The whole tract is nearly level, and so little elevated above the sea, that, at the distance of many hundred miles in the interior, the land rises only to the height of a few hundred feet above the surface of the Mediterranean; whereas in New Grenada, at less than one hundred miles from the sea, the chain of the Andes rises to elevations of from ten to fifteen thousand feet.

Such an ascent as that of a few hundred feet in hundreds of miles would be wholly imperceptible to any ordinary mode of observation; and the great rainless region, accordingly, of Africa and Asia is, as it appears to the traveler, one vast plain, a thousand miles wide and five thousand miles long, with only one considerable interruption to the dead monotony which reigns, with that exception, every where over the immense expanse of silence and solitude.

The single interval of fruitfulness and life is the valley of the Nile.
There are, however, in fact, three interruptions to the continuity of this plain, though only one of them constitutes any considerable interruption to its barrenness.

They are all of them valleys, extending from north to south, and lying side by side.

The most easterly of these valleys is so deep that the waters of the ocean flow into it from the south, forming a long and narrow inlet called the Red Sea.