DELTAS AT LOW LEVELS. 129 
meters) across from east to west. Its surface descends northward with 
moderate slope. Along its eastern side a small brook has cut a gulch. 
Three levels may be recognized in this form. The lowest is an ill de- 
fined bench 40 feet (12 meters) above the flood-plain of White river and 
about 65 feet (17 meters) above sea. From it the slope to the marsh be- 
low is 15 degrees. The terrace is composed of reddish brown sands of 
medium grain apparently derived from the Hocene sandstones, with 
small pebbles from the drift. The lobe is strongly convex toward the 
northwest. From the lowest bench the ‘surface rises gradually for 100 
yards (90 meters) to a second terrace edge at about 95 feet (30 meters) 
above sea. ‘This level is much more extensive than the lowest bench ; 
it is composed of the same materials, and represents a similar formation 
in deeper water. The alluvial plain rises very gently and uniformly 
southeastward to the third and highest flat, which is about 180 feet (55 
meters) above sea. Sparsely distributed over the delta are boulders, gen- 
erally of granite, which range up to 4 feet (1 meter) in diameter. 
This delta was produced by the stream which now flows along its 
northern edge. The water body in which it accumulated changed in 
depth during the growth of the delta. As the lower features are partly 
buried and the higher levels are not dissected, it is inferred that the water 
rose gradually and was subsequently rapidly lowered in such manner as 
to concentrate the stream on the eastern side. The boulders on the sur- 
face indicate the presence of floating ice. 
From the Talbot delta southward to Kent the eastern bank of the Du- 
wamish valley presents features for which the delta is a convenient ref- 
erence. Kast of Kent a remnant of a delta terrace borders the foot of 
the slope on the southern side of a gulch. Its surface rises from about 
70 feet (22 meters) above sea at the margin to 90 feet (27 meters) at the 
back. The brook which built it cut it through the middle. 
Nearer the Talbot delta the brook flowing from Panther lake has pro- 
duced a deposit of sands of faintly marked delta-form, but much obscured 
by forest and dissected by the brook. The sands extends northward for 
some distance along the slope as a nearly level flat a little less than 100 
feet (60 meters) abovesea. Spring brook, a small stream a mile (1.5 kilo- 
meters) south of the last described locality, has produced and bisected 
a cone of coarse gravels whose apex is 135 feet (41 meters) above sea, 
and whose lower portion may probably have been a delta corresponding 
to the Talbot delta at the lower levels. Between Spring brook and Kent 
a larger brook debouches into level meadows from a narrow ravine in an 
embayment in the slope. It does not possess an old delta. Across the 
embayment three remarkable ridges are thrown in parallelism. They 
rise 15 to 75 feet (4 to 28 meters) above the valley, are sharp crested, and 
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