Notices respecting JSeic Boohs. 645 



TJie Teaching of Elementary Mechanics. Discussion at Johannes- 

 burg at the Meeting of the British Association, 1905. Edited 

 hy John Peeey. London : Macniillan & Co. 1906. 



Having- read this book, the predominant feeling in our minds is 

 best expressed in the wish uttered by Sir David Gill : that he 

 had been born fifty years later and could have been taught 

 mechanics by more rational methods. The trouble we had over 

 " g," over the pound of matter and pound force and pound 

 of inertia ! There were no experiments to help us. Sir Robert 

 Ball's ' Experimental Mechanics ' was indeed available, but few 

 then made use of it. We w 7 ho write believe in the experi- 

 mental method of teaching above all things ; only we should not 

 classify the levers into orders and confuse and burden the mind 

 ■ with details. But inertia, acceleration, weight and force, kinetic 

 energy, should in this way be introduced. " Begin with the 

 things themselves*' as the President (Professor Forsyth) observes. 

 After that, whether or not a man acquires, for instance, an 

 adequate mental impression of what inertia is, depends a great 

 deal more on the man himself than upon his teachers. I do not 

 believe doubtful definitions will make a clear head go wrong or 

 influence a thoughtful student injuriously. In most cases the 

 student gains by having to form his own mental picture and not 

 receiving too much in the way of carefully prepared definitions. 

 The mere fact that there can be so much difference of expert 

 opinion over (e. g.) the utility of the term " poundal," suggests 

 that all minds are not alike in these matters. If so, a certain 

 degree of liberty should certainly be left to the student : 

 "poundal" may be useful to one student and not to another. 



But we must not depart from our duty as reviewer of a valuable 

 book, which may be read with pleasure and profit by teachers and 

 thinkers. Thanks are due to Prof. Perry for leading this useful 

 discussion. Our remarks above are by no means intended to 

 decry its usefulness. There should, of course, be agreement 

 among teachers when once the best methods of teaching are 

 arrived at, and such a discussion as we have just read is the 

 surest way of arriving at a knowledge of the best methods of 

 teaching. 



Hermann von Helmlioltz. By Leo Koenigsbebgee. Translated 

 by Eeances A. Welbv. With a Preface by Lord Kelvix. 

 Oxford : at the Clarendon Press. 1906. 



The English translation of Professor Leo Koenigsberger's Life 

 of Helmholtz is certain to be welcomed by English readers. The 

 work of translation has been excellently done. There is added an 

 interesting preface by Lord Kelvin. 



We have already referred at some length to the original 

 German edition of this book, and it is hardly requisite to refer in 

 detail to the contents of the English version, more especially in view 

 of the commendation which the German work received on every 

 side. In the biography are admirably blended and interwoven the 

 episodes of life in its more material aspect and the mental or 



