familiar with all the classical and ecclesiastical literature which was calculated to throw any light on that vexed question. The consequence of this study was that the Irish monks became the greatest astronomers of the seventh, eighth and ninth centuries. It is enough to read the Paschal Epistle of Cummian Fada (d. 661)[133] or the famous letter of Dungal who in 810 A.D. was asked by Charles the Great to explain the double eclipse of the sun which was supposed to have occurred in that year,[134] to be convinced of the superiority of their scholarship. ORGANIZATION OF THE IRISH MONASTERY ON A TRIBAL BASIS: In marked contrast with the other Western churches which were organized on a national and episcopal basis the Irish Church was tribal and monastic. This was quite natural. The conversion of the chieftain was followed by the conversion of the clansmen and a tribal character was thus given to the nascent church.[135] At an early date the Irish Church took a monastic form which accorded so well with the native social system. The abbot became chief of an ecclesiastical clan most of whose members were descended from the same common ancestor as the abbot himself. No wonder the native name for the monastic community was _muintir_, usually translated _familia_.[136] Even the successor of the abbot—the _coarb_, literally heir—could often claim lineal descent from the same chieftain as the abbot whom he succeeded. Of course, as the abbot was unmarried, there could be no direct lineal succession from the first abbot, but there was a succession in the manner indicated. There was thus a close resemblance between the succession of the abbot and that of the chieftain. The successor of the chieftain was not necessarily his son, but a member of the clan by whom he was selected on account of his personal fitness for the position. In the case of the monastery of Iona it has been noted that Columba and thirteen of his successors were descended from a common ancestor, an Irish chief named Conall Gulban.[137] The monastic family consisted of _fratres_: those of tried devotion were called _seniores_; those who were strong for labour were _operarii fratres_; and those under instruction were _juniores_, _alumni_, or _pueri familiares_. Besides the congregation—_collectio_—of professed members there were usually present _peregrini_, sometimes called _proselyti_, _poenitentes_, or _hospites_ whose sojourn was of varied duration.[138]