June 1, 1888.] 



♦ KNOWLEDGE ♦ 



171 



Nay to be perjured, which is worst of all ; 



And, among three, to love the worst of all ; 



A whitely wanton with a velvet brow \_relfi't for blacli] 



With two pitch balls stuck in her face for eyes. 



And I to sigh for her 1 to watch for her ! 



To pra)' for her 1 Go to : it is a plague 



That Cupid will impose for my neglect 



Of his almighty dreadful little might. 



Compare with this the self-drawn Shakespeare of the 

 later .'^onnets, and it will at least be seen that, in attributing 

 something of Biron's weakness for dark-browed, black-eyed, 

 ]iale-faced women to the poet himself, we do not wrong him. 

 Even the strange charm which Biron seems half to admit 

 that he finds in the suggestion that Eo.saline is amorous 

 (" Ay, and by heaven," etc.) Shakespeare found in the dark 

 lady of the sonnets : — 



When my love swears that she is made of truth, 

 I do believe her though I know she lies. 



O, love's best habit is in seeming trust, i:c. 

 For the rest, the whole story of " Love's Labour's Lost" 

 speaks of Shakespeare's loving recollection of the fair scenes 

 and forest life of Stratford and Charlecote I From the first 

 scene ("a Park with a Palace in it," but a palace into which 

 none of the characters enter), through all the others (always 

 " another part of the Park "), to the last songs of Spring and 

 Winter, the whole play is full of English country ways and 

 sylvan life. 



FORCE AND ENERGY. 



N his otherwise capital work, " The Stoi-y of 

 Creation " — the main portion of which ap- 

 paared, bj' the way, in these pages — my friend, 

 Mr. Clodd, continues his use of the word 

 " force " to represent attraction, and " energy " 

 to represent repulsion. But he gives reasons 

 for the adoption of this incorrect usage which 

 serve to show how it had its origin in the entire misap- 

 prehension by others of the actual use of the terms " force " 

 and " energy " in books properly described as scientific : — 



" In attempting," he says, " to give a clear idea of the mechanism 

 of the universe, I have felt the difficulty expressed years ago by 

 such authorities as Sir W. R. Grove and Professor Tyndall, arising 

 from the lack of precision in standard books on physics in the use 

 of the terms ' force ' and ' energy.' When talking over this matter 

 with my friend Grant Allen, I was delighted to find that he had 

 published (although privately) a pamphlet on the subject, in which 

 rigid and definite meanings are given to ' force ' and ' energy ' as 

 the twofold and opposite forms of power manifest through matter ; 

 and in that sense, as affording the reader a clearer conception of 

 cosmic dynamics, those terms are used throughout this book." 



In the body of the book (p. 13) Mr. Clodd gives these 

 " rigid and definite meanings " (their rigidity and definite- 

 ness are, indeed, unmistakable), which will rather raise 

 the eyebrows of the scientific students of dynamics, espe- 

 cially when considered in connection with his purpose of 

 clearing his readei's' conceptions. They run as follows : — 



(a) Force is that which produces or quickens motions binding 

 together two or more particles of ponderable matter, and which 

 retards or resists motions tending to separate such particles. 



(i) Energy is that which produces or quickens motions separating 

 and which resists or retards motions binding together two or more 

 particles of matter, or of the ethereal medium. 



By the oddest confusion between energy as thus defined — 

 which, of course, is no other than our old friend, repulsive 

 force — Mr. Clodd goes on to say of Sir. Grant Allen's 

 " energy " what is only true of energy as correctly 

 defined : — " A stone lying on a roof, a clock wound up but 

 not going, have," he says, " potential energy " [that is, 

 according to definition {b) they have potentially " that 



which produces or quickens motions separating, and whic'n 

 resists or retards motions binding together two or more par- 

 ticles of matter "], and this energy " becomes kinetic " (or 

 is actually displayed in motion) when the stone falls or the 

 clock goes. Yet I suppose it will be admitted of the stone 

 (the clock may go by the out-pressing of a spring, a case of 

 repulsion, or by the down-drawing of a weight, a case of 

 attraction) that the potentiality possessed by it while at rest 

 is a tendency to go towards the earth", a motion not 

 separating but drawing together particles of ponderable 

 matter. The distance it may have to travel when once 

 freed to yield to the attractive influence (technically called 

 the attractive force) measures the stone's power of "getting 

 into motion (technically called its " potential energy "). The 

 motion it thus acquires, when considered not simply as 

 motion, but in connection with the mass moved, is tech- 

 nically called kinetic ener<j>j. AVhen the stone is brought 

 to rest this kinetic energy remains in the movements of 

 the stone's particles and of the particles of air around it — 

 either in actual displacements, or in the vibratory motions 

 whose efl'ects are rendered sensible as heat. The former 

 neither falls under definition a nor under definition h, 

 because the particles moved draw towards some and from 

 other particles. Nor can the vibrating particles be said to 

 display attractive or repulsive (aggi-egating or separating) 

 tendencies, their motions being essentially alternating. Mr. 

 Clodd's — or rather, I suppose, Mr. Allen's — barrel of gun- 

 powder has, on the other hand, unquestionably separating 

 or expansive or repulsive potencies, which become kinetic 

 when the powder is fired. Yet even here definition h does not 

 apply to these tendencies in the rigid or definitive manner 

 imagined by Mr. Allen and conceded by Mr. Clodd. The 

 bottom of the barrel is pressed towards the ground bj- the 

 action of what is technically called the explosive force of the 

 powder ; a fragment of the barrel, after flying a certain dis- 

 tance, strikes some other body : in each case the action dis- 

 played — so for as the wood, the ground, and the struck body 

 are concerned — is of the kind producing motions drawing 

 particles of ponderable matter together, not separating them. 

 If this reasoning is objected to for the reason tluit the 

 particles of gunpowder alone are to be understood as having 

 potential energy according to definition h, the fault lies with 

 the definition, which either says too much or too little — too 

 much if we are to be thus limited, too little when the case 

 of the stone is considered (for where are the particles 

 potentially tending to separate in the stone's case ?) 



The fact is, Mr. Allen has obviously misunderstood alto- 

 gether the trouble in regard to the inexact expressions em- 

 ployed occasionally by Sir R. Grove and Professor Tyndall 

 (one may add Professor Huxley and Mr. Herbert Spencer), 

 a mistake arising rather from the assurance that they could 

 not be misunderstood, than from want of familiarity with 

 the accepted limitations of the words " force " and " energy " 

 as technically used from the time of Newton tintil now — 

 in treatises on dynamics. 



Sir W. R. Grove was taken to task, in somewhat pedantic 

 sort, for speaking of electricity, heat, light, and the like, as 

 physical " forces " in the title of his well-known work and 

 elsewhere, instead of always (as in many parts of that 

 treatise) speaking of them as " afl'ections of matter." He 

 in eflTect replied that the word " forces " as thus used could 

 not well be misunderstood. His chief object had been 

 to show that those " aflfections of matter " are " modes of 

 motion," and every one would know that " modes of motion " 

 cannot be described as " forces." Considering specifically 

 (p. 18) the objection that "the term force" should be used 

 " not as expressing the eflTect " (that is, motion or some 

 afiection of matter involving or depending on motion) " but 

 as that which produces the eflfect," he says, " this is true, 



