THALES TO LINNAEUS 18 



nothing and his work is preserved mainly 

 through his influence on Plato. 



Leukippos and Demokritos are linked to- 

 gether through their statements of the atomic 

 theory, made more than twenty centuries be- 

 fore Dalton. They placed the permanent 

 reality of things in numberless atoms, of which 

 Leukippos said "there are an infinite number 

 of them, and they are invisible owing to the 

 smallness of their bulk." 



Plato we shall pass by ; his metaphysical doc- 

 trine of ideas contributed little of value to the 

 solution of the riddle of the universe. 



We now come to the great Stagirite, Arist- 

 otle, founder of the experimental school and 

 father of natural history. Born in 384 B. C, he 

 entered the Academy under Plato when a boy 

 of eighteen. When he was thirty-six Plato 

 died, and Aristotle then left Athens. At forty- 

 one he became the teacher of Alexander the 

 Great. He was the greatest of all the Greeks, 

 and his studies took a wider range than had 

 been embraced by any previous thinker. 



Stageira, where he spent his boyhood, was 

 on the Strynomid gulf, and here he observed 

 the variations and gradations between marine 

 plants and animals. It is an evidence of his 

 keen insight that he classified the sponge as an 

 animal. Compare this with Agassiz, the op- 



