OS'TIA. An ancient city of Latium, at the mouth of the Tiber. 15 miles from Rome. It is said to have been founded by Anew; Marcius, and was regarded as the oldest Roman colony. It first acquired importance from its salt works, the establishment of which is attributed to Ancus Marcius, and afterwards was the port where the Sicilian, Sardinian, and African corn shipped for Rome was landed. Its name first occurs during the Second Punic War. It was long the prin cipal station of the Roman navy; but its har bor was exceedingly bad, and gradually the entrance became silted up with alluvial deposits, so that vessels could no longer approach it. but were compelled to ride at anchor and disembark their cargoes in the open roadstead. At length the Emperor Claudius dug a new harbor or basin two miles north of Ostia, and connected it with the Tiber by a canal. It was named the Fortes Augusti, and around it soon sprang up a new town called Portus Ostiensis. Port us Urbis, Por
tus Roarer, and often simply Port us (modern Porto). The work of Claudius was carried further by Trajan. After the fall of the Roman Empire Ostia declined rapidly, and in the eighth century it was a mere ruin. During the Middle Ages a village—the modern Ostia—was built about half a mile above the site of the ancient town; but it has not more than about a thousand permanent inhabitants, who still carry on the manufacture of salt. Ostia has the reputation of being the seat of the earliest bishopric save that of Rome, and the Cardinal Bishop of Ostia (and Velletri) is Dean of the Sacred College. The ruins of the ancient Ostia extend for a mile and a half along the banks of the Tiber, and are nearly a mile in breadth.