With the sixth dynasty a new epoch begins. The most powerful monarch in this series is _Pepi_. He levied armies, conquered the negroes of Nubia, and waged war against the nomads of the eastern desert. The interval from the sixth to the tenth dynasty was marked by usurpations and insurrections. The district governors sought to make themselves independent. Monarchs rose and fell. Syrian invaders appear to have seized the occasion to attack the country. _Heliopolis_, with _Tum_ for its sun-god, is the center of the new symbolical lore of the priesthood. Power is transferred to _Thebes_, and _Ammon_ becomes the embodiment of the monotheistic conception, the supreme deity. The Theban ruling-house gradually extended its supremacy over the land. The kings of the twelfth dynasty have left their inscriptions everywhere, and of several of them gigantic portrait-statues remain. _Amenemhat I._ and his successors are prosperous sovereigns. They carry on a lively intercourse of trade with the small states of Syria, reaching possibly to Babylon. Under the twelfth dynasty, the valley of the upper Nile was conquered. _Usurtasen III._, in after times, was revered as the subduer of the Nubian land. By monarchs of this epoch, vast structures, like the temple of Ammon at Thebes and the temple of the Sun at Heliopolis, were erected. _Amenemhat III._ built the immense artificial reservoir, Lake Moeris, to receive and dispense the waters of the Nile. Under the twelfth dynasty is the blossoming period of literature. The carving of hieroglyphics and the execution of the details of art reach their perfection. It is the culminating point of Egyptian culture. THE MIDDLE EMPIRE (FROM ABOUT 2100 TO 1600 B.C.).--The season of prosperity under the twelfth dynasty was followed by anarchy and the downfall of the Theban rule. According to _Manetho_, it was under a king named _Timaos_ that a horde of invaders--the _Hyksos_, or _"shepherds"_--came in from the north, devastated the country, and made themselves its rulers. They were probably of Semitic descent, but nothing more is known as to their origin. In connection with them, Semitic, and in particular Canaanite, elements penetrated into Egypt, and left their traces in its language. The residence of their kings was _Tanis_, on the eastern Delta, a splendid city, which they still more adorned. They conquered Memphis, but their power was not permanently established in Lower Egypt. The duration of their control was a number of centuries,--how many can only be conjectured. It is believed by some scholars that either _Apepi,_ or _Nub_, kings of the Hyksos line, was the sovereign who made _Joseph_ his prime minister, and invited his family to settle in the land of Goshen. The elevation of a foreigner and a Semite to an exalted office is thought to be less improbable in connection with a Semitic dynasty.