with his theory, that when a copper plate was rotated in the plane of the magnetic dip no currents of electricity were developed in the plate, whilst placed in any other plane the earth acted as a magnet, and the currents of electricity at once began to circulate.

What results, it may be asked, have accrued from this discovery of magneto-electricity? To what practical uses has the discovery been applied? In the first place, then, the original electric telegraph established between Weber's laboratory in the University of Göttingen and Gauss's Observatory was worked by moving a coil of wire over a permanent magnet, and even to the present day, all the smaller telegraph lines are worked by Wheatstone's machines, which depend upon the production of Faraday's magneto-electricity. Then the beautiful art of electro-plating in gold and silver is now almost entirely carried on by Faraday's currents produced by magnetism. Enormously powerful magneto-electric machines are now made by Mr. Wilde and Mr. Holmes, which, worked by steam power, yield us by far the most available source of electricity. With these machines heat in the steam engine is converted into electricity, for the coils of wire placed as armatures in front of the poles of an enormous magnet are driven rapidly round by the engine, and in these coils so powerful a current is developed, that a bar of inch iron several yards in length can be heated to whiteness and fused by its means. The electricity can be thus reconverted into heat, or, by the white hot carbon poles, we may obtain the brilliant electric light, whose rays beam through the fogs of the Channel from Dungeness and meet the answering signal from La Hève. Or, if we please, we may use the current to effect chemical change, as in Elkington's far-famed manufactory in Birmingham, where six powerful magneto-electric machines deposit gold and silver on moulds of the most chaste and artistic forms. These practical uses of Faraday's currents are each day being extended. At this moment,' says Dr. Tyndall, the Board of Trade and the Brethren of the Trinity 'House, as well as the Commissioners of the Northern Lights, are contemplating the introduction of the magneto-electric light at various points upon our coasts, and future generations will be able to refer to those guiding stars in answer to the ' question-What has been the practical use of the labours of 'Faraday?'

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The records of the years 1832-33-34 now extant show the vast amount and the high importance of the work which Faraday accomplished. Amongst the chief of these labours was his attack on the difficult problems of the Identity of the

Electricities. He was constantly troubled by the question, Do all the various modes of obtaining electricity really furnish the same manifestation of energy? Is the electricity of the Voltaic pile identical with that of the Gymnotus or of the electric machine, or with the kinds of currents produced by a magnet, or by heating a bar of dissimilar metals? He soon proved that ordinary frictional electricity affects the galvanometer, and thus showed the identity of these two forms; but this did not satisfy him. He must next be able to compare them quantitatively, or, as he terms it, find the relation by measure of common and Voltaic electricity. This he accomplished by determining how much work in the way of chemical decomposition, as in the separation of the constituents of water, each kind of electricity can do. He finds that the amount of frictional electricity needed to decompose a single grain of water is so enormous that he is almost afraid to mention it, as he estimates it at 800,000 discharges of his large battery of Leyden jars!

'When the loud crash of the thunder or the lightning's flash awakens us from our thoughtless abstractions or our reveries, our feelings become impressed with the grandeur of Omnipotence and the might of the elements He wields, yet the whole fury of the thunderstorm-what is that in comparison with the electric energies which silently and continually exert themselves in every chemical change? Why the electric force in a single drop of water, and disturbed when the water is decomposed, is of itself greater than is the electricity of a whole thunderstorm.'

Next in order, published in 1833 and 1834, come the wonderful researches on the chemical effects of the Voltaic current, ending in the discovery of the law of electrolysis. Of the numerous discussions of principles in which the history of science abounds, none is more interesting or instructive than the contest as to the origin and maintenance of the power of the Voltaic pile. To begin with, we have the celebrated controversy between Galvani and Volta respecting the source of the electric power, causing the motion of the frog's legs, discovered by the former philosopher in 1780. Galvani attributed the contraction of the muscles to animal electricity; Volta said that the electricity was produced by the contact of the heterogeneous metals with which the muscle was touched; Galvani replied by showing that the contraction can be produced without the presence of any metal whatever; and Volta, dispensing with the conditions which his rival had thought necessary, produced electricity without frogs, simply by the contact of heterogeneous metals! Here, as in many other cases, truth lies in the middle.

Galvani laid the foundations of animal electricity, now, chiefly through the labours of Du Bois Reymond, a recognised and important branch of the science. Volta discovered the Voltaic

pile, by which the effects of contact-electricity can be accumulated and multiplied. Singularly enough, Volta neglected to prosecute his inquiries into the chemical actions which can be brought about by his pile; but many other philosophers, such as Nicholson and Carlisle, Davy, Courtois and Gay Lussac, soon took up this side of the inquiry.

