The differences existing between that which appertains to the air
of heaven (the realms of universal space) and that which belongs to
the strata of our terrestrial atmosphere are very striking. It is
not possible, as well-attested facts prove, perfectly to explain
the operations at work in the much-contested upper boundaries of
our atmosphere. The extraordinary lightness of whole nights in the
year 1831, during which small print might be read at midnight in
the latitudes of Italy and the north of Germany, is a fact directly
at variance with all we know according to the researches on the
crepuscular theory and the height of the atmosphere. The phenomena
of light depend upon conditions still less understood; and their
variability at twilight, as well as in the zodiacal light, excite our
astonishment. Yet the atmosphere which surrounds the earth is not
thicker in proportion to the bulk of our globe than the line of a
circle two inches in diameter when compared with the space which it
encloses, or the down on the skin of a peach in comparison with the
fruit inside.