FORCHHAMMER ON THE BOULDER FORMATION. 379 



a broad sound. That the Gulf of Bothnia has thus been united 

 with the Cattegat, the open sea having reached to the gulf, is clear 

 from the great Aos of Gefle and Stockholm, which contains marine 

 fossils. But the Gulf of Bothnia has also been connected with the 

 White Sea, where, in the neighbourhood of Uleaburg, a consider- 

 able depression towards its shores may be observed.* In the same 

 way Norway and Sweden in former times were detached from 

 Finland, a complete water communication existing from the White 

 Sea through the Gulf of Bothnia, and the northern part of the 

 Ost See to the Cattegat. This former communication may explain 

 why the fossil remains of niollusca found on the west coast of 

 Sweden and the north coast of Jutland have on the whole a more 

 northern character than the species at present living in the Cat- 

 tegat : but other causes besides these, and noticed by me elsewhere, 

 must also be taken into consideration with reference to this sub- 

 ject. The gradual elevation of Scandinavia must from time to 

 time have changed these relations, diminishing the communication 

 of the Gulf of Bothnia with the sea till the separation was finally 

 effected. Now the mass of water displaced by the elevation of so 

 large a portion of the sea bottom, must necessarily endeavour to 

 find an outlet, and escape either towards the north into the White 

 Sea, or westward into the Cattegat. But in both these directions 

 they would be opposed by a wall of granite, while the obstacles 

 towards the south, consisting of soft, sandy, and scarcely consoli- 

 dated rocks of the Silurian series, offered but little resistance, and 

 were therefore broken through to form a passage. To effect this, 

 however, a powerful current from north to south must have been 

 in motion, and the deep indentation on the Prussian coast, which 

 forms the Gulf of Konigsberg, appears to mark this event. 



The main stream must then have been deflected towards the 

 south-west by the beating back of the waves, and has left indica- 

 tions of its passage in the island of Bornholm (which interfered 

 with its progress) at a height of 250 feet above the present sea- 

 level.f The continuation of the south-western current is marked 

 by the separation effected between Rugen and Moen, and the deeply 

 intersected bay of Lubeck. 



The waves being reflected back from the coast, and acting again 

 upon the advancing wave, the current must then have taken a 

 diagonal direction towards the north, and a glance at the map will 

 show that the gulf on the western side of the Cimbrian peninsula 

 gradually takes a more northerly direction, till it loses itself in the 

 so-called Kallovig. Now, I am aware that it is always dangerous 

 to construct theories with regard to marine currents by examining 



* I owe to General Lafren of Stockholm the- information that communica- 

 tion hy water was still kept up in time of floods, even so lately as at the com- 

 mencement of the last century. 



f Up to this height for instance is the granite floor of the island covered hy 

 a fat marly clay, full of fragments of all kinds of Silurian rocks just as they 

 occur in Gothland and Oeland. 



