born June 3, 1726, Edinburgh, Scot.
died March 26, 1797, Edinburgh
Scottish geologist, chemist, and naturalist.
After short careers in law and medicine, he followed his interest in chemistry and developed an inexpensive manufacturing process for sal ammoniac. He settled in Edinburgh (1768) to pursue a life of science. In two papers presented in Edinburgh in 1785 (published 1788), he elaborated his theory of uniformitarianism . Its ability to explain the Earth's geologic processes without reference to the Bible and its emphasis on an immensely long, cyclical process of erosion, deposition, sedimentation, and volcanic upthrust were revolutionary.