256 GEOLOGY OF OHIO 



district, there ma}* be five' seams, aggregating ten feet in thickness. The 

 chances are that in this case the first named field will be the more valu- 

 able; the second may not justify mining at all. To determine the rela- 

 tive values of coal lands, a number of consideration must be taken into 

 account. 



The maps that accompany this volume render it, for the first time, 

 possible to determine approximately the coal resources of the state. 

 They show the separate areas of the principal seams, above drainage. 

 To these areas there must be added the extensions of the several seams 

 under cover so far as they have been determined by test boriugs in 

 advance of development. In default of such tests, the additional areas 

 required in carrying the seam to some arbitrary depth below drainage, 

 as 300 or 500 feet, may be computed. Nothing but the vaguest estimates 

 of the amount of Ohio coals has heretofore been possible, but it is prob- 

 able that the amount is always exaggerated in our speculations on the 

 subject. A study of these maps will reveal the fact that our coal 

 resources are by no means co-extensive with the ten thousand square 

 miles of our Carboniferous rocks. Some important deductions from this 

 study will appear in a later section of this report. 



Origin of Coal. — For the last, fifty years, there has been no reason- 

 able ground for doubt as to the real nature and ultimate source of coal. 

 Coal is more or less metamorphosed vegetable structure, and conse- 

 quently the materials composing it were, in the main, derived from the 

 atmosphere, by the cells of growing plants, under the agency of sun- 

 light, at some earlier stage of the earth's history. These conclusions are 

 questioned by no one who has earned a right to an opinion. Occasion- 

 airy, it is true, some belated denizen of the seventeenth century still 

 attacks the problem of the origin of coal in the a priori wa3*, and 

 evolves a theory of its formation from his own consciousness. Such 

 theories do not deserve or require refutation. Like the seed sown in 

 stony places, they speedily wither because they have no root. They are 

 inventions, and not discoveries, and in our day at least, they are quite 

 sure to go to their own place and to be buried with their inventors. 



Again, for the last fifty years, there has been no reasonable ground 

 for doubt, or at least, ever-lessening reasonable ground for doubt, that 

 the vegetation which formed the coal grew where it is now found. It is 

 not drifted vegetation, but it was accumulated in situ, by the slow pro- 

 cesses of plant growth. This position received powerful support from a 

 famous paper of the late Sir William Logan, which was read before the 

 Geological Society of London, in 1841. It was entitled "On the Char- 

 acter of the Beds of Clay hying immediately below the coal seams of 

 South Wales." In it, Sir William announced the significant fact, which 

 had long been known by the miners and used by them as a guide in 

 their practical explorations, and from whom he had received it, that all the 

 coal seams of the South Wales field are underlaid by beds of clay, and that 



