220 



SCIENCE. 



[N. S. Vol. XVII. No. 423. 



Dikes in the Oklahoma Panhandle: C. A. 



Waldo. 



In this paper the author referred to the 

 discovery of mineral dikes in the extreme 

 northwest townships of Oklahoma Terri- 

 tory. This section has not been carefully 

 mapped by the U. S. Geological Survey, 

 and it is a region about which little has 

 been written. The discovery of the dikes 

 resulted from an attempt to explain the 

 existence of extensive mineral deposits in 

 that locality, and was accomplished after 

 the failure in this particular of several 

 experts and hundreds of professional min- 

 eral prospectors. 



The Geographic Development of Western 

 Pennsylvania and Southern Neiv York: 

 Maetos R. Campbell, U. S. Geological 

 Survey. 



His study of the upland features of 

 western Pennsylvania and southern New 

 York has satisfied the author that this pla- 

 teau is not as old as the deeply dissected 

 upland of the bituminous coal field of 

 West Virginia and Kentucky. The latter 

 is generally regarded as of Cretaceous age ; 

 therefore, the former must date back only 

 to some part of the Tertiary. In review- 

 ing the work of Professor Davis in the 

 eastern part of the state, the author finds 

 evidence of a peneplain intermediate in 

 position and age between the Schooley 

 (Cretaceous) and the Somerville (Ter- 

 tiary) peneplain. This newly-recognized 

 feature is called the Harrisburg peneplain, 

 from its extensive development in the belt 

 of shale hills back of that city. It appears 

 that from whatever point this peneplain is 

 traced it rises .toward the New York line, 

 and the author has provisionally correlated 

 it with the general upland tops already 

 mentioned in the plateau region of north- 

 ern Pennsylvania and southern New York. 

 If this correlation is correct, the peneplain 

 has been deformed into an ellipsoidal. 



dome-shaped structure whose major axis 

 extends in a northeast-southwest direction, 

 and whose maximum development is at- 

 tained in Potter and McKean Counties, 

 Pennsylvania. 



The Blue Bidge of North Carolina: Wil- 

 liam Morris Davis, Harvard Univer- 

 sity. 



The Blue Ridge in northern North Caro- 

 lina and southern Virginia is not properly 

 a ridge with strong slopes descending on 

 either side of its crest line, but it is an 

 escarpment separating an uneven and often 

 mountainous upland on the northwest from 

 a rolling and occasionally mountainous 

 lower land on the southeast. The escarp- 

 ment is not determined by variation of 

 structure in the disordered schists in which 

 it is carved, but by the unequal length of 

 the rivers which drain the upland back of 

 it in the northwest and the lower land in 

 front of it on the southeast. The high 

 level head-waters of the northwestern 

 rivers, which discharge via the Mississippi 

 into the Gulf of Mexico, are constantly 

 losing length by the retreat of the escarp- 

 ment through the retrogressive erosion of 

 the low level head-waters of the shorter 

 Atlantic stream. There is no local indi- 

 cation that the sea has had any share in 

 producing the escarpment. 



The Fresh-water Tertiaries at Green River, 

 Wyoming: William Mobeis Davis, Har- 

 vard University. 



This paper gave an account of some de- 

 tailed observations on the stratigraphy of 

 the Tertiary strata at Green River, show- 

 ing the occurrence of variable deposits, in- 

 cluding frequent cardboard shales, alter- 

 nating with cross-bedded, ripple-marked 

 sandstones and with occasional shale-peb- 

 ble beds. An inquiry into the nature of 

 strata deposited in large lakes and on the 

 stream-washed surface of interior basins 



