204 W. M. DAVIS 
Murea, near Tahiti, may be briefly considered. Its dissection is 
far more advanced than that of Tahiti; its slopes are less steep, its 
embayments are much larger and wider; several spur ends of its 
northwest or leeward coast are rather strongly truncated in sloping 
facets resembling mature cliffs, but around most of its circuit the 
spurs descend gradually to sea-level; the barrier reef here is compara- 
tively close-set. Surely, if the great cliffs of Tahiti were cut under 
the conditions assumed in the glacial-control theory, great cliffs 
should have been cut at the same time around Murea, especially on 
its southern and eastern sides; the absence of such cliffs indicates 
that the sea has not had access to the island shore, or, in other words, 
that the encircling reef of Murea has long protected the island from 
abrasion. The absence of cliffs cannot be explained under the 
glacial-control theory by postulating an exceptional resistance for 
the lavas of Murea; for if the total duration of lowered sea-level 
during the glacial period were long enough for small streams to 
deepen their valleys and for the slow processes of weathering to 
widen the deepened valleys to the form now seen in the drowned- 
valley embayments in spite of the exceptional resistance postulated 
for the island lavas, then the waves of the lowered sea working 
through the same duration of time should all the more have cut 
great spur-end cliffs; for there can be no question that the waves 
of the trade-wind sea are much more powerful agents of island 
sculpture than the streams of short valleys and the weather changes 
on the valley sides. The same statement may be made for Raro- 
tonga in the Cook group; it is elaborately dissected by wide valleys, 
but its embayments are replaced by alluvial plains. Its spur ends 
are not clift. 
The Society Islands, therefore, do not support—indeed, they 
strongly contradict—the consequences expectable from the glacial- 
control theory as to the abrasion of preglacial reefs; and I believe 
that they likewise give no support to, if they do not contradict, the 
fundamental postulate of the “long period of nearly perfect stability 
for the general ocean floor” on which that theory is constructed; 
for the depth of submergence indicated by the form of the mountain 
slopes that inclose the embayed valleys of these islands demands a 
greater submergence than the glacial-control theory provides. 
