8,9

a very rugged portion of high land, forming part of the southeast boundary of the Mare Nubium.

"Cichus, 189, on index map, a crater opened in table land, lies 9000 feet beneath the plateau, 4000 feet below the plain; its ring is perforated by a smaller crater, an object of great interest. In 1833 I perceived that it was twice as large as it had been represented three several times by Schröter. On becoming possessed of the great map, I found it there also enlarged. Schröter, though a clumsy, was a faithful draughtsman; his views have the appearance of being each independently drawn, and they are under different angles of illumination, which often vary the size of small craters, so that here is fair evidence of volcanic action since 1792; the silence of Beer and Mädler being characteristic, goes for little or nothing."

Webb gives two figures; one, copied from Schröter's design, 1792, Jan. 4; the other, taken from Beer and Mädler's map. I am not in possession of Schröter's.

II. Cichus A, marked C in Beer and Mädler's map, a small but deep crater on the south-east margin of the ridge of Cichus. This small crater should be most carefully watched and measured; only a portion of the margin was seen this morning, as a projecting tongue of light into the dark shadow within the larger crater.

III. A crater north of Cichus, given in the small German map, but singularly omitted in the large map. There is a very obscure marking in the neighbourhood of the fault next to be described, where I saw the crater exceedingly well defined; but it has on the map not the remotest resemblance to a crater: it is situated between two mountain masses marked ẞ and y. This is also an object that requires close attention.

IV. A fault north-east of III., forming the south-west portion of a somewhat narrow triangular mass of very high land, about 5000 feet; see quotation from Webb. It is also very rugged. This mass of high and rugged land is well shown on the large German map.

V. A small crater west of Cichus, marked B on the large German map.

VI. A crater near the boundary of the Mare Nubium, forming with III. and V. an isosceles triangle, III. and V. being the base. The position of this crater, as I saw it, does not accord with its position on the large map. I apprehend it to be really more southerly than marked by Beer and Mädler. Westward of this are four small craters, which I failed to see. Query, were they too much advanced on the terminator?

VII. A portion of high land, on the south-east extremity of which e (VI.) is situated. The small German map gives a ridge hereabout; it does not, however, terminate as I saw it. It is very much better delineated on the large map.

VIII. A crater marked A on the large map, on the east edge of Hesiod, which is now on the terminator. Its outline is perceptible, but the floor is in perfect darkness.

9, 10

XI. A small crater nearly, but not quite, in a line with VI. and X., also given in the German maps, but delineated in the larger map as being much more diminutive in comparison with the craters in its neighbourhood than I saw it. It is undesignated, probably as having been an inconspicuous object at the date of Beer and Mädler's labours.

XII. A small serpentine mountain chain between X. and XI. given in the German maps.

XIII. A rille or canal brought out most exquisitely by the Hartwell telescope, but no traces of its consisting of minute craters, although examined with a power of 416. The utmost I could detect was a very narrow gutter-like formed canal running north-west and south-east, or thereabout, from Hesiod to near the steep and rugged south-east boundary of the Mare Nubium, the north-east interior slope being in shadow, the south-west in sunshine. I estimated it to be somewhat about a mile wide. It is well delineated on the German map, and is marked d.

XIV. A short mountain-range running nearly at right angles from one extremity of the triangular mass of high land, described at IV., and at right angles generally to the steep and rugged boundary of the Mare Nubium, to the two craters Mercator and Campanus. It is given very distinctly on the larger map.

XV. A small conical mountain (?) very apparent north-east of, and closely abutting on, the rille or canal XIII. (♪). This is not given on the German map, and no traces whatever can be seen on the larger map. It would be well to watch very closely the neighbourhood of this mountain, especially as the surface of the Mare is exceedingly smooth, north-east of the canal.

XVI. Western edge of the high land forming the southwest part of the mass on which Cichus is situated; shown on the large map.

From VI. in the direction of X. towards XII., and as far as XIV., the surface is studded with small mountains (hillocks in comparison with the larger mountain masses), clearly separating the smoother spaces within IX. and XVI. from the general surface of the Mare. This appearance of being thus studded is shown on the larger map. The space between IX. and XVI. being separated from the general surface has greatly the appearance of having been a portion of a large ancient crater, probably broken up by the formation of this portion of the boundary of the Mare Nubium.

