io6 THE POPULAR SCIENCE MONTHLY. 



he was at once offered a position in that establishment. His election 

 to the appointment which he now holds, ol' Professor of Natural Phi- 

 losophy at the Royal Institution, was unanimously made in June, 1853. 

 The first three years of his residence in London he devcted to an ex- 

 haustive investigation of diamagnetism, the results of which were pub- 

 lished 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 with- 

 out becoming interested in the scientific questions they present. Ac- 

 cordingly, 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 some- 

 times in winter,' he has climbed the mountains and explored the Gla- 

 ciers, to clear up the various questions that have arisen, arid 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 philo- 

 sophic 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 differ- 

 ent 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 mani- 

 fested. 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 in- 

 volves 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 investi- 

 gations 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 



