Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.3)

April, 1836. FIELDS of dead coral. 549 the level of the lagoon. Now it acts in a directly contrary manner ; for the water, not only is not increased by currents from the outside, but is blown outwards by the force of the wind. Hence, it is observed, that the tides near the head of the lagoon do not rise so high during strong breezes as on ordinary occasions. This difference of level, although no doubt very small, has I believe caused the death of those coral groves, which under the former co^idition of things had attained the utmost possible limit of upward growth. A few miles north of Keehng there is another small lagoon island, the centre of which is nearly filled up. Cap- tain Ross found in the conglomerate of the outer coast a well rounded fragment of greenstone, rather larger than a man's head ; he and the men with him were so much sur- prised at this, that they brought it away and preserved it as a curiosity. The occurrence of this one stone, where every other particle of matter is calcareous, certainly is very puzzling. The island has scarcely ever been visited, nor is it probable that a ship 'had been wrecked there. From the absence of any better explanation, I came to the conclu- sion that it must have come there entangled in the roots of some large tree: when, however, I considered the great distance from the nearest land, the combination of chances against a stone thus being entangled, the tree washed into the sea, floated so far, then landed safely, and the stone finally so embedded as to allow of its discovery, 1 was almost ashamed of imagining a means of transport so improbable. It was therefore with great interest that I found Chamisso,* the justly distinguished naturalist who accompanied Kot- zebue, stating that the inhabitants of the Radack Archipelago, * Kotzebue's first voyage, vol. iii., p. 155. It is said, " The sea throws up on the reefs of Radack the trunks of northern firs (!) and trees of the torrid zone (palms, bamboos). It provides the inhabitants not only with timber for boats, but it also brings them in wrecks of European ships, the iron which they want." — " They receive, in a similar manner, another treasure, hard stones' fit for whetting. They are sought for in tlie roots and hollows of the trees which the sea throws up."