86 



situations, that they could not have been brought together by exist- 

 ing river action, being much above the level of the streams which 

 now traverse the valleys. They are most probably referable to gla- 

 cier moraines of two classes the lateral and terminal formed by 

 masses of rock descending from the highest peaks, and thrown to 

 either side by the movement of the ice, or deposited at the extremity 

 of the glacier when the ice melted. The former have been much 

 modified by torrents entering from the sides, after the glaciers dis- 

 appeared, and now present but detached mounds. In some glens, 

 however, as Sannox, terraces yet remain complete, but not of great 

 extent. The terminal moraines are better marked, fine examples 

 being visible at the mouths of Glen lorsa, Glen Catacol, Glen 

 Rosa, and others. The remarkable terraces at the opening of Glen 

 Catacol skirt the valley on the south-west, at a height much exceed- 

 ing any level the stream could now reach by the joint effects of 

 floods and high tides, and indeed surpassing that which it could ever 

 have attained even when the sea covered the present maritime belt 

 or terrace. We are therefore inclined to regard these mounds and 

 terraces as terminal moraines, modified in their outlines by floods, 

 tides, and ordinary river action. 



Still more remarkable are the lofty terraces at the mouth of the 

 river lorsa ; they are far more striking, indeed, than anything of the 

 kind in Arran. They consist throughout of transported materials, 

 some of the rocky masses being very large ; the sides are steep and 

 the summits usually flat ; and the height of the highest is sixty or 

 seventy feet above the river, and at least thirty above the ancient sea 

 level just alluded to. Speaking of these (lorsa and other such 

 mounds) in reference to river action, MacCulloch remarks : " The 

 origin of such alluvia is very obscure a few may have been depo- 

 sited in particular situations by the same waters which are now 

 removing what they formerly laid down ; while in other cases it is 

 impossible to assign any mode of action by which this double and 



opposite effect could have taken place from one agent 



The quantity and quality of the materials, their extremely rounded 

 forms, the nature and permanence of the hills above, and the want 

 of a regular gradation of size in the stones from the bottom upwards, 

 seem to show that other causes [than river action] of a transient, 

 and probably of a diluvian nature, have in distant times generated 

 those deposits, which have been subsequently acted on by the stream 

 concentrated on the bottom of the glen by the form of the ground." 

 (Western Isles, ii., 335, 1819.) The difficulties of these cases had 

 thus presented themselves to the mind of this distinguished geologist, 



