PRELIMINARY REPORT. jg 



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 exann'ned, 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 fiom corals. 



After refitting and coaling here, we left on the 5th October 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 diflScult to determine if this sink is the remnant of the former 

 lagoon of the i,sland, 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 canons, 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 



