HYPOTHESES AS TO ORIGIN OF THE SOUND. 119 
the bottom. The Puget Sound hollows are excayated in or built around 
by drift, which almost completely buries the antecedent topography. 
= HYPOTHESES OF GENETIC PROCESSES 
General statement.—The Puget phase of the fiord type may probably 
be related to the Norwegian phase as genetically similar, with excess of 
elacial deposition over antecedent topographic relief in the Puget basin. 
This idea is consistent with two hypotheses of the origin of the hollows 
and plateaus, which may be stated as follows: 
The erosion hypothesis—As a result of general glaciation the Puget 
Sound basin was filled with drift to an approximately even plain. With 
retreat of the ice after one or several epochs of glaciation, streams were 
established, which cut their channels in the drift down to a level repre- 
sented by the depths of the Sound. In consequence of depression of 
the recion the valleys were submerged and the present inlets established. 
The construction hypothesis.—Glaciation of the Puget Sound basin was 
confluent, not indigenous. ‘The distinction is unportant in its bearing 
on the effects of advance and retreat of the ice. Where glaciation is in- 
digenous the accumulation begins at high altitudes, and the summits 
are covered with névé before the lower valleys are filled with ice. In 
the epoch of lessening glaciation the summits are last bared. But where 
glaciers become confluent in a region in which they do not originate the 
valleys are first occupied and filled and the hills are subsequently buried. 
When the ice-mass diminishes, the hilltops are laid bare while yet the 
valleys are the seats of glaciers. Glaciers first occupied the valleys of 
the Sound basin, but becoming dammed rose till the ice overtopped di- 
vides. During the episode of retreat hilltops appeared as nunataks, and 
this condition extended to divides. In ponded waters about these nuna- 
taks accumulated stratified drift. Stagnant ice lingered in the valleys 
to the latest stages of retreat, and, melting, perpetuated the hollows. By 
repetitions of this process the antecedent divides were built out to plateau 
forms and the axes of the original valleys were maintained as relatively 
shallow hollows, which are thus the casts of glacial tongues. Oscillations 
of level and the effects of erosion played a subordinate part. 
The erosion hypothesis is based upon analogies with fiords and estu- 
aries of other coasts. The construction hypothesis was first suggested 
to me by Russell upon the analogy of the Malaspina glacier. I received 
it with doubt, but detailed field work has tended to confirm and elab- 
orate it. 
DESCRIPTION OF MINOR TOPOGRAPHIC FEATURES 
ORDER OF TREATMENT 
The topographic features which are characteristic of the drift-covered 
XVIII—Burt. Grou. Soc. Am., Vou. 9, 1897 
