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EECENT WORK OF THE GEOLOGICAL SURVEY 



schist. So characteristic is this feature that few of the dykes do not 

 display the marginal strips of schist. A further stage of change is 

 met with when a broad dyke is traversed by several lines of 

 shearing, in which case lenticular or eye-shaped masses of diorite are 

 formed, round which curve in wavy lines beautiful bands of horn- 

 blende-schist (Canisp deer-forest). 



Fig. 2. — Diagram Sketch, showing Formation of ' Eijes ' of Diorite 

 in Hornhlende-sehist, from shearing of Dolerite-dyke intrusive in 

 Gneiss. 



The gneiss has been modified by a secondary foliation parallel to the walls of 

 the dyke. 



The arrow indicates the direction of movement. 

 Area represented, about 600 square yards. 



Pinally the ^ eyes ' of diorite disappear, and the whole of the 

 original dyke is converted into a zone of hornblende-schist. This 

 extreme alteration is almost invariably accompanied by a complete 

 reconstruction of the surrounding gneiss to be described presently. 

 The bands of hornblende-schist consist mainly of secondary felspar 

 and hornblende with a small quantity of mica, and can be split into 

 thin laminae from a quarter to half an inch thick, the direction of 

 foliation being parallel with the lines of movement, viz. W.N.W. or 

 N.W. An examination of the foliation- surfaces shows that the 



