1868.] MACFARLANE — GEOLOGY OF LAKE SUPERIOR. 247 



the Laurentian and Hurooian rocks. They are regularly inter- 

 stratified with each other, and even among the melaphyres and 

 porphyrites distinct bedding is observable. They do not 

 seem to have been disturbed to such a degree as to occasion the 

 formation of anticlinal and synclinal folds, and in each of the 

 principal areas of distribution a tolerably persistent strike and dip 

 can be observed. 



The general strike of the rocks of the Mamainse group is N. 

 20 2 to 50° W., and the dip 20° to 45° south-westward. They 

 are beautifully exposed along the west coast of Mamainse. and 

 the highest strata of the group form the south-west extremity of 

 the cape. The lower part of the group consists of granular and 

 delessitic melaphyres, polygenous conglomerates and sandstone. Iu 

 the upper part compact melaphyres and porphyritic conglomerates 

 predominate. The total thickness of the group, according to an 

 approximative measurement, is 16,208 feet, of which the conglo- 

 merates occupy 2,138 feet. The succession of the beds along the 

 coast is quite regular ; but on attempting to follow them inland, 

 they are found to thin out and disappear, while others take the ir 

 places. This is especially the case with the conglomerates. Were 

 the beds continuous throughout, the section above given ought to 

 be repeated on the south coast, and round to Anse-aux-Crepes. 

 But there, although some of the melaphyre beds have the same 

 strike and dip as on the west coast, there is not the same regularity 

 nor the same plentiful development of conglomerates. Theiv 

 are moreover evidences of great disturbances and of a conflict 

 between the rock of some of the igneous beds and a sandstone, 

 which here appears in highly contorted and sometimes vertical 

 strata. On coming round the south coast of Mamainse, from 

 Anse-aux-Crepes, strata of sandstone are observed very much 

 disturbed and dipping inland. As near as it can be ascertained, 

 their strike is about N. 85° W., dip 25° to 40° northward. The 

 sandstone is red coloured, and contains streaks and spots of a 

 cream coloured felspathic substance, which also forms bands crossing 

 the stratification. Many thin cracks filled with calcspar also 

 traverse the beds. The same sandstone continues for about a 

 hundred and forty yards further to the west, becoming still more 

 disturbed, and containing between its layers the felspathic 

 substance. The strike, where the beds are at all regular, is N. 10° 

 W.j and dip 52° eastward. Further west it changes to N. 52° 

 E., with dip vertical, and in places 75° S. W. Here the sandstone 



