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HISTORY OF ENGINEERING.
Book I.
Modern nations have neither excelled the Romans in works of this kind, nor rivalledthem in boldness, by lifting out of the ocean walls so lofty and durable as many theyliave left us ; their engineers formed artificial islands as well as breakwaters, and in what-ever they undertook, they seem to have blended the arts with a thorough knowledge ofconstruction. rhe medails of some of the Roman emperors show the taste bestowed uponthese public works; and no bounds seem to have been set to the area they walled 'in fromthe sea. One of their ports must have had the character of an extensive island, as its con-nection with the land could hardly be seen, at the first view, from its length and thestretching out of its moles. The ports called angiportum were very narrow, and considerableskill was required to work vessels into them. Juvenal notices the extent of some of themoles constructed in his day, and observes that such ports as those of Claudius , the work ofnature and of art, were wonderful for the extent of their foundations, laid at the bottom ofthe sea.
We find Roman harbours well calculated to receive and protect the vessels which enteredthem: at the mouths of rivers they drove in ranges of piles, planked over, and coveredwith pitch ; at the extremity of each mole was a tower or contrivance by which a chain orboom could be stretched across the entrance, and protect the port from any sudden attackof an enemy. When an artificial port was formed on the coast, for the security of ships,they constructed a mole, in a circular shape, or with vast arms, like crabs' dates (chelai),or, as Cicero terms them, with cornua: Epist. ad Attic, lib. ix. ep. 19. A Roman harbour,or Claustra, was entirely shut in, and none could gain admission without the consent of themariners who occupied the watch towers at its entrance.
That part of the harbour by which you entered was called Ostium and fauces , or the mouthbetween the arms of the semicircle : when the vessels had entered, they were made fast tothe shore, or lay at anchor. Where a flat shore presented itself, the vessels on their arrivalwere run backwards upon it, with their heads towards the sea, when the rowers, inhibereremos, hung up their oars out of the reach of the waters, that they might not be broken :sometimes they were attached to the sides of the vessel; according to Ovid , “ to theship’s sides the seamen hung their oars.”
The port of Ostia, or mouth of the Tiber, having silted up, we trace those of Claudius and Trajan , and the diversions of the river far from the present shore; the whole features ofthe coast are now materially changed, and a wide marsh lies in front of the port ofClaudius .