COMETS AND METEORITES.
A curious discovery has been lately made. It is that some sort of
mysterious tie seems to exist between comets and meteorites. For a long
while this was never suspected. How should it be? The comets, so large,
so airy, so light; the meteorites, so small, so solid, so heavy,--how
could it possibly be supposed that the one had anything to do with
the other? But supposings often have to give in to facts. Astronomers
are gradually becoming convinced that there certainly is a connection
between the two.
Strange to say, comets and meteorites occupy--sometimes, at least--the
very same pathways in the heavens, the very same orbits round the
sun. A certain number of meteorite systems are now pretty well known
to astronomers as regularly met by our earth at certain points in
her yearly journey. Some of these systems or rings have each a comet
belonging to it--not merely journeying near, but actually in its midst,
on the same orbit.
Perhaps it would be more correct to say that the meteorites belong to
the comet, than that the comet belongs to the meteorites. We tread here
on uncertain ground; for whether the meteorites spring from the comet,
or whether the comet springs from the meteorites, or whether each has
been brought into existence independently of the other, no one can at
present say.
Though it is out of our power to explain the kind of connection, yet a
connection there plainly is. So many instances are now known of a comet
and a meteorite ring traveling together that it is doubtful whether any
such ring could be found without a comet in its midst. By and by the
doubt may spring up whether there ever exists a comet without a train
of meteorites following him.
Among the many different meteorite rings which are known, two of the
most important are the so-called August and November systems. Of these
two, the November system must claim our chief attention. Not that we
are at all sure of these being the most important meteorite rings in
the Solar System. On the contrary, as regards the November ring, we
have some reason to think that matters may lie just the other way.
The comet belonging to the November system is a small one--quite an
insignificant little comet--only visible through a telescope. We
do not, of course, know positively that larger comets and greater
meteorite systems generally go together, but, to say the least, it
seems likely. And if the greatness of a ring can at all be judged of by
the size of its comet, then the November system must be a third-rate
specimen of its kind. It is of particular importance to us, merely
because it happens to be the one into which our earth plunges most
deeply, and which we therefore see and know the best. The August ring
is, on the contrary, connected with a magnificent comet, and may be
a far grander system. But our pathway does not lead us into the midst
of the August meteors as into those of November. We pass, seemingly,
through its outskirts.
The meteorites of the November system are very small. They are believed
to weigh commonly only a few grains each. If they were larger and
heavier, some of them would fall to earth as aerolites, not more than
half-burnt in their rush through the atmosphere. But this they are
never found to do.
There are known meteorite systems, which our earth merely touches
or grazes in passing, from which drop aerolites of a very different
description--large, heavy, solid masses. It is well for us that we do
not plunge into the midst of any such ring, or we might find our air,
after all, a poor protection.
The last grand display of the November system of meteorites took place
in the years 1866 to 1869, being continued more or less during three or
four Novembers following. The next grand display will occur in the year
1899.
For this system--Leonides, as it is called, because the falling-stars
in this display seem all to shoot towards us from a spot in the
constellation Leo--seems to have a “time” or “year” of thirty-three and
a quarter earthly years. The shape of its orbit is a very long ellipse,
near one end of which is the sun, while the other end is believed to
reach farther away than the orbit of Uranus.
A great deal of curiosity has been felt about the actual length and
breadth and depth of the stream of meteorites through which our
solid earth has so often plowed her way. During many hours at a
time, lookers-on have watched the magnificent display of heavenly
fireworks,--not a mere shooting-star here and there, as on common
nights, but radiant meteors, flashing and dying by thousands through
the sky. In 1866 no less than eight thousand meteors, in two hours and
a quarter, were counted from the Greenwich Observatory in England. A
natural wonder sprang up in many minds as to the extent of the ring
from which they fell.
For not in one night only, but in several nights during three or four
years, and that not once only but once in every thirty-three years,
thousands and tens of thousands appear to have been stolen by our earth
from the meteorite-ring, never again to be restored. Yet each time we
touch the ring, we find the abundance of little meteorites in nowise
seemingly lessened.
When speaking of a “ring” of meteorites, it must not be supposed that
necessarily the meteorites form a whole unbroken ring all round the
long oval orbit. There may be no breaks. There may be a more or less
thin scattering throughout the entire length of the pathway. But the
meteorites certainly seem to cluster far more densely in some parts of
the orbit than in other parts, and it was about the size of the densest
cluster that so much curiosity was felt.
Little can be positively known, though it is very certain that the
cluster must be enormous in extent. Three or four years running, as our
earth, after journeying the whole way round the sun, came again to that
point in her orbit where she passes through the orbit of the Leonides,
she found the thick stream of meteorites still pouring on, though each
year lessening in amount. Taking into account this fact, and also the
numbers that were seen to fall night after night, and also the speed of
our earth, a “rough estimate” was formed.
The length of this dense cluster is supposed to reach to many
hundreds of millions of miles. The thickness or depth of the stream
is calculated to be in parts over five hundred thousand miles, and
the breadth about ten times as much as the depth. Each meteorite is
probably at a considerable distance from his neighbor; but the whole
mass of them, when in the near neighborhood of the sun, must form a
magnificent sight.
And if this be only a third-rate system, what must a first-rate system
be like? And how many such systems are there throughout the sun’s wide
domains? The most powerful telescope gives us no hint of the existence
of these rings till we find ourselves in their midst.
It may be that they are numbered by thousands, even by millions. The
whole of the Solar System--nay, the very depths of space beyond--may,
for aught we know, be crowded with meteorite systems. Every comet may
have his stream of meteorites following him. But though the comet is
visible to us, the meteorites are not. Billions upon billions of them
may be ever rushing round our sun, entirely beyond our ken, till one
or another straggler touches our atmosphere to flash and die as a
“shooting star” in our sight.
We have, and with our present powers we can have, no certainty as
to all this. But I may quote here the illustration of a well-known
astronomical writer on the subject.
Suppose a blind man were walking out of doors along a high road, and
during the course of a few miles were to feel rain falling constantly
upon him. Would it be reasonable on his part, if he concluded that a
small shower of rain had accompanied him along the road as he moved,
but that fine weather certainly existed on either side of the road? On
the contrary, he might be sure that the drops which he felt, were but a
few among millions falling all together.
Or, look at the raindrops on your window some dull day at home. Count
how many there are? Could you, with any show of common sense, decide
that those raindrops, and those alone, had fallen that day? So, when
we find these showers of meteorites falling to earth, we may safely
conclude that, for every one which touches our atmosphere, myriads rush
elsewhere in space, never coming near us.