STATE GEOLOGIST. 93 



effloresce with common salt in dry weather and furnish a favor- 

 ite " lick " for cattle. 



The roof of McReynoIds & Stewart's quarry dips N. W., 

 about one foot in twenty. The dip in Hovey's quarry is very 

 slight, N. 10° E. 



By connecting these observations with those made in boring 

 the State salt well on the opposite side of the river, we arrive 

 at an approximation to the whole thickness of the group, thus: 



Section measured at McR. & S.'s quarry, 58 ft. 



From bottom of quarry to alluvial flat by river's edge, . . 50 ft. 



Allowance for dip of formation, 15 ft. 



Thickness of alluvium at salt well, 40 ft. 



Residual thickness of salt strata in well, 21 ft. 



Total, 184 ft 



This series of rocks is penetrated in all the borings for salt,. 

 at Grand Rapids and that vicinity. It is found passing up- 

 wards through a few feet of calcareous sandstone, into the well 

 characterized carboniferous limestone. The thickness of the 

 group in Lyon's salt well, was found to be 111 ft.; in Butter- 

 worth's, 157 ft.; in Scribner's, 153 ft ; in the Indian Creek well, 

 (Ball's) 133 ft.; in Windsor's, 184 ft.; and it was penetrated 

 100 feet in Powers & Martin's well. In Jackson county it is 

 found to be 49 feet thick. 



In Kent county, the Michigan Salt Group is undoubtedly the 

 source of the supply of brine, though the strength remains un- 

 diminished, as a matter of necessity, while the boring is con- 

 tinued in the underlying Napoleon sandstone, until a stream of" 

 fresh water is struck, which, rising up, materially dilutes the 

 brine 



On the opposite side of the State, this group outcrops on the= 

 shore of Tawas Bay (Ottawa Bay), on the west side of Sagi- 

 naw Bay. Two miles beyond White Stone Pt., Bay county, T. 

 20 N.', 7 E., is a bluff about 19 feet high, known as "Plaster 

 Bluff," at which the following section was observed: 



