444 Transits of Jupiter's Satellites. — Occultations. 



ancient neighbour; a relation frequently obtaining in these 

 configurations. Close S.E. of it our guides notice a dark spot 

 in the Full Moon ; an exemplification of our recent remarks. 

 The ring of Gay Lussac is interrupted by a minute crater close 

 to- the companion- crater A; and they point out a curious 

 arrangement here : three pairs of objects — A and this little 

 pit — two summits (a) close together on the N.W. slope of the 

 ring — and two others (/3) on the E., make up respectively two 

 equilateral triangles, with sides parallel and very close toge- 

 ther, whose common centre coincides with that of Gay Lussac 

 itself. The cleft proceeding from it has already passed under 

 our review. The mountains E. are confused in arrangement, 

 with no central axis ; and are penetrated by valleys usually as 

 luminous as the heights. Measurement is difficult from the 

 way in which the shadows fall. One high promontory reaches 

 6300ft. Towards the E. extremity lies a considerable crater, 

 Tobias Mayer, 22 miles in diameter. A summit of its W. ring- 

 rises 9700ft. above the cavity. Schr. pointed out that in con- 

 sequence of its position on the mountain's flank, its E. side 

 was much lower — he gave it but 2700ft. (short measure). It 

 has a central hill, which from local colour appears large in 

 Full Moon. S.E. of this the map shows a very minute crater 

 in the depth ; rather an unusual position. W. of the ring lies 

 a conspicuous sub-crater, as it might perhaps be termed, 

 Mayer a. The extremity of the mountains N.E. of Mayer 

 rises to 4000ft. — Milichius, a small bright (8°) crater lies in a 

 curiously-shaded region of the M. Imbrium (I), nearly S. of 

 Mayer and E. of Copernicus. S.S.E. of this is another similar 

 crater, Hortensius, very remarkable for its isolation, and the 

 luminosity surrounding it, almost like a miniature streak-system. 

 In a position forming a right-angled triangle with the two last 

 objects — the right angle being towards Copernicus — is a spot 

 containing within the compass of less than 30 miles eight 

 parallel ridges running nearly N. and S., and all pretty nearly 

 of similar length and elevation. 



Another step S.W. brings us from Hortensius to Reinhold 

 again, and completes the circuit of a region where so much is 

 seen, and so little is understood, of the wonderful works of God. 



TRANSITS OF JUPITER'S SATELLITES. 



Jan. 1st. I. egress, 5h. 11m. — Ditto shadow, 6h. 16m. — 

 5th. II. shadow ingress, 5h. 50m. II. egress, 6h. 84m. — 

 8th. I. shadow ingress, 5h. 53m. I. egress, 7h. 12m. — 

 12th. II. ingress, Oh. 29m. — 15th. I. ingress, 6h. 54m. — 

 24th. I. egress, 5h. 45m. — Ditto shadow, Oh. 31m. — 30th. 

 II. shadow egress, 5h. 45m. — 31st. I. shadow ingress, 6h. 8m. 



