If the surplus of water upon the Abyssinian mountains had been constant and uniform, the stream, in its passage across the desert, would have communicated very little fertility to the barren sands which it traversed. The immediate banks of the river would have, perhaps, been fringed with verdure, but the influence of the irrigation would have extended no further than the water itself could have reached, by percolation through the sand. But the flow of the water is not thus uniform and steady. In a certain season of the year the rains are incessant, and they descend with such abundance and profusion as almost to inundate the districts where they fall. Immense torrents stream down the mountain sides; the valleys are deluged; plains turn into morasses, and morasses into lakes. In a word, the country becomes half submerged, and the accumulated mass of waters would rush with great force and violence down the central valley of the desert, which forms their only outlet, if the passage were narrow, and if it made any considerable descent in its course to the sea. It is, however, not narrow, and the descent is very small. The depression in the surface of the desert, through which the water flows, is from five to ten miles wide, and, though it is nearly two thousand miles from the rainy district across the desert to the sea, the country for the whole distance is almost level. There is only sufficient descent, especially for the last thousand miles, to determine a very gentle current to the northward in the waters of the stream. Under these circumstances, the immense quantity of water which falls in the rainy district in these inundating tropical showers, expands over the whole valley, and forms for a time an immense lake, extending in length across the whole breadth of the desert. This lake is, of course, from five to ten miles wide, and a thousand miles long. The water in it is shallow and turbid, and it has a gentle current toward the north. The rains, at length, in a great measure cease; but it requires some months for the water to run off and leave the valley dry. As soon as it is gone, there springs up from the whole surface of the ground which has been thus submerged a most rank and luxuriant vegetation.