When Nicolas V. had ascended the papal throne, Valla received from that liberally-minded pontiff an invitation to fix his residence in Rome. He accordingly repaired to the pontifical court, where he was honourably received, and employed in translating the Greek authors into the Latin tongue.[431] Soon after his arrival in Rome, the following circumstance gave rise to the irreconcilable enmity which took place between him and Poggio. A Catalonian nobleman, a pupil of Valla, happened to be possessed of a copy of Poggio’s epistles. This book having fallen into Poggio’s hands, he observed on its margin several annotations, pointing out alleged barbarisms in his style. Fired with indignation at this attack upon his Latinity, and precipitately concluding that the author of these criticisms could be no other than Valla himself, whose _Libri Elegantiarum Linguæ Latinæ_ had gained him the reputation of an acute grammarian, he had immediate recourse to his accustomed mode of revenge, and assailed the supposed delinquent in a fierce invective. In this work he accused Valla of the most offensive arrogance, which, as he asserted, was manifested in his animadversions on the style of the best classic authors. Poggio then proceeded to examine and to defend the passages which had been noted with reprobation in the young Catalonian’s copy of his epistles. Collecting courage as he proceeded, he arraigned at the bar of critical justice several forms of expression which occur in Valla’s _Elegantiæ_. Alluding to Valla’s transactions in the court of Naples, he impeached him of heresy both in religion and philosophy, and concluded his strictures by the sketch of a ridiculous triumphal procession, which, as he asserted, would well befit the vanity and folly of his antagonist.[432]