THE STORY OF NINETEENTH-CENTURY SCIENCE 



thetical mistiness has been reared the most tenable 

 theory of the constitution of ponderable matter which 

 has yet been suggested or, at any rate, the one that 

 will stand as the definitive nineteenth-century guess at 

 this " riddle of the ages." I mean, of course, the vortex 

 theory of atoms that profound and fascinating doctrine 

 which suggests that matter, in all its multiform phases, 

 is nothing more or less than ether in motion. 



The author of this wonderful conception is Lord Kel- 

 vin. The idea was born in his mind of a happy union 

 of mathematical calculations with concrete experiments. 

 The mathematical calculations were largely the work of 

 Hermann von Helmholtz, who, about the year 1858, had 

 undertaken to solve some unique problems in vortex 

 motions. Helmholtz found that a vortex whirl, once es- 

 tablished in a frictionless medium, must go on, theoret- 

 ically, unchanged forever. In a limited medium such a 

 whirl may be Y-shaped, with its ends at the surface of 

 the medium. We may imitate such a vortex by drawing 

 the bowl of a spoon quickly through a cup of water. 

 But in a limitless medium the vortex whirl must always 

 be a closed ring, which may take the simple form of a 

 hoop or circle, or which may be indefinitely contorted, 

 looped, or, so to speak, knotted. Whether simple or 

 contorted, this endless chain of whirling matter (the 

 particles revolving about the axis of the loop as the par- 

 ticles of a string revolve when the string is rolled be- 

 tween the fingers) must, in a frictionless medium, retain 

 its form, and whirl on with undiminished speed forever. 



While these theoretical calculations of Helmholtz were 

 fresh in his mind, Lord Kelvin (then Sir William Thom- 

 son) was shown by Professor P. G. Tait, of Edinburgh, 

 an apparatus constructed for the purpose of creating 



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