BLL'E RIDGE OF NOETH CAROLINA 543 



PORPHYRITIC APPEARANCE OF ROCKS 

 BY A. C LANE 



The two papers are printed as pages 369-406 of this volume. 

 The fifth paper was 



PLVMOSE DIABASE COXTAIXIXG SIDEROMELAN AXD SPHERULES OF CALCITE 



AND BLUE QUARTZ 



BY B. K. EMERSON 



Remarks were made by A. C. Lane and F. B. Peck. 

 The sixth paper was 



CONFIGURATION OF THE ROCK FLOOR OF THE VICINITY OF NEW YORK 



BY W. H. HOBBS 



The paper was discussed by J. F. Kemp, Bailey Willis, J. W. Spencer, 

 and the author. An abstract is printed in Science, volume xvii, page 

 298. 



The seventh paper was 



SUBMARINE VALLEYS OFF THE AMERICAN COAST AND IN THE NORTH A TLANTIC 



BY J. \\\ SPENCEK 



The paper is printed as pages 207-226 of this volume. 



The next two papers, by the same author, and the last ones presented 

 on Wednesday, w^ere received from Section E. 



THE BLUE RIDGE OF NORTH CAROLINA 

 BY W. M. DAVIS 



\_Ahstract'] 



The " Blue Rid^e " in northern North CaroUna and southern A^irginia is not prop- 

 erly a ridge with strong slopes descending on either side of its crest line, but an 

 escarpment separating an uneven and often mountainous upland on the northwest 

 from a rolling and occasionally mountainous lower land on the southeast. The 

 escarpment 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 on the northwest and the lower land in front of it on the south- 

 east. The high-level headwaters of the northwestern rivers, which discharge via 

 the Mississippi into the gulf of Mexico, are constantly losing length by the retreat 

 of the escarpment through the retrogressive erosion of the low-level headwaters of 

 the shorter Atlantic streams. There is no local indication that the sea has had 

 any share in producing the escarpments. 



LXXV— Bui.i-. Geol. Soc. Am., Voi,. 14. 1902 



