=1. The Land.=--Egypt is in many ways unique among the countries of the world. One of these unique features is its form. If we omit the Delta, it has but one dimension,--length. From Cairo to the First Cataract is a distance of 583 miles, while the breadth of the valley, including the barren lands on each side of it, varies from 12½ to 31 miles. If we include Nubia to the Fourth Cataract, which the Egyptians ultimately conquered, the length is much greater, being about 1,100 miles. In Nubia the banks are much more precipitous, the valley varying from 5 to 9½ miles. The verdant portion is, however, often not more than a mile in width. This land is flanked on each side by extensive barren deserts on which there is almost no rainfall. Egypt itself would be a part of this desert, were it not for the overflow of the Nile. This overflow is caused by the peculiar formation of this marvelous river. The upper part of the Nile consists of two main branches, called, respectively, the White and the Blue Nile. The White Nile rises 3 degrees south of the equator, some 4,000 miles south of the Mediterranean, to the south of Lake Victoria Nyanza. This region is watered by tropical rains, which fall almost daily. This steady water supply gives to the Nile its constant volume. At Khartum, 1,350 miles from the Mediterranean in a direct line, and 1,650 miles as the river winds, the White Nile is joined by the Blue Nile. This branch of the river drains a large part of Abyssinia, an upland and mountainous region which has a dry and a rainy season. In the dry season this stream dwindles almost to nothing; in the rainy season it is a turbid mountain torrent, which rushes impetuously onward, laden with loose soil from all the land which it drains. For this reason it is called the Blue, _i. e._, the Dark or Turbid, Nile. At a distance of 140 miles north of the union of the two Niles the river receives its only other tributary, the Atbara, which also flows in from the eastern side. The Atbara, like the Blue Nile, is an insignificant stream except in the rainy season, when it is a torrent. It is the variation of the water supply from the Blue Nile and Atbara which causes the overflow of the river in Egypt. At the beginning of June the river begins slowly to swell; between the 15th and the 20th of July the increase becomes very rapid; toward the end of September the water ceases to rise and remains at the same height for twenty to thirty days. In October it rises again, attaining its greatest height. It then decreases, and in January, February, and March the fields gradually dry off. This overflow prepares the soil of Egypt for cultivation, first by softening it and then by fertilizing it. It was easy, under these conditions, to develop agriculture there.