MAHONING COUNTY. | : 189 
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 eccupies 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 
erew there and formed the coal, and depositing over all the submerged 
area a fine clay sediment, which, compressed and 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. Ata 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. Ina 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 ana of the Mahoning Valley Coal is so excellent, and th 
