306 GEOLOGY OP OHIO. 



CLEVELAND SHALES. 



These have the ordinary characteristics of this formation, as described 

 in the reports of the north-eastern counties of the State, differing mate- 

 rially only in two particulars. The deposit is thinner here, varying 

 from fifteen to thirty-two feet at the points where measurements could be 

 obtained. It also contains less carbonaceous matter and more iron, pass- 

 ing into the red shale which gives its name to the Vermillion River, and 

 furnished an inexhaustible supply of " war paint " to the native inhabi- 

 ants of the region. The Cleveland shale rests upon the 



ERIE SHALES. 



The largest measurement which I have obtained of these shales in the 

 county is thirty-two feet. They present characters similar to those 

 shown in the valley of the Cuyahoga, Chagrin, Grand and Ashtabula 

 River, i. e., are composed of soft, argillaceous, bluish shales with hard cal- 

 careo-silicious brands, a few inches in thickness. 



The great changes in the thickness of this formation, and its position 

 between the two beds of carbonaceous shales are of interest, as showing 

 the topography of the region, and the changes of level at the time of the 

 introduction of the carboniferous vegetation of the Coal Measures. 

 These two deposits of carbonaceous shales are as well-defined, and as 

 easily distinguished from the including strata, as beds of coal. They 

 may in one sense be called coal, containing from eighty-five to ninety 

 per cent, of ash, and having an origin similar to that of true cannel 

 coal. Carbonaceous matter from the vegetation of shore swamp or the 

 fucoids of a vast inland sea, finely comminuted, was deposited in still 

 water and mingled with the argillaceous mud of the sea-bottom. The 

 fine homogeneous material of which the shales are composed indicate 

 their deposition from quiet water ; and the wide range of the formation, 

 as well as the remains of huge fishes which it contains, forbid the idea of 

 its having accumulated in shallow swamps. Whatever may have been 

 the conditions under which the Huron shales were formed, these condi- 

 tions were abruptly changed ; and the epoch was followed by long con- 

 tinued intervals, in which the growth and deposit of this carbonaceous 

 matter was interrupted. 



A section of these three formations extending from Huron to Lake 



