Scientific Intelligence — Geology. 181 



verer of iodine in the atmosphere, is continuing Lis researches on 

 this subject. The general result of his latest observations leads him 

 to conclude, that the nearer he approached the Alps the smaller was 

 the quantity of iodine, and that in some districts, as Maurienne, 

 this atmosphere contained no iodine. 



GEOLOGY. 



3. 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 shewing 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 de- 

 grees, 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 may 

 be bare swellings, unless eruptive rocks find a local vent. 



6. Horizontal forms of the mountains correspond in some degree 

 to the grouping of the volcanoes, — the single mountain masses (Mas- 

 sen-Gebirge) to the central volcanoes ( Vulkan-Gruppen), the moun- 

 tain chains to the lines of volcanoes (Vulkan-Reihen). 



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

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

 velopment 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 

 penetration of eruptive masses, exhibit the most manifold diversity 

 of stages of destruction, whereby they fall into mountains with folded 



