The Water Supply of Rome

1874

In the course of a lecture on Roman antiquities, delivered at the Royal Institution, London, Mr. J. H. Parker said: The celebrated Aqua Marcia has recently been again brought into Rome, and is rapidly coming into use, being considered the finest drinking water in the world, always cool even in the hottest weather. On the river Anio itself, where a fine cascade falls over the rock, there is a deep rocky gorge; and here great engineering works were made in the time of Claudius and Nero.

A great wall, 12 feet thick, built of large blocks of stone, was erected across the river at the lower part of the gorge, forming a dam of 100 feet high and 12 feet thick, to enclose a portion, perhaps 100 yards long, between the dam and the natural cascade; the water was made to fall over the dam, which thus became the cascade; but at one end of it a specus was made below the level of the surface of the water, so that the water must always flow through that specus, and consequently through Rome, before any of it could fall over the cascade.

This magnificent and most useful piece of engineering continued in use for centuries. It was destroyed in the fourteenth century by an ignorant monk, who was annoyed by a temporary flood in the upper country, which overflowed the meadows near his monastery, and, to relieve that, he made a hole at the bottom of the great dam. The force of the water soon carried all before it, and caused a great flood over all the lower country, even to the Tiber, and did immense mischief — even the walls of Rome were injured.

Mr. Parker said that he had not time to describe the thermae, or great public baths, to supply which most of the aqueducts were made, but he could not conclude without mentioning that the opinion, commonly entertained, that the ancient Romans were ignorant of the fact that water will rise to its level, is entirely a popular delusion. At every half mile of the aqueducts, on their course from the foot of the hills to Rome, each aqueduct forms an angle, to break the force of the water, and at that angle a great reservoir is made, with a piscina or filtering place at one end. Each piscina consists of four vaulted chambers, two above and two below. The water enters into the top of the first upper chamber; it then falls through a hole in the vault into the first lower chamber, then passes through small holes in the intermediate wall into the second lower chamber, then rises again through a hole in the vault into the second upper chamber, and then follows its course at the same level as it originally entered, depositing its mud in the lower chamber as it passed. Each piscina is therefore made upon the principle of water finding its level.

They used the large stone specus, or aqueducts, instead of ordinary pipes, because they could not depend either upon their leaden pipes or their terra cotta pipes to resist the force of such a stream of water. Nothing but the concrete stone was strong enough. At the present time, the cast iron pipes of the new company are bursting every day in the streets of Rome to such an extent that the managers of the company fear that the expense will be ruinous to them. This seems to show that the old Romans were better engineers than we are.