\22 M, Tlumholdt oil Volcanoes, [A to. 



to and receding from each other in groups occur in both hemi- 

 spheres, from the equator to the poles. On a distant island, 

 surrounded by strange plants, under a sky where the well- 

 known stars do not shine, the sailor recognises, often with glad 

 surprise, the clayslate which is the common rock of his native 

 country. 



This independence of the geognostical relations of places on 

 the present constitution of their climate, does not diminish, but 

 only gives a particular direction to the favourable effect upon the 



Erogress of geology and physical geognosy, which is produced 

 y numerous observations made in foreign countries. Every 

 expedition enriches natural history with new plants, and new 

 genera of animals ; at one time they are organic forms ranging 

 themselves with well-known types, and representing to us, in its 

 original perfection, a regularly woven, though often apparently 

 interrupted texture of animated creatures ; at another, they are 

 forms which appear to be isolated, as vestiges of genera which 

 have been destroyed, or as surprising members of groups still to 

 be discovered. Such a variety is not presented by the examina- 

 tion of the solid crust of the earth ; it rather reveals to us an 

 agreement, which excites the admiration of the geognost, 

 between the parts of which it is composed, in the superposition 

 of masses of different natures, and in their periodical repetition. 

 In the chain of the Andes, as well as in the central mountains 

 of Europe, one formation seems, as it were, to occasion the 

 existence of another; masses of the same character assume 

 similar forms : * mountains are formed by basalt and 



dolerite ; steep declivities by dolomite, porphyry, and quader- 

 sandstein; bell-shaped eminences and high-vaulted domes by 

 vitreous trachyte rich in felspar. 



In the most distant zones, larger crystals, as it were by inter- 

 nal evolution out of the more compact texture of the greater 

 mass, aggregate into subordinate beds, and thus frequently 

 announce the vicinity of a new and independent formation. 

 Thus is the whole inorganic world reflected, more or less clearly, 

 in every mountain of considerable extent ; but in order to ascer- 

 tain completely the most important phaenomena respecting the 

 composition, the relative age, and the origin of the different 

 species of rocks, observations from the most distant parts of the 

 earth must be compared together. Problems which had appeared 

 enigmatical to the geognost in his mother country are solved 

 near the equator. If distant zones do not furnish new species 

 of rocks, that is to say, unknown arrangements of simple sub- 

 stances, as has already been remarked, they yet teach us how to 

 discover the great laws which are every where the same, and 

 according to which, the different strata of the earth support each 



• In an imperfect translation of this paper, which has been forwarded to the Editor 

 from the Continent, a word here occurs which cannot be decyphered ; and on account of 

 other inaccuracies which it has been necessary to correct, unaided by the original, the 

 traaslatigo, as now given, is not to be regarded as exact in every particular. 



