REEFS OF FIJI AND NEW CALEDONIA 545 



THE HALF-SUBMERGED CLIFFS OF NEW CALEDONIA 



If after its broad rock platform and liigli cliffs had been cut by the 

 waves, the Madras district of southeastern India, block C, figure 14, had 

 subsided beneath the sea, block E, instead of risen from the sea, block D, 

 it might be today fronted by a long barrier reef inclosing a lagoon, the 

 waters of which would lie against the partly submerged cliffs where fring- 

 ing reefs would thrive and enter many cliff -breaching valleys in the form 

 of branching bays. The amount of the subsidence could not be well 

 measured by the depth of the lagoon, because its floor would be aggraded 

 by an unknown thickness of sediments ; still less by the depth of the bays, 

 where river sediments would accumulate; the subsidence could be better 

 measured by the downward prolongation of the bay-side slopes with grad- 

 ually decreasing declivity, until their intersection marked the bottom of 

 the drowned valley that the bay represents. 



As the Madras district was fated to rise, we must go elsewhere for the 

 realization of a similar coast that has subsided; we fortunately find it 

 along the northeast side of N'ew Caledonia, which exhibits all the features 

 just outlined. Much of that side of this long island is cut off in strong 

 cliffs, which, although by no means vertical, still rise 500 or 1,000 feet 

 above sealevel, as in figure 15, although their base line is submerged sev- 

 eral hundred feet. The upper view, looking south, shows Thio, a delta- 

 front port at the mouth of an embayed and aggraded valley, from which 

 much nickel ore is shipped ; the high cliffs of the outer coast on the left are 

 followed by low cliffs on the spur ends of the valley side, a short distance 

 inland. The second view, also looking south, near the bay of Ba, illus- 

 trates the maturely even alignment of several cliffs that truncaie the spur 

 ends of the dissected highlands. The third and fourth views are of a 

 strongly truncated promontory between Laugier and Kuaua bays; one 

 shows the face of the cliffs, looking south; the other, looking southeast, 

 gives the profile ai the cliffs in strong contrast to the maturely carved 

 forms of subaerial erosion on the east side of Kuaua Bay. In these two 

 views the little vertical cliffs cut by lagoon waves at present sealevel are 

 seen at the apparent base of the great slanting cliffs of earlier origin, the 

 real base of which lies, as well as can be inferred from the slopes of the 

 bay sides, several hundred feet beloAV present sealevel. Singularly enough, 

 these great cliffs are hardly mentioned in the published accounts of N'ew 

 Caledonia ; or if mentioned they remain as completely unexplained as the 

 beautiful embayments by which they are interrupted. True, the cascades 

 that here and there leap down the cliff face from small hanging valleys 

 have occasionally excited comment; tlius Brenchley noted ^^a fine water- 



