128 B. WILLIS—DRIFT PHENOMENA OF PUGET SOUND. 
in its form and in cross-section as that of a lateral moraine built across 
a reentrant angle in the banks which confined the glacier. 
The two instances described are the more striking occurrences of fea- 
tures traceable throughout the Duwamish and Puyallup valleys, so far 
as their banks have not been modified by landslides or by the lateral 
corrasion of the streams. These features demonstrate the fact that the 
valley was occupied by a glacier, which in retreat shrank into the hollow 
to depths which now lie beneath the modern alluvial cone. 
In the plateau, 2 to 4 miles (8 to 6 kilometers) east of the Duwamish 
valley, a channel extends from near Cedar river south by east for 7 miles 
(11 kilometers). It is occupied by swamps, through which meanders 
Big Soos creek. Its bottom is between 300 and 400 feet (91 to 122 me- 
ters) above sea. It is one-eighth to one-quarter of a mile (.2 to 4 kilo- 
meters) wide, and its slopes are steep embankments 100 to 150 feet (30 
to 45 meters) high. At several points along the course of this hollow 
narrow ridges are built. diagonally along the steep slopes. They are of 
coarse material, including large erratics of granite. They also are lat- 
eral moraines, which indicate that this hollow existed before the latest 
ice advance, and that during the last retreat from this area it was occu- 
pied by a glacial tongue after the general surface of the plateau was 
cleared. 
Hvidence of a similar kind, left by a glacier which followed the valleys 
from the southeast, is to be found on South Prairie creek, in the vicinity 
of South Prairie. One striking instance which occurs just west of the 
main road from South Prairie northwestward to Sumner is a small hill 
about fifty feet (15 meters) in height and 100 yards (90 meters) long, 
standing immediately on the margin of a gravel terrace. The terrace is 
200 feet (60 meters) high above the valley, and the hill is a dump heap 
of morainal material deposited from a glacier which occupied the valley. 
Deltas at low levels.—The features to be described under this head have 
been observed between Renton and Kent, along the eastern bank of the 
Duwamish valley. They are of limited occurrence. Their absence at 
the same levels elsewhere is due in part perhaps to their removal as the 
larger rivers cut away the slopes, and in greater part to the non-occur- 
rence of conditions favorable to their development. 
The Talbot delta is an alluvial form, herewith named from the old 
Talbot coal mine which was worked out beneath it, a mile and a quarter 
(2 kilometers) south of Renton. On its eastern side Eocene sandstones 
crop out in the plateau slope at 200 feet (60 meters) above sea; its west- 
ern margin is even with a bold bluff of similar sandstones which stands 
above the White river flood-plain at an altitude of 175 feet (53 meters) 
above sea. Between these outcrops lies the mass of sands 3,000 feet (915 
i, suxid 
