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 that we know, according to the most recent and
acute researches on the crepuscular theory and the height of the
atmosphere.--_Biot._