PRESIDENTIAL ADDRESS. 35 
As one island strip was elevated soa parallel one within 
the same group was depressed proportionately. In this 
way, during the upward growth of the amorphous reefs, the 
atoll formations were formed which are associated with 
the elevated reefs. 
The unconformable bases of these later and non-bedded 
types of Pleistocene reefs, together with their coastal 
profiles, the original forms of which are discernible still 
with ease, indicate the growth of the elevated reefs of 
Tonga, Lau, and other groups, during subsidence. The 
action of submergence, unaccompanied by land subsidence 
is discussed below. 
The last movement of pronounced elevation is old, from 
the historical point of view, inasmuch as important barrier 
reeis have been formed around the islands since this date. 
The pauses in the general movement of undulatory uplift 
were of short duration only, and are indicated OY the narrow 
benches and parallel lines of marine erosion.’ 
It would be advisable at this stage to note the history 
of the western blocks of each main island group during the 
period that the eastern portions were sinking to receive 
their terraced caps of coral, and reémerging later in undu- 
latory and vibratory manner. 
It will be remembered that the Pleistocene period was 
one not alone of coral reef formation, but one also of marked 
glaciation, as Daly has shown so well. The formation of 
each great ice cap belonging to the Pleistocene was 
accompanied by a lowering of the ocean surface possibly 
to the extent of 150 to 250 feet, and, at later stages, each 

* Agassiz, A. Pacifle Coral Reefs, Mem. Mus. Comp. Zool., Harvard, 
1903, Plates. Andrews, H.C. The Limestones of Fiji, Bull. Mus. Com. 
Zool., Harvard, 1900, Plates. 
