This kind of masonry was bound, at every four feet of its height, by two courses of "great bricks," each brick being 22 inches square, and two inches thick. The angles of the piers, formed of small square slabs of stone, offered, in many instances, an insufficient resistance to the lozenge masses which they terminated, and their displacement has been apparently the main cause of the ruin of the greater number of the piers, for these have been formed by a sort of encasements, of the thicknesses of four feet of the

opus reticulatum, without being properly bonded by stones large enough at the quoins. The arches are semi-circular ; the arch stones are slabs (thick slates) of stone, three inches " thick, alternating with a great brick ;" the extrados of the arch is finished by a row of bricks, which forms a fillet ; on this fillet is laid a double horizontal row of bricks, which runs through the entire length of the aqueduct, without, however, forming any projection. It is upon these bricks, as a pavement, that the water channel is laid, or bedded.

Of the arcades forming that part of the aqueduct called Langoneau, only seven piers remain, arid these of the common reticulated masonry. The valley between Soncieu and Chaponost is about 200 feet deep. Five ranges of arcades, placed one over the other, for a length of 2400 feet, conducted the water across the valley the valley through which ;

the river d'Izeron flows, between Chaponost and St. Foi, is nearly 300 feet deep, and was crossed by a series of arcades having eight ranges in height. The third valley, formed by the small hill of St. Foi, and that of Fourvieres, had three ranges of arcades.