Vol. 68.] THE GLEN OECHY ANTICLINE. 179 



Discussion. 



Mr. Gr. Baeeow remarked that too much importance seemed to 

 be attached to small variations in the succession. The Geological 

 Survey had published numerous sections of colliery shafts ; in these 

 the coal-seams were seen to continue for great distances, but the 

 succession between the seams was never alike in any two of them. 

 Similarly, along the North-East Yorkshire coast the marine beds of 

 the Lower Oolite were singularly persistent ; but it was impossible 

 to find a similar succession in the intervening beds, even at such 

 small distances as 500 yards apart. 



With regard to the sudden thickening of the quartzite, the 

 speaker had never seen such a phenomenon ; the increase or 

 decrease in thickness of this rock was very slow, and always in 

 definite directions. The apparent increase was due to ' pitch ' or 

 inclination of the axis of folding, which cut the ' surface-section ^ 

 obliquely. From experience in other districts, the speaker was 

 inclined to adopt a different interpretation of the outcrops shown 

 on the map, which formed a very small portion of the lines shown 

 in the diagram. 



Mr. E. H. Cunningham-Ceaig asked what relations the structures 

 described by the Authors bore to the main folding of the country, 

 and whether the anticline was earlier or later than the main folding. 

 He could not entirely accept their reading of the succession, and felt 

 a doubt as to the conclusions that the Authors had put so clearly 

 before the Society. 



Mr. E. B. Bailey, replying for the Authors, stated that the Glen 

 Orchy Anticline was regarded as, in all probability, a later structure 

 superinduced upon the recumbent folds of the neighbourhood. The 

 fan-structure of Ben Lawers (Perthshire) may also eventually prove 

 to be a comparatively late development, Mr. Barrow's suggestion 

 that the limestone which had been traced along the front of the 

 Beinn Doirean range did not continue regularly underground for 

 any considerable distance was negatived by the very evident relation 

 between the outcrop of the limestone and the surface-irregularities 

 of this region. In fact, although it might be admitted that 

 certain of the more speculative conclusions arrived at were still 

 sub jiidice, it was confidently claimed that the local geometrical 

 relations of the various rock-masses were correctly represented in 

 the maps and sections accompanying the paper. 



