294 PHILOSOPHICAL TRANSACTIONS. [aNNO 1 680. 



less time than those of Jupiter answering to them ; except the first, as may 

 be seen in the following table. 



Periods of the Satellites' Revolutions. 



d. h. m. d. h. m. 



The first of Jupiter in. . 1 18 29 The third of Jupiter in . . 7 4 



The first of Saturn in . . 1 21 19 The fourth of Saturn in 15 23 15 



The second of Saturn in 2 17 43 The fourth of Jupiter in 16 18 5 



The second of Jupiter in 3 13 IQ The fifth of Saturn in . . 79 21 O 



The third of Saturn in. . 4 12 27 

 By these discoveries, the admirable analogy and uniformity of the parts of 

 the universe are most evident, and the infinite wisdom and power of the Creator 

 is demonstrative to the contemplative mind. The discoverer considering that 

 the ancient astronomers had given the names of their heroes to the stars ; and 

 that Galileo, after their example, had honoured the house of the Medici with 

 the discovery of the satellites of Jupiter, which he made under the protection 

 of Cosmus II, calling them Sidera Medicea ; so in like manner M. Cassini 

 concludes that the satellites of Saturn are not unworthy to bear the name of 

 Louis le Grand, under whose reign and in whose observatory the same have 

 been detected, which therefore he calls Sidera Lodoicea. 



Two Observations of the Eclipses of the Planet Jupiter by the Moon. By Mr. 

 Hook, Mr. Halley, and Mr. Haines. N° 181, p. 85. 



The first was observed at Gresham College, London, by MM. Hook and 

 Halley, viz. on March 31, 1686, at night. At 9h. 33m. as near as could be 

 guessed, was the time of the central immersion, which was very difficult to be 

 observed, by reason of the asperity of the moon's limb, which undulated and 

 sparkled very much, as it appeared through the vapours near the horizon, so 

 that the contact of the limbs could with no certainty be determined : the ingress 

 happened much about the length of the spot, called by Hevelius Palus Mareotis, 

 to the north of the said spot, or about the 124th degree of the outer limb of 

 his Selenography, nearly in the same latitude with the moon's centre. — At lOh. 

 30m. the western edge of Jupiter began to emerge out of the dark limb of the 

 moon. — lOh. 31m. 20s. the whole disk of Jupiter was entire ; so that he was 

 about a minute and a third in coming out from behind the moon ; whence the 

 diameter of this planet may be determined. — The emersion was exactly in a right 

 line with the moon's centre, and the northern part of Palus Maeotis, or about 

 the 324th degree of the inner limb of the Selenographic Table of Hevelius. 



The other occultation happened May the 28th in the morning, or astronomi- 

 cally, the. 27th after midnight. 



