In this wall, which went nearly round the city, the Roman bricks are interlayed in separate courses between layers of flints. The quantity of mortar between the bricks is nearly equal to the thickness of the bricks themselves. Four layers were discernible; the lowest tier had four bricks, the next three, and the two uppermost had each of them two. The distances between the courses of bricks, which were filled up with flint and mortar, were two feet and eight inches. The bricks were an inch and an half, or an inch and a quarter thick; their lengths were from 12 to 18 inches, viz. 12, 16, 17 and 18 inches. Having no authority to pull down the wall, their depth could not be measured.