124 
B. WILLIS—-DRIFT PHENOMENA 
Distances between determined Elevations. 
OF PUGET SOUND. 
Elevations. White river. Stuck river. 
| By river. On the plain. By river. On the plain. 
Feet. Meters. | 
is Kilo- |, Kilo- : Kilo- ; Kilo- 
Miles. meters. Miles. meters. Miles. meters. Miles. meters. 
160-100 | 48.7-30.5 3.25 5.2 2.5 4 350) 5.6 3 4.8 
100- 50 | 30.5-15.3 | 10.25 16.4 6 9.6 6.5 10.4 5.5 8.8 
50— 0 | 15.3-0 24 38.4 15 24 10.5 16.8 U5 12 
From these measurements it appears that the fall per mile (1.6 kilo- 
meters) of White river in the three sections is, in round numbers, 5, ‘5, 
and 2 feet (4.5, 1.5, and 0.6 meters), respectively. These grades are very 
steep, but the river is aggrading and not degrading the form, because it 
always carries an excessive load. The cone is growing upstream by 
the addition of coarser material at its head. As its slope is thus raised 
the gravel and sands previously deposited on its surface are swept fur- 
ther down by the current, which is accelerated. Lower down the finer 
silt is moved by stages in a similar manner, coincidently with the 
building up of the cone, but where the slope passes below tide the con- 
struction is that of a delta terrace with a relatively bold front which 
descends into deep water. 
This topographic form is very delicately adjusted to sealevel. If by 
regional movement it should be lifted higher than its present attitude, 
the cone would be dissected by the river from the mouth retrogressively 
and would be represented in the readjusted topography by terrace rem- 
nants. There are no such fragments of any older cone in the Duwamish 
and Puyallup valleys, and their absence indicates that there has been no 
uplift from an attitude of greater depression during which the conditions 
of alluvial deposit were similar to those of the present. If, on the other 
hand, the land were appreciably more deeply submerged, the delta ter- 
race would extend beneath the sealevel as a broad shoal, upon which at 
some distance back from its earlier front a new delta would be built up. 
The United States Coast Survey charts show that the deltas are now 
being extended into water which deepens rapidly from 1 fathom (1.8 me- 
ters, at the delta’s edge to 50 fathoms (90 meters) three-fourths of a mile 
(1.2 kilometers) out, and which continues to deepen to 100 fathoms (183 
meters) or more. From this fact it follows that any subsidence of the 
land which may be going on is progressing at a rate which is less than 
that of the counterbalancing process of delta-building, 
