Articles

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Rocks of rhyolitic type in eastern Idaho and adjacent parts of Wyoming were observed by the Teton Division of the Hayden Surveys under Orestes St. John (Report of the geological field work of the Teton Division, U.S. Geol. and Geog. Surv. Terr., 11th Ann. Rep., pp. 498–504, 1879), who described them as trachytes. He noted their relations to different types of underlying sedimentary rocks and their

The history of vulcanism in Alaska is a topic of great universal interest, but one which has had no adequate treatment. For some years the writer has been accumulating comparative data on this subject, and it is hoped that this information may some time be sufficiently amplified and coordinated to justify a general description of the sequential igneous history of Alaska. The scope of such an under

The study of the Highwood Mountains was undertaken by a group of men from Harvard University under a grant from the Shaler Memorial Fund of the Department of Geology. The work was under the general direction of Larsen, who, with the assistance of Norman A. Haskell, mapped most of the volcanic rocks. Hurlbut and Griggs worked mostly on the laccoliths, Burgess on the stocks, and Buie on the dikes. T

The Blue Ridge and Piedmont geomorphic provinces, topographically distinct but geologically a unit, extend southwestward across eastern Pennsylvania and central Maryland, in a belt with an average width in these States of some 50 miles. In these provinces are exposed the crystalline formations of the Atlantic belt. Gneisses (with sporadic interbedded graphitic schist and marble), quartz-schist, cr

The Island of Oahu is third in size in the Hawaiian group and lies in the mid-Pacific about 2,100 miles southwest of San Francisco. Honolulu, the capital and principal port of this group, is on Oahu. Two dissected volcanic domes, the Waianae Range (4,035 feet high) and the Koolau Range (3,105 feet high) make up the island. They are surrounded by a nearly continuous coastal plain, in places reachin

Many of the water‐bearing formations in the United States have hydraulic gradients of much less than 20 feet to the mile, and some may have gradients of less than one foot to the mile, whereas most laboratory‐tests of permeability are made with much higher gradients. An investigation was therefore undertaken by the writer, under the direction of 0. E. Meinzer, in the Hydrologic Laboratory of the U

The ground‐water of the Florida Peninsula constitutes one of its most valuable natural resources and is of importance as a source of water‐supplies throughout the area. The problems relating to the development of ground‐water supplies are both quantitative and qualitative. They include such problems as the decline in yield of wells in areas of large withdrawals of water and salt‐water contaminatio

Volcanic rocks occur from Pennsylvania to Alabama in the Piedmont Plateau, Blue Ridge Area, and the Great Valley. They include volcanics of pre‐Cambrian, Cambrian, and Middle Ordovician age. The most abundant types are basalt, andesite, rhyollte flows, tuffs, ash‐beds, and bentonite. The paper will discuss the types of volcanics In the different areas, their metamorphism, the relations of volcanic

Whenever measurements show that the discharge of a stream becomes smaller as it passes downstream to a considerably larger drainage-area and no diversions of water are known to exist between the places of measurement, curiosity is always aroused as to the cause, and a question may be raised as to the accuracy of the measurements purporting to show the decrease.Small streams sometimes disappear in

The annual report this year consists almost wholly of a brief summary of investigations in progress in different parts of the country. It is by no means complete, and the Chairman of the Committee will be glad to receive information in regard to investigations that have not been mentioned.The outstanding feature of the past year has been the focusing of public attention on problems of underground