=80.= The faction of the Alemæon´ids, who had been exiled under their leader, Megacles, now gained strength for an active demonstration. They bribed the Delphic priestess to reiterate in the ears of the Spartans that “Athens must be delivered.” These brave but superstitious people had a friendship of long standing with the Pisistrat´idæ, but they dared not disobey the oracle. An army was sent to invade Attica: it was defeated and its leader slain. A second attempt was more successful: the Thessalian cavalry which had aided the tyrant was now defeated, and Hippias shut himself up in the citadel. His children fell into the hands of the Spartans, who released them only on condition that he and all his kin should withdraw from Attica within five days. A perpetual decree of banishment was passed against the family, and a monument recording their offenses was set up in the Acropolis. =81.= Clisthenes, the head of the Alemæonidæ, now rose into power. Though among the highest nobles, he attached himself to the popular party, and his measures gave still greater power to the people than the laws of Solon had done. Instead of the four tribes, he ordained ten, and subdivided each into demes, or districts, each of which had its own magistrate and popular assembly. The Senate, or Great Council, was increased from 400 to 500 members, fifty from each tribe, and all the free inhabitants of Attica were admitted to the privileges of citizens. To guard against the assumption of power by one man, as in the case of Pisistratus, Clisthenes introduced the singular custom of _ostracism_, by which any citizen could be banished without accusation, trial, or defense. If the Senate and Assembly decided that this extreme measure was required for the safety of the state, each citizen wrote upon a tile or oyster-shell the name of the person whom he wished to banish. If the name of any one person was found upon six thousand ballots, he was required to withdraw from the city within ten days. The term of his exile was at first ten years, but it was afterward reduced to five. =82.= Isag´oras, leader of the nobles, disgusted by the rise of his rival, called again upon the Spartans to interfere in Athenian affairs. Cleom´enes, king of Sparta, advanced upon Athens, and demanded the expulsion of Clisthenes and all his family, as accursed for the sacrilege committed, nearly a hundred years before, in the murder of Cylon. Clisthenes retired, and Cleomenes proceeded with his friend Isagoras to expel seven hundred families, dissolve the Senate, and revolutionize the city. But the people rose against this usurpation, besieged Isagoras and his Spartans in the citadel, and only accepted their surrender on condition of their withdrawing from Attica. Clisthenes was recalled and his institutions restored. [Sidenote: B. C. 507.]