1846.] MURCHISON ON THE GEOLOGY OF DALECARLIA, ETC. 13 



range of hills, have perforated, and in some cases overflowed, bol^ 

 the Silurian rocks and the Old red sandstone of that territory. 



In addition to an excursion into Elf Dal, we threaded the por- 

 phyry range which separates the Siljan from the Wenjan Lake, 

 passing by the iron forge called Siljan-fors to the glass works of 

 Johannisholm, situated at the south end of the last-mentioned sheet 

 of water. 



The sides of this lake, whose length is about seven miles from 

 N.N.W. to S.S.E. and its mean width about a mile and a half, are of 

 no great altitude. The outline on the western shore is however 

 much more pronounced and elevated, and consists either of por- 

 phyry, which, as seen in the buttresses near Johannisholm, has a 

 grey felspathic base enclosing small crystals of black hornblende, 

 or else of a red porphyry with greenish and grey crystals. This latter 

 rock, like the red porphyry alluded to near Skatunge, is as regularly 

 stratified and jointed as any sedimentary rock, its strike being nearly 

 north and south, and the beds either vertical or dipping at 70° to the 

 west. 



Enclosed between these porphyry ridges on the west side of 

 the lake and those of Siljan-fors, which range up to Elf Dal, is a 

 considerable breadth of sandstone, which, from its characters and 

 intimate association with the porphyry, is, I have no doubt, of the 

 same age as the rocks at Ringerigge near Christiania, and the equi- 

 valent of the Old red sandstone of Britain*. This sandstone, which 

 constitutes in fact the western bank of the lake, is there dislocated 

 and piled up in the remarkable manner described in a previous 

 memoir. The rock is with difficulty observed as a solid mass hi situ ; 

 but from the points at which we detected it, as well as from informa- 

 tion we received from the Magister V/estrom, that the rock is ex- 

 tensively quarried at Wenjan, it would appear that throughout a 

 great space it is nearly horizontal. 



That such is the position of the fundamental rock might, indeed, 

 also be inferred from the fact, that throughout the space of the few 

 miles which we travelled amid its numerous and colossal angular 

 fragments the sandstone exhibited no varieties, all the specimens 

 being referable to the same stratum ; whereas, if the beds had been 

 inclined, we ought to have met with conglomerates, flagstones and 

 thick-bedded hard sandstones, &c., similar to the succession which 

 the formation presents in Norway, portions of which rocks I have 

 already adverted to as occurring in the district east of Moraf. Heje 

 the sandstone is uniformly a finely laminated, slightly micaceous hard 

 rock, and is for the most part of mottled light red and grey, red, 

 green and yellow colours. In short, it is undistinguishable from 

 some well-known forms of the British Old red sandstone, like which, 



* These relations having been incorrectly expressed in a woodcut published in 

 the first volume of the Quarterly Journal of the Geological Society, the reader is 

 referred to the second volume of that work, Part ii. p. 71, and to ' Russia in Europe 

 and the Ural Mountains/ vol. i. p 13. 



t See a further account of these angular blocks, Quart. Journ. Geol. Soc, vol. ii. 

 p. 374. 



