Joshua Wilson — On the Olacial Epoch. 413 



of insect life. These remains consist solely of fragments of wings 

 and a few segments of the abdomen ; why the other hard portions of 

 these animals are not mixed up with the rest is a mystery. They 

 were probably the spoils of the land through which the ancient 

 river flowed, hy means of occasional overflowings. This is the more 

 probable as the Purbeck series is generally recognized as an estuary 

 deposit. 



Amongst the most interesting of the fossils are those of the 

 crustaceous order Isopoda (well represented by a single species, the 

 ArchoBoniscus Brodiei, Milne Edw.), which are very rarely met 

 with in the fossil state. 



(^To be concluded in our next Number.) 



IV. — On the Glacial Epoch of Great Britain. 

 By Joshua "Wilson. 



IT must be admitted that if during the Glacial period an arctic 

 current, similar to that which now sweeps along the east coast of 

 Korth America, were to pass over the submerged portions of our 

 island, there is no reason why the climate of this country should not 

 assimilate to that of Labrador, where there is now perpetual frozen 

 ground in the latitude of Liverpool. The question then is, what 

 evidence have we that such a current existed at the commencement 

 of the Glacial epoch ? Have we not the evidence of the strige on the 

 rocks and mountains of the Scandinavian peninsula, as well as on those 

 of our own country, to show that, during the period of the submer- 

 gence of these districts, icebergs were driven by an arctic current from 

 the north-east to the south-west ? — that the Polar Sea extended from 

 the White Sea to the entrance of the Baltic, spreading southward 

 over Germany to the confines of Switzerland, which can be traced by 

 the deposited boulders and other ice- transported materials? Then, as 

 to the cause of this return current. It must be evident that the Gulf- 

 stream at that date could not have flowed in its present direction. 

 The arctic current coming down the Baltic must have thrown it 

 further to the west, so that in all probability in its northern progress 

 it would impinge on the east coast of Greenland and the Island of 

 Spitzbergen ; then being deflected by the polar ice, it would return by 

 the way of the White Sea and the Baltic, so completing the circuit. 



As the land was gradually upheaved, we may conclude that in the 

 first instance the larger icebergs would be detained ; but there might 

 be a considerable quantity of polar ice transported, until at length 

 there might be only the cold current left. And when, by the upheaval 

 of the land, this was finally stopped, the Gulf-stream would be di- 

 verted to its present channel, and by its genial warmth would 

 speedily terminate the Glacial period. The next question is, at 

 what geological date did this change take place ? On this I agree 

 with A. Geikie, F.R.S., in his "Scenery of Scotland" (page 320), 

 where he mentions a raised beach, about 40 feet above high-water 

 mark, in which arctic shells have been found, which he considers to 

 have dated from the latter part of the Glacial period. The next 



