DERFFLINGER, dt•fling-er. GEORG. Baron von (1606.95). A field-marshal of Brandenburg. liorn at Neuhofen, Austria. Ile entered the Swedish serviee during the reign of Gustavus Adolphus, and advanced to the rank of colonel.
In 1642 he was sent by Torstenson to negotiate an alliance with George in Transyl vania. Several years afterwards he resigned from the Swedish service and entered that of the Elector of Brandenburg. lIe fought with dis tinction in the wars against Poland. Denmark, Sweden, and France. and was promoted to the rank of lieutenant-general. in consideration of his splendid assault on Warsaw. in 1656. field-mar shal (Ilia)), and military Governor of Pomerania (113ig). The formation and training of the cavalry of the electorate were due chiefly to his initiative, and the celebrated battle of Fehrbe (June IS, 1675) was decided by the brilliant cavalry charge \Odell he executed at the In-ad of 6500 horsemen. The conquest of Stralsund and Riigen (11;78). where at the age seventy-two he led the attack iu person, and the subsequent campaign against Sweden. were also among the
military feats of this officer. The military great ness of Prussia in later times was undoubtedly due to the influence exerted upon the army of Brandenburg by men like Derfflinger.
DERG, (Ir.. clear lake). The name of two Irish lakes. (1) The larger is an expansion of the river Shannon, between Tip perary on the southeast and Galway and Clare on the northwest (Slap: Ireland, D 2). It is 24 miles long from northeast to southwest. and 2 to 6 miles broad. Its surface is about 100 feet above the sea; its average depth, 35 feet. It has several islands. (2) A lake in the south of Donegal County. on the border of Tyrone. It is 3 miles long, miles broad. and has many islets and rocks. on its wild shores are hills rising 700 to 1200 feet. Saint's Island possesses the remains of a priory founded about the year 600, and was the scene of Saint Patrick's wisinn of purgatory. The place of penance on Station Island was for years the most celebrated spot for pilgrimage in Ireland.