A soum consists of a cow and her progeny; in some places the cow and her calf only: in some a cow, her calf, her one-year-old progeny (called a _stirk_) and her two-year-old _quey_; in other places again, the cow, calf, stirk, quey and a three-year-old heifer. At four years old the heifer becomes a cow, and so originates a fresh soum.
In making souming calculations, it is assumed that one cow is equal to two queys or to four stirks or to eight calves, or to one heifer and one stirk. Also one cow is equal to eight sheep, or to twelve hoggs (one-year-old sheep) or to sixteen lambs or to sixteen geese. One mature horse is equal to two cows; also to eight foals, or to four one-year-old colts or fillies, or to two two-year-olds, or to one three-year-old and one colt or filly. The cow is entitled to her calf; and if one tenant has two cows without calves they are entitled to take one stirk instead.
Those tenants who are found at the souming to have overstock must either buy grazing from a tenant who has understock or may be allowed by the community to let the overstock remain on the grass till he can dispose of it. In that case payment must be made, according to a recognised code, into a common fund which is used to buy bulls or tups or for some other common purpose. The souming is amended at Lammas, and again at Hallowtide.
In Lewis and Harris similar arrangements with regard to stock obtain among the _crofters_, the amount of stock allowed to each crofter being regulated according to the rent paid.
During the early summer the herds are put at night into enclosures, according to the species, and two tenants, chosen in rotation, keep watch to prevent them from straying over the open fields. If they escape, the watchmen are fined and have to make any damage good, but the fines, and the amount assessed for damages, both go into the common fund.
Early in June, the tillage being finished, the people go to the hill grazing with their flocks. The scene is vividly described by Mr. Carmichael, the general excitement, the men shouting directions, the women knitting and chatting, the children scampering about. Sheep lead the procession, cattle come next, the younger ones preceding the older, the horses follow. Implements and materials are carried to repair the summer huts. When the grazing ground is reached the huts are repaired, fires lit, and food cooked. The people bring forward their stock into an enclosure, and the constable and another man stand at the gate of the enclosure and count each man’s stock separately to see that he has brought only his proper souming. Then the cattle are turned out to graze, and the “Shealing Feast” is celebrated by the singing of hymns and the eating of cheese. The summer huts are of a beehive shape, and are sometimes constructed of stone, and sometimes of turf and frail materials.[85]