[ 1 3 ° ] 
of the lame Nation, as Mr. Cowper informs us [a) : 
And every one may perceive, that the Skins of dif- 
ferent Perlons are of different ThicknelTes and Denfi- 
ties; and much more thofe of different Nations and 
Complexions : But when the Diverfiry of our Colours 
proceed from the different Tranfmiffions of the Rays 
of Light, from one and the fame coloured Bodies, 
fuch different Thickneffes of our Skins will only' 
make our Colours vary from one another ftcundum 
majus vet minus , only in the Degree of one and the 
fame Colour; by which alone will Negroes, Indians , 
and white People, or each of a Sort, differ from one 
another in Colour ; and, confequently, their different 
Colours will proceed from Cautes more uniform and 
alike, agreeable to the exaCt Symmetry of Nature in 
the Variations of other Things of the fame Kind ; lo 
that, however different, and oppofite to one another, 
thefe two Colours of Black and White may appear 
to be to the Unskilful, yet they will be found to dif- 
fer from one another only in Degree; fince Whitenefs 
proceeds from a Reflexion orTranfmiffion of the Rays 
of all Colours; but Blacknefs is brought on, by an 
Extinction or Suffocation of thofe fame mixed Rays, 
which, probably, in the black Bodies, are reflected or 
tranfmitted in fbme fmall Quantity, as they are in larger 
or fmaller Quantities, in proportion to the Whitenefsof 
Bodies [b ) : And hence it is, that one of thefe Colours is 
moreeafily changed into the other, than to any other 
Colour ; and where any Body lofes its white Colour, it 
of courfe turns black, without any other Caufe con- 
curring, but a bare Lofs of its W hitenefs (r). From 
(a) Anatom. Tab. IV. (b) Newton Opt ubique. (e) Idem ib. 
whence 
