As for the Hamadah, we know that near Sokna the plateau breaks up and forms what are called the Jebel-es-Soudy, or Black Mountains, a most picturesque group of cliffs; and again on the route to Egypt from Mourzuk, six days’ journey south-east from Sokna, it also breaks into huge cliffs, and bears the name of El-Harouj.  These mountain buttresses are either the bounds of the Hamadah, or masses of rock where it breaks into hills, forming ravines or valleys.  But, in fact, how far the Hamadah extends between Ghadamez on the west and Augila on the east is not yet properly ascertained.  It seems to be like a broad belt intercepting the progress of commerce, civilisation, and conquest, from the shores of the Mediterranean to Central Africa.  The kingdom of Fezzan, however, advances like a promontory beyond it; and then on every side stretches the desert ocean with its innumerable oases or islands, which, from being once mere fluctuating names, as it were, on a guess map, are now by degrees dropping one by one into their right places.

On the breaking-up of the plateau we observed its geological structure to consist of three principal strata:  first, a covering or upper crust, limestone with flints and red earth; then masses of marl; and then sandstone, lumps and masses of which were blackened by the contact of the air with the iron they contain.  Under the sandstone was likewise a bed of yellow clay, with a mixture of gypsum.

The face of the cliffs of the plateau was blackened as with the smoke of a huge furnace, which gave a majestic and yet gloomy appearance to the scene as we descended the pass towards the valley of El-Hasee.  We found the plain strewed with great masses of dark sandstone, seeming to have been detached by some convulsion from the rocky walls, which now rose in apparently interminable grandeur behind us.  We glanced back in awe, and yet in some triumph, towards the iron-bound desert we had thus safely traversed; but our eyes soon turned from so bleak a prospect, when we beheld, dotting the sandy wady, clumps of the wild palm, green copses, and the majestic ethel-tree.

It was about two in the afternoon when we reached the camping-ground, all our people shouting, “Be-Selameh el Hamadah!” Farewell to the Hamadah!  I cried out the same words in a joyful voice; for, although now that the dangers of the plateau were overcome they seemed diminished in my eyes, yet I felt that we had escaped from a most trying march with wonderful good fortune.  It is difficult to convey an idea of the horror and desolation of so vast a tract of waterless and uninhabited country.  They alone who have breathed the sharp air of its blank nakedness can appreciate it, or understand how any accidental delay, sickness, the bursting of the water-skins, the straying of the camels, might produce incalculable sufferings, and even death. “Be-Selameh el Hamadah!” then, with all my heart. “Be-Selameh! be-Selameh!” again rings through the caravan,