12 



South Anna rivers, and thence through City Point, and further south 

 in a direction not yet precisely ascertained. Much of the district 

 here defined exhibits Miocene as well as Eocene marl, the former 

 being found either in highlands remote from the rivers, or in the 

 superior parts of the river cliffs overlying the latter. The localities 

 abovje named were selected as points marking the eastern boundary 

 of ,this region, because at those places the Eocene marie was ob- 

 served to disappear below the water line by a gentle clip to the east. 

 Its existence extensively beneath the Miocene district may be looked 

 upon as highly probable, though under what circumstances as to 

 depth and inclination of the beds, we have no positive data to deter- 

 mine. 



MIOCENE MARL DISTRICT. 



In the most eastern portion of this division of the tertiary, the 

 general level of the surface is but little elevated above tide. The 

 country is a uniform fiat, in some places subject to be occasionally 

 overflowed. The rest of the region in cmestion has an elevation 

 above tide, varying from twenty to eighty feet. But few points, 

 however, in the district have a level corresponding to either of these 

 extremes, and by far the larger portion of the surface preserves a +S 

 height of from forty to fifty feet. 



The surface of this more elevated portion, though preserving a 

 general level of remarkable uniformity, is deeply channelled by innu- 

 merable ravines. The smaller of these connect themselves with 

 large ones, and these with the wider and deeper excavations forming 

 the beds of the creeks flowing into the neighbouring rivers. The 

 system of ravines connected with one river are separated by a nar- 

 row central tract from those connected with the next, and in a gene- 

 ral view of the district, these systems present the appearance of 

 mere creeks or inlets subordinate to the great rivers by which this 

 region is broken into peninsulas. The number and extent of the 

 large rivers and the navigable streams of this portion of the 

 state, constitute the most inestimable of its natural advantages. 

 The numerous creeks indenting its peninsulas furnish the cheap- 

 est and readiest avenues for a commerce which comes home to 

 the abodes even of its rural inhabitants, while its surface scooped 

 into ravines and its river cliffs washed by the tides, disclose the 

 rich materials which are hereafter to bestow the highest rewards 



