It will thus be seen that Lincoln Castle, as regards its earthworks, belongs to that type of English fortress in which the mound has its proper ditch, and is placed on one side of an appended area, also with its bank and ditch. The general area, which at Windsor, Arundel, and Berkhampstead is oblong, to suit the contour of the ground, is here, as at Tonbridge, Tickhill, and Clare, where the ground is not strongly marked, nearer to a more solid figure, of which, in this case, two sides and the contained angle are governed by the line of the old Roman wall. In general, these fortresses are much alike, and all belong to that class of burhs known to have been thrown up by the English in the ninth and tenth centuries, and at about the same time by the Scandinavian settlers in Normandy. Two mounds, though not unknown, are uncommon. At Lewes there are two, one at each end of an oblong enclosure. At Hereford, besides the keep mound, now removed, there is a mass of earth at the north-east corner of the outer area, a part of the bank, and at Cardiff also, besides the keep mound, are two masses of earth upon the north-east and south-east corners of the enclosure, forming, which there the keep mound does not, a part of the bank. Such subordinate mounds are not uncommon in earthworks of all ages, and are totally distinct from the grand isolated moated mound which gives character to the earthworks of the ninth and tenth centuries, both in England and Normandy. [Illustration: PLAN OF LINCOLN CASTLE. Wyman & Sons, Gᵗ. Queen Sᵗ. London.]