The conditions in the United States have been favorable to the development of geology. The varied forms of the land have offered abundant opportunities for research, whereas the practical value of the work has led to the establishment of surveys, the magnitude of whose contribution to geology is only known to special students. The Geological Society of America has about two hundred and fifty members, nearly all of whom are actively engaged in geological research, perhaps a larger number than in any other science. The U. S. Geological Survey is the center of this movement, and its great efficiency is in large measure due to Mr. G. K. Gilbert, now president of the American Association for the Advancement of Science. He was born in Rochester, N. Y., in 1843, and after graduating from the university in that city, acted for five years as assistant in the Ward Museum, where a number of eminent naturalists have been trained. He then became geologist in the Ohio Survey under Newberry, was engaged in the Wheeler and Powell Surveys, and has been geologist in the U. S. Geological Survey since its establishment in 1879. In the arid west, where the face of the earth is bare, Mr. Gilbert made the observations and discoveries in dynamical and physical geology which have done so much toward the making of the science of physiography. His monographs on the Henry Mountains and on Lake Bonneville, the name he gave to the ancient lake that once filled the Utah basin, are models, both in regard to their original discoveries and the methods of presentation. He has extended his studies to the basins of the Laurentian Lakes and to other regions, always with important results. Mr. Gilbert has been president of the American Society of Naturalists, the Geological Society of America and the Philosophical Society of Washington, and has received the Wollaston Medal of the Geological Society of London. His presidential address before the American Association will be given at the American Museum of Natural History, New York City, on the evening of June 26, his subject being ‘Geological Rhythm.’ * * * * *