TOL. v.] PHILOSOPHICAL TRANSACTIONS. 42p 



unless we suppose it a librating or moving point: but that the equable motion 

 of a planet cannot be more properly assigned to any point than the superior 

 focus. No person has yet denied that Kepler's areas do satisfy the appearances; 

 but since neither he himself, nor any after him, could determine them by a di- 

 rect calculus, some have blamed Kepler as giving way too much to physical 

 causes, and swerving from geometry: as if physical causes were inconsistent with 

 it; or, as if the problem were two ungeometrical, which, without mentioning 

 physical causes, is thus proposed: TJw area of the trilinear Jigure intercepted be- 

 tween the line of the apses and tfmt of the tnie motion^ and the elliptical periphery^ 

 being given ; to find the angle at the sun. 



M. Bulliald attempted to investigate by geometrical reasonings, both the orbit 

 and the degrees of remission and intention in the motion of the planets; that 

 we might be led from that equable motion, assumed by astronomers before 

 Kepler's time, to that inequality observed in the heavens. And bishop Ward, 

 adopting this hypothesis, first shows how to do the like with the line of the 

 equable motion revolved round the other focus of the ellipsis, and then gives 

 that method of direct calculation, which we have repeated above. And two 

 years after, the illustrious Count Pagan undertook to maintain the truth of this 

 hypothesis, so far, that he ascribed the difference observed about the octants, to 

 the unskilfulness of astronomers. But M. Bulliald, upon second thoughts, and 

 considering that astronomical observations were the best guides, upon applying 

 some limitation to his former inventions, made that difference vanish. ^yV^hence 

 then it appears, that that hypothesis, on which M Cassini builds the investiga- 

 tion of the apogees and eccentricities, deviates so far from the truth, as is stated 

 by that limitation of Bullialdus.* 



An Account of three Books. iV** 57, p- 1175. 



I. Esperienze intorno alia Generatione Degl' Insetti, fatte da Francisco 

 Redi,-!- Academico della Crusca. In Firenze, 1668, 4to. 



* In this state of uncertainty remained the difference between the old hypothesis and the phaeno- 

 mena or observations, till Newton demonstrated in his Principiaj that the planets must move in ellip- 

 tical orbits, and that they must describe elliptical areas always proportional to the times. 



f The notes upon Redi's experiments on vipers, at p. 58 of this vol. having, for the better elucida- 

 tion of that subject, been extended to some length, it was deemed proper to postpone a biographical 

 account of this author until another opportunity of introducing it should present itself. This oppor- 

 tunity now occurs. 



Francis Redi, not more distinguished by his scientific labours than by his poetical talents and clas- 

 sical acquirements, was descended from an ancient and honourable family, and was bom at Arezzo, 

 in 1626. He studied tlie profession of physic at Pisa, and soon brought himself into notice by his 

 writings, the fame of which procured him the appointment of physician to Ferdinand JI. and afterwards 



