Vol. 60.] OF THE EAST-CENTRAL HIGHLANDS. 427 



movements anterior to the main crystallization of the Highland rocks. ; 

 Associated with the flinty bands are much paler, almost white, 

 layers. The dominant constituents of these are white pyroxene and 

 calcite. Other pale bands rich in epidote occur. All these phases 

 may be found in the Calc-Flintas associated with the Main Lime- 

 stone at the corrie opposite Newbiggin. They also show another 

 feature of the rock : here and there special bands occur, differing in 

 type from the normal. At this locality, a few bands have an almost 

 micaceous aspect, owing to the presence of a great number of small 

 parallel crystals, determined by Dr. Flett to be pale hornblende. 

 The proportion of the more flinty material is small here, but the 

 parallel banding is well shown. A very small infold of the pyroxene- 

 bands is associated with the limestone in the bed of the Clunie at the 

 southern end of Auchyndrine (Braemar). 



(/) Further Evidence of the Succession. 



It has already been shown that the Quartzite is succeeded by the 

 Parallel-Banded Hocks; the best locality for ascertaining the nature 

 and succession of the zones above the latter occurs in Glen Callater, 

 at the bend of the stream above the quarry in the flaggy hornfels, 

 above the bridge at Auchallater. At this bend, when the water is 

 low, we see first the Little Limestone (tremolite-rock, S091) : next 

 this comes the Twin-Chlorite Hock (8092) of a characteristic 

 dead-black, due to the presence of graphite ; while next this again 

 come the various portions of the Felspar-Rock (8094, etc.), often 

 known as the Felspar-Hornfels 2 of Glen Callater. At the southern 

 edge of the quarry (see map, fig. 4, p. 422), in the flaggy hornfels, 

 we see again the Felspar-Rock, with its glistening crystals of felspar 

 rendered dark by the presence of the dark dust, which serves to fix 

 the horizon of the rocks within the quarry. These arc characterized 

 by a flaggy habit, the splitting-faces being coated with bronzy mica 

 and, at times, with small spots. The different bands vary in colour 

 and compactness. The darkest have a somewhat flinty cross-fracture, 

 and contain a great quantity of fresh andalusite showing the typical 

 pink pleochroism. Except on the splitting-face the amount of biotite 

 present is small, but there is a considerable quantity of shimmer- 

 aggregate material replacing some alumina-silicate. Quartz is sub- 

 ordinate in amount, and a small quantity of felspar is present. The 

 typical dark dust is abundant, and the structure of the rock is 

 essentially that of a hornfels. A band, in which the flinty cross- 



1 The hornfels-like aspect of this rock, traceable over half the breadth of 

 Scotland, is due to the fact that, after induration, it usually escaped crushing 

 owing to the plasticity of limestone at a high temperature (as proved by the 

 experiments of Prof. Adams & Dr. Nicolson). The limestone next the Hintas gave 

 way readily and relieved the latter from the crushing stresses. Many other 

 rocks must have been similarly indurated, but possessing no such yielding 

 margin they have been since crushed. 



2 See §IV, p. 442, at the end of which the bearing of this rock on the absence 

 of metamorphism due to the neighbouring mass of granite is discussed. 



