:natueal philosophy. 



THE NEW THEORY OF LIGHT. 



TiTE following are extracts from a letter to the " Reatler " by J. 

 G. Macvic-ar, on Professor C. Maxwell's elcctro-niagnetie theory 

 of light, of which he says : '♦ A slight inspection is suflicient to 

 show that it sets tlie seal of mathemctical consistency and prestige 

 upon ideas which must modify profoundly all our popular ideas 

 on solar radiation. With regard to light, it sanctions the idea 

 that it is an electro-magnetic phc^nomonon, and such, therefore, 

 that it must observe tlie laws and produce the 2>henomena of what 

 is commoidy known as polarized action. And does not tiiis view 

 at once relieve speculative astronomy of some of its gi'catest 

 difliculties, and open the way for a happy exidanation of some 

 of the most remarkable but still unexplained phenomena of the 

 heavens ? 



"Thus, our first physicists, taking for gi\anted, as to the solar 

 action, the hypotliesis of an universal and indiscriminate radiation 

 in all directions into sj)ace (or in accordance with modern science, 

 let us say into the ether) by such a body as the sun, just as if he 

 were a sj^hcrical gong poised in compressed air, and struck from 

 within sinniltancously all round, have been bestowing of late 

 years infinite pains to ex2)lain how his brightness is kept up 

 during all time, without any loss, so far as can be discovered. 

 But, if not gross mechanical undulations to and fro in compi-essed 

 air, but a rhythmical action in ctlicr — electro-magnetism, in short 

 — is to be the type to Avhich light and radiant heat are to be re- 

 ferred, then there will be no waste of solar action at all, and there 

 need be no more concern about the permanence of the sun's bright- 

 ness. For if the solar action, with respect to which, so far as ob- 

 servation goes, we know only that it illuminates the vai'ious mem- 

 bers of our planetary sj^stem, be of an electric or electro-magnetic 

 nature, then, after having induced a similar state of action in 

 the medium immediately surrounding him, — that is, after having 

 surrounded the central orb Avith a photosphere, — it will render 

 the ether immediately beyond almost, and soon altogether, non- 

 conducting in all directions, excei^t those in which bodies in a 

 dissimilar state pi-esent themselves, — that is, the sun will be in- 

 sulated in the ether, except in the direction of planets, satellites, 

 meteorites, etc. In all other directions, his action will be con- 

 sei-ved. And even in the direction, in which he radiates to a 

 distance, he will receive back again as much as he gives away. 

 Such is the well-known phenomenon of electrical and magnetic 

 action. In exchansre for the lisrht and heat which the sun gives 

 to the planets, he will receive from them a negative, reciprocal 



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