364 



upon this island, as is testified by numerous pits, but tbe fractured sur- 

 face stone only appears to have been removed. These fragmentary 

 blocks seldom exceed a foot diameter, are of a white color, compact, and 

 afford good lime. The island is but little above high water level, and 

 the pits are now flooded. 



Quarries have been opened at the lower end of Grosse Isle. The rock 

 makes its appearance in a slightly elevated ridge, at some distance from 

 the shore. Trenches are opened for quarrying in no place more than 5 

 feet deep. The upper layers are of a few inches thickness, removable 

 in irregular pieces of a size suitable for rough building. One of the 

 trenches exposes a stratum of 3 feet thickness, for the distance of 300 

 feet. The stratum is compact and may be broken out in nearly square 

 masses. 



Sulphate of strontian, in large crystals, is abundant in the upper 

 layers. No fossils were discoverd. 



In section seven, of Monguagon, is a protrusion of the rock in a 

 ridge, occupying a surface of a dozen acres. Quarries have been exten- 

 sively worked, chiefly for lime. The rock is in strata of from 6 to 10 

 inches thickness, of gray color, crystalline, and eminently fossiliferous. 

 The quarries have extended to tl.e depth of 6 feet. The color of the 

 stone deepens into blue, and its hardness increases with the depth. Cal- 

 careous spar is contained in crystals, lining small gendes and fissures. 

 Thin layers of indurated bituminous matter, approaching coal, are con- 

 tained between some of the strata. The largest masses of stone ob- 

 served to be quarried in good condition, were two feet in length by about 

 eighteen inches wide. Whether larger slabs might not be obtained by 

 proper care, I was unable to learn. It is fully equal in beauty to the 

 much admired building material brought from Ohio, but its superior 

 hardness renders the dressing and polish much more expensive. 



From 9,000 to 12,000 bushels of lime are manufactured annually at 

 this quarry. 



Limerock makes its appearance in Brownstown creek, one and a half 

 miles west from Gibraltar, and has been used to a very limited extent 

 for domestic purposes. 



Rock is said to appear at the water's edge, on the lower end of Cele- 

 ron island. 



Limerock forms the rapids in the Huron, at Flat Rock. It appears 



