208 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



has in no way the appearance of the bottom of a lagoon, — at any rate, not of 

 such higoons as we now find in the atolls of the Paumotns, Ellice, Gilbert, 

 or Marshall groups. Judging from the soundings, if one of these atolls 

 were to be elevated, the bottom would be almost flat, and rise very rapidly 

 towards the outer edge to the rim. This is not the case with the basin 

 forming the elevated sink of Kambara, or of any of the so-called elevated 

 atolls. The slopes from the outer edges to the middle of the sink appear 

 to be gentle slopes of denudation, and here and there are huge spurs 

 running out as buttresses on the flanks of the rim, — a very different 

 structure from that found in any atoll we have examined, and to be 

 accounted for only by the difference in the degree of denudation and 

 erosion of the coralliferous limestone in different parts of the basin (PI. 

 126, fig. 1). These buttre.sses are covered with thick vegetation, and are in 

 marked contrast with the bare slopes of the volcanic cone on the western 

 face of Kambara. The limestone slopes of the outer edge of the rim are 

 both deeply eroded, and the whole surface is covered with pinnacles, with 

 crevasses, with cuts, and honeycombed in every direction, showing that the 

 weathering of that part of the i,sland, as well as the weathering of the 

 limestone fragments left on the slope of the volcanic outburst, has been 

 going on for a long period of time. Even if this sink represented the 

 remnant of an old lagoon, denudation has gone on long enough to alter 

 its shape radically, and to give it its present topography, — a very different 

 one from what it would have were it the bottom of the lagoon of an atoll 

 raised above the level of the .sea. The top of the limestone cliffs probably 

 forms the third terrace. The resemblance of the volcanic cone of Kambara 

 to Quoin Hill at Fulanga is striking ; both these hills have undoubtedly 

 been prominent factors in the formation of the characteristic topographical 

 features of Fulanga and of Kambara. They have broken through the 

 original limestone area and have formed, in this way, a more or less 

 incomplete sound, having probably here and there access to the sea. The 

 sea once having gained access to the interior of the limestone area began 

 its work of erosion and of disintegration, a process which was further 

 assisted by the large rainfall, and has helped to carry off, in solution or 

 in suspension, the limestone composing the elevated areas. Thus was left 



