These letters are in any case the most important evidence for the fast of forty days before Easter. The first of them, for the year 329, is satisfied with appointing “a holy fast of six days” from the Monday to the Saturday in Holy Week;[193] the second, however, for 330, and all the following require a fast of forty days, beginning on the Monday of the sixth complete week before Easter.[194] The Festal Letters give no direct explanation of how, and for what reason, the six days’ fast was changed into a fast of forty days. However, the covering letter which Athanasius sent along with his eleventh Festal Letter, written from Rome in 339, throws some light upon the process. He writes, namely, to Serapion, first Abbot and then Bishop of Thmuis, that he may announce the fast of forty days to his brethren and impress upon them the necessity of the fast, “lest, when all the world fasts, we only who live in Egypt be derided for not fasting.” This warning is repeated with still greater emphasis: Serapion is to instruct those under him that they must fast forty days,[195] which seems to show that the custom of fasting for forty days was not yet in force in Egypt, though elsewhere it was universally observed, and especially in Rome. At the conclusion of the nineteenth Festal Letter is found a sharp reproof of those who disregarded the fast.[196] This is the forty days’ discipline (ἄσκησις) observed during the six weeks before Easter according to Eusebius.[197] The Gallic pilgrim, already so often quoted, gives the following minute information concerning the manner in which the fasts were observed in Jerusalem in the fourth century. The preparatory period before Easter lasted eight weeks, not forty days, as in Gaul, and all the days of the week, Saturday and Sunday excepted, were fasted. Holy Saturday was an exception to this rule, being kept as a fast. Thus there were in all forty-one fast days, which were called in Greek ἑορταί; in Latin, _feriæ_. On Wednesday in Lent, the Psalmody was performed as on Sunday, and the bishop read the appointed Gospel, but the Mass (_oblatio_) was offered only on Saturday and Sunday. On certain days processions were also made to different churches which lasted until eleven o’clock.