IS^G.J MURCHISON ON THE SCANDINAVIAN DRIFT. 361 



pose, in icebergs or ice-floes, in the manner already explained in the 

 work on Russia and the Ural Mountains. 



In speaking of the erratics of Gothland, it is well to indicate the 

 marked distinction between the ancient and powerfully rolled drift 

 and any materials which are now wafted to its shores. The former 

 is composed of crystalline materials all derived from the north *, 

 and these crystalline and rounded fragments, together with much 

 hard quartzose red sandstone, also only known in the north, are mixed 

 with limestone of the island and a good deal of sand. In corrobora- 

 tion of this, we see that the subjacent limestone has been furrowed 

 and scratched, I believe by the weight and friction of those very 

 masses which have lain upon it until removed by the hands of man ; 

 and in the north of Gothland, where I principally observed them, 

 these markings are directed from N.N.E. to S.S.W. Now, whether 

 the foreign materials may have been derived from the northern parts 

 of Finland or from the north of Sweden (and the latter supposition 

 might be inferred from the character of the porphyry and hard red 

 sandstone) is immaterial for the present argument. Doubtless, 

 under the extensive submarine area in which I consider that this 

 drift was transported, the powerful currents of translation referred 

 to (caused, as I imagine, by sudden heaves of the Scandinavian con- 

 tinent), may, by the form of the bottom of the sea and other causes, 

 have been in some tracts directed to the east, and in others to the 

 west of north ; for throughout all the mainland of Sweden, the linear 

 direction of the gravel-banks or Osar and the wearing and striation 

 of the subjacent rocks vary from east to west of north in different 

 districts and according to the general outline of the land. But 

 that to which I wish now to call attention is, that in no instance is 

 a fragment of chalk or chalk-flint to be found in such ancient de- 

 tritus, though these rocks exist abundantly in the countries to the 

 south and S.W. of Gothland ; whilst, on the other hand, the devious 

 and uncertain tides of the present sea, differing entirely from the 

 ancient currents, and acting quite as much from the south as from 

 the north, do occasionally waft to the shores of this island (probably 

 in fragments of ice) lumps of chalk and flint, derived from the cliffs 

 of Rugen, Bornholm or Denmark. 



Lastly, in reference to Gothland, I annex a series of diagrams 

 which sufficiently explain my hypothetical views respecting the con- 

 dition of the island at different periods after the first consolidation 

 of the limestone floor of which it is composed. 



The first of these (fig. 2) represents a portion of the Upper Si- 

 lurian limestone, of which the island is composed, when it laid be- 

 neath the sea, long after the consolidation of the rock, and when its 

 surface had been partially eroded by ordinary submarine action. 



Fig. 3 exhibits the same mass of limestone exposed to a powerful 

 denudation on its northern flank (N.W. or N.E., as the case may 

 be) and also along its upper surface, by the passage of great heaps 



* This is proved by the character of the granites and porphyries therein con- 

 tauied, none of which occur to the south of Gothland. 



