galleries constructed in every direction under the city of Rome. The principal channel, called Cloaca Maxima, has a breadth of about sixteen feet, with a height of thirty, and all the others communicate with it. The bottoms, sides, and arches are formed with large blocks of stone, well and strongly connected together; and notwithstanding the weight of the buildings, ruins, and other things either incumbent upon, or forced down them, recent travellers represent that their solidity and good condition is still very remarkable, although choked up at one end through the neglect, laziness, or indifference of the present public functionaries of Rome. "Such the sewers huge, Whither the great Tarquinian genius dooms; JOHN DYER. CHAPTER XI. Materials employed in the construction of the Roman Aqueducts. Variations in forming them. Knowledge of Hydrostatics displayed by the Romans. Lead and Earthern Pipes. Instruments used for taking levels. Modes of distributing and measuring Water. Magnitude and splendour of Antoninus Caracalla's Baths; adorned with fine Paintings and Sculptors. Extraordinary grandeur of those erected by Dioclesian: number of People employed in constructing them. Titus's Baths on the site previously occupied by the house and gardens of Mæcenas, and near the residences of Virgil and Horace. Great number of apartments in the Baths of Caracalla: their uses and conveniences. Methods of heating the Baths. Motives for constructing the great Roman works. Contrast of modern times. VARIOUS circumstances concerned in the formation of the Roman aqueducts are deserving of observation;— for instance, the materials employed were different even in the same aqueduct; and in constructing an arch of the Aqua Martia there were used three kinds of stone, one reddish, another brown, and a third of an earthy colour. The Aqua Claudia was constructed with a beautiful hewn stone, whilst others were built with bricks and a strong cement, which so firmly united them as to render the work almost a solid mass. Moreover, the Aqua Appia differed from the others, by its having a peculiar construction of width, as it approached the point where the water was disembogued. Although several of the Roman aqueducts might have been constructed in a straight line, yet it is remarkable that their contrivers adopted a sinuous course with numerous windings. Various plausible reasons have been sug gested for their preference of such a devious track; some presuming its chief object was to avoid the expense of erecting arcades of great height and solidity; whilst others have inferred that it solely had in view the preserving of a gentle and equable current for the water. The latter reason appears to be both plausible and cogent; for if the velocity had been considerable, the strong and impetuous motion of the water would have continually kept it in a turbid state, and consequently rendered it unsuitable for the beverage and other uses of the inhabitants. However, another important circumstance demanded peculiar attention and consideration; this was the prevention of injury to the aqueducts, from the constant attrition produced by the force and motion of a very quick current upon the bottoms and sides of their channels, for the repairing of such dilapidations would inevitably be attended with great inconvenience. The eminent professor quoted in a former page, and who was alike distinguished for superior intellect, diligence of research, and diversity of attainments, has enumerated several circumstances illustrative of the scientific knowledge and mechanical skill of the ancient Romans. His detail is concise, but it conveys much curious information that may interest and gratify those, who may be desirous of learning what were the acquisitions of a people, so celebrated in the annals of the world, and whose various achievements will never cease to obtain the admiration of mankind. "It is a prevailing opinion," observes Professor Leslie, "that the Romans, amidst all their magnificence, were ignorant of the simplest elements of Hydrostatics, and • A recent publication has the following remarkable passage"Ignorance of the principle by which liquids return to their level, and was adjusted till the water rose equally in them; the chorobates, or perambulator, which he considered as the most accurate instrument, was composed of a rod twenty feet long, having a square and plummet attached at each extremity. Vitruvius allows only half a foot in the hundred for the slope of an aqueduct. After water had reached the walls of the city, it was admitted into a reservoir or castellum, divided into three distinct and equal compartments, one to feed the pools and fountains, another to supply the public baths, and a third for the accommodation of palaces and private houses. The distribution of the water was commonly effected by leaden pipes. The smallest of these was called a denaria, being ten feet in length, the sixteenth part of this in breadth, and weighing 120 Roman pounds. This gives for the thickness of the lead, exactly the quarter of an English inch. In lower situations, where the stress against the sides was greater, the pipes appear to have been made proportionably stronger. "The quantity of water delivered from the cisterns, was regulated by the dimensions of the spouts, termed calices. These formed a series of twenty-five different kinds, which served as moduli. Their diameters were sometimes reckoned by ounces, or the twelfth part of a Roman foot, but more commonly by quarter digits, or the sixty-fourth part of a foot. The quinaria seems to have been considered as the standard, and its width must have corresponded to the 906 part of an English inch. The ajutage or length of all these spouts was the same, being twelve digits, or three-fourths of a Roman foot, and therefore equal to 87 English inches. Prony conjectures from very probable grounds, that such was also the altitude of a column of pressure above the mid dle of each orifice. This estimate gives 1979 cubic feet for the quantity of discharge of a denaria, in the space of twenty-four hours. "Leaden pipes were likewise employed to carry water across vales, and over eminences. But it behoved to erect, at several incurvations, columnaria, or chimneys, to give vent to the air which might collect and gorge up the passage of the water. Such funnels required to be raised to near the height of the fountain head. "Vitruvius, however, joins with Palladius and Columella, in recommending pipes of earthenware, as not only cheaper but more wholesome than those of lead. They could be formed thicker, if necessary, and might be farther strengthened and secured, they said, by an outer coating of lime worked up with oil. But such pipes not being glazed, it became necessary, before using them, to fill up the pores by a sort of puddling, that is to wash their inside with favilla, or fine wood ashes. "No wonder, therefore, that leaden pipes were held in little estimation among the ancient Romans. They seem to have been seldom used indeed beyond the limits of the imperial city, except as auxiliaries in the smaller aqueducts. When such conduits happened to be interrupted by a narrow vale, instead of joining them by an arch thrown over the gap, the connection was sometimes formed by an inverted syphon of lead, carried on the one side down to the bottom, and brought up on the other."* This comprehensive and instructive summary furnishes ample materials, for estimating fairly and accurately, the scientific knowledge, and practical skill, possessed by the Romans, for the effective accomplishment of their plans. Such an assemblage of facts demonstrates that their * Leslie's Elements of Nat. Philosophy, p. 416. |