Page:Field Book of Stars.djvu/153

Rh. There is always a pleasure in being able to recognize at a glance a certain definite manifestation of nature, be it a rare flower or a flashing meteor.

The generally accepted theory respecting the meteors is that they were all originally parts of comets now disintegrated, and the four well-known showers of April 20th, August 10th and 14th, and November 27th, bear testimony to this theory.

The apparent velocity of the meteors is between ten and forty-five miles a second, and their average height is about seventy-six miles at first appearance, and fifty-one miles at disappearance. Occasionally a meteor is so large and compact as to escape total destruction, and falls to the earth. Specimens of these meteorites are to be found in our best museums.

I have seen fit to divide the principal meteor showers into four groups, according to the seasons in which they appear, and have placed them respectively at the conclusion of each season's work on the constellations.

By radiant point is meant the point from which the meteors start on their flight. This point is an apparent one, however, due to an illusion of perspective, for the meteors really approach the earth in parallel paths.

The dates given for these showers are those of the maxima, and the meteors should be looked for several nights before and after the dates specified.

The showers that are to be seen after midnight are, unless of special note, omitted.