gin of these remarkable bodies. Some have supposed
them to have been shot out from volcanoes belonging to our earth; but
this theory is opposed by the fact that no substance, resembling
aerolites, has ever been found in or near any volcano; and they fall from
a height to which no volcano can be supposed to have projected them, and
still less to have given them the horizontal direction in which they
usually move. Another supposition is, that these masses are formed in
the atmosphere; but it is almost ridiculous to imagine a body, weighing
many tons, to be produced by any chemical or electrical forces in the
upper regions of the air. A third explanation is, that they are bodies
thrown out by the volcanoes, which are known to exist in the moon, with
such force as to bring them within the sphere of the earth's attraction.
This notion was supported by the celebrated astronomer and mathematician
La Place. He calculated that a body projected from the moon with the
velocity of 7771 feet in the first second, would reach our earth in about
two days and a half. But other astronomers are of opinion, that the
known velocity of some meteors is too great to admit of the possibility
of their having come from the moon. The theory which agrees best with
known facts and the laws of nature, is that proposed by Chladni, namely,
that the meteors are bodies moving in space, either masses of matter as
originally created, or fragments separated from a larger mass of a
similar nature. This view has also been supported by Sir Humphrey Davy,
who says, "The luminous appearances of shooting-stars and meteors cannot
be owing to any inflammation of elastic fluids, but must depend upon the
ignition of solid bodies. Dr. Halley calculated the height of a meteor
at ninety miles; and the great American meteor, which threw down showers
of stones, was estimated at seventeen miles high. The velocity of motion
of these bodies must, in all cases, be immensely great, and the heat
produced by the compression of the most rarefied air from the velocity of
motion, must be, probably, sufficient to ignite the mass; and all the
phenomena may be explained, if _falling stars_ be supposed to be small
bodies moving round the earth in very eccentric orbits, which become
ignited only when they pass with immense velocity through the upper
region of the atmosphere; and if the meteoric bodies which throw down
stones with explosions, be supposed to be similar bodies which