208 HISTORY OF PHYSICAL ASTRONOMY. 



and not to the center. The asserters of vortices 

 often tried their skill in remedying this vice in the 

 hypothesis, but never with much success. Huy- 

 ghens supposed the ethereal matter of the vortices 

 to revolve about the center in all directions ; Per- 

 rault made the strata of the vortex increase in 

 velocity of rotation as they recede from the center; 

 Saurin maintained that the circumambient resist- 

 ance which comprises the vortex will produce a 

 pressure passing through the center. The elliptic 

 form of the orbits of the planets was another dif- 

 ficulty. Descartes had supposed the vortices them- 

 selves to be oval; but others, as John Bernoulli, 

 contrived ways of having elliptical motion in a 

 circular vortex. 



The mathematical prize-questions proposed by 

 the French Academy, naturally brought the two 

 sets of opinions into conflict. The Cartesian Me- 

 moir of John Bernoulli, to which we have just 

 referred, was the one which gained the prize in 

 1730. It not unfrequently happened that the Aca- 

 demy, as if desirous to show its impartiality, divided 

 the prize between Cartesians and Newtonians. Thus 

 in 1734, the question being, the cause of the in- 

 clination of the orbits of the planets, the prize 

 was shared between John Bernoulli, whose Memoir 

 was founded on the system of vortices, and his son 

 Daniel, who was a Newtonian. The last act of 

 homage of this kind to the Cartesian system was 

 performed in 1740, when the prize on the question 



