Scottish Naturalist and Mineralogist. He is noted for his advanced scholarship in natural history. His father was a soap manufacturer. He took his early education at Leith Grammar School and then became the apprentice of a local surgeon, with the intent of becoming a ship's surgeon. He attended the University of Edinburgh, Edinburgh, Scotland, from 1792 to 1793 where he studied medicine, botany, chemistry, and natural history. He was greatly influenced by John Walker, the Regius Professor of Natural History at the University of Edinburgh, which caused him to focus his career on geology and mineralogy instead of medicine in 1793. That same year, he was given the responsibility for looking after the University's Natural History Collection. Over the next few years, his geological field work took him to the various islands around Scotland as well as Ireland. In 1800 he studied for a year at the Freiberg Mining Academy in Frieberg, Saxony, under the noted geologist Abraham Gottlieb Werner. In 1804 he succeeded John Walker as the third Regius Professor of Natural History at the University of Edinburgh which he held for fifty years. He became the first British spokesman of the Wernerian geological system, or Neptunism (the discredited and obsolete scientific theory that rocks formed from the crystallization of minerals in the early Earth's oceans, which he would later renounce). Among his most noted students were the Scottish essayist and historian Thomas Carlyle as well as the British naturalist Charles Darwin. His teaching also influenced British geologist Charles Lyell, who would often attend his lectures at the University. Over the course of his professorship, he accumulated a vast collection of mineralogical and geological specimens for the University's Museum, with over 74,000 by 1852 which was second to that of the British Museum. In 1819 he teamed up with Sir David Brewster to write the "Edinburgh Philosophical Journal" and became its sole editor in 1824. He wrote many scientific papers and books, including "The Mineralogy of the Scottish Isles" (1800), his "System of Mineralogy" (1808, which ran three editions), and "Manual of Mineralogy" (1821).