Bulletin - United States Geological Survey, Ausgaben 349-354


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Seite 222 - DIKE. A mass of granite, diabase, basalt, or other rock which has been erupted through a narrow fissure. DIMENSION STONE. A term applied to stones that are quarried of required dimensions. DIP. The inclination from the horizon, given in terms of degrees, of a sheet, joint, heading, dike, or other structural plane in a rock. DRIFT. Sand and bowlders deposited by the continental glacier.
Seite 30 - The individual lesions appear as tense, clear, shiny vesicles, obtuse, round, or ovoid in form, and varying in size from that of a pin head to that of a pea.
Seite 44 - The impact of the hammer breaks up the granules on the immediate surface so that the light falling upon it is reflected, instead of absorbed, and the resultant effect upon the eye is that of whiteness. The darker color of a polished surface is due merely to the fact that through careful grinding all these irregularities and reflecting surfaces are removed, the light penetrating the stone is absorbed, and the effect upon the eye is that of a more or less complete absence of light or darkness. Obviously...
Seite 224 - A term applied to rock consisting of originally horizontal beds or strata. STRIKE . The direction at right angles to the inclination of a plane of bedding, a sheet, or joint, etc. STRIPPING. The material (sand, clay, soil, etc.) overlying a rock of economic value, which must be removed before quarrying.
Seite 28 - ... wholly to exfoliation parallel to preexisting lines of weakness. The mass appears to be made up of imbricated sheets of granite which he regards as the result of torsional strains. The bosslike form is incidental and consequent. Intermittent expansion and contraction from changes of temperature have so affected the sheets that bound the mass at the sides that they have found relief in expansion in an upward direction. These ruptured sheets are rarely more than 10 inches thick, but are 10 or 20...
Seite 223 - ... and of potash feldspar are nearly the same or in which the former exceeds the latter. In ordinary granites the amount of soda-lime feldspar is relatively small. RANDOM STONE. A term applied by quarrymen to quarried blocks of any dimensions.
Seite 31 - The observations made in Europe and in this country, taken in connection with the various inferences geologists have drawn from them, indicate that sheet or " onion " structure in granite rocks is due to the following possible causes: 1. To expansion caused by solar heat after the exposure of the granite by erosion. 2. To contraction in the cooling of the granite while it was still under its load of sedimentary beds, the sheets being therefore approximately parallel to the original contact surface...
Seite 35 - In some quarries the granite near the surface acquires a marked foliation, which appears to be parallel to the sheet structure, and in places to the rift. This foliation is known by quarrymen as " shakes." It occurs both at the top and at the bottom of the sheet, through a maximum thickness of 6 inches. It is coextensive with the discoloration known as " sap " and occurs at many places near vertical joints. Under the microscope this structure proves to consist of minute, nearly parallel fissures,...
Seite 26 - The curves are arranged strictly with reference to the surface of the masses of rock, showing clearly that they must have been produced by the contraction of the material while cooling or solidifying, and also giving very strongly the impression that, in many places, we see something of the original shape of the surface, as it was when the granitic mass assumed its present position.
Seite 90 - WEB'STER. A town, including several vil-lages, in Worcester County, Mass., 16 miles south by west of W'orcester, on the French River, and on the New York, New Haven and Hartford and the Boston and Albany rail-roads (Map: Massachusetts, D 3).

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