Selections from the correspondence (_Briefwechsel_) of Frederick William IV. and Bunsen were edited by Ranke (Leipzig, 1873); his proclamations, speeches, &c., from the 6th of March 1848 to the 31st of May 1851 have been published (Berlin, 1851); also his correspondence with Bettina von Arnim, _Bettina von Arnim und Friedrich Wilhelm IV., ungedruckte Briefe und Aktenstuecke_, ed. L. Geiger (Frankfort-on-Main, 1902). See L. von Ranke, _Friedrich Wilhelm IV., Koenig von Preussen_ (works 51, 52 also in _Allgem. deutsche Biog._ vol. vii.), especially for the king's education and the inner history of the debates leading up to the united diet of 1847; H. von Petersdorff, _Koenig Friedrich Wilhelm IV._ (Stuttgart, 1900); F. Rachfahl, _Deutschland, Koenig Friedrich Wilhelm IV. und die Berliner Maerzrevolution_ (Halle, 1901); H. von Poschinger (ed.), _Unter Friedrich Wilhelm IV. Denkwuerdigkeiten des Ministers Otto Frhr. von Manteuffel_, 1848-1858 (3 vols., Berlin, 1900-1901); and _Preussens auswaertige Politik_, 1850-1858 (3 vols., ib., 1902), documents selected from those left by Manteuffel; E. Friedberg, _Die Grundlagen der preussischen Kirchenpolitik unter Friedrich Wilhelm IV._ (Leipzig, 1882). FREDERICK WILLIAM (1620-1688), elector of Brandenburg, usually called the "Great Elector," was born in Berlin on the 16th of February 1620. His father was the elector George William, and his mother was Elizabeth Charlotte, daughter of Frederick IV., elector palatine of the Rhine. Owing to the disorders which were prevalent in Brandenburg he passed part of his youth in the Netherlands, studying at the university of Leiden and learning something of war and statecraft under Frederick Henry, prince of Orange. During his boyhood a marriage had been suggested between him and Christina, afterwards queen of Sweden; but although the idea was revived during the peace negotiations between Sweden and Brandenburg, it came to nothing, and in 1646 he married Louise Henriette (d. 1667), daughter of Frederick Henry of Orange, a lady whose counsel was very helpful to him and who seconded his efforts for the welfare of his country.