•222 Revicics— The A toll of Funafuti. 



Section v, written by Professor David and Mr. G. Sweet, F.G.S., 

 -deals with the geology of the Funafuti atoll. Describing first its 

 shape as a whole, they suggest that its elongation in a meridional 

 direction is due rather to its being situated in a volcanic zone or 

 fold-ridge, than to any influence of prevalent winds and ocean 

 currents. The prevalent winds are the north-west monsoons and 

 the south-east trades, the former being the stronger, and the storms 

 caused by both result in the formation of the hurricane beaches of 

 the islets. 



The islets, as shown on the maps and sections accompanying the 

 volume, may be divided into zones as already stated. A glance at the 

 maps, however, shows a much more detailed division of the surface 

 of the land than was given by Professor Sollas. It is to be regretted 

 that Professor Sollas' divisions and tliose of Professor David are not 

 compared, for in casually reading the account of one and then of 

 the other the correlation is not obvious. However, the order from 

 the ocean to the lagoon, and the correlation with the divisions of 

 Professor Sollas, seem to be as follows. The symbols on the maps 

 are given in brackets. 



1. The outermost rim of liviiig Lithotluimnion (O.L. 10) = the Nullipore Rim of 



Sollas. 



2. Zone of dead LithotJiamnion (0. 3) = the reef-flat of Sollas. 



3. Old reef of Ilelioporn and Porif^s (O.L. 1) ) = glacis of coral rock 



4. Breccia which overlies 3 (0. 2 B., 0. 2 C, 0. 2 D.) / of Sollas. 

 .5. Hurricane beach (0. 4) = hurricane beach of Solhis. 



6. Old reef of Hcliopora and Porites and breccia, \ 



together with various newer and older = central flat of islet of Sollas. 

 superficial deposits (L. 6, L. 7, etc.) ) 



7. Inner hurricane beach (0. 4), not always present. 



5. Various superficial deposits of lagoon beach (L. 8, L. 9). ^ 

 y. Old reef of Heliopora and Porites and breccia, cropping out ou i 



lagoon side. \ Not mentioned 



10. Zone of living Lithothamnion, present in channels leading into L by Sollas. 



the lagoon, and in some places ou the lagoon side of the 1 

 islets. 



The reef of Ilelioporn and Porites is the oldest rock whicli crops 

 out on the island, and is in most places covered by the breccia. 

 All the other deposits ai-e superficial, and lie irregularly on these, 

 which thus form the primitive reef-platform. 



The sequence of events, which is not very clearly stated, seems to 

 have been as follows : — First the Heliopora and Porites reef was 

 formed, and then there was an uplift of from six to ten feet, during 

 which time the breccia was formed by the marine denudation of the 

 reef. The land then sank about 8 feet, and the breccia became 

 cemented by Lithothnmnion. Then another elevation occurred, 

 allowing the breccia to come under the action of the waves which 

 made breaches in the breccia barrier; and so the several islets were 

 formed, and subsequently the Hurricane banks were piled up from 

 the material of the bi-eccia. Minor oscillations of level occurred, 

 the present subaerial deposits were laid down, and the present fauna 

 was introduced ; a deposit of silt killed the Heliopora near the 

 lagoon shore. Finally, there was an upward movement of G or 



