124 NATURE AND LIFE. 
tric light, may occasion it. The violet and the ultra-violet 
parts of the sunbeam seem to be the cause of this action, 
for screens of uranium glass, that absorb these portions, 
protect the eyes of experimenters occupied in studying the 
electric light. This disorder is a true inflammation. 
The action of light on the human skin is manifest. It 
browns and tans the teguments, by stimulating the produc- 
tion of the coloring-matters they contain. The parts of 
the body usually bare, as the skin of the face and hands, 
are darker than others. In the same region, country-people 
are more tanned than town residents. In latitudes not far 
apart, the inhabitants of the same country vary in com- 
plexion in a measure perceptibly related to the intensity 
of solar light. In Europe three varieties of color in the 
skin are distinctly marked: olive-brown, with black hair, 
beard, and eyes; chestnut, with tawny beard and bluish 
eyes; blond, with fair, light beard and sky-blue eyes. 
White skins show more readily alterations occasioned by 
light and heat; but, though less striking, facts of variation 
in color are observable in others. The Seytho-Arabic race 
has but half its representatives in Europe and Central Asia, 
while the remainder passes down to the Indian Ocean, con- 
tinuing to show the gradual rising heat of climate by deep- 
ening brown complexions. The Himalayan Hindoos are 
almost white; those of the Deccan, of Coromandel, Mala- 
bar, and Ceylon, are darker than some negro tribes. The 
Arabs, olive and almost fair in Armenia and Syria, are 
deep-brown in Yemen and Muscat. The Egyptians, as we 
go from the mouths of the Nile up-stream toward its source, 
present an ascending chromatic scale, from white to black, 
and the same is true of the Tuariks on the southern side of 
Mount Atlas, who are only light-olive, while their brethren: 
in the interior of Africa are black. The ancient monuments 
of Egypt show us a fact equally significant. The men are 
always depicted of a reddish brown; they lived in the open 
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