BRITISH POSTGLACIAL &> RECENT DEPOSITS. 413 



during the Glacial Period proper. I have in a former chapter 

 described the closing scenes of the true Ice Age, and shown that 

 the mer de glace melted away from the low grounds, breaking up 

 as it were into a series of large local glaciers, which gradually 

 shrank up the valleys. The morainic dSbris and perched 

 blocks dropped by these glaciers can still be followed along the 

 slopes of the valleys in Peeblesshire, but no well-defined morainic 

 mounds now occupy the valley-bottoms at low levels. If such 

 ever did exist, they have all been swept away by the denuding 

 action of torrents, streams, and rivers. It is only when we 

 reach the very heads of the upper valleys, as in those of the 

 Manor, the Talla, the Fruid, and other streams, that we encounter 

 well-marked conspicuous mounds of morainic matter. 



Similar examples of isolated and well-preserved moraines 

 occur in the Cheviots, and they are especially numerous in the 

 mountain-valleys of South Ayrshire, Kirkcudbright, and Wigton. 

 In the Northern Highlands there is hardly a high valley in 

 which they may not be seen, and the distinction between the 

 shapely cones and ridges of the recent moraines and the denuded 

 heaps of morainic dSbris and great banks of gravel which marked 

 the dissolution of the older glaciers, is always more or less well 

 defined. As an excellent example, and one of easy access, I may 

 point to Glen Turret, in the neighbourhood of Crieff, at the head 

 of which morainic cones and ridges are abundant and beauti- 

 fully preserved. Farther down the valley, below the lake, the 

 only relics of the older glaciation are weathered roches moutonnees, 

 scattered angular boulders, degraded morainic mounds, boulder- 

 clay, and diluvial sand and gravel. 



It has been held by some geologists that the reason why 

 moraines are so well preserved and prominent in the upper 

 reaches of many mountain-valleys, may be due to the glaciers of 

 the Ice Age having made a long pause in those localities before 

 they finally disappeared. They suppose that the great glaciers 

 melted slowly but continuously away from the lower reaches of 

 the valleys, so as never to allow of the accumulation of distinct 

 frontal moraines until they were just about to vanish for ever. 



