Geological Changes in the South of Scotland. 35 



the driving blast : on this supposition, the lashing of the 

 stormy waves together with the tidal action would certainly 

 in the course of time excavate a beach of less or greater mag- 

 nitude, according to the nature of the ground and its exposed 

 situation. But a close observer must reject that idea also, as 

 he will at once perceive that powerful currents must have swept 

 along, which is incontestably proved by the vast mass of ruins 

 so universally thrown to the east, enough in many cases to 

 afford material for a city. During our first examination of the 

 terraces, we were frequently puzzled by a singular appear- 

 ance they presented.' In almost every case, whether those 

 shelves were of greater or less extent, their extremities were 

 always observed to be rounded over, especially at their west- 

 ern end, and whenever the ground trended back, they still 

 kept a nearly straight course by bending down hill for some 

 distance. From this mysterious form and other inexplicable 

 appearances, we were, after repeated examinations, at last 

 obliged to abandon the idea of water alone having run out those 

 terraces. Early in the spring of 1841, as the writer was 

 wandering upon one of the finest scenes of the kind in the 

 district, it then occurred to him, that probably floating ice- 

 bergs was the cause of the extraordinary denudation around 

 him ; gradually the mystery seemed to vanish, and shortly 

 after he became so thoroughly convinced of the truth of the 

 theory, as to be surprised at his obtuseness of intellect in not 

 having caught the idea earlier, so plainly did that place seem 

 to tell its own tale. The scene alluded to is upon a saddle- 

 backed ridge or spur of Williamlaw hill, which stretches its 

 denuded spine and terraced front boldly south into the Gala 

 valley. The grooving over the summit of that ridge is the most 

 remarkable of any we have seen ; at one place the rock is worn 

 down about 10 feet below the adjoining strata, and 36 feet 

 broad. The rock everywhere bears strong marks of attrition. 

 The grooving runs in the direction of the tilted strata, which is 

 nearly east and west. The west side descends at an angle of 

 26 degrees, and the grooving continues downwards for about 

 76 feet, gradually diminishing in depth as it descends. The 

 east side has much the same appearance, but is nothing like so 

 strongly marked. Some adjoining ledges of great hardness 

 project several feet high, completely rounded over. The rock 

 is greywacke, the strata nearly vertical, and harder than many 

 kinds of granite*. That place is by no means a solitary in- 



* In the face of this evidence, there are not wanting some who assert 

 that the rounded form of those prominent blocks has been occasioned by 

 weathering, " for (they say) had the place been subjected to the powerful 

 denudation of floating icebergs, the surface would have been as smooth as a 



D2 



