Many of the older geographers describe a chain of mountains, the Kong, running parallel with the coast of Guinea; but more modern authors, in their descriptions of the edge of the plateau, state that it approaches the coast only at intervals beyond the low delta of the Niger, as far as Cape Verd, and that the supposed Kong Mountains do not exist.
East of the Niger the country is merely hilly, interspersed here and there with very fertile, often swampy, plains. In the basin of Lake Tchad is a vast plain, formed of alluvial deposits. This plain is one of the largest upon the globe, and is noted for its great fertility.
The third section, or Great Desert, extends south nearly to the Senegal, the northern bend of the Niger, and Lake Tchad. Northward, it extends to the Atlas range in Morocco and Algeria. Towards Egypt it reaches nearly to the Mediterranean Sea.
The Sahara is not a vast plain of trackless sand, as we might suppose. The greater part of it, on the contrary, rises into great table-lands. Some of these table-lands contain groups of mountains, rising often to the height of more than six thousand feet. This height is almost equal to that of Mount Washington in New Hampshire, or Mount Katahdin in Maine. It is somewhat greater than that of Mount Marcy in New York, or Mount Mansfield in Vermont.
We must consider the Sahara, then, not a monotonous expanse of burning sand, but a region presenting great variety in its form and characteristics.
From south to north it has an average breadth of about one thousand miles. From the Atlantic Ocean to the western edge of the Nile valley its length is about two thousand miles.
Throughout the entire desert rain rarely falls. Indeed, over a great portion of it there is never a drop of rain. For this reason the land is dry and sterile.
In some portions of the desert there are vast tracts of shifting sand. Frequent and violent winds blow these sands high into the air, and travelers often find themselves suddenly overtaken by one of these sand-storms, to their great discomfort and danger.
Most of us have experienced the discomfort from a sudden cloud of dust and dirt, when the rude winds of March have full force. We can imagine, in a slight degree, the fury of one of these storms of blinding, burning sand.
We can picture the unfortunate bewildered traveler overtaken by one of these storms. Blinded, half-smothered, unable to battle with so unsuspected a foe, he sinks helplessly to the ground. The shifting sands heap themselves over his prostrate form. Alone, unknown, with naught to mark his resting place, he lies buried in the wastes of the Sahara.