88 THE GEOLOGY OF FUNAFUTI. 



tion to receive them all without materially atiectiug its depth. The main island, 

 liowever, though receding slowly on the ocean side, has certainly gained considerably 

 in width, in the immediate past, through the deposit against its lagoon shore, near 

 Fongafale, of foraminiferal and Ilahmeda sand, and there is every probability that it 

 will continue to so gain in the near future. 



We have already given many reasons, in the earlier part of this rejDort, for our 

 opinion that probably the atoll is slowly enlarging its periphery. It will be interesting 

 in years to come to compare the outline of the reef at the main island, opposite the 

 diamond-drill camp at the 1114 feet bore, with that shown on the carefully measured 

 plan of Mr. Fjnckh on Plate 17 and that of Mr. Halligan on Plate 19. It will 

 also be of interest to refer the Admiralty Bench mark on the Mission Church and 

 the permanent marks fixed by Mr. Halligan and Mr. Finckh on the ocean and 

 lagoon platforms of the main island to the level of low-water spring tides in the 

 future. The Lithothamnion itself, in the neighbourhood of these marks wliere the 

 latter were placed in the living Lithothamnion zone (O.L.IO) should serve as a fair 

 tide-gauge to indicate upward or downward movement of the order of 5 or 6 inches ; 

 for an emergence of G inches would probably suffice to kill a large area of the 

 Lithothamnion now occupying the zone O.L.IO on the ocean side of the reef 



The surfice geological evidence collected by us proves, in our opinion, that several 

 oscillatory vertical movements of the shore have taken place in the immediate past 

 at Funafuti, and we should not, therefore, be surprised if the evidence gained from 

 the core shows that movements of the shore-line in both directions have occurred 

 at Funafuti at earlier epochs. 



With regard to the geological maps of the atoll, other than the portions shown on 

 Plates 17 and 19, no pretence to more than general accuracy can be claimed for them. 

 It is hoped, nevertheless, that they may prove of use not only in illustrating our 

 jDresent views as to the atoll's structure, but also for later reference, when possible 

 clianges on a larger scale in its physical geography and geology are being studied by 

 future observers. 



\_Xote. — In the manuscript of this Report, the Authors, to avoid prejudging the question whether the 

 level of the land or that of the ocean has undergone changes, speak of the "positive" {i.e., upward) and 

 " negative " {i.e., downward) movement of the shore-line. We have substituted the more familiar terms 

 "upM-ard"and "downward," but it must be borne in mind that if the land has risen, this corresponds 

 with an apparent downward movement of the shore-line, and vice versa. — Ed.] 



