L 120 ] 
thematically exad or no ; all that I would endeavour 
to prove, is, that the Parts into which the Cuticle 
is divided, are left, in fome Proportion, than the 
Particles of Bodies on which their Colours depend.. 
Proposition' VI. Problem. 
To determine and explain the proximate Caufe of the 
Colour of Negroes, Indians, white People , &c. 
from the foregoing Proportions. 
We have fhewn above Prop. I. that the Colour 
of white People depends upon the Colour which 
the Epidermis tranfmits, and not on what it refleds : 
This Pellucidity of Bodies proceeds from the Num- 
ber of Intcrftices between the Particles which com- 
pote them, and the extreme Smallncfs of thofe Par- 
ticles ; for, in order to render a Body of any Colour, 
or fit to refled the Rays of Light, its Particles, and 
the Intervals between them, ought not to be lefs 
than a certain Magnitude ( a ) el fie they become in- 
capable of making any Reflexions, from their com- 
mon Surfaces, i. e. of appearing coloured : But, by 
Prop. V. the Cuticle is divided into Parts, and 
Pores or Intervals between thefe Particles, far lefs 
than thofe on which the Colours of Bodies depend ; 
that is, too fimall to relied any Rays of Light from 
their common Surfaces, or to appear coloured from 
l'uch reflcded Rays: But, as fiuch porous Bodies are 
always tranfparent, fo the Epidermis is tranfiparent 
enough, to fiiew any Colour rcfleded from the Parts 
(a) Newton Opt. Prop. IV. 
below 
