ELISHA MITCHELL SCIENTIFIC SOCIETY 100 
The river crosses the lower limit of tke fall line zone 
a little above Cheraw. ‘The shoals in the river at that 
point and for some distance above are not large, but they 
are sufficient to mark the passage of the river from its 
characteristics in the Piedmont plateau region to its 
typical coastal plain condition, that of a sluggish stream. 
GEOLOGIC CONDITIONS FAVORING WATERPOWER DEVELOPMENT AT THE 
FALL LINE. 
(1). The eastward tilting of the surface of these older 
crystalline rocks, and (2) the partial removal of the leose 
and easily eroded loams and gravels from the channel on 
the eastern slope of these rocks, have given this result- 
iug descent in the river surface at the fall line, which, in 
the Roanoke at Weldon, aggregates 85 feet in 9 miles. 
(3) The variation in the character of the rock, being 
harder and more obdurate at certain points, and softer, 
more jointed, more crushed, and hence more easily eroded 
at the intervening arcas, results in concentrating this 
fall of the stream at certain places; and (4) the existence 
of terraces along the river banks facilitates the con- 
struction of canals which still further concentrate the 
fall of the water. ‘These are the more important geo- 
logic conditions that favor the development of important 
waterpowers on the Roanoke at the fall line in the Wel- 
den region. 
Other striking cases illustrating the conditions favor- 
ing waterpower development on streams crossing geolog- 
ical contacts will be found mentioned on pp. — and — of 
this report. 
WATERPOWER IN THE SLATE BELTS. 
One of the most common types of geological structure 
affecting waterpower development in North Carolina 
