NEW CONCEPTIONS IN SCIENCE 



grouped together with the discoveries of Hertz and 

 Rontgen and the recent measurements of Professor 

 Blondlot, it will be seen that the hypothesis of a 

 space-filling substance rests upon a solid body of 

 observation. Hazarded as an economical mode of 

 thought a century ago, the evidence in its favor 

 has steadily accumulated, so that in the minds of 

 most physical investigators it is now considered as 

 well-grounded a theory as, let us say, the Darwin- 

 ian theory of natural selection. The comparison 

 is chosen advisedly. 



Taking up some mathematical calculations of 

 von Helmholtz, Lord Kelvin has suggested that 

 what we call matter might turn out to be incon- 

 ceivably minute whirls or "vortex-rings" in this 

 universal fluid. These rings would be similar to 

 the smoke-rings which are formed by puffing smoke 

 from the mouth, or those a locomotive often sends 

 into the air. The action of these rings has been 

 studied attentively by Professor J. J. Thomson and 

 others; some of their performances are curious in 

 the extreme. Two smoke-rings attract each other, 

 just as if they were little worlds like the earth and 

 the moon, and if in travelling across a room they 

 are stopped by an obstacle, they will move on again 

 when this obstacle is taken away. 



On the other hand, without indulging in theory 

 at all, a Norwegian physicist, Professor Bjerknes, 



82 



