CONCEPT OF AN ATOMIC UNIVERSE 139 



So far as mere philosophical reasoning could carry him, he had 

 the second as well. Ideas of force and energy were nebulous 

 enough in those days. Forces could hardly be studied before 

 they were known. Of electricity the ancients knew practically 

 nothing at all ; of magnetism, but little more. They had 

 observed, of course, that some substances, like amber, repelled 

 or attracted light particles when they were smartly rubbed up 

 with flannel or cat's fur ; but the idea of associating this with 

 lightning of the thunderstorms on the one hand, with light 

 and heat on the other, probably never entered their minds. 

 Nor could they have had any very clear idea of the relations 

 of electricity and the actions of the magnet. 



Nor, again, could very definite ideas of energy arise before 

 they had developed the science of dynamics and begun to invent 

 and to use varied machines. It was beyond the powers of 

 any man, therefore, then to conceive the doctrine of the con- 

 servation of energy at least in its modern sense that is, the 

 idea that there is no motion, no force, no power to do work which 

 is ever " lost " fo the universe ; that energy, as little as matter, 

 cannot be created nor destroyed. Yet the idea in all its 

 essentials Democritus had unequivocally attained. He had 

 reached even the distinction between force (SiW/xis) and energy 

 (wfpyem) which we regard as a fruit of our own time. 



His ideas waited many centuries for definitive experimental 

 proof ; but that in no wise detracts from the merit of his 

 genius. He was the father of modern physics and of modern 

 chemistry as well. True, the idea of chemical affinity, of 

 attractions among the atoms, did not come into his system ; 

 that was reserved for a later day. But, Empedocles' vague 

 poetical concept of loves and hates among the atoms disre- 

 garded, there was no one, apparently, among the ancients who 

 got any further than he. When in our modern time men again 

 began to turn their minds to physical problems, it was to begin 

 where Democritus left off. 



The Abderan philosopher founded no school. His philo- 

 sophy and his system were far too severe for the volatile and 

 phrase-loving Greek mind. So we find here, as in the field of 

 astronomy, that a space of eighteen or twenty centuries inter- 

 venes before any further progress is made before, indeed, there 

 was apparently any further thought upon the subject at all. 



In the sixteenth and seventeenth centuries we find philo- 



