Page:Popular Science Monthly Volume 29.djvu/757

Rh 5. A cloudy train is sometimes left along the track, both of the stone-meteor and of the shooting-star.

6. They have like varieties of colors, though in the small meteors they are naturally less intense and are not so variously combined as in the large ones.

In short, if bodies that produce the various kinds of fire-balls had just the differences in size and material which we find in meteorites, all the difference in appearances would be explained, while, on the other hand, a part of the likenesses that characterize the flights points to something common in the astronomical relations of the bodies that produce them. This likeness of the several grades of luminous meteors has not been admitted by all scientific men. Especially was it not accepted by your late president, Professor J. Lawrence Smith, who by his studies added so much to our knowledge of the meteorites. The only objection, however, so far as I know, that has been urged against the relationship of the meteorites and the star-shower meteors, and the only objection which I have been able to conceive of that has apparent force, is the fact that no meteorites have been secured that are known to have come from the star-showers. This objection is plausible, and has been urged both by mineralogists and astronomers as a perfect reply to the argument for a common nature to all the meteors. But what is its real strength? There have been in the last one hundred years five or six star-showers of considerable intensity. The objection assumes that, if the bodies then seen were like other meteors, we should have reason to expect that among so many hundreds of millions of individual flights a large number of stones would have come to the ground and have been picked up.

Let us see how many such stones we ought to expect. A reasonable estimate of the total number of meteors in all of these five or six showers combined makes it about equal to the number of ordinary meteors which come into the air in six or eight months. Inasmuch as we can only guess at the numbers seen in some of the showers, let us suppose that the total number for all the star-showers was equal to one year's supply of ordinary meteors. Now, the average annual number of stone-meteors of known date from which we have secured specimens has during this hundred years been about two and a half.

Let us assume, then, that the luminous meteors are all of like origin and astronomical nature; and further assume that the proportion of large ones, and of those fitted to come entirely through the air without destruction, is the same among the star-shower meteors as among the other meteors. With these two assumptions, a hundred years of experience would then lead us to expect two or perhaps three stone-falls from which we secure specimens during all the half-dozen star-showers put together. To ask for more than two or three is to demand of star-shower meteors more than other meteors give us. The failure to get these two or three may have resulted from chance, or from some