The word ‘ḥair’ denotes a camp, a castle, or a villa.[51] The original signification does not seem to have implied solid constructions, but rather the headquarters of a desert princeling and his retainers. Such an assemblage must necessarily have been mobile. The exigencies of pasturage and the uncertainties inherent in tribal predominance, where the limits of authority cannot be expressed in terms of geographic definition, were alike unfavourable to stable residence. Joshua the Stylite[52] talks of the ḥertâ of Nu’mân ibn Mundhir as having withdrawn into the inner desert before the attack of the Tha’labites--it must therefore have been a movable camp; on the western borders there is no certain evidence that the Ghassânid princes possessed either fenced cities or garrisoned fortresses.[53] But before the dawn of the Mohammadan era the ḥîrah had begun to change its character, and the nomad encampment to develop into the standing camp and even into the city. The Ghassânids must have had a fixed establishment in the Djaulân,[54] and some of the existing ruins on the eastern frontiers of the Ḥaurân may date from their time. At Khirbet al-Baiḍâ, for example, I could find no certain trace of Roman handiwork. The plan might date from the age of Diocletian, but the decorations betray a different origin.[55] Yet I cannot place them as late as the Umayyad period. Djebel Sais I have not seen.[56] The plan of the bath recalls the arrangement of the chambers at Qṣair ‘Amrah, and it may therefore be Mohammadan. At Qaṣr al-Azraq, Dussaud found a dedication to the emperors Diocletian and Maximian, but the fortress would seem to have been rebuilt in the thirteenth century A.D.[57]