St. Willibrord, a Saxon noble educated in Ireland about the same time with King Aldfrid, went out thence and ultimately became Archbishop of Utrecht. Another noted scholar of the same period was Agilbert, a Frank by birth, who spent a long time in Ireland for the purpose of study and afterwards became Bishop of Paris.[13] We have seen how the Office of St. Cathaldus states that the school of Lismore was visited by Gauls, Angles, Scotti, Teutons, and scholars from other neighbouring nations. The same was more or less the case with Clonmacnois, Bangor, and some others of the most noted of the Irish schools. It was not in Greek attainments, nor in ecclesiastical studies, nor in Latin verses alone, that the Irish excelled; they also produced astronomers like Dungal and geographers like Dicuil. Dungal's attainments we have glanced at, but Dicuil's book--_de mensura orbis terrarum_--written about the year 825, is more interesting, although nothing is known about the author's own life, nor do we know even the particular Irish school to which he belonged.[14] His book was published by a Frenchman because he found Dicuil's descriptions of the measurements of the Pyramids a thousand years ago tallied with his own. "Antioch," writes Professor G. Stokes, "about A.D. 600, was the centre of Greek culture and Greek erudition, and the chronicle of Malalas, as embodied in Niebuhr's series of Byzantine historians, is a mine of information on many questions; but compare it with the Irish work of Dicuil and its mistakes are laughable." A great deal of his work is founded of course upon Pliny, Solinus, and Priscian, but he shows a highly-developed critical sense in comparing and collating various MSS. which he had inspected to ensure accuracy. What he tells us at first-hand, however, is by far the most interesting. In speaking of the Nile he says that:-- "Although we never read in any book that any branch of the Nile flows into the Red Sea, yet Brother Fidelis told in my presence to my master Suibhne [Sweeny]--to whom under God I owe whatever knowledge I possess--that certain clerics and laymen from Ireland who went to Jerusalem on pilgrimage sailed up the Nile a long way."