548 PROCEEDINGS OF NKW V'ORK MEETING. 



tion : and it therefore seems wise t'> extend the terra applied to the formation in the 

 region in which it was tir-t discriminated. 



The sources of the materials of the formation have been fairly well ascertained: 

 The pebbles were derived in j «:i it from the Potomac formation of the immediate vicin- 

 ity, in part from the quartzite ridges and quartz v. 'ins of the Piedmont region and the 

 Blue Ridge, in part from the silicious dolomites of the central Appalachian zone, and 

 in part from the chert-bearing formations of the western Appalachian slope; and 

 these pebbles were evidently distributed by the rivers flowing along the lines of the 

 present great waterways of the region. A considerable elemenl of the loam came 

 from the Bame Bources ; but a part of it i< always local and reflect taracteristics 



of the various sub-terranes. 



In brief, the Appomattox formation forms a widespread terrane almost contermi- 

 nous with the Coastal Plain between the Rappahannock and the Mississippi; audit 

 i- an easily recognizable structural and chronologic unit, entitled t.> first rank as a 

 datum formation from which the stratigraphy and geologic history of the seaward p 

 tion of the Coastal Plain may be reckoned downward and backward. Although its 

 wide extent and essential unity have been established by a large number of observa- 

 tions, the exposures have 1 n correlated and the observations systemized by a method, 



which may be characterized as horn largely inspired and well illustrated by this 



formation. This method is Bet forth in detail elsewhere. 



On the close of the reading of this paper the Society adjourned to meel in 

 t he evening at 8 o'clock. 



After the r< cess Mr. McGee gave a brief synopsis of the paper, which was 

 followed by tin' discussion appended : 



Professor C. II Bitchcock : I would like to inquire if Mr. McGee can tell us the 

 precise relation- of this formation ? Where doe- it come in contact with the Pliocene : 

 and I do not quite understand its relation- to the Pleistocene? 



\l McGke: The formation is probably the exact stratigraphic equivalent of the 

 Pliocene. En central South Carolina it is overlain by the Pleistocene Columbia for- 

 mation and unconformably overlies the Miocene deposits, while fifty miles easta ard, 

 in the neighborhood of Charleston, fossiliferous Pliocene deposits are similarly inter- 

 calated between the Pleistocene Columbia formation and the fossiliferous Miocene 

 formation-. 



Professor W. M. Davis: If I undersl 1 Mr. McGei correctly this afternoon, he 



said thai the present Btreams follow inequalities which exist in the Burfai f the 



Columbia formation. I mi i thai the Columbia formation is redly only a mask over similar 



inequalities in the previously eroded Burfa f the earlier formations. The question 



ari- what terms should beapplied to streams of that kind ? Among the several 



terms that are now applied to rivers none fairly describe such examples as tl The 



on- are not strictly consequent on the Columbia, because the Columbia form is 



tliut of the underlying Ap] attoi formation : and they could hardly be said to be 



superimposed on the Appomattox, because their location accords too well with it- -ur- 

 facp, Bas any name been in the roind of the author for such Btreams? It is a diffi- 

 cult matter to invent pertinent name- i hat will be acceptable in general use; and yet 

 in bo clear a this of a new Btyle of streams some new name must be introduced. 



Mr VIcGi i : The class of rivers which I have described as cutting the Columbia and 

 Appomatto] formations alike is one which ha- definite existence, but for which no 



