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. [Sidenote: 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.