At S. Sergius, the expedient of planning columned exedras to fill out the angles of the square beneath a domed vault had proved its utility and beauty. For the influence of the cross type we need only turn to the plan, and observe that the width across the “transepts” is exactly the same as the length included by the eastern and western hemicycles. The master builders not only designed the church, they came “and worked at every part,” and lived with their building until their death; they certainly graduated as workmen, and we hear nothing of their honours or position, only of their genius.[335] In the words of M. Choisy, “In Justinian’s time, to build was the essential _rôle_ of the architect.” Both master builders are again mentioned as working together on the occasion of the fortifications of Dara in Mesopotamia, having been injured by floods. The emperor on hearing of it at Constantinople “straightway summoned those most celebrated architects Anthemius and Isidorus mentioned before, and inquired what might be devised.” The scheme of Chryses, the engineer of the works at Dara, was however adopted.[336] The younger Isidorus who re-erected the dome of S. Sophia Procopius mentions as having been employed by Justinian in rebuilding the city of Zenobia in Mesopotamia with its fortifications, churches, baths and porticoes. “All this work was done under the superintendence of Isidorus and Joannes, of whom Johannes was a Byzantine and Isidorus a Milesian by birth, being the nephew of that Isidorus I mentioned before.” To the master builders Procopius, Paulus, and Theophanes give the names _mechanikos_, _polumechanos_, _mechanopoios_, to which other writers add _protooikodomos_--“first of the builders,” _magistros_ and _maistor_. The craftsmen appear to have been classed as _technitai_ with a foreman over each subdivision. The Latin names of the different building crafts are given both in Theodosius’ code,[337] and in the edict of Diocletian,[338] which fixed their wages. This edict is bilingual, but unfortunately the Greek synonyms for the workmen are wanting. In the description of the building of S. Sophia, Procopius speaks of the _lithologos_ or “stone-layer,” who built the big piers, Paulus and the Anonymous use _laotoros_ and _laotomos_ a “mason” and “stone-cutter,” wherever marble workers are mentioned, to which must also be added _lithoxos_ “stone polisher.” The general bricklayers, &c. are comprised as _oikodomoi_. _Tektonikos_ implies a carpenter. S. Gregory of Nyssa, in describing a church of S. Theodore, calls the craftsman who arranged the mosaic tesserae, ὁ συνθέτης τῶν ψηφίδων.