32 The Scottish Naturalist. 



rocks rest is a thick mass of Cambrian red sandstone. In the 

 great upthrow, it is this sandstone platform which has there been 

 pushed over the limestones and quartzites. On the west side of 

 Loch Keeshorn, the red sandstones, in their normal unaltered 

 form, rise up into the colossal pyramids of Applecross ; but on the 

 east side, where, at a distance of little more than a mile, they over- 

 lie the limestones, they bear so indurated an aspect that they have 

 naturally been classed with the quartzose members of the Silurian 

 series. Traced eastwards they present increasing evidence of in- 

 tense shearing ; fluxion-structure makes its appearance in them, 

 with a development of mica along the divisional planes, until they 

 pass into frilled micaceous schist, in which, however, the original 

 clastic grains are still recognisable. They finally shade upwards 

 into green schists and fine gneiss which merge into coarse gneiss 

 with pegmatite. The short space within which ordinary red fel- 

 spathic sandstone and arkose acquire the characters of true schists, 

 is of some importance in regard to the change from the unaltered 

 Silurian strata of the Southern Uplands into the metamorphic con- 

 dition of the Highland phyllites, grits, &c. 



Obviously the question of chief importance in connection with 

 the structure now ascertained to characterise the north-west High- 

 lands relates to metamorphism. That there is no longer any evi- 

 deir-j of a regular conformable passage from fossiliferous Silurian 

 quartzites, shales, and limestones, upwards into crystalline schists, 

 which were supposed to be metamorphosed Silurian sediments, 

 must be frankly admitted. But in exchange for this abandoned 

 belief, we are presented with startling new evidence of regional 

 metamorphism on a colossal scale, and are initiated some way 

 into the processes whereby it has been produced. 



From the remarkably constant relation between the dip of the 

 Silurian strata and the inclination of their reversed faults, no mat- 

 ter into what various positions the two structures may have been 

 thrown, it is tolerably clear that these dislocations took place 

 before the strata had been seriously disturbed. The persistent 

 parallelism of the faults and of the prevailing north-easterly strike 

 of the rocks indicates that the faulting and tilting were parts of 

 one continuous process. The same dominant north-easterly strike 

 extends across the whole Highlands, and also over the Silurian 

 tracts of Southern Scotland and of the North of England. There 

 is reason to regard it in all these regions as probably due to one 



