336 Foerste — Ordomcian-Silurian Contact in the 



ferruginous layers have a thickness of 3 feet and are sent to the 

 iron furnaces along the Ohio river. The rock was originally a 

 detrital limestone, more or less oolitic, but has in the course of 

 time been replaced in part by a red iron ore which often pre- 

 serves the structure of the fragments and of the more complete 

 specimens of fossils, indicating the source of the material to 

 which the rock owes its original composition. The rock was 

 formerly quarried for use in smelters also at other localities in 

 Kentucky and Ohio, but the development of iron industries 

 elsewhere, in other states, on a much larger scale, has led to the 

 abandonment of these workings in the Clinton of Kentucky 

 and Ohio at all localities except at Owingsville. 



Pebbles are found in the Clinton of Ohio at other localities* 

 than the locality first described by Professor Orton. They are 

 abundant at several horizons in the Clinton near Sharpsville. 

 The area within which they are fairly common is indicated on 

 the accompanying map. It is interesting to notice that this 

 area is located directly east of the area in Indiana where peb- 

 bles are so common. At some localities in Ohio the pebbles 

 are of much larger size than those usually found in Indiana ; at 

 one locality 2 miles east of Belfast, pebbles 4 to 8 inches in 

 length are common, and quite a number attain a length of 12 

 inches. They are always strongly rounded. 



Wave-marks are characteristic of the top of the Clinton over 

 a wide area in Kentucky and Ohio. The extent of this terri- 

 tory is indicated on the accompanying map ; it is almost coin- 

 cident with the extent of the area containing -ferruginous 

 deposits. 



In case the Cincinnati geanticline was already sufficiently 

 developed in Clinton times to form a barrier in southern Ohio, 

 Indiana, and adjacent Kentucky, the opposition of conglomer- 

 atic and salmon-brown deposits of Clinton age, west of the 

 geanticline, to conglomeratic, ferruginous, and wave-marked 

 deposits east of the geanticline may have little connection. In 

 ease this barrier did not exist, the observations so far made are 

 in favor of a gradual diminution in thickness of the Clinton 

 across the northern part of the field. They do not exclude the 

 possibility of the former presence of the Clinton, thinning 

 westward, even across the northern extremity of Kentucky. 

 In this case the same cause may have been operative in both 

 territories, east and west of the geanticline. The evidence of 

 wave and current action is much stronger in the area east of 

 the geanticline than westward. It is impossible to determine 

 from the evidence at hand whether the few feet of Clinton 

 strata west of the geanticline, in the region nearest the areas 

 from which the Clinton is absent, are to be regarded as equiva- 



* Journ. Geol., iii, pp. 16-30. 





