William B. Rogers, the well-known memoir, On the Physical Structure of the Appalachian Chain, unfolding certain dynamical laws which have regulated the elevation of mountain chains. About the same time (1842) he published an elaborate paper on the origin of the Appalachian coal strata, bituminous and anthracite, containing much original observation and important speculative views, his brother pursuing a parallel system of investigation in Virginia, where the formations are identical with those of Pennsylvania. The result of the labor of these two brothers, carried on for ten years together, was the grand discovery of the structural unity of central North America, between the Appalachian chain and the Rocky Mountains, the Great Lakes, and the Delta inclusive, a fact of such importance that it must serve in future as a guide to all general researches, since it is not reasonable to suppose that so large a portion of the earth's surface should have been formed in any other than the normal mode. . . . Prof. Rogers was one of the founders and an early president of the American Association of Geologists, which after an active and most useful career expanded into the American Association for the Advancement of Science.
"Although chiefly devoted to geological research, he paid much attention to those sciences of which geology is the extended application—natural history, climatology, and physical geography."
His work was appreciated abroad as well as at home. He received the degree of LL. D. from Trinity College, Dublin; was elected a Fellow of the Royal Society (London), and of the Royal Society of Edinburgh, and of many other important societies. He was also for two years the President of the Philosophical Society of Glasgow. He became one of the conductors of the Edinburgh New Philosophical Journal, and was associated with Sir William and A. K. Johnston in the publication of maps of physical geography and geology, particularly of a geological map of the United States and a chart of the arctic regions in their Physical Atlas.
The anniversary address of the President of the Geological Society (London), in a notice of Prof. Rogers, contains the following estimate of his work as a geologist:
"While employed upon his great survey he had contributed to the Proceedings of this society a paper entitled Some Facts in the Geology of the Central and West Portions of North America. In this address he dwelt especially on those great features which he had elaborated in his survey, the disturbance of the Palæozoic rocks of the Appalachian chain, ‘a stupendous undulation or wavelike pulsation, the strata being elevated into permanent anticlinal and synclinal flexures, remarkable for their wave-
