2b0 VAST AMOUNT OF aUBSIDENCE. 



of atolls. It is, therefore, a striking fact, that in 

 the Friendly Archipelago, which consists of a group 

 of atolls upheaved and since partially worn down, 

 two volcanoes, and perhaps more, are historically 

 known to have been in action. On the other hand, 

 although most of the islands in the Pacific which 

 are encircled by barrier-reefs are of volcanic ori- 

 gin, often with the remnants of craters still distin- 

 guishable, not one of them is known to have ever 

 been in eruption. Hence, in these cases, it would 

 appear that volcanoes burst forth into action and 

 become extinguished on the same spots accordingly 

 as elevatory or subsiding movements prevail there. 

 Numberless facts could be adduced to prove that 

 upraised organic remains are common wherever 

 there are active volcanoes ; but until it could be 

 shown that in areas of subsidence volcanoes were 

 either absent or inactive, the inference, however 

 probable in itself, that their distribution depended 

 on the rising or falling of the earth's surface, would 

 have been hazardous. But now, I think, we may 

 freely admit this important deduction. 



Taking a final view of the map, and bearing in 

 mind the statements made with respect to the up- 

 raised organic remains, we must feel astonished at 

 the vastness of the areas which have suft'ered chan- 

 ges in level either downwards or upwards, within 

 a period not geologically remote. It would appear, 

 also, that the elevatory and subsiding movements 

 follow nearly tlie same laws. Throughout the 

 spaces interspersed with atolls, where not a single 

 peak of high land has been left above the level of 

 the sea, the sinking must have been immense in 

 amount. The sinking, moreover, whether contin- 

 uous, or recurrent with intervals sufficiently long 

 for the corals again to bring up their living edifices 

 to the surface, must necessarily have been extreme- 



