40 PRESIDENTIAL ADDRESS SECTION A. 



Why is this the great achievement of human thought 'f 

 Because it has been found to be true — i.e., every theoretical resuh 

 o'btained by logical deduction from it has " come off," has been 

 confirmed by experiment : as the telescopes, the micrometers and 

 the spectroscopes have increased in accuracy, every observation 

 has been found to converge to the results prophesied by the 

 Newtonian reasoning. The planet Neptune (undreamt of 

 before) was found where theory, w^orking on otherwise un- 

 accounted-for motions of Uranus, said it should be. Halley's 

 comet returned duly after 75 years, as theory jjrophesied it 

 w^ould: corrections in the time of its return in lyio which al- 

 lowed, by Newton's laws, for the delaying influences of Jupiter 

 and other todies, were confirmed by facts. Great bridges, dams, 

 warships, railways, bicycles, motor-cars, electric cal)les, wireless 

 telegraphy, and all the rest, have in practice done exactly what 

 Newton's laws led us to expect. We can safely put our money 

 on these laws. But there are exceptions. The elli])tic orbit 

 of Mercury changes its position with reference to the sun much 

 more rapidly than theory leads us to expect ; light, in passing 

 through crystals, seems strangely indifferent to the earth's mo- 

 tion ; and the phenomena of radiation and radio-activity are 

 not in harmony with the scheme that our theory has established 

 for aether-matter relations. Some reliable physicists have come 

 to the conclusion that some or all of these exceptions are finally 

 irreconcilable with Newtonian philosophy ; others do not yet 

 despair of reconciling them to the system ; but the heterodox 

 view is gaining ground. 



In our reverence for our intellectual father Newton, we 

 may as well recognize that he had luck. Descartes' system, or the 

 Astrologers', or the Aristotelian, might ha\e been right : but they 

 were unfortunate in finding facts ultimately across their lines 

 of develo])ment instead of parallel to them. 



The history of mechanics since Newton and Leibnitz died 

 may be practically summed up as the automatic working of the 

 machinery of " the Calculus " on Newton's laws. Poisson, 

 D'Alembert, Euler, Lagrange, Laplace, Legendle, (iaviss. Young, 

 Fresnel, Faraday, Stokes, Helmholtz. Thomson, Maxwell, and 

 the rest of the host, have been as poets speaking the language 

 of the calculus, and laying bare, not the passing passions and 

 emotions of humanity, but the secrets of nature, the founda- 

 tions of the universe. 



One great name is absent from my list — that of Faraday. 

 He deserves mention by himself. His experimental and intel- 

 lectual work on electricity were marvellous, and give him rank as 

 one of the very greatest physicists; but he had no leanings 

 towards mathematics, and preferred thinking in " tubes and 

 lines of force," which he visualized as filling his space, to the 

 standard " potentials '' and energy functions. A striking tribute 

 to his ])owers has been recently paid by J. J. Thomson, who, able 

 mathematician as he is. has chosen in some of his work to recur 

 to Faradav's tube-of-force form of reasoning. 



