200 J. L. and H. D. Campbell — Wm. B. Rogers's 



Ridge, and known by different names, as Cittocton Mountain 

 in Loudoun county, Bull Run Mountain in Fauquier; and 

 farther to the southwest, its several parts are known as South- 

 west, Green and Findlay's Mountains. This leads to the in- 

 ference that the broken range thus designated was the shore 

 line of the Mesozoic sea in which these groups of strata were 

 originally deposited. 



Another point worthy of note, in connection with the topog- 

 raphy of the tracts, is that they differ from one another but 

 little in their elevation above tide-level, though separated by 

 intervals of many miles. This has been determined by the 

 surveys of the railway lines by which they are severally 

 traversed, and on which we give the elevations of only such 

 points as are actually on Mesozoic strata. For examples, on 

 the Virginia Midland Road, Manassas station is 317 feet above 

 tide ; the average elevation from that point to Culpeper is 300 

 feet ; the portion of the Manassas and Strasburg branch of the 

 same road, as far as it runs on this formation, has an average 

 elevation of 351 feet, the minimum being 317, and maximum 

 395 feet. On the Richmond and Danville road, Coal-field 

 station is elevated 320 feet above tide, and Powhatan station 

 317 feet. Farmville on the Norfolk & Western road, where it 

 crosses Mesozoic rocks, has an elevation of 316 feet. At these 

 several points only the Jurasso-Triassic beds (16-17) are found, 

 with none of the newer beds of Jurasso-Cretaceous overlying 

 them, hence we may conclude that they were elevated above 

 the level of the sea before the Cretaceous epoch. And, after 

 making allowance for a considerable amount of erosion and 

 denudation, we may very reasonably conclude that the sea 

 bottom, which received the latest deposits of 16-17, has been 

 lifted through a space of at least 400 feet above present tide- 

 level, plus the depth of the water in which those deposits were 

 made ; and that the uplift was simultaneous and very uniform 

 in extent, over an area 200 miles long and 50 or 60 miles wide, 

 or fully one thousand square miles. 



Tertiary Age. — Eocene, Miocene, Pliocene, (19 a, b, c.) — 

 Rocks of this age cover a very large area in the eastern part of 

 the State. A line from Aquia Creek, on the Potomac, running 

 south through Richmond and Petersburg to the North Carolina 

 line, would mark out approximately the western border of this 

 area, while it covers all the territory between that line and the 

 Atlantic coast. Its total length is about 130 miles by a 

 meridional line, and its width from Richmond eastward to the 

 mouth of the Rappahannock River is about 65 miles, and at 

 the latitude of Norfolk 80 miles. 



Although Quaternary Drift obscures much of the surface 

 of this Tertiary region, the banks and bluffs of the many 



