96 APPENDIX ill. 



2)latfoim along the adjacent islands, by a wide sandstone deposit, passing in parts into a fine breccia, 

 which overlies tirst the lagoon conglomerate (L.3), and then the ordinary reef breccia. The lirst- 

 named of these ajjpears to be somewhat unconformable to the second, and both are decidedly so to the 

 third, and all again to the fourth ; the sandstone and fine breccia dip towards the N.E. at an angle 

 of about 6 , the fine Ijreccia resting on the sandstone, this on the conglomerate, and this on the reef 

 breccia. It is to be observed that tlie strike of the two upper deposits agrees approximately with a 

 line drawn fi'om the south end of Teafoafou to the next islands, Motungia and Nukusavalivali, Init 

 does not conform to the outline of this side of the present island nearest which its lower l)eds rest. 

 It would appear quite improljable and without support from similar phenomena observed in any part 

 of the islands of this atoll, that these sandstones could be laid down as we now find them, with the 

 scour usual at this locality, \vhich is at \vork at high tide during every strong S.E. wind, and is 

 sufficient, as we have seen, to drive away all the finer loose material along this and the neighbouring 

 islands, and to deflect it into the shelter of the iu)rth ends of each, where it is deposited as sand banks. 



The deposition of this newer sandstone, in my opinion, undoubtedly requires the shelter of some higher 

 land on the reef south of it than the present reef affords. This would at once provide from its waste 

 (1) the material of which the sandstone is formed; (2) an inclined bank along the direction of its strike 

 on which it could leposc, and (3) a jirotection from distur1)ing incursions from the sea, and so (4) the 

 presence of calm waters which our observations on this atoll show to bs essential to the laying down of 

 recent sandstones. To the south of these sandstones the reef breccia and conglomerate are uncovered for 

 a consideralde distance, the sandstone having a])parently lieen removed. Before the south of the island 

 is reached, a more or less sharp step occuis in the conglomeiate and breccias, varying in height from 

 2 feet G inches till it is lost. Its outline is roughly parallel, with a shallow depression commencing between 

 this and the reef south of this island, and deepening as it extends westerly into the lagoon. This 

 depression is now the channel to which gravitate the first waters which, at the rising of the tide, pass over 

 the reef in its vicinity and that circumstance has doubtless contributed to its excavation. This, with the 

 attacks from the sea duiing high tide and strong winds from the S.E., i.e., from the direction of the 

 prevailing wind, and the scour so produced, will go fai', when the outer contour of the reef is remembered, 

 to account l)Oth for the erosion of the depression, the partial removal of the sandstones, conglomerates, 

 and breccias, and the creation of the stej) or low cliff. 



MOTUNGIE. 



Occupying the extreme south of the atoll, between Avalau and Motiuigie, is a wide and long reef, in 

 ^^•i(lth lesemliling that occupying the extreme north of the atoll. On its western portion, and near to 

 Avalau, there is but a comparatively thin sheet of much eroded breccia, though here and there thickei' 

 portions occur; still in a few places it is veiy much thicker. The I'urih'^ masses have become less and 

 less as we have approached this point, ami ha\e now all but ceased to exist. Not far from niitlway 

 between Avalau and IMotiuigie some remnants of the breccia sheet attain a height of a foot above high 

 water level. Sweeping roun<l from Avalau seaward from these higher masses and on to Motiuigic, are 

 low breccia scarps, which indicate the site of successive boundaries fi'om whence the breccia sheet has 

 l)een eroded. In the same way the remaining high masses indicate the level which it inust have reached, 

 and has probably niitch exceeded. 



The highest of the long breccia scarps is far back on the platform, and is plainly one of the last outliers 

 of the breccia sheet, having till now i-esisted the unceasing attacks of the waves, to which in other jjarts 

 it has yielded. IJehintl or on the lagoon side of this outlier a clift' is formed, 6 feet high, and ending in 

 a depression in the breccia, in which a pool of water remains at low tide. Behind this and Ijeyond the 

 l)reccia covering the reef there lies a deposit of moderately coarse rubl)le driven into the shallow waters 

 of the lagoon. 



