Jan. 24, 1889] 



NA TURE 



291 



' must be carefully distinguished from the opposite 

 principle of the Conservation of Energy." 



From the examples given it appears that the author 

 means by "the persistence of force" the universal pre- 

 valence and unalterable character of gravitation. This, if 

 you please, is a principle " opposite " to the " conservation 

 of energy." 

 f It may be asked how on earth the author manages to 



y make out any doctrine of conservation for what he is 

 * pleased to style " Energy." It maybe asked, but scarcely 

 answered. First, there is a momentous difference of 

 language to be attended to, a diflerence of which we are 

 told the concrete and practical results are enormous. 

 " While Forces persist, Energies are conserved^ This is 

 a most satisfactory beginning, and makes one feel quite 

 smooth and comfortable. But unfortunately the author 

 is net original in the rest of this chapter, and his illustra- 

 tions of conservation of energy do not flow from his 

 definition, but are quite common-place. I cannot resist 

 one little extract from this chapter wherein the property 

 of " inertia " has an altogether new light thrown upon it, 

 a light even more brilliant than that just thrown upon 

 *'■ friction." 



" Two molecules of water vapour are prevented from ag- 

 gregating under the relatively feeble attraction of cohesion 

 at a distance, by their inertia— that is, by the relatively 

 strong cohesion of surrounding or intervening matters (just 

 as a mass on a table is prevented from aggregating with 

 the earth by the cohesion of its boards). Two atoms 

 having affinities for one another are similarly prevented 

 from aggregating by inertia. ... So also two electrical 

 units are prevented from aggregating in the Leyden jar 

 by the electrical neutrality of the glass partition." 



Chapter X., " The Indestructibility of Power," asserts 

 that 



" the total amount of Power, aggregative or separa- 

 tive, in the Universe is constant, and no Power can ever 

 disappear or be destroyed. This sums up the two pre- 

 ceding generalizations of the Persistence of Force and the 

 Conservation of Energy in one still wider generalization." 



•Chapter X. is very short. 



The chapter on " Liberating Energies " is a dissertation 

 on pulling a trigger, and quite mistakenly supposes that 

 some expenditure of energy is essential to the performance 

 of this act. 



'' A ball suspended by a thread is released by the 

 separative Energy of a knife or scissors." 



The separative Energy of a knife is a good phrase. 



" The stronger Force necessarily outweighs the weaker, 

 and as Forces cannot increase or decrease in intensity, the 

 only manner, &c.'' 



Forces cannot increase or decrease in intensity ? No, 

 certainly not ; this is proved by the existence of the 

 phrase "persistence of force." Well, this is logical, at 

 any rate, after the bookish manner of argument, and 

 that is some comfort. 



" Electrical Liberating Energies are those which re- 

 lease Electrical Units from the interference of a Force 

 antagonistic to Electrical Affinity." 



" They are such as close the circuit of a battery, or 

 bring a discharging tongs to a Leyden jar." 



" The usual vagueness of electrical science prevents any 

 definite treatment of these phenomena." 



Are we, then, to conclude that the author, in all this 

 treatise, has hit on no germ of truth — nothing but what 

 was well known before, or what is erroneous ? I fear that, 

 with the possible exception of the idea of classifying 

 energies by reference to the sizes of the bodies concerned, 

 this must be our conclusion. He has regarded the uni- 

 verse from the point of view of action at a distance, 

 and has been struck with one or two salient features : 

 (i) the universality of gravitation at great distances, and 

 of cohesion at small ; (2) the existence of what has been 

 styled " repulsive motion " — that is, a motion which simu- 

 lates the effects of repulsion, as when two particles or 

 two molecules, rushing together, swing each other round 

 and separate again ; or when a heated gas expands. One 

 knows that, in old text-books, heat was often spoken of 

 as a repulsive force. And a sufficient velocity imparted 

 to a satellite does keep it clear of the earth. 



Struck with these facts, he has proceeded to take 

 gravitative separation as the typical and fundamental 

 form of energy ; motion being a form of energy only 

 because it tends to separation (in some cases, at any rate), 

 so that he defines motion, in the last chapter of Part I., 

 as " the redistribution of separations," while energy he 

 defines as "a Power which separates." On the other 

 hand, he has taken gravitation and cohesion as his typical 

 forms of force ; and, because these tend to pull bodies 

 together, he has defined force as " a Power which aggre- 

 gates," and has proceeded to write a treatise on the 

 subject, showing how force and energy are opposed to 

 one another. 



The thing which strikes one most forcibly about the 

 physics of these paper philosophers is the extraordinary 

 contempt which, if they are consistent, they must or 

 ought to feel for men of science. If Newton, and La- 

 grange, and Gauss, and Thomson, to say nothing of 

 smaller men, have muddled away their brains in concoct- 

 ing a scheme of dynamics wherein the very definitions 

 are all wrong ; if they have arrived at a law of con- 

 servation of energy without knowing what the word 

 energy means, or how to define it ; if they have to be 

 set right by an amateur who has devoted a few weeks or 

 months to the subject, and acquired a rude smattering 

 of some of its terms, — what intolerable fools they must 

 all be ! 



But this does seem the attitude of many literary 

 men, and that must be one reason why they dislike 

 and despise science. If such a view were just or true, 

 dislike and contempt would be the only reasonable 

 attitude. 



A scientific man may often feel harassed by being 

 unable to express in literary form what he has to say ; 

 but, though this is an evil, it is surely a lesser evil than 

 to have the knack of writing and no matter to write. It 

 is as when the Sophists proceeded to teach rhetoric, 

 heedless of whether either their pupils or themselves 

 possessed any real knowledge about which to be eloquent. 



Mr. Grant Allen has apologized for his Mistake in the 

 preface, and one has no quarrel with him. One might, if 

 it were worth while, have a quarrel with a certain class of 

 literary men for the shallow and flippant way in which 

 they occasionally refer to Science; but it is not worth 

 while. 



The disciple is not above his master in this respect. 



