But to counteract this the Tyrians adopted the following contrivance. They filled a vessel, which had been used for transporting horses, with dry twigs and other combustible wood, fixed two masts on the prow, and fenced it round in the form of a circle as large as possible, so that the enclosure might contain as much chaff and as many torches as possible. Moreover they placed upon this vessel quantities of pitch, brimstone, and whatever else was calculated to foment a great flame.[313] They also stretched out a double yard-arm upon each mast; and from these they hung caldrons into which they had poured or cast materials likely to kindle flame which would extend to a great distance. They then put ballast into the stern, in order to raise the prow aloft, the vessel being weighed down abaft.[314] Then watching for a wind bearing towards the mole, they fastened the vessel to some triremes which towed it before the breeze. As soon as they approached the mole and the towers, they threw fire among the wood, and at the same time ran the vessel, with the triremes, aground as violently as possible, dashing against the end of the mole. The men in the vessel easily swam away, as soon as it was set on fire. A great flame soon caught the towers; and the yard-arms being twisted round poured out into the fire the materials that had been prepared for kindling the flame. The men also in the triremes tarrying near the mole kept on shooting arrows into the towers, so that it was not safe for men to approach in order to bring materials to quench the fire. Upon this, when the towers had already caught fire, many men hastened from the city, and embarking in light vessels, and striking against various parts of the mole, easily tore down the stockade which had been placed in front of it for protection, and burnt up all the engines of war which the fire from the vessel did not reach.[315] But Alexander began to construct a wider mole from the mainland, capable of containing more towers; and he ordered the engine-makers to prepare fresh engines. While this was being performed, he took the shield-bearing guards and the Agrianians and set out to Sidon, to collect there all the triremes he could; since it was evident that the successful conclusion of the siege would be much more difficult to attain, so long as the Tyrians retained the superiority at sea.[316] CHAPTER XX. TYRE BESIEGED BY SEA AS WELL AS LAND.