NAMONUITO. 363 



Judging from the structure of Kusaie, of Ponapi, of Truk, of Yap, and of 

 the Pelevvs, we may infer that some of the low islands represent only a 

 state of greater denudation and submarine erosion than the groups I have 

 just mentioned. Truk is perhaps the best evidence we have that such 

 extensive denudation has taken place, for it requires but little imagination 

 to picture its islands reduced to the level of the sea, when Truk would be 

 an atoll similar in all respects to the larger low atolls like Namonuito, the 

 Mortlocks, and others, differing from them only in having numerous coral 

 flats upon which low islands like Gregoire, Brongniart, and many others in 

 the atoll have been thrown up. These low islands in their turn might 

 eventually be changed into mere coral shoals should the denudation go 

 on a step farther. We noticed that in Truk, as in the low atolls of tlie 

 Carolines, the principal land rim thrown up on the outer barrier reef is 

 found on the northern and the eastern faces, where the barrier reef flats 

 are exposed to the full action of the trades or of the sea during the change 

 of the trades and the prevalence of northerly winds. 



Namonuito. 



Plates m^ ; 233, fig. 1. 



The only one of the large low atolls of the Carolines we examined is the 

 Namonuito group. It is a triangularly shaped flat (PI. 233, fig. 1), its apex 

 towards the north, at a distance of about twenty-five miles from the south- 

 ern face of the reef, which is nearly forty-five miles in length. The lagoon 

 has been fairly surveyed in 1828,^ by the Russian ship '' Seniavina," which 

 crossed and recrossed the lagoon in several directions. The charts do not 

 indicate any features of interest other than those we observed. 



The southeastern point of Namonuito projects out as a sharp reef flat 

 covered by shallow water, enclosing a secondary lagoon very similar to those 

 on the northern and the northeastern points of Arhno, but there are no 

 islands on the sides of the secondary lagoon. 



On the extremity of the eastern spit rises the island of Pisaras, on which 

 a few cocoanut trees grow; it is flanked by coarse shingle, and a shingle 



1 A. Chart 772. 



