me extent, and once in thirty-three
years seem to run right into the middle of them? This also was answered.
One has only to imagine a swarm of such meteors at first hastening
busily along their orbit, a great cluster all together, then, by the
near neighbourhood of some planet, or by some other disturbing causes,
being drawn out, leaving stragglers lagging behind, until at last there
might be some all round the path, but only thinly scattered, while the
busy, important cluster that formed the nucleus was still much thicker
than any other part. Now, if the orbit that the meteors followed cut the
orbit or path of the earth at one point, then every time the earth came
to what we may call the level crossing she must run into some of the
stragglers, and if the chief part of the swarm took thirty-three years
to get round, then once in about thirty-three years the earth must
strike right into it. This would account for the wonderful display. So
long drawn-out is the thickest part of the swarm that it takes a year to
pass the points at the level crossing. If the earth strikes it near the
front one year, she may come right round in time to strike into the rear
part of the swarm next year, so that we may get fine displays two years
running about every thirty-three years. The last time we passed through
the swarm was in 1899, and then the show was very disappointing. Here in
England thick clouds prevented our seeing much, and there will not be
another chance for us to see it at its best until 1932.

These November meteors are called Leonids, because they _seem_ to come
from a group of stars named Leo, and though the most noticeable they are
not the only ones. A shower of the same kind occurs in August too, but
the August meteors, called Perseids, because they seem to come from
Perseus, revolve in an orbit which takes a hundred and forty-two years
to traverse! So that only every one hundred and forty-second year could
we hope to see a good display. When all these facts had been gathered
up, it seemed without doubt that certain groups of meteors travelled in
company along an elliptical orbit. But there remained still something
more--a bold and ingenious theory to be advanced. It was found that a
comet, a small one, only to be seen with the telescope, revolved in
exactly the same orbit as the November meteors, and another one, larger,
in exactly the same orbit as the August ones; hence it could hardly be
doubted that comets and meteo