784 GEOLOGY OF OHIO. 



This has produced much confusion in the search for coal ; but all the 

 drillers have noticed that the surface of the Waverly is reached at 

 various depths, and that hills of " bottom rock " cut out the coal. In 

 such cases the coal was never formed on these hills, but accumlated in 

 lower ground surrounding them as a bed of peat that reach to a limited 

 distance up their side. When subsequently covered by clay, sand, and 

 gravel, the peat was compressed to perhaps one-fourth part of its original 

 thickness, and formed a bed of coal five or six feet thick in the bottom 

 of the basin, and running to a thin edge at the original water level. 

 These irregularities in the surface of the Waverly have been sometimes 

 attributed to disturbances and upheavals, but if they were folds in the 

 strata the coal would be carried up with the Waverly; but since we 

 find the Waverly hills composed of undisturbed and nearly horizontal 

 layers, and the coal not reaching the tops of the higher ones, we must 

 conclude that they are the result of erosion, and that before the deposi- 

 tion of the coal the surface was worn into hills and valleys much as 

 now. 



CONGLOMERATE. 



Probably but little of the area of Mahoning county is underlain by the 

 ■Conglomerate. Patches of it are found in the northwestern corner, and 

 these may extend for a long distance southward ; but the great sheet of 

 •Conglomerate which occupies Geauga and the northern part of Portage 

 .county, thins out rapidly toward the east, and between Niles and the 

 State line it either does not exist, or is represented by a thin bed of 

 -sandstone without pebbles. 



COAL NO. 1. 



This is the seam which furnishes the famous Briar Hill or Mahoning 

 coal, so extensively used for iron smelting, and widel}' distributed 

 through the markets of the northwest. It is the same seam that is so 

 largely worked in western Pennsylvania, at Sharon, Greenfield, etc., and 

 shipped to Erie under the name of the Ormsby coal. The true position 

 of this coal seam is from twenty to fifty f^et above the Conglomerate, the 

 interval being filled with shale, sandstone, and fire-clay. In Summit 

 and Stark counties, where the same strata are exposed as those which 

 form the banks of Mahoning at and below Youngstown, and were the 

 Conglomerate is generally from fifty to one hundred feet in thickness, 

 the position of Coal No. 1 is clearly shown and is always seen to be that 

 described above. In Mahoning county where the Conglomerate is often 

 absent form the series, and the Waverly rocks were extensively eroded 

 before the formation of the coal, the succession is less apparent and has 



