of space, their surfaces are quickly cooled, as Moissan cooled his
prepared iron by throwing it into water, and thus the requisite stress
is set up within, and, as the iron solidifies, the included carbon
crystallizes into diamonds. Whether this explanation has a germ of
truth in it or not, at any rate it is evident that iron meteorites
were not created in the form in which they come to us; they must once
have been parts of immeasurably more massive bodies than themselves.

The fall of meteorites offers an appreciable, though numerically
insignificant, peril to the inhabitants of the earth. Historical
records show perhaps three or four instances of people being killed by
these bodies. But for the protection afforded by the atmosphere, which
acts as a very effective shield, the danger would doubtless be very
much greater. In the absence of an atmosphere not only would more
meteorites reach the ground, but their striking force would be
incomparably greater, since, as we have seen, the larger part of their
original velocity is destroyed by the resistance of the air. A
meteorite weighing many tons and striking the earth with a velocity of
twenty or thirty miles per second, would probably cause frightful
havoc.

It is a singular fact that recent investigations seem to have proved
that an event of this kind actually happened in North America --
perhaps not longer than a thousand or two thousand years ago. The
scene of the supposed catastrophe is in northern central Arizona, at
Coon Butte, where there is a nearly circular crater in the middle of a
circular elevation or small mountain. The crater is somewhat over four
thousand feet in diameter, and the surrounding rim, formed of upturned
strata and ejected rock fragments, rises at its highest point one
hundred and sixty feet above the plain. The crater is about six