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GEOLOGICAL MEMOIRS. 



[zuriickweichen] of the masses. We ought here to observe, that the 

 study of the valley-formation of the Alps can only be well followed 

 out, in proportion as the general upcast of the strata approaches the 

 perpendicular. For the strata often preserve over large tracts the 

 same strike and dip, and are frequently cut through by a series of 

 valleys without suffering any change. One might expect that in the 

 great basin-like depressions the inclination of the strata would be in 

 some degree altered. Still we must consider that the uprise or tilt- 

 ing of the strata is unusually steep in the Alps ; a partial withdrawal, 

 therefore, may happen without any very striking disturbance of the 

 inclination and the succession of strata, and is far more possible than 

 under the conditions of horizontal stratification. Sometimes only are 

 we led to notice very striking disturbance of the stratification, parti- 

 cularly in the limestone Alps, and there indeed, where the greatest 

 irregularity of the valley-bottoms has been effected by the deep de- 

 pressions that even yet are occupied by the Alpine lakes. These are 

 confined chiefly to the north and south districts, and are altogether 

 wanting in the central parts, where crystalline slates abound and 

 where the elevation is most regular. 



Chapter x. (p. 222-234) contains M. Adolph Schlagintweit's ob- 

 servations on the Geological formation of the Oetz Valleij and the 

 Tauern Range. In speaking of the Alps generally, the author ob- 

 serves that crystalline slates, mica-schist, gneiss, and granite, are 

 widely distributed, and with great regularity, throughout the Alps, 

 stretching from the Maritime Alps, in important mountain-" groups," 

 to Mont Blanc, and continuing on to the eastern extremity of the 

 Alps, where they suddenly disappear beneath the tertiary formations. 

 The constituent rocks are very various. Gneiss and mica-schist pre- 

 dominate, with manifold modifications ; granite occurs but sparely, 

 and mostly in isolated masses on the southern declivities of the Alps, 

 in company with red porphyry and melaphyre. After some observa- 

 tions on the connection of geological formations with orographical 

 conditions, and an enumeration of treatises on the structure of the 

 Alps in general, and of the Oetz Valley in particular, our author 

 proceeds to give in detail the geological constitution of the Oetz-thal 

 " group" ; premising, that the great regularity of elevation over so 

 considerable an area, and the pretty equal distribution of the forma- 

 tions, are here very remarkable. In this extensive district no true gra- 

 nite is found. Gneiss, hornblende rock, and mica-slate are the most 

 prevalent rocks ; amongst these the last preponderates in extent, and 

 indeed of itself composes the highest parts. Besides these, at the 

 boundaries of the mountain-" group" there are some narrow ridges 

 of grauwacke-like rocks of red sandstone and clay-slates ; and at the 

 northern limit towards the valley of the Inn there are tracts of lime- 

 stone. The latter reach to inconsiderable heights only, and evidently 

 belong to the great limestone ranges in the north, separated by the 

 Inn Valley. These, together with small beds of calc-tuff, often com- 

 pose low terraces, behind which the crystalline rocks rise with steep 

 ascents. Within the district under notice occur some isolated masses 



