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 he was at once offered a position in that establishment. His election to the appointment which he now holds, of Professor of Natural Philosophy at the Royal Institution, was unanimously made in June, 1853. The first three years of his residence in London he devoted to an exhaustive investigation of diamagnetism, the results of which were published in various memoirs that have since been collected in a volume.

Prof. Tyndall was first attracted to the Alps in 1849, for the sole object of healthful recreation and exercise. But he could not be long in the presence of the grand physical phenomena there displayed without becoming interested in the scientific questions they present. Accordingly, for more than twenty years, the Alps have served the double purpose to Prof. Tyndall of physical and mental reinvigoration, after being run down by his London work; and, at the same time, they have furnished him with a series of the most interesting scientific problems. In company with his friends Prof. Huxley and Prof. Hirst (an old and favorite pupil of Tyndall's, and to whom he dedicated his "Hours of Exercise in the Alps"), and often alone, usually in summer, but sometimes in winter, he has climbed the mountains and explored the Glaciers, to clear up the various questions that have arisen, and extend our knowledge of the subject. The description of his adventures and the results of his researches were embodied in his volume on "The Glaciers of the Alps," but which is now out of print. The reader will, however, find the records of adventure, and the results of study in the mountains, embodied in the "Hours of Exercise," published last year, and in a neat little volume on the "Forms of Water," now just issued from the press.

As we remarked last month, Prof. Tyndall's proclivity is for philosophic physics, and all his various lines of research, since he began in the Marburg laboratory, twenty-four years ago, have converged upon the great question of the molecular constitution of matter. The different forces of Nature, and the several divisions of physics, can only be brought into scientific harmony as they are harmonized in Nature, by arriving at some clear understanding of the common constitution of matter and how it is related to the action of forces. Prof. Tyndall has been a profound student of the correlation of these forces, and of the mechanism of that material substratum through which they are manifested. Taking up matter in its free or vaporous condition, his chief problem has been to explore or to sound it by the action of the radiant forces. In his work on "Heat as a Mode of Motion," published in 1863, he develops that modern view of the nature of heat which involves a molecular conception of the bodies displaying it. The results of his original researches into the relations of radiant heat to gases and vapors are there summarized, and his full memoirs upon these investigations have just been published in a companion volume to the work on diamagnetism. His interesting little volume on "Sound," although not designed as a statement of original work, takes up the subject of