350 Notices respecting New Boohs. 



Here, then, " Force " is used in the ordinary sense of " Attractive 

 Force," bat "Energy" in a sense wholly different from its usual 

 and accepted meaning, the power of doing work, the result and 

 equivalent of the ivork done on the body in which the energy is 

 said to reside. It may be remarked that Mr. Grant Allen's new 

 theory ignores tuorJc and momentum wholly. Instances adduced in 

 illustration of the above novel definition of Energy are, that " the 

 Moon is prevented from falling upon the Earth and the Earth from 

 falling into the Sun by the Energy of their respective orbital mo- 

 tions;" and that "a ball shot from a cannon into the air is pre- 

 vented from falling by the Energy of its upward flight." Now 

 if in these instances for "Energy" is substituted its new definition, 

 'a Power accelerating separative motion from the Earth " (or Sun), 

 the total irreconcileableness of the "theory" with what is well 

 known is at once apparent. If Mr. Allen had contemplated the 

 case of the gun being pointed from above downwards (say from 

 the "fighting-top" of a ship's mast upon boarders on deck) he 

 must have seen himself that the Energy of the shot would have 

 been the same in amount as before, but its effect would have been 

 "aggregative" in his sense; while the smaller Energy of the gun 

 itself would have been "separative." 



In these and such cases Mr. Allen fails altogether to realize the 

 conditions of the problem ; but in mere descriptions of phenomena 

 (which occupy the greater part of the book) the facts are correctly 

 stated with characteristic lucidity and charm of style*. If therein, 

 with the alteration of a word or phrase occasionally, Energy were 

 understood in its accepted sense all would be "just what was 

 already known and universally acknowledged." Much that may 

 have appeared to Mr. Allen as he wrote to plausibly support his 

 notion of a " separative Power " (in a retrospective sentence at the 

 opening of the concluding chapter is reiterated " our theory of two 

 opposing Powers, aggregative and separative ") is perhaps due to the 

 selection of instances wherein disintegration is an attendant cir- 

 cumstance : thus (p. 118) the Energy of the prime mover in the 

 water- or wind-mill is ultimately given up " partly in producing 

 separation, in opposition to cohesion, among the molecules of corn." 

 It does not seem to have occurred to Mr. Allen that it might, by a 

 slight change of mechanism, have been employed in working a 

 small hammer which should have produced the opposite effect 

 among the " molecules" of a bar or rod of iron. 



A tolerably good idea of what the book is as a whole might be 

 derived from the supposition that Mr. Grant Allen had proposed 

 to himself to rewrite the late Balfour Stewart's ' Conservation of 



* Exception being made of occasional lapses into the u slipshod," such 

 as the following found in chap. v. of part ii. : — '• so soon as we apply 

 heat to eithe:, they burn away ' : "it is probable that they spontaneously 

 decompose .... on any direct contact with external agencies^ An 

 instance of lapse into incorrectness occurs in chap. viii. : (the Earth's) 

 " orbital Energy and nutation which indirectly yield the phenomena of 

 winter and summer ; " where the inclination of the plane of the orbit to 

 that of the Equator is evidently meant. 



