Or, boiled in a like vessel, and left to cool, if, when poured off, there shall be neither sand nor earth left at the bottom, it may be deemed good. Again, if vegetables boiled in it be rapidly cooked, it is an indication that the water is pure and wholesome."* For 441 years after the building of their city, the Romans were content to use the water furnished by the Tiber, (the yellow Tiber,t as Horace calls it) by wells, or fountains. * t Ode 2 r lib. E. Vitruvius, chap, v., lib. viii.

PRELIMINARY ESSAY. 13

To the latter especially, as in some measure sacred, they showed a marked preference, and believed that bodily infirmities were cured by the salubrity of the waters from such sources ; but when the convenience and abundance of supply from aqueducts was once

experienced, the enterprise, wealth, and luxury of the great city, very soon multiplied without a figure, them, so that in the reign of Nerva, they were nine in number, pouring, rivers into every part of Rome.

Of these magnificent and beneficial structures, we have quite a detailed account left us by Sextus Julius Frontinus a man of consular dignity, who was appointed by Nervdj superintendent or chief commissioner of the Aqueducts an office of great dignity as well as responsibility. The curatores vel prefecti aquarum were invested with considerable authority. They were attended outside of the city by two lictors, two slaves, a secretary, Frontinus, on his appointment, very sensibly concluded, and other followers. " as he tells us at the outset of his treatise, that, considering in this as in other affairs of life, that the first thing was to know and understand what he had undertaken," he set himself about collecting and noting down in order, all that related to the history, structure, size, and defects of the aqueducts committed to his charge, the abuses to which they were liable, and the laws for their protection.