IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 



433 



the belt of green schist already described. At this locality these 

 Cambrian schists seem to merge into the eastern schists without 

 any well-marked boundary line. 



Fig. 23. — Diagram of Cambrian Strata on Coinne-mlieall, illus- 

 trating differential cleavage, schistosify, and formation of fjeg- 

 matite in Gamhrian Grits and Shales above Ben-More Thrust- 

 plane as seen in Goinne-mheaell and Biver Oglcel. (Area shown 

 about 12 yards square.) 



d 



a. Coarse Grits or Arkose, 



b. Finer G-rits or Ai'kose. 



c. Shales. 



cl. Pegmatites. 

 The arrow shows the direction of movement. 



3. lletaynorjyhism of the Silurian Strata. 



The various members of the Silurian series underlying the Glencoul 

 Thrust-plane show little alteration, even where they have been piled 

 on each other by minor and major thrusts. The " Pucoid-beds " are oc- 

 casionally cleaved, the planes being determined by the adjacent thrusts. 

 Not till we pass eastwards to the horizon of the materials above the 

 Ben-More Thrust-plane is much change observable. The various 

 powerful thrusts above this horizon, repeating wedges of the Archaean 

 platform with various members of the Silurian series, produce marked 

 changes in the latter. Both zones of the quartzite have been 

 attenuated by the elongation or dragging-out of their constituent 

 mineral particles. In the case of the false-bedded grits, the small 

 pebbles of quartz and felspar have been drawn out to a length of 

 three inches near Loch Strath nan Asinteach. The felspar pebbles 

 are often cracked in the direction of the movement and the fissures 

 are filled with secondary quartz. Again, in the " pipe-rock,"' the 

 quartz-grains have been elongated and the vertical " pipes " or 

 Annelide-tubes have been bent over, flattened, and drawn out into 

 ribands parallel with the direction of movement. Along the 



2q2 