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It was, however, to Faraday, who in 1834 pointed out the importance of these decompositions effected by the battery, that we are indebted for the chemical theory of the Voltaic pile in which chemical action and not metallic contact is made the source of the current of electricity. 'The contact theory,' says Faraday, assumes that a force which is able 'to overcome resistances can arise out of nothing, for, not even in the case of the Gymnotus and Torpedo, is there a pure creation or production of power without a corresponding exhaustion of something to supply it.' That on mere contact two different metals do become charged, one with negative and the other with positive electricity, is certain, but it is equally certain that no current or rush of electricity capable of doing work, whether in the decomposition of a salt or the raising of a weight, can occur unless a corresponding amount of energy is developed in the cell by the chemical changes there going on. Faraday was, however, the last man to be led to conclusions without sufficient basis, or to support a theory unless founded on exact experiments. He showed that the chemical decompositions brought about by the current always take place in definite atomic proportions; that if, for instance, we decompose with the same current two chemical substances at once, such as water and chloride of tin, the quantity of the hydrogen and that of the tin separated stand to one another in the proportion by weight of their chemical equivalents, or as 1 to 59; nor is this all, for every equivalent of one element separated out by the current, exactly one equivalent of zinc, or 32.6 parts by weight of zinc, dissolves in each of the cells. Here then we have the secret power of the battery divulged; here we see its working plainly shown. The zinc oxidises or burns in the battery; the energy thus developed passes along the wire in the form of the current, and can be made to do various kinds of work; thus it may either produce heat or effect chemical decomposition. This latter it accomplishes according to a definite law, which Faraday proved to be unalterable under all

sorts of changing circumstances, a law which serves the chemist as a remarkable confirmation of Dalton's laws of definite combining proportions, and with them now forms the foundationstone of chemical science.

During the two years spent in making these researches, Faraday not only undertook many other original investigations of importance, but he was busily engaged in lecturing at the Institution both on old and familiar subjects as well as on new discoveries. Thus in 1832 he gave a course of five lectures on some points of domestic chemical philosophy-a candle, a lamp, a chimney, a kettle, ashes. His Friday evening discourses were six in number, some being an account of his own experiments on magneto-electric induction, some being descriptions of the discoveries of others. In 1834 he gave his first utterance on the correlation of the physical forces. Now consider,' he says in his notes, a little more generally the relation of all 'these powers. We cannot say that any one is the cause of the others, but only that all are connected and due to one common cause. As to the connexion observe the production. of any one from another, or the conversion of one into another.' In 1853 Faraday marked these notes with his initials, and added correlation of physical forces.' Mr. Grove's celebrated lecture on this subject at the London Institution was in 1842; Faraday's at the Royal Institution on June 21, 1834.

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In 1832 he collected and bound up together the different notes, papers, notices, &c., published in octavo, up to this time; and he adds this very characteristic preface:

'Papers of mine published in octavo in the "Quarterly Journal of "Science" and elsewhere, since the time that Sir H. Davy encouraged me to write the "Analysis of Caustic Lime." Some I think (at this date) are good, others moderate, and some bad. But I have put all into the volume, because of the utility they have been to me, and none more than the bad, in pointing out to me in future, or rather after times, the faults it became me to watch and avoid. As I never looked over one of my papers a year after it was written without believing, both in philosophy and manner, it would have been much better done, I still hope this collection may be of great use to me.'

An incident worthy of notice as exhibiting Faraday's character occurred in 1835. It appears that in April of this year Sir Robert Peel desired Sir James South to inform Faraday that had he (Sir Robert) remained in office, it was his intention to have offered Faraday a pension. In his answer, Faraday, after thanking South, says :

'I cannot accept a pension whilst I am able to work for my living.

Do not from this draw any sudden conclusion that my opinions are such and such. I think that Government is right in rewarding and sustaining science. I am willing to think, since such approbation has been intended me, that my humble exertions have been worthy, and I think that scientific men are not wrong in accepting the pensions; but still I may not take a pay which is not for services performed whilst I am able to live by my labours.'

This letter was however, at the advice of his father-in-law, not sent, and one containing a less definite refusal forwarded in its place. Nothing more was heard of the pension until Oct. 26th, when he was asked to wait upon Lord Melbourne. A conversation took place, in which the Prime Minister expressed himself' certainly in an imperfect and perhaps in too blunt and in⚫ considerate a manner;' and probably said or insinuated that the whole system of literary and scientific pensions was a complete job and a piece of humbug. Faraday on the same day, after the interview, left the following note for his Lordship:

'My Lord, the conversation with which your Lordship honoured me this afternoon, including as it did, your Lordship's opinion of the general character of the pensions given of late to scientific persons, induces me respectfully to decline the favour which I believe your Lordship intends for me; for I feel that I could not, with satisfaction to myself, accept at your Lordship's hands that which, though it has the form of approbation, is of the character which your Lordship so pithily applied to it.'

The refusal of the pension became known, and it even reached the King, and it pleased him to remind his Prime Minister of it whenever he had an opportunity. Perhaps to avoid these remarks, and perhaps for other reasons, an excellent lady, who was a friend both to Faraday and the Minister, tried to arrange matters betweem them; but she found Faraday very difficult to move from the position he had assumed. After many fruitless attempts, she at length begged of him to state what he would require of Lord Melbourne to induce him to change his mind. He replied, "I should require from his Lordship "what I have no right or reason to expect that he would grant-a "written apology for the words he permitted himself to use to me." After some days the required apology came in a frank letter, and Faraday's answer ended with the words, "I hesitate not to say that "I shall receive your Lordship's offer both with pleasure and with " pride."'

During the two years ending November 30, 1837, Faraday was unremittingly engaged on his researches on Frictional Electricity, and on the above day his first great paper on this subject was read before the Royal Society. These researches contain more speculative matter than any of his former works. He tries to dive into the electric actions of the smallest par