CHAPTER III.
SCIENTIFIC RESEARCHES: FIRST PERIOD.
From first to last the original scientific researches of Faraday extend over a period of forty-four years, beginning with an analysis of caustic lime, published in the Quarterly Journal of Science in 1816, and ending with his last unfinished researches of 1860 to 1862, on the possible existence of new relations between magnetism and gravity and between magnetism and light. The mere list of their titles fills several pages in the catalogue of scientific papers published by the Royal Society.
For convenience of description, these forty-four years may be divided into three periods: the first lasting from 1816 to 1830, a period of miscellaneous and in some respects preliminary activity; the second from 1831 to the end of 1839, the period of the classical experimental researches in electricity down to the time when they were temporarily suspended by the serious state of his health; the third from 1844, when he was able to resume work, down to 1860, a period which includes the completion of the experimental researches on electricity, the discovery of the relations between light and magnetism, and that of diamagnetism.
RESEARCHES BEGINNING.
Faraday’s first research was an analysis for Sir Humphry Davy of a specimen of caustic lime which had been sent to him by the Duchess of Montrose from Tuscany. The Quarterly Journal of Science, in which it appeared, was a precursor of the Proceedings of the Royal Institution, and was indeed edited by Professor W. F. Brande. Faraday frequently wrote for it during these years, and took editorial charge of it on more than one occasion during Brande’s holidays. The paper on caustic lime was reprinted by Faraday in the volume of his “Experimental Researches on Chemistry and Physics,” prefaced by the following note:—
I reprint this paper at full length; it was the beginning of my communications to the public, and in its results very important to me. Sir Humphry Davy gave me the analysis to make as a first attempt in chemistry, at a time when my fear was greater than my confidence, and both far greater than my knowledge; at a time also when I had no thought of ever writing an original paper on science. The addition of his own comments, and the publication of the paper, encouraged me to go on making, from time to time, other slight communications, some of which appear in this volume. Their transference from the Quarterly into other journals increased my boldness, and now that forty years have elapsed, and I can look back on what successive communications have led to, I still hope, much as their character has changed, that I have not either now or forty years ago been too bold.
For the next two or three years Faraday was very closely occupied in the duties of assisting Sir Humphry Davy in his researches, and in helping to prepare the lectures for both Davy and Brande. Yet he found time still to work on his own account. In 1817 he had six papers and notes in the Quarterly Journal of Science, including one on the escape of gases through capillary tubes, and others on wire-gauze safety lamps and Davy’s experiments on flame. In 1818 he had eleven papers in the Journal; the most important being on the production of sound in tubes by flames, while another was on the combustion of the diamond. In 1819 he had nineteen papers in the Quarterly Journal, chiefly of a chemical nature. These related to boracic acid, the composition of steels, the separation of manganese from iron, and on the supposed new metal, “Sirium” or “Vestium,” which he showed to be only a mixture of iron and sulphur with nickel, cobalt, and other metals.
OERSTED’S DISCOVERY.
The year 1820 was marked in the annals of science by the discovery, by Oersted of Copenhagen, of the prime fact of electromagnetism, the deflexion which is produced upon a magnetic needle by an electric current that passes either under or over the needle. Often had it been suspected that there must be some connection between the phenomena of electricity and those of magnetism. The similarities between the attractions and repulsions caused by electrified bodies, and those due to the magnet when acting on iron, had constantly suggested the possibility that there was some real connection. But, as had been pointed out centuries before by St. Augustine, while the rubbed amber will attract any substance if only small or light enough, being indifferent to its material, the magnet will only attract iron or compounds of iron, and is totally inoperative[16] on all other substances. Again, while it had been noticed that in houses which had been struck by lightning knives, needles, and other steel objects near the path of the electric flash had become magnetised, no one had been able, by using the most powerful electric machines, to repeat with certainty the magnetisation of needles. In vain they had tried to magnetise knives and wires by sending sparks through them. Sometimes they showed a trace of magnetism, sometimes none. And in the cases where some slight magnetisation resulted, the polarity could not be depended upon. Van Swinden had written a whole treatise in two volumes on the analogies between electricity and magnetism, but left the real relation between the two more obscure than ever. After the invention, in 1800, of the voltaic pile, which for the first time provided a means of generating a steady flow or current of electricity, several experimenters, including Oersted himself, had again essayed to discover the long-suspected connection, but without success. Oersted was notoriously a poor experimenter, though a man of great philosophical genius. Having in 1820 a more powerful voltaic battery in operation than previously, he repeated[17] the operation of bringing near to the compass needle the copper wire that conveyed the current; and, laying it parallel to the needle’s direction, and over or under it, found that the needle tended to turn into a direction at right angles to the line of the current, the sense of the deviation depending upon the direction of flow of the current, and also on the position of the wire as to whether it were above or below the needle. A current flowing from south to north over the needle caused the north-pointing end of the needle to be deflected westwards. If the wire were vertical, so that the current flowed downwards, and a compass needle was brought near the wire on the south side, therefore tending under the earth’s directive influence to point northwards toward the wire, it was observed that the effect of the current flowing in the wire was to cause the north-pointing end of the needle to turn westwards. Or, reversing the flow of current, the effect on the needle was reversed; it now tended eastwards. All these things Oersted summed up in the phrase that “the electric conflict acts in a revolving manner” around the wire.[18] In modern phraseology the whole of the actions are explained if one can conceive that the effect of the electric flow in the wire is to tend to make the north pole of a magnet revolve in one sense around the wire, whilst it also tends to make the south pole of the magnet revolve around the wire in the other sense. The nett result in most cases is that the magnetic needle tends to set itself square across the line of the current. Oersted himself was not too clear in his explanations, and seems, in his later papers, to have lost sight of the circular motion amidst repulsions and attractions.