140 REPOKT OF THE 



(e) Brown, bituminous limestone, 75 feet: Monroe, Presque 



Isle and Emmet counties. 

 (d) Arenaceous limestone, 4 feet: Monroe county, Crawford's 



quarry. 



(c) Oolitic limestone, 25 feet: Bedford, Raisinville, &c, Mon~ 



roe county; Mackinac. 



(b) Brecciated limestone, 250 feet: Stony Pt., Pt. aux Peaux, 



Mackinac and vicinity. 

 (a) Conglomerate, cherty, and sometimes agatiferous, 3 feet: 

 Mackinac, Sitting Rabbit. 



II. UPPER SILURIAN SYSTEM. 



6. Onondaga Salt Group, 3 1 feet: 



(d) Chocolate colored limestone, 10 feet: Monroe county, 



Mackinac. 



(c) Calcareous clay, 3 feet: Bois Blanc. 



(6) Fine, ash colored, argillaceous limestone, with acicular 

 crystals, 14 feet: Monroe county, at Montgomery's 

 quarry, Ida; Otter Creek and Plumb Creek quarries; 

 Mackinac; Round and Bois Blanc islands. 



(a) Variegated, gypseous marls, with imbedded masses of 



gypsum, 10 feet: St. Martin's islands; Little Pt. au 

 Chene. 



5. Niagara Group, 91 feet: 



(g) Thin-bedded brown limestone, 6 feet: south side Drum- 



mond's Island. 

 (/) White, massive, crystalline limestone, 20 feet: south and 



southeast sides Drummond's Island; coast west of 



Detour. 



(e) Rough, vesicular limestone, 6 feet: east end of Drum- 



mond's Island. 



(d) Limestone, in thin broken layers, 8 feet: Ibid. 



(c) Limestone, geodiferous, rough, crystalline, 45 feet: Ibid. 



(b) Limestone, hard, gray, crystalline, 7 feet: Ibid, 

 (a) Arenaceous limestone, 5 feet: Ibid. 



4. Clinton Group, 51 feet: 



(c) Argillo-calcareous limestone, very light colored, and 



evenly bedded, 14 ft.: E. and W. ends of Drummond's 



Island. 

 (6) Argillo-calcareous limestone, dark, containing geocles and 



gashes, 3 feet: N. ±U. side Drummqnd's Island, 

 (a) ^Alternations of argillaceous, bituminous and calcareous 



limestones. 31 feet: Ibid. 



