An inland sea in the N. of Europe, 900 m. long and from 100 to 200 m. broad, about the size of England and Wales; comparatively shallow; has no tides; waters fresher than those of the ocean, owing to the number of rivers that flow into it and the slight evaporation that goes on at the latitude; the navigation of it is practically closed from the middle of December to April, owing to the inlets being blocked with ice.