Virgo, 2,504 " Julia, 1,368 " 7008 Claudia, 4,607 17,567 17,567 quinariae 24,575 The quantity of the Alsietina is not given, but it was computed to deliver about 400 quinariae making altogether, 25,000 quinariae.* * The quinaria is equivalent to about 2000 cubic feet, of about 7 gallons each.

20 PRELIMINARY ESSAY.

But of this immense abundance, not three-fifths, according to the public registers, were lawfully delivered, the rest being surreptitiously abstracted by individuals. The whole daily supply shown by these registers, was 14,018 quinarise, equal to about 28,000,000

cubic feet, or one hundred and ninety-six million gallons ! Notwithstanding this prothe aqueducts, which Strabo compares to rivers digious abundance of water supplied by flowing along the streets and through the sewers, the use of well and spring water was not abandoned.

The population of Rome* at the period when Frontinus wrote, between 70 and 80 years after the Christian Era, may be taken at between 1,000,000 and 1,200,000. Assuming it at one million, the daily supply of water from the aqueducts to each inhabitant, was 196 gallons !

The supply of London, now containing more than two millions of inhabitants, is computed at 37,000,000 gallons, or about one-fifth of that of ancient Rome. The city of Paris is still more deficient in this resource.

The distribution of the water along its course, as well as throughout the city, was regulated with scrupulous care. Besides the piscina limosa, or purify ing reservoir usually placed at the mouth of each aqueduct, there were frequent castella, or wells along the line, which both aided in the process of purification, and permitted water to be drawn occasionally along the route, for the irrigation of fields and gardens, and the supply of baths. The main castellum was that in which the aqueduct terminated, and whence the water was distributed through the city.