Drift near Seattle, Taconia and Olynipia. — I 'pliant. 205 
The c-haniicliiii;- of the dcc'i) valleys now occu])ic(l by Puget 
sound and its many inlets, ranging from common depths to 100, 
300, and 500 feet to a maximum of 918 feet a few miles north 
of Seattle, must be ascribed, as I think, to river erosion during 
the time of continental elevation inaugurating the Ice age. 
While these valleys w'ere being filled gradually by the grow- 
ing piedmont glaciers, sometimes retreating and again read- 
vancing, as we must suppose, their early till might become 
buried beneath stratified drift and a forest, which in their turn 
would be later overridden by the glaciers and long covered by 
the general glaciation. Therefore the intermittent glacial 
action shown by deposits of till underlying and overlying 
stratified drift, which sometimes contains layers of lignite, noted 
in various localities of the Puget sound region and attributed 
bv Willis and Russell to successive and distinct stages of gla- 
ciation, may perhaps be more probably explainable by moderate 
oscillations of the margins of the early glaciers, requiring no 
long stage, nor very notable secular climatic changes, as the 
lower till would represent a time before the broad and general 
ice accumulation. 
After the glaciers flowing outward from the mountains at 
the east and west had become united, the Puget sound basin 
was evidentlv filled by a typical lobe of the continental ice- 
sheet, the snow and ice being amassed to the greatest thickness 
and hight upon its central and axial part, thence flowing out- 
ward to the west through the strait of Juan de Fuca, and to 
the south, where it terminated at a curved border nearly on 
the same latitude with Mt. Rainier. From the sites of Seattle, 
Tacoma, and Olxinpia, the currents of the ice-lobe moved 
southeast and south, carrying drift from the arta of the sound 
upward fully thirty miles to a hight of 1,000 to 1,600 feet 
above the sea level near the base of the great snow-covered 
cone of Rainier, and reaching several miles farther south, to 
the latitude of that majestic white mountain, at the most 
southern limits of the icefields, about 100 to-400 feet above the 
sea, southwest, south, and southeast of Olympia. 
The lowest place in the southern watershed of Puget sound 
is aliout three miles southwest from Olympia, between that arm 
or inlet of the sound and Black lake, some two miles long, 
at the head of the P>lack river, a tributarv of the Chehalis river. 
