PRESIDENTIAL ADDRESS. 15 
whose existence is believed to support this inference:— 
(a) The arrangement of the “‘ocean deeps”’ or trenches. 
(b) The distribution of the main earthquake zones. 
(c) The distribution of the principal volcanic belts. 
(d) The distribution of the ‘*‘ island arcs ’’ and plateaus. 
(e) The form of the floor of the Pacific. 
(f) The nature, distribution, and variable movements, 
of Kainozoic coralline limestones and of coral reefs 
within the Greater Pacific. 
The most impressive feature, suggested at first glance, 
concerning the first group of four of the above is their 
arrangement as broken, or discontinuous, girdles, of the 
Pacific. A feature almost equally impressive also is the 
great interference with these Pacific girdles by an outside 
but similar set, which we may call the Tethyan girdle, the 
individuals of which are arranged mainly in the north 
tropical and subtropical zones. 
(a) Zone of Deeps.—The ‘‘ ocean deeps’’ or trenches are 
arranged parallel or subparallel to the main trend of the 
land masses nearest to them, which in turn, have a trend 
sympathising in the main with that of the nearest conti- 
nental coast. 
Beginning with the Chilian area, and proceeding thence 
northward and returning by way of the Western Pacific 
and Antarctic, the order of their occurrence in space is the 
Heckel, Richards, Bartholomew, Krummel, Milne-Hdwards, 
Maury, Supan, Tuscarora, Challenger with Nero, Pelew, 
Philippine, Planet, Tongan, and Kermadec, Deeps. 
These deeps follow the west coast of South America and 
of Alaska closely, as also the eastern coast of Japan. In 
the Caroline, Marianne, Ladrone, and Philippine Groups, 
the Ocean Trenches are not collinear, but are arranged 
en echelon alternating with land crests which are dotted 
with islands, the latter being arranged linearly; thence by 
