DESCRIPTION OF SMALL ISLANDS OF THE ATOLL. 95 



uction of the sea, has comparatively recently been surrounded l)y ii sand Ijcach thrown back from the 

 lagoon. (Fide Avalau.) 



The history of this corner of the atoll is nearly a repetition of that observed from Telalaoingo to this 

 point. The present condition of these two islets, Tengasu and Teafoafou, though the latter is much 

 larger in area, closely resembles that of Tefalaoingo {'pi'.), with this diftereuce, the ocean side of Teafoafou 

 is not driven back to such an extent as at Tefalaoingo, so that the earlier ocean boundarj' is still seen in 

 a less eroded breccia sheet, with its clusters of Ngie trees ; while the island itself is nuich wider than is 

 that of Tefalaoiuii'O, notwithstandiuii- tlic less hei^'ht of the Porifcs bosses. 



AVALAU. 



This island (Plate 5) is pleasant in appearance, its cocoanut and other trees attaining a height and vigour 

 fully uj) to the average. Its surface is moderately level, standing somewhat higher above high water 

 than Teafoafou, and is situated well back from the ocean bed of the platform. The present island has not 

 been greatly disturbed by invasions from the sea, though on its ocean side it has suffered in some degree. 

 The sea rolls over the breccia, which has been eroded to a gentle slope from the ocean platform (0.3) to 

 the beach, obstructed by only two or three low and narrow breccia scarps, and but few I'orites blocks ; 

 these not being nearly so large as was observed further north. As a result, where the direction of the 

 monsoons is at right angles to the beach, the sea has scattered for a considerable distance into the islands 

 whatever has been thrown up, so that it noAv exists as a wide but mild form of clinker field. Further 

 south, along its west side, where the seas strike it oljliquely, and can escape southwards, a normal 

 Hurricane Bank begins to be developed, till at the south-west corner it becomes of modei'ate proportions. 

 Along the southern end the Hurricane Bank is steep, and the clinker field rugged. These also 

 continue, till near its northern end, along the lagoon side, though in much reduced proportions, and 

 it is then succeeded by a sand bank scarcely higher than the general level of the island, and projecting 

 northwards. 



For a considerable portion of its northern surface, Avalau is formed of sand, Litltoihaiiuiion, and other' 

 fine fragmental material, presenting in its central portion a moderate area of level, open floor, with but 

 few trees. Here, near the centre of the island, and in this material, is the native well, the sides of which 

 exhibit a somewhat similar formation to that in which those at the main island have Ijcen made ; this 

 well supplies — after rain — water used by the natives for drinking purposes when their other sources of 

 supply fail. But since the bottom of it, as like those of Fongafale, is much below high water level, 

 the water disappears at every fall of the tide, and is forced back with the rise, thus being always 

 more or less brackish. Around the area which is occupied by this finer material, is one in which more 

 coral rubble, and some pumice, is intermingled, and here the trees are more numerous, and thrive much 

 better than they do in the Lithufhainuion material. 



Dividing this island from Teafoafou is a channel through which the tidal waters flow till the tide is 

 quite low. This channel bounds the north point of the projecting tongue-like foraminiferal sand bank, 

 which is 3 feet high above the platform, and partly submerged at high water. The slope of this bank 

 was inclined, when we were there, at the angle of 33", although it was not only submerged, but the 

 outgoing tidal waters were flowing past it. This sand beach, and those at the north of Tutanga and 

 Teafoafou, appear, from their direction and shape, to have been determined by the action of the waters of 

 the lagoon when agitated by reason of high tides and strong winds from the south driving the sea across 

 the reef between- Motungia and Avalau. This produces a scour along the lagoon side of Avalau, 

 Teafoafou, and Tutanga, and carries the finer material northwards, till it finds shelter at the northern 

 end of each of these islands. Here it is deposited, and now forms extensions, which, however, the high 

 westerly seas periodically disperse, much of it, no doubt, finding its way into the lagoon. 



The lagoon platform east of this island is very much extended, beyond the ordinary width of lagoon 



