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 46. 



Develop- 



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



conception 



be brought into harmony was William Thomson (Lord j^? 1 

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



1 "On the uniform motion of heat in certain perfectly denned 



Heat in homogeneous solid bodies, ; circumetances. With developments 



and its connexion with the mathe- : and applications contained in a 



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



' Cambridge Mathematical Jour- stitute & full theory of the char- 



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 i theory of the conduction of heat, 



distribution of electric or magnetic j 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. 

 Res.,'No3. 2797-2802) involve the 

 idea." 



