Page:Popular Science Monthly Volume 16.djvu/269

Rh actual path pursued by a meteor may be on one side of the heavenly sphere, while the radiant is on the other; precisely as any particular yard of a set of parallel railway lines and telegraph wires may be to the right or the left, or above or below, or may be behind an observer, while the point from which all these lines converge is in front of him. Yet two meteor-tracks, carefully observed, will suffice, unless absolutely coincident, to show the radiant point belonging to them, assuming of course that they belong to the same system. And when on any night many meteors of the same system are seen, the radiant point of the system, which indicates the direction from which with respect to the earth they all seem to travel, can be most accurately determined. In this way each meteor system is perfectly distinguishable from all others; and also, from the position of the radiant point of a system, the question whether the meteors are or are not bodies following in the track of any known comet, can be at once set at rest. The path of such bodies can be calculated with perfect exactness. The apparent path resulting from the combination of their motions with the motions of the earth can equally well be determined. This gives the radiant point of such bodies, if such bodies there are, as they appear in shooting-star displays in our skies. No scattered meteors, still less any meteor-shower, can be mistaken for attendants on such a comet—at least, if we set aside the bare possibility (for such it is) that bodies really traveling in a different course may appear to travel on the same course. This can happen; but it is so exceedingly unlikely, that if a meteor-flight appears at the time, and from the radiant point, corresponding to the attendants of a particular comet, it may be confidently assumed that they really are such attendants.

But, as I have said, on former occasions when displays of meteors occurred during the last week in November or the first week of December, which might therefore have indicated the earth's passage through the train of Biela's comet, no special observation was made of the tracks of individual meteors, so that it was not possible to ascertain afterward whether such showers might or might not be thus explained. Nor were any observations made for Biela meteors when the earth passed through the track of the comet in 1836, when, from what we now know, a display of such bodies might have been expected.

It was otherwise in 1873, Biela's comet itself having been searched for fruitlessly, several astronomers called attention to the circumstance that in the last week of November the earth might be expected to pass through a train of meteors following in the track of the now disintegrated comet. They showed also how Biela meteors, if such existed, could be distinguished from other shooting stars; the radiant point corresponding to attendants on Biela's comet lying in the region where the constellation Andromeda borders on Cassiopeia, near the feet of the former of these celestial bodies. I myself wrote in the following terms, in a paper written in October, and which appeared in the "St.