A writer in the Quarterly Review, No. CLXXXIII., taus sums up the result of all the chemical analyses hitherto made: "Wefind the actual number of recognized elements discovered in A. to be nineteen or twenty—that is, about one third of the whole number of elementary substances (or what we are yet forced to regard as such) discovered on the earth. Further, all these A. elements actually exist in the earth, though never similarly combined there. No new substance has hitherto come to us from without; and the most abundant of our terrestrial metals, iron, is that which is largely predominant in A., forming frequently, as in some of the instances just mentioned, upwards of 90 parts in 100 of the mass. Seven other metals—copper, tin, nickel, cobalt, chrome, manganese, and molybdena—enter variously into the composition of these stones. Cobalt and nickel are the most invariably present; but the proportion of all is trilling compared with that of iron. Further, there have been found in different A. six alkalies and earths—namely, soda, potash, magnesia, lime, silica and alumina; and, in addition to these, carbon, sulphur, phosphorus and hydrogen. Finally, oxygen must also be named as a con stituent of many A., entering into the composition of several of the substances just mentioned. As respects the manner Of conjunction of these elements, it is exceedingly various in different A. A few there are, especially examined by Berzelius and Hose, containing olivine, augite, hornblende and other earthy minerals, and closely resembling certain crystalline compounds which we find on the surface of the earth." Besides those solid masses of considerable size, numerous instances are on record of showers of dust over large tracts of land; and it is remarkable that such dust has generally been found to contain small hard angular grains resembling augite. Stories of the fall of gelatinous masses from the sky are ranked by Humboldt among the mythical fables of meteorology. It has been supposed that such fables may have originated in the very rapid growth of gelatinous algae, as Nostoc (q.v.).
Fireballs and Shooting-stars.—From the height apparent diameter, the actual diameter of the largest fire balls is estimated by Humboldt to vary from 500 to 2800 ft.; others allow a diameter of about a mile. Shooting-stars are much smaller, their weight varying from 30 grains to 7 lbs. In most cases of luminous meteors, a train of light many miles in length is left behind. One or two instances are on record where the train of the fireball continued shining for an hour after the body disappeared. The heights of shooting-stars are found to range from 15 to 150 m. at the points at which they begin and cease to be visible. Their rdocitks vary from 18 to 36 m. in a second. When it is remembered that the velocity-of Mercury in its orbit is 20.4 m. in a second, of Venus 19.2, and of the earth 16.4, we have in this fact a strong confirmation of the planetary nature of meteorites.
One of the most remarkable facts connected with shooting-stars is, that certain appearances of them are periodic. On most occasions they are sporadk—that is, they
appear singly, and traverse the sky in all directions. At other times they appear in swarms of thousands, moving parallel; and these swarms are periodic, or recur on the same days of the year. Attention was first directed to this fact on occasion of the prodigious swarm which appeared in N. America between the 12th and 13th of Nov., 1833, described by prof. Olmsted, of New Haven. The stars fell on this occasion like flakes of snow, to the number, as was estimated, of 240,000, in the space of nine hours, and varying in size from a point or phosphorescent line to globes of the moon's diameter. The most important observation made was that they all appeared to proceed from the same quarter of the heavens—the vicinity, namely, of the star y, in the constellation Leo; and although that star had changed greatly its height and azimuth during the time that the phenomenon lasted, they continued to issue from the same point. It was afterwards computed by Encke that this point was the very direction in which the earth was mov ing in her orbit at the time. Attention being directed to recorded appearances of the same kind, it was observed with surprise that several of the most remarkable had occurred on the some day of Nov., especially that seen by Humboldt at Cumana in 1799, and by other observers over a great extent of the earth. November stream was again observed in the U. S. in 1834, between the 13th and 14th, though less intense. Though often vague, and in some years altogether absent, this phenomenon has recurred with such regularity, both in America and Europe, as to establish its periodic character.
Another periodic swarm of considerable regularity is that appearing between the 9th and the 14th of Aug., and noticed in ancient legends as the " fiery tears" of St. Lawrence, whose festival is on the 10th of that month. There are other periodic appearances, and Humboldt gives the following epochs as especially worthy of remark: 22d to 25th of April; 17th of July; 10th of Aug.; 12th to 14th of Nov.; 27th to 29th of Nov.; 6th to 12th of December.
It remains to notice briefly the various opinions that have been advanced as to the origin of Rerolites, and the theory of meteors in general. The hypotheses that have been formed in answer to the question—Whence come those solid masses that fall upon the earth?—are of two kinds; some ascribing to them a telluric origin, and others making them alien to the earth. Of the first kind is the conjecture that they may be stones ejected from terrestrial volcanoes, revolving for a time along with the earth, and at last returning to it. Anotbertheory, which at one time found considerable favor, supposed that the matter of which aerolites are composed existed in the atmosphere in the form of vapor, and was bY some unknown Cause suddenly aggregated and precipitated to the earth. These conjectures arc untenable in the face of the facts of the phenomena stated above, and are now completely given up.