KOEPPEN, Adolphus Louis, educator, born in Copenhagen, Denmark, 14 February, 1804; died in Athens. Greece, 14 April, 1873. He was destined for the army, but studied law, and in 1825 entered the royal board of commerce. In 1834, during a visit to Greece, he was invited by King Otho to fill the professorship of history, archaeology, and modern languages at the royal military college of the Euripides, which was then situated in the island of Aegina. He was obliged to retire in 1843, in consequence of a popular demonstration against the German system of government, and returned to Denmark, but in 1846 came to the United States at the invitation of the Historical society of Philadelphia, before which he delivered a course of lectures on "Ancient and Modern Athens and Attica." These were repeated within the next few years in an enlarged form before the Lowell institute in Boston, the Smithsonian institution in Washington, the University of Virginia, Brown university, and other similar bodies. In 1850-'1 he gave lectures on the political, social, and literary history of the middle ages. About the same time he accepted the professorship of history, aesthetics, and modern languages in Franklin and Marshall college, Lancaster, Pennsylvania He published "The World in the Middle Ages," accompanied by an "Historico-Geographical Atlas of the Middle Ages" (2 vols., New York, 1854).