PRESENT MINOR TOPOGRAPHIC FORMS. 121 
of corrasion. Its valley is readily divided in three sections, which differ 
in age and topographic forms. The upper heads in a huge amphitheater 
on the northern side of mount Rainier, and its extremity is occupied by 
a glacier four miles in length. The amphitheater and canyon leading 
from it are shut in by precipices from 1,000 to 4,000 feet (800 to 1,000 
meters) in height, composed of andesites of the great Tertiary volcano. 
Where this uppermost section of the valley, 16 miles (25 kilometers) from 
the present end of the glacier, passes into a series of Hocene sandstones 
and shales it widens notably, the slopes recede, and tributaries enter the 
river from the south. In this lower part of the uppermost section the 
river is bounded by a terrace approximately 60 feet (20 meters) above its 
present level. he terrace bench is of sand and gravel, with occasional 
large boulders resembling closely the material now deposited by the swift 
but overloaded stream, but underneath the river deposit lies an old lateral 
moraine which marks the former expansion of the existing glacier to a 
point 20 miles (382 kilometers) below its present end. This old moraine 
was discovered in driving a tunnel into the terrace for the purpose of 
opening the coal measures at the lowest available level. It is composed 
of the heterogeneous accumulations typical of morainic debris, including 
massive rocks up to 6 or 8 feet (2 to 2.5 meters) in diameter. The total 
length of the upper section of the river from the amphitheater in mount 
Rainier to where it narrows at its lower end is 20 miles (82 kilometers). 
The second section of the river is a steep sided canyon 5 miles (8 kilo- 
meters) in length, through which the stream passes in a series of rapids. 
The canyon walls are of Hocene sandstones and shales, with some intru- 
sive voleanic rocks. They are frequently perpendicular to heights of 
200 feet (60 meters) or more, and are crowned by steep slopes covered 
with gravel and sand up to a total height of 500 feet (153 meters) above 
the stream. In the upper 3 miles (5 kilometers) of its course through 
this canyon, the river receives no tributaries, and a swamp which lies 
500 feet (153 meters) above it on its eastern side is drained away from the 
river by a small creek. Carbonado is situated on the lower part of this 
canyon section, at a point where the stream turns from a northerly course 
to northwest. At this point, 400 feet (122 meters) above the present 
channel, there are older river courses continuing to the north and east- 
ward and intimately related to the positions of the ice front during the 
latest general glaciation of the sound. 
The third section of the river valley belongs to the Puyallup valley, 
one of the great hollows of the Puget Sound system, whose age and origin 
are at least open to discussion. 
Thus it is obvious that the valley of Carbon river consists of.an upper 
section which dates back to the inception of glaciation upon the Tertiary 
