Book I.

128 HISTORY OF ENGINEERING.

vaulted, which is very probable, but it is still less possible to decide in what manner it waslighted.

The pavement of this stove, as well as of the warm bath at the side, is raised about 2 feet6 inches above that of the place in which is the entrance of the furnace. There is also theremains of a leaden pipe which conveyed the water into the warm baths ; its externaldiameter is about 2£ inches. In these apartments were the vases or kettles in which thewater was warmed ; there is no vestige of the laconicum, but at the side of the furnace thereis a square recess in the wall with a bench, the situation of which must have been muchwarmer than that of the niche at the bottom, so that persons could place themselves eitherin one or the other, according to the greater or less degree of heat desired.

In another part of the same ruins was a stove of a circular plan, with a step and nichesaround; it is lighted by a round hole about l£ feet in diameter, made in the middle of thevault; this hole might have been the situation of the brazen shield, to be raised or loweredfor the purpose of increasing or diminishing the heat.

A bath was discovered at Rome , in which the basin was covered with a coating of cementso hard, that it was impossible to dissolve it sufficiently to analyse its substance, it was aRoman palm thick, and capable of resisting not only the heat of the water, but the actionof any heat whatever.

The Romans having introduced the use of the bath wherever they had carried theirarms, we find remains of them in their most distant provinces. At Wroxeter in thecounty of Shropshire was discovered a small square room, the pavement of which was con-structed in the folllowing manner : —there were four rows of pillars in brick 8 inchessquare, put together with very fine red cement; they were placed on a bed of bricks a footsquare; the platform above the pillars was formed by bricks 2 feet square, and of extraor-dinary hardness ; the bed above was composed of a mortar of broken tiles and large gravel ;round the internal walls were fixed by iron clamps pipes whose inferior extremity abuttedagainst the platform of large bricks, which formed the floor above the pillars; the other endcame to the surface of the upper pavement; it was covered by a row of bricks; each pipehad two opposite holes to communicate the heat.

Six miles from Chester, a part of a bath recognised as Roman construction was discovered,in which was a hypocaustum surrounded by walls cut in the rock. The lower pavementwas of brick laid in cement; the platform was supported by brick pillars, which appeared tohave been polished, and had in several places holes above which were brick tiles, to distributethe heat. On some of the bricks were inscribed LEG. XX., whence it was inferred thatthis hypocaustum had been constructed by the twentieth legion, which was called the“ Victorious.”

With regard to the vaults of the warm baths, Vitruvius says that it is better to makethem in masonry than in carpentry, but when a floor is required, there should be underneatha filling-up of terra cotta, made in the following manner. Bars or ares of iron must be sus-pended to the carpentry with clamps of the same metal, placed sufficiently close, that fromone to the other there may be put flat tiles without edges, so that a vault may be formedisolated from the floor and entirely suspended by iron ; over it should be laid a coatingof clay mixed with hair, and the under side towards the pavement should be first coveredwith cement, and then finished with polished stucco ; the vault would be better if double, inorder that the vapour, which might penetrate the first, should be stopped by the second,and thus preserve the carpentry from humidity.

The Thermce discovered in 1824 at Pompeii are highly interesting, as they exhibit thearrangements of such an establishment out of the Imperial city ; they occupy an irregularquadrilateral space north of the forum, and were entered from the street by a small passagewhich opened into a court 60 feet in length, on two sides of which was a Doric portico, onthe other a crypt, over which was a second story. At the opposite angle of the court wasanother exit, where was situated the latrina; to this succeeded a sort of pronaos with seats,which was vaulted and lighted at night by a lamp, so placed that its rays fell into thechambers around. This lamp was protected by a circular convex glass, the fragments ofwhich were discovered. From the court the bathers passed to another chamber, in whichwere found above 500 lamps, made of terra cotta, with various devices upon them; thisroom was the frigidarium, and served also as the spoliatorium, apodyterium, or apolyterium,or the place where the clothes were left; many holes still remain in the walls in which thepegs were inserted, on which were hung the garments of the bathers, and which were calledCaprarii, probably from resembling two horns. This spacious chamber is vaulted from aprojecting cornice, decorated with griffins and lyres richly painted. The vault is panelled,coloured red and white, and the pavement is mosaic. The walls were coloured yellow,around which was a stone seat with a step a little elevated above the floor. At each endwas a window, similar to the one remaining on the south end, and which opened upon thecemented roof of one of the chambers. This window had a plate of thick glass, slightlyground on one side, and secured by copper bars. Another room contained the natatio, orswimming bath ; in the time of Pliny , it was called baptisterium. 'Dus chamber is perfect;