large and deep valley of Bonnan, being underground twice and having three bridges on its course, the last of which, the sixteenth on the course of the aqueduct, ends in a reservoir on the edge of the valley.  Only one of the openings by which the siphons, of which there were probably ten, started from the reservoir is now left.  The bridge across the valley below had thirty arches, and was about 880 ft. long by 24 ft. wide.

A number of the arches still remain standing, and, the pillars of the arches were constructed of transverse arches themselves.  The work consisted of concrete, formed with Roman cement so hard that it turns the points of pickaxes when employed against it, with layers of tiles at regular intervals.  The surface of the concrete is covered with small cubical blocks of stone placed so that their diagonals are horizontal and vertical, and forming what is known as opus reticulatum.  After crossing the bridge the pipes were carried up the other side of the valley into a reservoir, of which little remains, and then the aqueduct was continued to the next valley, passing over three bridges in its course.  This valley, that of St. Irenee, is much smaller than either of the others, but nevertheless it was deep enough to necessitate the construction of inverted siphons, of which there were eight.  Leaving the reservoir on the other side of this valley, the aqueduct was carried on a long bridge (the twentieth on its course) which crossed the plateau on the top of Fourvieres and opened into a large reservoir, the remains of which are still to be seen on the top of that hill.

From this reservoir, which was 77 ft. long and 51 ft. wide, pipes of lead conveyed the water to the imperial palace and to the other buildings near the top of the hill.  Some of these lead pipes were found in a vineyard near the top of Fourvieres at the beginning of the eighteenth century, and were described by Colonia in his history of Lyons.  They are made of thick sheet lead rolled round so as to form a tube, with the edges of the sheet turned upward, and applied to one another in such a way as to leave a small space, which was probably filled with some kind of cement.  These pipes, of which it is said that twenty or thirty, each from 15 ft. to 20 ft. long, were found, were marked with the initial letters TI.  CL.  CAES.  (Tiberius Claudius Caesar), and afford positive evidence that the work was carried out under the emperor Claudius.  Lead pipes, constructed in a similar manner, have also been found at Bath, in this country, in connection with the Roman baths.  The great difference between this aqueduct and those near Rome arises from the fact that, instead of being carried across a nearly flat country, it was carried across one intersected with deep ravines, and that it was therefore necessary to have recourse to the system of inverted siphons.  There can be no doubt that the inverted siphons were made of lead, although no remains of them have been