s not absolutely prove our conjecture to be right, yet it will
give us a very lively conception of the manner, in which the phaenomenon
may be caused.

This probability may be shewn in the case of _freckles_, which are
to be seen in the face of children, but of such only, as have the
thinnest and most transparent skins, and are occasioned by the rays of
the sun, striking forcibly on the _mucous substance_ of the face,
and drying the accumulating fluid. This accumulating fluid, or
perspirable matter, is at first colourless; but being exposed to violent
heat, or dried, becomes brown. Hence, the _mucosum corpus_ being
tinged in various parts by this brown coagulated fluid, and the parts so
tinged appearing through the _cuticle_, or upper surface of the
skin, arises that spotted appearance, observable in the case recited.

Now, if we were to conceive a black skin to be an _universal
freckle_, or the rays of the sun to act so universally on the
_mucous substance_ of a person's face, as to produce these spots so
contiguous to each other that they should unite, we should then see, in
imagination, a face similar to those, which are daily to be seen among
black people: and if we were to conceive his body to be exposed or acted
upon in the same manner, we should then see his body assuming a similar
appearance; and thus we should see the whole man of a perfect black, or
resembling one of the naked inhabitants of the torrid zone. Now as the
feat of freckles and of blackness is the same; as their appearance is
similar; and as the cause of the first is the ardour of the sun, it is
therefore probable that the cause of the second is the same: hence, if
we substitute for the word "_sun_," what is analogous to it, the
word _climate_, the same effect may be supposed to be produced, and
the conjecture to receive a sanction.

Nor is it unlikely that the hypothesis, which considers the cause of
freckles and of blackness as the same, may be right. For if blackness is
occasioned by the rays of the sun striking forcibly and universally on
the _mucous substance_ of the body, and drying the accumulating
fluid, we can account for the different degrees of it to be found in the
different inhabitants of the globe. For as the quantity of perspirable
fluid, and the force of the solar rays is successively increased, as
the climates are successively warmer, from any given parallel to the
line, it follows that the fluid, with which the _mucous substance