ACHILLES AND THE TORTOISE. 



to a continuation of this process was the im- 

 perfection of our instruments of crushing and 

 observation. That meant that there was no 

 natural limit to the divisibility of substances. 



For more than a hundred years now, how- 

 ever, since D alt on promulgated his great atomic 

 theory, we have been accustomed to think 

 we had scientific evidence that all things are 

 constructed of similar small portions of definite 

 size, called atoms, which are indivisible and 

 indestructible, so that with their separation 

 the process of subdivision must stop not 

 accidentally, because of the limitations of 

 our instruments, but of necessity, because of 

 the natural structure of things. 



Of late years, it is true, this theory has [had 

 to be revised. There has been reason to think 

 that the Crookes tube, which produced Rontgen 

 rays, contained matter in a finer state of divi- 

 sion than atoms, that atoms within it were 

 broken up into corpuscles or radiant matter, 

 as it was called. This view has been strongly 

 confirmed by the study and explanations of 

 the phenomena connected with radium and 

 similar substances. And it may yet become 

 necessary to accept the divisibility of corpuscles 

 into still finer portions of matter. 



But the habit of a hundred years being still 

 strongly upon us, and being itself a natural 

 mode of connected thought, having been very 

 fully realised by Democritus and Lucretius 



277 



