he speaks of as answering the purpose tolerably, though he anticipates a better may be found.

We cannot close this examination of the labours of Mr. Spencer, without an allusion to the results of his experiments in an attempt to obtain impressions in cameo and intaglio, although we intend in another number to explain the method in which the various experiments may be performed. From what has been already stated, the reader must be aware that no metallic deposition can be obtained by the action of voltaic electricity, without a metallic body, or we might more properly say a metallic surface, as a nucleus. Bearing this fact in mind, the following observations, by the discoverer of the process, must be read with interest.

"I placed a very prominent copper medal in a voltaic circuit (as already described) and deposited a surface of copper on one of its sides to about the

thickness of a shilling. I then proceeded to get the deposition off. In this I experienced some difficulty, but ultimately succeeded. On examination, with a magnifying glass, I found every line was as perfect as the coin from which it was taken. I was then induced to use the same piece again, and let it remain a much longer time in action, that I might have a thicker and more substantial mould. I accordingly put it again in action, and let it remain until it had acquired a much thicker coating of the metallic deposition; but when I attempted to remove it from the medal, I found I was unable. It had apparently completely adhered to it.

66

"I had often practised, with some degree of success, a method of preventing the oxidation of polished steel, by slightly heating it until it would melt virgin wax; it was then wiped, apparently completely off, but the pores of the metal became impregnated with the wax-I thought of this method, and applied it to a copper coin.

66

"I first heated the piece, applied wax, and then wiped it so completely off, that the sharpness of the coin was not at all interfered with. I proceeded as before, and deposited a thick coating of copper on its surface. After the lapse of a few days, when I wished to take it off, I applied the heat of a spirit lamp to the back, when a sharp crackling noise took place; and I had the satisfaction of seeing that the coin was completely loosened. In short, I had a most complete and perfect copper mould of a halfpenny.

"I have since taken some impressions from the mould thus formed; and by adopting the above method with the wax, I get them out with the greatest

ease.

"I was now of opinion that this latter method might be applied to engraving, much better than the method described in the first portion of this paper. Being aware that copper in a voltaic circuit deposited itself on lead with as much rapidity as on copper, I took a silver coin, and put it between two pieces of clean sheet lead, and placed them under a common screw press. From the softness of the lead, I had a complete and sharp mould of both sides of the coin. I then took a piece of copper wire, soldered the lead to one end, and a piece of zinc to the other, and put them into

the same voltaic arrangement I have already described. I did not, in this instance, wax the mould, as I felt assured that the deposited copper would easily separate from the lead, by the application of heat, from the different expansibility of the two metals.

66

"In this result, I was not disappointed. When the heat of a spirit lamp was applied for a few seconds to the lead, the copper impression fell easily off. So complete do I think this latter portion of the subject, that I have no hesitation in asserting that fac-similes of any coin or medal, no matter of what size, may be readily taken, and as sharp as the original. To further test the capabilities of this method, I took a piece of lead plate, and stamped some letters on its surface to a depth sufficient to print from when in relief. I deposited copper on it, and found it came easily off. "I now come to the conclusion of my experiments on this subject. As I stated at first, my object was to deposit a metallic surface on a model of clay, or other non-metallic body; as, otherwise, I imagined the application of this principle would be extremely limited. I made many experiments to achieve this result which I shall not detail, but content myself with describing that which was ultimately the most success

ful.

"I took two models of an ornament, one made of clay, and the other of plaster of Paris; soaked them for some time in linseed oil, took them out, and suffered them to dry, first getting the oil clean off the surface. When dry, I gave them a thin coat of mastic varnish. When the varnish was as nearly dry as possible, but not thoroughly so, I sprinkled some bronze powder on that portion I wished to make a mould of. This powder is principally composed of mercury and sulphur; I had however a complete metallic coating on the surface of my model, by which I was enabled to deposit a surface of copper on it, by the voltaic method I have already described. I have also gilt the surface of a clay model with gold leaf, and have been successful in depositing the copper on its surface."

GOD'S CHIEF GIFT.

H.

WHEN We reflect on the personal dignity of Jesus Christ, as the Son of God;

on the unchangeable interest he had in his Father's love; and on the Father delivering him up to an execrable death for mere sinners, we cease to wonder that, with him, he freely bestows all spiritual blessings, without any regard to worthiness in them on whom they are conferred. Because the gift of Christ himself is the grand evidence of God's love to sinners, incomparably greater than that of authorizing the ungodly to believe in Jesus, or than that of his giving heaven to saints.-Booth.

SALVATION.

OUR Saviour, Jesus Christ, having substituted himself in the place of sinners, suffered in his own person the punishment of sin, conformably to that declaration, "In the day that thou eatest thereof, thou shalt surely die." He came forth from among the dead in testimony that the threatening of God the acceptance of his sacrifice, and that was accomplished, and as a pledge of by his obedience unto death Divine justice was satisfied, the law honoured and magnified; and that eternal life was awarded to those for whom he died, whose sins he had borne in his own body on the tree, 1 Peter ii. 24. He was quickened by the Spirit, by whom he was also justified, 1 Tim. iii. 16, from every charge that could be alleged against him as the surety of them whose iniquities he bore. The justification, therefore, of his people, which includes not only the pardon of their sins, but also their title to the eternal inheritance, was begun in his death, and was perfected in his resurrection. He wrought their justification by his death; but its efficacy depended on his resurrection. By his death he paid their debt, in his resurrection he received their acquittance. He rose to assure to them the right to eternal life, fully to discover it, and to establish it in his own person, for all those who are the members of his body.-R. Haldane.

WEAKNESS OF HUMAN RESOLUTIONS.

To attempt to resist temptation, to abandon our bad habits, and to control our dominant passions, in our own unaided strength, is like attempting to check by a spider's thread, the progress of a ship of the first rate borne along before wind and tide.- Waugh.