There was a certain unity in Egyptian worships, but in various localities the chief deities bore different names, and were regarded under varying aspects. The worship of some of these chief deities, however, became general, if not universal, at a very early period; _e.g._ that of Osiris, Isis, and Horus, the triad of Abydos; that of Ra and Turn,[17] chief gods of On, and that of Ptah, the centre of which was Memphis. The Thebaid—_i.e._ the district surrounding Thebes—had its own local divinities also. Khem, ‘Lord of the mountain,’ was adored at Koptos; Amen (worshipped in connection with Mut, the ‘Divine Mother,’ and Khons) was the chief god of Thebes. He was destined to become, under the name of Amen-Ra, the chief amongst Egyptian gods at a later day. The name of the first sovereign of the twelfth dynasty, Amenemhat (‘Amen the leader’), bespeaks its southern origin. This great monarch followed up the successes of the Mentuhoteps, and finally re-united Egypt under one sceptre, although at the cost of many years of severe conflict. Then he had to drive back the Kushites, who had encroached on the south, and the Libyans and the Amu, who troubled the northern borders; and after he had restored the ancient boundaries there was still need of perpetual vigilance upon the frontiers. On the north-east, where lay the greatest danger, he erected fortresses and built a strong wall of defence. But although Amenemhat I. had been able to restore the ancient boundaries of Egypt, and all the country was subject, nominally, to his sway, it is certain that the kinglets and chieftains whom he had reduced bore him but little affection, and yielded only a sullen and constrained obedience; in fact there is evidence of a hatred so vindictive that it did not scruple to resort even to the dagger of midnight assassination. But King Amenemhat did not rest content with the supremacy he had won; he strove, and not without success in the end, to win the goodwill and affection of the people, and he bequeathed to his successors a legacy of peace and prosperity that lasted for many generations. In the ‘Instructions’ which he left for his son Usertesen (whom he had associated with him on the throne), we may see both the high ideal this great and wise sovereign had formed of his own duties, and also form some idea of the perils and anxieties amidst which he strove to perform them. ‘Now thou art king,’ he says to his son; ‘strive to excel those who have gone before thee. Keep peace between thy people and thyself, lest they should be afraid of thee. Go amongst them, keep not thyself aloof; do not let it be only great lords and nobles whom thou takest to thy heart as brothers; nevertheless, let none come near thee whose friendship thou hast not proved.