PRELIMINARY REPORT. 19 
larger than my fist!—the top of the bank being entirely covered by nul- 
lipores. We sounded across the bank in all possible directions, and 
examined it thoroughly with the water-glass, and at the stage of water 
at which we sounded found about eighteen inches difference from the 
soundings indicated by the charts. It is also greatly to be regretted that 
Dolphin Bank was not examined, either in 1839 or in 1869, and notes 
made of what species of corals, if any, were growing on its surface; for 
an excellent opportunity has been lost to determine the growth of corals 
during a period of sixty years. The choice of this bank as a standard to 
determine the growth of corals was unfortunate, as it is in the midst of 
an area comparatively free from corals. 
After refitting and coaling here, we left on the 5th Onibes for a cruise 
in the. Paumotus. 
We steamed for Makatea, which we had visited on our way to Tahiti, 
and not only examined the island more in detail, but took a number of 
photographs of the cliffs of the east side, which, on our first trip, we 
passed late in the afternoon. We crossed the island from west to east, 
the path leading down from the summit of the cliffs bordering the island 
into a sink at least forty to fifty feet lower than the rim of either face 
of the island. The sink occupies a little more than one-third the length 
of the island. It is deeper at its southern extremity, where it is said to 
be seventy-five to one hundred feet below the rim of the adjoining 
cliffs. 
It is difficult to determine if this sink is the remnant of the former 
lagoon of the island, or of a sound formed during its elevation; or if it 
has been formed by the action of rain and atmospheric agencies. The 
amount of denudation and erosion to which this island has been sub- 
jected is very great, as is clearly indicated by the small cafions, pinnacles, 
and walls of limestone, as well as by the crevasses which occur in the 
surface of the basin in all directions. The extent to which this action 
has penetrated into the mass of the island is also plainly shown by the 
great number of caverns which crop out at all levels along the sea face 
of the cliffs, some of which are of great height and extend as long 
galleries into the interior of the island. It is, of course, difficult, in the 
