This shews also that _stagna_ do not necessarily mean ponds; any reservoir of water is a _stagnum_, whether supplied by a natural spring or by an aqueduct. Neither of these now remaining are of the time of Nero, they belong to later repairs or alterations; but the great thickness and strength of the wall of so little height could only have been made to support the weight of water. This is especially evident in the upper view, where the wall is nearly as thick as it is high. In this passage the canal, lined with lead, was supported on massive wooden beams; in the lower view the canal in that passage, which is wider than the other, was supported on the brick arches of the second or third century, shewn in this view. It is even probable that the _stagna_ of Nero were in the same place as these, as a good deal of brickwork of his time is on a higher level than these walls, and the two sheets of water, one on either side of the great central passage, would have been magnificent sheets of water, about three hundred feet long and fifty or sixty or more wide in the central part, though narrow at both ends. It is still possible, though not probable, that the _stagna_ of Nero were on a lower level, cut through a bed of tufa, which is not generally very thick, to the clay of the Tiber valley beneath. This would account for the central passages on the site of the _stagna_ having suffered so much from the earthquakes, while the great corridors of the Flavian Emperors, standing on the bed of tufa, have not suffered at all. THE COLOSSEUM. PLATE XI. TWO CAPITALS. A. FROM THE UPPER STOREY. B. FROM THE LOWER ONE, OR THE PODIUM. [Illustration: COLOSSEUM—TWO CAPITALS A. OF UPPER STOREY—B. OF LOWER] DESCRIPTION OF PLATE XI. TWO CAPITALS. A. FROM THE UPPER STOREY. B. FROM THE LOWER ONE, OR THE PODIUM. It will be seen at once that this capital (A) is intentionally left in a rude state to be seen from a distance[247], the upper gallery being nearly a hundred feet above the level of the arena. A great number of these capitals, and of the white marble columns to which they belonged, have rolled down from the top of the building to the bottom in an earthquake, crushing all the seats of the galleries in their fall; as many as forty of them have been found, and a still larger number of broken columns, which have evidently fallen with great force; some of them have been found passing quite through the walls in the substructure, and can be still seen with one end on one side of the wall, and the other on the opposite side. B. is a highly-finished capital of the Corinthian order: of this kind only three or four have been found, but much more perfect than most of the others. They were probably on the short columns of the _podium_ by the side of the state entrance. THE COLOSSEUM. PLATE XII. RESTORATION OF ONE COMPARTMENT OF THE SUPERSTRUCTURE. [Illustration: COLOSSEUM—SUPERSTRUCTURES RESTORATION OF ONE COMPARTMENT] DESCRIPTION OF PLATE XII.