FUNAFUTI. 227 



metrical range of corals in the interior of lagoons. Gardiner noticed that 

 corals grow in abundance on the slopes and summits of shallow shoals, but 

 were not found on the bottom of the lagoon. It is natural to suppose that 

 the silt from the shores of the lagoon and from the shoals should settle on 

 the bottom of the lagoon of Funafuti, so that corals would not grow there, 

 and that nothing but corallines or Nullipores would flourish in the midst of 

 that waste. He could find no signs that the lagoon was filling up at any 

 appreciable rate. He found, as I did, a hard bottom on the floor at many 

 points in the lagoon. Gardiner insists justly on the prominent part taken 

 by Nullipores and corallines in building up the thickness of a coral reef, 

 or its base, or in extending the rim of the reef seaward. 



The difference in the width of the outer reef platform of different atolls 

 may be due to the gradual piling up on the sea face of successive rows of 

 shingle and sand beaches. Where this has taken place regularly, an original 

 wide sea face reef flat may gradually become reduced to a narrow belt.^ 

 Well-marked cases of such narrow reef flats are found in the Marshall 

 and in the Gilbert Islands, and the land growth lagoonward from similar 

 causes is also well seen in islands of the same groups. That the outer rim 

 where coral reefs grow expands seaward, is seen on the slope of the 

 fringing reef off Papiete, Tahiti (PI. 209), as well as along all the sea faces 

 of islands where the slope is not too steep to allow the formation of a talus 

 made up of the dead material which has become loosened from the living 

 part of the coral slopes. 



Professor Sollas, in an address before the British Association for the 

 Advancement of Science, delivered at Bristol, gave an account of Funafuti. 

 He does not seem to have been aware that several attempts were made 

 to study coral reefs by boring before the middle of the last century," by 

 Wilkes, Belcher, and Beeohey. Professor Sollas states that an atoll like 

 Funafuti belongs to a family of atolls of unexceptional character, and that 

 the atolls of the Gilbert and Marshall Islands belong to a system all of 

 them excellent atolls. I would refer Professor Sollas to the Hydrographic 



• Soe also the notes of Hedley on the broadening of atoll islets, Natural Science, March, 1898, 

 p. 174. 



2 See Bull. M. C. Z., XXXIII. p. 4G (1899). 



