52 HISTORY OF MECHANICS. 



others of his predecessors and contemporaries, had 

 speculated concerning the problem of Percussion, 

 he did not arrive at any satisfactory conclusion; 

 and the problem remained for the mathematicians 

 of the next generation to solve. 



We may here notice Descartes and his Laws of 

 Motion, the publication of which is sometimes 

 spoken of as an important event in the history of 

 Mechanics. This is saying far too much. The Prin- 

 cipia of Descartes did little for physical science. 

 His assertion of the Laws of Motion, in their most 

 general shape, was perhaps an improvement in 

 form; but his Third Law is false in substance. 

 Descartes claimed several of the discoveries of Ga- 

 lileo and others of his contemporaries ; but we can- 

 not assent to such claims, when we find that, as 

 we shall see, he did not understand, or would not 

 apply, the Laws of Motion when he had them 

 before him. If we were to compare Descartes with 

 Galileo, we might say, that of the mechanical truths 

 which were easily attainable in the beginning of 

 the seventeenth century, Galileo took hold of as 

 many, and Descartes of as few, as was well pos- 

 sible for a man of genius (B). 



