Bulletin - United States Geological Survey, Ausgabe 315

Cover
 

Was andere dazu sagen - Rezension schreiben

Es wurden keine Rezensionen gefunden.

Andere Ausgaben - Alle anzeigen

Häufige Begriffe und Wortgruppen

Beliebte Passagen

Seite 14 - minerals and water solutions, with special reference to geologic phenomena, by EC Sullivan.
Seite 257 - H. The limestone quarries of eastern New York, western Vermont, Massachusetts, and Connecticut.
Seite 138 - Its soft ore, now nearly all mined out either by surface trenches or drifts, is the best in the district. Its hard ore is also of high grade and hitherto has been for the most part held in reserve, since ore could be produced from the thicker Big seam at a lower cost per unit of iron. The structure and composition of the Big and Irondale...
Seite 129 - No. 2I«, 1!X», pp. 321-334. strong contrast with the irregular, roughly dissected topography of the coal fields. The valley topography is characterized by long, narrow, canoeshaped troughs, in general parallel to each other and separated by well-defined ridges. The trend of the valleys is approximately N. 30° E. Their form is directly dependent on the geologic structure and lithology of the underlying rocks. They are developed mainly on the softest and most soluble rocks, along the axes of anticlines,...
Seite 71 - The examination of this region was made primarily for the purpose of determining the locality of the various coal and oil beds that occur in Uinta County and to trace northward the coal formations mapped by AC Veatch and the writer in southern Uinta County during the summer of 1905. In carrying out this plan the surveys were carefully tied to the land corners, and geologic and sketch topographic maps were prepared on a scale of 2 inches to the mile, with a contour interval of 100 feet. These separate...
Seite 404 - Orthoclase and microcline are the most common varieties of feldspar found in pegmatite. In many places, however, a variety of plagioclase, either albite or oligoclase, makes up part or all of the feldspar component.
Seite 403 - Sterrett1 that we may quote his description almost without modification. After stating that the pegmatites of North Carolina occur mainly in the Roan gneiss, which is a series of hornblendic gneisses and schists, and in the Carolina gneiss which is nonhornblendic, he says : . Pegmatites occur in irregular masses, streaks, lenses, augen, or balls, some of them having no visible connection with other pegmatite bodies. They range from a fraction of an inch up to many yards in thickness. . . . Horses,...
Seite 138 - ... to the southwest. The middle of the Big seam is the workable part in the northeast end of the district, but the upper bench is of most importance throughout the rest of the area. In the southwest portion of the district the lower bench, which farther northeast is composed of ore that will in later years be...

Bibliografische Informationen