At Bordeaux the ruins of the amphitheatre are called the (_arènes_) arena, and it evidently had a boarded floor covered with sand, as in the Colosseum; and the superstructures, with the seats, are more perfect than in Rome. There is a great general resemblance, but the details are not the same. The Colosseum is the only amphitheatre which has _double_ corridors round it, and the absence of this outer passage makes a different arrangement of the stairs to the _vomitoria_ necessary in this and other amphitheatres, where the people went straight out through each archway. SUBSTRUCTURES COMPARED. In treating of the amphitheatres in general, and corroborating the account given in this work of the Colosseum, it must be borne in mind that in every theatre a considerable space is required behind the scenes for the use of the actors. The performances in an amphitheatre would equally require such space for the performers when off the stage, and the only space to which they could possibly retire is under that stage which is called the _arena_, because it was covered with sand; and it has been shewn that in these substructures there are numerous passages and contrivances for the machines to send up the wild beasts to be hunted, the men and the dogs to hunt them, and the athletes for the wrestling matches; we have also canals for water for the keels of the vessels, in some instances, but not in all; in some cases, the vessels employed could only have been rowing-boats, _rates_. We have also mention of battles with swords in the _naumachia_, and of many men being killed. This seems to make it clear that the principal amusement consisted in the crew of one vessel trying to board the other, and the defendants preventing their doing so in every way that they could, either by throwing them off into the water, or with swords and spears. At Pozzuoli, where the substructures are nearly perfect, there are remains of an intermediate passage, as if for men to run along; and this has been traced to communicate with the Emperor’s seat, and is thought to have been for messengers to go with orders, and to give the necessary directions. All that remains of this intermediate passage are the corbels for carrying a wooden gallery upon. There are similar corbels for an intermediate passage between two floors in the Colosseum, but here in the upper part, apparently for the sailors to run along to furl or unfurl the awning, not in the substructures; there also appear to have been separate stairs and _vomitoria_ for that passage, and as we know that several hundred sailors were employed in the Colosseum, such an arrangement would be quite necessary.