ON THE 



STRUCTURE AND MODE OF ACTION 



OF 



VOLGANOS 



IN DIFFEKENT PAKTS OF THE EAETH. 



(This Memoir was read at a Public Meeting of the Academy, at 

 Berlin, on the 24th January, 1823.) 



WHEN we consider the influence exerted on the study of 

 nature during the last few centuries, by the extension of geo- 

 graphical knowledge and by means of scientific expeditions 

 to remote regions of the earth, we are at once made sensible 

 of the various character of this influence, according as the 

 investigations have been directed to the forms of the organic 

 world, the study of the inorganic crust of the earth, or to the 

 knowledge of rocks, their relative ages, and their origin. 

 Different vegetable and animal developments exist in every 

 division of the earth, whether it be on the plains, where, on 

 a level with the sea, the temperature varies with the latitude 

 and with the various inflections of the isothermal lines, or on 

 the steep declivity of mountain ranges, warmed by the direct 

 rays of the sun. Organic nature imparts to every region of 

 the globe its own characteristic physiognomy. But this 

 does not apply to the inorganic crust of the earth divested of 

 its vegetable covering, for everywhere, in both hemispheres, 

 from the equator to the poles, the same rocks are found 

 grouped with some relation to each other, either of attrac- 

 tion or repulsion. In distant lands, surrounded by strange 



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