80 



SCIENTIFIC THOUGHT. 



49. 



His con- 

 ception of 

 "tubes of 

 force. " 



embrace the processes of the flow of heat, of electricity, 

 magnetic and diamagnetic, and of fluid motion. " He 

 called attention to the remarkable resemblance which 

 the diagrams of flow bore to those which Mr Faraday 

 had recently shown at the Eoyal Institution to illus- 

 trate his views regarding the action of ferro- magnetics 

 and diamagnetics in influencing the field of force in 

 which they are placed, and justified and illustrated the 

 expression ' conducting power for the lines of force ' by 

 referring to rigorous mathematical analogies presented 

 by the theory of heat." l 



This view, which Thomson had merely shadowed forth, 

 was more fully worked out by Maxwell in 1855 and 

 1861. His methods 2 were "generally those suggested by 

 the processes of reasoning which are found in the re- 

 searches of Faraday, and which, though they had been 

 interpreted mathematically by Prof. Thomson and others, 

 are very generally supposed to be of an indefinite and 

 unmathematical character when compared with those 

 employed by the professed mathematicians." The first 

 addition which he introduced, by which he made Fara- 

 day's " lines of force " mathematically more definite, was 

 to change them into " tubes of force," which represented 

 not only the direction of force at every point of space, 

 but also according to their sectional dimensions the 

 intensity of the force. These tubes were supposed to be 



1 Abstracts of two communica- 

 tions to the British Association at 

 Belfast in 1852, "On certain Mag- 

 netic Curves : with Applications to 

 Problems in the Theories of Heat, 

 Electricity, and Fluid Motion " 

 (Reprint of Papers, &c., p. 519, &c.) 



2 James Clerk Maxwell ' ' On 

 Faraday's Lines of Force," 'Trans- 

 actions of the Cambridge Philo- 

 sophical Society,' 1855. See ' Col- 

 lected Scientific Papers,' vol. i. p. 

 157. 



