in volcanic districts, and in the vicinity of the salt springs of the Uni- 

 ted States. 



ITew Red Sandstone. "A series of sandy and argillaceous, and of- 

 ten calcareous strata, the prevailing color of which is brick reil, but con- 

 taining portions which are grounish gray. Those occur often in ppots 

 and stripes, so that the series has sometimes been called the variegated 

 sandstone. The European, so called, lies in a geological position im- 

 mediately above the coal measures." 



Nodule. A rounded, irregular shaped lump or mass. 



Old Red Sandstone. "A stratified rock belongin;' to the carbonif- 

 erous group of Europe." 



Oolite, oolitic. "A limestone, so named, because it is composed of 

 rounded particles, like the roe or eggs of fish. The name is also ap- 

 plied to a large group of strata characterized by peculiar fossils." 



Organic Remains. See Fossils. 



Orthoceratite. The remains of an extinct genus of molluscous aiii- 

 mals, called Cephalopoda. The orthoceratites are loug, straight, coni- 

 cal chambered shells. 



Out-crop. See Crop out. 



Out-liers. Hills or ranges of rock strata, occurring at some distance 

 from the general mass of the formations to which they belong. Many 

 of these have been caused by denudation, having ren)oved parts of the 

 strata which once connected the out liers with the main mass of thj for- 

 mation. 



Oxide. A combination of oxygen with another body. The term is 

 usually limited to such combinations as do not present active acid or al- 

 kaline properties. 



Puloeontology. A science which treats of fossil remains. 



Pisolite. A calcareous mineral, composed of rounded concretions, 

 like peas. 



Pliocene. The upper, or more recent tertiary strata. This group of 

 strata is divided into the older and newer pliocene rocks. 



Petroleum. A liquid minerul pitch. It is common in the region of 

 salt springs in the United Slates. 



Porphyry. A term afiplied to every species of unstratified rock, in 

 which detached crystals of feldspar are ditluseJ through a compact base 

 of other mineral composition. 

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