612 MESSES. CLOTJGH, MATJEE, AND BAILEY ON [Nov. I909, 



intrusions. In a final section we hav added a theoretical dis- 

 cussion of our results. 



Situated between Oban and Fort William, in the midst of the 

 mountainous region of Northern Argyllshire, the district of Glen 

 Coe affords a series of magnificent natural sections. The Pass, 

 even at its summit, barely reaches the 1000-foot contour, while 

 the majority of the hills on either side rise steeply to altitudes of 

 3000 feet and more. Bidean nam Bian, the highest mountain in 

 Argyllshire, attains the elevation of 3766 feet, and the average 

 gradient of its flanks, measured from the valley-floor, amounts 

 to 25°. Individual slopes are, of course, much steeper than this ; 

 the face of Aonach Dubh, above Loch Achtriochtan, for example, 

 is an all but inaccessible cliff, rising 2000 feet at an angle of 55°. 

 In addition to this, the comparatively recent glaciation of the dis- 

 trict has left the rock-surfaces fresh and clean, and the covering of 

 morainic drift is everywhere remarkably light. 



But want of railway connexion, which has only recently been 

 established, and the physical impossibility of dealing with such 

 hills in a limited space of time, have proved obstacles in the way 

 of scientific research, and Glen Coe has never received so much, 

 geological investigation as it deserves. 



Among the older geologists, MacCulloch, 1 Macknight, 2 Boue, 3 

 and Nicol 4 have given brief accounts of their visits to the Glen. 

 They recognized the existence of crystalline schists and gneisses, 

 granite or syenite, dykes of ' felspar-porphyry,' and masses of 

 ' compact felspar ' and ' hornstone,' but the complex relations of 

 these rock-masses were scarcely, if at all, understood. 



In 1874 Prof. Judd included a short description of Glen Coe in 

 his account of the Newer Palaeozoic Volcanoes of the "Western 

 Highlands. 5 He recognized a great series of ' felstone ' lavas, under- 

 lain partly by schists and partly by granite, and remarked on the 

 close similarity in petrological characters between the Glen Coe 

 lavas and those which make up larger areas in Lome and the Ochil 

 and Cheviot Hills. He also called attention again to the multitude 

 of dykes traversing schists, granites, and lavas alike. 



In 1900 Mr. H. Kynaston began work in the district on behalf of 

 the Scottish Geological Survey. He received assistance from Dr. B. 

 N. Peach, who was at that time in charge of the West Highland 

 division, and in 1902 a joint excursion was undertaken by Dr. Peach, 

 Mr. Kynaston, and Mr. Tait, primarily with the object of establishing 

 the age of the Glen Coe volcanic group. This expedition was en- 

 tirely successful, for Mr. Tait obtained remains of two Lower Old 



1 'Observations on the Mountain Cruachan in Argyllshire, with some 

 Bemarks on the Surrounding Country ' Trans. Geol. Soc. vol. iv (1817) p. 132. 



2 ' On the Mineralogy & Local SceDery of certain Districts in the High- 

 lands of Scotland' Mem. Wernerian Nat. Hist. Soc. vol. i (1811) pp. 311-18. 



3 ' Essai geologique sur l'Ecosse ' Paris, n. d. p. 67. 



4 'Guide to the Geology of Scotland' Edinburgh, 1844, pp. 159-61. 

 s Q.uart. Journ. Geol. Soc. vol. xxx (1874) p. 220. 



