[ '34 ] 
3. By a new Accretion of many new Membranes, 
which render it thick and opaque. For the Sun- 
beams a£t as a vibrating Force, or external FriCtion, 
upon the Skin, which derives frefh Supplies of Juices 
to it 5 by which new Membranes, or Lamellae , are 
formed, in the fame manner as the Epidermis is 
renewed when abraded, which is very foon and eafily 
done. This is the Senfe of a very great Philofopherj 
Calor fobs homines quibufdam in regionibns nigri- 
cante colore tingit , at in Ethiopia, Guinea, &c. 
Non ejfe illud ignis ejfeEium oflendunt vitrarii, conti- 
nuo ad ignem occupati. Ratio , fortaffe, quod ignes 
in fanguinem <& Jpiritus agat lit exhalent , hominef- 
que Jic reddet pal lidos & fubfufeos : benignior autem 
foils calor fanguinem duntaxat in corporis extimas 
partes prolicit , concoquitque eum potius quam eli - 
quat (a). Which Derivation and (lonco&ion of the 
Humours on the Surface of the Body muft occafion 
a Thicknels of their Skins, as well as of their Lips, 
and other Mufcles, efpecially of their Face. 
4. By increafing thofe Parts or Principles, in the 
Compofition of the Epidermis, which have the greardf 
refractive Powers. As the terreftrial, and fixed (aline ; 
but, efpecially, the tenacious fulphureous, which re- 
fraCt and abforb Light more ftrongly than any other 
Subltances {d) ; whilft the more traniparent and pel- 
lucid Principles, as the aqueous, lpirituous, and vola- 
tile inline, are evaporated by the Hear, which cautes 
the other more fixed Principles to be accumulated in 
’a) Bacon Hip. Natur. Cent. IV. 399. (b) Newton Opt, 
Prop. X. 
greater 
