At the Double Columns the detachment of the fleet which had come from the Dardanelles was joined by other vessels which had been swept in from the Black Sea and the Marmora. Phrantzes gives the total number at four hundred and eighty.[230] Many of the vessels from the Black Sea were laden with wood or with stone balls. The Turkish fleet under Baltoglu’s command thus consisted of a number of vessels from all the shores of the Marmora, the Bosporus, and the Black Sea. Among them were triremes, biremes, _fustae_, _parandaria_, and galleys. As we shall find these terms recurring, it will be well to realise what they signified. The trireme of the fifteenth century was a long and fast vessel which had usually two masts, was very low in the water and, though employing sails, was mainly dependent for propulsion on her oars. The arrangement of oars from which she derived her name was not in tiers one above the other and thus requiring oars of different length. The ‘banks’ or benches, unlike those in ancient ships, were all on the same level. The oars were short and all of the same length: but three oars projected through one rowlock port, each oar working on a tholepin. ‘One man one oar’ was the invariable rule. Three men occupied one bench or seat. Down the middle of the trireme ran a central gangway called the _histodokè_, primarily intended as a rest for the mast, but upon which the officer passed to and fro to keep time for the oarsmen. There were thus three upon each side of him, or six men nearly abreast throughout the length of the trireme. The arrangement upon a bireme was of a similar character, except that two men instead of three occupied one bench. There was also but one mast. The _fusta_ resembled the bireme in having two oarsmen on each bench on each side of the _histodokè_ from the stern to the one central mast, but only one on each side from the mast forward.[231] The _fusta_ was a lighter boat than the trireme, and could thus be propelled more rapidly. The _parandaria_ were heavy boats, probably not differing much from the sailing barges or _mahoons_ still used in the harbour of Constantinople, the Bosporus, and Marmora. The name ‘galley’ was in the fifteenth century applied to war vessels propelled by a single bank of long oars on each side. Leonard employs the term _dromon_, not, as it had been used in earlier days from about 500 A.D., as a generic term for war ships,[232] but to indicate the large _caiques_, usually of twelve oars, which could not be classed as triremes, biremes, or fustæ. Probably the majority of the vessels in Mahomet’s fleet were not larger than the ordinary bazaar caiques which ply between Constantinople and distant villages on the Bosporus or the Marmora or are employed in deep-sea fishing.[233] [Sidenote: Turkish army arrives before the walls, April 5.]