NOTEMBEE 20, 1914] 



SCIENCE 



723 



condemned. Thomson and Tate, T and T', 

 as we used to call them, in the earlier edition 

 of their book anathematized them, as all the 

 more pernicious in proportion as they were 

 beautiful. They were completely swept away 

 by the profound originality and incisiveness 

 of the Faraday-Maxwell hypothesis (1854). 

 Maxwell's great book (18Y3) had in fact ap- 

 peared three years before I entered as a stu- 

 dent, but it naturally was looked at askance 

 in Germany, Helmholtz alone excepted. The 

 aim of the earlier thinkers, to reduce the whole 

 of electrical science to one equation was now 

 to be realized in a way that marks one of the 

 most important epochs in the history of physi- 

 cal science; an epoch comparable only to that 

 of Newton; for although Maxwell modestly 

 ascribes the incentive to his great accom.- 

 plishments to Faraday, and believes that he 

 is seeing nature with a mathematically un- 

 sophisticated eye, the capital discovery of the 

 equations of the electromagnetic field (and 

 this is the real issue) is Maxwell's creation. 

 More than the widest sweep of the generalizing 

 fancy could have anticipated was here com- 

 pleted; for at a single stroke of the wand, as 

 it were, the whole domain of light and heat 

 was annexed to electricity. It interpreted the 

 meaning of the transparent and the opaque 

 body of reflection and refraction. It intro- 

 duced a new cosmical force, the light pressure 

 long after found by Lebedew (1900), and our 

 own countrjTnen, Nichols and Hull. It har- 

 monized the divergent views of Fresnel and 

 Neumann, admitting both impartially, and it 

 gave to optics a new lease of life by lifting it 

 over the obstructions of the elastic theory. 

 Indeed Maxwell's best friends were apprehen- 

 sive, since the theory predicted even more 

 than was believed to exist, until in 187Y the 

 new Maxwellian light dawned upon the mind 

 of Hertz. The theory endowed the world 

 medium, the ether, with new potencies, in in- 

 sisting on its continuity, on the point to point 

 transfer of electric force, so that ether stress 

 became one of its familiar images, a veritable 

 charm to conjure by. 



It would carry us too far if we attempted to 

 analyze the reaction of the new views on kin- 



dred sciences. Hydrodynamics, which had 

 suggested the useful conception of the force- 

 flux, in particular, profited and such beauti- 

 ful researches as those of the Bjerknes 

 (1863 et seq.) father and son, were stimulated 

 in proportion as they fitted into the electromag- 

 netic scheme. It was inevitable, moreover, 

 that in the further treatment of Maxwell's 

 equation the use of vector methods of compu- 

 tation should become indispensable in physics. 

 They were approached cautiously enough and 

 at first rather regarded as an affectation. Max- 

 well himself merely indicated the use of qua- 

 ternian methods. Helmholtz, so far as I 

 know, made no use of them. But in spite of 

 petty differences of notation which still per- 

 sist, the vector method became more and more 

 general until to-day it is a commonplace, and 

 beginning to make room for the new and more 

 powerful 4, 6 and 9 dimensional geometry of 

 higher vectors. 



This was the second epoch and an epoch 

 of unexampled fruitfulness. The ether elec- 

 trically ignored heretofore has become all em- 

 bracing. Woe to him that lisps, action at a 

 distance! That Maxwell should have died 

 before the ultimate vindication of his theory 

 on the part of Hertz or the appearance of im- 

 portant corollary of Pojmting (1884) is one 

 of the tragedies of science. Similarly Hertz 

 was not to witness the spectacular development 

 of radio-telegraphy which followed so soon 

 after his death. Maxwell's theory, which ac- 

 cording to Hertz means Maxwell's equations, 

 thus includes the whole of physics, dynamics 

 alone excepted, and the world equation has ad- 

 vanced another step. Maxwell indeed, follow- 

 ing the established custom, endeavored to call 

 dynamics to his aid; but here his questions 

 were put to a silent sphinx, inasmuch as 

 mechanics had no counsel to give. Naturally 

 the theory so revolutionary gained headway 

 but slowly on the continent of Europe and 

 even in England, unfortunately, Kelvin and 

 (I believe) Eayleigh long remained uncon- 

 vinced. When therefore the theory was uni- 

 versally accepted, it was already ripe for the 

 modification, which Hertz himself actually 



