Some years ago, a farmer living near Rowton, in Shropshire, noticed
on a path in a field a hole which had been suddenly made by some
mysterious and unknown agent. The laborers who were near told him they
had just heard a remarkable noise; and when the farmer put his hand
down into the hole, he felt something hot at the bottom of it. He took
a spade and dug up the strange body, and found it to be a piece of
iron, weighing about seven pounds. He was naturally amazed at such an
occurrence, and brought the body home with him.
Where did that piece of iron come from? It is plain that it could not
have been always in the ground. The noise and the recently made hole
showed that was not the case, and that is confirmed by the fact that
the iron was hot. A piece of iron within a few feet of the earth’s
surface cannot have remained warm for any length of time. It is
therefore clear that the iron must have tumbled from the sky. This is
a marvellous notion; in fact, it seems so incredible that at first
people refused to believe that such things as stones or solid lumps of
iron could have fallen from the heavens to the earth. But they had to
believe it; the evidence was too conclusive. Fortunately, however,
the occurrence is a comparatively rare one; indeed, our life on this
globe would have an intolerable anxiety added to it if showers of iron
hailstones like that at Rowton were at all of frequent occurrence. We
should want umbrellas of a more substantial description than those
which suffice for the rains we actually experience. There are, indeed,
instances on record of persons having been killed by the fearful blows
given by these bodies in falling.
The Rowton siderite is a comparatively small one; pieces weighing
hundredweights, and even tons, have been collected together in our
museums. I would recommend you to pay a visit to that interesting room
in our great British Museum in which these meteorites are exhibited.
There we see actual specimens of celestial bodies which we can feel
or weigh, and which our chemists can analyze. It may be noticed that
they only contain substances that we already know on this earth. This
celestial iron has often been made use of in primitive times before
man understood how to smelt iron from its ore and how to transform it
from cast iron to wrought iron. Nature seems to have taken heed of
their wants, and occasionally to have thrown down a lump or two for the
benefit of those who were so fortunate as to secure them.
That these stones or irons drop from the sky is absolutely certain,
but when we try to find out their earlier history we become involved
in not a few difficulties. Nobody really knows the true history of
these objects, but the view of their origin which seems to me to
possess fewer difficulties than any other view is that which we may
call the Columbiad Theory. I use this expression because every boy or
girl listening to me ought to have read Jules Verne’s wonderful book,
“From the Earth to the Moon,” and if any of you have not read it, the
sooner you do so the better. It is there narrated how the gun club of
Baltimore designed a magnificent cannon which was sunk deep into the
ground, and then received a terrific charge of guncotton, on which a
great hollow projectile was carefully lowered, containing inside the
three adventurous explorers who desired to visit the moon. Calculations
were produced with a view of showing that by firing on a particular
day the explosion would drive the projectile up to the moon. There
was, however, the necessary condition that the speed of projection
should be great enough. The gun club were accurate in saying that if
the cannon were able to discharge the projectile with a speed twenty
or thirty times as great as that which had ever been obtained with
any other cannon, then the missile would ascend up and up forever if
no further influence were exerted on it. No doubt we have to overlook
the resistance on the air and a few other little difficulties, but to
this extent, at all events, the gun club were right: that a velocity of
about six or seven miles a second would suffice to carry a body away
from the gravitation of the earth.
No one supposes that there were ever Columbiad cannons on our globe by
which projectiles were shot up into space; but it seems possible that
there may have been in very ancient days volcanoes on the earth with a
shooting power as great as that which President Barbicane designed for
the big cannon.
Even now we have some active volcanoes of great energy on our earth,
and we know that in former days the volcanoes must have been still more
powerful; that, in fact, the Vesuvius of the present must be merely
a popgun in comparison with volcanoes which have shaken the earth in
those primitive days when it had just cooled down from its original
fiery condition. Some of these early volcanoes, in the throes of their
mighty eruptions, appear to have shot forth pieces of iron and volcanic
substances with a violence great enough to carry them off into space.
Suppose that a missile were projected upwards, it would ascend higher
and higher, and gravity would, of course, tend to drag it back again
down to earth. It can be shown that with an initial speed of six or
seven miles a second the missiles would never return to the earth if
only influenced by its attraction. The subsequent history of such a
projectile would be guided by the laws according to which a planet
moves. The body is understood to escape the destination which was aimed
at by the Columbiad. I mean, of course, that it is not supposed to hit
the moon. Of course, this might conceivably happen; but most of the
projectiles would go quite wide of the mark, and would travel off into
space.
Though the earth would be unable to recall the projectile, the
attraction of the sun would still guide it, whether it was as big as
a paving-stone or ever so much larger or smaller. The body would be
constrained to follow a path like a little planet around the sun. This
track it would steadily pursue for ages. The wanderer would, however,
cross the earth’s track once during each of its revolutions at the
point from which it was projected. Of course, it will generally happen
that the earth will not be there at the time the meteorite is crossing,
and the meteorite will not be there at the time the earth is crossing.
Nothing will therefore happen, and the object goes again on its long
rounds. But sometimes it must occur that a meteor does not get past
the junction without coming so close to the earth that it plunges into
the air, often producing a noise and generating a streak of light like
a shooting star. Then it tumbles down, and is restored to that earth
whence it originally came.
If this be the true view--and I think there are less weighty objections
to it than to any other I know of--then the history of the piece
of iron that was found in Shropshire would be somewhat as follows.
Many millions of years ago, when the fires of our earth were much
more vigorous than they are in these dull times, a terrific volcanic
outbreak took place, and vast quantities of material were shot into
space, of which this is one of the fragments. During all the ages that
have since elapsed this piece of iron has followed its lonely track. In
a thousandth part of the time rust and decay would have destroyed it
had it lain on the earth, but in the solitudes of space there was found
no air or damp to produce corrosion. At last, after the completion of
its long travels, it again crashed down on the earth.
We have now briefly surveyed the extent of the solar system. We began
with the sun, which presides over all, and then we discussed the
various planets with their satellites, next we considered the eccentric
comets, and finally the minute bodies which, as shooting stars or
meteorites, must be regarded as forming part of the Sun’s system. In
our closing lecture we shall have to deal with objects of a far more
magnificent character.