KINETIC Oil MECHANICAL VIEW UF NATURE. 81 



filled with a moving tiuid, and the velocity of the How — 

 inversely proportional to the sectional area of the tuljes 

 — represented the intensity of the force at any point in 

 space. He also showed how very much simpler the con- 

 ception becomes, if the law of tlie acting forces is the 

 experimentally established law of the inverse square of 

 the distance. 



This thought of " referring to the purely geometrical 

 idea of the motion of an imaginary tluid " ^ was tlie 

 beginning of the now universally adopted view of a 

 very large class of plienomena, and it was at the same 

 time a great step in the development of tlie kinetic 

 or mechanical view of natural processes. These lines or 

 tubes of force,"^ with which all space surrounding magnets 

 or electrified bodies was supposed to be filled, enal)led 

 Maxwell further to give a definite representation of that 



peculiar state of matter of which Faradav had very so. 

 ^ ^ J "Electro- 



early formed an indefinite conception, and wliich he oj'jj^'t^r'* 



called the " electrotonic state." Thomson had already 



in 1847 ^ shown how the ideas of Faraday, who as early 



^ How little ]\laxwell originally 

 intended to give a physical theory 

 is seen from the concluding sen- 

 tences of the introduction to his 

 first paper {!oc. cit., vol. i. p. 159) : 

 " By referring everything to the 

 purely geometrical idea of the 

 motion of an imaginary fluid, I 

 hope to attain generality and pre- 

 cision, and to avoid the dangers 

 arising from a premature theory 

 professing to explain the cause of 

 the phenomena. If the results of 

 mere speculation which I have 

 collected are found to be of any 

 use to experimental philosophers, 

 in arranging and interpreting their 

 results, they will have served their 



VOL. II. 



purpose, and a mature theory, in 

 which physical facts will be physi- 

 cally explained, will be formed by 

 those who by interrogating Nature 

 herself can obtain tlie only true 

 solution of the (luestions which the 

 mathematical theory suggests." 



-' Faraday had already in 1852 

 spoken of shells and tubes of force, 

 and invented the term sphondyloid 

 to denote the portion of space en- 

 closed between such shells of force 

 ('Exp. Kes.,' vol. iii.. No. 3271). 



2 In 1847 ('Cambr. and Dubl. 

 Math. Journal,' lepriiited in ' Matli. 

 and Phys. Pai>ers,' vol. i. p. 76) 

 Thomson wrote tlmt Faraday's 

 theory of electrostatic inductii>n 



