376 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 8, 



navia, which stretching over a wide expanse in these parts, has been 

 thus broken up without exhibiting those changes of lithological 

 character which are so conspicuous wherever deep escarpments, 

 like that of the Tyrifiord near Christiania, are exposed, and where 

 conglomerates and hard siliceous beds occupy the summit, thick- 

 bedded and earthy sandstone the centre, and flagstones the base. 



Now, notwithstanding the almost perfect angularity of these broken 

 masses (which are just like the fragments that fall from natural 

 joints in a quarry), it is curious to observe that occasionally (though 

 rarely) a small rounded boulder of porphyry may be detected be- 

 tween their interstices, and that here and there a considerable quan- 

 tity of sandstone and smaller detritus is mixed with loose sand, and 

 is seen lying around the base and lower edges of the blocks. This 

 fact seems to prove, that by whatever cause the blocks were dislo- 

 cated, water has since passed over and between them, though not 

 with such power in this tract as to abrade them, and merely trans- 

 porting a very few foreign pebbles, has only had sufficient energy 

 to clear away much of the intermediate loose sand and smaller 

 broken materials, converting them into the fragmentary shingle 

 which we see in the trainees to the south of this sandstone range. 

 From these facts* I would infer, that the currents which proceeded 

 to those countries from Scandinavia acted with much greater in- 

 tensity on certain lines than on others ; in some leaving " cherres " 

 of broken rock almost unaltered, like the one now under considera- 

 tion, and in others powerfully abrading the surface by hurling over 

 it prodigious masses of detritus. 



In quitting the region of Silurian rocks, Old red sandstone and 

 porphyry at Furadal, on the northern frontier of Dalecarlia, and in 

 travelling thence westwards towards Alfta, all trace of porphyritic 

 or sandstone detritus vanishes as soon as we regain, on a more 

 northern parallel than that just described, the region of granitic 

 gneiss, large tracts of which exhibit the usual phaenomena of an- 

 gular gneiss blocks in situ, or the same material partially trans- 

 ported to the summits of other rocks, or osar of sand, clay, sand or 

 gravel, as the case might be : all the detritus is granitic or gneiss- 

 ose ; and thus the proofs are complete respecting the independence 

 of the trainees of Scandinavian drift, as derived from the normal 

 positions of the rocks in situ to the north of them. 



In our published work on Russia, my friends and myself have en- 

 deavoured to explain at some length our ideas upon the whole subject 

 of the northern detritus, and the evidence obtained during our last 

 tour seems materially to strengthen the probability, that in respect to 

 all the low countries of Scandinavia, the assumption of heavy masses 

 of drift having been swept over the surface by powerful aqueous 

 currents will alone explain the phasnomenon of the abrasion and 

 striation of the subjacent rocks, and that the outlines and relations 



* This view is indeed also sustained by all the superficial phaenomena of Russia, 

 Poland and Northern Germany, to which countries the Scandinavian gravel and 

 worn detritus have been propelled in distinct trainees from north to south, each one 

 separated by tracts in which few or no erratic materials are found. 



