But when at length this country had been drained by the canals and dikes which Sesostris constructed, population was introduced there, and wars arose which proved fatal to the power of Thebes.

Commerce then took another route, and descended to the point of the Red Sea, to the canals of Sesostris (see Strabo), and wealth and activity were transferred to Memphis.

This is manifestly what Diodorus means when he tells us (lib.i.sect.

2), that as soon as Memphis was established and made a wholesome and delicious abode, kings abandoned Thebes to fix themselves there.

Thus Thebes continued to decline, and Memphis to flourish, till the time of Alexander, who, building Alexandria on the border of the sea, caused Memphis to fall in its turn; so that prosperity and power seem to have descended historically step by step along the Nile; whence it results, both physically and historically, that the existence of Thebes was prior to that of the other cities.