[ 1*6 ] 
neceffe & multi Radii inter cipiantur^ refiinguantur , 
&■ inter ip fa intercidant ( a ). 
Two Properties are generally affigned to all black 
Bodies, to be opaque and porous : Now the Skin is 
well known to be porous; and we have fhewn, that 
the Skins of Negroes are opaque ; to thefe we may 
add a third neceflary Property of black Bodies, m. 
the Minutenefs of their Particles: For, as Sir Ifaac 
Newton (hews } Ad Nigrorem exhihendum y Rarticula 
adlouc minor es ejfe debent omnibus illisy qua Colores 
cujufcunque modi exhibent : Nam Rarticula omnes 
majufcula plus ref e blunt Luminis , quam tit nigra 
pojfnt videri [b) ; which Smallncfs of Particles we 
have above demonftrated in the Skin (Prop. V.) ; 
and it is probable, that, in Negroes, the Particles 
of the Skin between the Pores are ffnallcr than in 
Whites ; as the Pores themfclves are fo : From which 
Smallnefs of its Particles, the Skins of Negroes can- 
not reflect the Rays of Light ; another Caufe of 
their being black. 
So that, from the Whole, we may conclude, that 
the proximate Caufe of the Colour of Negroes is 
threefold ; m. the Opacity of their Skins, proceed- 
ing from the Thicknefs and Denfity of ther Texture, 
which obftruds the Tranfmiflion of the Rays of 
Light, from the white and red Parts below them; 
together with their greater refradive Power, which 
abforbs thofe Rays; and the Smallnefs of the Parti- 
cles of their Skins, which hinder them to refled any 
Light. E. I. 
(a) Newton Opt. Prop. V.II. 
{b) Ibid. Prop. VII. 
Scholium. 
