APPENDIX A. l6l 



izontal ledges of the Lake Superior sandstone, in plainly visible 

 inconformable superposition on the uplifted edges of the slate rock. 

 Mr. Hurley, of Marquette, during last summer, opened a quarry 

 in this sand rock, and, as I am informed, found a ven,* good mar- 

 ketable stone equal to the Marquette brown stones. In the slate 

 exposures along the shore, we can see the strata frequently flexured 

 in a series of synclinal and anticlinal axes. The slate is in shatter- 

 ed condition, with cleavage planes intersecting the lines of stratifi- 

 cation at various angles ; its color is a light green or bright red, or 

 variegated. Hard and soft seams frequently alternate ; it is not 

 durable, nor does it split regularly, and can not therefore be used 

 as a roofing slate. At intervals, belts of a metamorphic rock, inter- 

 mediate in structure between a very compact glassy sandstone and 

 a Diorite, are intercalated between the slate layers. Some of these 

 belts are massive, like an intrusive volcanic rock, while others are 

 distinctly bedded and alternate with thinner seams of slate rock. 

 In places the tough, hard rock is rotten on the surface, and, when 

 such is the case, lumps can be taken and crushed into sand by a 

 mere pressure of the hand. 



The thickness of the shale rock in the exposure can not well be 

 estimated, as the strata repeat themselves several times on account 

 of their synclinal and anticlinal position ; but the rock is so much 

 alike in its totality, that an identification of the corresponding 

 strata on opposite sides of the axes of elevation can rarely be 

 made. In one of the synclinal crevices, I noticed an interesting 

 case of the filling up of the gap by horizontal layers of sandstone. 

 The bed of a creek which descends in a series of rapids, from the 

 northern slope of the Huron mountains to the head of L'Anse 

 Bay, presents a splendid section through at least ICXDO feet of 

 slate rock, with an approximate strike from northwest to south- 

 east, and a southern dip. This slate is of darker color and more 

 compact than the slate in the shore exposure, but is not at all 

 suited for roofing purposes. Contact of the slates with the granitic 

 rocks cropping out at the summit of this slope is not seen. Deep 

 drift masses, mixed with slate and granitic blocks, occupy a large 

 space between them. 



The slate rock suitable for roofing is found on the northwest 

 side of the Huron mountain range, in the vicinity of Huron Bay. 

 A fine road 15 miles in length has been made from L'Anse to 

 II 



