226 Professor Hoffmann on the Geological Investigations 



neral application which their proposer endeavoured to give 

 them, yet they have undoubtedly been of the greatest advan- 

 tage to the science. Not only have new facts been discovered, 

 but attention has, in consequence, been more pointedly awa- 

 kened to a number of appearances whose investigation has 

 produced new ideas respecting the structure of individual por- 

 tions of the crust of the earth. 



Elevation of mountain-chains. — A great advancement of 

 our ideas regarding the elevation of mountain- chains is im- 

 mediately connected with the application of these views. 

 During these investigations, the observation made by Saussure 

 was very successfully taken up, that in the Alps, not only the 

 central chain has a certain prevailing chief longitudinal direc- 

 tion, but that all the secondary chains run parallel, and in 

 such a manner, that they constantly present their steeper 

 acclivities to the principal chain, and their gentler accli- 

 vities to the edges of the mountain-mass. Von Buch con- 

 vinced himself, during his numerous journeys in central Eu- 

 rope, of the fact, which is also evident in geognostical maps, 

 that in all elevations which rise up pretty prominently, the 

 same phenomenon recurs, just as in the larger mountains, with 

 great distinctness. 



The explanation of this remarkable fact, which no preceding 

 geologist had endeavoured to investigate, was no longer far dis- 

 tant; for, an entirely similar arrangement had been already found 

 in the linear distribution of volcanos on the surface of the earth. 

 We have already seen, that these bands of volcanos also, not 

 unfrequently run parallel to the chief longitudinal direction 

 of the mountains, and that they protrude on longitudinal 

 fissures which were formed at the time of their eruption. 

 Now, Buch has distinctly and incontrovertibly shewn, that 

 mountains are produced by elevation ; their central chains 

 are usually composed of plutonic, crystalline-granular rocks, 

 which had not, till subsequently, intruded themselves among 

 the previously-formed combination of strata ; their chief longi- 

 tudinal direction must therefore be the direction of the fissure 

 by which these broke forth at the period of the elevation 

 of the mountains ; and, when we observe, on both its sides, 

 the precipitous acclivities of the secondary chains always 



