470 



AUSTRALASIA. 



Samoa, whicli is regularly disposed in a long chaiu, is entirely volcanic, present- 

 ing nothing but basalt rocks, either still compact or reduced to tuffas and scoriae, 

 and differing greatly in age. Some are completely weathered on the surface, 

 while others appear to have little changed since the time when the lava streams 

 overflowed from their fiery furnaces. Tutuila, easternmost of the three large 

 islands, has no longer a central crater, all the cones having been obliterated by 

 weathering, while profound ravines have been opened in the flanks of the moun- 

 tains, whose original outlines can no longer be recognised. TJpolu, farther west, 

 presents a somewhat similar aspect, though the volcanoes have preserved their 

 regular slopes, scoriae, and craters in some districts. 



Lastly, the large island of Savaii, in the extreme west, forms a single igneous 



rig'. •iOo.— Samoa. 

 Scale 1 : 3,500.000. 



to 1,000 

 Fathoms. 



Depths. 



1,000 to 2,000 

 Fathoms. 



2,000 Fathoms 

 and upwards. 



60 Miles. 



mass, an Etna with central crater, with gently inclined slopes dotted over with, 

 numerous parasitic cones. A continuous forest clothes the central summit and the 

 zone of secondary crests, while every crater is embowered in verdure. Of all 

 the Samoan islands Savaii has the narrowest fringe of coral reefs, which Dana 

 attributes to the shorter period that has elapsed since the extinction of its vol- 

 canoes. The eastern islets also present the same coralline formation, relatively 

 larger in proportion to the longer time they have been quiescent. Rose, last link 

 of the chain, is probably an atoll built up by the polyps on the summit of an igneous 

 crest. Even on the reefs are seen here and there fragments of basalt, perhaps 

 deposited by the floating trunks of trees, or thrown out by passing boats as useless 

 ballast. 



