was 620 ft. long and 513 wide, and the height was about 162 ft. It was situated in the hollow between the Esquiline and Cælian hills. The ranges of seats were admirably planned so as to enable all the audience to have a view of what was going on in the arena, and great skill was shown both in the arrangement of the approaches to the different tiers and in the structural means for supporting the seats, and double corridors ran completely round the building on each floor, affording ready means of exit. Various estimates have been made of the number of spectators that could be accommodated, and these range from 50,000 to 100,000, but probably 80,000 was the maximum. Recent excavations have brought to light the communications which existed between the arena and the dens where the wild animals and human slaves and prisoners were confined, and some of the water channels used when mimic sea-fights were exhibited. The external façade is composed of four stories, separated by entablatures that run completely round the building without a break. The three lower stories consist of a series of semicircular arched openings, eighty in number, separated by piers with attached columns in front of them, the Doric order being used in the lowest story, the Ionic in the second, and the Corinthian in the third; the piers and columns are elevated on stylobates; the entablatures have a comparatively slight projection, and there are no projecting keystones in the arches. In the lowest range these openings are 13 ft. 4 in. wide, except the four which are at the ends of the two axes of the ellipse, and these are 14 ft. 6 in. wide. The diameter of the columns is 2 ft. 8¾ in. The topmost story, which is considerably more lofty than either of the lower ones, was a nearly solid wall enriched by Corinthian pilasters. In this story occur two tiers of small square openings in the alternate spaces between the pilasters. These openings are placed accurately over the centres of the arches of the lower stories. Immediately above the higher range of square openings are a series of corbels--three between each pair of pilasters--which probably received the ends of the poles carrying the huge awning which protected the spectators from the sun's rays. The whole is surmounted by a heavy cornice, in which, at intervals immediately over each corbel, are worked square mortise holes, forming sockets through which the poles of the awning passed. The stone of which the façade of the Colosseum is built is a local stone, called travertine, the blocks of which are secured by iron cramps without cement. Nearly all the internal portion of the building is of brick, and the floors of the corridors, &c., are paved with flat bricks covered with hard stucco. These amphitheatres were occasionally the scene of imitations of marine conflicts, when the arena was flooded with water and mimic vessels of war engaged each other. Very complete arrangements were made, by means of small aqueducts, for leading the