Page:Astronomy for Everybody.djvu/304

years. The earliest account is the following from an Arabian writer:

In the year 599, on the last day of Moharren, stars shot hither and thither, and flew against each other like a swarm of locusts; people were thrown into consternation and made supplication to the Most High; there was never the like seen except on the coming of the messenger of God; on whom be benediction and peace.

The first well-described shower of this class occurred on November 12, 1799. It was seen by Humboldt, then on the Andes. He seems to have considered it as a very remarkable display, but made no exact investigation as to its cause.

The next recurrence was in 1833, which seems to have been the most remarkable one ever observed. The astronomer Olbers suggested from this that the shower had a period of thirty-four years, and predicted a possible return in 1867, which actually appeared in 1866. In 1866 and 1867 the observations were more carefully made than ever before, and led to the remarkable astronomical discovery, just alluded to, that of the relation between meteors and comets. To explain this we must define the radiant point of meteors.

It is found that if, during a meteoric shower, we mark the course of each meteor by a line on the celestial sphere, and continue these lines backward, we shall find them all to meet at a certain point in the heavens. In the case of the November meteors this point is in the constellation Leo; in the August meteors it is in Perseus. It is called the radiant point of the shower. The lines in which the