CORAL ISLANDS. 383 



part, in situations where the winds are constant, being 

 arrived at the surface, affords a shelter, to leeward of 

 which their infant colonies may be safely sent forth ; and 

 to this, their instinctive foresight, it seems to be owing, 

 ,that the windward side of a reef exposed to the open sea, 

 is generally, if not always, the highest part, and rises al- 

 most perpendicular, sometimes from the depth of 200, 

 and perhaps many more fathoms. To be constantly co- 

 vered with water, seems necessary to the existence of the 

 animalcules, for they do not work, except in holes upon 

 the reef, beyond low- water mark ; but the coral, sand, 

 and other broken remnants thrown up by the sea, adhere 

 to the rock, and form & solid mass with it, as high as the 

 common tides reach. That elevation surpassed, the fu- 

 ture remnants, being rarely covered, lose their adhesive 

 property ; and remaining in a loose state, form what is 

 usually called a key, upon the top of the reef. The new 

 bank is not long in being visited by sea-birds : salt plants 

 take root upon it, and a soil begins to be formed ; a co- 

 coa-nut, or the drupe of a pandanus, is thrown on shore; 

 land birds visit it, and deposit the seeds of shrubs and 

 trees ; every high tide, and still more every gale, adds 

 something to the bank ; the form of an island is gradual- 

 ly assumed ; and last of all comes man to take possession. 

 " Half-way Island is well advanced in the above pro- 

 gressive state ; having been many years, probably some 

 ages, above the reach of the highest spring tides, or the 

 wash of the surf in the heaviest gales. I distinguished, 

 however, in the rock which forms its basis, the sand, co- 

 ral, and shells, formerly thrown up, in a more or less 

 perfect state of cohesion. Small pieces of wood, pumice 

 stone, and other extraneous bodies which chance had 

 mixed with the calcareous substances when the cohesion 



