ANCIENT GLACIERS IN EASTERN HEMISPHERE. 151 



absence of structure, in many respects quite inconsistent 

 with such an origin, and contains no shells or other remains 

 of marine creatures, it must be pointed out that no theory 

 of marine notation will explain the distribution of the 

 erratics, and especially their concentration in such num- 

 bers at a station sixty or seventy miles from their source. 



" Upon the land-ice hypothesis this difficulty disappears. 

 During the early stages of the Glacial period the Welsh 

 ice had the whole of the Severn Valley at its mercy, and a 

 great glacier was thrust down from Arenig, or some other 

 point in central Wales, having an initial direction, broadly 

 speaking, from west to east. This glacier extended across 

 the valley of the Severn, sweeping past the Wrekin, whence 

 it carried blocks of the very characteristic rocks to be 

 lodged as boulders near Lichfield ; and it probably formed 

 its terminal moraine along the line indicated. (See lozenge- 

 shaped marks on the map.) As the ice in the north gath- 

 ered volume it produced the great Irish Sea Glacier, which 

 pressed inland and down the Yale of Severn in the manner 

 I have described, and brushed the relatively small Welsh 

 stream out of its path, and laid down its own terminal 

 moraine in the space between the Welsh border and the 

 Lickey Hills. It seems probable that the Welsh stream 

 came mainly down the Vale of Llangollen, and thence to 

 the Lickey Hills. Boulders of Welsh rocks occur in the 

 intervening tract by ones and twos, with occasional large 

 clusters, the preservation of any more connected trail 

 being rendered impossible by the great discharge of water 

 from the front of the Irish Sea Glacier, and the distrib- 

 uting action of the glacier itself. 



" Within the area in England and Wales covered by the 

 Irish Sea Glacier all the phenomena point to the action of 

 land-ice, with the inevitable concomitants of sub-glacial 

 streams, extra-morainic lakes, etc. There is nothing to 

 suggest marine conditions in any form except the occur- 

 rence of shells or shell fragments ; and these present so 



