The number of asteroids discovered up to present date is about 450. A number of these small planets have not been observed since their discovery, and are practically lost. Consequently it is now sometimes a matter of doubt, until the elements have been computed, whether the supposed new planet is really new, or only an old one rediscovered.

The Moon.

THE mean distance of the Moon from the Earth is 238, 850 miles; its mean sidereal revolution round the Earth is 27 days, 7 hours, 43 minutes, 11. 46 seconds; its mean synodical revolution, or the period from new moon to new moon, is 29 days, 12 hours, 44 minutes, 2.87 seconds; the eccentricity of its orbit is 0.0549, and its diameter 2,162 miles. The Earth being taken as unity, the density is. 61; mass, 1-81; volume, 1-50, and gravity, 1-6; that is to say, the Earth would weigh as much as 81 Moons, is 50 times larger, and a pound of matter at the Moon's surface would, if transferred to the Earth, weigh 6 pounds.

The weight of a cubic foot of distilled water at a temperature of 60° F. is 1,000 ounces Avoirdupois, very nearly, therefore the weight (in ounces, Avoirdupois) of a cubic foot of any of the substances in the above table is found by multiplying the specific gravities by 10, thus:-one cubic foot of oak weighs 1,170 ounces; one cubic foot of marble 2,700 ounces, and so on. * Compared with water.

Freezing, Fusing, and Boiling Points.

Two heavenly bodies are in conjunction' (6) when they have the same Right Ascension, or are on the same meridian, i. e., when one is due north or south of the other; if the bodies are near each other as seen from the earth, they will rise and set at the same time; they are in opposition'' (8) when in opposite quarters of the heavens, or when one rises just as the other is setting. "Quadrature" is half way between conjunction and opposition. By "greatest elongation' is meant the greatest apparent angular distance from the sun; the planet is then generally most favorably situated for observation. Mercury can only be seen with the naked eye at this time. When a planet is in its ascending" (Q) or descending" (8) node it is crossing the plane of the earth's orbit. The term "Perihelion means nearest, and "Aphelion' farthest, from the sun. An occultation" of a planet or star is an eclipse of it by some other body, usually the moon.

1. ECLIPSES.

There will be five Eclipses in the year 1902; three of the Sun and two of the Moon.

1. A partial Eclipse of the Sun April 8, invisible in the United States, visible in the Arctic Ocean. A total Eclipse of the Moon April 22, invisible in America.

2.

3.

A partial Eclipse of the Sun May 7, invisible in America, visible in New Zealand and the South Pacific Ocean. 4. A total Eclipse of the Moon October 16-17, visible in the United States as follows:

The point of the Moon's limb which first comes in contact with the Earth's shadow is 860 from the north point of the Moon's limb toward the east, and the last contact 1180 from the north point toward the west.

Magnitude of the Eclipse-1.46, the Moon's diameter being considered unity.

5. A partial eclipse of the Sun October 31, invisible in America, visible in Europe and Asia. Magnitude of greatest Eclipse is 0.696, the Sun's diameter being 1.

a Virginis (Spica) will be occulted by the moon on February 26, 3 h. 26 m. A. M., and on May 20, 1 h. 48 m. A. M. (Washington Mean Time). The duration of the first is 1 h. 12.4 m., and of the second, 47.4 m., as seen from Washington, D. C.

The planetary configurations serve to identify the planets and to mark the time when they are in critical points of their apparent orbits as seen from the centre of the earth, the general station from which all astronomical phenomena are supposed to be viewed, unless the contrary is distinctly stated. The conjunctions of the moon with the planets when viewed from the earth's surface may differ from the above dates as much as 20 minutes or even more by reason of the moon's parallax in right ascension. For the mere purpose of observation the above dates are sufficiently accurate for all places.

The Harvest Moon.

EVERY person who observes the ordinary astronomical phenomena of everyday occurrence will no doubt have noticed that there is a great variation in the time of the moon's rising and setting. This is due to several causes, viz., the direction of the moon's apparent path with reference to the horizon of the place, her distance from the earth, and her daily motion eastward in right ascension. During every lunar month the moon rises or sets only twenty-three or twenty-four minutes later for three or four successive evenings, while during the remainder of the mouth the retardation in the time of rising or setting may vary from twenty-four to seventy-eight minutes in this latitude. When full moon occurs at or near the autumnal equinox, and if at the same time the moon is in her ascending node, that is, passing from the south to the north side of the ecliptic or sun's apparent path, she will rise at almost the same hour on several successive evenings and at a point of the horizon opposite to that of the sun. This phenomenon is more noticeable in high northern latitudes as in the middle and north of Europe. The duration of moonlight on such occasions is the greatest possible, and as the harvest occurs in those latitudes at that season of the year the excess of moonlight is a great assistance to the farmer, and hence the name "harvest moon." In order to understand the action of the causes which produce this phenomenon it will be necessary to bear in mind that at the time of the autumnal equinox, September 21. the sun sets exactly in the west and the southern half of the ecliptic or the sun's apparent annual path in the sky will then be wholly above the horizon and the northern half entirely below and the ecliptic will make the least possible angle with the horizon.

If at the same time the moon is at or near the full and in the ascending node, her apparent path will make a still smaller angle with the horizon by about 50 8', and as she advances in her orbit about 130 every day this arc or portion of her orbit will evidently be less depressed below the horizon than at any other time, and as her motion is also northward as well as eastward she will not only rise at almost the same hour on several successive evenings, but also at points of the horizon farther and farther north of the east point. In high northern latitudes, as in Alaska, British Columbia, the north of Scotland, and Sweden and Norway, the moon's path at such times is almost parallel with the horizon and she rises at nearly the same hour for more than a week

A directly opposite state of things takes place when the full moon occurs at or near the time of the vernal equinox; the moon's path is then nearly perpendicular to the horizon and she rises later and later every evening by about seventy-eight minutes. There is then the least possible amount of moonlight.