QUATRIÈME COMPLÉMENT X LA DrOPTRlQUE. 1668 — 1692. 84 1 



Pag. 261. de Galilei obfervatis. Pag. 264, de meis circa Saturnum. Til '°) de 

 [fie] incomparabel Chr. Hugenius bas put the laft hand to this afFair and in bis 

 ingénions Treatife, Syftenia Saturnium, Hag Com. 1659, 4° ,has publifhed to 

 the world a complète biftory of ail obfervations of tbis Planets appearances, with 

 a nioll ingénions Theory for tbeir explication. In the beginning of the year 1655 

 bis excellent Perfon firfi: difcovered de biggefl: ofSaturns Satellites with a tele- 

 fcope of 12 feet. cbarged with an eyeglass of 3 inches. afterwards an. 1656 be 

 doubled that lengtb, retaining the famé eyeglas &c. addit Halleium correxifle 

 motum mei comitis Saturnij "), nefcio quam bene, nam ab eo Caflînus diffentit. 

 ego médius ut puto inter utrumque"). Galletij ineptam hypothefin qua ad 

 Saturni annukim exprimendum ufus eft refellit, quae hoc nonmeretur ''). 



Pag. 271 refert obfcrvationem fuam qua fatellites Jovis omnes latuerint nempe 

 a°. i68i.nov.2. hora 10 p.m. Dublinii St. Vet. quod Flamftedium fuis numeris 

 convenire invenerit. 2dus poft Jovem , reliqui ante difcum. 



Pag. 270, rationem periodorum ac diftantiarum commémorât , quam debuifîct 

 Ceplero referre acceptam '*). 



') Comparez la p. 513 du Tome présent. 



'°) Voici ce qui précède le passage cité: „Galihû was the first that observed any thing extra- 

 ordinary in >S«/»r«5 Appearance Jn. 1610. Oc/oè.&s he tells us in some oïhxs Italian Letters: 

 But his Classes were too short to give the true Shape of this Planet. AU thathe descry'd was 

 something appendent on each side of hini, which he toolc to be two Globes much less than 



Saturni own Body But when the Télescope was better advanced. ... the true and 



genuine Appearance of Saturn began to shew it self, and its regular Changes were taken 



'„ notice of. But though several Authors writ Treatises of this surprising Appearance, and 

 particularly the celebrated Hevelius (de nativa Saturni facie) Hodîerna , &c. yet ail their 

 Observations were imperfect and déficient; and chiefiy for want of excellent Classes :Till 

 the", etc. 



") Voici, en effet, la suite du passage en question „TheiS'tf/e//;7hediscover'd, isthei^uw/^ 

 ùomSaturn; and in the forenamed Treatise, he gives us Û\tEpocha and Tablesoï\Xs Motion; 

 But our most ingénions Countryman, Mr. Halley, deservedly celebrated for his Astrono- 

 mical Labours, discovered in the year i68a. that Hugenius's Numbers were considerably 

 run out; and therefore he set himselfto correct the Period of this i'«/<?////, which hehas 

 done accordingly,Num. 145. Pag. ^z.Philoioph. Transacf. And in Num. 187. Pag. 299, we 

 shall find Mons. Cassint''s Tables ofthe Motions of ail Saturns 6'(7/f////«, together with 

 their distances from Saturn correspondent to their Periodical Times". 



") Contrairement à la pensée de Huygens, Halley et Cassini arrivent tous les deux, aux lieux 

 cités dans la note précédente, à un mouvement moyen journalier de 22° 34' 38", c'est-à- 

 dire à une durée de la révolution sidérale du satellite de Huygens de 15) 221- 41'". Huygens 

 dans le „Systema Saturnium" avait trouvé 151 22'' 39"". Ajoutons que les observations 

 modernes confirment les résultats de Halley et de Cassini. 



'3) Voir sur Callet et sur son hypothèse les pp. 46, note 4, et 494 du T. VHI. Molyneux n'em- 

 ploie pas moins de quatre pages (p. 265 — 269) à la réfutation de cette hypothèse. 



'*) Voici ce passage, où, en effet, Kepler n'est pas nommé: „But before I kave i'^/ww and 

 Jupiter, I cannot but take notice of one admirable Property for the Knowledge whereof, 



106 



