JANSEN, Olaus, Danish naturalist, born in Christianstadt in 1714; died in Copenhagen in 1778. He studied in Germany, and was for several years professor at the University of Tiibingen, where he acquired reputation as a naturalist. He was elected in 1761 rector of the University of Copenhagen, and in the following year a member of the Academy of sciences. Two years later he was sent by the government to travel in America and collect information on the natural productions of that country, he landed in Buenos Avres in October, 1764, and visited successively Paraguay, Uruguay, Chili, Patagonia, Araucania, Brazil, Peru, Central America, thence, crossing the Isthmus of Panama, he journeyed through New Spain, Louisiana, and Florida, reaching Boston in 1772. On his return, which was hastened by difficulties in which he was involved with the English authorities when he was about to visit Canada, he published "Den Geist in den Naturvidenskaben og naturens almindelige laere" (Copenhagen, 1773); "Journal holden y Skibet prindsess Isabella poa rejsen til Buenos Ayres" (2 vols., 1773-'4): "Forste indledning til den Almind naturlaere" (1774): " Neue Reisen durc!h Brazil und Peru" (1775)" "Neue Reisen durch Louisiana und Nueva Espana" (1776); "Ge-schichte und Beschreibung des Brodbaums" (Tuningen and Copenhagen, 1776); "Anmarkningar ons Historia Naturalis och climated af Nye England og Nye Spanien" (2 vols., Copenhagen and Stockholm, 1778); and several other works, which enjoyed a high reputation during the 18th century.