62 



SCIENTIFIC THOUGHT. 



a 42. It does not seem that Helmholtz's speculations were 



Influence of 



speculation's muc ^ taken up abroad ; in this country, however, they 



in England. f ruit f ul goi l . 1 they } ed firgt of ftU to 



1 It is a remarkable fact that the 

 country which produced the great 

 theory that finally destroyed the 

 older vortex theory of Descartes, 

 was the one in which, a century 

 after Newton, the modern views on 

 vortex-motion were first and almost 

 exclusively developed. Notably 

 the scientific atmosphere in which 

 Thomson and Tait moved was, inter 

 alia, charged with the bold ideas 

 and the suggestive nomenclature of 

 Macquorn Rankine. He owes his 

 permanent place in the history of 

 science to being side by side with 

 Lord Kelvin and Clausius, one of the 

 three founders of theoretical thermo- 

 dynamics. But he was in addition 

 to this perhaps the earliest and 

 purest representative of the kinetic 

 or mechanical view of natural 

 phenomena, and of the scientific 

 tendency or habit derived from his 

 profession as an engineer of con- 

 structing for every phenomenon to 

 be explained a mechanical model. 

 In a succession of memoirs beginning 

 in 1850, Rankine put forward his 

 theory of "molecular vortices," 

 " which assumes that each atom of 

 matter consists of a nucleus or 

 central point enveloped by an 

 elastic atmosphere" ('Scientific 

 Papers of Macquorn Rankine,' ed. 

 Miller, London, 1881, p. 17). Clerk 

 Maxwell in 1878 wrote of Rankiue's 

 theory: "Whatever he imagined 

 about molecular vortices was so 

 clearly imaged in his mind's eye 

 that he, as a practical engineer, 

 could see how it would work. How- 

 ever intricate, therefore, the 

 machinery might be which he 

 imagined to exist in the minute 

 parts of bodies, there was no danger 

 of his going on to explain natural 

 phenomena by any mode of action 



of this machinery which was not 

 consistent with the general laws of 

 mechanism. Hence, though the 

 construction and distribution of his 

 vortices may seem to us as compli- 

 cated and arbitrary as the Cartesian 

 system, his final deductions are 

 simple, necessary, and consistent 

 with facts. Certain phenomena were 

 to be explained. Rankine set himself 

 to imagine the mechanism by which 

 they might be produced. Being an 

 accomplished engineer, he succeeded 

 in specifying a particulur arrange- 

 ment of mechanism competent to 

 do the work." Maxwell goes on to 

 say : "As long as the training of 

 the naturalist enables him to trace 

 the action only of particular 

 material systems, without giving 

 him the power of dealing with the 

 general properties of all such 

 systems, he must proceed by the 

 method so often described in 

 histories of science he must 

 imagine model after model of hypo- 

 thetical apparatus, till he finds one 

 which will do the required work. 

 The theory of molecular 

 vortices was distinguished from 

 other theories which attribute 

 motion to bodies apparently at rest, 

 by the further assumption that this 

 motion is like that of very small 

 vortices, each whirling about its 

 own axis " (Clerk Maxwell in 

 ' Nature,' 1878 ; ' Scientific Papers,' 

 vol. ii. p. 662, c. ; and Prof. 

 Tait's memoir of Rankine in the 

 ' Collected Papers,' p. xxix). In the 

 most recent attempt to reconcile 

 the two fundamental ideas with- 

 out which we do not seem to be 

 able to proceed in a description of 

 natural phenomena viz. , that 

 space is a plenum, filled by a con- 

 tinuous something, and that matter 



