4 1 6 PREHISTORIC E UR OPE. 



been deflected by masses of rock which, falling in late glacial 

 and early postglacial times, bad choked up the paths followed 

 by the ice of the true Ice Age. The presence of such a " berg- 

 fall" has even been adduced as proof that the glaciers of the 

 Ice Age had little power to scoop and erode, seeing that the 

 fallen rock-masses have not only not been removed by the local 

 glaciers, but have even sufficed to control the direction in which 

 these latter flowed. Thus a writer in Nature 1 has called 

 attention to the large "bergfall" of sandstone which cumbers 

 the bottom of Glen Beansdale at Loch Maree, and which has 

 forced the stream out of its old course, and compelled it to dig 

 for itself a new passage between the bergfall and the opposite 

 slopes of the valley. This newer course, after having been 

 formed by the stream, was at a later date traversed by a local 

 glacier which necessarily flowed in the same direction, the old 

 stream-course being effectually blocked up by the great fall of 

 sandstone from the cliffs at the base of which the water formerly 

 ran down to Loch Maree. The writer concludes that this bergfall 

 is of preglacial age ; and from the fact that it looks so fresh tbat 

 it " might have fallen within the memory of man, instead of at 

 a date which must be reckoned by thousands if not millions of 

 years," he infers that the modern school of geologists is pro- 

 bably in error in ascribing so much potency to the agents of 

 "subaerial waste," seeing that these have apparently made no 

 impression upon the " bergfall," while the stream itself has only 

 been able to cut a narrow trench in the bottom of the glen since 

 the glacier melted away. But this large bergfall is not of 

 preglacial but of postglacial age. During the last glacial 

 epoch all the glens of that region were filled with ice, the 

 surface of which rose to a height of certainly not less than 3000 

 feet above what is now the sea-level. After those great glaciers 

 had disappeared, and the streams and rivers were once more 

 permitted to carry on their work, the stream of Glen Beansdale 

 worked its way down through the glaciated rocky floor of the 

 glen, and cumbered this with shingle and boulders. Then the 



1 Nature, vol. xx. p. 504. 



