The book's own unit of comparison. Bogoras reaches for it whenever a Chukchee practice is not only Chukchee — "all the tribes of northeastern Siberia" drink tea after the meal (1-255), share one cut of glove (1-308), one diaper of moss (1-324), one bow (1-194), one dog-sledge (1-136). It is also what he measures loss against: the decrease of the native tribes (1-057), the smallpox (1-062), the liquor trade (1-263).

He never draws it. The one edge he gives is administrative and eastward — Yakutsk province ran "as far as Chaunskaya Bay" (1-079) — so the map's frame here is the editor's, and no boundary is being asserted. Its four sides are named rather than chosen: west at the western edge of the Yana basin, south at the southern tip of Kamchatka, north at Wrangel Island, east at Cape Prince of Wales, the farthest thing on the American side the book reaches for.