262 GEOLOGY OF OHIO 



1. The present coal field of Ohio, at the beginning of the Carboni- 

 ferous Age, was occupied by an arm of the sea, the slowly-growing Cin- 

 cinnati Arch making its western boundary. 



2. Around the shores of this ancient gulf, marginal swamps of 

 varying width existed, which, by their long-continued growths and sub- 

 sequent fossilization, became the earliest coal seams. 



3. While the swamps were successively submerged and covered by 

 shales, sandstone and limestone, derived from or formed in the adjacent 

 sea, and were finally covered by other swamps, the continental nucleus 

 was slowly growing to the southward, as it had been growing from the 

 earliest records, and with it the Cincinnati Arch united, by a like advance 

 to the eastward, the combined movements gradually expelling the waters 

 of the gulf and converting the earlier formed portions of the coal field 

 into dry land. , 



4. Every successive coal-forming swamp, thus had a narrower area 

 than its predecessor. 



5. As all the coal seams were formed at sea level, so all were raised 

 by the continental growth to an approximate equality which their outer- 

 most outliers still retain. 



6. To look for the earlier formed seams in the center of the basin, 

 would be to look for the living among the dead. 



7. In the formation of one seam, in particular, the floor of this 

 gulf around which the coal swamps were growing, appears to have been 

 raised nearly to the sea level at many points, and coal appears to have 

 formed in island-like masses over much wider areas than any single 

 marginal swamp could account for. 



The importance of the facts that are here considered cannot well be 

 overstated. The resources of the Ohio coal field, as can easily be seen, 

 are intimately connected with and dependent upon the mode of growth 

 of the entire field. The affirmative answers to the questions proposed 

 in a preceding paragraph, would give us a hundred fold more coal within 

 the boundaries of the field than the answers that the facts oblige us 

 to make. It does not now appear that Ohio has any great stock of 

 deeply buried coal. At no point in the state have coal seams been 

 brought to our knowledge in the repeated tests for gas and oil that have 

 been carried forward in the last few years, at a greater depth than six or 

 eight hundred feet. It seems quite likety that these figures will make 

 the general limit of the extent of our coal seams as they descend towards 

 the center of the gulf around which they were formed. Such a depth 

 would be consistent with a breadth of seam of twenty to thirty miles, 

 the breadth being measured at right angles to the axis of the gulf. 



Value of coal. — One of the most striking generalizations of modern 

 science is to this effect : all the force that is in the world, available for 

 man's use, is derived from the sun. 