The above described observations were made with Dr. Lee's great Equatoreal, object-glass by Tully, on July 30, 1861, between 13 and 15 hours G.M.T. Power employed 240.

The Lunar Crater Plato.

Mr. Birt communicated a series of observations of this wellknown crater, embracing a period of eighteen months, viz., from January 1860 to July 1861, which he had arranged according to the Moon's age, so that they not only served as a record of the past, but can also be used as an Ephemeris, indicating to the observer the appearances likely to be seen, and thus form the basis of an accurate course of observations on

N.P.D. from
Observation.

93 56 7'94 95 22 52 42

N.P.D. from
Observation.

0 / "

97 36 41°29 97 51 51'54 98 43 11.06

N.P.D. from Observation.

0 1 2

89 55 19:32

15, 16

Places of the Comet II., 1861, from Sextant-Observations of the Distances of the Comet from Fixed Stars, made by Commander A. L. Mansell, R.N., commanding H. M. S. Firefly.

(Communicated by the Astronomer Royal.)

A short time since, the Admiralty placed in my hands a sheet of observations of the distances of the Comet II., 1861, from fixed stars, made by Commander A. L. Mansell, accompanied with the particulars which were absolutely necessary for their reduction, but with nothing tending to facilitate the reduction. At my request, the Rev. George Fisher most kindly took charge of the observations, and under his care they were reduced by the Officers of the Greenwich Hospital Schools.*

The observations were made on board H.M.S. Firefly, her anchorage being within a quarter of a mile of the observatorystation used in the survey of Sidon, the position of which islatitude 33° 34" 26' N., longitude 35° 21′ 39′′ E. The latitude is determined from a mean of four meridian altitudes of a and B Libræ south of the zenith, and ten observations of Polaris, using the Nautical Almanac method. The longitude is determined from three good meridian distances from Beirut, using eight chronometers; Beirut being fixed by a mean of seven meridian distances, using seven chronometers, run between it and Malta. The longitude of Malta is deduced from that of the Observatory at Palermo. [It will be remarked, in the subsequent computations, that a small error of latitude produces no error in the deduced place of the comet, except in so far as it alters the computed altitude of the star and comet, and therefore slightly alters the refraction and the correction of distance; and a small error of longitude produces no effect, except in the correction of distance for refraction, and in the computation of the comet's place from the Ephemeris.] Mean time was determined by equal altitudes of the Sun on the 2d and 8th of July. is a good pocket-chronometer, by French: it has how3063 ever always been compared with the standard chronometer (Dent, 1793), which watch shows a good mean of the nine chronometers.

210

The elements given are-the Greenwich mean time of each observation, and the observed distance, index-error, and corrected apparent distance.

It does not appear necessary to give all the numbers of the observations, or the troublesome reductions, but it may be proper to describe the method pursued:

1. The Comet's R.A., N.P.D., and log. distance were interpolated from the Ephemeris published by M. Le Verrier in the Bulletin. The hour-angle being found, the true altitude was computed; and by calculation of refraction and parallax, the apparent altitude was found.

2. The Star's R.A. and N.P.D. being taken from the Nautical Almanac, its true altitude was computed, and by calculation of refraction the apparent altitude was found.

3. From the two apparent altitudes and the measured distance, with the corrections of altitudes, the true distance was found by the usual method of clearing Lunars.

4. The distances of the Comet from the two stars were measured at different times. But on each of the evenings the distance of the Comet from at least one star was measured twice; and the change of distance for a known interval being thus found, it was always possible to reduce to the same moment the measures of distance from two stars.

5. With the R. A. and N.P.D. of the two stars, the distance between them was soon found, and the angle made by that distance with the meridian of one star. The three sides of the

*See p. 26, 27.—ED.

19, 20

20, 21

advantage has been found to be, that the old transit clock, as now locked up in a closet and used only to regulate the observing clock, remains in a more equable temperature.

Major A. Strange, late Astronomical Assistant in the Great Trigonometrical Survey of India, has sent to the Society three papers:

"On Testing the Vertical Axes of Altazimuth Instruments."

