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FARADAY 31 This long series of researches is an instance of his persist ence. His energy is shown in the way in which he followed up his discovery in the single instance in which he was successful. The first evidence which he obtained of the rotation of the plane of polarization of light under the action of magnetism was on the 13th September 1845, the transparent substance being his ow ? n heavy glass. He began to work on August 30, 1845, on polarized light passing through electrolytes. After three days he worked with common electricity, trying glass, heavy optical glass, quartz, Iceland spar, all without effect, as on former trials. On September 13 he worked with lines of magnetic force. Air, flint, glass, rock-crystal, calcareous spar, were examined but without effect. " Heavy glass was experimented with. It gave no effects when the same magnetic poles or the contrary poles were on opposite sides (as respects the course of the polarized ray), nor when the same poles were on the same side either with the constant or intermitting current. But when contrary magnetic poles were on the same side there was an effect produced on the polarized ray, and thus magnetic force and light were proved to have relations to each other. This fact will most likely prove exceedingly fertile, and of great value in the investigation of the conditions of natural force." He immediately goes on to examine other substances, but with "no effect," and he ends by saying, "Have got enough for to-day." On September 18 he "does an excellent day s work." During September he had four days of work, and in October six, and on Gth November he sent in to the Royal Society the nineteenth series of his " Experimental Researches," in which the whole conditions of the pheno mena arc fully specified. The negative rotation in ferro magnetic media is the only fact of importance which re mained to be discoverer] afterwards (by Verdet in 1856). But his work for the year was not yet over. On November 3 a new horseshoe magnet came home, and Faraday immediately began to experiment on the action in the polarized ray through gases, but with no effect. The following day he repeated an experiment which had given no result on October G. A bar of heavy glass was sus pended by silk between the poles of the new magnet. " When it was arranged, and had come to rest, I found I could affect it by the magnetic forces and give it position." By the Gfch December he had sent in to the Royal Society the twentieth, and on 24th December the twenty-first, series of his " Researches," in which the properties of diamagnetic bodies are fully described. Thus these two great dis coveries were elaborated, like his earlier one, in about threa months. The discovery of the magnetic rotation of the plane of polarized light, though it did not lead to such important practical applications as some of Faraday s earlier dis coveries, has been of the highest value to science, as furnish ing complete dynamical evidence that wherever magnetic force exists there is matter, small portions of which are rotating about axes parallel to the direction of that force. We have given a few examples of the concentration of his efforts in seeking to identify the apparently different forces of nature, of his far-sightedness in selecting subjects for investigation, of his persistence in the pursuit of what he set before him, of his energy in working out the results of his discoveries, and of the accuracy and completeness with which he made his final statement of the laws of the phenomenon. These characteristics of his scientific spirit lie on the sur face of hia work, and are manifest to all who read his writings. But there was another side of his character, to the cultivation of which he paid at least as much attention, and which was reserved for his friends, his family, and his church. His letters and his conversation were always full of whatever could awaken a healthy interest, and free from anything that might rouse ill-feeling. When, on rare occasions, he was forced out of the region of science into that of controversy, he stated the facts, and let them make their own w r ay. He was entirely free from pride and un due self-assertion. During the growth of his powers he always thankfully accepted a correction, and made use of every expedient, however humble, which would make his work more effective in every detail. When at length he found his memory failing and his mental powers declining, he gave up, without ostentation or complaint, whatever parts of his work he could no longer carry on according to his own standard of efficiency. When he was no longer able to apply his mind to science, he remained content and happy in the exercise of those kindly feelings and warm affections which he had cultivated no less carefully than his scientific powers. The parents of Faraday belonged to the very small and isolated Christian sect which is commonly called after Robert Sandeman. Faraday himself attended the meetings from childhood ; at the age of thirty he made public pro fession of his faith, and during two different periods he dis charged the office of elder. His opinion with respect to the relation between his science and his religion is expressed in a lecture on mental education delivered in 1854, and printed at the end of his Researches in Chemistry and Physics. " Before entering upon the subject, I must make one distinction which, however it may appear to others, is to me of the utmost importance. High as man is placed above the creatures around him, there is a higher and far more exalted position within his view ; and the ways are infinite in which he occupies his thoughts about the fears, or hopes, or expectations of a future life. I believe that the truth of that future cannot be brought to his knowledge by any exertion of his mental powers, however exalted they may be ; that it is made known to him by other teaching than his own, and is received through simple belief of the testimony given. Let no one suppose for an instant that the self-education I am about to commend, in respect of the things of this life, extends to any con siderations of the hope set before us, as if man by reasoning could find out God. It would be improper here to enter upon this sub ject farther than to claim an absolute distinction between religious and ordinary belief. I shall be reproached with the weakness of refusing to apply those mental operations which I think good in respect of high things to the very highest. I am content to bear the reproach. Yet even in earthly matters I believe that the in visible things of Him from the creation of the world are clearly seen, being understood by the things that are made, even His eternal power and Godhead ; and 1 have never seen anything incompatible between those things of man which can be known by the spirit of man which is within him and those higher things con cerning his future, which he cannot know by that spirit." Faraday gives the following note as to this lecture : "These observations were delivered as a lecture before His Royal Highness the Prince Consort and the members of the Royal Insti tution on the 6th of May 1854. They are so immediately connected in their nature and origin with my own experimental life, con sidered either as cause or consequence, that I have thought the close of this volume not an unfit place for their reproduction." As Dr Bence Jones concludes " His standard of duty was supernatural. It was not founded on any intuitive ideas of right and wrong, nor was it fashioned upon any outward experiences of time and place, but it was formed entirely on what he held to be the revelation of the will of God in the written word, and throughout all his life his faith led him to act up to the very letter of it." Published Works. Chemical Manipulation, Icing Instructions to Students in Chemistry, 1 vol., John Murray, 1st edition 1827, 2d 1830, 3d 1842 ; Experimental Mcscarches in Electricity, vols. i. andii. , Richard and John Edward Taylor, vols. i. andii., 1844 and 1847; vol. iii., 1844; vol. iii., Richard Taylor and William Francis, 1855 ; Experimental Researches in Chemistry and Physics, Taylor and Francis, 1859 ; Lectures on the Chemical History of a Candle (edited by W. Crookes), Griffin, Bohn, .and Co., 1861 ; On the Various Forces in Nature (edited by "W. Crookes), C lmtto and "Windus (no date). Biographies. Faraday as a Discoverer, by John Tyndall, Long mans, 1st edition 1868, 2d edition 1870 ; the Life and Letters of Faraday, by Dr Bence Jones, secretary of the Royal Institution, in 2 vols., Longmans, 1870; Michael Faraday, by J. II. Gladstone, Ph.D., F.R.S., Macmillan, 1872. (J. C. M.)