262 



SCIENCE. 



[N. S. Vol. XX. No. 504. 



transformations applied science is at pres- 

 ent so largely concei-ned, can not rival the 

 kinetic energy stored within the molecules 

 themselves. This prodigious mechanism 

 seems outside the range of our immediate 

 interests. We live, so to speak, merely on 

 its fringe. It has for us no promise of 

 utilitarian value. It vrill not drive our 

 mills; -we can not harness it to our trains. 

 Yet not less on that account does it stir 

 the intellectual imagination. The starry 

 heavens have from time immemorial moved 

 the worship or the wonder of mankind. 

 But if the dust beneath our feet be indeed 

 compounded of innumerable systems, whose 

 elements are ever in the most rapid motion, 

 yet retain through uncounted ages their 

 equilibrium unshaken, we can hardly deny 

 that the marvels we directly see are not 

 more worthy of admiration than those 

 which recent discoveries have enabled us 

 dimly to surmise. 



Now, whether the main outlines of the 

 world-picture which I have just imperfect- 

 ly presented to you be destined to survive, 

 or whether in their turn they are to be ob- 

 literated by some new drawing on the 

 scientific palimpsest, all will, I think, admit 

 that so bold an attempt to unify physical 

 nature excites feelings of the most acute 

 intellectual gratification. The satisfaction 

 it gives is almost esthetic in its intensity 

 and quality. We feel the same sort of 

 pleasurable shock as when from the crest 

 of some melancholy pass we first see far 

 below us the sudden glories of plain, river 

 and mountain. Whether this vehement 

 sentiment in favor of a simple universe has 

 any theoretical justification I will not ven- 

 ture to pronounce. There is no a priori 

 reason that I know of for expecting that 

 the material world should be a modification 

 of a single medium, rather than a com- 

 posite structure built out of sixty or sev- 

 enty elementary substances, eternal and 

 eternally different. Why, then, should we 



feel content with the first hypothesis and 

 not with the second? Yet so it is. Men 

 of science have always been restive under 

 the multiplication of entities. They have 

 eagerly noted any sign that the chemical 

 atom was composite, and that the different 

 chemical elements had a common origin. 

 Nor, for my part, do I think such instincts 

 should be ignored. John Mill, if I rightly 

 remember, was contemptuous of those who 

 saw any difficulty in accepting the doctrine 

 of 'action at a distance.' So far as ob- 

 servation and experiment can tell us, bodies 

 do actually influence each other at a dis- 

 tance. And why should they not? Why 

 seek to go behind experience in obedience 

 to some a priori sentiment for which no 

 argument can be adduced? So reasoned 

 Mill, and to his reasoning I have no reply. 

 Nevertheless, we can not forget that it was 

 to Faraday's obstinate disbelief in 'action 

 at a distance' that we owe some of the 

 crucial discoveries on which both our elec- 

 tric industries and the electric theory of 

 matter, are ultimately founded; while at 

 this very moment physicists, however baf- 

 fled in the quest for an explanation of 

 gravity, refuse altogether to content them- 

 selves with the belief, so satisfying to Mill, 

 that it is a simple and inexplicable prop- 

 erty of masses acting on each other across 

 space. 



These obscure intimations about the na- 

 ture of reality deserve, I think, more atten- 

 tion than has yet been given to them. That 

 they exist is certain ; that they modify the 

 indifferent impartialitiy of pure empiricism 

 can hardly be denied. The common notion 

 that he who would search out the secrets of 

 nature must humbly wait on experience, 

 obedient to its slightest hint, is but partly 

 true. This may be his ordinary attitude; 

 but now and again it happens that observa- 

 tion and experiment are not treated as 

 guides to be meekly followed, but as wit- 

 nesses to be broken down in eross-examina- 



