1874.] 185 [Whittlesey. 



number along the central line, if the series shall be pierced by bor- 

 ings or by shafts, should be the same as at the out-crop. 



Secondly. — The beds may not be persistent in any direction, but 

 may thin out, both on their line of bearing and of dip ; and in this 

 case the number of beds musb be different at different parts. 



Thirdly. — There might be undulations of regular beds like those in 

 ny first hypothesis, which shall be persistent and parallel, which is 

 the theory of the Report. This I shall endeavor to show is an error. 



To make the demonstration complete there should be a map, and 

 correct physical sections, commencing at a central line near the mid- 

 dle of the basin, about midway between Steubenville and Pittsburg, 

 in West Virginia and Pennsylvania, and radiating from thence to the 

 west and north, at points on the border of the field. The Survey has 

 not yet furnished topographical materials to do this. To bring those 

 that are available into as compact a form as possible, I will assume 

 for the purpose of demonstration, Coal Seam No. 6 as a persistent 

 horizon, in accordance with the Report. 



If this seam is regular the others must be the same, forming parts 

 of a system; for if there are undulations resulting from the Alleghany 

 up-lifts, they occurred after the deposition. If the proofs of such 

 disturbances are wanting, the fact of irregularities being admitted, we 

 must look for a solution in the direction of unequal and irregular de- 

 position during the formation of the series. 



The mode of this deposition I consider to have been generally in 

 disturbed waters, on a shelving shore, — not necessarily a basin, — 

 where the beds did not reach downwards continuously to the centre 

 or deepest water. They were laid up along the sloping sides — coal, 

 limestone, sandstone and shales — by currents that were sometimes 

 strong, and at others sluggish, their dip more rapid than that of the 

 floor. The areas over which these changes occurred were often not 

 extensive. 



To bring all the observations in favor of merely local uniformity of 

 deposition together, would make this article altogether too lengthy, 

 and therefore I confine myself at present principally to physical or 

 topographical geology. 



The floor of the series in Ohio has a very irregular surface, and 

 therefore Coal Seam No. 1, as it is called, furnishes a very uncertain 

 horizon to reckon from. It (No. 1) is often interrupted, and when it 

 is again taken up, after a break of continuity, cannot be regarded as 

 a geological equivalent. The limestone beds, like the coal, show 



