Egypt may be said to owe its very existence as a habitable country to the presence of the Nile. The course of that magnificent river has now been traced to great lakes lying across the Equator, more than two thousand miles south of Alexandria in a direct line. After receiving its two Abyssinian branches, at Khartoum and at Berber in Nubia, it pours the broad, deep volume of its waters through a flat, alluvial valley for fifteen hundred miles without being increased by any other tributary, and finally discharges itself by two principal channels and several minor outlets into the sea.

This fruitfulness is consequent upon the periodic inundations of the river. Although there is little or no rain in Egypt, there are continuous and heavy rains at the sources of the Nile. These begin to fall in March, and being supplemented by the melting of the mountain snows in the following months, occasion a perceptible rise in the river about the end of June. From this period to the close of September, the rise increases with a regularity almost certain and constant, at a rate of four inches a day.