[From the Transactions of the Cambridge Philosophical Society, Vol. X. Part I.] 



VIII. On Faraday's Lines of Force. 

 [Read Dec. 10, 1855, and Feb. 11, 1856.] 



THE present state of electrical science seems peculiarly unfavourable to specu- 

 lation. The laws of the distribution of electricity on the surface of conductors 

 have been analytically deduced from experiment ; some parts of the mathematical 

 theory of magnetism are established, while in other parts the experimental data 

 are wanting ; the theory of the conduction of galvanism and that of the mutual 

 attraction of conductors have been reduced to mathematical formulae, but have 

 not fallen into relation with the other parts of the science. No electrical theory 

 can now be put forth, unless it shews the connexion not only between electricity 

 at rest and current electricity, but between the attractions and inductive effects 

 of electricity in both states. Such a theory must accurately satisfy those laws, 

 the mathematical form of which is known, and must afford the means of calcu- 

 lating the effects in the limiting cases where the known formulae are inapplicable. 

 In order therefore to appreciate the requirements of the science, the student 

 must make himself familiar with a considerable body of most intricate mathe- 

 matics, the mere retention of which in the memory materially interferes with 

 further progress. The first process therefore in the effectual study of the science, 

 must be one of simplification and reduction of the results of previous investiga- 

 tion to a form in which the mind can grasp them. The results of this simplifi- 

 cation may take the form of a purely mathematical formula or of a physical 

 hypothesis. In the first case we entirely lose sight of the phenomena to be 

 explained ; and though we may trace out the consequences of given laws, we 

 can never obtain more extended views of the connexions of the subject. If, 

 on the other hand, we adopt a physical hypothesis, we see the phenomena only 

 through a medium, and are liable to that blindness to facts and rashness in 



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