OF THE COSMOS. INTRODUCTION. 19 



tractoria) extends as far as the Earth ; and he even says 

 that this force, " similar to that which the magnet exercises 

 upon iron/' would deprive the Earth of water, if the Earth 

 itself ceased to attract the water. Unfortunately, ten years 

 later, in 1619, this great man, perhaps out of deference to 

 Galileo, who ascribed the ebb and flow to the rotation of the 

 Earth, gave up the true explanation, and in the Harmonice 

 Mundi described the Earth as a living animal whose whale- 

 like respirations, in periodical alternations of sleeping and 

 waking dependent on the solar time, cause the swelling and 

 sinking of the ocean. The profound mathematical genius, 

 recognised by IJaplace, which shiiies forth in one of Kepler's 

 writings ( 33 ), makes us regret that the discoverer of the three 

 great laws of all planetary movement did not persevere in 

 the path, in which his views respecting the attraction of 

 masses had led him to enter. 



Descartes, furnished with a greater variety of knowledge 

 in the natural sciences than Kepler, and himself the founder 

 of several parts of a mathematical system of physics, under- 

 took to embrace the whole world of phsenomena, the ce- 

 lestial sphere, and all that he knew of animate and inanimate 

 terrestrial Nature, in a work to which he gave the names of 

 "Traite du Monde" and "Summa Philosophise." The 

 organization of animals, and particularly that of man, for 

 the understanding of which he pursued for eleven years a 

 systematic course of anatomical study, ( 34 ) was to form the 

 concluding portion of the work. In his correspondence 

 with Father Mersenne, we find many complaints of the 

 slow progress of the undertaking, and of the difficulty of 

 arranging and combining such numerous materials. This 

 Cosmos, which. Descartes always called his World (son. 



