metallic fragments which in their
journey through space are caught in the earth's atmosphere and
instantaneously ignited by the friction. Far away in the depths of space
one of these bodies felt the attracting power of the sun, and began
moving towards him. As it approached, its speed grew gradually quicker
and quicker continually, until by the time it has approached to within
the distance of the earth, it whizzes past with the velocity of
twenty-six miles a second. The earth is moving on its own account
nineteen miles every second. If the two bodies happened to be moving in
opposite directions, the combined speed would be terrific; and the
faintest trace of atmosphere, miles above the earth's surface, would
exert a furious grinding action on the stone. A stream of particles
would be torn off; if of iron, they would burn like a shower of filings
from a firework, thus forming a trail; and the mass itself would be
dissipated, shattered to fragments in an instant.

[Illustration: FIG. 96.--Meteor stream crossing field of telescope.]

[Illustration: FIG. 97.--Diagram of direction of earth's orbital
motion, showing that after midnight, _i.e._ between midnight and noon,
more asteroids are likely to be swept up by any locality than between
noon and midnight. [From Sir R.S. Ball.]]

Even if the earth were moving laterally, the same thing would occur. But
if earth and stone happened to be moving in the same direction, there
would be only the differential velocity of seven miles a second; and
though this is in all conscience great enough, yet there might be a
chance for a residue of the nucleus to escape entire destruction, though
it would be scraped, heated, and superficially molten by the friction;
but so much of its speed would be rubbed out of it, that on striking
the earth it might bury itself only a few feet or yards in the soil, so
that it could be dug out. The number of those which thus reach the earth
is comparatively infinitesimal. Nearly all get ground up and dissipated
by the atmosphere; and fortunate it is for us that they are so. This
bombardment of the exposed face of the moon must be something
terrible.[31]

Thus, then, every shooting-star we see, and all the myriads that we do
not and cannot see because they occur in the day-time, all these bright
flashes or streaks, represent the death and burial of one of these
flying stones. It had been careering on its own account through space
for untold ages, till it me