ON May 1 a very notable figure passed away from the field of geological discovery and research. Dr. Grove Karl Gilbert was born in Rochester, N.Y., in 1843, and had thus almost completed his seventy-fifth year. In his “Report on the Geology of the Henry Mountains,” issued by the U.S. Geographical arid Geological Survey of the Rocky Mountain region in 1877, he developed the theory of the expansion of intrusive igneous sheets into the great cauldron-like masses that he conveniently styled “laccolites” (stone cisterns), and the rapid recognition of laccolites throughout the world bore witness to the cogency of his exposition. From 1879 onwards he was attached to the staff of the U. S. Geological Survey, and it is not too much to say that his reports helped considerably to direct general scientific attention to the earlier publications of that body. His “Contributions to the History of Lake Bonneville” in 1882, and his monograph on “Lake Bonneville” in 1890, became classics for the treatment of vanished lakes in other areas, and also raised important questions as to crustal yielding under load.