﻿COTTA ON THE INTERNAL STRUCTURE OF MOUNTAINS. 119 



On the Internal Structure of Mountains. By B. Cotta. 



[Leonhard u. Bronn's Jahrb. f. Min. u.s.w. 1851, p. 181-2.] 



In a letter to Dr. K. C. v. Leonhard, the author states that in a short 

 memoir on the Internal Structure of Mountains, lately published at 

 Freiberg, he has attempted the physiology, as it were, of mountains, 

 in showing the different phases of their formation and destruction. 

 The chief results arrived at are — 



1. The mountains did not suddenly arise, but were formed by 

 degrees, sometimes during very long periods of time. 



2. For their position and direction there are as yet no general laws 

 positively known. 



3. All true mountains are results of elevatory volcanic (plutonic) 

 action. 



4. The majority, however, in their present form are at the same 

 time the result of a later destructive process (the action of water) in 

 very unequal degrees. 



5. The mountain-elevations are to be distinguished as local from 

 the continental elevations of great tracts of land, which latter maybe 

 bare swellings, unless eruptive rocks find a local vent. 



6. Horizontal forms of the mountains correspond in some degree 

 to the grouping of the volcanos, — the single mountain-masses (Massen- 

 Gebirge) to the central volcanos (Vulkan-Gruppen), the mountain- 

 chains to the lines of volcanos (Vulkan-Reihen) . 



7. Of the origin of mountains the author distinguishes three prin- 

 cipal kinds, and very many forms of combination, and stages of deve- 

 lopment and destruction. The three kinds of origin are : — 



a. By the efflux and superficial accumulation of eruptive rocks ; — 



volcanic mountains. 



b. By the elevation of existing hard portions of the earth's crust, 



caused by eruptive rocks penetrating upwards ; — plutonic 

 mountains. 



c. By lateral pressure, and, in consequence thereof, the folding of 



existing hard portions of the earth's crust. 



8. Several of these kinds of development, however, sometimes occur 

 in combination with one another. 



9. The mountains originating in the elevation of the existing hard 

 portions of the earth's crust, owing to the upward pressure and pe- 

 netration of eruptive masses, exhibit the most manifold diversity of 

 stages of destruction, whereby they fall into mountains with folded 

 strata [Falten-Gebirge], crystalline slate mountains, and central mass 

 mountains of upper, middle, and lower section. 



10. The mountains with folded strata of this sort, however, are not 

 always distinguishable from those originating in lateral pressure. 



11. Of especial importance in judging of the relative age of the 

 mountains, — besides the distinction of elevated and non-elevated beds 

 brought forward by E. de Beaumont, — is the fixing of the mountain- 

 chains as lines of separation between deposits during determined pe- 

 riods ; — recognizable by dissimilar characters in the series of sedi- 

 mentary formations on two or more sides. 



