3H THE POPULAR SCIENCE MONTHLY. 



matical abstraction. The two theories of light have exhausted all 

 imaginable ways in which force can be gradually transmitted without 

 increase or loss of energy. Maxwell cut the Gordian knot when he 

 selected the luminiferous ether itself as the arena on which to marshal 

 the electro-magnetic forces under the symbols of his mathematics, and 

 made light a variety of electro-magnetic action. His analysis gave a 

 velocity essentially the same as that of Weber, with the advantage of 

 being a physical reality and not a mere ratio. Of the two volumes 

 of Mi*. Maxwell, freighted with the richest and heaviest cargo, the re- 

 viewer says : " Their author has, as it were, flown at every thing : and, 

 with immense spread of wing and power of beak, he has hunted down 

 his victims in all quarters, and from each has extracted something new 

 and interesting for the intellectual nourishment of his readers." Clear 

 physical views must precede the application of mathematics to any 

 subject. Maxwell and Thomson are liberal in their acknowledgments 

 to Faraday. Mr. Thomson says : " Faraday, without mathematics, 

 divined the result of the mathematical investigation ; and, what has 

 proved of infinite value to the mathematicians themselves, he has 

 given them an articulate language in which to exjjress their results. 

 Indeed, the whole language of the magnetic field and lines of force is 

 Faraday's. It must be said for the mathematicians that they greedily 

 accepted it, and have ever since been most zealous in using it to the 

 best advantage." 



It is not expected that the new views of physics will be generally 

 accepted without vigorous opposition. A large amount of intellectual 

 capital has been honestly invested in the fortunes of the other side. 

 The change is recommended by powerful physical arguments, and it 

 disenthralls the theories of science from many metaphysical difficulties 

 which weigh heavily on some minds. On the other hand, the style of 

 mathematics which the innovation introduces is novel and complex ; 

 and good mathematicians may find it necessary to go to school again 

 before they can read and understand the strange analysis. It is feared 

 that, with many who are not easily deflected from the old ruts, the in- 

 tricacies of the new mathematics will outweigh the superiority of the 

 new physics. 



The old question, in regard to the nature of gravitation, was never 

 settled : it was simply dropped. Now it is revived w T ith as much 

 earnestness as ever, and with more intelligence. Astronomy cast in 

 its own mould the original theories of electrical and magnetic action. 

 The revolution in electricity and magnetism must necessarily react 

 upon astronomy. It was proved by Laplace, from data which would 

 now, probably, require a numerical correction, that the velocity of the 

 force of gravitation could not be less than eight million times the 

 velocity of light ; in fact, that it was infinite. Those who believe in 

 action at a distance cannot properly speak of the transmission of 

 gravitation. Force can be transmitted only by matter : either with 



