202 TEANS ACTIONS OF THE [1892 



The dark lead colored, or red clays, which underlie the 

 white sandstone group near Falmouth, extend west at in- 

 tervals, and appear in force near the Rappahannock river, 

 east of Chancellorville. Along the eastern border of the 

 "Wilderness" tract, these clays contain iron ores, just the 

 same as those of the region lying near Washington, D. C. 



The cobblestone ranges of Yirginia do not agree with 

 those of the Chesapeake bay district of Maryland, nor 

 with those of the Raritan district in I^ew Jersey. In the 

 tidewater region of Maryland the Potomac formation has 

 not continuous stretches of cobblestone beds at base, like 

 those in Yirginia ; and those of the sandstone member of 

 the Albirupean in Maryland are chiefly made up of 

 medium size quartz gravel, in sharp white sand, quite 

 unlike any to be seen in the Fredericksburg area. 



In this part of Yirginia the Freestone series is not over- 

 laid by the iron ore group, but rests on it, wherever the 

 group has not been cut out by erosive agencies. Materials 

 from the iron ore series have, therefore, been carried into 

 the younger and more forcibly deposited, coarser forma- 

 tion, since it holds them, and partly overlies the homologue 

 of the " Yariegated Clays." Such intergradation as occurs 

 is a result of transportation where the materials have been 

 cut out of elevated beds and rapidly distributed over de- 

 graded and eroded basins. The friction of moving water 

 would speedily carry away much of the talus that had 

 fallen from cliifs along its borders, while the tremendous 

 weight of overflows from upper levels would tear out 

 bodies of movable clays and sands wherever they stood in 

 the way. Dislocations of wide surfaces of clifl^s of clay by 

 atmospheric agencies have been taking place along the 

 northern shores of Chesapeake bay, from time immem- 

 orial. So after a heavy storm, great masses of clay and 

 sandy marl have been torn from exposed cliifs, rolled out 

 into the current, or dropped into holes of the channels. 



