92 NOTES TO BOOK I. 



undulatory theory of light, we see that both involve the 

 same Idea ; the Idea of a Medium acting by certain 

 mechanical properties. The question there is, what is 

 the true view of the mechanism of the Medium I 



The other example of Aristotle's failure in physics, 

 given in p. 82, namely, his attempted explanation of the 

 round image of a square hole, is a specimen rather of in- 

 distinct than of inappropriate ideas. In the first edition 

 I had not accurately represented Aristotle's statement. 



The geometrical explanation of this phenomena, which 

 I have inserted in the text, was given by Maurolycus, and 

 before him, by Leonardo da Vinci. 



