nageable as reflecting telescopes, and perform as much as those which he makes of 10 feet, with two object glasses." The marking the word common in this manner, sufficiently implies that the telescopes in question are now become uncommon.

7. P. xxv. "For the mean obliquity of the ecliptic, the Preface of the Nautical Almanac certainly renders the Astronomer Royal responsible. The equations are computed from Delambre's tables."

8. P. xxvi." Ephemeris, by Schumacher. A regular supply should have been sent over to this country in the first instance." It not only was so sent, but was advertised for sale by the bookseller to the Board of Longitude, long before the appearance of Mr. Baily's astronomical tables and remarks, which it is presumed he will think it still less necessary continue in any future year," than before the present attempt was made to shew their superfluity and frivolity, as far at least as regards the errors and omissions attributed to the Nautical Almanac.

Additional note, from Schumacher's Journal.

66

to

Professor Schumacher, in the 6th Number of his Astronomical Newspaper, gives a favourable opinion of the general utility of Mr. Baily's tables, which have been communicated to him by the author; but with respect to the Nautical Almanac he observes, (p. 94,)" I understand that the Board of Longitude has within a few years reduced the price of the annual volumes as much as possible, in order that they may the more easily be purchased by seafaring persons, and they would therefore probably not be willing to add to them each year an Astronomical Supplement, which must make the price unavoidably greater. I cannot agree with the author in his comparison of the Nautical Almanac, with the Connaissance des Tems, with Bode's Jahrbuch, with the Ephemerides of Milan, and with those of Vienna, which last have been discontinued from the year 1806; and I should doubt whether occultations are particularly appropriate to the determination of the longitude at sea. The seaman requires to know his longitude without delay, and as near as possible to the place of observation; and even if he should happen to be an able computer, which is not very commonly to be expected, the calculation of a lunar occultation. might take up so much of his time as to be wholly impracticable while the result would be of any value; and the great advantage of corresponding observations of the same occultation at different places is wholly lost to him."

[No doubt it was from considerations of this nature that Dr. Maskelyne and the Board of Longitude were induced to discontinue the insertion of the greater part of the occultations formerly indicated in the Nautical Almanac. It now remains to

be proved whether or no the experiment, which has been made, for the year 1824, will be authorised by any utility that may be found to accrue to the seaman from the elements inserted, when employed in the manner pointed out in the third number of these collections.]

ii. Places of the Small Planets for 1822.

Places of Juno, by Prof. Nicolai, Bode's Jahrb. 1824, p. 244.

Places of Vesta, by Prof. Encke, Bode's Jahrb. 1824,

ART. XVIII. Results of some Astronomical Observations made in Blackman-Street, during the Months of January and February, 1822, by James South, F.R.S., in Latitude 51° 30′ 3′′ N., Longitude 21".8 W.

No tremulous motion of either of these Stars, nor any projection of either upon the D's disk, their disappearance instantaneous.

Diameter of Mercury, taken in the direction of his Cusps.

Diameters of Venus taken in the direction of her Cusps.

Feb. 10, The planet distant from

14,

15, ......
28,

27 days

23 days

22 days

9 days

the mean of

10

10

measures

n

= 46.224

= 49.791 €49.647

=

These measures of Venus, as also those of Mercury, were taken by day-light, and from one to three o'Clock, P. M.

Observations of the Shadows of two of Jupiter's Satellites, seen on the planet's disk in the day-time.

