Me′teors are small bodies traveling in large numbers and in many directions through space. They are known as aërolites, fireballs and shooting stars, and may be seen every clear night, sometimes few only, but at other times in showers. The whole number which the earth meets in one day’s travel is estimated at 7,500,000, but as this large number weighs in all only 100 tons, many of the meteors must be very small. The air acts as a shield, and offers so much frictional resistance that the meteor generally burns. The aërolites are the large masses which actually fall to the earth. Some of them are of iron, some of stone, some of stone and iron. When their fall is noted, there always are a noise, as of an explosion, and a cloud or smoke and a melting of the mass, at least on the surface, showing the action of heat. The iron is combined with nickel, cobalt, copper etc. in a way different from any combination found on the earth, though no new element has been discovered. The falls of aërolites have been more numerous than might be supposed, the British Museum having over 300 specimens of them. The fireballs are brightly-shining bodies seen crossing the sky, and are considered to be aërolites before their explosion and fall. Many hundreds have been observed, Arago giving a list of over 800. They are of all sizes, and travel about 26 miles a second. Shooting-stars may be seen on almost any evening, and if carefully watched will seem to come from the same point in the sky. These points are called radiants, and are named for the constellation in which they are found — as the Leonids, a group whose radiant is in the constellation Leo. When there is a meteoric shower, the earth is passing through a group or swarm of these meteors, which are also moving, as the earth does, each in an orbit of its own. The Leonids, which are seen in November, are calculated to move round the sun once in 33¼ years, the earth crossing their track every year, but only meeting the main swarm when this reaches the point of crossing at the same time as the earth. When this happens, there is a meteoric shower, such as took place on Nov. 13, 1833, when the stars fell like snowflakes and fireballs darted back and forth, making the most wonderful display of the kind ever seen. Astronomers predicted another shower in 1866, and it came within a few hours of the time agreed upon. The latest investigations point to a common origin for these meteors and the comets, or rather indicate that meteoric swarms are composed of disintegrated comets. Besides the great November group, other groups are active in August, April, September and October. See Young’s General Astronomy.