Sleaford, a town of Lincolnshire, on the right bank of the Slea, a branch of the Witham, 17 miles SSE. of Lincoln. It has a fine church (1271), a grammar-school (1624), and a monumental cross (1850). King John was struck with his last illness (1216) in the old castle, now almost wholly disappeared. Pop. 5750.

Sleswick(Danish Slesvig; Ger. Schleswig) forms, united with the former duchies of Holstein and Lauenburg, a province of Prussia, just south of Denmark. Area, 7273 sq. m.; pop. (1900) 1,387,968, nearly all Low Germans, except in the north of Sleswick, where there are 140,000 Danes. Sleswick belongs to the alluvial peninsula of Jutland, its eastern half being an undulating plain and its western a series of low-lying but very fertile marsh-lands, protected from the ocean by sea-banks. The eastern coast (230 miles) is deeply indented by several long narrow arms of the sea, some of which make excellent harbours, and alongside it lie the islands of Fehmern and Alsen. The low western coast is protected by a string of low islands and sandbanks from the waves of the North Sea. The Elbe (on the S. border) and the Eider are the great rivers; and the province is crossed by the Baltic Ship Canal (in Holstein, 61 miles long), the Eider Canal, Stecknitz Canal, etc. Nearly 87 per cent. of the area is cultivated; fishing is also carried on. Flensburg is the chief seaport.

At the dawn of history Sleswick was inhabited by the Cimbri, who were succeeded by the Angles, Jutes, and Frisians; but the greater part of the Angles crossed over into England, and their place was taken by the Danes. Successively Danish and German, or sometimes independent, for more than a thousand years, Sles-wick-Holstein was the scene of an unsuccessful rebellion against Denmark in 1848-50, but in 1864 was wrested therefrom by Prussia and Austria. The dissensions between these powers led to the Austro-Prussian war of 1866, and to the ultimate incorporation of the duchies with Prussia.