The most westerly of the three valleys to which we have alluded is only a slightdepression of the surface of the land marked by a line of oases. The depression isnot sufficient to admit the waters of the Mediterranean, nor are there any rainsover any portion of the valley which it forms sufficient to make it the bed of astream. Springs issue, however, here and there, in several places, from the ground, and, percolating through the sands along the valley, give fertility to little dells, longand narrow, which, by the contrast that they form with the surrounding desolation, seem to the traveler to possess the verdure and beauty of Paradise. There is a lineof these oases extending along this westerly depression, and some of them are ofconsiderable extent. The oasis of Siweh, on which stood the far-famed temple ofJupiter Ammon, was many miles in extent, and was said to have contained inancient times a population of eight thousand souls. Thus, while the most easterly ofthe three valleys which we have named was sunk so low as to admit the ocean toflow freely into it, the most westerly was so slightly depressed that it gained only acircumscribed and limited fertility through the springs, which, in the lowestportions of it, oozed from the ground. The third valley-the central one-remainsnow to be described.The reader will observe, by referring once more to the map, that south of the greatrainless region of which we are speaking, there lie groups and ranges of mountainsin Abyssinia, called the Mountains of the Moon. These mountains are near theequator, and the relation which they sustain to the surrounding seas, and tocurrents of wind which blow in that quarter of the world, is such, that they bringdown from the atmosphere, especially in certain seasons of the year, vast andcontinual torrents of rain. The water which thus falls drenches the mountain sidesand deluges the valleys. There is a great portion of it which can not flow to thesouthward or eastward toward the sea, as the whole country consists, in thosedirections, of continuous tracts of elevated land. The rush of water thus turns tothe northward, and, pressing on across the desert through the great central valleywhich we have referred to above, it finds an outlet, at last, in the Mediterranean, ata point two thousand miles distant from the place where the immense condenserdrew it from the skies. The river thus created is the Nile. It is formed, in a word, bythe surplus waters of a district inundated with rains, in their progress across arainless desert, seeking the se