War and traffic furnished the great supplies of slaves or chattels for the Athenians. Such chattels were from all nations and races, and the black slaves constituted an accidental and imperceptible minority. Witness Æsop telling the story of a rustic who bought a black slave and unsuccessfully tried to bleach or to whitewash it. If blacks had been common merchandise, the rustic would have been familiar with its nature. Slavery was transmitted from parents to children, if the prisoner of war was not ransomed or the slave not manumitted. But at any time a slave could receive or buy his freedom, and a chattel once liberated could not, under penalty of capital punishment, again be violently enslaved. In the South they begin to legislate for the re-enslavement of the liberated: the odium no longer falls on the individual but on the whole body politic. All over the ancient world the state watched over and protected the once enfranchised slave: the modern slave-holding polity expels him or legislates for his disfranchisement. In Athens, as all over Greece, the offspring of freemen and slave-women were free. At first slaves performed domestic service, and afterward, when their number increased, they were employed in various trades. The state used them in public works, sometimes to row the ships. But the greatest number were employed to work the mills and mines of Attica. However, the state itself did not work the mines, but rented them generally without the slave labor; though private individuals rented them for a term of years, together with the slaves who worked them. Slowly chattelhood spread over the rural economy of Attica. About the time of the Persian wars, rural property was still nearly equally divided among the citizens. Wealth was accumulated and represented in commerce, in various industries, and in the precious metals. But at that time slaves nowhere outnumbered the freemen. At the battle of Marathon the Athenians had ten thousand _hoplites_ or heavily armed able-bodied citizens; at Platea eight thousand; and in both battles nearly as many _peltasts_ or lightly-armed troops--poorer citizens, but not serfs, or retainers, or slaves. Before the invasion of Xerxes, the free population of Attica probably amounted to more than one hundred and twenty thousand of both sexes and all ages. The slave population is estimated at the utmost as sixty thousand.