LOWER HURONIAN AND UNDERLYING GRANITE. 273 



ders appears to be identically the same granite as that on which 

 the conglomerate rests. We find both the white and the red- 

 weathering varieties represented among the pebbles of the con- 

 glomerate, and perhaps also the coarse pegmatite. Figures I and 

 II from a sketch made to scale in thfe field show the appear- 

 ance of the rock on the dip surface, while Fig. Ill, drawn to the 

 same scale, shows the outlines of two medium-sized granite bowl- 

 ders, as seen in cross section on a joint plane. 



V. Contact. 



At the south end of the main exposure, a nearly vertical cross 

 joint plane on the south of which the rocks have been removed, 

 shows the contact for eight or ten feet across the strike. The 

 relations are represented in Fig. IV. 



The conglomerate can be followed by its pebbles with great 

 certainty. The granite below is equally unmistakable. Between 

 the lowest pebble layer of the conglomerate and the undoubted 

 granite, is a zone a few inches wide, that is difficult to assign 

 with certainty to either rock. The contact otherwise is very 

 definite and follows the dip of the conglomerate pebbles. There 

 is no indication that the contact is not simply one of erosion. 

 As the matrix of the conglomerate has been transformed into a 

 crystalline schist as the result of shearing, one may easily sup- 

 pose that the doubtful zone represents either recomposed granitic 

 detritus or the broken up material of both rocks due to move- 

 ment along the contact during the folding. 



At the north end of the main exposure we have another nat- 

 ural section on a cross vertical plane, shown in Fig. VI. Here a 

 large semi-detached mass of granite, which seems to be joined at 

 the east end to the main mass, lies over a portion of the con- 

 glomerate. At its west end it includes a folded fragment of the 

 conglomerate matrix four or five feet long, and two or three feet 

 across, shown at B in the figure. 



The junction between the quartz-schist and the granite is 

 sharp, and the banding of the schist is cut at a small angle by 

 the granite. At the east end of the granite mass, at A, a ver- 



