er except the comet
of 1843--the danger not, however, being that derived from possible
collision between the earth and a comet, but that arising from the
possible downfall of a large comet upon the sun, and the consequent
enormous increase of the sun's heat. That, according to Newton, is the
great danger men have to fear from comets; and the comet of 1680 was one
which in that sense was a very dangerous one. There is no reason why a
comet from outer space should not fall straight towards the sun, as at
one time the comet of 1680 was supposed to be doing. All the comfort
that science can give the world on that point is that such a course for
a comet is only one out of many millions of possible courses, all fully
as likely; and that, therefore, the chance of a comet falling upon the
sun is only as one in many millions. Still, the comet of 1680 made a
very fair shot at the sun, and a very slight modification of its course
by Jupiter or Saturn might have brought about the catastrophe which
Newton feared. Whether, if a comet actually fell upon the sun, anything
very dreadful would happen, is not so clear. Newton's ideas respecting
comets were formed in ignorance of many physical facts and laws which in
our day render reasoning upon the subject comparatively easy. Yet, even
in our time, it is not possible to assert confidently that such fears
are idle. During the solar outburst witnessed by Carrington and Hodgson
in September 1859, it is supposed that the sun swallowed a large
meteoric mass; and, as great cornets are probably followed by many such
masses, it seems reasonable to infer that if such a comet fell upon the
sun, his surface being pelted with such exceptionally large masses,
stoned with these mighty meteoric balls, would glow all over (or nearly
so) as brightly as a small spot of that surface glowed upon that
occasion. Now that portion was so bright that Carrington thought 'that
by some chance a ray of light had penetrated a hole in the screen
attached to the object-glass by which the general image is thrown in
shade, for the brilliancy was fully equal to that of direct sunlight.'
Manifestly, if the whole surface of the sun, or any large portion of the
surface, were caused to glow with that exceeding brilliancy, surpassing
ordinary sunlight in the same degree that ordinary sunlight surpassed
the shaded solar image in Carrington's observations, the result would be
disastrous in the extreme for the inhabitants of that h