1846.] MURCHISON ON THE SCANDINAVIAN DRIFT. 379 



Wenjan Lake, whilst the local angular blocks in situ (b, b, b), iden- 

 tical in structure with the parent rock (a), are strikingly contrasted 



Fig. 17. 



Ancient level of lake. 







Hill of Kamenibor. 



c 



l^8»— 





^ L^ 



^^^ 



/«?;«>rp=;<*;:s::=^5*=^>N 



Siliceous sandstone. 



with the far-transported crystalline erratics (/) which occupy the 

 higher portion of the hill. 



Whether this hypothesis, founded on a cause now in operation, 

 be accepted or not, to account for the Dalecarlian phaenomenon, 

 no one can view these great broken and remarkable piles on level 

 surfaces without seeing that they are the original sources from 

 whence many of the angular erratics which cover the tracts to the 

 south of these have been derived, and no one has yet ventured to 

 offer any rational explanation of how such masses should have tra- 

 velled hundreds of miles and yet have preserved their angularity, 

 except by supposing that they were transported by floating ice. 

 The examination of North Sweden and the ridges in question leads 

 me to believe that icebergs, as derived from terrestrial glaciers, do 

 not in themselves offer a sufficient cause for all the features of the 

 erratic phsenomena; but that if large and lofty icebergs were re- 

 quired to float blocks to great distances, we must also imagine 

 that sea-formed sheet-ice, encompassing certain shattered and rocky 

 ridges and islets, may also have urged southwards for certain 

 distances on ice-floes or ice-rafts, a great number of those an- 

 gular erratics which extend over the northern and central parts of 

 Sweden. 



In offering these hypothetical views, I care little for their adop- 

 tion or rejection. My main object in thus bringing additional 

 facts before geologists is to show, that however inadequate my own 

 theory may be to account for all the northern superficial phaenomena 

 in question, strong reasons at all events exist for the restriction 

 of the terrestrial glacier theory to its legitimate domain ; and not 

 doubting that many surface appearances (undoubtedly all those in 

 flat regions) have been produced by nothing but aqueous drift, put 

 in motion lay vibrations of the crust of the earth, which brought 

 into action the great transporting power of water, whilst other de- 

 bacles were caused by glaciers, and others again by the breaking 

 up of former glaciers and glacial seas, it is clear that in reference 

 to this subject our future business as geologists is, not to contend 

 for the exclusive operation of any one of these causes, but to en- 

 deavour calmly and patiently to work out each case on its own 

 merits, instead of appealing to one universal cause for the produc- 

 tion of rounded, polished, abraded, grooved and striated rock-sur- 

 faces. 



And here I would furtiier observe, tiiat liowevcr it may be aiyued, 



