James Hall, one of the United States' foremost invertebrate paleontologists, was born September 12, 1811. After the New York legislature authorized a state geological survey in 1836, Hall was assigned to collect fossils in the state's western district. He took a 5-year journey on foot and on horseback. The collection he gathered, part of which was sold to the American Museum of Natural History, became the basis for the influential 13-volume Paleontology of New York.
Hall also made lasting contributions to geology. In 1857 he described the basic geological feature that underlies mountain ranges such as the Appalachians: a crustal downfold at the edge of a continent, which fills with sediments to form a structure called a geosyncline. He also proposed a mechanism for uplifting thickened crust, called isostasy. Hall argued that crust floats on deeper material; like ships with deeper hulls, he said, thicker regions of crust ride higher. These ideas were considered so bizarre at the time that Hall did not publish them until 1883.
[Source: Charles Coulston Gillespie, Ed., Dictionary of Scientific Biography (Charles Scribner's Sons, New York, 1973).]