124 ON CORAL REEFS AND ISLANDS. 



It is worthy of special note, that this axial line or line of 

 greatest depression coincides in direction with the mean trend of 

 the great ranges of islands, it having the course N. 52° W. 



The southern boundary line of the coral area, as we have laid 

 it down, lies within the area of subsidence, although near its 

 limits. There are places along this line where this area has been 

 prolonged farther than elsewhere. One of these regions lies be- 

 tween Samoa and Rotuma, and extends down to the Feejees and 

 Tonga Group; another is east of Samoa, reaching towards the 

 Hervey Group. Each of these extensions trends parallel with 

 the groups of islands ; and with the part of the line east of Ta- 

 hiti. It would seem, therefore, that the Society and Samoa 

 islands were regions of less change of level than the deep seas 

 about them. 



What may be the Extent of the Coral Subsidence ? — It is very 

 evident that the sinking of the Society, Samoan, and Hawaiian 

 Islands has been small compared with that required to submerge 

 all the lands on which the Paumotus and the other Pacific atolls 

 rest. One, two, or five hundred feet could not have buried 

 all the many peaks of these islands. Even the 1500 feet of 

 depression at the Gambier Group is shown to be at a distance 

 from the axis of the subsiding area. The groups of high islands 

 above mentioned contain summits from 4000 to 14,000 feet above 

 the sea ; and can we believe it possible that throughout this large 

 area, when the two hundred islands now sunk were above the 

 waves, there were none equal in altitude to the mean of these 

 heights ? That all should have been within nine thousand feet 

 in elevation, is by no means probable. However moderate our 

 estimate, there must still be allowed a sinking of several thou- 

 sand feet : and however much we increase it within probable 

 bounds, we shall not arrive at a more surprising change of level 

 than our continents show that they have undergone. 



Between the New Hebrides and Australia the reefs and islands 

 mark out another area of depression, which may have been simul- 

 taneously in progress. The long reef of one hundred and fifty 

 miles from the north cape of New Caledonia and the wide barrier 

 on the west cannot be explained without supposing a subsi- 

 dence of one or two thousand feet at the least. The distant bar- 

 rier of New Holland is proof of as great if not greater subsidence. 



Effect of the Subsidence. — The facts surveyed give us a long 

 insight into the past, and exhibit to us the Pacific scattered over 

 with lofty lands where there are now only humble monumental 

 atolls. Had there been no growing coral, the whole would have 

 passed without a record. These permanent registers, planted 

 ages past in various parts of the tropics, exhibit in enduring char- 

 acters the oscillations which the "stable" earth has since under- 

 gone. Thus Divine wisdom creates and makes the creations 



