CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 569 



coral, Serpula tubes, Echinoderm fragments, Alcyonium spicules, and Foramini- 

 fera, as Globigerina, Polytrema, Rotalia, and Nummulina. 

 Residue (5 -81) of a light brown colour, consists of — 



(a) Minerals (2 -00), m. di. 01 mm. ; felspar, augite, hornblende, magnetite, 



and a few glassy fragments. 

 (6) Siliceous Organisms (l - 00) ; a few fragmentary sponge spicules, 

 (c) Fine Washings (2 -81), consisting of a flocculent substance. 

 Sections of this rock show specimens of all the organisms mentioned above, 

 together with calcareous Algse and Carpenteria. 



in concluding these observations on this locality, I may remark on the 

 probable geological character of the elevated interior of this portion of Choiseul 

 Island. Judging from my partial examination of the lower slopes, and from 

 the significant profile of the high land behind, I think it probable that the 

 western portion of this large island will be found, on examination, to exhibit the 

 same geological structure as that which characterises the islands of Treasury, 

 Ugi, and other islands in the Solomon group. 



St Christoval. 



The large island of St Christoval, which is rather over 70 miles in length 

 and about 4100 feet in elevation, may be taken as probably representative, 

 respecting its raised calcareous formations, of the larger islands of the Solomon 

 group. My examination of the island was considerably curtailed on account 

 of the uncertain disposition of the natives. I was able, however, to obtain a 

 general acquaintance with the north coast and its vicinity, together with such 

 knowledge of the interior of the island as a traverse across its breadth from 

 Wano to Makira and various ascents, never exceeding 1400 feet, could afford me. 



The north coast is skirted by a margin of low-lying land of varying breadth, 

 which in its turn is fringed by shore-reefs along a large portion of its extent. 

 This low-lying margin is either of calcareous sand, shells, and coral detritus, 

 imperfectly mixed with humus, when it is raised from 2 to 4 feet above 

 the sea ; or it is of coral rock elevated 5 or 6 feet at the sea-coast, and rising 

 to some 15 or 20 feet as one proceeds inland. 



The general character of the mountainous interior is that of a parallel series 

 of long level-topped and gently rounded ridges, separated by deep valleys from 

 each other, and composed, as far as my limited field of observation enables me 

 to judge, of ancient volcanic rocks. From the elevated interior several lofty 

 spurs descend with a gentle slope and even profile to the north coast, where 

 they protrude as bold headlands that often retain an elevation of 800 or 

 1000 feet. My observations have shown that the masses of these headlands 

 are of old basic rocks ; whilst more recent calcareous formations encrust their 



VOL. XXXII. PART III. 5 A 



