124 DIRECT PROPERTIES OF MOLECULES 349 



atomic weights, and which point to a common origin of all 

 the elements from one and the same substance, as was con- 

 jectured by Prout, and after him by Thos. Thomson and 

 Dumas. 



The theory of vortex atoms proposed by Lord Kelvin l 

 seems to me to be a happy hypothesis which is well suited to 

 satisfactorily explain the facts ; it is directly connected with 

 a similar and rather earlier theory of Rankine's, 2 and with 

 a doctrine taught by Descartes a very long time before. 

 It rests on a mathematical memoir by Helmholtz, 3 in 

 which the vortical motions of a liquid moving without 

 friction are investigated, and especially upon one theorem 

 proved in this memoir respecting vortex lines and vortex 

 filaments. The former name is given by Helmholtz to 

 curved lines which may be so drawn in the liquid that at 

 every point along their whole length they are perpendicular 

 to the direction of the motion of rotation, and are therefore 

 parallel to the axis of rotation ; a vortex filament is a thin 

 filament of liquid the axis of which is a vortex line and 

 which is bounded on the outside by a system of vortex lines. 

 Helmholtz proved that, if certain assumptions, satisfied 

 in nature, are made as to the law of action of external forces 

 on the liquid, all the motions so proceed that each vortex 

 line remains permanently made up of the same particles of 

 liquid. Since the vortex lines are in general closed curves, 

 each vortex filament contains a finite and never-changing 

 mass of liquid, which can alter its ring shape and its 

 position, but can never lose the connection of its parts. 



Lord Kelvin takes as the^foundation of his new theory 

 of atoms the theorem, which this law proves, that the pro- 

 duction of new vortices and new vortex filaments would be an 

 act of creation. He considers the so-called atoms to be vortex 

 filaments, and represents them by the smoke-rings which 

 tobacco smokers blow. 



However strange this view may appear at first sight, it 

 will be found by everyone who takes the trouble to master 



1 Phil. Mag. 1867 [4] xxxiv. p. 15. 



2 Ibid. 1855 [4] x. pp. 354, 411. 



3 Crelle-Borchardt's Journ. f. Math. 1858, Iv. p. 25. 



