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upon one another, form those rounded cones, 

 that are found so frequently in the Mittelgebirge 

 in Bohemia, nearBilin, the country of phonolites. 

 The following is the result of my partial obser- 

 vations. 



The gruenstein, which at first alternated with 

 strata of serpentine, or was connected with this 

 rock by insensible transitions, is seen alone, 

 sometimes in strata considerably inclined, and 

 sometimes in balls with concentric strata, im- 

 bedded in strata of the same substance. It lies, 

 near Malpasso, on green slates, steatitic, mingled 

 with hornblende, destitute of mica and grains 

 of quartz, dipping like the gruensteins 45° to- 

 ward the North, and directed like them N. 

 75° W. 



A great sterility prevails where these green 

 slates predominate, no doubt on account of the 

 magnesia they contain; which (as is proved by 

 the magnesian limestone of England*) is very 

 inimical to vegetation. The dip of the green 

 slates remains the same ; but by degrees the 

 direction of their strata becomes parallel to the 

 general direction of the primitive rocks of the 

 chain of the coast. At Piedras Azules, these 

 slates, mingled with hornblende, cover in con- 



* Magnesian limestone, straw yellow, with madrepores - } 

 beneath red marl, or muriatiferous red sandstone. 



