THE ASTRONOMICAL VIEW OF NATURE. 371 



nished a foundation, there remained in physics mainly the 

 investigation of the laws of interaction of bodies; for 

 without interaction bodies would for ever remain in that 

 state of rest or motion in which they happened to be. 



these actions of ponderable matter, 

 in which electricity was flowing, 

 could be reduced to an action at a 

 distance proportional to the inverse 

 square of the elements of the electric 

 circuits. When Faraday showed 

 that a current of electricity under 

 certain conditions induced in con- 

 ductors in its neighbourhood other 

 currents, this was explained by 

 saying that the electric fluid exerted 

 not only pondero-motoric but also 

 electro-motoric action at a distance. 

 Not only did electrified matter act 

 on other electrified matter, but 

 electricity as a fluid acted on elec- 

 tricity itself. Weber adopted, for 

 the purpose of putting these ap- 

 parent actions into mathematical 

 language, and for finding an ele- 

 mentary law of the ultimate par- 

 ticles of electric matter out of 

 which by summation the observ- 

 able data might be calculated, the 

 hypothesis of Fechner, according to 

 which in an electric current the 

 two electric fluids were moving 

 with equal velocity in opposite 

 directions. It then became evident 

 looking at the phenomena dis- 

 covered by Oersted, Ampere, and 

 Faraday that the electro - static 

 formula of Coulomb required to 

 be supplemented by an additional 

 term, if the mutual action was to 

 be determined not only for the case 

 of equilibrium and rest, but also for 

 that of relative motion. The ad- 

 ditional term, depending on this 

 relative motion, had to be found. 

 (See ' Electrodynamische Maasbes- 

 timmungen, ' vol. i. p. 102). From 

 this starting-point, and with this 

 definite problem in view, Weber un- 

 dertook a series of most valuable 

 measurements. No doubt can exist 



as to the lasting importance of these 

 measurements. Any theoretical con- 

 ception which produces in its appli- 

 cation such results must hold a 

 prominent place in the history of 

 scientific thought. And the very 

 fact that, unlike Boscovich and 

 other purely metaphysical theorists, 

 Weber undertook to fix by experi- 

 ment the actual constants or nu- 

 merical quantities which his ab- 

 stract formula contained, led to 

 much enlargement of actual know- 

 ledge. I will mention only one 

 of the most interesting points in 

 his elaborate researches. I stated 

 above that it took a whole century 

 after the discovery of the law of 

 gravitation before the gravitation 

 constant was approximately fixed, 

 but that for the progress of phy- 

 sical astronomy this was of little 

 importance, gravity being a uni- 

 versal property of matter. Still 

 such' a constant exists, because we 

 possess another definition of matter 

 viz., inertia or mass. The con- 

 stant in Coulomb's law cannot be 

 determined in a similar manner, as 

 the property of attraction or repul- 

 sion defines for us ultimately the 

 numerical quantity of electricity. 

 We have so far no other ultimate 

 absolute measure of electricity. But 

 in Weber's law it was the quantities 

 of electrical matter which acted on 

 each other not only according to 

 their distances, but also according 

 to their relative motion or their 

 velocities. A second constant thus 

 entered into his formula, and this 

 constant established a relation be- 

 tween electricity at rest and elec- 

 tricity in motion. This constant 

 was a velocity, and, if determinable, 

 it revealed a constant of nature in 



