12I must not omit to speak of the formation of harbours, but explain in what manner ships are secured therein in stormy weather. If they are naturally well situated, and have rocks or long promontories jutting out, which from the shape of the place, form curves or angles, they are of the greatest utility; because, in that case, nothing more is necessary than to construct porticos and arsenals round them, or passages to the markets; and then erect a tower on each side, wherefrom chains may be suspended across by means of machinery.
12The subject of the usefulness of harbours is one which I must not omit, but must explain by what means ships are sheltered in them from storms. If their situation has natural advantages, with projecting capes or promontories which curve or return inwards by their natural conformation, such harbours are obviously of the greatest service. Round them, of course, colonnades or shipyards must be built, or passages from the colonnades to the business quarters, and towers must be set up on both sides, from which chains can be drawn across by machinery.