30 Reviews — Geology of Ben Nevis. 



II. — The Geology of Ben Nevis and Glen Coe (Explanation of 

 Sheet 53). Memoirs of the Geological Survey, Scotland. By 

 E. B. Bailey, M.A., and H. B. Maufe, M.A. ; with contributions 

 by C. T. Clough, J. S. Grant Wilson, G. W. Geabham, M.A., 

 H. Kxnaston, B.A., and W. B. Weight, B.A. pp. 247, with 

 12 plates. 1916. Price 7s. 6d. 



rnHIS memoir describes the geology of the region that contains the 

 JL highest mountain and perhaps the wildest and most rugged 

 country in Great Britain. All phases of its geology are replete with 

 interest. 



The area is a greatly dissected part of the main Highland plateau, 

 with a summit level of about 3,000 feet. Ben Nevis and other high 

 peaks rising above this level are regarded as features dating from an 

 earlier geographical cycle. Loch Linnhe, lying in a north-easterly 

 direction along the shatter-belt of the Great Glen, divides the 

 area into two unequal parts. Another system of valleys runs 

 W.N.W.-E.S.E. ; and these remarkable 'through' valleys, cut 

 athwart the grain of the country, are consequent upon the pre-glacial 

 uplift of the Highland plateau. Glacial erosion is believed to have 

 cut off spurs and thus widened the valleys. In some cases it is 

 responsible for hanging valleys, although general deepening of valleys 

 by ice action is considered improbable. A large part in breaking up 

 the ' through' valleys into segments is attributed to the formation of 

 pre-glacial delta-watersheds or corroms. While accepting many of 

 Professor J. W. Gregory's views as to the origin of fiords, the authors 

 are not inclined to attribute so much potency as he does to earth- 

 movements (gaping faults and joints) in the development of the 

 typical West Highland fiords. 



The subject of prime interest in this memoir, however, is the structure 

 and succession of the Highland Schists. These rocks form the basement 

 of the whole district, but are partly covered by extensive outpourings 

 of Old Bed Sandstone lavas (Glen Coe and Ben Nevis), and are 

 intruded by great masses of plutonic rocks, principally granite (Ben 

 Cruachan, Ballachulish, Ben Nevis). The Highland rocks consist 

 of alternations of phyllite, mica-schist, and quartzite, with thin 

 horizons of limestone which form good datum-lines for the inter- 

 pretation of the structure. The folding of the rocks is very complex. 

 Mr. E. B. Bailey has developed the view that the rocks are arranged 

 in a number of great recumbent folds, which are frequently ruptured 

 along fold-faults or slides. In certain cases the major folds have 

 been bent into later secondary folds, and have been dislocated by 

 ordinary faults. In consequence of the extraordinary inversion and 

 repetition the beds have suffered, theoi'iginal stratigraphical sequence 

 is doubtful, and it is not known which is the top or bottom of the 

 list of formations. As usual, in the interpi'etation of regions of 

 extreme complex^ such as this, differences of opinion arise; and in 

 regard to the Kinlochleven district Mr. Carruthers holds views at 

 variance with those of Mr. Bailey. The chief difficulty appears to 

 be the number of formations recognized by the respective observers. 

 Mr. Carruthers increases the number of stratigraphical horizons and 



