The setting of the Moon is given from new moon to full, and the rising from full moon to new; the letters M. A. m. a., to be found in these columns and in other parts of the Almanac, are used to denote Morning and Afternoon.

The time of the Phases of the Moon is computed for the meridian of Washington, 5h. 7 42", but may be readily reduced to that for any other meridian, by adding or subtracting the difference of the longitude, according as the same is east or west of that city. The time of the moon's southing is computed for the same meridian. The variation, however, even in a remote part of the United States, will be inconsiderable.

The time of High Water is corrected for the difference of the Right Ascension of the Sun and Moon, and the distance of the moon from the Earth. The small corrections depending on their declinations and our distance from the Sun, have been neglected as unimportant; indeed it has been ascertained, from a series of several hundred observations, that the corrections we have introduced will, in calm weather, give the time of high water within fifteen minutes, and, generally, much nearer. The difference between the time of high water at New York, Charleston, and Boston, was derived from the best authorities; but perhaps it has not been ascertained with the degree of accuracy that is to be desired. If our authorities are correct, the ime of high water along the coast of Maine, New Hampshire, and Massachusetts, as far as Nantucket, is nearly the same as at Boston. Moreover, when it is high water in New York, it is nearly so in Long Island Sound, along the coast of New Jersey, Delaware, Maryland, Virginia, and North Carolina, as far as Cape Lookout, (with the exception of Sandy Hook and the entrance of Chesapeake Bay ;) whilst along the coast of the southern part of North Carolina, of South Carolina, Georgia, and Florida, at Sandy Hook and the entrance of the Chesapeake, the time agrees very nearly with that in the column for Charleston; when greater accuracy is desired, reference should be had to the Tide Table on the 30th page. The time of the tide immediately preceding the southing of the moon, only, having been given, it should be corrected by the addition of half the difference when the time of the other tide is required.

The Planets are placed in the order in which they pass the meridian on the first day of each month, and their declinations are computed for the moment of their passage over the meridian of Washington.

The equation of time is the correction by which apparent is reduced to mean time. It is computed for apparent noon at Berlin, and should be applied according to the direction at the head of the column; but when mean is to be reduced to apparent time, the sign of the equation should be reversed.

Mean time has been generally used in this Almanac; the exceptions being the beginning and end of twilight, the rising and setting of the sun (which could not be expressed in mean time, without occupying too much room), the equation of time and the Sun's Declination.

The Ephemeris of the Sun is taken from the celebrated Almanac of Professor Encke. For the Sun's Right Ascension, in the American Almanac for 1831, the Sidereal time has been substituted; which will be found more convenient for the determination of the time of a star's transit, or of the Right Ascension of the Meridian; its epoch is noon, mean time at Berlin, whilst that of the Sun's Declination and of the Equation of time is noon, apparent time, of the same meridian.

The apparent places of twenty-four stars, as determined by Professor Bessel at Königsberg, will be of great use in ascertaining the time or the latitude. The Declination of some of them will, on comparison with their places in the English Nautical Almanac, be found to differ therefrom more

than was to be expected in the present improved state of astronomical instruments. This difference sometimes amounts to four seconds, and can hardly be altogether ascribed to the use of different tables of refraction.

The Table of Refractions is that computed on principles explained by the late Dr. Thomas Young, and is recommended by its great simplicity; moreover, it is said to agree as closely as any other, with the latest observations: nevertheless had not Professor Bessel's new table required a table of logarithms in its use, it would have been preferred, as indeed would any thing recommended by this eminent astronomer.

In the year 1833 there will not be any very important astronomical phenomena in the United States. The Sun will not be eclipsed, and there will not be any occultation of a planet or of a star of the first or second magnitude.

A communication of any observations of the solar eclipse of last February, of the eclipses in 1832, or of any occultations, together with the correct latitude, will be very acceptable; and the longitude of the place of observation will thence be deduced.

R. T. PAINE.

Boston, October 19, 1831.

Comparative Scales of Thermometers 88 3. First Meridians of Longitude

210-242

170-174

214-217