The Atbara, or “Black Nile,” was simply a vast wady or furrow, thirty feet deep and 400 yards to half a mile across, plowed through the heart of the desert, its edges marked by a thin growth of leafless mimosas and dome palms. The only trace of water was here and there a rush-fringed pool which the impetuous torrent had hollowed out in the sudden bends in the river’s course, and where disported themselves hippopotami, crocodiles, and immense turtles, that had long ago adjusted their relations on a friendly footing on the discovery that none of them could do harm to the others. On the 23 of June, the simoom was blowing with overpowering force; the heat was furnace-like, and the tents of travellers were covered with several inches of drifted sand. Above, in the Abyssinian mountains, however, the lightnings were playing and the rains were falling as if the windows of heaven had been opened. The monsoon had set in; the rising streams were choking their narrow channels in their frantic rush to the lowlands, and were tearing away huge masses of the rich dark soil, to be spread a month hence over the flat plains of Egypt. The party encamped on the Atbara heard through the night a sound as if of distant thunder; but it was “the roar of the approaching water.” Wonder of the desert! Yesterday there was a barren sheet of glaring sand with a fringe of withered bush and tree. All nature was most poor. No bush could boast a leaf. No tree could throw a shade. In one night there was a mysterious change——wonders of the mighty Nile! An army of waters was hastening to the wasted river. There was no drop of rain, no thunder cloud on the horizon to give hope. All had been dry and sultry. Dust and desolation yesterday; to-day a magnificent stream five hundred yards wide and twenty feet deep, dashing through a dreary desert. Bamboos, reeds, floating matter of all kinds, hurry along the turbid waters. Where are all the crowded inhabitants of the pools? Their prison-doors are open, the prisoners are released, and all are rejoicing in the deep sounding and rapid waters of the Atbara. Here is the clue to one part of the Nile mystery——its great annual inundations, source of fertilizing soil and slime. The Blue Nile, further on, and with its sources in the same Abyssinian fastnesses, contributes like the Atbara, though in a secondary degree, to the annual Nile flood and to Egypt’s fertility, with this difference, that it flows all the year round. At Kartoum, as already seen, we reach the junction of the White and Blue Nile, the frontier of two strongly contrasted physical regions, and the dividing line between the nomadic barbarism of the north and the settled barbarism of the south. The secret that has still to be unveiled is the source of that unfailing flow of water which perpetually resists the influences of absorption, evaporation and irrigation, and carries a life giving stream through the heart of Egypt at all seasons of the year.