222 DISTRIBUTION OF PLANTS. 



wide;" its Southeastern extreme being "in S. Lat. 18° 33' and W. 

 Long. 136° 21'." The rim of land appeared to be throughout about 

 eighteen feet high, or three times the height of some natives standing 

 among the shrubs; but a survey-party, in circumnavigating, discovered 

 a place where the land " was very low, as though the surf broke 

 over occasionally into the lagoon." 



Aware that we had reached the border of a new creation, I was 

 impatient to look upon growing East Indian plants ; and on the 14th, 

 towards noon, I obtained the opportunity of landing. 



The surf broke against a low bank, which proved a horizontal shelf 

 of dead coral, extending back about a hundred feet, and containing 

 shallow pools of clear water left by the tidal overflow. Two or three 

 boulder-like blocks of coral-rock, of several tons weight, were resting 

 on this shelf; while smaller fragments were strewed here and there, 

 some of them rounded by attrition in the surf; or in a few instances, 

 united by secondary adhesion into coral-rock conglomerate. 



Beyond the coral-shelf was a regular alluvial strand, rising gradu- 

 ally to the top of the island; which was found to consist principally 

 of angular fragments of coral-rock, in no respect rounded by the rains; 

 owing doubtless, as I had formerly observed in calcareous pebbles of 

 river-beds, to the great solubility of the material. The land proved 

 in fact only a beach, extending around in a ring ; and the sandy inner 

 slope being more gentle, the distance across, from the surf to the 

 " lagoon" or lake of sea-water, seemed about five hundred feet. 



For a long distance towards the centre of the lagoon, the water was 

 extremely shallow, as was ascertained by wading ; the bottom being 

 an even floor of coral-rock, much resembling some limestone strata, 

 and in like manner containing quantities of imbedded shells ; but on 

 closer examination, the imbedded species proved identical with living 

 ones around. Specimens of the ponderous Tridacna squamosa were 

 abundantly imbedded in their natural position ; while living specimens, 

 attached to the coral floor by the ligamentous byssus, seemed waiting 

 their turn ; except, that the floor being of dead coral was not suscep- 

 tible of further increase. The water of the lagoon was as transparent 

 as in mid-ocean ; the margin only, being rendered turbid and milky 

 white by the claj^ey decomposition of coral and shells. There was 

 no mineral basis ; the whole island, rock, pebbles, gravel, sand, and fine 

 earth, consisting exclusively of the debris of organic life, of successive 

 generations of corals and shells. 



