1871.] 117 [Shaler. 



the age which we must assign to the Cincinnati and the Richmond 

 axes. 



It would be very important to determine the age of the several 

 members of the central part "of the Appalachian chain ; as yet we 

 have no data to make the basis of such a determination, nor do we 

 even know the age of the rocks which compose the great mass of the 

 chain to the south of the Pennsylvania line. It is quite evident that 

 there has been a difference in the character of the movements which 

 have produced the upheavals of the section from northern Virginia 

 to the southward. To the north of that first-named line the chain is 

 characterized by the absence of great faults. These dislocations are 

 very frequent in the region to the southward. The existence of the 

 hot springs of Virginia is due to the great dislocations of that region. 

 The existence of a different class of irregularities in this part of the 

 Alleghany chain, points to the conclusion that the conditions of ele- 

 vation, and therefore likely the time of upheaval, was different from 

 that of the mountains to the northward. 



I am confident that the tertiary rocks which lie to the eastward of 

 the Richmond ridge have been so far uplifted by the original or some 

 subsequent elevation of this ridge, that they have had given to them 

 the additional height which produces the projection of Cape Hatteras. 

 Along the shore of the main land from Newbern, N. C., to Washing- 

 ton, at the mouth of the Roanoke, the hard, shelly limestone of the 

 Tertiary period, looking much like the shell bed which is found near 

 Charleston, S. C, comes to the surface just above high tide mark, 

 and seems to be the principal barrier to the encroachment of the sea. 

 At most points this shell bed is covered to the depth of several feet 

 by an accumulation of vegetable mould, but before the last subsidence 

 of this shore began it probably stood several feet higher. The dip 

 of these beds is so slight that it is impossible to obtain any distinct 

 indications of the slope. The relation of the beds is, therefore, to a 

 certain extent, inferential. 



We have determined that the Richmond axis must have been elevated 

 since the close of the Palaeozoic time. But we have found no reason 

 to conclude that it must have been uplifted at or near that period in 

 the earth's history. I am inclined to think that the only satisfactory 

 evidence concerning the period at which this uplift occurred must be 

 sought for at a point remote from this part of the coast, though closely 

 connected with it geologically. The belt of rocks of a Triassic or 

 Liassic age, to which the Richmond coal-field belongs, continues along 



