184 



THE CANADIAN NATURALIST. 



[May 



place, a faint parallel structure is observable, the strike of which 

 is N. 50° to 60° W. Both the hornblendic fragments and 

 the gneissoid granite are cut by veins of newer granite. On the 

 south-east shore of Goulais Bay, a beautiful group of syenitic 

 rocks is exposed, the mutual relations of which are similar to those 

 above described. Fragments of hornblende rock or schist, varying 

 from half-an-inch to three feet in diameter, are enclosed in a 

 coarse-grained syenitic granite, in which, occasionally, a rough 

 parallelism of the hornblende individuals is observable, the direction 

 of which is N. 57 a E., and coincides with that of the longer axes 

 of the hornblendic fragments. The specific gravity of the horn- 

 blendic rock is 2-94 to 3-06, and of the enclosing oranite 2-74. 

 Both are intersected by a coarse-grained granite, having a specific 

 gravity of 2-61 only, and containing little or no hornblende or 

 mica. The appearance here described are represented by Fig. 4. 



Pig! 4. 



a, Hornblende schist, b, Syenitic gneiss-granite, c, Coarse-grained granite 

 The mutual relations of these brecciated and intrusive 

 rocks in eight different localities, some of them upwards of one 

 hundred miles apart, have here been described, and it will be 

 observed that, in every one of the instances mentioned, the oldest 

 rock is the most basic in constitution, and this appears to be the 

 case, without regard to the mineralogical composition or structure 

 of the rocks associated together as above described. It matters 

 not whether the older rocks be brecciated or entire, hornblendic or 

 micaceous, granular, schistose or porphyritic, it is always most 

 deficient in silica. It appears, further, that the newer the rock 



