When we attempt to reconstruct the monastic horarium we are baffled, in the later as in the earlier middle ages, by a lack of reference to hours of the day. Generally speaking, however, few changes were made during the period under review. One such may have been an advancement of the hour of the night-office to midnight in large houses, consequent upon the practice, now becoming general, of retiring to the dormitory for sleep in the interval between Mattins and Lauds. As the latter office began before dawn a difficulty was caused by the length of the night office on great feasts in the early summer, and a solution was found by throwing Mattins back to the previous evening, thus giving on those nights a single period of rest after the office, supplemented by the normal summer siesta. The only other change was in the morning, where at some houses the morrow or chapter Mass was advanced from 9 a.m. to c. 7.30 or 8 a.m. in order to provide students of theology with a longer unbroken period of work. On the very eve of the dissolution the course of the day at Durham appears before us in its main outlines: the midnight Mattins, the sung Chapter-Mass at 9.30 followed by the chapter; the High Mass at about 10.30 followed by dinner and reading till Vespers at 3; supper at 4.30 followed by a conference, and Compline followed by the Salve at 6.