RADACK AND OTHER ISLANDS. 141 



of the basin. They seem to be of the same nature 

 as the surrounding wall, but never project above 

 the surface. The inner sea, or lagoon, in the 

 more considerable group of Kavven, was from twenty- 

 five to thirty-two fathoms in depth ; in the smaller 

 one of Eilu, twenty-two fathoms, with numerous 

 shoals. The bottom is finer or coarser coral sand, 

 and in some places corals. The ocean is already 

 coloured, at this depth, with the deep azure blue 

 which distinguishes the pure waters of this ocean. 

 The eye recognizes the shoals at a distance, and 

 the lead may be dispensed with. 



That part of the reef which projects abov^e the 

 water, and which may be examined, consists of al- 

 most horizontal masses of hard lime-stone, difficult 

 to be broken, which is composed sometimes of finer, 

 and sometimes of coarser fragments of madrepores, 

 mixed witli numerous shells and thorns of sea 

 hedge-hogs, and breaks in large tables, which 

 loudly sound under the hammer. The stone con- 

 tains the lythophytes only as fragments, and no 

 where in the situation in which they have grown 

 and lived. 



The surface of the dam is swept and smoothed, 

 on its edge turned to the exterior sea, by the 

 dashing of the surf. On the outer edge itself, 

 against which the breakers rage, blocks of the 

 stone have been torn up from their places. Such 

 blocks are found again scattered here and there, 

 on the side turned to the Lairiuia. This siile is 



