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venters, and the first length of the rising pipe. By this attention the tubes in their ascentand descent were never put out of order. In aqueducts there is generated a great rush ofair, says Vitruvius , of force sufficient to break stones, unless the water is softly and sparinglylet down from the head, and unless in elbows and bending joints it be restrained by meansof ligatures or a weight of ballast.

When the water was first let down from the head, ashes were put in, which closed thejoints where they were not sufficiently coated ; earthen pipes were considered in someinstances preferable, as when damaged, almost any one could repair them, and the waterconducted by them wjis of greater purity. The Romans preferred earthen vessels tosilver at their daily meals, the water preserving its flavour better in them.

When wells were dug, they were steined or walled round, to exclude filtration, and tanksand cisterns were frequently used to collect the rain, which were carefully built with thepurest and roughest sand and broken flint,among which no single piece weighed more thana pound; very strong lime and sand, mixed inthe proportions of five of sand and two of lime,formed the mortar. The flints combined withthe mortar lined the sides and bottom of theexcavation. Several divisions were made inthese cisterns coated with cement, and the waterspassing from one to the other, depositing its im-purities, was rendered wholesome and fit for use.

Pliny , lib. xxxi. cap. 31., informs us, thatwhen water is to rise, the pipes must he madeof lead, and that water will always ascend by itself to the height in the castollum from whichit is delivered, or, in other words, find its own level; but that wherever there is a bendin the pipe, the lead must be increased in thickness at that place.

Fire Engines _There can be no doubt but that the Romans had contrivances by which

they could extinguish fires, for we learn by one of Pliny’s letters to the Emperor Trajan ,that when the town of Nicomedia, in Bithynia , was almost destroyed by fire, its ravageswere increased by the laziness of the inhabitants, and the want of a proper machine —sipho — for extinguishing the flames. When Strabo , lib. v., alludes to the subterraneanconduits at Rome , lie mentions, that all the houses had siphones or water-pipes, and whichprobably could be applied to put out any accidental fire. Apollodorus, the architect , inliis description of warlike machines, mentions the sipho for extinguishing fire, and observes,that if it is not at hand, leathern bags filled with water may be fastened to hollow canes,in such a manner as by pressing the bags the water may be forced over the flames. Sucha sipho might throw water to a great height, and in the fourth century they were made useof. The Romans had many ordinances for the extinguishing of fires, and Ulpian , Digest ,xxxiii. 7. 18., when mentioning those things which ought to belong to a house when sold,names the siphones , which have been supposed to be fire-engines. Seneca observes that theheight of the houses at Rome rendered it impossible to extinguish fire, in consequence ofthe narrowness of the streets.

Form of the Pipes. These were not truly cylindrical, as has been commonly supposed,but their section that of a pear; the upper part being gathered in formed an edge whereit was soldered. On some found is inscribed the name of the maker, and the situationthey occupied. Where strength was required, over the joint was soldered a capping orridge, hooped round with narrow cuttings of lead.

Pliny gives us (lib. xxxiii. cap. 30.), the method adopted for soldering the differentmetals; for gold, borax was used; for iron potter’s clay (argilla); alum for brass; resinfor lead; and in lib. xxxiv. cap. *18., the same writer tells us that tin is used as a compoundto solder conduit pipes, and that the best common black lead, beaten with hammersinto sheets for the making of the conduit pipes, was brought from Britain , where it wasfiAmd on the surface of the ground in great abundance.

To stop the water in the pipe, or to turn it on, a metal cock was used, and manyhave been found, similar in their construction to those of modern date. Vessels resem-bling a deep pan of lead are met with, supposed to be for the purpose of measuring off acertain quantity of water.

Pipes of earthenware or terra cotta, called tubuli fietiles, arc found in the walls of thebaths and Coliseum of various diameters, none less than two fingers or digits, which wasrequired to prevent any accumulation of deposit.

Canales lignei, or wooden pipes, were common in ordinary structures, on account oftheir economy. Piscina and cisterns were differently constructed for the reception ofwater : that called the Sette Sale, which served the baths of Titus, is one of the most perfect.

The Sette Sale , where the water was collected for the supply of the baths of Titus,contains nine large reservoirs; it is situated on the Esquiline Hill , in a lonely vineyard nearthe Palombara. By seme writers it is assumed, that the quantity of water they contained

m 4

Fig. 185.

PLAN OP WELL.