Egypt is almost rainless and the Nile gives both land and people their food and drink. I have already described some of the wonders of the stream and what it does for Egypt. It rises in Lake Victoria, in Central Africa, and drops a distance greater than the altitude of the highest of the Alleghanies before it flows into the Mediterranean Sea. In the upper part of its course it is known as the White Nile, and this should be called the main stream of the river. At Khartum, thirteen hundred and fifty miles from the Mediterranean, the Blue Nile, which rises in the Abyssinian Mountains, comes in, while about one hundred and forty miles farther north the Atbara, or Black Nile, which is also from Abyssinia, joins the main stream. From the mouth of the Atbara to the sea there is not a tributary of any kind connected with the river. It ploughs its way through the desert valley, in which it has built up Egypt, narrowing and widening, until a few miles below Cairo, where it divides into two great branches and flows off into the sea. The volume of the Nile is enormous. At flood times, a billion tons of water go by at Aswan every day. The river then rises twenty-five feet at Cairo, thirty-eight feet at Old Thebes, and almost fifty feet at the first cataract, where I now am. There is so much water that no dam could hold it, hence all of these great works had to be made so that the water can be let in and out and allowed to pass through at will. It is at flood time that the Nile valley gets its rich feed of Abyssinian mud. This is brought down in part by the Blue Nile, but more abundantly by the Atbara, or Black Nile. It is carried by the inundation all over Egypt and by means of irrigation conducted to nearly every farm. After the floods subside the muddy waters grow clear again. The Blue Nile and the Black Nile become almost dry, and the white water of the main, or Victoria Nile, is about all that Egypt has. It is this white water that is stored up by the Aswan Dam, and it feeds the country in much the same way as our irrigation canals do, with water only and not with a thick mixture of water and mud as in the times of the overflow. For thousands of years these rivers have been pouring down through this Nile valley; but whenever the rains have been scanty in the highlands of Abyssinia and in Central Africa the main stream has not been high enough to reach the whole country. Most of the lands could be inundated only once a year, and if the Nile was especially low some could have no water at all. By the present system Egypt has water all the year round, and enough to make it produce two or three crops every twelve months.