Page:The Music of the Spheres.djvu/260

 tionate to its charities on earth, and when its allotted period is over, it falls to earth as a meteorite.

If picked up soon after it falls, a meteoric stone is found to be very hot on the outside while the inside is cold. One constant characteristic by which it may be identified is the fused, black, thin and glossy crust, somewhat like varnish, which coats the surface of the meteoric stone. This surface crust is thin and sharply defined from the inner mass.

The predominating element in one class of meteorites is iron, generally combined with a small amount of nickel. Copper, tin, cobalt and other substances are also found, but never silver or gold. Stony meteorites are, however, more common than iron meteorites.

The velocity of meteors, or shooting stars, varies from 12 to 40 miles a second. Herschel estimates their average height above the earth at the time of their appearance as 73 miles, and 52 miles at the time of their disappearance.