MAHONING COUNTY. 785 



been sometimes misunderstood. The true reading of the geology of this 

 region is, however, briefly stated in the notes already given on the 

 Waverly. 



As is now generally known, Coal No. 1 occupies a series of limited and 

 sometimes disconnected basins which are separated by intervals of bar- 

 ren territory. The absence of coal from these latter areas seems to be 

 due to two causes ; first, its accumulation in narrow basins and chan- 

 nels ; and second, its partial removal by surface erosion. The first of 

 these causes is probably the chief one, as it is plain that the carbonaceous 

 material which now forms the coal seam was once peat which accumu- 

 lated in certain local depressions of the surface. These doubtless resem- 

 bled the peat swamps of the present day, and all who have examined 

 them know that they are sometimes broad basins many miles in extent, 

 and sometimes they fill long and narrow valleys traversed by sluggish 

 streams. At the time when the lowest coal seam in northern Ohio was 

 formed, the surface had been for some time exposed to sub-aerial erosion, 

 and in Mahoning and Trumbull counties was quite irregular. Subse- 

 quently the drainage which excavated the valleys seems to have been 

 checked, and the lower portions of the surface became marshes. Here 

 peat formed in some instances to the depth of fifty or sixty feet, and 

 covering the minor irregularities of the surface below the water line 

 with a sheet of spongy carbonaceous matter varying in thickness with 

 the depth. The highlands between the marshes and any points or 

 islands which rose above the highest water line were not covered by it. 

 After the lapse of many centuries, during which the conditions of the 

 surface remained as described, this region subsided and was overflowed 

 with water. The inundation was at first quiet, and comparatively still 

 water covered all the peat marshes, destroying the vegetation which 

 grew there and formed the coal, and depositing over all the submerged 

 area a fine clay sediment, which, compressed ari^d consolidated, we now 

 call shale. Naturally the weight of this sediment compressed the spongy 

 peat, and caused a marked subsidence of the material over it in the 

 deepest parts of the basin. Hence we find the strata of coal and shale 

 dipping from all sides downward toward these points, and the coal 

 terminating in a feather edge along the old water line. At a later date, 

 strong currents of water swept over the surface, locally cutting away 

 both clay and peat, and depositing over all a thick bed of sand, now 

 sandstone. In a few places gravel was mingled with the sand, and the 

 sandstone becomes locally a conglomerate, which has sometimes been 

 mistaken for the true conglomerate below. 

 The quality of the Mahoning Valley Coal is so excellent, and th 

 60 



