that the probability of a contact is less, in an almost infinite degree,
than the proximity of a comet, which, notwithstanding, is an event which
every astronomer is fully aware, is within the verge of possibility.

The effects of a contact would be greatly modified by circumstance. Should
the comet strike the earth obliquely, it would glance off, and the
consequences would be partial. If the point of collision were on a
continent of the globe, mountains would be hurled from their bases, and
new ones would elevate their ridges towards the clouds. Were the place of
meeting on either of the great oceans, some regions would be deserted, and
others would be inundated by the waters of the sea. These dreadful
consequences would be increased, in an indefinite proportion, if the point
of contact were in the direction of the earth's centre; the meeting would
be terrific; the earth's period of revolution would, in all probability,
be altered, either by carrying it nearer to or farther from the sun; a
different inclination of the axis might be given, and there would be a
consequent change of seasons; the diurnal motion might be either
accelerated or retarded, by which the length of the day would be affected;
the vast continents of the globe would be again covered with the ocean,
which, deserting its bed, would rush towards the new equator.

Infinitely more tremendous would be the catastrophe if the earth were
struck by a _retrograde comet_ in the direction of the terrestrial centre,
the comet making up, by its velocity, the deficiency of mass: in this case
the centrifugal force of both bodies might be annihilated,--the
centripetal principle alone obeyed, and both comet and earth rush to the
sun!

It must, however, be stated, that the probability of such an event is all
but infinitely removed: the most likely of any that is known, to effect