SOME VIEWS ON LORD KELVIN'S WORK 421 



Journal points out the analogy between the steady motion of 

 heat and the chief theorems on Attraction, thus uniting flow of 

 heat with flow of force in electrostatics and paving the way 

 towards the banishment of action at a distance ideas in the latter 

 subject. The support which such an analogy lent to the views 

 then being put forward by Faraday is clearly indicated at the 

 end of Thomson's paper " On the Elementary Laws of Statical 

 Electricity," of date 1845 ; and there is little doubt that this dis- 

 covery deepened his interest in Faraday's researches and gave his 

 thoughts an added stimulus in the direction of physical theories. 

 From the importance of his mathematical work his interests 

 grew and extended to the region of practical physics under the 

 influence first of Faraday and afterwards of Joule. Being also 

 closely in touch with the work of Stokes " On the Friction of 

 Fluids in Motion, and the Equilibrium and Motion of Elastic 

 Solids," which virtually brought two new regions within the 

 scope of his mathematical analogies, he was naturally inspired 

 by Faraday's discovery, in 1845, of rotation of the plane of 

 polarised light in transparent bodies by a magnetic field, to 

 attempt and to achieve the elastic solid illustration of Electro- 

 magnetic actions. His paper " On a Mechanical Representation 

 of Electric, Magnetic, and Galvanic Forces," which appeared in 

 1847, marks the consolidation of his views with respect to the 

 medium of electromagnetic action. Lord Kelvin in later life never 

 hesitated to employ action at a distance principles in his later 

 speculations as to the constitution of atoms and their interactions, 

 whenever insufficiency of knowledge made such tentative methods 

 expedient, but Faraday's discovery of 1845 seems to have con- 

 vinced him of the necessity for some elastic solid explanation of 

 the actions manifested in the ether as Electrostatic, Magnetic, or 

 Electromagnetic forces. This same paper, which marks his 

 decision in this matter, practically adhered to throughout his 

 life, assisted largely in the development of Maxwell's views 

 towards the electromagnetic theory of light which he reached 

 in 1864. 



In this connection, as in other important decisions regarding 

 the larger questions in Physics, it is evident that the mathe- 

 matical bent of Lord Kelvin's mind largely determined his 

 attitude towards physical theories. A quotation which he makes 

 from Green's writings, regarding general matter-of-fact explana- 

 tions of physical processes, reveals clearly his own attitude of 



