Near this was placed the south tower, which, being undermined a few years since by the force of the water running down the vallum after some very heavy rains, is fallen on one side near its former situation, but remains perfectly entire. The north tower having met with a similar accident is reclined from the wall at the top about six feet, has drawn a part of it, and caused a breach near it. The whole area of the station contains four acres and two roods, and, including the walls, five acres, two roods and twenty perches. The mortar made use of by the Romans in this work was composed of lime and sand, unrefined by the sieve, and incorporated with common gravel and small pebbles. It was used two different ways; one cold, in the common manner now in use; the other, rendered fluid by fire and applied boiling hot. From the artful mixture of both in the same building, and from the coarse materials of the composition, this cement is extremely hard and durable, very difficult to break, and for several days indissoluble in water. The Romans, raising the wall to a convenient height with the former sort, at the end of every day’s work poured the latter upon it, which immediately filled up the interstices, and when cold, proved a most powerful adhesive. The Roman bricks made use of at Burgh are of a fine red colour and very close texture; they are about one foot and a half long, one foot broad, and an inch and a half thick. It does not, however, appear that the Romans had any exact standard for the size of their bricks: in different stations their dimensions are considerably varied. We ought, however, to observe that either in the choice of their materials, or in their method of preparing them, they far excel those of later days, being much harder and less porous than ours, and for durableness more resembling stone, for which they were undoubtedly substituted. In the area of this camp, and in many of the fields around it, vast numbers of Roman coins have been, and are still, found; but none of them rise higher than the reign of Domitian, {19} and the generality of them are much later. Few are found of any other metal than copper, and they are seldom curious, either for design or execution.