which was improved by Sulpicius Severus in 410, and continued to be used till 457, when a longer cycle of 532 years was introduced by Victorius of Aquitaine, based upon the cycle of nineteen years; and in the year 525 the computation was finally fixed by Dionysius Exiguus on the cycle of nineteen years. By this time it was likewise held that, as the Passover was slain on the evening of the fourteenth day of the moon, according to the Jewish system of reckoning the days from evening to evening, the fifteenth, and not the fourteenth, ought to be considered as the first day of unleavened bread, and consequently Easter ought to fall on the Sunday between the fifteenth and twenty-first days of the moon; and by a canon of the fourth council of Orleans, held in the year 541, it was directed that the Easter festival should be observed by all at the same time, according to the tables of Victorius.[11] These changes in the mode of computation in the Western Church took place after the connection between Britain and the rest of the empire had ceased, and when the British Churches were left in a state of isolation. They therefore still retained the older mode of computation, which had been once common to the whole Western Church; and thus it came that when Columbanus went on his mission to Gaul he found the continental Churches celebrating the festival of Easter on the Sunday between the fifteenth and twenty-first days of the moon, calculated on the cycle of nineteen years, while the British and Irish Churches celebrated the same festival on the Sunday between the fourteenth and twentieth days of the moon, calculated according to the cycle of eighty-four years; the difference in the days of the moon causing an occasional divergence of a week, and that of the cycles a possible divergence of a month.[12] The prelates of Gaul seem to have eagerly caught at a ground upon which they could charge these strange missionaries, who had taken such a hold upon the country, with following practices at variance with the universal Church, and thus pursuing a schismatical course. A council was summoned for the purpose of considering what steps they ought to take with regard to these strangers; but Columbanus, though probably included in the summons, contented himself by sending a letter, which is still extant, addressed to ‘our holy lords and fathers or brethren in Christ, the bishops, presbyters, and other orders of Holy Church,’[13] in which he vindicates the mode of keeping Easter which he had received from his fathers, according to the cycle of eighty-four years, refers to Anatolius as having been commended by Eusebius and St. Jerome, and denounces the change made by Victorius as an innovation. He claimed his right to follow the course derived from his fathers, and remonstrated with them for endeavouring to trouble him on such a point. What the result of this synod was we do not know; but it was followed by an appeal by Columbanus to the Pope himself.