Mercury sets 20 minutes after sunset at the beginning of the month, the interval increasing. Venus may be observed on the 1st for about three hours and a quarter after sunset, the interval increasing. Mars sets about an hour after midnight on the Ist, the interval decreasing to half an hour after midnight on the 31st. Saturn sets a quarter of an hour before midnight at the beginning of the month, and then earlier each night. On the last day he sets just before 10 p.m. He is at quadrature with the sun on the 5th. LUNAR OBJECTS SUITABLE FOR OBSERVATION IN DECEMBER, 1877. BY W. R. BIRT, F.R.A.S., F.M.S. The lunar area to the north of II. I. r (see Astronomical Register Nov., p. 302) is II. I. w, which contains the western portion of the northern part of the valley J. J. Cassini, registered by the symbol II. I. ∞ I. The north part of the west wall being II. I. w 2. Just exterior to this wall on the west rises the peak of Schröter, y of B. and M. and Neison, its symbol is II. I. w 4; Schröter represents it as a mountain spur from the wall II. I. w 2 of J. J. Cassini, with a long shadow towards the west; B. and M. as a triangular table-land or plateau, the apex towards the south and steep sloping sides east and west. Neison says this plateau is crowned by three peaks, that on the west, II. I. w 6 being 8,729 English feet high, those on the east 7,328 and 5,480 English feet, these two are included in the symbol II. I. w 7 as that of the east side of the plateau. To the south of this plateau and apparently branching westward from the wall of J. J. Cassini is a mountain II. I. w 5 rising to the height of 3,200 English feet, it is situated in N. lat. 71° 40' and 17° 24′ E. long. Schröter appears to have overlooked it. II. I. w 3 is a peak on the east border of Anaxagoras, attaining an altitude of 9,528 English feet. The terminal basin of J. J. Čassini, H of Schröter and Anaxagoras y Bn Z of B. and M., as given by Schafarik in the October number of the Astronomical Register, p. 265, being near the north pole, occupies a large space, viz., from 22° to 50° E. long. The peaks B (not ẞ as given by Scafarik) is in 22° E. long., 78° N. lat.; n is in 41 E. long., 82 N. lat., and Z in 50° E. long., 82° N. lat. The symbols are respectively of B II. N. & 1, of n II. O. i 1, of Z II. O. & 1. From this latter point the east wall crosses the meridians of 45' to 30° E., whence it wends south-west until it reaches area II. I. This area includes the eastern portion of the northern part of the valley J. J. Cassini II. I. with its wall II. I. 2, also a peak on this wall situated in N. lat. 70° 34' E. long. 22° 40', E Errata.- October list, par. II. I. § 3, last line but two, for position read portion. November list, second par., last line, for v read the Greek upsilon. Next par., line 3, for heights read height. Buckhurst Hill: November 16, 1877. THE FIVE INNER SATELLITES OF SATURN. Longitudes of the five inner satellites reckoned from upper conjunction, and expressed in decimal fractions of a revolution. To find the longitudes for other hours and the corresponding places of the satellites v. the tables p. 278. Approximate times of some of the conjunctions of the satellites with the ends of the ring, v. p. 279. 1877. Gr. M. Time. 1877. Gr. M. Time. h. Dec. I 50 Encel. W. 8.9 Dione. np. To watch the shadow of Titan crossing the central meridian of the disc of Saturn, observers must be on the alert on Dec. 9, about 64h., and on Christmas Day about 54h. G. M. T. Japetus is, during December, on the preceding side of Saturn, reaching on Dec. 16 its greatest western elongation. A. M. We are obliged to postpone several valuable articles through want of space. We cannot publish communications which are not authenticated by the name and address of the sender, as a guarantee of good faith. When subscriptions sent by post are not acknowledged in the next number, the Editor will be much obliged if subscribers will at once inform him of the fact. All Letters requiring an answer must enclose a penny stamp. The Editor will be obliged if those gentlemen who have not paid their subscriptions will kindly send them by Cheque, Post-office Order, or penny postage stamps, but the Editor will not be liable for loss in transmission. Post Office Orders for the Editor are to be made payable to JOHN C. JACKSON, at Lower Clapton, London, E. The Astronomical Register is intended to appear at the commencement of each month; the Subscription (including Postage to all parts of Great Britain and Ireland) is fixed at Three Shillings per Quarter, payable in advance, by postage stamps or otherwise. The pages of the Astronomical Register are open to all suitable communications. Letters, Articles for insertion, &c., must be sent to the Rev. J. C. JACKSON, Clarence Road, Clapton, E., not later than the 15th of the Month. |