Geological considerations are involved in a great variety of engineering undertakings related to river and harbor improvements, dam sites, etc., mentioned in Chapter XX.
FOOTNOTES:
[12] Mead, Daniel W., Hydrology: McGraw-Hill Book Co., New York, 1919, pp. 447-448, 456.
CHAPTER VI
THE COMMON ROCKS AND SOILS AS MINERAL RESOURCES
ECONOMIC FEATURES OF THE COMMON ROCKS
Under the general heading of common rocks are included the ordinary igneous, sedimentary, and "metamorphic" rocks, and the unconsolidated clays, sands, and gravels characteristic of surface conditions, which are mined and quarried for commercial use. Soils are closely related to this group; but since they present special problems of their own, they are discussed under a separate heading at the end of the chapter. Names of the common rocks will be used with the general commercial significance given them by the United States Geological Survey in its mineral resource reports.