About the year 1822 and for some time after he investigated the subject of the liquefaction of vapors and gases, and in 1823 examined a substance which had been regarded as pure chlorine, but which Davy in 1810 had proved to be a hydrate. Faraday first analyzed this hydrate, and then at the instance of Davy subjected it to the action of its own pressure on being heated in a strong sealed tube, by which means he obtained liquid chlorine. Extending his experiments to other gases, he succeeded in reducing a number of them to a liquid state. His first memoir was read before the royal society April 10, 1823, and the second on Dec. 19, 1844. Prof. Tyn-dall says that while making his first series of experiments an explosion occurred by which 13 pieces of glass were driven into his eyes. In 1825 he published a paper in the "Philosophical Transactions" on new compounds of carbon and hydrogen, in which he announced the discovery of benzole. But his mind continually reverted from chemistry to physics, and in 1826 he was again engaged upon the subject of vaporization, in which he came to the conclusion that a limit exists, and that our atmosphere does not contain the vapors of what are usually denominated the fixed constituents of the earth's crust.

During the year he had ten papers in the "Quarterly Journal," one of the principal being on pure caoutchouc, his analysis of which is given in the article on that substance in this work. In 1825 Faraday was appointed with Sir John Herschel and Mr. Dolland on a committee to examine the manufacture of glass for optical purposes. Their experiments continued for four years, when Faraday delivered his first Bakerian lecture "On the Manufacture of Glass for Optical Purposes." This paper required three successive sittings of the royal society, and although the investigation had not much immediate practical use, it led to other and very important discoveries. In 1831 he published a paper on vibrating surfaces, in which he solved the problem of the cause of the collection of lyco- I podium seeds and other light bodies upon the vibrating parts of sounding plates, instead of upon the nodal lines where sand is collected, by showing that the light bodies are prevented i from settling on the nodal lines by minute whirlwinds formed in the air over the vibrating parts.

In 1827 he published his "Chemical Manipulations (1 vol. 8vo; 2d ed., 1830; 3d ed., 1842). In April of this year he gave his first course of six lectures before the royal institution upon the atmosphere, gases, vapor, chemical affinity, definite proportions, flame, galvanism, and magnetism as evolved by electricity. Between February and May he delivered twelve lectures at the London institution on the subject of chemical manipulation. In December he commenced a course of lectures on chemistry to juvenile audiences. His power of imparting the elementary principles of science to youthful minds was wonderful, owing not only to the logical simplicity of his mind, but to his happy choice of and manner of making experiments. These courses of lectures succeeded each other from year to year, and it was also his habit to deliver popular lectures on Friday evenings at the royal institution throughout nearly his whole scientific career. In 1829 he was appointed lecturer on chemistry in the royal academy at Woolwich. In 1831 he commenced his celebrated series of electrical researches, which were continued through a great number of years.

He investigated the induction of electric currents and the evolution of electricity from magnetism; and although Oersted was the discoverer of electro-magnetism, and Ampere its expounder, Faraday made the science of magneto-electricity substantially what it is at the present day. In this year he also began to develop his theory of lines of magnetic force. In 1833 he was appointed the first Fullerian professor of chemistry at the royal institution, and during the same and the succeeding year he studied the laws of electro-chemical decomposition, and applied the word electrode in place of pole to the conductors connected with a decomposing cell, the fluid in which he called an electrolyte, and the act of its decomposition electrolysis. The positive electrode he called the anode, and the negative the cathode, and also applied the terms anions and cations to the chemical elements of the electrolytes which pass respectively to the anode and cathode. He now applied himself to the determination of electric quantity, and for this purpose devised his voltameter, by which he showed that the amount of electricity generated in a voltaic battery depends upon the amount of chemical decomposition, thus establishing the doctrine of "definite electro-chemical decomposition." He investigated-the contact theory of Volta, and in doing so developed the ideas which he always afterward entertained on the conservation of force, illustrating the fallacy of the contact theory of galvanism by showing that if true a force could be produced without drawing its supply from any consuming source.

His first great paper on frictional electricity was sent to the royal society Nov. 30, 1837. In his investigation of this subject he developed his inductive theory of electricity, and by numerous memorable experiments illustrated the specific inductive capacity" of dielectrics, in which he supposed the molecules of the dielectric to form a chain of communication between the inducing and the induced body. He also, during the years 1836-'8, made experiments for the Trinity house on electric light for lighthouses, a subject which again in the latter part of his life engaged much of his attention. In 1840 he was elected an elder in the Sandemanian church, but held the office only for 3 1/2 years, during which period, when in London, he preached on alternate Sundays. His great labors had impaired his health, and in 1841 he went with his wife to Switzerland, spending much of the time at Interlaken and at the falls of Giessbach, returning at the end of September in the same year. In 1842 he made experiments upon the generation of electricity by steam, prompted thereto by the invention of the celebrated hydro-electric machine of Sir William Armstrong, and showed that it was caused by friction, and not by vaporization, as had been supposed.