Page:Popular Science Monthly Volume 17.djvu/17

Rh that the fairest natives are found. The testimonies of the early explorers, which have been collected and arranged by Mr. Bancroft, of San Francisco, in his valuable work on the Indians of the Pacific coast, leave no doubt that, before there was any intermixture of European blood in this region, the complexion of the inhabitants was not very different from that of southern Europeans, that their skins transmitted a blush, and that fair and brown hair, ruddy cheeks, and light eyes were not uncommon among them.

Perhaps the best example of a perpetually humid tropical climate is afforded by the valley of the Amazons. In consequence, nearly the whole of the vast region drained by this stream is, like some parts of India and some of the East Indian islands, covered with a dense unbroken forest. Though heated by an equatorial sun, its natives are, not only not black, but, as has already been remarked, lighter-complexioned than those of the Peruvian Cordilleras.

Examples of perpetually dry tropical climates are furnished by the Nubian Desert and the southern part of the Sahara. These countries, together with southern Arabia, enjoy the hottest mean summer temperature known. The inhabitants, whether belonging to the Semitic, the Hamitic, or the negro race, are alike black. The Nubian Arabs are said to be as black as the blackest negroes.

The part of Africa south of the Great Desert will exemplify the case of a tropical climate with a dry season. This immense region consists essentially of a strip of low coast-land, and an immense level central depressed surface, with a more or less elevated rim inclosing it. The inhabitants of the coast and the central depression are very black, those of the rim lighter in color. Dr. Livingstone attributes this difference to the greater humidity of the lower regions. But it is obvious, from theoretical considerations, that the rim must be more humid than any other part of the continent. During the dry season the sea-breezes, when they strike the coast, will be raised in temperature, and consequently deposit no moisture, until cooled by being forced upward when they come against some elevated land. The meteorological observations made in Africa support this view. Along the coast there is everywhere one pronounced dry season, and in some places there are two. In Sierra Leone (8° N. L.), it lasts from November to May; at the mouth of the Gaboon (0°), from May to September. In Zanzibar (6° S. L.) there are eight rainless months; in Natal (25°-30° S. L.) seven. The central depressed regions exhibit similar phenomena. At Gondokoro (5° N. L.) there are five, at Ujiji (5° S. L.) there are eight rainless months. On the contrary, in the Usagara Mountains (6° S. L.), which are west of Zanzibar, and in the elevated equatorial region about the Victoria Nyanza, rain falls every month of the year.

It was long ago remarked that the negro perspires less than the white. Pruner Bey has established by actual measurement that both