CHAPTER XIII.
VISITORS FROM THE SKY.
ETEORITES have quite a peculiar claim on the attention of the astronomer. No doubt the spectroscope provides him with the means of demonstrating inferentially the existence of iron, and of many other terrestrial elements both in the sun and in many of the stars. But he is actually able to handle something which has come from the outside to the earth when he is in possession of a meteorite. Then, too, the movements of meteorites have a certain significance both for the astronomer and the mathematician. It is true that only the last stage of its wild career can be observed, for the flight of the meteorite for millions of preceding years is quite unknown, so far as any direct observations are concerned. The observer never beholds one of these bodies until that supreme moment when at the conclusion of its incalculable journey it flashes from the sky and strikes the earth beneath. The history of these objects before they are plunged into our atmosphere can only be ascertained by conjecture. I do not mean to say that we have no definite information by which to guide such conjectures. The laws of
