3 o8 THE POPULAR SCIENCE MONTHLY. 



the polar regions have often seen like results produced by the glare 

 of the snow. When the impression of light on the eye is sudden and 

 overpowering, the retina suffers most. If it is less powerful, but longer 

 continued, the humors of the eye are affected. The phenomenon called 

 sunstroke results from the action of light, and not, as is often supposed, 

 from excessively high temperature. It sometimes occurs in the mod- 

 erately warm season of spring ; or a very intense artificial light, and 

 particularly the electric light, may occasion it. The violet and 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 dis- 

 order is a true inflammation. 



The action of light on the human skin is manifest. It browns and 

 tans the teguments, by calling out the production 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 complexion in 

 a measure perceptibly related to the intensity of solar light. In Eu- 

 rope 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 observa- 

 ble in others. The Scytho-Arabic race has but half its representatives 

 in Europe and Central Asia, while the remainder passes down to the 

 Indian Ocean, continuing to show the gradual rising heat of climate 

 by deepening brown complexions. The Himalayan Hindoos are al- 

 most white ; those of the Deccan, of Coromandel, Malabar, 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 signi- 

 ficant. The men are always depicted of a reddish brown ; they lived 

 in the open air, wdiile the women, kept shut up, have a pale-yellow 

 complexion. Barrow asserts that the Mantchoo Tartars have grown 

 whiter during their abode in China. Iiemusat, Pallas, and Gutzlaff, 

 speak of the Chinese women as remarkable for a European fairness. 

 The Jewesses of Cairo or Syria, always hidden under veils or in their 

 houses, have a pallid, dead color. In the yellow races of the Sumatra 

 Sound and the Maldives, the women, always covered up, are pale like 

 wax. We know, too, that the Esquimaux bleach during their long 

 winter. These phenomena, no doubt, are the results of several infiu 



