“There are games that give pleasure to the eyes and the ears. Among these we may enumerate the machines which cause the cages to raise themselves, and silently rise to the top of the wooden floor (or stage), and others in unexpected variety, either gaping open or coalescing again, others which were distant drawing together again spontaneously, or those which were near gradually retiring from each other. The eyes of the silly people are astonished at all these sudden movements, the causes of which they do not understand.” Juvenal, writing about A.D. 100, also mentions the _pegmata_ in the Colosseum[94], with the _velaria_. There is a small stream of water in front of the dens, supplied by the aqueducts, from which the animals could drink. Behind each den is a small cell, four feet square, descending from above, called _catabolicus_[95], but not lower than ten feet from the ground, apparently for a man to go down and feed them safely. In what seems the earliest part of the two tufa walls, near the south-west end of the building, the apertures in the inner part are square-headed doorways, and not arches[96]. These are filled up with brick walls of the time of the Flavian emperors, or later[97]. In other parts of these tufa walls there are arches in the inner wall, also supported by brick arches of the time of the Flavian emperors, in which the bricks are thicker, and there is more mortar between them than in those of the time of Nero. On the floor of the central passage is a remarkable piece of ancient wooden framework lying on the ground[98], which has the appearance at first sight of having been burnt, but long exposure to wet will have the same effect on wood that fire has. (The Irish bog-oak often appears as if it had been burnt, and wood has been dug from under the foundations of an Irish round tower that had the same appearance.) This framework is a good deal worn, as if it had been much used; it has all the appearance of a dry dock, or a cradle for a vessel to stand upon. When the _stagnum navale_ of Nero was in use, there must have been some machinery for lifting up the vessels and placing them on the canals. They must also have been removed out of the way when the water was let off, and the boarded floor of the stage or arena replaced[99]. On each side of this wooden framework is a series of slabs of stone about a yard square, placed upright, with a hole through each for a water-course. These seem to have been for fixing the wooden frame of a _cradle_ for the vessels to stand upon, and to keep them upright. This plan is well shewn in a drawing of a trireme that was made for Napoleon III., to shew the French people what a Roman trireme was like[100].