183fi.j STONES TKANSPOrtlED BY TREES. 4GI 



channels into several islets ; this fact is likewise indicated by the 

 trees being younger on these portions. Under the former con- 

 dition of the reef, a strong breeze, by throwing more water over 

 the barrier, would tend to raise the level of the lagoon. Kow 

 it acts in a directly contrary manner ; for the water within the 

 lagoon not only is not increased by currents from the outside, 

 but is itself blown outwards by the force of the wind. Hence 

 it is observed, that the tide near the head of the lagcwon does not 

 rise so hiffh during: a strong breeze as it does when it is calm. 

 This difference of level, although no doubt very small, has, I 

 believe, caused the death of those coral-groves, which under the 

 former and more open condition of the outer reef had attained 

 the utmost possible limit of upward growth. 



A few miles north of Keeling there is another small atoll, 

 the lagoon of which is nearly filled up with coral-mud. Captain 

 Ross found embedded in the conglomerate on 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 surprised at this, that 

 they brought it away and preserved it as a curiosity. The oc- 

 currence of this one stone, where every other particle cf 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 conclusion that it must have come 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 Mashed into the sea, floated 

 so far, then landed safely, and the stone finally so embedded as 

 to allow of its discovery, I was almost afraid of imagining a 

 means of transport apparently so improbable. It was therefore 

 with great interest that I found Chamisso, the justly distin- 

 guished naturalist who accompanied Kotzebue, stating that the 

 inhabitants of the Radack archipelago, a group of lagoon-islands 

 in the midst of the Pacific, obtained stones for sharpening their 

 instruments by searching the roots of trees which are cast upon 

 the beach. It will be evident that tliis must have happened 

 several times, since laws have been established that such stones 

 belong to the chief, and a punishment is inflicted on any one 

 v/ho attempts to steal them. AVhen the isolated position of these 



