-tempest were trailing over Mexico, "a ball
of fire" was precipitated from the sky at Mazapil, within view of a
ranchman.[1244] Scientific examination proved it to be a "siderite," or
mass of "nickel-iron"; its weight exceeded eight pounds, and it
contained many nodules of graphite. We are not, however, authorised by
the circumstances of its arrival to regard the Mazapil fragment of
cosmic metal as a specimen torn from Biela's comet. In this, as in the
preceding case, the coincidence of the fall with the shower may have
been purely casual, since no hint is given of any sort of agreement
between the tracks followed by the sample provided for curious study,
and the swarming meteors consumed in the upper air.

Professor Newton's inquiries into the tracks pursued by meteorites
previous to their collisions with the earth tend to distinguish them, at
least specifically, from shooting-stars. He found that nearly all had
been travelling with a direct movement in orbits the perihelia of which
lay in the outer half of the space separating the earth from the
sun.[1245] Shooting-stars, on the contrary, are entirely exempt from
such limitations. The Yale Professor concluded "that the larger
meteorites moving in our solar system are allied much more closely with
the group of comets of short period than with the comets whose orbits
are nearly parabolic." They would thus seem to be more at home than
might have been expected amid the planetary family. Father Carbonelle
has, moreover, shown[1246] that meteorites, if explosion-products of the
earth or moon, should, with rare exceptions, follow just the kind of
paths assigned to them, from data of observation, by Professor Newton.
Yet it is altogether improbable that projectiles from terrestrial
volcanoes should, at any geological epoch, have received impulses
powerful enough to enable them, not only to surmount the earth's
gravity, but to penetrate its atmosphere.

A striking--indeed, an almost startling--peculiarity, on the other
hand, divides from their congeners a class of meteors identified by
Mr. Denning during ten years' patient watching of such phenomena at
Bristol.[1247] These are described as "meteors with stationary
radiants," since for months together they seem to come from the same
fixed points in the sky. Now this implies quite a portentous velocity.
The direction of meteor-radiants is affected by a kind of
_aberration_, analogous to the aberration of light. It results from