of Adams' calculation that he at once wrote to the astronomer in charge of the Royal Observatory, to search that quarter of the heavens, and discovered the planet so anxiously sought for. Leverrier, in September of the same year, wrote to Berlin asking for help in searching for the planet. Dr. Galle upon receiving this request did as he was asked, and immediately discovered the same planet.

Neptune revolves around the Sun at a mean distance of about 2,790,000,000 miles. Its year is equal to about 165 terrestrial years. Its motion is the slowest of any of the planets, it being the most remote from the Sun. The velocity of the planets decreases from Mercury, which revolves at the rate of about 105,000 miles per hour, to Neptune, which revolves at the rate of about 12,000 miles only.

Its diameter is about 37,000 miles. Nothing is known concerning its

seasons.

Measuring the Distance of the Stars.-The distance of the stars is calculated by ascertaining the angle formed by the rays of light from any celestial body at the Observatory of Greenwich, England, and at the Cape of Good Hope, Africa. The distance between these two points is known, and forms the base of a triangle. Tables are published, containing the Sines for all angles, and the calculation is comparatively simple, consisting in figuring out the perpendicular and hypothenuse of the triangle thus formed.

AEROLITES, SHOOTING STARS AND METEORS.

There are a great number of Shooting Stars and Meteors as well as Aerolites. These different names have been given them, although the distinction is not very definite.

Aerolites are the stony or iron masses which fall on the earth.

Meteors are spherical in form and have an appreciable diameter. They pass over a great extent of country, are visible for some seconds, and many leave behind them a trail of glowing sparks. Others explode with a noise like that of artillery; the pieces either continuing, or falling upon

the earth.

Shooting stars are bright transient spots, which dart suddenly through the air, leaving a fiery train behind.

At Yale College there is a mass of meteoric iron weighing 1635 lbs. The Chinese record the falling of an aerolite in the year 616 B. C., that broke several chariots and killed ten men. A block of stone, equal to a full wagon load, fell into the Hellespont, 465 B. C. A mass once fell in South America that was estimated to weigh fifteen tons. When first seen

it was so hot that no one could approach it; when cool, it was so hard that no tool could break it. There have been frequently showers of falling stars that appeared like celestial fire-works.

Prof. Newton estimates that the number of meteors that traverse the atmosphere daily, and which are large enough to be seen at night, is 7,500,000; if to these is added those which can be seen through a telescope the number would be increased to 400,000,000. Any clear night, from five to seven shooting stars may be seen, but they are more abundant in April, August, October and November, and they are produced by small bodies revolving like our earth about the sun; their paths cross the earth's and consequently collide. They are so small no shock results

COMETS.

These are the most fascinating of the heavenly bodies. They appear suddenly, have enormous fiery trains, and pass so swiftly, they seem mys

terious; many

people have a superstitious dread of them. The term signifies a hairy body. It consists generally of three parts: I. the nucleus, a bright point in the middle of the head; II. the coma (hair), the cloud-like mass surrounding the nucleus; and III. the tail, extending in a direction from the sun; while others have no nucleus. Kep

ler says "there

are as many comets in the heavens as there are fish in the sea." Some comets return, others never do. For instance the comet of 1844 will return A. D. 101,844.

There is good reason to believe that the earth passed through the tail of a comet in 1861. Little fear need be entertained of any trouble due from the earth running against one of them. The great comet of 1811 had a beard 112,000 miles in diameter; the nucleus was 400 miles, and the tail 112,000,000 miles long; it will return 3000 years hence.

Zodiacal Light.-In March and April, just after sunset, there is a faint nebulous light of a conical shape flashing upward as high as the Pleiades. In September and October, at dawn, the same light can be seen in the eastern horizon. It is sometimes confounded with the Milky Way or Aurora. It is red at the base, and is perpetual in the tropics. This is the Zodiacal light, and is supposed to be a nebulous ring, surrounding the earth inside the moon, like those of Saturn.

THE STARS.

The Solar system extends 2,800,000,000 miles into space, and yet were we on Neptune, the stars would seem just as far away. We never see the stars in fact; we only see the light they emit, precisely as we see the rays

from a light-house, but do not see the lantern. The most powerful telescope fails to reveal the faintest trace of a disk. At the present time the nearest star to the earth is Alpha, in the Constellation of Centaur. It is estimated to be over 20,000,000,000,000 miles distant; this means that it is not inside this distance, but how much farther away it may be is unknown. It takes the light from it 31⁄2 years to reach us.

