Notices respecting New Books. 297 



others of a character so neutral that the thought shall be uninflu- 

 enced by the term. Passing over many minor papers we arrive at the 

 important memoirs on Static Induction, on Conduction, and on Induc- 

 tion in Curved Lines. The latter idea reveals perhaps as clearly as any 

 other the profound and subtle character of Faraday's mind. The ques- 

 tion he proposes to himself is : " How is the electric power propa- 

 gated ? Does it act like the force of gravity at a distance without the 

 help of intervening matter, or does it act in virtue of such inter- 

 vention?'" He reflects thus : If it be a force acting at a distance, this 

 force will act in the straight line which unites each pair of active 

 points, but if it be a force which propagates itself by the agency of 

 material particles, there is every reason to suppose that it may act 

 in curved lines, as sound, for example, which depends on the atmo- 

 sphere for its propagation, can turn round a corner, or waves of 

 water round a rock. Reasoning in the inverse way, if it can be 

 established that the electric force propagatesitself in curved lines, it 

 may certainly be inferred from this that it requires a material 

 medium for its propagation. Faraday believes that his experiments 

 establish the latter jDoint ; others doubt it ; but however this may be, 

 the ])rofound and philosophic nature of the thought which guided 

 him is manifest. We may not be able to make Faraday's mode of 

 symbolizing the operations of nature our own, but when we reflect 

 upon the success which has attended his efforts, on the fact that 

 his peculiar symbols enabled him to foresee results of which no 

 other electrician dreamed, and which after a lapse of twenty years 

 accident has brought to light, we are warned against being dogmatic 

 on theoretic matters, and learn the salutary lesson, that the compe- 

 tent and earnest searcher after truth has other avenues than our 

 licensed scientific turnpikes into nature. 



The second volume of the Experimental Researches contains valu- 

 able papers on the Electricity of the Gymnotus, on the Source of 

 Power in the Voltaic Pile, on the Electricity evolved by the Friction 

 of Water and Steam, in which the principles of the hydro-electric 

 machine of Armstrong are fully developed, a paper on Magnetic 

 Rotations, dating as far back as 1821, some speculative observations, 

 and the writer's letters in the only controversy which has ever dis- 

 turbed his peaceful life. The memoir on the Source of Power in 

 the Voltaic Pile is of peculiar importance. The arguments which it 

 contains ajjpear to us to overthrow wholly the hypothesis of contact 

 as maintained by Volta. The doctrine of the conservation of force 

 has received formal expression at the hands of many recent investi- 

 gators, but the idea appears to have been a guiding light to Faraday 

 throughout his entire scientific career, and the explicit statement 

 of this principle at page 103 of the present volume jjlaces a difli- 

 culty in the way of the theory of contact which has never yet been 

 overcome. 



The third volume opens with an account of one of the most 

 remarkable discoveries of modern times, entitled by the author, " tlie 

 Magnetization of Light and the Illumination of Magnetic Lines of 

 Force," and expressed in the theoretic language usual in our day, 



Phil. Mag. S. 4. Vol. 10. No. 66. Oct. 1855. X. 



