16 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 18, 



observes, " the peculiarities in the distribution of the animals of the 

 glacial epoch, and in the relations of the existing fauna and flora of 

 Greenland, Iceland and Northern Europe, are such as strongly to im- 

 press upon my mind that the close of the glacial epoch was marked 

 by the gradual submergence of some great northern land*." Now 

 it is evident that such a continent or extension of land must not only 

 have given a more arctic character to the climate of Great Britain, 

 but also have had the effect of deflecting upon the north-western 

 shores of the British Isles the full power of any currents from the 

 north and west. It is easy to imagine such a distribution of the land 

 on the American continent, and such a change in the sea-bottom in- 

 tervening between it and the British Isles, that the union between 

 the gulf-stream and the great north-polar current which now takes 

 place about latitude 42" north, and longitude 45° west, shall have 

 been at a point much more eastward and northerly. And we may 

 thus account for that remarkable pheenomenon noticed by Professor 

 Forbes in the glacial deposits of Great Britain, of a southern fauna 

 passing at once into a boreal one without any intervening m.ore tem- 

 perate type. What I mean is, that there are now at work natural 

 agencies sufficient to have produced all the pheenomena of the boul- 

 der-clay and drift-gravel series, if we but allow the probability of a 

 different distribution of the relative proportion of land and water in 

 our northern hemisphere, and a consequent alteration in climate, and 

 in the direction of oceanic currents. 



As far as the northern portion of Scotland is concerned, I see no 

 difficulty in accounting for all the phenomena of the glacial deposits 

 on the principles and through the agencies to which I have just al- 

 luded. Perhaps they are capable of a still wider applicationf . 



The conclusions to which my examination hitherto of the phaeno- 

 mena connected with the newer pleiocene gravels, sands and clays, 

 has led me, may be thus briefly summed up ; viz. 



That at the commencement of the period of the boulder-clay, the 

 relative level of the sea and land in the British Isles was not greatly 

 different from what it now is, and that the main features of the 

 country had been already assumed. 



That a great current, originating probably in the union of a north- 

 polar current with a modification of the present gulf-stream, was 

 constantly setting in upon the northern and western shores of Great 

 Britain and Ireland, mth a climate of an arctic or subarctic character. 



That a gradual submergence of the area of the British Isles took 

 place to the extent, in some parts, of at least 1600 feet, and subse- 

 quentl}'' a gradual emergence of the same extent. 



That the former event is chronicled by the scratched rocks and 

 boulders of the true boulder-clay series ; the latter is marked by the 

 more elevated terraces or lower extended platforms of rolled boulders 

 and gravel, which are in many instances a redistribution in great part 

 of the materials of the boulder- clay, sometimes regularly stratified. 



That during the uprising the more rigorous conditions of the 



* Memoirs of the Geological Survey of Great Britain, vol. i. p. 399. 

 t These vievrs are not supposed to exclude the action of glaciers during the 

 same period. 



