MINERALOGY. 409 



taining a considerable quantity of bitter earth, and for its 

 wonderful conformations, which claim the admiration of 

 every beholder, as presented in the various shapes of 

 rocks, castles, walls, pillars, and ruins of old towers, and 

 mountain fortresses. Used for many purposes, on account 

 of its water-resisting nature, hardening when immersed. 

 It serves principally, however, for making mortars or 

 molds. 



111. TRIAS FORMATION. ( Upper New Red Sand- 

 stone of the English Geologists.} 



The Trias Formation, now about to be described, is dis- 

 tinguished by a deficiency or poverty of the lime or chalk 

 principle, with the single exception of Muschelkalk (Shell 

 Limestone). The Trias system of the French and Ger- 

 man geologists, so named because it is composed of three 

 kinds of rocks, is supposed to be constituted by new 

 deposits formed around the base of the hills after the 

 elevation of Vosges, Black Forest, etc., by geological 

 convulsions, which occurred after the previous formations 

 we have partially described. The stones of this system 

 are made up of clay and sand, and mostly of a red color. 

 The most important specimens are, first, 



The Keuper Sandstone, with Marl. Resting directly 

 above this species of rock is found another strata of sand- 

 stone, which is white, coarse-grained, soft, and so easily 

 pulverized, that it is used for various domestic purposes. 

 To this succeeds marl (argillaceous carbonate lime), found 

 in successive layers between the sandstone, and is of blue 

 or red color ; next comes the genuine Keuper Sandstone, 

 which furnishes excellent building materials ; sometimes 

 it is red, at others greenish -white. Distinguished by 

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