_Herodotus_[093] relates, that the _Colchi were black_, and that they had _crisped hair_.

These people were a detachment of the _AEthiopian_ army under _Sesostris_, who followed him in his expedition, and settled in that part of the world, where _Colchis_ is usually represented to have been situated.

Had not the same author informed us of this circumstance, we should have thought it strange[094], that a people of this description should have been found in such a latitude.

Now as they were undoubtedly settled there, and as they were neither so totally destroyed, nor made any such rapid conquests, as that history should notice the event, there is great reason to presume, that their descendants continued in the same, or settled in the adjacent country; from whence it will follow, that they must have changed their complexion to that, which is observable in the inhabitants of this particular region at the present day; or, in other words, that the _black inhabitant of Colchis_ must have been changed into the _fair Circassian_[095].
As we have now shewn it to be highly probable, from the facts which have been advanced, that climate is the cause of the difference of colour which prevails in the different inhabitants of the globe, we shall now shew its probability from so similar an effect produced on the _mucous substance_ before-mentioned by so similar a cause, that though the fact does 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.