48 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
ness, — 800 feet at Tuvutha, 1,000 feet at Vatu Vara. Therefore as 
soon as the drill struck the limestones it might correspond to any 
height in the beds exposed elsewhere, beds which at Mango, Kambara, 
and Vanua Mbalavu we had observed to rest upon a volcanic substratum. 
It was natural that immediately on my return to Suva after our first 
trip round the Eastern Archipelago I should send to Wailangilala or- 
ders to stop further boring, and to bring the crew and machinery back 
to Suva. For it seemed a waste of both time and money to bore and 
obtain a core from an indefinite datum plane, when the same evidence 
could be obtained by the examination of any one of the bluffs of ele- 
vated coralliferous limestones with which we had become familiar in our 
first trip. But, unfortunately, we were not equipped to make a thorough 
exploration of such a section, not being provided with explosives or 
drills, and had to content ourselves with somewhat fragmentary collec- 
tions at the more accessible points. However, this is a subject which 
I hope to attack again under more favorable conditions. 
The boring at Wailangilala shows that the island is the fragment of 
an ancient island of larger size, which once covered the whole area of the 
lagoon. Being at the northern extremity of the atoll, it was less subject 
to the destructive agency of the sea due to the prevailing southeasterly 
winds, and thus there was left a wider reef flat, the last to be worn 
away by the action of the sea. It also shows that at a depth of forty 
feet we meet the underlying elevated limestone forming the substratum 
of the northern reef flat of the lagoon. As will be noticed from the 
Figure on page 46, the western reef flat is much narrower than the 
eastern and less exposed face of the lagoon. 
The boring at Wailangilala is from the remains of an upheaved coral 
island, as has been suggested by Gardiner ;* but it is also the remnant 
of an island which once occupied the whole of that part of the atoll. 
Aiwa shows a stage antecedent to that of Wailangilala, the island on the 
rim of the lagoon being still of considerable height. Many of the reef 
rocks (negro-heads), which Gardiner considers as having been thrown up 
by hurricanes, are the remnants of the elevated reef-rock outliers left 
from the denudation of the flats on which they oceur, and which once 
rose to a greater height but have gradually been eroded and planed down 
to their present elevation. 
But Gardiner is wrong in assuming that the islands of the atolls are 
converted into land. Such is by no means necessarily the case. The 
islands on the rim of an atoll, as Ngele Levu, consist of elevated coral- 
1 Loe. cit., p. 445. 
