246 NERBTJDDA DISTRICT. 



identified with the different beds of the schist series, and the true breccia 



character of the rock is then well seen. 



Examined on the large scale, this breccia is found always to occur in 



lines, like the outcrop of a bed. But in places 

 Mode of occurrence. 



where the schists and gneiss of the metamorphic 



series are well exposed, and where at the same time the breccia lines can 

 be clearly traced, the latter are found not to coincide with, or to lie 

 parallel to the strike of the former. Both have (roughly) an east and 

 west direction, but the line of breccia is sometimes seen to cut ob- 

 liquely across the outcrop of several varieties of the schists succes- 

 sively. 



Thus it would appear that these lines of breccia mark the direction 



in which some disturbing force has crushed and 

 Conclusion suggested. 



fractured the rocks, so as to iorm the mass 01 



fragments, which recemented together by a quartz matrix, go to form 



the breccia. 



It has been already noticed, that generally, the enclosed fragments of 



•^ t*-u ^ the breccia are siliceous, and very often quartz, 

 Agrees with htholo- ' •> * ' 



gical character. an( j t } ie preponderance of this ingredient may be 



accounted for (on the above hypothesis of the breccia being a fault-rock) 

 by the fact that the fragments are principally derived from the hardest 

 bands of the schists, and are those which would naturally resist best the 

 effects of such mechanical violence, as we suppose to have been the 

 cause of the breccia. 



It has also been stated that fragments of other members of the schist 

 group often occur. These are, it is true, not often capable of being 

 identified with the different varieties of the schists, and referred to this, 

 or to that bed, but as far as such identification is possible, they are always 

 referrible to those beds in the immediate neighbourhood : and no case 

 has been known of a recognizable fragment which belonged to a rock 

 not seen close by. In one case the breccia, both matrix and fragments, 



