The superstructure of Cradle Tower is said to have formed a part of the palace quarter, and the view of 1597 shows it as a water-gate, with a square turret on its west flank, where was the supposed staircase. It shows also, west of this, a considerable tower extending across the ward, here very narrow, to the Lanthorn Tower, and which no doubt contained the Lanthorn Gate. The details of Cradle Tower are rather Decorated than early English; and if, as is historically probable, it be the work of Henry III., it must be late in his reign, and was perhaps completed by his son. Owing to the cumbrous character of the sluices and gates of St. Thomas’s Tower, state prisoners were sometimes admitted by this gate, then fitted with a cradle or drawbridge. St. Thomas’s Tower, better known from its ancient function as Traitors’ Gate, is the water-gate of the Tower, and also contained and commanded the communication between the Thames and the main ditch. It is, in fact, a barbican, and a very singular one, placed astride upon the ditch, here 40 feet broad, and perforated by a passage leading from the river. It stands considerably west of the south front, being in advance of the Bloody Tower 30 feet, the breadth, at this point, of the outer ward. The quay, in front of this tower, is traversed by a channel, 28 feet broad and 13 feet 6 inches deep, partly arched over and newly lined with granite, which opens from the Thames, through an archway 21 feet broad, into a rectangular basin or pool, 66 feet by 40 feet, and 18 feet deep, lined and paved with stone, and containing, when the gates are opened, about 8 feet of water at high water. A flight of steps from the water, on the inner or north side of this basin, landed the prisoner within 30 feet of the gateway of the inner ward. The tower proper is placed above the outer 18 feet of this basin, but its side walls are prolonged backwards, so that both the front and sides of the basin are protected. The south wall, 9 feet thick, is pierced below by a low-browed water portal, already mentioned, beneath a drop arch, ribbed and chamfered. Between the ribs is a groove, 6 inches broad, for an iron sluice or portcullis, worked in the building above; and in the jambs are two holes, 6 inches diameter, lined with iron, for the passage of a chain. Within this, on the inner face of the portal, were folding gates opening inwards. [Illustration: ST. THOMAS’S TOWER. DETAIL OF RING STONES.]