height, and terminate some three hundred miles north of the Caspian, leaving a broad gateway from Siberia into Europe. Let us speak of this vast plain as the Great Lowland.
Southward the Great Lowland ends along the foot of a tableland, whose average elevation is about half a mile, with mountain ridges rising to a mile and a half. This tableland bears upon its broad back the three countries of Persia, Afghanistan, and Baluchistan; for convenience we may describe the whole of it as the Iranian Upland. The Heartland, in the sense of the region of Arctic and Continental drainage, includes most of the Great Lowland and most of the Iranian Upland; it extends therefore to the long, high, curving brink of the Persian Mountains, beyond which is the depression occupied by the Euphrates Valley and the Persian Gulf.
Now let us travel in imagination to the west of Africa. There, between the latitudes of the Canary and Cape Verde Islands, is a Desert Coast: it was the character of that coast, it will be remembered, which so long baffled the effort of the mediæval sailors to make the southward voyage round Africa. With a breadth of a thousand miles the Sahara spreads thence across the north of Africa from the Atlantic Ocean to the Valley of the Nile.
