Page:Roman Manchester (1900) by Charles Roeder.djvu/29

Rh that is, along the northern side, and throws the underground and surface water into the depression or valley formed between the castrum and Camp Street.

Now at the time the Romans perched their castrum on the northern banks of the Medlock Bridgewater Street formed part of an open valley mingling with stretches of marshy swamp, moorland, patches of heather, sprinkled with some clear pools here and there, and traversed by little rills speeding down from the higher adjacent levels. They had to dig their northern wall along the edges or margins of this marshy ground, and we, therefore, find the foundation walls on that side by necessity sunk down into the swamp. We have seen already that under the foundation of the northern wall on the eastern side of Collier Street a large accumulation of heterogeneous land shells were discovered by me in the green marshy clay beneath, which clearly affords another proof of the existence of an old marshy ground.

At the northern or outer side of the wall this soft marshy bed is cut down to a slope of 45 degrees. At trench No. 2, 2 feet to 3 feet away from the wall, and at the very bottom of the first fosse, a solid causeway was struck in May, 1897, running apparently parallel to the wall. It was formed of large dressed blocks of compact, heavy, white millstone grit, measuring 11 inches by 7 inches by 6 inches each. The upper face of the stones was convex, and they had the hard Roman mortar still adhering to its two sides, the bottom had no mortar, and was rough. The width of this causeway was 2 feet 7 inches. It was laid on the marshy ground, and the navvies had great difficulty in breaking it up, in