Between these highlands is a lowland which spreads out in each continent in three directions. In North America its greatest extent is in the plain which stretches between the Rocky Mountains and the Appalachians, lowest along the north and south axis where the Mississippi runs, and rising gently to east and west with a slope im perceptible to the eye, and yet so continuous that when it reaches the abruptly rising mountains on the west, the surface is already a mile high. Between the Laurentian shield of hard old rock on the one hand, and the Appa lachians and Cordillera on the other, are the narrower lowlands through which the St. Lawrence and the Mackenzie find their ways to the Atlantic and the Arctic. In South America the great lowland is that which lies on either side of the equator, drained by the Amazon and its tributaries, with a comparatively narrow opening eastwards between the plateaus of Guiana and Brazil. Southwards a plain extends with the Andes and the plateau of Brazil on the west and the east ; while northwards, between the north-eastward curve of the Andes and the plateau of Guiana, is a much smaller plain through which the Orinoco flows.
Several results follow from the way in which the extent of the climatic provinces is determined by this con figuration. The equatorial forests of the hot, wet Amazon plain cover a vast area, stretching almost across the continent, and running up the eastern slopes of the Andes. On the other hand, the desert of South America, shut in between the Andes and the sea, is of necessity very narrow. The region which may be said to correspond to the Sudan is the savanna land of the Orinoco, comparatively small in extent, and with a climate which differs from that of the African Sudan in several important particulars ; the same may be said of the savannas of the interior highlands of Brazil, which are in addition composed of hard old rock from which such water as does fall runs oil quickly.
In North America the most arid region is on the high land to the west of the southern portion of the Rocky Mountains. Such streams as flow westwards from these dry heights rim in deep narrow channels far below the normal level of the land, and in fact help to make it drier than it otherwise would be. South of this desert the whole land narrows, and the mountain borders approach each other in the great peak of Orizaba. The eastern mountain edges, drenched by the rains of the trade winds, are wet and densely forested, but the Mexican plateau between the mountains is comparatively dry, receiving in winter very little rain for some months. There is also a dry region, on which grass grows, on the high plains to the east of the Rocky Mountains ; this is what corresponds to the steppes of Asia, but obviously it is not comparable in extent, for to north and east the land was covered by forest, coniferous in the north, tem perate towards the Atlantic, and almost tropical along the Gulf of Mexico. In South America, the only region
which may be said to correspond to the steppes is the land which lies to the east of the Andes, in what is now the Argentine.
Thus the places corresponding to those on the Old World where under simple conditions men were induced or compelled to make some effort to life are, in the New World, largely lacking in those qualities which would make them nurseries of civilizations. There is no great river crossing a great desert, at one season bringing abundance of water for growth of crops and at another dwindling away so that vegetation becomes parched and dry. There is no land where at once it Is warm and life is in consequence comparatively easy, where there is a strong incentive to think ahead and save stores of food and other forms of natural wealth, and where there is a protection against the inroads of those who might seize the wealth which has been stored.
Even the steppelands are of slight extent, and the peoples characteristic of the steppes of the Old World are conspicuous by their absence; this is partly due to another lack which the New World suffers in contrast with the Old; none of the animals which feed on grass and have been domesticated in Europe, Asia and Africa, are natives of North or of South America. There were no camels, horses, asses, sheep or goats ; and, more important than all, cattle, representing one of the earliest forms of saved energy, were entirely absent before they were introduced from Europe. There was no beast of burden to save human energy from being expended in moving things from one place to another, there was no milk nor any of the foods made from milk. This statement perhaps requires a slight, but a very slight qualification. Bison, or buffaloes as they are often wrongly called, roamed the grasslands in countless herds, and there does not seem any very good reason why these might not have been domesticated. It is sometimes said that they are incapable of domestica tion. Whether this is so or not, the fact remains that they never were domesticated, and that these animals alone could have allowed of the existence of any hardy nomadic pastoral peoples who, while moving to in fluence inhabitants of widely separated areas on the borders of the steppelands, might yet have the staying power that comes from the possession of saved energy or capital. The nomad of the New World must perforce travel light; this may allow of speed of movement, but gives no great irresistible power. In the New World we need not expect to see great migrations of people sweeping all before them, like those we have already seen in the Old. Further, even the negro type of civiliza tion, as far as it was based on cattle, was quite im possible, for the bison did not exist in South America.