and always so successful, that one might be apt to think that all this was the result of a happy intuitive power. Those who knew Faraday can tell, however, by what patient labour these results were brought about-how he used to spend hours upon hours arranging his experiments so as to ensure success-how no detail was too minute to escape his attention, and how well he had thought over the best mode of presenting his subject. The specimens of his lecture notes given in his Biography* show this excessive care, and the orderly neatness which was characteristic of his whole being, whilst the following extract may give to those who have missed the delight of hearing him, some slight idea of his characteristic style, and at the same time it will call up to the minds of those of us who knew him, the charm of voice and manner which were so peculiarly his own. He is addressing the audience of young people to whom for many years he gave a Christmas course :

'I shall here claim, as I always have done on these occasions, the right of addressing myself to the younger members of the audienceand for this purpose, therefore, unfitted as it may seem for an elderly infirm man to do so, I will return to second childhood, and become as it were, young again amongst the young.

Hence we

'Let us now consider, for a little while, how wonderfully we stand upon this world. Here it is we are born, bred, and live, and yet we view these things with an almost entire absence of wonder to ourselves respecting the way in which all this happens. So small, indeed, is our wonder, that we are never taken by surprise; and I do think that, to a young person of ten, fifteen, or twenty years of age, perhaps the first sight of a cataract or a mountain would occasion more surprise in him than he had ever felt concerning the means of his own existence; how he came here, how he lives, by what means he stands upright, and through what means he moves about from place to place. come into this world, we live, and depart from it, without our thoughts being called specifically to consider how this takes place; and were it not for the exertions of some few inquiring minds, who have looked into these things, and ascertained the very beautiful laws and conditions by which we do live and stand upon the earth, we should hardly be aware that there was anything wonderful in it. These inquiries, which have occupied philosophers from the earliest days, when they first began to find out the laws by which we grow, and exist, and enjoy ourselves, up to the present time have shown us that all this was effected in consequence of the existence of certain forces, or abilities to do things, or powers, that are so common that nothing can be commoner; for nothing is commoner than the wonderful powers by which we are enabled to stand upright-they are essential to our existence every moment.' We have now only brought Faraday to the commencement

* Vol. II., Appendix to Chapter I.

of his great discoveries. It is true, that if his scientific life had ended here, he had already earned for himself a high and honourable position in the ranks of science. He had been engaged in original scientific investigation for eighteen years (he always used to say that it required twenty years of work to make a man in physical science; the previous period being one of infancy); he had discovered electro-magnetic rotation, and he had thoroughly proved the possibility of the condensation of several gases into liquids. He had carried on two most laborious investigations on the alloys of steel and on the manufacture of optical glass. His discoveries in chemistry were of great interest and importance; of these the chief were in the first place the preparation of two new chlorides of carbon, then the discovery of benzol, the hydrocarbon now so valuable as a source of colour, of sulphonapthalic acid, besides several other new chemical compounds, whilst he had made interesting experiments on the limits of vaporisation and on the diffusion of gases. The catalogue of scientific papers lately compiled by the Royal Society shows, that up to the year 1830 he had printed no less than sixtytwo important scientific communications, nine of which were published in the Philosophical Transactions. From assistant in the laboratory of the Royal Institution he had become its Director; he constantly lectured in the theatre, and probably saved the Institution by the active interest he took in the establishment of the Friday evening meetings. It is, however, in the year 1831, when forty years of age and at the height of his physical and mental power, that Faraday began the work which has made his name illustrious.

Eight large volumes of private manuscript notes of 'Experi'mental Researches' were bequeathed by Faraday to the Royal Institution; these constitute a monument of human genius, industry, skill, patience, and orderly arrangement, perhaps only exceeded in the world by the contents of the celebrated Gauss-manuscripts deposited in the Observatory of Göttingen. The first paragraph in Volume I. begins in 1831; the last consecutive paragraph in Volume VII. is marked 16,041, in 1856! In all other matters Faraday's business-like sense of order was manifest; throughout all his numerous researches each experiment was numbered, and the result catalogued or the product carefully preserved; his accounts were most accurately and neatly kept; his letters were always read and answered early in the morning, before any other work was begun, and every complicated subject seemed naturally to fall into order under his hands. It is interesting to learn the

details of the method which such a man adopted for carrying out his experiments.

'Whenever he was about to investigate a subject, he wrote out, on separate slips of paper, different queries regarding it which his genius made him think were "naturally possible" to be answered by experiment. He slightly fixed them one beneath the other in the order in which he intended to experiment. As a slip was answered it was removed, and others were added in the course of the investigation, and these in their turn were worked out and removed. If no answer was obtained, the slip remained to be returned to at another time. Out of the answers the manuscript volumes were formed, and from these the papers were written for the Royal Society, where they were always read before the popular account of them was given to the Royal Institution at a Friday evening meeting.'

The second quarter of this century was the period of Faraday's great activity; the strain of the first ten years of this time produced loss of memory, and necessitated complete rest for nearly four years. After this much more work was done. What that work was, and how its results bear on science and civilisation, we shall next endeavour to ascertain.

