Iron is found in all these bodies, and in a considerable quantity, with the rare metal nickel. It is a singular fact, that though a chemical examination of their composition has not discovered any substance with which we were not previously acquainted, yet no other bodies have yet been found, native to the earth, which contain the same ingredients combined. Neither products of the volcanoes, whether extinct or in action, nor the stratified or unstratified rocks, have exhibited a sample of that combination of metallic and earthy substances which the meteoric stones present. During the era that science has admitted their path to the earth as a physical truth, scarcely amounting to half a century, few years have elapsed without a known instance of descent occurring in some region of the globe. To Izarn's list, previously given, upward of seventy cases might be added, which have transpired during the last forty years. A report relating to one of the most recent, which fell in a valley near the Cape of Good Hope, with the affidavits of the witnesses, was communicated to the Royal Society, by Sir John Herschel, in March, 1840. Previously to the descent of the aërolites, the usual sound of explosion was heard, and some of the fragments falling upon grass, caused it instantly to smoke, and were too hot to admit of being touched. When, however, we consider the wide range of the ocean, and the vast unoccupied regions of the globe, its mountains, deserts, and forests, we can hardly fail to admit that the observed cases of descent must form but a small proportion of the actual number; and obviously in countries upon which the human race are thickly planted many may escape notice through descending in the night, and will lie imbedded in the soil till some accidental circumstance exposes their existence. Some, too, are no doubt completely fused and dissipated in the atmosphere, while others move by us horizontally, as brilliant lights, and pass into the depths of space. The volume of some of these passing bodies is very great. One which traveled within twenty-five miles of the surface, and cast down a fragment, was suppose to weigh upward of half a million of tons. But for its great velocity, the whole mass would have been precipitated to the earth. Two aërolites fell at Braunau, in Bohemia, July 14, 1847.