VOLTAIRE. 65 



effected. The Cartesian system is fully explained, and 

 the outline of optical science, independent of New- 

 ton's researches, is more extended and more elaborate 

 than the account of those researches. The second part 

 relates to the nature and action of light ; the third to 

 the system of the world ; and the first part enters at 

 some length into the general doctrines of mind, mat- 

 ter, force, and motion, even dealing with the doctrines 

 of natural religion. 



Whoever reads the work attentively, allowing it 

 the full praise so justly its due, will find it wholly in- 

 capable of furnishing any proof that the author had 

 ever read either the ' Principia ' or the * Optics.' There 

 is no reference to those writings which at all shows 

 that he had ever seen a line of them. In the contro- 

 versy with the Cartesians, which he carried on after 

 the ' Elements ' were published, he cites the 96th 

 proposition (meaning of the first book of the ' Prin- 

 cipia,' although he does not mention the book) ; but it 

 is only to speak of optical matters. He also refers to 

 the Scholium Generate ; but that has been constantly 

 cited, and for the most part at second hand, by those 

 who never read any other part of the work. It is 

 further to be observed, that no account whatever is 

 given, nor even any mention made, of the Second Book, 

 concerning motion in resisting media; indeed there 

 are indications more positive of his not having drunk 

 at the pure source itself. If he had been acquainted 

 with the Optics,' in describing the induction by which 

 the composition of white light is proved, he never 

 surely would have omitted the expenmentum crucis. 

 He gives (Part ii. chap. 10) the composition of the 



F 



