From these causes it is easy to see, how conterminous tribes may differ considerably in their external appear ance, since every thing that influences their habits and manner of living must, in some measure, affect their ap pearance and complexion.
But besides these permanent causes of distinction, there is another which must not be lost sight of; that is, the recent settlement of various tribes within the limits of the torrid zone. It is a fact ascertained beyond the possibility of a doubt, that a tribe which has emigrated from a temperate to a hot climate, will be many ages in acquiring that shade of colour which distinguishes the indigenous inhabitants. Were ive, therefore, to find two tribes possessing the same habits, and enjoying the same temperature as to climate, yet differing considerably as to complexion, it would be absurd to resort to the un philosophical expedient of supposing a difference of spe cies, when the circumstance might be easily explained from the recency or antiquity of their emigration. The world is not yet old enough to ascertain the fact, how long it will take to pass from white to the deepest black. As far as our experience extends, however, we see every generation descended from white parents in the torrid zone acquiring a deeper tinge, and gradually approach ing that complexion which distinguishes the perfect ne gro. We are told that the Portuguese settled at Mitom ba, a river in Sierra Leone, have, by their marriages with the natives, and by the operation of the climate, degene rated into perfect negroes, with woolly hair, thick lips, Sze. and retaining scarcely a trace of their original, ex cept a smattering of the Portuguese language.
We have as satisfactory evidence, that a similar change is produced when negroes are transplanted to a tempe rate climate. Every succeeding generation is fairer than that which preceded it, though we are not as yet able to ascertain what length of time is necessary to wash out the constitutional stain from their skin. \Ve have, however, the most undoubted autnority for the fact. It is express ly affirmed by the Able Raynal, with respect to the de scendants of negro parents in North America ; and more particularly by Dr Smith, of New Jersey, who has exa mined this subject with great accuracy of observation, and who informs us, that the negroes, in the United States, though intermarrying with each other, are gra dually losing the curled hair and black complexion of their African progenitors.
Thus then, great heat, and the exposure of many sue CeSSIN e generations to its influence, are necessary to the production of that colour which distinguishes the negro; and the same length of time, accompanied with an inver sion of circumstances, would be requisite to bring him back to his original hue. The Jews afford the most re markable illustration of these observations : though scat tered over the face of the earth, they have in general re mained a distinct and separate race, with not a drop of blood in their veins but what has flowed in a direct course from Abraham : yet how various is their complexion ? They are found fair in Britain, brown in Spain and Por tugal, copper coloured in Arabia and Egypt, and almost wholly black in Abyssinia, and at Cochin in India.
With regard to the Jews at Cochin, Dr Buchanan, in his Chriraiun Researches, furnishes sonic particulars which show, in a very remarkable degree, the effect both of climate and of long residence. There are two descriptions of Jews at Cochin, the one he denominates black, and the other white Jews, and concludes, evidently without any theory in his head respecting the sameness, or diversity of the human species, that the former owe their dark complexion to their long residence in the country, whilst the latter have not resided long enough to complete the dye. His words are, " It is only necessary to look at the countenance of the black Jews, to be satisfied, that their ancestors must have arrived in India many ages be fore the white Jews. Their Hindoo complexion, and their very imperfect resemblance to the European Jews, indicate that they have been detached from the parent stock in India, many ages before the Jews in the West." There is therefore every probability that these white Jews will one day become as black as their sable bre thren. This conjecture is in a great measure confirmed by the remark of Dr Smith, that the people of the Uni ted States, though sprung originally from many different nations of Europe, have now all an uniform cast of fea tures and complexion.