SCIENCE AND MAN 



79 



to two great Path-hewers^ as the Germans 

 call them, whose names in relation to 

 this subject are linked in indissoluble 

 association. These names are Julius 

 Robert Mayer and James Prescott Joule. 



In his essay on "Circles" Mr. Emerson, 

 if I remember rightly, pictured intel- 

 lectual progress as rhythmic. At a 

 given moment knowledge is surrounded 

 by a barrier which marks its limit. It 

 gradually gathers clearness and strength 

 until by-and-by some thinker of excep- 

 tional power bursts the barrier and wins 

 a wider circle, within which thought 

 once more entrenches itself. But the 

 internal force again accumulates, the 

 new barrier is in its turn broken, and the 

 mind finds itself surrounded by a still 

 wider horizon. Thus, according to 

 Emerson, knowledge spreads by inter- 

 mittent victories instead of progressing 

 at a uniform rate. 



When Dr. Joule first proved that a 

 weight of one pound, falling through a 

 height of 772 feet, generated an amount of 

 heat competent to warm a pound of water 

 one degree Fahrenheit, and that in lifting 

 the weight so much heat exactly dis- 

 appeared, he broke an Emersonian 

 " circle," releasing by the act an amount 

 of scientific energy which rapidly overran 

 a vast domain, and embodied itself in 

 the great doctrine known as the " Con- 

 servation of Energy." This doctrine 

 recognises in the material universe a 

 constant sum of power made up of items 

 among which the most Protean fluctua- 

 tions are incessantly going on. It is as 

 if the body of Nature were alive, the 

 thrill and interchange of its energies 

 resembling those of an organism. The 

 parts of the "stupendous whole" shift and 

 change, augment and diminish, appear 

 and disappear, while the total of which 

 they are the parts remains quantitatively 

 immutable. Immutable, because when 

 change occurs it is always polar plus 

 accompanies minus, gain accompanies 

 loss, no item varying in the slightest 

 degree without an absolutely equal change 

 of some other item in the opposite direc- 

 tion. 



The sun warms the tropical ocean, 

 converting a portion of its liquid into 

 vapour, which rises in the air and is 

 recondensed on mountain heights, return- 

 ing in rivers to the ocean from which it 

 came. Up to the point where condensa- 

 tion begins, an amount of heat exactly 

 equivalent to the molecular work of 

 vaporisation and the mechanical work 

 of lifting the vapour to the mountain- 

 tops has disappeared from the universe. 

 What is the gain corresponding to this 

 loss ? It will seem when mentioned to 

 be expressed in a foreign currency. The 

 loss is a loss of heat ; the gain is a gain 

 of distance, both as regards masses and 

 molecules. Water which was formerly 

 at the sea-level has been lifted to a 

 position from which it can fall; mole- 

 cules which have been locked together 

 as a liquid are now separate as vapour 

 which can recondense. After condensa- 

 tion gravity comes into effectual play, 

 pulling the showers down upon the hills, 

 and the rivers thus created through their 

 gorges to the sea. Every raindrop which 

 smites the mountain produces its definite 

 amount of heat ; every river in its course 

 developes heat by the clash of its cataracts 

 and the friction of its bed. In the act 

 of condensation, moreover, the molecular 

 work of vaporisation is accurately re- 

 versed. Compare, then, the primitive 

 loss of solar warmth with the heat gene- 

 rated by the condensation of the vapour, 

 and by the subsequent fall of the water 

 from cloud to sea. They are mathemati- 

 cally equal to each other. No particle 

 of vapour was formed and lifted without 

 being paid for in the currency of solar 

 heat ; no particle returns as water to the 

 sea without the exact quantitative resti- 

 tution of that heat There is nothing 

 gratuitous in physical nature, no expen- 

 diture without equivalent gain, no gain 

 without equivalent expenditure. With 

 inexorable constancy the one accom- 

 panies the other, leaving no nook or 

 crevice between them for spontaneity to 

 mingle with the pure and necessary play 

 of natural force. Has this uniformity 



