[ 545 ] 



LXIII. Notices respecting New Boohs. 



Elementary Mechanics, including Hydrostatics and Pneumatics, 

 Revised Edition. By Oliver J. Lodge, D.Sc. London, Professor 

 of Experimental Physics in University College, Liverpool. London 

 and Edinburgh : W. and E. Chambers. 1885. 



TV/' HEIST the first edition of this little book appeared, those who 

 ' * knew the tendencies of the time in the teaching of Mechanics 

 were bold to predict for it a certain and speedy success. The call 

 for a new and revised edition is the evidence that these prophets 

 were right, and that the demand for sound, clear, elementary expo- 

 sition of the essential laws of matter and motion is a genuine and 

 growing one. Thomson, Tait, Maxwell, and Clifford took a fresh 

 look at the old and well-worn principles, and presented them to us 

 in a fashion that was implicitly full and complete as well as novel. 

 But their language is not that of the people — of the school-boy, of 

 the artizan-stud >nt, of the young engineer ; and even the trained 

 mathematician finds that their terse statement does not reveal all 

 its meaning and all its bearing at the first glance. Maxwell's 

 4 Matter and Motion ' is the best example : his booklet of text 

 would require a volume of commentary to develop its entire sig- 

 nificance ; and so while it gives practised readers all the delight of 

 severe healthful exercise, it is virtually sealed to the tyro. Some 

 work was wanted, then, which should lay open in ordinary language 

 what was hidden in the works of the masters. To do this without 

 sacrificing a jot of precision, without blurring by over- or under- 

 statement the sharp definition of the originals, without intruding 

 misleading illustrations intended to be vivid, without practising the 

 easy device of simplifying difficulties by evading them, itself requires 

 a kind of masterhood ; and this we think Professor Lodge to a 

 great extent in the first edition, to a greater extent in this second, 

 has come very near to indeed. 



He has a happy audacity which in work of this kind is almost 

 genius : at any rate it gives the capacity of " taking a fresh look " 

 which talent often lacks, especially the talent of talented textbook- 

 writers. They have told us for generations that "force is that 

 which tends to produce motion," and that word " tends" covered 

 with its five letters a very chaos of doubts and difficulties to the 

 hapless beginner who thought. The word " force ?? was made more 

 mysterious by its definition. Lodge cuts the metaphysical knot, 

 and sends the student straight to the concrete by telling him that 

 " by the term force we are to understand muscular exertion, and 

 whatever else is capable of producing the same effects " (p. 13). 

 Again, after a brief and clear investigation of the normal accelera- 

 tion of a point moving in a circle, that intangible phantom to the 

 beginner, we are told — "Although the point is always gaining velo- 

 city normal to the curve or along its radius at this rate, it does not 

 follow that it ever possesses any such velocity. It is in fact impos- 

 sible for a point to possess any velocity except that along the curve 