On August 29, 1831, Faraday began his electrical researches. His lecturing, reading, and experimentalising had not only given him complete command over all the known phenomena of electricity, but enabled him to see the directions in which knowledge was defective, and where investigation was likely to be rewarded. This peculiar power of feeling for new truths is the first requisite for an original investigator-it is the Forscher'blick 'characteristic of genius with which no amount of industry or plodding work can for an instant compete—and this penetrating glance Faraday possessed in high degree. He was, of course, familiar with the phenomena of ordinary electric induction—namely, that if we rub a stick of sealing wax till it becomes electrified, and then allow it to approach any other body, that body becomes electrified by the mere neighbourhood of the excited sealing wax. He was also familiar with the great discovery, made in 1802, by Romagnosi, although generally attributed to Oersted, who made independently the same discovery in 1820, of the action of an electric current on a magnetic needle, and had repeated all the experiments by which the illustrious Ampère had shown that every magnetic phenomenon then known could be explained by the mutual action of electric currents. Now Faraday had long wished to find out what influence a current of Voltaic electricity passing along a wire exerts upon another wire placed in its neighbourhood, to see whether an induction current' similar in kind to the induction of ordinary electricity could be detected. He failed

VOL. CXXXII. NO. CCLXIX.

in all his first experiments; not a trace of a permanent current could be observed in the neighbouring wire, however near it was brought to the one through which the electricity was passing, or however strong that current of electricity was made to flow. Although Faraday was looking for a continuous current, both his mind and his eyes were open to receive impressions of every kind; and whilst he had started-and necessarily sowith an hypothesis, he was not thereby blinded. Thus when he observed the needle of his galvanometer placed in contact with his wire swing instantly round as he closed the circuit, then come back into its original position and remain there until he broke contact, when it again swung round in the opposite direction, he at once saw that he had discovered Voltaic Induction; and from this and other experiments he concludes, That the battery 'current through the one wire did, in reality, induce a similar 'current through the other, but that it continued for an instant only, and partook more of the nature of the electric wave 'from a common Leyden jar than of the current from a Voltaic 'battery.' The short intermittent wave called into existence by the first passage of the electricity in the other wire is termed the Induced current, and flows in the opposite direction to the primary or inducing current, whilst the wave excited by the cessation of the primary current flows in the same direction as this latter.

6

Imbued with the idea of the close connexion between magnetism and electricity, knowing that Ampère's results showed that electricity can be made to produce all the effects of magnetism, and having himself, ten years before, shown that a moveable current can be made to rotate round a magnet, Faraday now attempted to produce electricity from magnetism. For this purpose he made a hollow coil or helix of wire and brought the ends into contact with a delicate galvanometer; then he plunged inside the coil a permanent magnet. A rush of electricity through the wire of the coil occurred when he inserted the magnet, and a flow in the opposite direction took place when the magnet was removed from the coil. In a similar way he found that a current of electricity was evolved in a coil of wire every time it was made to approach a fixed magnet, and if the coil be made to rotate in front of the two poles of the magnet, a quick succession of alternating waves of electricity is produced. By a long series of experiments carried out with wonderful precision, and varied so as to give him a knowledge of the boundaries of his discoveries, Faraday founded the science of Magneto-electricity, as Romagnosi, Oersted, and Ampère had previously established that of Electro-magnetism. In ten days of experiment these

splendid results were obtained; he collected the facts into the first series of Experimental Researches in Electricity, the publication of which placed him in the first rank of experimental philosophers. Certain portions of Faraday's continuation of his discovery of magneto-electricity illustrate so clearly his power of grappling with and bringing into light the most obscure of natural phenomena, that it may be worth while for a few moments to follow him in the execution of his task. Some time before the period of which we now speak, Arago had observed that when a magnetic needle is made to rotate rapidly on its axis this rotation is quickly stopped when a disc of a non-magnetic metal, such as copper, is held over it-or, if the plate of metal be made to rotate, a suspended magnetic needle placed above or below it began to rotate along with the metallic plate. No one had been able to explain these curious facts. How could a non-magnetic metal influence a magnet? If the disc was motionless not a trace of attraction or repulsion was exerted between it and the needle, hence the effect was in some way caused by the rotatory motion. The solution of this philosophical enigma had been unsuccessfully attempted by many great minds both in France and in our own country. With regard to Arago's position in this matter Faraday writes:- I have always admired the prudence and philosophical reserve shown by M. Arago in resisting the temptation to give a theory of the effect he had discovered, so long as he could not devise one perfect in its application, and in refusing assent to the imperfect theories of others.' Faraday now saw that his two discoveries of Voltaic induction and magneto-electricity only had to be combined in order to explain this enigma. He had proved that whenever a magnet was brought near a metallic conductor a sudden rush of electricity was set up in that conductor, and that, when the magnet was removed, a wave in the opposite direction occurred; hence when the copper disc revolved over the needle, currents must be established by the successive approach and withdrawal of the various parts of the disc, and these currents must deflect the needle. That electricity was really circulating in the rotating copper plate Faraday most beautifully proved experimentally, by connecting it with a galvanometer which became powerfully affected so long as the disc was in motion.

Now he passed from his coils and magnetic needles to observe the action of the earth's magnetism, and was able to produce a current of electricity by a simple unmagnetised bar of iron lifted into a helix, which was placed in the direction of the dip of the earth's magnetism; and he showed further, in accordance