A Reprint of Annual Reports and Other Papers on the Geology of the Virginias

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D. Appleton, 1884 - Geology - 832 pages
 

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Page 743 - A series of sandy, argillaceous, and often calcareous strata, the predominant colour of which is brick red, but containing portions which are of a greenish grey. These occur often in spots and stripes, 'so that the series has sometimes been called the variegated sandstone. The European formation so called lies in a geological position immediately above the coal measures.
Page 633 - ... horizontal direction, there being. . .little or no cohesion between one stratum and another. The part of the earth that is first raised, being bent from its natural form, will endeavour to restore itself by its elasticity, and the parts next to it, beginning to have their weight supported by the...
Page 633 - Suppose a large cloth, or carpet (spread upon a floor) to be raised at one edge, and then suddenly brought down again to the floor, the air under it being by this means propelled, will pass along, till it escapes at the opposite side, raising the cloth in a wave all the way as it goes.
Page 744 - PYRITES (Iron). A compound of sulphur and iron, found usually in yellow shining crystals like brass, and in almost every rock stratified and unstratified. The shining metallic bodies, so often seen in common roofing slate, are a familiar example of the mineral. The word is Greek, and comes from irvp, pyr, fire, because, under particular circumstances, the stone produces spontaneous heat and even inflammation.
Page 746 - ROCKS. Volcanic rocks composed of felspar, augite, and hornblende. The various proportions and state of aggregation of these simple minerals, and differences in external forms, give rise to varieties, which have received distinct appellations, such as basalt, amygdaloid, dolorite, greenstone, and others. The term is derived from trappa, a Swedish word for stair, because the rocks of this class often occur in large tabular masses, rising one above another, like the steps of a staircase. For further...
Page 737 - If a range of hills, or a valley, be composed of strata, which on the two sides dip in opposite directions, the imaginary line that lies between them, towards which the strata on each side rise, is called the anti clinal axis.
Page 168 - ... with innumerable markings at right angles to the stratification, penetrating in straight lines to great depths in the rock, and from their frequency and parallelism determining its cleavage in nearly vertical planes. These markings are of a flattened, cylindrical form, from...

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