Page:Popular Science Monthly Volume 29.djvu/389

From Wikisource
Jump to: navigation, search
This page has been proofread, but needs to be validated.
375
THE ORIGIN AND STRUCTURE OF METEORITES.

Some of the more remarkable falls were objects of extraordinary attention among the inquisitive but imperfectly informed ancients, and the stones themselves were invested with something like divine honors. But, notwithstanding the frequent and authentic testimonials that were given of the fall of meteoric bodies upon the earth in the course of more than twenty centuries, educated people were still incredulous on the subject not more than a hundred years ago. Inversely to the usual course, even the advance of knowledge furnished objections against the truth. The most natural supposition of an extra-terrestrial origin of the meteors appeared to contradict the immutable laws of the movements of the heavenly bodies; for those laws seemed to be inconsistent with the possibility of irregular phenomena. It was easier to deny the reality of such anomalies than to believe in them. But it will not be right to give too severe a condemnation to this persistent denial; for the fabulous and fanciful details with which the accounts of the phenomena were charged necessarily gave an air of incredibility to the whole. It was not till the end of the last century that conditions especially favorable to exact observations afforded the means of unanswerably demonstrating the existence of meteors. The recognition of them became general and complete after the showers that occurred at Benares, India, at eight o'clock in the evening of the 13th of December, 1798, in the presence of a large number of spectators; and was further strengthened after the fall at L'Aigle, France, at one o'clock in the afternoon of the 26th of April, 1803. Biot, acting under a commission of the Academy of Sciences, made a minute account of all the circumstances of the last fall.

Meteorites interest us not only in respect to the origin and the causes of their descent upon our planet, but also in respect to their constitution. It is to the last aspect that we shall pay particular attention, after giving a succinct account of the circumstances under which they come to us.

The phenomena that precede and accompany falls of meteorites, while they vary very much in their secondary details, nevertheless present a whole of general character, reoccurring with constancy at each apparition, and adequately proving that the origin of the bodies is foreign to our planet.

The first appearance is that of a globe of fire bright enough to set all the atmosphere aglow at night, or to be visible at high noon, if in the daytime. Its apparent diameter increases as it gets nearer. It describes a track whose incandescence makes it perceptible from a distance, and which is only slightly inclined to the horizon. The cosmic character of the bodies is indicated by their excessive velocity, which surpasses anything that we know of on the earth, and is in reality comparable to that of the planetary bodies. After a longer or shorter career, the body bursts with a noise which has been compared with that of thunder, a cannon, or musketry, according to the distance away