76 LOWER PENINSULA. 



same horizon with the grindstones of Huron City are near the sur- 

 face along the shore Hne. The outcrops are insignificant compared 

 with the stretch of sand and graved beach interrupting them, but 

 it rarely requires the removal of very deep drift masses in order 

 to uncover the rock beds. 



At Port Hope, the grindstones crop out in the lake bed close to 

 the docks. More extensi\^e denudations are to be seen one mile 

 and a half north of the village, at the shore ; the land behind it rises 

 in several terraces formed of coarse boulder drift with metamorphic 

 and crystalline blocks and of Niagara and Helderberg or Hamilton 

 limestones, besides a large proportion of fragments from the under- 

 lying sand rock, some of which are rich in the shells usually found 

 in the Marshall and Battle Creek sandstones. The boring of a salt 

 well at Port Hope, to a depth of 787 feet, is recorded as follows : 



Drift 16 ft. 



Greenish micaceous sandstone 6 *' 



Blue arenaceous shale, with occasional seams of 



sand rock 510 " 



Very hard rock (not more particularly specified). . i " 



Dark blue shales 1 54 " 



Arenaceous shales 29 " 



Coarse, whitish sandstone, saturated with strong 



salt brine 71 " 



Further south, in the creek near Sand Beach, greenish and bluish 

 micaceous sand-rock ledges interstratified with shales are exposed 

 in seams filled with a species of Chonetes. The same beds, with 

 Chonetes and impressions of Goniatites, are well exposed at Rock 

 Falls, the ripple-marked surface of the ledges in the latter place 

 being covered with Caudagalli fucoids in relief, as well as other 

 singularly-shaped prominences of organic origin. 



At White Rock, south of the village, the arenaceous shale beds 

 below the horizon of the grindstones ascend in steep bluffs of 25 

 feet elevation from the lake bed, for the distance of about a mile. 

 Indistinct casts of fossils, amongst which Goniatites is recognizable, 

 are found on the surface of the arenaceous flags ; this is the 

 last rock exposure on the shore of Lake Huron, which washes 

 upon a drift beach for the remainder of the distance down to 



