PRELIMINARY REPORT. 25 
deep. Some of the smaller islets we visited, among which are Tikei, 
Aki-Aki, and Nukutavake, have no lagoons. The former has a small 
shallow sink in which fresh water collects, but the rim is only very 
slightly higher than the interior. The last two islets are apparently 
depressed in the centre, three to four feet below the outer bank of sand 
which forms the rim (about ten to twelve feet high) of the basin of the 
‘sland. I was at first inclined to look upon these islands as examples of 
islands which had been cut down to the level of the sea and subsequently 
been built up by beach rock and sand in the manner described above. 
The existence of extensive sand dunes on two sides of the island at 
Pinaki, and of large dunes (estimated to be thirty-five feet high) on 
the south shore of Nukutavake, seems to indicate the possibility of 
there having been a shallow lagoon occupying the centre of Aki-Aki 
and of Nukutavake, and that these lagoons were gradually filled by the 
sand dunes, much as Pinaki is filling now. 
At Pinaki (Whitsunday Island), there is no doubt that the lagoon is 
rapidly filling from the sand blown in by the dunes. They are from 
twelve to fifteen feet high, and are forcing their way in towards the 
lagoon, killing the pandanus and whatever vegetation there is growing on 
the land-rim of the lagoon. The dunes have probably filled also a 
second entrance to the lagoon, indicated now only by a somewhat lower 
level of the land-rim. Dr. Moore and Mr. Townsend, who went ashore 
at Pinaki, report that the lagoon is not more than three fathoms deep ; 
they could wade over the greater part of it. Mr. Alexander counted no 
less than 116 islets in this small lagoon—less than a mile in diameter — 
islets formed of masses of dead Tridacna shells thrown up on ledge rock, 
on the slopes of which grew madrepores. The bottom of the lagoon is 
covered by Tridacna, and masses of a species of Arca live near the edge ; 
the intervening spaces being filled with nullipores. The entrance to 
the lagoon is perhaps 150 feet wide, and there is a cut through the beach 
rock covering the old ledge giving access to the sea into the lagoon at 
certain stages of the tide. The water in the lagoon is quite warm. 
At Pinaki, as at other atolls and islets to the eastward, there are 
fewer cocoanuts than on the westward atolls, and the vegetation consists 
