Chladni states that an Italian physicist, Paolo Maria Terzago, on the occasion of the fall of an aerolite at Milan, in 1660, by which a Franciscan monk was killed, was the first who surmised that aerolites were of selenic origin. Without any previous knowledge of this conjecture, Olbers was led, in 1795 (after the celebrated fall at Siena, June 16th, 1794), to investigate the amount of the initial tangential force that would be required to bring to the earth masses projected from the moon. Olbers, Brandes, and Chaldni thought that “the velocity of 16 to 32 miles, with which fire-balls and shooting-stars entered our atmosphere,” furnished a refutation to the view of their selenic origin. According to Olbers, it would require to reach the earth, setting aside the resistance of the air, an initial velocity of 8292 feet in the second; according to Laplace, 7862; to Biot, 8282; and to Poisson, 7595. Laplace states that this velocity is only five or six times as great as that of a cannon-ball; but Olbers has shown that “with such an initial velocity as 7500 or 8000 feet in a second, meteoric stones would arrive at the surface of our earth with a velocity of only 35,000 feet.” But the measured velocity of meteoric stones averages upwards of 114,000 feet to a second; consequently the original velocity of projection from the moon must be almost 110,000 feet, and therefore 14 times greater than Laplace asserted. It must, however, be recollected, that the opinion then so prevalent, of the existence of active volcanoes in the moon, where air and water are absent, has since been abandoned. Laplace elsewhere states, that in all probability aerolites “come from the depths of space;” yet he in another passage inclines to the hypothesis of their lunar origin, always, however, assuming that the stones projected from the moon “become satellites of our earth, describing around it more or less eccentric orbits, and thus not reaching its atmosphere until several or even many revolutions have been accomplished.” In Syria there is a popular belief that aerolites chiefly fall on clear moonlight nights. The ancients (Pliny tells us) looked for their fall during lunar eclipses.--_Abridged from Humboldt’s Cosmos_, vol. i. (Bohn’s edition). Dr. Laurence Smith, U.S., accepts the “lunar theory,” and considers meteorites to be masses thrown off from the moon, the attractive power of which is but one-sixth that of the earth; so that bodies thrown from the surface of the moon experience but one sixth the retarding force they would have when thrown from the earth’s surface.