KINETIC OR MECHANICAL VIEW OF NATURE. 71 



liave been the means of keeping l>efore the minds of 

 natural philosophers the question h«iw these actions 

 are mechanically communicated, a problem which lay 

 outside of the astronomical view of tlie phenomena. 

 To Faraday himself the analogy between the phenomena 

 of these actions meant also a real physical relation 

 or even identity, a supposition which he followed up 

 with unwearying patience and all the experimental 

 resources of his inventive mind, till lie succeeded in 

 showing by experiment that magnets in the neighbour- 

 ho(jd of transparent substances which ]ia\e a polarising 

 effect on rays of light possessed the jiroperty of altering 

 the direction in which the jjolarised rays show their 

 laterality. Faraday's conception of " lines of force " 

 filling all space and explaining electric and magnetic 

 action, radiation, and possibly also gravitation, was 

 elaborated during the years 1830 to ISoO. An opinion 

 then prevailed that his discoveries stood in opposition to 

 the views elaborated and experimentally verified by 

 Continental philosophers. The first who showed the 46. 



Devplop- 



analogy and threw out a hint how the two views could imntofthe 



^^ conception 



be brought into harmony was William Thomson (Lord ^J^"^ 

 Kelvin). As early as 1842,^ when scarcely eighteen 



^ " On the uniform motion of [ heat in certain perfectly defined 



Heat in homogeneous solid bodies, circumstances. With developments 



and its connexion with the niathe- and apijlications contained in a 



matical theory of Electricity," subsequent paper (1845), they con- 



' Cambridge Mathematical Jour- '. stitute a full tlieory of the cliar- 



nal,' February 1842. The following acteristics of lines of force, which 



note is attached to the reprint in have been so admirably investigated 



the ' Philosophical Magazine ' of experimentally by Faraday, and 



1854 : " The general conclusions complete the analogy with the 



established show that the laws of theory of the conduction of iieat, 



distribution of electric or magnetic of which such terms as 'conduct- 



force in any case whatever must be 

 identical with the laws of distri- 

 bution of the lines of motion of 



ing power of lines of force ' (' Exp. 

 Re8.,'Noa. 2797-2802) involve the 

 idea. " 



