Bothnia, a gulf between Sweden and Russia,-constituting the northern arm of the Baltic sea, extending from lat. 60° to 65° 50' N., 400 m. in length, with an average breadth of 120 m. At its mouth, about midway between the two shores, is the Aland archipelago, belonging to Russia, and the main entrance is the Alands Haf, a strait about 24 m. wide, on the Swedish side of the islands. About midway of its extent it is gathered into a channel much narrower than its main body, called the straits of Quarken. The channel is also further intercepted at this place by several small islands, the principal of which is Holnio. The entire coast line of the gulf is very irregular. There is a strong current, or gulf stream, setting constantly from the head of the gulf southward, through Quarken, to Aland, where it divides into two, one passing E. and the other W., to reunite again, and also with a third current from the gulf of Finland, near the island of Kokar, whence it sets southward through the Baltic. There are good harbors, the principal of which on the Russian side are Abo-Bjor-neborg, Uleaborg, and Tornea; and on the Swedish, Gefle, Hernosand, Pitea, Umea, and Lulea. The S. shore of the gulf is annually visited by shipping for the export of timber and naval stores.
It is usually completely frozen in the winter, so that armies have marched across it. The strong current and the abundant supply of fresh water, from a shed of an average breadth of 150 m. throughout its entire extent of coast line, give the waters of this gulf great freshness. The gulf of Bothnia presents an undoubted instance of slow upheaval of its E. and W. coasts, now taking place without volcanic action, at the approximate rate of two or three feet in a century. The coasts S. of Quarken are generally precipitous, and N". of the straits low and sandy. The numerous rivers which flow from Sweden and Finland into the gulf abound with fish, especially a kind of small herring called stromming, which constitutes a prominent article of food among the lower classes. A large part of the population on the W. coast are occupied in catching them. Most of these herrings are dried in the usual manner, but a considerable portion undergo fermentation in a closed cask, after having been previously a little salted and exposed to the air for a short time.
The fish thus acquires a sour taste, and is called sur-stromming.