INTRODUCTION. ix 



this region ; but of these, the fringing and barrier-reefs are 

 more commonly distributed, whilst the atolls are compara- 

 tively few in number and of small size, A line of barrier- 

 reefs, probably not much under 60 miles in length and bear- 

 ing innumerable islets on its surface, fronts the east coasts of 

 the islands of New Georgia at a distance of from one to 

 three miles from the shore. Extensive reefs of tlie same 

 class, having a broad deep-water channel inside them, lie off 

 the large island of Isabel and off the south-coast of Choiseul. 

 Barrier-reefs, of smaller extent, also skirt the west end of 

 Guadalcanar and the southern end of Bougainville. I have 

 referred particularly to these reefs because at the time that 

 Mr. Darwin wrote his work on " Coral Reefs," fringing-reefs 

 were alone believed to exist in these islands. 



The larger islands of tlie Solomon Group are often separ- 

 ated from each other by depths of several hundred fathoms. 

 St. Christoval, for instance, is separated from the neighbour- 

 ing islands of Guadalcanar and Malaita by straits in which 

 casts of 200 fathoms fail to reach the bottom. On the 

 other hand, the same 100 fathom line includes both Bougain- 

 and Choiseul. Judging, however, from the soundings ob- 

 tained by Lieut.-Commander Oldham between the islands 

 lying off the north coast of St. Christoval, it would appear 

 probable that depths of 400 fathoms commonly occur be- 

 tween the islands of the Solomon Group. Although the 

 soundings hitherto made in this portion of the Western 

 Pacific go to show that this archipelago, together with New 

 Ireland and New Britain, are included within the same 1,000 

 fathom line, which extends as a loop from the adjacent 

 borders of New Guinea, we can scarcely urge this fact as 

 evidence of a former land connection, seeing that one of the 

 most interesting features in the geological history of this 

 region is that of the enormous elevation which these islands 

 have experienced in recent and probably sub-recent times. 

 Independently of the character of the deposits discovered 

 by me in the Solomon Islands, I arrived at the conclusion 

 that there had b.^en a recent upheaval of at least 1,500 feet. 

 The characters of some of the deposits, as examined by Dr. 

 Murray in the light of the "Challenger" soundings, however, 

 afford, indications of an upheaval of a far more exten- 

 sive nature. I am informed, in fact, by Mr. H. B. l^)rady, 

 that the foraminifera of some of the Treasurv Island 

 rocks indicate depths of probably from 1500 to 2000 

 fathoms. Geologists may look forward with the greatest 



