CROOKSTON CASTLE 535 THIRD PERIOD There is one square tower still existing at the north-east corner, and the remains of a similar tower at the south-east corner (Fig. 458). From the arrangement of the door, which opens outwards, and the thin- ning of the walls at the west end, it seems probable that there were two corresponding towers at the north-west and south-west angles, as shown by dotted lines on the plan of the ground floor. The plan of the castle would in this respect resemble that of Hermitage. Over the door, from the basement into the north- west tower, there is a hole or machicolation in the wall, from which missiles might be cast on assailants below. This is shown on the plan of the first floor, Fig. 456. The entrance door (Fig. 459), which is on Fl - 456B.-Crookston Castle. Springing of End Rib. the ground level, adjoins the north-east tower, and has been strongly defended with two doors and a portcullis, the inner door having the usual sliding bar, which, when drawn back, crosses FIG. 457. Crookston Castle. Vault of Basement Floor. the staircase of the north-east tower at such a level as to prevent entrance by it. The doorway projects from the face of the wall, so as
