William Maclure's Wernerian Appalachians

Abstract

William Maclure (1763-1840), a geologist of Scottish ancestry, was also a man of many other talents and interests including educator, philanthropist, world traveler, prolific writer, patron of science, businessman, bibliophile, and social reformer. He produced the first American printing of a geological map of the United States in 1809 and followed this with four other editions identified as 1811, 1817A, 1817B, and 1817C. All were well received and reproduced by others at least 15 times, as recently as 1989. Maclure has been called 'Father of American Geology,' a title he rightly deserves, primarily for these maps, but also for the first cross sections through the Appalachians, many other geological articles, and substantial donations of specimens, books, and funds to many learned institutions, including the Academy of Natural Sciences of Philadelphia. Maclure's delineation of Appalachian geology followed Werner's geognostic classification of strata using Primary, Transition, Secondary, and Alluvial, but with modifications and considerable doubt concerning their Neptunian origin. He added 'Rock Salt' on his 1809 map as a line on the western edge of the Appalachians and 'Old Red Sand Stone' on the 1811 map for the basins later identified as Triassic. In his later articles, Maclure noted several times that 'trap' or basalt was an igneous rock and not an aqueous precipitate. He further stated that the Secondary and Transition strata are aggregates from the disintegration of the older Primitive rocks. He came to the conclusion near the end of his life that organic remains indicate '...that nature began with the most simple, and gradually proceeded to the more complicated and perfect.'.