Reviews aiid Notices of Books. 



141 



The First Principles of Natural Philosophy. By W. T. 

 Lynn. London : Van Voorst, 1863. 



This is in many respects a creditable little work — totally dis=- 

 tinct in kind from the peculiar absurdities produced by the 

 Reddie and Worms school of self-constituted philosophers. 



To some of its errors, which, we must say, are attributable to 

 those of more pretentious treatises, we shall presently advert. 

 But we allow that the author expresses himself well and clearly 

 on many points, and that his treatise is so far what it was in- 

 tended to be — a very simple guide to the first elements of 

 Mechanics and Optics. 



In some cases he has shown considerable acuteness, though 

 only brought into action by his want of knowledge. Thus his 

 remark, p. 40, about intensity of motion, though quite wrong, 

 shows that he has an idea of Vis viva as distinguished from 

 Momentum. 



The author has, however, followed too closely authorities 

 whose value is really much less than is generally believed ; such 

 as the bulk of the Cambridge and Dublin Text-Books. Most, we 

 may almost say all, of these — are admirable in their mathematical 

 development : but there is, in general, a fearful amount of loose- 

 ness, and even inaccuracy, whenever first principles or experimental 

 results are concerned. 



Thus Mr Lynn says (p. 20), 



"It is at once apparent that if a force acts continuously on a body, 

 it will generate in that body a continually increasing motion." 



He has not, so far as we can see, added the proviso that the force 

 must not act at right angles to the direction of motion. 



Again (in pp. 20, 22) he speaks of a constant, as distinguished 

 from an impulsive, force — meaning by the erroneous first term a 

 coritinuously acting force. He seems also (in p. 23, for instance) 

 to fancy that an accelerating force must be of constant magnitude. 

 In the same page, after giving an exceedingly good and complete 

 investigation of the space described from rest by a body in any 

 time, when acted on by a uniform force in its line of motion, he 

 seems to be dissatisfied with his work — for he goes on to say, 



" This proposition is so important and fundamental that it will be 

 proper to give a strict demonstration of it." 



Then he goes on with limits, and limiting ratios, as if to make 

 doubtful to the beginner, in 4 pages, what he has just before 

 satisfactorily proved (by general reasoning) in 8 lines. 



