﻿MM. SCHLAGINTWEIT ON THE ALPS. 



25 



have been deposited in standing waters. The inequalities of the 

 valley-bottoms may, indeed, in many cases be sufficient cause for 

 this ; but sometimes (for example, near Lengenfeld) the form of the 

 ravine immediately following, and the depth of the erosion of the 

 river-channel, show that here a stopping of the water-course had 

 taken place. At all events, this kind of aqueous operation was only 

 subordinate, and more deeply lying causes for the forms of these cavi- 

 ties must be sought for in the configuration of the whole district, 

 and in the original mode of the formation of the valleys. This is the 

 more evident when we consider that many such basins are separated 

 by precipitous depressions only, similar to terrace-like declivities, 

 where there has been a perfect absence of any dams for the collection 

 or restraint of water. 



In the longitudinal valleys, on reaching which the Alpine streams 

 have already lost much of their force, considerable beds of gravel 

 occur (p. 212), which have been cut through by the rivers. Here 

 again river-erosion always appears of slight importance in relation to 

 the extent of these valleys. At the terminal gap-like openings of 

 these valleys the eroding power of the streams is abundantly percep- 

 tible ; but we can scarcely dare to attribute the cutting through of 

 these rocks to such a cause. The signs of erosion reach at the high- 

 est to some 100 feet [French], whilst the rock-walls are many thou- 

 sand feet high. It is remarked (p. 219), that the distinguished ob- 

 servers, L. von Buch, F. Hoffmann, O. d'Halloy, E. de Beaumont, 

 Thurmann, B. Studer, and others, have indeed proved in different 

 regions of the earth, that the formation of valleys is not effected by 

 casual erosion, but is most intimately connected with the causes that 

 gave rise to the general configuration of a district. In relation to 

 this are especially to be regarded the manifold windings of valleys, 

 the great change in their direction and extent ; whereas in mere ero- 

 sion, water would have taken the shortest and straightest passage. 

 It frequently happens also that a valley cuts through a lofty moun- 

 tain crest ; whilst, on the other hand, running water would have 

 taken an easier, and frequently already opened, course to one side. 

 Hoffmann has proved this particularly by the well-known Porta West- 

 phalica in the Weserthal ; Omalius d'Halloy cites very similar phe- 

 nomena in the course of the Rhone. 



The author considers, therefore, that although running water and 

 atmospheric influences effect important changes on the earth's sur- 

 face*, yet these operations have not been sufficient to give rise to the 

 extensive series of Alpine valleys. 



The real causes of the origin of these valleys appear to lie in a 

 series of successive elevations, associated with certain sinkings. The 

 great basins found at the extremities of the valleys and in their wider 

 developments, and repeated on a smaller scale on the declivities of 

 the mountains, seem especially to point to a retreat or withdrawal 



* A series of observations on erosion and weathering is given in Chapter xii. 

 of this work. 



