§ 58. An important variation of plan in the western range occurs in three prominent instances. In each case the peculiarity is determined by the fact that a river forms the western boundary of the site, and afforded special convenience for drainage, while in two cases, at Durham and Worcester, the western range was on the side furthest from the town houses near the monastery. (1) At Worcester the cellarage was beneath the frater, and there was no western range parallel to the cloister. The dorter, with the common house below, was at right angles to the west walk of the cloister, and the rere-dorter was at the further end of this building next the river. A passage between the common house and the church led to the infirmary. (2) At Durham the older dorter and common house seem to have been, as at Peterborough, in the eastern range and its southward extension, next the chapter-house. But in the thirteenth century a long range was built at the back of the west walk. The great dorter occupied the whole of the upper floor. Its southern end, which crossed the west end of the frater range, was appropriated to the novices; and a stair into the cloister, close to the church, at the northern end, served for day and night use alike. The vaulted ground-floor next the cloister was divided into a treasury next the church and a common house. In the bay at the junction of the south and west walks a passage led through the range to the infirmary, which, as at Worcester and for the same reasons, was on the west side of the monastery. The bays beyond this contained the cellar and buttery, now known as the crypt, with entrances at one end from the infirmary and at the other from the cellarer's checker or office and the kitchen buildings in the outer court. A part of the old eastern range next the chapter-house was used as a prison for refractory monks, while the place of the rest was taken by the prior's lodging, now part of the deanery. (3) In the Premonstratensian house of St Agatha, the dorter was on the first floor of the western range and extended southwards, as at Durham, across the west end of the frater: its stair descended to the cloister at the south end of the west walk, dividing the common house and adjacent cellarage from the cellarer's guest-hall, which formed the five southern bays of the dorter sub-vault. There was, however, a large two-storied annexe west of the dorter, the upper story of which seems to have been used for lodging guests of the better class, while, of the three divisions of its ground-floor, the middlemost and largest may have been occupied by their servants, with a narrow cellar on the east, and a drain, crossed by transverse arches, on the west side. The whole arrangement is quite exceptional and was probably unique; but the plan of the dorter sub-vault, allowing for some difference in use, bears a strong resemblance to the plan at Durham. [Illustration: Fig. 9. Durham: ceiling of dorter (now the chapter library).]