VOL. XVI.J FHILOSOPHICAL TRANSACTIONS. 419 



to be that which has least vacuity. A bubble a rarer fluid in a more solid, a 

 drop a denser fluid in a more rare. His position is, that a dense body is more 

 potent than a rare. His supposition is, that in a body mixed of these two, both 

 endeavour to recede from the centre of it ; and thence his first proposition is, 

 that the most dense parts will get out most, the less dense will remain in inner 

 stations, which he calls natural. 2. He supposes, any other body immersed in 

 this will find and take its natural station, according to its comparative density , 

 the endeavour to go to this natural station, if downwards, is gravity, if upwards, 

 is levity. The conflict between the included and passing particles will create a 

 vortex, whose included matter will move exac^y as the elliptical hypothesis of 

 the planets supposes, and answer not only to that but to any other hypothesis. 

 To many other fanciful explanations he adds four new lemmas, which he applies 

 to the explication of Cartesius's system, supposing the matter between the vor- 

 tices that join to that of the sun, to influence that by its ingress, so as to keep 

 the sun in the focus of the elliptic vortex. This premised, he subjoins his first 

 lemma, where he presents the sun in the centre of gravity of its system, with- 

 out vortex or turbinated motion ; in the second, he directs it to the focus of the 

 ellipse ; in the third, he generates the vortex by the conflict of the entering and 

 contained matter, exactly agreeing with the phaenomena, and turns round the 

 sun by the motion of the vortex, giving the planets their exact motions, which 

 they cannot deviate from. 



Lastly, he generates earths or planets by the coalition of many smaller into 

 greater bodies ; these he explains more particularly from his principles, and then 

 answers two objections which may be made against it, and a third, which a 

 demonstration of Mr. Newton's, upon a supposition of his, directly opposes ; 

 to which he answers, that that hypothesis ought to be corrected, and gives his 

 reasons, which he thinks sufficient. He disapproves of the hypothesis of the 

 planets gravitating upon each other, and explains his reasons from the similitude 

 of a ship in the water; and ends his epistle with this conclusion, that though 

 the moon were a thousand times larger than the earth, it would not be able to 

 move the least sand out of its place if that were the centre of the earth. The 

 like he supposes of the other planets, with respect to the sun. 



//. Tabularum Aslronomicarum Pars prior, de Motihus Solis et Lunce, necnon de 



Positione Fixarum, ex ipsis Observationibus deductis, cum Usu Tabularum, dfc. 



^uthore Ph. de la Hire, Regio Matheseos Professore ac Regite Scientiarum 



ylcademicB Socio. Ate. Par. 1687. N° IQl, p. 443. • 



This author, long since eminent for his skill in geometry, now succeeds the 

 accurate Mr. Picart in the Royal Observatory at Paris, and this book is the first 



3 H 2 



