When the time arrived, the Persians advanced to the attack of the city in that quarter, and the Babylonians rallied as usual on the walls to repel them. The contest had scarcely begun before they found that the gates were open, and that the columns of the enemy were pouring in. The city was thus soon wholly at the mercy of the conqueror. Darius dismantled the walls, carried off the brazen gates, and crucified three thousand of the most distinguished inhabitants; then establishing over the rest a government of his own, he withdrew his troops and returned to Susa. He bestowed upon Zopyrus, at Susa, all possible rewards and honors. The marks of his wounds and mutilations could never be effaced, but Darius often said that he would gladly give up twenty Babylons to be able to efface them. CHAPTER VIII. THE INVASION OF SCYTHIA. B.C. 513 Darius's authority fully established throughout his dominions.--The Scythians.--Ancient account of them.--Pictures of savage life.--Their diversity.--Social instincts of man.--Their universality.--Moral sentiments of mankind.--Religious depravity.--Advice of Artabanus.--Emissaries sent forward.--The petition of Oebazus.--Darius's wanton cruelty.--Place of rendezvous.--The fleet of galleys.--Darius's march through Asia Minor.--Monuments.--Arrival at the Bosporus.--The bridge of boats.--Reward of Mandrocles.--The group of statuary.--The Cyanean Islands.--Darius makes an excursion to them.--The two monuments.--Inscriptions on them.--The troops cross the bridge.--Movements of the fleet.--The River Tearus.--Its wonderful sources.--The cairn.--Primitive mode of census-taking.--Instinctive feeling of dependence on a supernatural power.--Strange religious observance.--Arrival at the Danube.--Orders to destroy the bridge.--Counsel of the Grecian general.--The bridge is preserved.--Guard left to protect it.--Singular mode of reckoning.--Probable reason for employing it.--Darius's determination to return before the knots should be all untied.