Glaciers and. Icebergs in Scotland. 139 



supposed, on good grounds, that icebergs produce similar 

 effects. As these bodies are always formed in the vicinity 

 of land, there is little doubt that stones and gravel, such as 

 are occasionally seen embedded in them, will generally be 

 found adhering to their bottoiu. Armed with these sub- 

 stances, a floating mass of ice, measuring a thousand feet in 

 length, and breadth, and depth — and there are some much 

 larger — must exert a vast abrading force on the submarine 

 rocks with which it comes in contact. It is only in this way 

 we can account for the groovings on rocks in flat districts 

 where no mountains exist to generate glaciers, or where the 

 groovings run in a direction transverse to that in which a 

 glacier must have moved. Striae, for instance, were found 

 by Mr Murchison on rocks in the plains of Russia, remote 

 from any mountains. It was clear that they could not be 

 the work of glaciers, but in speculating on their possible 

 cause, it occurred to him that they might be produced by 

 icebergs ; and this idea has, I believe, been pretty generally 

 received as the best explanation of the phenomena. Again, 

 in the low country on the shores of the Forth, wherever a 

 firm rock is laid bare, striae are seen upon it ! If glaciers 

 produced them, the glaciers must have occupied the valleys 

 of the Ochil and Pentland hills, and their bearing should 

 have been in the direction of these valleys, that is, south and 

 north. In point of fact, however, the bearing of the striae is 

 invariably east and west, and I have found them in one in- 

 stance actually running across a valley in the Pentlands. 

 Now, if we adopt the iceberg hypothesis, the phenomena 

 may be explained. When the sea stood, as it certainly once 

 did stand, a thousand feet or more above its present level, a 

 current would set eastward through the gulf then occupying 

 the low lands of which the estuaries of the Forth and Clyde 

 form the extremities. If we then suppose numerous icebergs 

 detached from the mountains of the west, and armed at the 

 bottom with stones, to float through this gulf, we can easily 

 understand that such bodies would polish or scratch the 

 rocks with which they came into contact ; further, that the 

 scratches would point in the direction in which the current 

 flowed, that is, eastward ; and as the motion of these icebergs, 



