Arnold Henry Guyot, an American geographer, born near Neufchatel, Switzerland, Sept. 28, 1807. He studied at Neufchatel, Stuttgart, and Carlsruhe, where he formed an intimate friendship with Agassiz, and began with him the study of natural science. He afterward studied theology for three years at Neufchatel and Berlin; but he was gradually led to devote himself to physics, meteorology, chemistry, mineralogy, zoology, and botany. In 1835 he went to Paris, where he resided five years, passing the winters in study and the summers in scientific excursions through France, Belgium, Holland, and Italy. In a tour of Switzerland in 1838, he first discovered the laminated structure of the ice in glaciers, the motion of the central portion being more rapid than that of the borders, as in streams of water. He showed that the motion of the glacier is due to the displacement of its molecules. These discoveries were fully confirmed and illustrated by the investigations of Agassiz, Forbes, and others, several years afterward. He next investigated the distribution of erratic bowlders, in order to solve the question of the mode of their transportation.

De Saussure, Von Buch, Escher, and Charpentier had made numerous observations on this subject, but the extent and true limits of these great outpourings of rocks from the bosom of the Alps were not accurately known. During seven successive summers Guyot traced them on both sides of the central Alps, in Switzerland and Italy, over a surface 300 m. long and 200 m. wide, and delineated eleven different regions of rocks. Their vertical limits and the laws of their descent were determined by means of more than 3,000 barometrical observations; and the characteristic species of rock of each basin were tracked step by step to their source. The full details of these investigations were announced to form the second volume of the Systeme glaciaire by Agassiz, Guyot, and Desor, the first volume of which was printed in Paris in 1848; but political disturbances and the removal of Guyot to the United States prevented its publication. A topographical map of the subaqueous basin of the lake of Neufchatel, believed to be the first of the kind ever published, was his next work.

Guyot was professor of history and physical geography in the academy of Neufchatel from 1839 to 1848. He then removed to the United States, and resided for several years at Cambridge, Mass., occasionally delivering lectures on his favorite subjects. He delivered in Boston in the winter of 1848-'9, in the French language, a course of lectures on the relations between physical geography and history, afterward translated and collected into a volume under the title of "Earth and Man." He was now employed by the Massachusetts board of education to deliver lectures in the normal schools of the state and before the teachers' institutes, and by the Smithsonian institution to organize a system of meteorological observations, for which he prepared an extensive series of practical tables. He was the first to determine the true height of Mt. Washington, in 1851; of the Black mountains of North Carolina, in 1856; and of the Green mountains of Vermont, in 1857. By these investigations he ascertained that there are more than 20 peaks in the Black and Smoky ranges higher than Mt. Washington. In 1855 he was appointed professor of physical geography in the college of New Jersey at Princeton, which post he still retains.

In 1873 the Vienna international exhibition gave him a medal of progress for his geographical works. He read a paper on "Cosmogony and the Bible" before the meeting of the evangelical alliance in New York in 1873, embodying the substance of a course of lectures previously delivered in the Union theological seminary in New York. He has also published "Directions for Meteorological Tables" (Washington, 1850); "Geographical Series, Primary Geography" (New York, I866; almost immediately republished under the title "Introduction to Geography"); "Intermediate Geography" (1870); and "Physical Geography," with a set of wall maps (1873). He has delivered lectures on "The Unity of the System of Life, the true Foundation of the Classification of Plants and Animals," in Brooklyn, N. Y., and before the Smithsonian institution in Washington, and on "Man Primeval," in the Union theological seminary in New York.