308 Proceedings of the Boyal Physiccd Society. 



of feet in thickness, and would have no difficulty in filling 

 to overflowing a basin which we know ,from the present 

 depth of the German Ocean to have been only 200 or 300 

 feet in depth. The ice-streams coming from opposite directions 

 would meet and press against each other with a force pro- 

 portional to the impulse each had. The ice from the eastern 

 side — that' is, from the highlands of Sweden and Norway — 

 would be far greater in amount and power than that which 

 flowed in from the western side — from the Highlands of 

 Scotland, just as the area and height of the . Scandinavian 

 mountains surpass those of Scotland. In consequence of the 

 superior volume and force of the Scandinavian ice, the ice 

 which streamed out from Scotland would be pushed back 

 upon itself, and forced to heap itself up against the land, 

 and if the land was low, to override and pass over it, 

 carrying with it all the dehris of mud or stones it had 

 originally, or had picked up by the way. This theory was 

 confirmed by the stones found in the boulder clay of Caith- 

 ness. Many of these were known, by the researches of Mr 

 Dick of Thurso and Mr Charles Peach, to consist of chalk 

 flints and fragments of oolitic limestone, which had come 

 from the southern shores of the Moray Firth, and which 

 could only be carried to Caithness by ice flowing from thence, 

 and crossing over the basin of the Moray Firth, from which 

 also it could easily get the shells so abundantly scattered 

 through the Caithness boulder clay. This was the theory 

 which Dr Croll applied to the solution of the problem, and it 

 fitted into all the circumstances of the case so completely, 

 that he had no doubt of its truth. 



But it was with only one consequence of this state of 

 things that we are concerned at present. This was, that the 

 Scottish stream of ice having been met with one greater in 

 volume and force than itself, would be dammed back, or 

 heaped up, as it were, till it rose to a height almost equal to 

 that opposed to it, and of course, as the Scandinavian ice was 

 many hundreds of feet in thickness, the Scottish ice would 

 be almost as thick, and would be piled up upon the land till 

 it overtopped the highest hills on the eastern slope of Scot- 

 land. Now, if such a result had taken place in the glacial 



