James Hutton (1726-1797), the illustrious Scotch geologist, had something of the same aversion to speculation that did not rest on evidence; though he was eminently a philosopher in the strictest sense of the word, as his three quarto volumes on the _Principles of Knowledge_ bear witness. Hutton was well trained at Edinburgh in the High School and University. In a lecture on logic an illustrative reference to _aqua regia_ turned his mind to the study of chemistry. He engaged in experiments, and ultimately made a fortune by a process for the manufacture of sal ammoniac from coal-soot. In the mean time he studied medicine at Edinburgh, Paris, and Leyden, and continued the pursuit of chemistry. Then, having inherited land in Berwickshire, he studied husbandry in Norfolk and took interest in the surface of the land and water-courses; later he pursued these studies in Flanders. During years of highly successful farming, during which Hutton introduced new methods in Berwickshire, he was interested in meteorology, and in geology as related to soils. In 1768, financially independent, Dr. Hutton retired to reside in Edinburgh. He was very genial and sociable and was in close association with Adam Smith, the economist, and with Black, known in the history of chemistry in connection with carbonic acid, latent heat, and experiments in magnesia, quicklime, and other alkaline substances (1777). Playfair, professor of mathematics, and later of natural philosophy, was Hutton's disciple and intimate friend. In the distinguished company of the Royal Society of Edinburgh, established in 1782, the founder of dynamic geology was stimulated by these and other distinguished men like William Robertson, Lord Kames, and Watt. The first volume of the _Transactions_ contains his _Theory of Rains_, and the first statement of his famous _Theory of the Earth_. He was very broad-minded and enthusiastic and would rejoice in Watt's improvements of the steam engine or Cook's discoveries in the South Pacific. Without emphasizing his indebtedness to Horace-Bénédict de Saussure, physicist, geologist, meteorologist, botanist, who gave to Europeans an appreciation of the sublime in nature, nor dwelling further on the range of Hutton's studies in language, general physics, etc., it is already made evident that his mind was such as to afford comprehensiveness of view.