NORTHEAST-SOUTHWEST SERIES 491 



of Weldon, near which place the fall line makes its sharp bend to the 

 west, the line is continued southward in the topography along the 100- 

 foot contour line. 



THE NORTHEAST-SOUTHWEST SERIES 



Northern fall line. — By reference to the paper on Connecticut Rivers* 

 or to plate 45, it will be noted that a single line of definitely oriented 

 drainage along the direction measured as about north 48° east was indi- 

 cated on the map, though it was not found to be in correspondence with 

 any of the Pomperaug Valley faults, and was apparently without indi- 

 cated parallel lineaments in its vicinity. This line (H of plate 45) passes 

 along the entrance to New Haven harbor, while northeast of New Haven 

 for about 14 miles it follows the nearly rectilinear formation boundary 

 of the Newark system with the crystallines. Farther northeast, as 

 already indicated, it is in approximate correspondence with the course 

 of the Salmon river and with a branch of the Willimantic (see plate 46). 

 Still further extended along this direction it passes near the northern 

 shore of Massachusetts bay, and in Canada, the basalt bluffs forming the 

 steep southeast shore of the bay of Fundy. 



To the southwest from New Haven this line (H) is in approximate 

 correspondence with the Connecticut coastline (a " Rias " coast) and 

 with the western section of Long Island sound. Southwest of New York 

 cit}' its course is along the remarkable series of sharp and straight arms 

 of the Delaware river and the drowned Susquehanna and Potomac. It 

 thus connects the city of New York with Trenton, Philadelphia, and 

 Baltimore, and is, as shown by Powell,f a portion of the lineament, 

 traceable as far south as Macon, Georgia, along which the ancient mass 

 of the crystalline rocks to the westward is in contact with the later Cre- 

 taceous and Eocene deposits on the east. It is also a terrace line on 

 the land, and it is represented by rapids and falls in the streams. South 

 of the Potomac this fall line turns sharply to the southward, but the 

 line we have been following is continued in close correspondence with 

 the western border of the Piedmont plateau, as mapped by Powell. 

 The steep eastern wall of the Appalachian ranges begins at the 1,500- 

 foot contour line, and the high peaks of the range are to be found quite 

 close to this line. The wavy course of this 1,500 foot contour is outlined 

 on plate 46, where its general course is in correspondence with the linea- 

 ment we are considering. 



* Loc. cit. 



f J. W. Powell : Physiographic regions of the United States, National Geographic Monographs, 

 vol. i, no. 3, 1895, p. 73. 



LXIII— Bxjll. Geol. Soc. Am., Vol. 15, 1903 



