KINETIC OR MECHANICAL VIEW OF NATURE. 71 



have been the means of keeping before the minds of 

 natural philosophers the question how these actions 

 are mechanically communicated, a problem which lay- 

 outside of the astronomical view of the 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 he succeeded in 

 showing by experiment that magnets in the neighbour- 

 hood of transparent substances which have a polarising 

 effect on rays of light possessed the property of altering 

 the direction in which the polarised 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 1850. 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 

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



conception 



be brought into harmony was William Thomson (Lord ^^ d 

 Kelvin). As early as 1842, 1 when scarcely eighteen 



46. 



Develop- 



1 "On the uniform motion of 

 Heat in homogeneous solid bodies, 

 and its connexion with the mathe- 

 matical theory of Electricity," 

 ' Cambridge Mathematical Jour- 

 nal,' February 1842. The following 

 note is attached to the reprint in 

 the ' Philosophical Magazine ' of 

 1854: "The general conclusions 

 established show that the laws of 

 distribution of electric or magnetic 

 force in any case whatever must be 

 identical with the laws of distri- 

 bution of the lines of motion of 



heat in certain perfectly defined 

 circumstances. With developments 

 and applications contained in a 

 subsequent paper (1845), they con- 

 stitute a full theory of the char- 

 acteristics of lines of force, which 

 have been so admirably investigated 

 experimentally by Faraday, and 

 complete the analogy with the 

 theory of the conduction of heat, 

 of which such terms as 'conduct- 

 ing power of lines of force ' (' Exp. 

 Res.,'Nos. 2797-2802) involve the 

 idea. " 



