The White Tower is somewhat irregular in plan, for though it looks so square from the river its four sides are all of different lengths, and three of its corners are not right angles. The side towards which we approach is 107 feet from north to south. The south side measures 118 feet. It has four turrets at the corners, three of them square, the fourth, that on the north-east, being circular. From floor to battlements it is 90 feet in height. The original entrance was probably on the south side, and high above the ground, being reached as usual in Norman castles by an external stair which could be easily removed in time of danger. Another or the same entrance led from an upper storey of the palace. The interior is of the plainest and sternest character. Every consideration is postponed to that of obtaining the greatest strength and security. The outer walls vary in thickness from 15 feet in the lower to 11 in the upper storey. The whole building is crossed by one wall, which rises from base to summit and divides it into a large western and a smaller eastern portion. The eastern part is further subdivided by a wall which cuts off St. John's Chapel, its crypt, and its subcrypt, each roof of which is massively vaulted. There is no vaulting but a wooden floor between the storeys of the other part. There are several comparatively modern entrances. A short external stair leads to a staircase in the thickness of the wall on the south side, by which we approach the Chapel. A brass plate on the right refers to some children's bones found in the reign of Charles II. They were identified, somewhat conjecturally, with the remains of Edward V and his brother who disappeared so mysteriously at the accession of Richard III, and were removed to Westminster Abbey in 1678. Ascending the stair we come to the passage which led from the palace to _The Chapel of St. John_ (Pl. VIII). The chapel is the largest and most complete now remaining in any Norman castle, and must have seen the devotions of William the Conqueror and his family. It is 55 feet 6 inches long by 31 feet wide, and 32 feet high, and is vaulted with a plain arch. There are four massive columns on either side and four in the apse. The south aisle, as we have seen, communicated with the palace, and an upper aisle, or gallery, similarly opened into the _State Apartments_