Unfortunately only two sides of this tower and the foundations of the other sides remain. The walls are only 3 feet 6 inches thick, contrasting strikingly with the castles of the 12th and 13th centuries, where the usual thickness is 10 feet, which is often exceeded. This points to a date before any great improvement had taken place in assaulting-machinery. The masonry is what French architects call _petit appareil_, very small stones, but regularly coursed. There is no herring-bone work. The buttresses, of which there are five on the front, certainly suggest a later date, from the size of the ashlar with which they are faced, and from their considerable projection (3 feet on the entrance wall, 2 on the front). There is no sign of a forebuilding. There are only two storeys above the basement. The floors have been supported on ledges, not on vaults. The doorway, a plain round arch, with bar-holes, is on the first floor;[1117] it is now only a few feet above the ground, but probably the basement has been partially filled up with rubbish. The first storey is quite windowless in the walls which remain. There are no fireplaces nor any loopholes in these two fragments. In the second storey there are three rather small windows and one very large one;[1118] they are round arched, have no splay, and their voussoirs are of narrow stones alternated with tiles. In these details they resemble the Early Romanesque, which in England we call Anglo-Saxon. The Tower of London and Colchester keep are some seventy or eighty years later than that of Langeais, and if we attempt to compare them, we must bear in mind that Langeais was the work of a noble who was always in the throes of an acute struggle with a powerful rival, whereas the Tower and Colchester Castle were built by a king who had reached a position of power and wealth beyond that of any neighbouring sovereign.[1119] Langeais is but a small affair compared with these other two keeps. The larger area,[1120] thicker walls, the angle towers with their provision of stairways, the splayed windows [of Colchester], the fireplaces, the chapels with round apses, the mural gallery [of the Tower] cannot be definitely pronounced to be instances of development unless we have other instances than Langeais to compare with them. De Caumont mentions Chateau du Pin (Calvados), Lithaire (Manche), Beaugency-sur-Loire, Nogent-le-Rotrou (Eure et Loire), Tour de l'Islot (Seine et Oise), St Suzanne (Mayenne), and Tour de Broue (Charente Inf.), as instances of keeps of the 11th century.[1121] These should be carefully examined by the student of castle architecture, and De Caumont's statements as to their date should be verified. Not having had the opportunity of doing this, we will only ask what features the keeps of Langeais, London, and Colchester have in common, which may serve as marks of an earlier date than the 12th century.[1122] The square or oblong form and the entrance on the first floor are common