We are now below all the regular bridges and at the head of deep-sea navigation. In truth the Tiber is too shallow and uncertain a river to be very practical for large ships, even of the Græco-Roman type. Only small vessels, mostly of the coasting variety, come up to Rome on direct voyages. But the regular procedure is to unload the deep-sea craft at Ostia and then bring up their lading along the twenty odd miles of the crooked river, in light-draft barges. These barges--some worked by long oars, some towed by their crews walking along the shore--are constantly coming and going. To-day as every day the river is alive with them, and many others are moored closely, prow following stern, all along the magnificent stone embankments which serve as quays. Approaching one of these ungainly flat-bottomed craft, we see it has a little cabin on the poop, and its name, the “Isis of Geminus,”[130] is marked in large red letters upon the black hull. The captain is now standing by the mooring cable passed through a sculptured lion’s mouth, directing a great gang of porters carrying sacks of grain down a bank to the wharf, where Geminus, the owner himself, assisted by a government clerk carefully checks off every sack upon their bills of lading. A little scrutiny reveals that while all kinds of commodities abound on the Emporium two take wide precedence over all others--_grain_, from Egypt and provincial Africa; and _marble_, from Numidia, Greece, and Asia Minor. [Illustration: RIVER BOAT LOADED WITH HOGSHEADS OF WINE.] =214. The Marble and Grain Trades.=--The marble trade, indeed, demands a special section of the wharves. For the government buildings the imperial procurators in the marble-producing provinces are constantly sending in valuable cargoes, and for monolithic columns and extra large blocks specially constructed barges are used to bring them from Ostia. Even now a great labor gang is painfully disembarking a splendid column of Egyptian porphyry for the new Temple of Venus and Rome. Behind the Emporium stretches an ugly complex of offices, warehouses, porters’ barracks, and the like, but most conspicuous and ugly of all are the public _horrea_. These are tall gaunt storehouses for the keeping of grain, enormous fabrics of dull gray concrete, “elevators” in fact, carefully maintained by the government for the victualing of the capital. There are said to be more than three hundred horrea, and the largest are named for the emperors who built them--the Horreum of Augustus, of Domitian, and the like. Thousands of men are employed around them, and the state of their contents can give anxious nights to the Imperial Council. Unlovely as they seem, they are vital to the life of Rome.