In later days, other methods were adopted; one of which, attributed by Pliny to the Belgæ,[16] consisted in beating pounded seeds into the fissures between the planks of vessels—a substance, he says, found to be more tenacious than glue, and more to be relied on than pitch. This is evidently the same in principle as the modern practice of caulking. In the same way we find in remote times that pitch and wax were used partly for the prevention of leakage, and partly also to preserve the planks from the sea-weeds and animalculæ with which the waters of the Mediterranean abound.[17] The discovery, too, of what is supposed to have been a galley of Trajan at the bottom of Lake Riccio shows clearly that, in Roman times, sheathing as well as caulking were used to preserve the bottoms of ships. The famous Locke,[18] alluding to this discovery, says, “Here we have caulking and sheathing together above sixteen hundred years ago; for I suppose no one can doubt that the sheet of lead nailed over the outside with copper nails was sheathing, and that in great perfection; the copper nails being used rather than iron, which, when once rusted in water with the working of the ship, soon lose their hold and drop out.” [Sidenote: Names of ships.] Ships in ancient times were known by a great variety of names, most of which are descriptive of the purposes for which they were built, or of the services in which they were employed. Omitting _triremes_, the most usual _ships of war_, the following list enumerates their chief varieties:— Thus _olkas_ was a large heavy tow-barge; _ponto_—a word of Gallic or Celtic origin[19]—a _punt_. _Gaulos_, a round heavy merchant vessel, named probably so originally by the Phœnicians, and preserved to modern days in the galleon or galeass of the Middle Ages, and the _galley_ of later times. _Corbitæ_, slow sailing ships of burthen—so called because they carried baskets at their mast-heads. _Hippagogi_, as their name implies, carried horses. The characteristic of all these vessels was that their structure was bulky, their sides and bottom rounded from the flat, and, though not without rowers, that they were chiefly dependent on their sails. Of a lighter class, and for greater speed, were the _scapha_ (or skiff); the _acation_, or _acatus_; and the _linter_, which, though like _ratis_, often used for any kind of vessel, was more strictly a light boat or wherry.[20] Generically, merchant vessels were called _mercatoriæ_, or _vectoriæ_, as being the carriers of merchandise. So _piscatoriæ_ were boats used for fishing. [Sidenote: Decorations.]