318 On the Forms assumed by Granite and Chieiss. 



tration of felspar between the slates, and the conversion of the 

 slaty mass into mica), is a view which has been adopted by the 

 most eminent geologists for many years, and which has latterly 

 been not a little confirmed by many acute observations and 

 reasonings of Messrs Dufrenoy and Elie de Beaumont in the 

 illustrations of the geognostical map of France. According to 

 this view, all the gneiss of Sweden and Finland involves the 

 supposition of the previous existence of Silurian strata over the 

 whole north of Europe ; for, where unaltered strata present 

 themselves in that region, they belong to the oldest strata of 

 the transition series. The action of this immense metamor- 

 phism terminates with the Gulf of Finland, and it does not 

 appear again in Russia. 



Every map of these northern countries shews quite distinct- 

 ly that the Gulf of Finland is a continuation, having the same 

 direction, and placed in the same latitude, of the strait which 

 separates Norway from Jutland; and, exactly in the same 

 direction and latitude likewise, Sweden is traversed by a hol- 

 low in which a great series of lakes succeed one another, by 

 means of which it becomes possible to convey ships of war 

 through the solid land from the North Sea to Stockholm, 

 without having recourse to the Baltic. It is only in this hollow 

 that the unaltered transition strata present themselves, up the 

 Motalelv and in the West Gothland plains, and the strata 

 contain the same organic remains which occur near Peters- 

 burg and Reval, and hence evidently belong to the Silurian 

 Series. 



It is not impossible that the remarkable mountains of West 

 Gothland, viz. Billing en with its prolongations, the Kinne- 

 kulle, and the Hallberg and Hunneberg, near Wenersborg, may 

 one day give us the key to the cause of these inlets being the 

 boundaries of the action of the granite and of the metamor- 

 phism of the slates into gneiss. The hills of which I have 

 sppken rise like castles above the plains, and are the only ones 

 whose steep acclimties are composed of unaltered fossiliferous 

 strata of the transition series. At a little distance from their 

 bases, such strata are no longer met with in the flat country. 

 Each hill is also covered by a mass, often of considerable di- 

 mensions, of a rock which is probably augitic, and is black 



