JOHNSON: TALLULAH DISTRICT. 
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stream, A, which runs over softer rock, have been worn back as far 
as F, the falls on the tributary B have been worn back a much shorter 
distance in the hard rock, to the point Z; the retreat of the falls on 
the main stream past the mouths of smaller tributaries, as C, leaves 
the valleys of those streams hanging well above the bottom of the 
main gorge. These streams being small and weak, have not yet worn 
down to the new level, but are beginning that process, as shown by 
the slight notches in the walls of the gorge. The incision of the 
gorge in the bottom of the former more open valley leaves a series 
of benches or terraces marking the remnants of that former valley 
floor, except where the gorge has widened sufficiently to consume 
such terraces. The beheaded stream, A 1 , and its tributaries, C 2 , C 4 , 
etc., have become somewhat better adjusted to the new conditions; 
the alluvial fans are dissected and removed as the stream A 1 cuts 
down to a slightly lower level, and the tributaries bring in only such 
sediment as the main stream is able to remove. Branches F, F l , 
from the main stream in the gorge, possibly working back along a 
belt of weak rocks, or a crushed zone, begin to appear, the one at F 
