THE STORY OF NINETEENTH-CENTURY SCIENCE 



heaping hypothesis upon hypothesis, as before. Still, a 

 hypothesis that violates no known law and has the war- 

 rant of philosophical probability is always worthy of a 

 hearing. Only we must not forget that it is hypothesis 

 only, not conclusive theory. 



The same caution applies, manifestly, to all the other 

 speculations which have the vortex atom, so to say, for 

 their foundation-stone. Thus Professors Stewart and 

 Tait's inferences as to the destructibility of matter, based 

 on the supposition that the ether is not quite frictionless, 

 Professor Dolbear's suggestions as to the creation of 

 matter through the development of new ether ripples, 

 and the same thinker's speculations as to an upper limit 

 of temperature, based on the mechanical conception of 

 a limit to the possible vibrations of a vortex ring, not 

 to mention other more or less fascinating speculations 

 based on the vortex hypothesis, must be regarded, what- 

 ever their intrinsic interest, as insecurely grounded, until 

 such time as new experimental methods shall give them 

 another footing. Lord Kelvin himself holds all such 

 speculations utterly in abeyance. "The vortex theory." 

 he says, " is only a dream. Itself unproven, it can prove 

 nothing, and any speculations founded upon it are mere 

 dreams about a dream." 



That certainly must be considered an unduly modest 

 pronouncement regarding the only workable hypothe- 

 sis of the constitution of matter that has ever been 

 imagined; yet the fact certainly holds that the vortex 

 theory, the great contribution of our century towards 

 the solution of a world-old problem, has not been car- 

 ried beyond the stage of hypothesis, and must be passed 

 on, with its burden of interesting corollaries, to another 

 generation for the experimental evidence that will lead 



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