18i6.] MURCHISON ON THE GEOLOGY OF DALECARLIA, ETC. 7 



pass on the north into a porphyry. The natural inference from this 

 section (if it occurred in an undisturbed region) would be that the 

 beds of sandstone and conglomerate were of older date than the 

 fossiliferous Lower Silurian rocks ; but subsequent observation ren- 

 dered this point very doubtful. By following the Orthoceratite 

 Silurian limestone upon its strike to the N.E., it was evident, that 

 upon the shoulder of the Degeberga above Wangsgarde, the por- 

 phyry of that mountain (a red felspathic rock) was in absolute con- 

 tact with the limestone, which is there a thin-bedded rock, having 

 somewhat the aspect of marble, but still offering no very distinct 

 evidence of having been altered. That the strike and inclination of 

 these beds had been deranged and changed by the invasion of the 

 eruptive rock was made more evident, by trending the flank of the 

 headland of porphyry which sweeps eastwards from the valley above 

 the vale of Orsa, where we found that the limestone also changed 

 its direction and wheeled round to the E.N.E., the strata dipping 

 from 50° to 75° to the N.N.W. In one spot, indeed, we observed 

 the edges of the calcareous strata expanded over a width of not less 

 than 250 paces on the slopes of the hill or between the porphyry 

 and the lake ; both the red Orthoceratite rock, the gray and green 

 limestone with Lituites and other fossils being exposed. Again, 

 between this spot and the valley of the Ore we saw (near the village 

 of Enon) portions of a black schist charged with Graptolites and a 

 very minute Orthis, which seemed toioverlie the limestone, a small 

 advanced promontory of which we detected in a highly inclined 

 position striking across the brook above the bridge from N.N.E. to 

 S.S.W. But on ascending the banks of this stream (which is not 

 marked either in the maps of Forsell or of Hisinger), we looked in 

 vain for any connection of those masses with the great body of 

 Orthoceratite limestone higher up the hill to the south. The stream 

 is seen to run through a gorge of porphyry, the protrusion of which 

 has evidently dismembered the strata. Here, as elsewhere then, 

 we had to decipher the probable original relations of mere detached 

 fragments of the Silurian rocks, and all that we could determine 

 from their character and fossils was, that as a whole they clearly be- 

 longed to the Lower Silurian group. We next proceeded along the 

 central dome of eruptive rocks (porphyry in one part and granite 

 or granitello in another) on its northern and eastern faces, first by 

 ascending the Ore Alf from Orsa to Skatunge, and thence by fol- 

 lowing the road from the latter place to Ore, Osmundsberg, Boda 

 and the waterfall called Styggfors, in order to connect if possible the 

 whetstone and shale of the valley with the well-known horizon of 

 the Orthoceratite limestone^"'. 



Judging from the deep incoherent sands, devoid of nearly all 

 other detritus, which occupy the lower part of the valley, and have 

 the appearance of being nothing more than the disintegration of the 

 whetstone or " Slepsten," that rock may be presumed to form the 

 basis of the lower and undisturbed portion of this tract. For, on 



* From the mouth of the river Ore this whetstone is largly exported, being con-. 

 veyed by the Orsa and Siljan lakes to different parts of Sweden. 



