Soum

The amount of pasture that will support one cow, used to apportion common grazing.

A soum is what the land can keep, not how much land there is. One cow is the standard, and the sheep equivalent varies by district: ten in Selkirkshire and Lanarkshire, eight in the Lothians where a horse counted a full soum, and four in the Highlands.

That variation is the point rather than a defect. Ten sheep to a cow on good southern grass and four on Highland hill is an accurate statement about both places, and a unit of area would have told the commoners nothing they needed to know.

Dividing a common pasture by it was called souming, and the phrase to soum and roum meant settling each tenant’s share of grazing and of arable together. Selkirkshire even reckoned a soum against grain, at nineteen pecks of oatmeal.

It is not a historical curiosity. Crofting townships are still soumed, and the Scottish Land Court still hears disputes about how many a shareholder may put out.