Page:Proceedings of the Royal Society of London Vol 60.djvu/544

508 of shells forming but an insignificant part of i t ; calcareous algce aremore abmidant, but its chief constituents are large foraminiferar which seem to belong chiefly to two genera and Tinoporus).. It covers a considerable area of the islands, and has accumulated during 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 essential, 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 anticipate/!, and if deposits of a similar nature and origin should have been encountered in, say, the mountain limestone, it isdoubtful whether, previous to the borings in Funafuti, their interpretation would have been easily reached.

While the boring has proved a failure, the other objects of the expedition 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. Collingwood has obtained a good deal of information of ethnological interest, and we all have brought home a fairly complete collection of native implements and manufactures. A daily record was kept of maximum and minimum temperature, 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 commensurate 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 outwards. How close together the soundings wei’e made is shown in the following table which Captain Field has kindly permitted me to copy from his order book —

Depth 0— 40 fathoms every 40— 70 55 9* 70—100 5 5 100—150 V 150—200 1) 10 yards. 20 „ 30 „ 40 „ 50 5 ?