north to south (Fig. 135). The four angle towers are larger in diameter than those which are set along the walls. The intermediate bastions are perfectly regular in size and shape except the two on either side of the southern gate, from which a segment is cut off by the door openings, and the bastion immediately to the west of the same gate which has a small addition to the western part of its curve, an addition which I do not believe to be later in date though the brickwork is of a slightly different character. The southern gate is a triple opening in the middle of the wall where it would be natural to look for the miḥrâb (Fig. 138). There are remains of mouldings round the inner face of the central opening (Fig. 139). The upper part of the south wall is pierced by twenty-four windows, two of them being placed over the smaller openings of the central gateway (Fig. 122). These windows, together with the trenches in the interior of the mosque which mark the line of the columns, determine the number of the colonnades; there must have been twenty-four, each one ending against the wall between the windows. The central aisle which terminated at the main gate and was wider than the rest, was not provided with a window. The space between the colonnades was undoubtedly roofed with beams; the holes into which the large cross-beams were fitted can still be seen on the inner side of the south wall. The windows, placed with regard to the aisles, bear no relation to the position of the round bastions on the exterior of the wall. They break into them at haphazard, frequently impinging upon their sides, while in one instance a window is cut straight through a tower (Fig. 120). On the inner face the windows are covered by a cusped arch (Fig. 142). The east and west walls are broken by numerous doors. Beginning from the southern end there is first a small entrance, 1·25 m. wide, close to the angle bastion (Fig. 141). A wall about a metre in length projects from the main wall to the south of the door opening and has been connected with the top of the main wall by a section of vaulting. Immediately beyond this postern there is a large gateway 4·55 m. wide, and then another which is still larger, being 4·75 m. wide. The next door is 3·85 m.; the fifth, which is only 2·62 m., is found in the west wall alone. Then follows another of the larger doors, about 4 metres wide, beyond which there is, in the west wall only, a door 2·62 m. wide; then on both sides a large door 4·05 m. wide and a small door 1·50 m. wide. The north wall is broken by five gates, the two at the outer ends averaging 1·50 m. and the other three 4 metres in width. All the smaller doors exhibit an exceedingly curious piece of construction (Fig. 140). The brickwork of the wall runs uninterruptedly over the door opening without the intermission of arch or lintel. It is as if the door had been cut out of the wall with a knife, and the bricks above it, so far