religious development of children should be liturgic, we must not be understood as denying them the exercise of good works. The last page of our former article will vindicate us from such a supposition. These, however, we contend, as we did then, should be almost entirely domestic, and altogether private. Their only public religious action should be in Church; there alone can they be seen by others in a Christian capacity, without the imminent risk of injury to themselves. 1843. Elements of Electro-Metallurgy. By ALFRED SMEE, F.R.S. 1843. London: Edward 1842. In our number for June, 1842, (vol. iii. pp. 631-644,) we traced the History of Electricity from its earliest days, six centuries before the Christian era, in the time of Thales, to the date of Coulomb's investigations; to whom we are indebted for the subjection of electro-statical phenomena to the rigorous rule of mathematical analysis, and the establishment of the fundamental principles of electro-statics as an independent science. In that article we were chiefly occupied with the elementary theories appertaining to the subject: in the present, we propose to consider some of its practical applications. The Natural science presents to us both laws and works: it has both its credenda and its agenda; its researches are both lucifera and fructifera; its end is both "the knowledge of causes and secret motions of things, and the enlarging of the bounds of human empire to the effecting of all things possible." latter of these was a continual subject of high and bright anticipation to Lord Bacon; and, throughout all his writings, he dwells upon it with enthusiastic hope. In that interesting philosophical romance, the New Atlantis, he assigns a principal place to those "fellows" of "Solomon's house" who devote themselves to the Practical. "We have three that bend themselves, looking into the experiments of their fellows, and cast about how to draw out of them things of use and practice for man's life and knowledge, as well for works, as for plain demonstrations of causes, and the easy and clear discovery of the virtues and parts of bodies. These we call dowry-men, or benefactors." "For our ordinances and rites, we have two very long and fair galleries: in one of these we place patterns and samples of all manner of the more rare and excellent inventions; in the other, we place the statues of all principal inventors. There we have the statue of your Columbus, that discovered the West Indies; also the inventor of ships: your monk that was the inventor of ordnance, and of gunpowder; the inventor of music; the inventor of letters; the inventor of printing; the inventor of observations of astronomy; the inventor of works in metal; the inventor of glass; the inventor of silk of the worm; the inventor of wine; the inventor of corn and bread; the inventor of sugars, and all those by more certain tradition than you have. Then we have divers inventors of our own of excellent works... Upon every invention of value, we erect a statue to the inventor, and give him a liberal and honourable reward. "We have certain hymns and services, which we say daily, of laud and thanks to GOD for His marvellous works; and forms of prayers, imploring His aid and blessing for the illumination of our labours, and the turning of them into good and holy uses." It has rarely been permitted to natural science to advance in both directions at once. When Newton pierced the skies, and raised philosophy to heaven, the scientific arts were comparatively few and weak. Now that the busy hands of science have made the surface of the civilized earth a theatre of wonders, her eye is all but closed to lofty speculations; and, having become the handmaid of material utility, she no longer reigns as a queen in the higher world of mind. Among our men of science we have "mystery-men," who "collect the experiments of all mechanicalarts;"-" pioneers or miners," who "try new experiments;" and we are not without " lamps," who "out of former labours and collections, take care to direct new experiments, of a higher light, more penetrating into nature than the former." But the age still waits for an "Interpreter of Nature," who shall collect the scattered Sybilline leaves, and proclaim the one complete and consistent meaning of the broken oracles. Meanwhile, science heedfully toils on in the laboratory and the workshop. Her hand is busy though her eye is closed, and she fails not to scatter profuse material gifts among the sons of men. Her glory though obscured is not departed; and she awaits, in patient hope, the time when a new truth shall emerge from her multitudinous works, to rule over them; when her present humble ministrations to the material comforts and outward necessities of man, shall be rewarded by one of those grand and simple interpretations, which illuminate and exalt the age that witnesses their birth. Next to chemistry, no science has been more fruitful than electricity in works subservient to the general purposes of life. The contributions of this infant science to the arts are too numerous to be described in full; and we shall confine ourselves to a notice of the more prominent, previously glancing at the general theory of electrical action, as far as appears to be necessary to our immediate purpose. The identity of all the various kinds of electricity has been established by Faraday. From the time of Gilbert, the effects produced by friction on certain dry substances had been grouped under the common name of " electricity;" a word indifferently applied to the science conversant with these and kindred phenomena, and to the agent whether a mode of action only, or a material but exquisitely subtle fluid-by which these effects were produced. The term "galvanism" had been applied to the effects resulting from the contact of different metals: while those effects which depend upon the action of the magnet were called " magnetism." But these various effects, at first attributed to different agents or causes, have been traced up by the indefatigable philosopher just named, to one and the same source: and it has been satisfactorily shown by his laborious and admirable researches, that electrical, galvanic, and magnetic phenomena, together with the intermediate varieties of electromagnetism, animal electricity, thermo-electricity, electro-chemistry, &c. are all modifications of one agent, which exhibits itself under different forms according to the mode in which it is excited. The two principal of these forms are those now familiarly known as common and voltaic electricity. The first of these might properly be designated electricity of tension. It is well exhibited by the common electrical machine, with its prime conductor and the Leyden jar. It seems to result from the accumulation