l36 Mediaeval Military Architecture in England. White Tower, built in great haste, is of rubble, rudely coursed, with very open joints ; but the plinth, quoins, and pilasters seem to have been of Kentish rag, dressed as ashlar, and also open jointed. Mailing is an excellent example of very early Norman rubble, with open joints, and this may also be said of a part of the adjacent abbey church, and perhaps of the tower of the parish church. Guildford contains a good deal of herring-bone work ; Chepstow and Penllyne a little. Col- chester is partly built of old Roman materials, chiefly brick, and contains some herring-bone work. In the chalk dis- tricts flint was largely used, as at Bramber, Dover, Hastings, Canterbury, Thurnham, Berkhamsted, Bungay, and Walden. In the south, or near the sea, the ashlar is often in small blocks from Caen. Corfe is of excellent local ashlar, as is most of Kenilworth. Porchester is of chalk and flint rubble, faced with ashlar outside and partially inside. Hedingham is all ashlar, and altogether the finest keep in England. Bowes is a fine example of ashlar, in a local stone. Whatever Norman masonry may be in church towers, in keeps it is always sound, though often rough, and is very durable. Now and then chain courses of timber are inserted in the heart of the walls, to hold the work together till the mortar shall have set, and it has happened that the wall has been breached and the exposed timbers have been found to have rotted away, leaving cavities, as at Rochester, concerning the use of which much nonsense has been written. In considering the limited and very inconvenient accom- modation afforded by a Norman keep, it should be remem- bered that it was not meant for a residence, save during an actual siege, and that at such times it often only received the baron's armed tenants, and not his mercenaries. Indeed, the builders of some of these keeps seem to have mistrusted their own troops as much as they feared those of the enemy. The staircases and galleries are often contrived quite as much to check free communication between the several parts of the building as between its inside and its outside. Further, the excessive jealousy in guarding the entrance, the multiplied doors, the steep and winding staircases, the sharp turns in the passages, although they helped to keep out an enemy, or, if he got in, placed him at a disadvantage, also rendered im- practicable the rapid re-entry of the garrison, so that if the court or outer ward were taken by assault, the defenders had scant time to retire into the keep, which was thus liable to a coup de uiahi. Otherwise, with a sufficient and faithful garrison, and ample provision and military stores, a Norman rectangular keep was almost impregnable, so great was its