Feb. 14. At 2 1' sidereal time, or about 4" 26' mean time, I saw very distinctly the shadow of one of Jupiter's satellites upon his disk. At 2" 12' a satellite came off his face, and con

tinued visible, notwithstanding its proximity to the planet. Measures of the shadow's distance from the satellite were procured. At 2 22′ 10" I distinguished another satellite emerging from the same spot whence the preceding had passed off. My attention was directed to the place some minutes previously, in consequence of a luminous point which far exceeded in splendour the faint light of the planet. As yet only one shadow had been observed, but at 2" 38' that of the second became visible; distances of the shadows from their respective satellites were obtained; distances of the satellites from each other were gotten, and also distances of the shadows from each other. The angles of position of the satellites, and of their shadows, were also ascertained. The interior contact of the first shadow with the limb of the planet, was observed at 3 20'; and that of the second at 4" 4' sidereal time. The actual disappearance of the one or the other shadow, owing to the then constant passing of light clouds could not be ascertained. At the commencement of the observations the sun was shining, but the sky, although cloudless, was of a very light blue colour, not at all favourable for sidereal observations. Under more advantageous circumstances in the day-time, I have no doubt measures of the diameters of the shadows might be procured without difficulty.

The five feet Equatorial has a telescope of five feet focal length, and a double object glass of 33 inches aperture. The Gregorian telescope has a speculum of six inches diameter, and thirty inches focus.

The measures of the planet's diameters are taken with a wire micrometer made by Mr. Troughton; its value has been rigorously ascertained, and the uniformity of its screw's thread has most satisfactorily stood the severest examinations.

The declinations of the stars, as also their right ascensions, (here given,) will be found sufficiently accurate to identify them, and are for no other purpose introduced.

Wherever more than one observation of the same phenomenon is given, each may be considered independent of the other; the same clock is used by each observer, but the moment of observation as estimated by each person is noted upon paper before the least mutual communication is allowed; so that any coaxing to make observations tally, is absolutely impossible.

In future communications it is my intention to give all observations in sidereal time, and very much do I wish that other observers would do the same. So would the trouble of converting sidereal to mean time, as also the chance of errors in the reduction be entirely precluded; the considerable incongruities frequently existing between the sun's observed and computed right ascensions would likewise cease to prejudice the observations.

Reference to Plate III.

Observations of the eclipses of Jupiter's satellites are the most unsatisfactory which the practical astronomer is called upon to make; the immersions, however, will afford considerably less incongruity than the emersions; I believe much of this may be attributed to the observer not having his eye well directed to the spot at which the satellite first issues from the shadow, for I have found that since a diagram, of which the annexed is a copy, has been suspended in my observatory, the discordancies have materially diminished. From experience, therefore, I can recommend to others its adoption; the observer will also do well to prefix to the dates of those eclipses which he is likely to witness, the planet's distance from opposition, he will then immediately know which of the diagrams is most applicable to his purpose. The emersion may generally be expected a little to the north or south of the belts.

ART. XIX. Observations on the Chronometrical Arrangements now carried on at the Royal Observatory, under the authority of the Lords Commissioners of the Admiralty, tending to shew their Inadequacy to the purpose for which they were designed. By JAMES SOUTH, F.R.S.

IN offering to the consideration of those who may feel an interest in such matters, the following remarks, I trust, it will be believed that I am actuated by no sinister motive; but conceiving that the acts of public bodies, which have for their object public benefit, when they have had not only notoriety, but even national importance, attached to them, by insertion in the London Gazette, become fair subjects for private as well as public inquiry, I have resolved to investigate how far the advertisement relative to chronometers, which appeared in the London Gazette of June the 26th, 1821, is likely to prove beneficial to the country.

"Admiralty Office, June 25, 1821. "The Lords Commissioners of the Admiralty, being desirous of increasing the number of chronometers for the use of his Majesty's Navy, and of encouraging the improved manufacture of that important article, do hereby give notice, that a depôt for the reception of chronometers is opened at the Royal Observatory of Greenwich, where the makers will be permitted to deposit their chronometers, in order to their being tried, and ultimately purchased for the use of the navy, or of being disposed of by the proprietors to private purchasers.

"And, for further encouragement, their Lordships will purchase, at the end of each year, the chronometer which shall have kept the best time, at the price of 3001., and the second best at the price of 2001., provided that there have been above ten chronometers in the competition, and that the said best chronometers shall keep their rates within certain limits to be bereafter stated. The other chronometers their Lordships may purchase, as they may think proper, at such sums as may be agreed upon with the makers, and their Lordships have reason to expect, that their an