184^.] MURCHISON ON THE GEOLOGY OF DALECARLIA, ETC. S 



consideration ; and as my sole object at present is correct classifica- 

 tion and not topographical accuracy, the precise limits of such de- 

 posits are left to be subsequently defined by Swedish observers. At 

 the same time, whilst it is hoped that tlie accompanying diagrams 

 (see Plate I.) will sufficiently illustrate the chief phsenomena and the 

 order of the strata, the reader will do well to refer to Forsell's 

 map of Sweden *. 



1 . Dalecarlia and the surrounding country. 



The portion of Dalecarlia in which transition rocks are known to 

 occur (from the descriptions of Hisinger accompanied by a detailed 

 map), includes the extensive parishes of Rattvik, Ore, Orsa, Mora and 

 SoUeron ; or in other words, it is the country circumscribed by and 

 in parts extending beyond the Lakes Siljan, Orsa-sjon, Skatunge, 

 Oresjon and Garsjon. These lakes, fed by streams from the higher 

 country, are nothing more than expanded and gently meandering 

 tributaries of the great river Dal-Elv, which flowing from west to 

 east to the south of Fahlun, finds its way, through other and smaller 

 lakes, to the Baltic Sea south of Gefle. 



Bounded on the south, the east and the north by regions of gneiss 

 and other slaty crystalline rocks, as well as intercalated granites 

 and greenstones of different dates, the chief palaeozoic rocks of this 

 tract of Dalecarlia form merely a ragged belt surrounding a dome of 

 porphyrj'-. Surrounded by the lakes in question, this dome is a nearly 

 circular mass of about twenty English miles in diameter, the inner 

 portion of which has been left blank upon the geological map of 

 Hisinger. From all that we could ascertain by examining its edges, 

 or by information from persons who have penetrated further than our- 

 selves (there being no roads in the greater part of these woodlands), 

 this district is occupied by granitic as well as porphyritic rocks, 

 which, to judge from the evidences that fell under our notice, must 

 all have been erupted, or at all events were thrown up posterior to the 

 deposit of the Silurian strata, and probably after that of the Old red 

 sandstone. 



The crystalline central dome-shaped mass rises to about a thou- 

 sand feet above the sea, and contains some small upland lakes or 

 tarns. On the whole, this tract is geologically analogous to the cen- 

 tral masses of the Christiania district already described, wherein por- 

 phyritic, hypersthenic and younger granitic rocks have burst through, 

 and dislocated the Silurian strata. 



In the Table attached to his Map, Hisinger has correctly represented 



* I must here express ray great obligations and those of my friend to Baron 

 Berzelius, who not only furnished us with Hisinger's district maps, but also gave us 

 every facility for examining the collections under the superintendence of Professor 

 Mosander and Professor Loven, and further made us known to M. Sefstrom and 

 M. Weggehn. The latter gentleman, who has examined the rocks of Dalecarlia 

 in some detail, gave us some useful notes respecting them. 



B 2 



