AGASSIZ: FIJI ISLANDS AND CORAL REEFS. 53 
case, I am inclined to consider these central basins as due to the action 
of atmospheric agencies, and to look upon them as similar to the gigantic 
banana holes, as they are called, occurring in the Bahamas, which are 
undoubtedly due to the solvent action of the rains overcharged with car- 
bonic acid, which carry off the limestones, and, percolating through the 
mass, leave the saucer-shaped basins characteristic of the so called ele- 
vated atolls. In such islands as Naiau, Vanua Vatu, Tuvuthaé, Kambara, 
and Wangava, the central depression has not extended very far towards 
the sealevel. But. in such islands as Mango the central depression has 
formed a small lagoon, in Namuka submarine erosion has carried off one 
side of the rim; in Fulanga (Plate 22) the process has been carried 
still further by the direct action of the sea and of submarine erosion, 
forming a large lagoon; and the conditions existing at Ongea, Yangasa, 
Aiwa, and finally at Reid Haven, Wailangilala, Ngele Levu, etc., illus- 
trate the different stages in the transformation by submarine erosion of a 
so called elevated atoll of tertiary age into an atoll of the present epoch. 
The probable extent to which atmospheric agencies have contributed 
to shape such central basins is also shown from the presence of exten- 
sive caves in the elevated limestone islands of Vatu Leile, of Thithia, 
and of Ngillangillah, and in the numerous cracks, caverns, and cavities 
which characterize the faces of the vertical bluffs of elevated limestone 
wherever we have met them in the Fijis (see Plates 74, 77, 92). 
VATU VARA, SEEN FROM THE EAST. 
Vatu Vara. 
Plate 19. 
On the last trip of the “ Yaralla” from Suva to Wailangilala, Captain 
Thomson examined for me the islands of Vatu Vara, Yathata, Kaimbo, 
and Naitamba. The accompanying account is based upon his notes. 
