THE CARBONIFEROUS SYSTEM. 91 



seventy to seventy-five feet of argillaceous shale, of which the upper por- 

 tion is generally of a marked red color, while the lower portion is dark 

 bluish gray. These shales are very variable in their relative thickness, 

 sometimes one or the other filling the entire,interval between the Berea 

 grit above and the black Cleveland shale below, sometimes that interval 

 being equally divided between them, and sometimes again one or the 

 other greatly preponderating, while both are present. In the section 

 exposed at Bedford the red shale is scarcely visible, while it is met with 

 at Newburgh, five miles distant, and in the hills east of Cleveland fills 

 the larger part of the interval that separates the Berea grit from the 

 black shale which underlies the East Cleveland quarries. At Berea and 

 Elyria both shales are visible, while on the Vermilion — which takes its 

 name from this circumstance — the red shale is much more largely devel- 

 oped, and attains a thickness of something like sixty feet. In most 

 localities where the Bedford shale is exposed, the' upper surface is very 

 irregular, and it is evident that this formation has been extensively 

 eroded by the agency which transported the beds of sand now consoli- 

 dated into the Berea grit. It is probably due to this fact, that the red 

 shale is so frequently found to be wanting in the section. In the red 

 shale no fossils have as yet been discovered, doubtless for the same rea- 

 son that fossils are so generally absent from the sediments that contain 

 a sufficient amount of peroxide of iron to derive their color from this 

 source. The explanation of this phenomenon is very simple. The action 

 of carbon upon the sesquioxide of iron is to reduce it to the protoxide by 

 the absorption of one equivalent of its oxygen, so that in all deposits which 

 contain, when accumulating, a considerable percentage of organic matter, 

 this serves to reduce the iron to the protoxide, which imparts a bluish 

 or greenish color to the deposit. Where organic matter is absent the 

 iron passes to the condition of peroxide, and in this state, though in 

 small quantity, it communicates a bright red color to the materials im- 

 pregnated by it. 



The lower portion of the Bedford shale, though, like the upper part, 

 very fine and argillaceous, is generally dark gray or blue in color, con- 

 tains considerable lime, and is locally highly fossiliferous. The fossils 

 are most abundant in that portion which rests immediately upon the 

 black shale below, and here they are sometimes so numerous as to form 

 a large part of the mass. 



The following are some of the fossils derived from this horizon : Syrin- 

 goihyris lypa, Win. ; Orthis Michelini, Lev. ; Spiriferina solidirostris, White ; 

 Macrodon Hamiltonise, Hall; Hemipronites crenistria, Phil.; Chonetes Logani, 

 Hall; Lingula Cuyahoga, Hall; Rhynchonella Sagerana, Win. 



