[Illustration: MAP OF THE AQUEDUCTS ON THE EASTERN SIDE OF ROME Whiteman & Bass, _Photo-Litho’ to the Queen_, 236, Holborn] This map is reduced by photography from one made for this work on a very large scale, which was thought necessary in order to shew the line of the course of each aqueduct, which, being to a large extent subterranean, are not shewn in the usual maps of the country. In the immediate neighbourhood of Rome the lines are so complicated that they could only be shewn on this large scale. (At the Tor Fiscale, for instance, they remind English travellers of the railways at Clapham Junction near London. There are many coincidences between the aqueducts and the railways; both are carried at different levels in order to cross each other; both are in some parts in tunnels, and in other parts carried on embankments, or on arches). This map was made by Signor De Mauro, an engineer and surveyor, who took much interest in the work, and is generally very careful and accurate, under the direction chiefly of Dr. Fabio Gori, who is a native of Subiaco, near which the principal aqueducts have their sources. The author of this work went with them from time to time to verify what they had done, but as it was a work of several months, and necessarily done in the summer, it was not practicable for him to do more than to go to the source of each aqueduct and follow it down to its mouth. The large map, which covers one side of a room, being 135 ft. long and 90 ft. wide, has been reduced by photography to three different sizes; the first makes eighteen photographs of the usual size, called the “normal size,” and the whole on this scale is about 15 ft. long and 10 ft. wide; this again has been reduced to two sheets[238], 21 ins. long and 14 ins. wide; and then to the same size as this outline; but on this small scale the lettering requires a powerful magnifying-glass, and therefore the bare outline has been taken from it to shew the general features of the line of the great aqueducts. The reservoir at the source of each is marked by a dark circle, and from each of them the line can be traced into Rome. Within the walls a separate and careful examination was required, as so much of the work is subterranean; this examination has been made, and the line of each of the aqueducts has been traced to its mouth. It will be observed that the _specus_ or conduit of each aqueduct is of a separate form, and this was no doubt necessary to distinguish one from the other, as they frequently intersect and cross one another in a very singular manner, and in case of repair being necessary, it would have been very difficult for the workmen to know which aqueduct was at fault, or how to find the part that wanted repair, without this arrangement.