508 Prof. W. J. Sollas. Report to the Committee appointed 



of shells forming but an insignificant part of it ; calcareous algos are 

 more abundant, but its chief constituents are large foraminifera, 

 which seem to belong chiefly to two genera (Orbitolites and Tinoporus). 

 It covers a considerable area of the islands, and has accumulated dur- 

 ing the memory of the inhabitants to such an extent as to silt up 

 certain parts of the lagoon. This and the abundant growth of corals 

 and calcareous algse, such as Halimeda, lead to the belief that the 

 lagoon is slowly filling up. 



A suggestion has recently been made that more light is likely to 

 be thrown on the history of atolls by a study of ancient limestones 

 in the British Isles than by boring in existing reefs. The first essen- 

 tial, however, for such a study would appear to be a knowledge of 

 the structure of living atolls, for, without this, the identification of 

 others forming a part of the earth's crust, might remain more or less 

 a matter for conjecture. So far as the structure of Funafuti has 

 been proved by borings, it is scarcely what a field geologist might 

 have anticipated, and if deposits of a similar nature and origin 

 should have been encountered in, say, the mountain limestone, it is 

 doubtful whether, previous to the borings in Funafuti, their inter- 

 pretation would have been easily reached. 



While the boring has proved a failure, the other objects of the ex- 

 pedition have been attained with complete success. Messrs. Hedley 

 and Gardiner have made a thorough investigation of the fauna and 

 flora, both land and marine. Dr. Collingvvood has obtained a good 

 deal of information of ethnological interest, and we all have brought 

 home a fairly complete collection of native implements and manufac- 

 tures. A daily record was kept of maximum and minimum tempera- 

 ture, and of the readings of the dry and wet bulb thermometers. 



The most important contribution, however, and one that I think 

 must, in certain details, greatly modify our views as to the nature of 

 coral reefs, is afforded by the investigations of Captain Field. Never 

 before have soundings, both within and without an atoll, been so 

 closely and systematically made, and the results seem to me commen- 

 surate with the care and pains that have been taken to secure them. 

 Four series of soundings, " Sections " as they are termed on board 

 the " Penguin," have been run from the seaward face of the reef out- 

 wards. How close together the soundings were made is shown in 

 the following table which Captain Field has kindly permitted me to 

 copy from his order book : 



Depth 40 fathoms every 10 yards. 



40 70 . 20 



70100 30 



100150 ,; 40 



150200 50 



