For instance, on the manor of Tidenham, in the time of Edward I., one serf worked for the lord for five days in every alternate week for thirty-five weeks in the year, two and a half days every week for six weeks in the summer, and three days every week for eight weeks during August and September (the three festival weeks of Easter, Christmas, and Pentecost were holidays). Then, in addition to this regular weekly work, he could also be required for extra work, commonly called boon-works or precariæ. "He made one precaria called churched, and he ploughed and harrowed a half acre for corn and sowed it with one bushel of corn from his own seed, and in the time of harvest he had to reap and bind and stack the produce, receiving one sheaf for himself on account of the half acre." And he had to plough one acre for oats. In addition, there were dues in kind--one hen at Christmas, five eggs at Easter, eight gallons of beer at every brewing, and also small payments in money, commuted, one would conjecture, for payments in kind, _i.e._ one penny for every yearling pig, and one halfpenny for those only of the half year.[24] In other cases the tenants paid dues of lambs, of fish, of honey, of clews of net yarn, of straw, &c. One of the tenants of the great monastic establishment at Glastonbury had to find thirty salmon, "each as thick as a man's fist at the tail."[25] A curious form of labour due is described in the Boldon Book. The tenants of certain manors in Durham had to build each summer a hunting-lodge for the bishop and his retinue when they came to take their pleasure in the moors in the west of Durham. At different periods and in different districts the subdivisions of the tenants vary greatly, and for complete details the reader must be referred to the special works on the subject. But two classes can usually be distinguished--(1) the villeins, who possessed oxen and worked the larger holdings (often about thirty acres--called virgates or yard lands); and (2) the cotters, who held about five acres, and whose domestic animals consisted of pigs and poultry. In addition there were often found socmen, who were personally free; and, at the other end of the social scale, slaves, who, largely through the influence of the Church, were manumitted before the end of the Middle Ages.