842 QUATRIÈME COMPLÉMENT X LA DIOPTRIQUE. 1668 — 1692. 



ai AllLifiunciilas inferit de Martis robore, de Veneris piilchrltudinc, quœ 

 frivolai '). 



The Heer Lceuwenhoeck of Delfc in Holland. hujusdiligcntiam inicrofcopicam 

 célébrât, eiimqiie le vidiiïe ait, et celaffe exquificiorcin microfcopij iifiim. qiiippe 

 qiiem fibi rcfervet*^. Credo nihil aliud eiïe quam liicis ufuni in res vifas fubtiliter 

 induftce. 



Nihil mirabilius aut jiicniidius fibi vifum ait quam fangiiinis circuitum in 

 Lacerta aqiiatica (angiiilla) ^) (apud Lceiiwenh, puto} de qiia obfervatione ait 



3tJ we are beholden to tbe Télescope; and that is, the wonderful Agreement whicli is found in 



gfiall theseveral Systems of onr Vortex; as well between tlie General System of the Sun and Pri- 

 mary Planets with the particular System o{ Saturais or Jupiter''s IManets, as between the par- 

 ticular Systems themselves , in this single Property , 'f/iat the Periodical Times ofthe Planets 

 Révolutions are in a sesquialtera Ratio of their Distances from the Centre of the IHanet about 

 •uohich they revolve. . . . This holds niost exquisitely true in Jupiter^s Satellites , as is noted by 

 the admirably learned Mr. Newton, in his incomparable Treatise, l'hilosophiie Naturalis 

 Principia Mathematica, Lib. 3. Ilypoth. 5. And the same Law of Motion is strictly observed 

 by the fivePrimary Planets, and the Earth about the Sun. As he notes, Hypoth.7,8. This 

 is also verifyed by Mons. Cassini'xn the five Satellites oiSattirn; as appears by his Account of 

 them in the Philosoph. 7">w7S/7f/. Num. 92. P. 5178. N. 133. P. 831.N. 181.P.79". 



')„Mars offers himself next; who, trusting in his own Strength, is attended by no Guards; But 

 the Prying Télescope discovers in his Face Sears, Spotsvc^à Rtiggedness'''' (p. 274). „Fenus, 

 the brightest Planet in the Ileavcns. She fears not sometimes even at Noon-day to display 

 her Beauty; and in this Armourreposing an entire Confidence, perforrnsher Course olone, 

 and free from ail othcr Attendants" (p. 275). „Mi?;T«r/s vvit and Quickness secureshim, 

 therefore he bas no Train , but generally shelters himself under the Beams of his potent Lord 

 the Sun" (p. 276). Dans le même esprit Molyneux écrivait à propos du phénomène men- 

 tionné un peu plus haut „j!/piter there stood by himself, inall Appearance, withouthis 

 Guards; and a bold Ltician might hâve puU'd him from his Throne without Résistance" 

 (p. 271). 



^} „The Heer Lewenhoeck of Delft in Holland, bas lately apply'd himself with great Diligence 

 to the use of iVIicroscopes : of vvhich Instrument he thinks he has a better kind than was ever 

 yet known. When I visited this Gentleman at Delft, he shew'd meseveral that indced were 

 very curious; but nothing more than what I had ordinarily seen before; beingcomposed 

 onlyofone single, very minute Glass-Sphere or Hémisphère, placed between two very thin 

 pierced Lamina, or Plates of Brass, and the Object was brought to its due distance before 

 the Glass by a fine Screw: But for his ^«/sort,he beg'd our Excuse in concealing them" 

 (p. 281). 



') „I hâve been often delighted with the curious Appearance of many Objects seen through the 

 Microscope. But none ever surprised me more, than the visible C/rwto/o» ofthe Blood in 

 Water-Newts (^Lacerta aquatica') to be seen as plainly asWater runningin a River, and 

 proportionately much more rapid" (p. 281). 



**) Celles pour le mois de décembre 1685. D'après cette communication, datée du 27 octobre 

 1685, il avait découvert lui-même ce phénomène depuis deux ans et demi et en avait envoyé 

 le 12 mai 1583 une description détaillée à son frère qui se trouvait alors à Leiden. 



