That this appointment, which in effect embraced natural science at large, should come to be the recognized beginning of the teaching of geology in America reflects more than a presonal bent of Silliman's mind. It was in an age concerned intellectually with conflicting visions of man's place in nature and practically with the exploration and exploitation of the natural resources of a new continent. A boundless optimism and faith in the universality of science and reason sustained the offspring of the Enlightenment. Rocks, minerals, and living organisms manifest chemistry in nature, and so it was perfectly natural that the Professor of Chemistry should concern himself with geology. The new science had not yet fully confronted the subtle kinetics and baffling complexity of natural systems, which would force geology during the nineteenth century more and more into the pigeonholes of descriptive disciplines. At any rate Silliman began by sending a "half-bushel of unlabeled stones" to Philadelphia to be identified, and in the year he spent abroad it was his excursions with the geologists then beginning to emerge in Britain, particularly at Edinburgh, that most engaged him. There is a prophetic note in Silliman's concern with both geology and chemistry, for the facilities of the Kline Geology Laboratory now clearly proclaim the extent to which the experimental investigation of natural systems has become a central theme of modern geology.

A similar faith in the universality of science is felt in Silliman's founding of America's oldest surviving journal of natural science in 1818. The title page ran: "The American Journal of Science more especially of Mineralogy, Geology, and the Other Branches of Natural History, including also Agriculture and the Ornamental as well as Useful Arts." It was widely known as "Silliman's Journal," and with the passingyears became essentially devoted to geology. Benjamin Silliman, Jr., who became Professor of Chemistry at Yale, succeeded his father as editor, but even the younger Silliman was to be best remembered for his report on the properties of crude oil from a seep in Pennsylvania, a report that led to the drilling of the first oil well. Otherwise members of the Department of Geology at Yale have always borne the principal editorial responsibility. Professor John Rodgers is the present editor of the American Journal of Science. Its editorial office is now part of the Kline Geology Laboratory, and its status in geology is international.

Ideas that exercised an enduring influence on geology came in profusion with James Dwight Dana, Silliman's most distinguished student and ultimate successor, holder of the first Silliman Professorship of Natural History at Yale, and, as it happened, Silliman's son-in-law. In 1833, at the age of twenty, Dana took leave of Yale College somewhat in advance of graduation to serve as instructor in mathematics for midshipmen of the United States Navy on a cruise to the Mediterranean. His first scientific paper, published in 1835, records his observations of Vesuvius. He returned to Yale as Silliman's assistant, and at the age of twenty-four produced the first edition of System of Mineralogy, which was to go through six editions during his lifetime to become one of the first internationally recognized scientific treatises by an American.

A voyage of exploration to the Pacific Ocean and the southern seas in the years 1838-1842 on the Peacock in the commmand of Captain Wilkes gave Dana an intense, prolonged, and unrelenting confrontation with the scale and scope of the forces of nature. Such an experience is common to countless seamen and ordinary adventurers without coming to any great result. In Dana it was mediated by a mind of extraordinary vigor and became basic input for a lifetime of imaginative attack on the most profound and searching questions of geology.

The parallels in external circumstances are striking; one wonders at the parallels in inner experience with another voyage in the same seas and almost in the same span of years by another young man, Charles Darwin on the Beagle. Both Dana and Darwin returned to publish geological observations with important and original ideas about such problems as volcanoes, the crystallization of lava, the origin of coral atolls, cycles of erosion, and development of continents and oceans basins. Both undertook, almost as a matter of personal discipline, to write monumental treatises in systematic biology, Dana on crustaceans, Darwin on the Cirripedia (barnacles and related animals). Darwin, forced by failing health into a life of semi-seculsion, abandoned his first love (so he called it), geology, for the painstaking biological research which produced The Origin of Species and an intellectual revolution. Though overwork took a heavy roll of Dana's health, he became the leading figure of the century in Amiercan geology through his books, through his teaching, and through the men he taught. When he succeeded Silliman in 1850 he was Yale's only Professor of Natural History. When he became inactive a few years before his death in 1895 Yale had a faculty in geology which was the peer of any in its time. There were seven men, G. V. Brush, S. L. Penfield, L. V. Pirsson, O. L. Marsh, H. S. Williams, C. E. Beecher, and his own son and collaborator, Edward Salisbury Dana.