556 H. B. GUPPY ON THE EECENT 



exposed about a foot at high tide, which fringes the shores of the harbour. 

 Allowing for the rise and fall of the tide in this region, I estimate this most 

 recent elevation at not less than 5 feet. It is of importance to note, as indicat- 

 ing the coincidences in the elevatory movements in this region of the Pacific, 

 that in the islands of Ugi and Santa Anna, which lie over 400 miles distant at 

 the opposite end of the Solomon group, there have been modern upheavals of 

 the same limited extent (vide page 549). 



The first page in the history of Treasury Island, as an island, began when 

 the submarine volcanic peak had been brought up to within the depths at 

 which reef corals thrive, by the constant piling up of sediment assisted by the 

 upheaving movements. During these movements, the barrier-reef, now repre- 

 sented by Stirling Island, was formed by the outward growth of the reef. Coral 

 reefs, however, have played but a secondary part in the actual building up of 

 the island of Treasury as a whole. 



The Island of Santa Anna. 



The small island of Santa Anna, at the eastern extremity of the Solomon 

 group, presents an example of a raised atoll. Having a nearly circular form 

 with a length and breadth of 2^ and 2 miles respectively, this island consists 

 of a central basin surrounded by an elevated rim which is wanting at the 

 middle of the west or lee side. The bottom of the basin, which extends 

 downwards to about 100 feet below the sea-level, is occupied by two fresh- 

 water lakes (vide Plan and Section of this island Plate CXLIV. figs. 5 and 6). 



The elevated rim has a broad level summit, varying between a quarter and 

 one-third of a mile in width, and elevated 200 feet above the sea, except on 

 the south and south-west sides of the island, where it has only half this 

 elevation. From the middle of this raised margin, on the east or weather side, 

 there rises an elevated mass to a height of about 470 feet above the sea, which 

 gives to the island, when viewed either from the eastward or the westward, 

 a profile resembling a broad-brimmed low-crowned hat. On the flat summit 

 of this elevated mass, there is a basin-shaped hollow between 100 and 150 

 yards across and 35 or 40 feet in depth (vide Section Plate CXLIV. fig. 5). 



The central depression may be described as a somewhat symmetrically shaped 

 hollow, the bottom of which, lying about 100 feet below the sea-level, is 

 occupied by two fresh-water lakes, the waters of which are not affected by the 

 rise and fall of the tide, although lying at or about the mean tide-level. The 

 interior of this island is, in fact, a closed basin, which is completely cut off from 

 the sea ; and it may be aptly compared to a bowl of fresh water floating on sea 

 water. But so low is the barrier that shuts out the waters of the ocean — a 

 barrier which is composed for the most part of coral detritus, calcareous sand, 

 and shells — that a depression of about 25 feet would admit the sea into the 