"On a Direct Method of Testing and Adjusting the Equipoise of Altazimuth Instruments."

"On a proposed Isolated Flange for Conical Axes." It would be useless to attempt giving an abstract of these elaborate papers, relating, as they do, to instrumental details, and requiring the illustration of a series of figures.

Information has been received of the death of M. Daussy, Member of the Bureau des Longitudes at Paris, and an Associate of the Society.

On a New Observing Clock.

By Prof. C. Piazzi Smyth, Astronomer Royal for Scotland. (Abstract.)

The desideratum of obtaining a clock with an easily audible seconds' tick has been realised by Mr. R. L. Jones' patent method, to which Prof. Smyth was introduced by letters from Sir T. Maclear and Mr. Hartnup; and Mr. Jones himself procured a second-hand cast-iron barrel clock without striking parts, and having introduced into it his magnetic pendulum brought to the Edinburgh Observatory in April last, and erected it in front of the transit instrument and in electric connexion with the old transit clock, removed for this purpose out of its former position and into the central hall of the Observatory.

The new observing clock goes as accurately as, because simultaneously with, the old transit or regulating clock, but with a vigour or mechanical power more than three hundred times greater, its driving weight being 180 lbs., descending 10 feet in one day, instead of 5 lbs., descending 3 feet in 7 days. The seconds' tick, though loud, was at first a peculiarly slumberous, heavy, and mournful sound, but this was remedied, as suggested by Mr. F. Ritchie, clockmaker in Edinburgh, by obtaining the seconds beat, not in the usual and almost invariable method by the escapement, but, by introducing for the purpose a tilt hammer striking on an anvil, the escapement being rendered noiseless, so as not to interfere with the note of the hammer. The most appropriate quality of sound was found to be produced by a steel hammer striking on an anvil of hard olive wood, hollowed out below, so as to be under one quarter of an inch thick. It would have been an advantage, as regards loudness, to have the hammer and anvil outside the case of the clock in the free open air of the room: this was not actually done, but the casing was taken in the form of a wooden tubing to them, and almost as loud a beat was obtained. The cost of the production of the electricity is trifling, and, as regards the first cost of the apparatus, Mr. Ritchie, having been recently applied to on the part of a Canadian Observatory, has estimated the cost of a big observing clock, with its hammer, anvil, and galvanic battery, at one-third to one-fourth part of the expense of a first-rate

RECENT PUBLICATIONS.

Astronomical Observations made at the Sydney Observatory in the year 1859. By W. Scott, M.A., Astronomer for New South Wales. Sydney, 1860. 8vo. pp. i. to xxiv. and

I to I12.

In the Monthly Notices, vol. xix. p. 293, are printed some extracts from the first Annual Report to the Observatory Board, 22d Dec. 1858, giving an account of the establishment and the position of the Observatory. The Transit Circle arrived from England about the end of December 1858; but the regular observations were not commenced until June 1859. It appears by the observations published in the Monthly Notices, vol. xx. p. 77, that the latitude and longitude of the Observatory were provisionally found to be Lat. 33° 51'41"1 S.; Long. 10h 4 595-86 W. The corrected values, as given by the Observations of Zenith Distances of Nautical Almanac Stars and the Observations of Moon-culminating Stars during the year 1859, are found to be Lat. 33° 51′ 40′′-8 N.; Long. 10h 4 595-96 W.

m

The greater part of the volume is occupied with Transit and Zenith-distance Observations of Stars; and from these are deduced the mean right ascensions and north polar distances for 1st January, 1859. It is from the internal evidence afforded by these that an estimate can be formed of the amount of reliance to be placed on the results which may hereafter proceed from the Observatory.

The causes of error are in a great measure of a temporary nature; such, for instance, as the changes in the piers of the instrument, owing to the contraction of the sandstone; but the results indicate also a permanent instrumental error, such as an irregularity in the form of the pivots. The errors of observation are not greater than those which occur in observatories of a high class, as those at Oxford and Cambridge, and are such as to disappear to a great extent when the mean of four or five observations is taken; but the instrumental errors are such that, although the circle may be regarded for some purposes as