substance, before-mentioned, is found to vary
in its colour, as the _climates_ vary from the equator to the
poles, his mind must be instantly struck with the hypothesis, and he
must adopt it without any hesitation, as the genuine cause of the
phaenomenon.

This fact[083], _of the variation of the mucous substance according to
the situation of the place_, has been clearly ascertained in the
numerous anatomical experiments that have been made; in which, subjects
of all nations have come under consideration. The natives of many of the
kingdoms and isles of _Asia_, are found to have their _corpus
mucosum_ black. Those of _Africa_, situated near the line, of
the same colour. Those of the maritime parts of the same continent, of a
dusky brown, nearly approaching to it; and the colour becomes lighter or
darker in proportion as the distance from the equator is either greater
or less. The Europeans are the fairest inhabitants of the world. Those
situated in the most southern regions of _Europe_, have in their
_corpus mucosum_ a tinge of the dark hue of their _African_
neighbours: hence the epidemick complexion, prevalent among them, is
nearly of the colour of the pickled Spanish olive; while in this
country, and those situated nearer the north pole, it appears to be
nearly, if not absolutely, white.

These are facts[084], which anatomy has established; and we acknowledge
them to be such, that we cannot divest ourselves of the idea, that
_climate_ has a considerable share in producing a difference of
colour. Others, we know, have invented other hypotheses, but all of them
have been instantly refuted, as unable to explain the difficulties for
which they were advanced, and as absolutely contrary to fact: and the
inventors themselves have been obliged, almost as soon as they have
proposed them, to acknowledge them deficient.

The only objection of any consequence, that has ever been made to the
hypothesis of _climate_, is this, _that people under the same
parallels are not exactly of the same colour_. But this is no
objection in fact: for it does not follow that those countries, which
are at an equal distance from the equator, should have their climates
the same. Indeed nothing is more contrary to experience than this.
Climate depends upon a variety of accidents. High mountains, in the
neighbourhood of a place, make it cooler, by chilling the air that is
carried over them by the winds. Large spreading succulent plants, if
among