a. The dens for wild beasts. b. The shaft for a man to descend and feed the animals. c. The drain and flood-gate at the mouth of it. e, e. Small brick chambers of the time of Nero. All the sockets that are visible are shewn in the plan, whether in the passages or in the chambers. THE COLOSSEUM. PLATE IX. ARCHES IN THE SUBSTRUCTURE. [Illustration: COLOSSEUM. ARCH OF THE SECOND CENTURY, IN THE SUBSTRUCTURE. BRICK ARCH OF NERO, IN THE SUBSTRUCTURE.] DESCRIPTION OF PLATE IX. 1. ARCH OF THE SECOND CENTURY IN THE SUBSTRUCTURE. In addition to the two ancient walls of tufa parallel to each other round the edge, with the grooves for lifts in them, there are some remains here and there of a third wall of tufa within the other two, and this appears to have been much shaken by an earthquake. In this, little is perfect, but in the parts that remain there are arches, and these arches are supported by brick walls of different periods. The upper arch in this plate is supported by a brick wall of the second century, as is seen by the thickness and quality of the bricks and of the mortar between them. This is shewn by the six-foot rule, each foot painted alternately black and white, by which the bricks can be counted the same as on the spot. 2. ARCH OF THE FIRST CENTURY IN THE SAME. This small arch is in the same wall, but in this case the brick arch that supports the tufa is clearly of the time of Nero[246]. The long, thin bricks of his time, nine or ten to the foot, are well known to all Roman archæologists, and are so marked that there is no mistaking them: they are thus good evidence that the amphitheatre of Nero, mentioned by Pliny, was on the same site as the Flavian Amphitheatre. A segment of another arch of the same period abuts against it, to support it like a flying buttress, and is seen in the plate. THE COLOSSEUM. PLATE X. SUBSTRUCTURES. REMAINS OF TWO CANALS, ONE SUPPORTED ON TIMBERS, THE OTHER ON BRICK ARCHES. [Illustration: COLOSSEUM—SUBSTRUCTURES A. REMAINS OF A CANAL SUPPORTED ON TIMBERS B. —— OF ANOTHER CANAL SUPPORTED ON ARCHES] DESCRIPTION OF PLATE X. SUBSTRUCTURES. REMAINS OF TWO CANALS, ONE SUPPORTED ON TIMBERS, THE OTHER ON BRICK ARCHES. These two canals, parallel to each other, to be supplied with water by the aqueducts, and used for the _naumachia_ or naval fights, are among the most curious discoveries brought to light in the recent explorations. They shew how completely the whole of the great public exhibitions of the ancient Romans were theatrical displays, with all the usual tricks of a theatre, just the same as in a Christmas pantomime.