152 THE CANADIAN NATURALIST. [April 



Count Kumford and his Researches on Heat. — The 



highest law in physical science which our faculties permit us to 

 perceive, is, to quote the words of Faraday, " the Conservation of 

 Force." The generalizations which serve to illustrate this great 

 principle of the conservation of force in all its varied applications, 

 are generally referred to as the law of the Correlation of Forces, 

 and have been set forth by various writers within the last twenty 

 years. Prof. Youmans, who is already favorably known for his 

 new Class-book of Chemistry, — a work which deserves, by its lucid 

 method, scientific accuracy, and felicity of illustration, to super- 

 sede all others as an elementary manual, — has just rendered an 

 important service to the scientific student by bringing together in 

 a single volume a series of expositions of this doctrine of the 

 correlation and conservation of force, * by Grove, Helmholtz, 

 Mayer, Faraday, Liebig, and Carpenter. With the exception of 

 the first named, a treatise of considerable extent, and of great merit, 

 which has gone through at least two editions, and the wonderful 

 essay of Mayer on Celestial Dynamics, the productions here col- 

 lected are scattered through scientific journals not always accessible 

 to the general reader. Besides bringing them together with notes, 

 explanatory remarks, and a good index, Dr. Youmans has, in a 

 modest introduction of forty pages, given a review of the subject, 

 and has called attention to the labor of that most remarkable 

 thinker of our day, Herbert Spencer, who, to use our author's 

 words, " has the honor of crowning this sublime inquiry by show- 

 ing that the law of conservation, or, as he prefers to call it, of the 

 Persistence of Force, as it is the underlying principle of all being, 

 is also the fundamental truth of all philosophy." 



It would have added to the value of this excellent compilation 

 if our author had included in it the essay of Dr. Joseph Henry, on 

 the Conservation of Force, published in the Agricultural Report of 

 the United States Patent Office for 1857, and in Silliman's Jour- 

 nal [2] , xxx, 32 ; and Dr. Joseph Leconte's exposition of the 

 Correlation of Physical, Chemical, and Vital Forces, and of the 

 Conservation of Forces in Vital Phenomena, which appeared in the 

 same Journal [2], xxviii, 305. A valuable, and in many respects, 



* The Correlation and Conservation of Forces : a series of expositions 

 by Prof. Grove, Prof. Helmholtz, Dr. Mayer, Dr. Faraday, Prof. Liebig, 

 and Dr. Carpenter. With an introduction and brief biographical notices 

 of the chief promoters of the new views : by Edward L. Youmans, M.D. 

 New York: D. Appleton & Co. Montreal: Dawson Brothers. 



