﻿192 Canadian Record of Science. 



Nor is the matter unworthy of its presentment. It is written 

 throughout with direct reference to practical things on the one hand, 

 and to scientific principles and the method of establishing them 

 by experiment on the other. Very properly a thorough account of the 

 mechanics of visible bodies, and the properties of matter is made 

 the basis of the other branches of Physics, and occupies no less 

 than 228 pp. out of the whole 544 pp. The whole subject, including 

 the introductory mechanics, is treated in a very fresh and interesting 

 manner. Much information not usually found in Text-books of 

 Physics {e.g., the capital account of meteorology) is given. The 

 numerous examples interspersed between the sections are mostly new, 

 and drawn from practical life. It is justly remarked in the preface 

 that "the reputation of the several contributors, and the standing of the 

 great scientific schools which they represent, must seciire for this work 

 a consideration accorded to few American school-texts." We think that 

 the general merits of the book will assure the fulfilment of this 

 prophecy, and as it is important that a book which is to be widely 

 used should be as perfect as possible, we shall without further 

 description of the general features of a work which every teacher 

 of physics should see for himself, employ the rest of our space in 

 pointing out certain blemishes which could hardly fail to arise in 

 an attempt to re -write freshly such familiar subjects as Mechanics and 

 Physics. 



The attention of teachers is called in the preface to the " thorough 



and original treatment of motion, energy, force, and work 



These subjects are treated with the greatest simplicity, precision, and 

 thoroughness, for it is believed that a proper understanding of them 

 lies at the base of all scientific knowledge, however far it may be 

 pursued." It is as difficult as it is important to write with simplicity 

 and precision on elementary mechanics, especially when any attempt is 

 made at originality of treatment ; and on this account most of 

 the criticisms we have to make will be directed against the earlier part 

 of the book. 



We will note first some faults of precision. In the preliminary 

 statements and definitions (which seem to us rather advanced in 

 character compared with succeeding chapters) occurs the statement 

 (p. 8) that "all our knowledge of time and space is, therefore, 

 essentially relative,'" by which is meant that we can only define 

 one point of time or space by reference to some other. This is not the 

 usual meaning of the word relative, as applied to knowledge in 

 philosophy. Nor is it correct to define (p. 12) any body as homogeneous, 

 when it is of the same density in all its parts. Velocity is stated (p. 18) 

 to be the ratio of the distance travelled to the time occupied. But 

 ratios are only between like things. On p. 16 a distinction is formally 

 drawn between uniform and constant. But on pp. 18, 20, 24, 26, 28, 



