64 



SCIENTIFIC THOUGHT. 



43. 



Difflculties 



of Lord Kelvin this theory led to the conception that 

 in an all-pervading, boundless fluid, such as physicists 

 imagined for the purposes of the theory of light, dif- 

 ferentiated portions might exist in the form of whirling 

 rings (vortex rings), which would possess most of the 

 properties of ponderable matter identity and perman- 

 ence of quantity of substance, stability, rigidity, elasticity. 

 It was indeed soon found that although eminently sug- 

 gestive in this way, and pointing in the direction of a 



ring theory. c ' 



general kinetic theory of natural phenomena, the vortex 

 ring theory presented two fundamental difficulties. How 

 does whirling matter acquire weight, and how does it 

 acquire immensely increased inertia ? In the explana- 

 tion of these two properties the progress has been small, 

 if indeed any glimpse at all has as yet been got. 1 

 But by suggesting numberless experiments through which 

 our knowledge of things natural has been enormously in- 

 creased, by placing before the minds of mathematicians 

 a great number of problems of practical importance and 

 physical interest, and generally by familiarising the minds 

 of philosophers with an ultimate kinetic explanation of 

 nature, 2 the vortex-atom theory has marked an epoch in 



after him, to distinguish between 

 singly, doubly, triply, &c., con- 

 nected surfaces (' Werke, ' 1876, 

 pp. 18, 88, 448). These studies, 

 which for a long time were looked 

 upon merely as curiosa or of purely 

 abstract interest, were indepen- 

 dently taken up in the practical 

 interest of the vortex-atom theory 

 by Prof. Tait in 1876 (" On Knots," 

 Trans. Roy. Soc. Edinb., 1877, vol. 

 28, p. 145, &c. ), and continued in 

 1884-85. To him we owe a con- 

 venient notation and vocabulary. 

 For the history of the subject and 



further developments, see Din- 

 geldey, ' Topologische Studien,' 

 Leipzig, 1890. 



1 See Clerk Maxwell's article 

 " Atom " in the 9th ed. of the 

 ' Ency. Brit.,' reprinted in 'Scien- 

 tific Papers,' vol. ii., and the account 

 given there of Le Sage's theory. 



2 See Dr Larmor's Address to 

 Section A of the Brit. Assoc. at 

 Bradford in 1890 (Report, p. 625) : 

 " The vortex-atom theory has been 

 a main source of physical suggestion, 

 because it presents, on a simple 

 basis, a dynamical picture of an 



