PRELIMINARY REPORT. 29 
pteropod ooze, and a few Globigerine. Between Namuka and Yangasé 
we obtained 324 fathoms; between Namuka and Marambo, 600 fathoms ; 
between it and Kambara, 450 fathoms; and finally, about fifteen miles 
west of Kambara, we sounded in 990 fathoms. These soundings would 
indicate a continuous plateau of moderate depths from Wailangilala south, 
upon which the islands of the Lau Group rise. 
On our way back to Papeete from the Paumotus we examined the east- 
ern cost of Tahiti, and from Papeete examined the western coast as far as 
Port Phaeton, at Taravoa Isthmus. We examined, in a general way, the 
Leeward Society Islands: Murea, Huaheine, Raiatea, Tahaa, Bora-Bora, 
Motu Iti, and Maupiti. There are excellent charts of the Society Islands, 
so that it was comparatively simple to examine the typical points of the 
group and to gain an idea of their structure as far as it relates to coral reefs. 
The Society Islands are all volcanic islands edged with shore platforms, 
some of great width, upon which thé barrier or the fringing reefs of the 
islands have grown. The structure of the reefs of the Society Islands is 
very similar to that of the Fiji reefs round volcanic islands. A comparison, 
for instance, of the charts of Kandavu, Viti Levu, Mbengha, Nairai, and of 
other volcanic islands in the Fijis, with those of the Society Group, will at 
once show the identity of their structure. Huge platforms of submarine 
denudation and erosion characterize both, with fringing and barrier reefs 
determined by local conditions. Perhaps it is easier to follow the changes 
which have taken place in the Society Islands; and such islands as Tahaa 
and Bora-Bora, where we anchored, as well as Maupiti,. are admirable 
examples and epitomes of the structure and mode of formation of the coral 
reefs of that group. 
In Motu Iti and Tetiaroa the volcanic peaks have disappeared, leaving 
nothing but a shallow platform, upon the outer edges of which sandy coral 
islets have been thrown up. There is, however, one point in which the 
barrier reefs of the Society Islands differ from those of Fiji. The barrier 
reefs in Fiji are generally indicated merely by reef flats, upon which the sea 
breaks, and an occasional rocky islet or negro-head ; only rarely do we find 
sand keys upon the fringing reefs of the islands of Fiji. In the Society 
Islands, on the contrary, we find the line of the barrier reefs usually well 
