To make this theory of a learned migration from Western Gaul to Ireland more easily accepted, Zimmer gives a valuable collection of facts in historical evidence, showing that there was a regular course of trade between the two countries at this time and for centuries before and after it. Zimmer applies his theory to the explanation of certain remarkable facts. In the first place, he explains by it the pre-eminence in the knowledge of Latin and Greek that belonged in the following age to Irishmen and the pupils of Irishmen. Secondly, he explains by it the reference made by St. Patrick in his Confession to certain critics who despised his rusticity, _i.e._, his want of a classical grounding in Latin. St. Patrick calls these critics "rhetoricians," a term which certainly seems to imply that they belonged to a professional academic set. Zimmer thinks that these "rhetoricians" were some of the learned refugees from Western Gaul. A third fact which Zimmer explains by his migration theory is the fondness of the early Irish poets and grammarians for certain artificial super-refinements of language and grammar, and in particular for the production of a learned jargon in Irish by making deliberate changes in the form of words, substituting one letter for another, and adding, transforming or removing letters or syllables. This trait, he argues, was adopted from a certain learned school of Aquitaine, who played similar tricks with Latin, and produced by such means not one but a dozen Latin jargons; and Zimmer goes so far as to insist that the supposed Irish poet-grammarian who is named "Fercertne the Poet" was actually and personally identical with one of the chief exponents of this artificial Latinity, Virgilius Grammaticus. The difficulties I find in accepting this theory of Zimmer are chiefly two. The first is that Zimmer, when he set out to establish a novel theory, was quite as ingenious in weaving an argument as Virgilius Grammaticus could be in concocting a Latin jargon. My second difficulty is that, if such a school of foreign Latinists existed in Ireland in St. Patrick's time, I cannot understand why neither the school itself nor any individual belonging to it is mentioned in any Irish document. St. Patrick does not say that his critics lived in Ireland.