Annual Report on the Geological Survey of Pennsylvania

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Page 88 - Trap family, usually fissile. It is sonorous when struck with a hammer, whence its name. Coal Formation. — This term is generally understood to mean the same as the Coal Measures. There are, however,
Page 87 - Axis. 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 anticlinal axis. In a row of houses with steep roofs facing the south, the slates represent inclined strata dipping north and south, and the ridge is an east and west anticlinal axis.
Page 90 - 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 snip, pyr, fire, because, under particular circumstances, the stone produces spontaneous heat and even inflammation.
Page 34 - It requires to be ground in a drug-mill, and levigated in troughs, by passing over it a stream of water. Thus prepared, it constitutes, when mixed with oil, a very excellent pigment for the exterior of houses, fences, and other structures exposed to the weather.
Page 27 - Schuylkill, there are numer ons and extensive quarries, furnishing a large supply of the rock, a portion of which is transported to Philadelphia and other places, by the several railroads and the Schuylkill navigation ; but a large amount is converted into lime on the spot, designed for the same markets. "A large quarry of the limestone is wrought on the west side of the Schuylkill, two or three miles below Valley Forge, where the rock is tolerably thick- bedded, and of a light color.
Page 28 - Philadelphia with the beautiful article employed in so many of its private and public edifices. It is on the farm of Mr. John R. Thomas. The beds on this quarry are slightly contorted. The portion worked for the marble separates into two bands. The rock occurs in massive beds, chiefly white, with sometimes a bluish tinge, and is quarried with great facility. It has been much used in the construction of the Girard College and other public buildings which adorn Philadelphia and the neighboring towns.
Page 88 - Conglomerate or Puddingstone. — Rounded water-worn fragments of rock or pebbles, cemented together by another mineral substance, which may be of a siliceous, calcareous, or argillaceous nature.
Page 90 - OXIDE. The combination of a metal with oxygen; rust is oxide of iron. OXYGEN. One of the constituent parts of the air of the atmosphere ; that part which supports life. For a further explanation of the word, consult elementary works on chemistry.
Page 87 - CARBONATE of LIME. Lime combines with great avidity with carbonic acid, a gaseous acid only obtained fluid when united with water, — and all combinations of it with other substances are called Carbonates. All limestones are carbonates of lime, and quick lime is obtained by driving off the carbonic acid by heat.
Page 93 - ... regularity, showing that the rock was deposited from a rather gentle current and probably in a shallow sea. Impressions of arundinaceous plants are not uncommon. Thickness, by estimation, thirty feet. No. XVI. LIMESTONE. Resting on the above, and immediately underlying the Pittsburg coal seam, is a bed of limestone of characteristic appearance and remarkable for the regularity with which it accompanies the coal. It consists of blue and black limestone in layers from six to ten in number, separated...

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