126

HISTORY OF ENGINEERING.

Book I.

necessity, by lighting them with lamps and candelabra?, which contributed greatly to theirdecoration. The most magnificent we now see at Rome were found in the thermic; theirlight was thrown on crystal balls, according to Seneca, placed in the vaulting, or on thewalls, so as to produce the most dazzling reflection : the introduction of glass as a decorationbelongs to the time of Pliny , who calls it a modern invention ; it did not exist according tohim in the time of Agrippa , whose baths were decorated with coloured tiles, or a stuccocalled Albarium Opus; in one excavation, the vaultings were thrown into compartments ofstucco, painted and gilt.

All the walls and masses composing them were built in rough masonry, filled up withsmaller stones, the facings of which were of brick covered with stucco, ornamented withpaintings, marbles, and precious stones. Generally every apartment was vaulted in the samekind of masonry; but in order to produce more lightness, tufa, pumice-stone, or extremelylight lava, were used.

The large apartments in the baths of Caracalla were vaulted. The pavement was formedof masonry covered with stucco or mosaic.

The six apartments of which the ancient baths were composed were thus arranged : —

In the first there was nothing remarkable but the shelves or closets, in which were placedthe clothes of the bathers.

In the second was the cold bath, called Lavacrum by the Romans, where was the basin,in which several persons could bathe at a time. It was of granite or marble, and sometimesof masonry covered with a strong cement, or capped by an edge of freestone : this cementacquired by time more hardness than stone ; vessels were often made of a single piece, impe-netrable to water; and as it is in the angles that square vessels generally became injured,care was taken to round them all internally ; the bottom was so hollowed as to be deepest inthe middle; they were finished by an edge or return on three sides only, called the labrum,and the centre alveum. Vitruvius , lib. G. cap. 10. says, that the size or capacity of thebasin should be proportioned to the number of persons intended to bathe, but they shouldnot be less than 6 feet wide, two of which were given to the lower step and the lip ; thelength should be one and a half the width. The fourth side of the basin, which was thatby which it was entered, was occupied by the steps which led to the bottom; beyond theedge or lip, and around the three sides, was a balustrade to separate those who ■were bathingfrom those who waited for their turn, on which account, between the balustrade and thewalls of the hall, there was a gallery called schola, which was required to be sufficientlywide to accommodate all who were to replace the bathers ; this gallery was paved in marble ;the walls, as well as the cement which covered them, required to be made with care andprecaution, on account of the humidity occasioned by the evaporation of the water. Perrault,in his translation of Vitruvius , imagined that the baths were lighted by an opening in thecentre of the vault; but it appears that Vitruvius himself says, that the bath should beplaced under the light of the window, so that the shadow of those who are around it shouldnot intercept the rays, which would lead to the supposition that there was no gallery on theside of the window.

There are several of these cold baths in the therrrue of Caracalla , one of which remainsin a vaulted hall, preceded by a small vestibule with a portico, said to have been added bySeptimius Severus . The apartment is 31 feet long,and 15 feet 3 inches wide; the basin isin masonry, with an edge in freestone, which separates it 18 inches from the bottom wall,and the two returns: the hollow of the basin between the edges is 12 feet wide, by 15 feetlong: the descent is in front, by seven or eight steps, which are the whole width of the hall,viz. four to arrive at the edge of the bath, and three or four to descend to the bottom, sothat those who washed could sit on the edge, which was round the three sides. The bottomand sides are covered with a very thick and hard cement; the surface being crystallised,which probably greatly contributed to its hardness; such incrustations are apparentin all reservoirs and receptacles for water throughout Rome , the water having the propertyof petrifying, if we may so term it, the surface of all cements, which are moreover wellmixed, and made with the greatest care.

This hall was lighted by a semicircular window opened at the top of the lower wall,against which the baths were formed.

Along the side of the thermae which is to the north-east there are fifty apartments,apparently destined for the same purpose, so that a thousand persons might bathe at a time;the water must have been tepid, for it appears by the pipes and conduits which are left, thatit came from the warm baths of the great thermae, of which these baths formed, as it were,the inclosure; between the baths, and at nearly equal distances, were the remains of four largestaircases, of two rampes, which led to the thermic, the soil of which was 20 feet higherthan that of the baths. The whole edifice was built on the declivity of the mount Aventine,so that the first served as the substructure or foundation of the upper soil.

All the walls and vaults are in masonry, faced in brick, and covered with cement ofmortar; the pavement is in masonry, which proves that the baths were only destined forthe common people.