of electricity, or, as it is conveniently termed, "the electric fluid," on the surfaces of bodies; and has a continual tendency to escape, until an equilibrium is restored between the electrified body and those by which it is surrounded. The most magnificent specimen of this state of electricity is furnished by a thunder-storm. The other state of sensible or free electricity is that exhibited by electricity in motion; the effects being such as might be produced by a current flowing with enormous rapidity. Hence the term "electric current." In this case a vast quantity of electricity may be in action, but without any apparent intensity. Whilst the current is unbroken, it produces various magnetic phenomena: when interrupted, it produces chemical changes upon the interposed substances, under certain conditions; decomposing some, heating, igniting, deflagrating others. Common electricity differs from voltaic, in having a much greater degree of intensity or tension; so that it acts with greater elastic force in a given direction. On the other hand, voltaic differs from common electricity in the enormous quantity of electric "fluid" which it develops and puts in motion, and in the continuity or perpetual reproduction of the current. Having thus briefly drawn out the difference between these two forms of electricity, we shall, through the remainder of this paper, speak only of the second of them, as being that from which those practical applications flow, which are our immediate subject of consideration. Voltaic electricity, although indebted to Volta, professor of natural philosophy at Pavia, 1800, for its distinguishing name, (that philosopher having been the first to give an exact and scientific character to his researches in this fascinating department of physical inquiry,)-owes its origin, in a great measure, to Galvani, professor of anatomy at Bologna, 1789. The first stages in the growth of scientific discovery, like the first stages in the growth of a plant, are generally obscure, and the exact circumstances and dates unknown; so that the honours of discovery rarely encircle the head of the rightful candidate, and the favourite motto of aspirants-"Palmam qui meruit ferat"-is reversed. Thus Amerigo gained the honours due to Columbus: the invention of the fluxionary or differential calculus was disputed by Leibnitz and Newton: Franklin usurped the claim to priority of discovery with regard to the identity of lightning and common electricity. And, in the case before us, although the substitution of the word "voltaic" for the word “galvanic” is an example of a corrected judgment, yet, to do full justice, we must go back to dates anterior to those of both the philosophers, from whose names these words have been derived. According to M. Becquerel, whose Traité Expérimental de l'Electricité et du Magnétisme is the standard work on the subject of which it treats, Sulzer, in 1782, was the first to bring to light the fact upon which galvanism or voltaic electricity historically rests. The fact was this: If we place a strip of zinc and a strip of silver, one upon and the other under the tongue, and bring their further extremities together, we perceive a taste similar to that of sulphate of iron, and at the same time a faint light, although each strip separately produces no effect whatever. Again, in 1786, Cotugno stated, in an early number of the Journal Encyclopédique de Bologne, that a medical student, whilst dissecting a live mouse, was much surprised by experiencing in his hand a slight electric shock, upon touching with his scalpel one of the nerves of the animal. These two facts, unconnected with any of the then known truths of physiology, and, indeed, wholly dissimilar, attracted little or no interest until 1789, when Galvani's attention was drawn to those phenomena attendant upon the accidental electrization of a skinned frog, which are too well known to allow of our relating them here. The explanation which Galvani gave of the convulsive motions of the frog's leg, when placed in contact with metallic bodies, was that the muscle of the frog was a sort of Leyden phial; that the nerves represented the interior, and the muscles the exterior coating of the phial; and that the discharge or shock took place by the metals communicating between the two electrified coatings. These experiments excited general interest. Valli, Fowler, Robison, Volta, Wells, Humbolt, Fabrici, and others, turned all their energies in this direction; but of all these experimentalists, Volta was by far the most successful. Galvani's most important discovery had been that relating to the influence of different metals in producing the convulsive movements of the dissected animal. This fact was Volta's starting-point. While Volta acknowledged Galvani's right to the priority of discovery, and always spoke of him with respect as an industrious experimentalist, he strenuously opposed Galvani's theory, and successfully maintained his own; which was, that the exciting cause was ordinary electricity produced by the contact of the two metals, and that the convulsions of the frog arose from the passage of the electricity thus developed along its nerves and muscles. But the great contribution of this philosopher to the infant science was the Voltaic Pile; an instrument, which has grown into the voltaic batteries of Cruikshanks, Wollaston, Children, Hare, Faraday, Daniell, and several others. We will content ourselves with describing the simplest form of this instrument; one too simple indeed to be of any practical use, but better suited than more complete and complicated forms to elucidate the theory of the action of the pile and battery. Immerse a strip of pure zinc, and another of silver, in a cup of very dilute sulphuric acid. No action will ensue. But if we bring together the extremities of these strips which are out of the fluid, a decomposition of the water immediately begins; its oxygen combines with the zinc to form oxide of zinc, which is dissolved by the acid; while the hydrogen passes over to the surface of the silver, where it collects, and ultimately escapes in gaseous globules. At the same time there is a continuous current of electricity from the zinc across the water to the silver, and from the further extremity of the silver back to the zinc which is there in contact with it. If we now restore the strips to their original position, but attach a wire to the outer extremity of each, and then bring the further extremities of these wires together, the decomposition of the water will take place as before, and the current of electricity will flow in the direction indicated by the darts in the annexed diagram. Various substances may evidently be interposed at A; and, provided they are capable of transmit |