810 WM. SIDNEY TANGIER SMITH 
of the two stream profiles, CBA and CDE. If faulting 
occurs parallel to this divide, with a downthrow toward the left, 
it may occur on either side of C (leaving out of the question 
the possible occurrence of a fault at C itself). Suppose, first, 
that the fault is to the left of C, at B (Fig. 1), and that the 
B! Ct 
3 Gi D’ 
A B Zp 
ee Cc Ec 
B’ D 
Fic. 1. 
faulted portions have assumed the positions indicated by B” C’ 
D’ Eand AB’, A and E representing the limits of movement 
in either direction.t The part B C will have had its angle of 
slope decreased by elevation, and therefore the rate of erosion 
on this slope will be diminished. The angle of the slope CDE, 
however, will have been increased, and its rate of erosion will be 
correspondingly greater. The slope C’D’E, then, will be cut 
away more rapidly than the opposite slope, C’B", and the divide, 
C’, will migrate toward Bis in, accordance with) the mormnal 
operation of the law. This condition, however, will last only a 
comparatively short time, for on account of the high angle of 
BB’ erosion on this slope will be very vigorous, and the point 
B" will be rapidly carried back toward C’, till the two meet. 
When this stage is reached the edge of the faulted block will be 
represented by C", and the profile, approximately, by B’C'E. 
Further erosion will tend to carry the crest C" toward E, owing 
to the more rapid cutting on the steeper slope, B’ C’. The 
final result will be that the point C” is carried to some point 
such as D’, the exact position of which depends on the relative 
attitude of the points which correspond to B’ and E, when 
erosion has reached this stage. 
The second case (Fig. 2), when the faulting is between the 
« These sections are diagrammatic, and do not attempt to give the exact relative 
positions of the two parts, as these positions depend on the circumstances obtaining 
at the time of faulting. 
