The hair is rarely wholly black, as when examined by reflected light it will also show a faint undercolor of red. This reddish tinge is very perceptible in some tribes, and especially in children. Generally straight and coarse, instances are not wanting where it is fine and silky, and even slightly wavy or curly. Although often compared to that of the Chinese, the resemblances are superficial, as when critically examined, “the hair of the American Indian differs in nearly every particular from that of the Mongolians of eastern Asia.”[41] The growth is thick and strong on the head, scanty on the body and on the face; but beards of respectable length are not wholly unknown.[42] The stature and muscular force vary. The Patagonians have long been celebrated as giants, although in fact there are not many of them over six feet tall. The average throughout the continent would probably be less than that of the European. But there are no instances of dwarfish size to compare with the Lapps, the Bushmen, or the Andaman Islanders. The hands and feet are uniformly smaller than those of Europeans of the same height. The arms are longer in proportion to the other members than in the European, but not so much as in the African race. This is held to be one of the anatomical evidences of inferiority. On the whole, the race is singularly uniform in its physical traits, and individuals taken from any part of the continent could easily be mistaken for inhabitants of numerous other parts. This uniformity finds one of its explanations in the geographical features of the continent, which are such as to favor migrations in longitude, and thus prevent the diversity which special conditions in latitude tend to produce. The trend of the mountain chains and the flow of the great rivers in both South and North America generally follow the course of the great circles, and the migrations of native nations were directed by these geographic features. Nor has the face of the land undergone any serious alteration since man first occupied it. Doubtless in his early days the Laramie sea still covered the extensive depression in that part of our country, and it is possible that a subsidence of several hundred feet altered the present Isthmus of Panama into a chain of islands; but in other respects the continent between the fortieth parallels north and south has remained substantially the same since the close of the Tertiary Epoch.