Not the least remarkable feature in this great growth was the celerity with which it was achieved. The period between the Persian and the Peloponnesian war was only sixty years in duration. Yet in that brief space of time the great growth we have chronicled took place, and the architectural splendor of the city was consummated. The devastation of the unhappy Peloponnesian war put an end to this external growth, and left the Athens of old frozen into marble, a thing of beauty forever. But the intellectual growth went on, and for centuries afterwards Athens continued the centre of ancient thought. And now the question in point is how all this came about, and what made Athens great and glorious among the cities of Greece. It all flowed naturally from her eminence in the Persian war. During that war there had been a league of the states of Greece, with Sparta as its accepted leader. After the war the need of being on the alert against Persia continued, and Greece became in great part divided into two leagues,--one composed of Sparta and most of the Peloponnesian states, the other of Athens, the islands of the archipelago, and many of the towns of Asia Minor and Thrace. This latter was called the League of Delos, since its deputies met and its treasure was kept in the temple of Apollo on that island. This League of Delos developed in time to what has been called the Athenian Empire, and in this manner. Each city of the league pledged itself to make an annual contribution of a certain number of ships or a fixed sum of money, to be used in war against Persia or for the defence of members of the league. The amount assessed against each was fixed by Aristides, in whose justice every one trusted. In time the money payment was considered preferable to that of ships, and most of the states of the league contributed money, leaving Athens to provide the fleet. In this way all the power fell into the hands of Athens, and the other cities of the league became virtually payers of tribute. This was shown later on when some of the island cities declined to pay. Athens sent a fleet, made conquest of the islands, and reduced them to the state of real tribute payers. Thus the league began to change into an Athenian dominion. In 459 B.C. the treasure was removed from Delos to Athens. And in the end Chios, Samoa, and Lesbos were the only free allies of Athens. All the other members of the league had been reduced to subjection. Several of the states of Greece also became subject to Athens, and the Athenian Empire grew into a wealthy, powerful, and extended state. [Illustration: A REUNION AT THE HOUSE OF ASPASIA.] The treasure laid up at Athens in time became great. The payments amounted to about six hundred talents yearly, and at one time the treasury of Athens held the great sum of nine thousand seven hundred talents, equal to over eleven million dollars,--a sum which meant far more then than the equivalent amount would now.