246 VOYAGE TO THE 



chap- there is usually six or seven fathoms water ; reced- 



VIII. 



^-^— ' ing from it, the lead gradually descends to the 

 S?6. general level, of about twenty fathoms. The lagoon 

 contains an abundance of shell-fish, particularly 

 those of the pearl-oyster kind. The party in the 

 employ of the Dart sometimes collected seventeen 

 hundred of these shells in one day. 



The height of water in the lagoon is subject to 

 the variations of the tides of the ocean ; but it 

 suffers so many disturbances from the waves which 

 occasionally inundate the low parts of the surround- 

 ing land, that neither the rise of the tide nor the 

 time of high water can be estimated with any 

 degree of certainty. Were the communication be- 

 tween the lake and the sea larger, so as to admit of 

 the water finding its level, the period of low water 

 might be determined, as there is a change of tide in 

 the entrance. 



The strip of low land enclosing the lagoon is nearly 

 seventy miles in extent, and the part that is dry is about 

 a quarter of a mile in width. On the inner side, a 

 few yards from the margin of the lake, there is a low 

 bank formed of finely broken coral ; and, at the outer 

 edge, a much higher bank of large blocks of the same 

 material, long since removed from the reach of the 

 waves, and gradually preparing for the reception of 

 vegetation. Beyond this high bank there is a third 

 ridge, similar to that skirting the lagoon ; and out- 

 side it again, as well as in the lagoon, there is a wide 

 shelf three or four feet under water, the outer one 

 bearing upon its surface huge masses of broken 

 coral ; the materials for an outer bank, similar to the 

 large one just described. These appearances na- 

 turally suggest the idea of the island having risen 



