and usually fall after the explosion of the
bolides. Those meteors, moreover, are
occasioned by tho rapid passage through
our atmosphere of solid bodies existing in
space, and which the earth encounters along
her orbit.

Aërolites, touched immediately after their
fall, are found to be burning hot. But
they cool with very great rapidity; a proof
that their high temperature was merely
superficial, and had not penetrated their
entire mass. As to their form, it is coarsely
polyhedral, with irregular sides and edges.
The flat portions of their surfaces often
present hollows like those produced by
pressing a round body, as a marble or an
upple, on a layer of paste or dough. They
are also covered with a thin, black crust,
usually dull, but sometimes shining like a
varnish.

The merely superficial heat of aërolites
at the moment of their fall, and the thin,
black crust which covers them, clearly
demonstrate that they have been
subjected, for a very short time, to intense
heat, which has melted their outer shell
without penetrating to any depth within.
On breaking an aërolite and exposing one
of its fragments to the flame of a blow-pipe,
you produce on the surface of the fragment
a crust exactly similar to that which
covered the entire aërolite. Doubt on the
subject is no longer possible. Besides which,
the black crust is often wrinkled, owing to
the rapid passage of the air over the melted
surface.

And now, what is the cause of the
intense but short-lived incandescence of
bolides? Chladni, we have seen, thought it
owing to the friction of the air; Benzenberg,
in 1811, supposed it rather due to
the compression of the air. M. Regnault,
after experiments on gases flowing with
great rapidity, made in 1854, came to the
same conclusion, namely, that the
temperature of bolides is solely owing to the
heat disengaged by the compression of air.
When a body moves through the
atmosphere with a velocity greater than that
of sound, the air's elasticity is neutralised,
and compression takes place as if it were
enclosed in a vessel. The violent heating
of the bolide, during the short lapse of
time occupied by its passage through the
air, is the necessary consequence.

Showers of iron are much rarer, at least
at the present epoch, than showers of stones.
Meteoric iron presents itself in masses quite
free from stony matter, and sometimes
sufficiently pure to be forged immediately. It
has even been employed in the fabrication
of tools and weapons. Meteorites also
contain many other materials of great terrestrial
importance, such as oxygen, hydrogen,
and carbon. They hence lay claim to a
community of origin with the planets which
revolve round the sun; which is confirmed
by the recent discovery of numerous
extremely small planets and the probable
existence of others smaller still, which
remain invisible in consequence of the trifling
quantity of sunlight they reflect.

Of late years, great pains have been
taken to form collections of stones fallen
from the sky. We may specially cite those
in the British Museum, in the Mineralogical
Museum at Vienna, and in the Museum
d'Histoire Naturelle, at Paris. The last
contains specimens of two hundred and
thirty-five falls, that is of nearly all; since
the number of stone showers represented
in collections does not exceed two hundred
and fifty.

ALL SORTS.

THERE is held in the northern outskirts
of the metropolis, every Friday afternoon,
a market which is not recognised among
the regular markets noticed in guide books
and directories. It is a sort of interpolation,
an irregularity, an unintended
adjunct, an unexpected growth; and yet it is
very useful notwithstanding. When London
would no longer be tormented with Smithfield,
the authorities built a new market out
in the fields; and a first-rate market it is.
Not that there are any fields near it now;
the builders have taken good care to prevent;
that. The market was opened for trade,
fourteen or fifteen years ago; and there
has been plenty of bellowing and bleating
in it ever since. Mondays and Fridays
were at first adopted as market days;
Thursday was then substituted for Friday;
and there is nothing now for butchers,
or salesmen, or graziers to do there on
Tuesdays, Wednesdays, Fridays, or Saturdays.
A horse market used to be held
once a week at Smithfield; and this,
in like manner, has been transferred to the
new establishment, where it is held on
Fridays. Now, the growth, the adjunct, is in
another part of the area, but held at the
same time as the horse market. The space
being thirty acres in extent, there is ample
room for something besides horses. And
so a singularly strange miscellaneous market
has sprung up} a market which we