before its collision with the
earth's atmosphere. Several attempts have therefore been made to search
for approaching swarms by photography, but, so far, it appears without
success. It has also been proposed, by Mr. W.H.S. Monck, that the stars
in those regions from which swarms are due, should be carefully watched,
to see if their light exhibits such temporary diminutions as would be
likely to arise from the momentary interposition of a cloud of moving
particles.

Between ten and fifteen years ago it happened that several well-known
observers, employed in telescopic examination of the sun and moon,
reported that from time to time they had seen small dark bodies,
sometimes singly, sometimes in numbers, in passage across the discs of
the luminaries. It was concluded that these were meteors moving in space
beyond the atmosphere of the earth. The bodies were called "dark
meteors," to emphasise the fact that they were seen in their natural
condition, and not in that momentary one in which they had hitherto been
always seen; _i.e._ when heated to white heat, and rapidly vaporised, in
the course of their passage through the upper regions of our air. This
"discovery" gave promise of such assistance to meteor theories, that
calculations were made from the directions in which they had been seen
to travel, and the speeds at which they had moved, in the hope that some
information concerning their orbits might be revealed. But after a while
some doubt began to be thrown upon their being really meteors, and
eventually an Australian observer solved the mystery. He found that they
were merely tiny particles of dust, or of the black coating on the inner
part of the tube of the telescope, becoming detached from the sides of
the eye-piece and falling across the field of view. He was led to this
conclusion by having noted that a gentle tapping of his instrument
produced the "dark" bodies in great numbers! Thus the opportunity of
observing meteors beyond our atmosphere had once more failed.

_Meteorites_, also known as aerolites and fireballs, are usually placed
in quite a separate category from meteors. They greatly exceed the
latter in size, are comparatively rare, and do not appear in any way
connected with the various showers of meteors. The friction of their
passage through the atmosphere causes them to shine with a great light;
and if not shattered to pieces by internal explosions, they reach the
ground to bury themselves deep in i