tify the hypothesis.

I must tell you now the history of three bodies, and you will see that
some intimate connection between comets and meteors is proved. The
three bodies are known as, first, Encke's comet; second, Biela's comet;
third, the November swarm of meteors.

Encke's comet (one of those discovered by Miss Herschel) is an
insignificant-looking telescopic comet of small period, the orbit of
which was well known, and which was carefully observed at each
reappearance after Encke had calculated its orbit. It was the quickest
of the comets, returning every 3-1/2 years.

[Illustration: FIG. 103.--Encke's comet.]

It was found, however, that its period was not quite constant; it kept
on getting slightly shorter. The comet, in fact, returned to the sun
slightly before its time. Now this effect is exactly what friction
against a solar atmosphere would bring about. Every time it passed near
the sun a little velocity would be rubbed out of it. But the velocity is
that which carries it away, hence it would not go quite so far, and
therefore would return a little sooner. Any revolving body subject to
friction must revolve quicker and quicker, and get nearer and nearer
its central body, until, if the process goes on long enough, it must
drop upon its surface. This seems the kind of thing happening to Encke's
comet. The effect is very small, and not thoroughly proved; but, so far
as it goes, the evidence points to a greatly extended rare solar
atmosphere, which rubs some energy out of it at every perihelion
passage.

[Illustration: FIG. 104.--Biela's comet as last seen, in two portions.]

Next, Biela's comet. This also was a well known and carefully observed
telescopic comet, with a period of six years. In one of its distant
excursions, it was calculated that it must pass very near Jupiter, and
much curiosity was excited as to what would happen to it in consequence
of the perturbation it must experience. As I have said, comets are only
visible as they approach the sun, and a watch was kept for it about its
appointed time. It was late, but it did ultimately arrive.

The singular thing about it, however, was that it was now double. It had
apparently separated into two. This was in 1846. It was looked for again
in 1852, and this time the components were further separated. Sometimes
one was brighter, sometimes the other. Next time it ought to have come
round no one could find either portion. The comet seemed to have wholl