396 EECENT WOEK OF THE GEOLOGICAL STJKVET 



powerful disruption-lines. In the case of the first system of 

 movements, the strike of the gneiss in these contorted belts is 

 W.]N".W. or ^.W. ; in the second system the strike is nearly E. 

 and W. 



6. Coincident with this folding and high inclination of the 

 gneiss there is a modification of the constituent bands ; the folia 

 are attenuated, and there is a partial reconstruction of the rock. In 

 some cases this reconstruction has been so complete that the orienta- 

 tion of the minerals in the gneiss coincides with that of the minerals 

 in the hornblende-schist in the basic dykes. Where this happens, 

 the movements have given rise to a second foliation of the original 

 types of gneiss. 



c. The constituents of the different laminae have undergone a 

 mineralogical change, the original opalescent quartz-granules, 

 besides being elongated, lose much of their opalescent character and 

 become clear and vitreous ; black mica has been abundantly 

 developed out of the original hornblende, and a white hydrous mica 

 out of the original felspar ; the hornblende has recrystallized in 

 the form of needle-shaped crystals of hornblende or actinolite ; and, 

 lastly, there is a plentiful development of secondary felspar. 



d. The high inclination and folding of the gneiss is usually 

 accompanied by crush-lines, forming sometimes coarse breccias full 

 of irregular fragments, sometimes very thin schistose bands several 

 inches in breadth or even less, the foliation being parallel with the 

 sides. Indeed, along the crests of many of these sharp folds new 

 shear-planes occur, indicating complete disruption. 



One of the best examples of the second foliation developed in the 

 original gneisses by these vertical lines of movement occurs in the 

 neighbourhood of Lochinver. It forms a belt from a quarter to half 

 a mile in width, running W.N.W. through the Canisp deer-forest by 

 Torbreck to Loch Eooe and Achmelvich. The strata consist of fine- 

 grained gneiss and schist striking W.I^.W., and inclined at high 

 angles to the S.S.E. Indeed, as a general rule, this second foliation, 

 wherever it occurs throughout the area in connexion luiili the N. W. 

 vertical movements^ dips at high angles in a south-easterly direction. 

 Excellent examples of narrow zones of iewer foliation trending 

 E. and W. are displayed to the north of Kylesku. 



In the case of the flat thrust-planes near Kylestrome, the 

 disruptions in the gneiss are prominently marked, being sometimes 

 filled with a layer of soft, rusty micaceous matter, on either side of 

 which the folia of gneiss are inclined at different angles to the 

 thrust. Occasionally there are repeated overfolds of a thin band in 

 the micaceous layer, though the adjacent gneiss shows no trace of 

 similar contortions. 



In all the cases observed near Kylestrome the crests of the over- 

 folds point S.W. or S.S.W., so that it would appear that the upper 

 layers had moved over the lower ones in this direction. These 

 layers of micaceous material may reach a few feet in thickness, and 

 the plates of mica may be repeatedly folded by renewed movement 

 along the line. The micaceous matter found in these fiat thrust- 



