I9I2.] STEVENSON— THE FORMATION OF COAL BEDS. 525 



level and that the water was excluded finally by deposition of 

 mineral matter on the bottom. Under such conditions, it would be 

 impossible to account for the formation of fossiliferous limestones 

 and shales within narrow well-defined areas at 2,000 feet below the 

 water-surface. It would be impossible to account for the distribu- 

 tion of conglomerates and pebble rocks, almost free from argil- 

 laceous matter, over great areas in the central parts of the basin. 

 100 or more miles from the shore and at a depth of several thousand 

 feet below the surface. It would be impossible to explain the 

 occurrence of sun cracks, ripple marks and clumps of plants in situ, 

 which are found at so many horizons throughout the column. It 

 would be almost impossible to discover a source for the material, 

 which has filled this vast basin of not less than 200.000 square miles 

 to a depth of 4,000 to not less than 6,000 feet. The Appalachian 

 land at the north would have been very narrow, for Carboniferous 

 beds, with coal, were forming in New England less than 175 miles 

 away at the east ; the lowland of Cincinnatia separated the basin 

 from the Indiana region where coal deposits were forming, no more 

 than 175 miles distant; while, at the northwest, the Michigan area 

 was filling, at less distance away. The land area would be insignifi- 

 cant on all sides except due north ; but one cannot accept that as the 

 source, unless willing to assign to the Pennsylvanian a duration 

 which would stagger the credulity of even the most generous geolo- 

 gist. The suggestion that the Appalachian basin was bounded at 

 the east by a great fault seems to be inadmissible for there is no 

 evidence that the fault exists. The Appalachian system of folding 

 originated far back in the Palaeozoic and continued through the 

 Devonian and Carboniferous. Its faults with insignificant excep- 

 tion are overthrusts toward the west ; but such overthrusts cannot 

 explain the origin of the basin, which could be formed, if formed 

 by a fault, only by a normal fault with hade toward the west. 



Each of the other suggestions, somewhat modified, would seem 

 competent to explain the phenomena ; but this statement is general. 

 In discussing a matter of this kind, one must endeavor to gain a 

 birdseye view of the whole area, for a problem so vast in extent 

 cannot be studied with a microscope. Many details have much 



