58 PHILOSOPHICAL TRANSACTIONS. [aNNO 1744. 



of white people are. 3. Infant negroes, whose skins differ from adults only in 

 the thinness and rarity of their texture, look whitish, in comparison to adult 

 negroes, but grow black, as their skins turn thicker and denser. These infant 

 negroes, labouring under an icterus, look of a yellow colour, all over their 

 body, which the adult do not, except in the eyes; a plain proof, that the colour 

 of the skin proceeds from the colour which is transmitted through it; and that 

 the skins of adult negroes transmit no colour of any sort. 4. But that the 

 thickness of the corpus reticulare, the part which appears black in negroes, by 

 prop. 3, may and does make it black, Malpighi gives an instance in the said 

 part, in the tongue of a beef, in which it appears black, on the middle of the 

 tongue, where it is thick ; but is white on the edges and cheeks, where it is very 

 thin. As for the manner in which this blackness or opacity is occasioned, by a 

 thick or dense skin, it will appear from what has been said about the skins of 

 tawny people ; and it is very easy to conceive how the rays of light are intercepted, 

 in passing through the thick and dense skins of negroes, which easily pervade 

 the thin and rare cuticles of whites. 



But, as the skins of negroes are of a denser texture than those of whites, 

 they will be more apt to refract the rays of light; for the denser the body, the 

 greater the power of refracting; and the greater the refraction of any body is, 

 the more apt it will be to absorb the rays of light; which is another property of 

 opaque bodies, by which they become black. 



So that, from the whole, we may conclude, that the proximate cause of the 

 colour of negroes is threefold, viz. the opacity of their skins, proceeding from 

 the thickness and density of their texture, which obstructs the transmission of 

 the rays of light, from the white and red parts below them ; together with their 

 greater refractive power, which absorbs those rays, and the smallness of the par- 

 ticles of their skins, which hinder them from reflecting any light. 



Hence we may justly infer, 1 . That there is not so great, unnatural, and unac- 

 countable a difference between negroes and white people, on account of their 

 colours, as to make it impossible for both ever to have been descended from the 

 same stock, as some people, unskilled in the doctrine of light and colours, are 

 very apt too positively to affirm and believe, contrary to the doctrine of the sacred 

 pages. 1. That the epidermis, besides its other uses, tends to preserve the yni- 

 formity of the colours of people throughout the world. 



Prop. vii. — The influence of the sun, in hot countries, and the ways of life of 

 the inhabitants in them, are the remote causes of the colour of negroes, Indians, 

 iSc. ^nd the ways of living, in use among most nations of white people, make 

 their colours whiter than they were originally, or would be naturally. — As for 

 what relates to the remote causes of the colours of negroes, it has been generally 

 Kupposal, though not universally believed, that the power of the sun in hot 



