lb . p. 5179»5184.

H 3 . p. 831

( 368 )

This Digrestion belng treble to that os the Ordmary Satellite enabl’d us atfirst to judge the Time os his Revolution to be Quintuple, applying to theSatellites that Proportion, which Repi er hath noted in the Principal Planet s,betwcen the Periodical Pinses and their Difiances. We were asterwards con-firmed in this Opinion ; For by the Apparent Iwiftness os his Motion it waseaiieto see that this Planet had been in Conjunction with Satum,Feb. z. 1673.and by his Motion en the Wels it appears, that he was in the Inferior part oshis Circle : And because during this time os 17 Days he remov’d more and.more from Satum, ’tis certain that he remained in the tarne Quadrant os theInferior Occidental Circle above 17 Days, and that his whole Revolution ismore than 68 Days. He was these last Days at a Distoncc almost equal•to that which he had about the end os OBob. 1671; tö that in 480 days orthercabout he made a certain Number os Intirc Revolutions, which can beno more than 7; since each os themis without Question os more than 68days. If you sliould count 7 os them, each would be 68i Days; if youcount 6, each would be 80 Days; and if you count but 5, each would be96 Days. But this last Supposition can by no means be made to agree withthe two Observations of Dcc. 1672., and the first doth not agree tö well withthem as the Second.

M. CaJJini has since found that this Outermoft Satellite is distant from theCenter of Satum 1 oi Diameters of his Ring ; that the Period of his Revolu-tion in 80 Days is tö just, that he doth not Anticipate 9 Revolutions, whichare made in two Y ears, but by one whole Day ; and that in the Conjunctionswith Satum , his Latitude encreafes according as the RJng of Satum enlargethit seif ; though the Line of his Motion is not Parallel to the Circumferenceof the RJng.

M. Caffini hath alto diseovered, aster many Revolutions, that this Satellitehath a Period of Apparent Augmentation and Diminution , by which Period hebecomes viiible in his greatest Occidental Digrestion, and Invisible in hisgreatest Oriental Digrestion; he begins to Appear two or three Days beforehis Conjunction in the Inferior part, and to Disappcar two or three Days as-ter his Conjunction in the Superior part: So that he remains Invisible in eve-ry Revolution of 80 Days for a whole Month together.

This Viciilitude of Pbases makes it scem probable, that one part of his Sur-face is not to capable of Reflecting to us the Light of the Sun, which ma-keth it vifibl", as the other part is. Whence we may conjecture, that theGlobe of this Satellite hath tome Diversity of Parts Analogous to that of theEarth, the one part of whose Surfiice is cover’d by the Sea, which is not tö fitto Reflect from all parts the Light of the Sun, as the Continent which ma-keth up the other part: So that this Planet by a Convcrsion about hisAxis, or by an Exposition of the tarne Hemifphere to Satum (much aster themanner of the Hemifphere of the Moon to the Earth,) (ometimes turns tous the part Analogous toi the Continent, sometimes that part which anlwcrs tothe Sea.

LXXIX.