The fixed stars, so called, are flying through space at an amazing rate; for instance, Arcturus, with a speed of 200,000 miles per hour, requires 3 centuries to traverse as much of the starry vault as equals the moon's

CONSTELLATION OF THE GREAT BEAR.

apparent diameter. This will give some idea of heavenly distances. The fact that stars shine by their own light proves that they are suns like our own, which is quite a small star, sweeping the heavens at the rate of 150,000,000 miles per year.

Number.-The stars seem to us innumerable, but in fact the entire number visible is but 6000, while but few people can discern more than 4000.

Magnitude. The classification of the stars is made from their comparative brilliance, as nothing is known of their size. They are arranged in 20 classes or magnitudes. There are about 20 stars of the first magnitude, 65 of the second, 200 of the third, 1100 of the fifth, 3200 of the sixth, 13,000 of the seventh, 40,000 of the eighth, and 142,000 of the ninth. But

few persons can see stars of less magnitude than the fifth or sixth. The relative brightness may be due to size, distance, or intrinsic brightness. Many of the stars were named at an early date, as Sirius and Arcturus. The chief stars of each constellation are called after the letters of the Greek alphabet, according to their relative brightness.

Constellations.-- From the earliest times the stars have been arranged in groups, to more readily study them, and took on fanciful names from their fancied resemblance to natural objects, mythology being largely drawn upon for this purpose.

The best known constellation is the Great Bear or Dipper. The next

Ursa Minor, or Little Bear, or Little Dipper, containing the North Star. The Bible refers to Orion and the Pleiades.

The signs of the Zodiac are 12 constellations, arranged as follows: Aries, the ram, so named because it rose with the sun in the spring. Then came Taurus, the bull, and Gemini, the Twins. At the summer solstice the sun appeared to stop, and crab-like go backward, hence Can cer, the Crab. When Leo, the Lion, appears, the streamlets are dry. Virgo comes next, when the virgin gleans the summer harvest. When the days and nights are equal, at the Autumnal Equinox, Libra, the balance, reigns. When the summer days are gone, the Scorpion arrives in the heavens. When the hunters are abroad, Sagittarius, the archer, bends his bow in the sky. At the winter solstice, December 21st, Capricornus, the goat, climbs the heavenly arch, and finds the sun ascending the sky on his return north. The rainy season, January, has Aquarius, the Water-bearer. Pisces, the fishes, complete the round of the months.

Although all the stars look like a single luminary, the telescope says that 10,000 of them are double; i. e., the ray of light is the blended emanation of two suns. The North Star consists of two stars 18° away from The Dog Star (Sirius) has two 7 distant from the other. Colored Stars.-The stars are different colors. Sirius is white, some are red, while others are yellow, blue, and green.

each other.

The Variable Stars have periodical changes of brilliancy, variously explained. Some stars suddenly appear with great brilliance, others gradually fade away, giving rise to what are called New Stars and Lost Stars.

The Nebula are faint misty appearances like an illuminated cloud. A few can be seen with the naked eye, but the telescope makes thousands visible. It is believed that these are the beginnings of stars, or sun germs. They are variously shaped, ring-like, spiral, oval, etc. One looks like a dumb-bell, another like the wings of a bird, and yet another has the appearance of a crab.

Astronomical study is now occupied in determining the constitution of the stars, and by the Spectrum Analysis much is being determined that seems incredible. The rays of light are passed through a prism, and by refraction compared with those made by metals that are heated to incandescence.

Time. The time of day is measured by the interval required by the earth to rotate on its axis, the time certain stars rise, as well as the sun, the latter varying more than the former, it being necessary to add one day every four years to even things up.

Parallax is the difference in direction of an object seen from two different places; for instance, place your finger before you in front of a window, look at it with the left eye only and it will seem to be at one point on the window. Look at it now with the right eye only and it will be located apparently somewhere else on the window. The difference in the position of your finger as seen from your two eyes separately is its parallax. Aberration of Light is the apparent change of position of heavenly bodies due to the refraction of light.