part 4] THE SCHISTS OF THE SCHICHALLION DISTRICT. 44o 



of material originally picked up from the still soft black mud 

 below : this continues to the west of Pitlochry. Farther south- 

 west the erosion went deeper, and small fragments of coherent 

 mud were picked up and are now seen enclosed in the Quartzite. 

 Still farther south-west these fragments are at times as large as 

 the palm of a man's hand. That the Quartzite is above the true 

 Graphite- Schist is thus clear. 



Starting from the base and crossing the Quartzite, we reach the 

 top, which is fine-grained and white. It is one of the most easily 

 recognized horizons in the Highland rocks. It is perfectly seen 

 in the coast-section at Portsoy, and the speaker had followed it 

 for over 100 miles in the interior of the Central Highlands. 



The area selected by the Author was not a good one for dealing 

 with the succession, as the presence .of the Boulder Bed at once 

 showed that there was a non-sequence : that is, part of the series 

 is always absent when this bed is present. 



The speaker then referred to the succession described by him in 

 the area of (lien Clunie. 1 He had shown that, going southwards, 

 one notes a comparatively sudden hiatus. The Limestone is seen 

 to rest upon a remnant of the Parallel Banded Series, and is 

 occasionally quite close to the white edge of the Quartzite. The 

 erosion is the same, whether the Boulder Bed be present or absent. 

 A photograph of the base of the Limestone lying in an eroded 

 hollow in the Moine Gneiss is published in the paper already cited. 3 

 The approach to and recession from the edge of the Quartzite 

 by the Blair Athol Limestone occurs repeatedly over a large area, 

 and the published evidence shows that the Blair Athol Limestone 

 is above the dark Schist and Little Limestone, which are often 

 cut out by it. The Limestone is also above the Boulder Bed. 



The speaker adduced further detailed evidence bearing on these 

 points from Glen Tilt and' Glen Elg, which all went to prove the 

 Lewisian age of the Moine Gneisses. With regard to the rocks 

 between the true Graphite-Schist and the Southern Highland 

 Border, the superposition of the Quartzite on the Schist shows 

 the succession to be a descending one, and the rocks near the 

 Border are the lowest. This is clearly proved by the fact that 

 a great group of rocks below anj'thing ever occurring along this 

 Border are brought up by a big fault, and cover a Avide area 

 stretching from the North Esk to Aberdeen, etc. These rocks, 

 like the others, are seen to increase in crystallization as one proceeds 

 north-westwards from the Highland Border ; but the increase is 

 much more rapid in the case of the rocks brought up by the fault. 

 Mr. J. F. N. Green said that he was particularly interested in 

 the nordmarkite Boulder Bed. In Islay this had been attributed 

 to ice on good grounds by Thomson half a century ago. In that 

 island, where the rocks were virtually unaltered and excellent 

 '•oast-sections were available, it was obvious that the bouldery beds 



1 Q. J. G..S. vol. lx (1904) pp. 423-27. 



2 Ibid. p. 430. 



