; and it is not unlikely that these may have all been seen in some
parts of the earth. Sometimes they may have been witnessed by savages,
who had neither the inclination nor the means to place on record an
apparition which to them was a source of terror. Sometimes, however,
these showers were observed by civilised communities. Their nature was
not understood, but the records were made; and in some cases, at all
events, these records have withstood the corrosion of time, and have now
been brought together to illustrate this curious subject. We have
altogether historical notices of twelve of these showers, collected
mainly by the industry of Professor H.A. Newton whose labours have
contributed so much to the advancement of our knowledge of shooting
stars.

Let us imagine a swarm of small objects roaming through space. Think of
a shoal of herrings in the ocean, extending over many square miles, and
containing countless myriads of individuals; or think of those enormous
flocks of wild pigeons in the United States of which Audubon has told
us. The shoal of shooting stars is perhaps much more numerous than the
herrings or the pigeons. The shooting stars are, however, not very close
together; they are, on an average, probably some few miles apart. The
actual bulk of the shoal is therefore prodigious; and its dimensions are
to be measured by hundreds of thousands of miles.

[Illustration: Fig. 76.--The Orbit of a Shoal of Meteors.]

The meteors cannot choose their own track, like the shoal of herrings,
for they are compelled to follow the route which is prescribed to them
by the sun. Each one pursues its own ellipse in complete independence of
its neighbours, and accomplishes its journey, thousands of millions of
miles in length, every thirty-three years. We cannot observe the meteors
during the greater part of their flight. There are countless myriads of
these bodies at this very moment coursing round their path. We never see
them till the earth catches them. Every thirty-three years the earth
makes a haul of these meteors just as successfully as the fisherman
among the herrings, and in much the same way, for while the fisherman
spreads his net in which the fishes meet their doom, so the earth has an
atmosphere wherein the meteors perish. We are told that there is no fear
of the herrings becoming exhausted, for those the fishermen catch are as
nothing compared to the profusion in which they abound in ocean. We may
say the sa