KELLER, Christian Arnold, Swiss explorer, born in Friburg in 1711; died in Basle, 11 October, 1790. He received his early education in Switzerland, but finished it in Paris, and was employed in 1734 in the physical cabinet of the Paris Academie des sciences. In 1735 he accompanied Charles Marie de la Condamine to South America. In 1740 he followed La Condamine again during his exploration of the Amazon, but parting with him in Columbia, he travelled extensively in South America, and returning in the spring of 1749, after an absence of fourteen years. In 1751 he was given the chair of physics and chemistry in the University of Basle, which he occupied till his death. Keller's works include "Discours du voyage des astronomes La Condamine, Bouguer et Godin, pour mesurer un arc du meridien g l'equateur, suivi d'un traitd et description des plantes et des animaux qui habitent les Cordillieres du Perou" (2 vols., Geneva, 1771); "La pression atmospherique dans les Cordillieres des Andes et du Perou" (Paris, 1756); " Observations astronomiques faites dans les Cordillieres du Perou" (1758); "Reise auf dem Amazonenflusse" (1773); "Neue Amerikanische Beitrage" (1776); " Reisen im Innern yon Siid-Amerika" (Basle, 1781); " Land und Leute yon Peru" (2 vols., 1784); and "Grand atlas de l'Amerique du Sud" (6 vols., 1788).