26 E. C. ANDREWS. 
Taking the western zone as a datum, the remaining 
groups lie to the east thereof in the order of description 
here observed. 
These belts are parallel or subparallel to each other. 
The volcanoes may be dormant as Laté, or active as Kao. 
They rise as isolated cones from moderate sea depths. 
Tonga proper consists of very large plains and terraces. 
of coral reefs, rising from a few feet to 1050 feet above 
sea level. The profound sea depth known as the Tongan 
Trench forms the lowest portion of the compound earth- 
wave forming the group. 
az Society and Paumotu Groups.—The Society Islands. 
consist of a series of volcanoes, which are arranged along 
an arc whose curve is sympathetic with the main trend of 
the Tongan, and other associated groups. These volcanoes 
are encircled by coral reefs, but no elevated reefs have been 
recorded therefrom. 
The Paumotus, or Low Archipelago, represent a group: 
of elevated coral limestones and of atolls lying along a 
great land-wave crest related structurally to the volcanoes. 
of the Society Group. The Cook Group is a similar but less. 
impressive example of this type. 
(f) Important Geological Features Connected with the 
General Geology of these Island Groups.—There are at 
least six important features to which attention may be 
drawn at this stage of the discussion. © 
(1) The variations in the Tertiary and Pleistocene 
limestones. 
(2) The variable heights to which limestones belonging 
to these two periods occur in the various belts. 
of the individual island groups. 
(3) Variable structures composing the individual 
groups. 
