GENERAL OBSERVATIONS, 377 



Salixa, Saliferovs Epoch. — Brown and gray argillaceous limestones, calcareous clay, 



and variegated gypseous marls, 37 feet. 

 Oriskany, Oriskany Epoch. — Chert}-, sometimes agatiferous conglomerate, 3 feet. 



Devonian. 



Cobnifekous, Corniferous Epoch. — Brecciated limestone, 250 feet; overlaid by oolitic, 

 arenaceous, and bituminous limestones, 104 feet. 



Hamilton, MarceUus (?) Epoch. — Black, bituminous limestone, 15 feet. 



Hamilton Epoch. — Argillaceous limestones, 17 feet; crystalline limestone, 

 •with included lenticular clayey masses, 23 feet; total, 40 feet. Contains * 

 bed of coal, on Little Traverse Bay. 

 Genesee {?) Epoch. — Black, bituminous shale, 20 feet. 

 Chemung, Portage Epoch. — "Huron " shales, 190 feet. 



Carboniferous. 



Subcarbonifebous, Lower. — "Huron" and "Marshall" grit-stones, and reddish, 

 yellowish, and greenish sandstones and conglomerates, 173 feet; "Napoleon 

 sandstone," generally micaceous, with clay beneath, 123 feet; "Michigan 

 Salt-group," carbonaceous and argillaceous shales, magnesian and arena- 

 ceous limestones, and thick beds of gypsum, 184 feet; total, 480 feet. 

 Upper. — Limestones, arenaceous below, 66 feet. 



Caebonifebous, Millstone Grit Section — "Parma" thick-bedded sandstone, in some 

 places conglomerate, 105 feet. 

 Coal-measures. — Bituminous shales and fire-clays, with occasional thin sand- 

 stones and limestones, 123 feet; ''"Woodville " sandstone, 79 feet; total, 

 202 feet. 



4. Iowa Section. 



Lower Silurian. 



Pbimobpial, Potsdam Epoch. — Sandstone, with thin, calcareous layers, £00 feet. 

 Canadian. Calciferous Epoch. — " Lower Magnesian " limestone, 250 feet 



Chazy Epoch. — " St. Peter's Sandstone," 80 feet. 

 Trenton, Trenton Epoch. — "Buff," "Blue," and "Galena" magnesian limestones. 

 with some shaly portions in the lower layers, 450 feet. 

 Cincinnati Epoch. — Siliceous and argillaceous " Maquoketa " shales, mostly 

 bituminous, 80 feet. 



Upper Silurian. 



Niagara, Clinton and Niagara Epochs. — Light yellowish-gray, compact magnesian 

 limestone, with much chert, 350 feet. 



Devonian. 



Hamilton, Hamilton Epoch. — Shales and magnesian limestones, 200 feet. 



Carboniferous. 



Subcabbonifebous. — Consisting of — 1st, " Kinderhook " beds, 175 feet; 2d, "Bur- 

 lington " limestone, 190 feet; 3d, "Keokuk " limestone, with thin beds of 

 shale, 90 feet; 4th, "St. Louis" limestone, commonly brecciated and con- 

 cretionary, in some parts compact, 75 feet; total, 530 feet. 



Carbonifebous. — Lower Coal-measures, 200 feet ; Middle, 200 feet ; Upper, 200 feet. 



