Indeed, the width of productive Egypt is determined by the lateral extent of this overflow. For the last 1,500 miles of its course the Nile receives no tributary. It plows its way through regions of desert which, but for the Nile itself, are unbroken. At six points, beginning at Khartum and ending at Assuan, the river makes its way over granite ridges, through which it has never succeeded in cutting a smooth channel. These are called the Cataracts. As civilized man discovered these from the north, that at Assuan is known as the First Cataract, and that at Khartum as the Sixth. The calendar of ancient Egypt was shaped in part by the Nile. The year was divided into three seasons of four months each. Beginning with the rise of the water about July 19th, there was the season of the inundation, which was followed by four months of winter and four months of summer. [Illustration: MAP OF EGYPT.] In late geologic time all Egypt north of Cairo was a bay of the Mediterranean. In the course of the centuries the sea has been driven out by deposits of detritus brought down by the Nile. As the mud was deposited in this level region, the water continued to make its way through it here and there. Several mouths were kept open, and thus the Delta was formed. This Delta is called Lower Egypt. Upper Egypt extends from Cairo to the First Cataract; Nubia, from the First Cataract to the Sixth. =2. The Preservation of Antiquities.=--Rain in Egypt is very, very rare. One might almost say that it never rains. The country lies in a latitude so far south that frost is rarely known. These two conditions have united to preserve the ruins of many ancient buildings in both Egypt and Nubia in a state of perfection which is rare in other countries. It was the custom of the ancient Egyptians to bury their dead in the dry land beyond the reach of the Nile’s overflow. Like many other peoples, they placed in the tombs of their dead many objects used by the departed in life. Further, their peculiar beliefs concerning immortality led them to mummify the bodies of the departed; _i. e._, they fortified them against decay. Thus archæological objects have been preserved in Egypt in an abundance and a perfection without parallel. So many of these are massive temples of stone, which, through all the ages, have stood unconcealed as silent witnesses of a past greatness, that from Cairo to the First Cataract Egypt is one great archæological museum. =3. Egyptian Discoveries.=--Although many Egyptian antiquities have always been visible, they attracted little attention until modern times. Egyptian temple walls are covered with hieroglyphic writing, but the art of reading it had long been lost. Coptic, a language descended from the ancient Egyptian, was still preserved as the sacred language of the Egyptian Church, as Latin is the ecclesiastical language of Roman Catholics, but no one realized that Coptic was simply late Egyptian.