THE NORTHERN PACIFIC ROUTE. 185 
Rainier. This view may be had on the right while rounding the 
extreme pomt of the loop about 2 miles west of Stampede. The 
mountain is in view only for a moment and then is hidden by the 
nearer slopes. 
The rocks in the valley of Green River are the same as those seen on 
the east side. They consist of lava flows and beds of voleanic tuff that 
have been tilted in various directions. These rocks are known as the 
Keechelus andesitic series and most of them are of Miocene age. 
They represent the great floods of lava and fragmental material that 
were poured out before the Cascades were formed. They now form 
part of the broad platform upon which the great volcanic cones of 
Mount Rainier, Mount Adams, and Mount St. Helens are reared. 
The train runs down the mountain slope on the left side of Sunday 
Creek to the junction of that stream with Green River, which comes 
from the south. At present the road makes a long loop up Green 
River, but a new line is being constructed that will cut off this loop. 
The valley of Green River, as well as that of Sunday Creek, is broad 
and rounded and shows clearly that it has been cleared and modified 
by a glacier. The development, maximum extension, and retreat 
of the glaciers of this region are described below by Bailey Willis. 
from the Olympic Mountains, on the west; 
a larger one gathered along the base of 
the Cascade Range, on the east; the lar- 
‘Glacial development began in the 
high mountains climate, at one 
time milder than that now existing, grad- 
ually though not continuously increased 
in severity. As cold seasons grew longer 
d warm ones shorter, snow banks in 
the shadows of high peaks increased in 
volume and drifts accumulated in hol- 
lows less protected fromthesun. As they 
grew, the snow banks consolidated to ice, 
and, flowing downward, became glaciers. 
Each canyon received an onward-moving 
ice stream proportionate in size to the 
tributary area above it. The air was 
chilled, precipitation increased, and gla- 
ciers extended, and thus the effect of 
Th 
except over sharp, ogo peaks and 
ridges. Issuing from the foothills, the 
glaciers spread and oo ones coal- 
esced, forming broad piedmont glaciers. 
at the foot of the mountain) is 
to the mountain or alpine glaciers which 
feed it as a lake is related to its tributary 
—~ 
great ee pees met in 
the sieges Sound One was fed 
Sound. Tongues of these piedmont gla- 
ciers advanced along the valleys until 
opposing ice streams met and coalesced 
Then the ice mass deepened, as water 
may deepen in a lake. Land divides 
became peninsulas and isolated hills 
Hills of the Puget 
Inlet, the main channel leading to Puget 
Sound, and the southern extremity of the 
ice sheet spread beyond — and 
Olympia on the south and wes 
a change 
ach like those that brought on glacia- 
tion, are not understood. Then followed 
