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XXX. — Observations on the Recent Calcareous Formations of the Solomon Group 

 made during 1882-84. By H. B. Guppy, M.B., F.G.S., Surgeon H.M.S. 

 "Lark." Communicated by John Murray, Esq. (Plates CXLIV., 

 CXLV.) 



(Read 15th June 1885.) 



Preliminary Eemarks. 



On account of the treacherous character of the natives of the Solomon 

 Group, no extensive geological observations have ever been made in these 

 islands since the period of their discovery by the Spaniards three centuries 

 -ago. For this reason my excursions in these regions were not free from 

 personal risks ; in many places they were considerably curtailed, and in some 

 places they had to be abandoned altogether. Fortunately, however, I was 

 able to make a detailed examination of several of the smaller islands, the 

 natives of which had been first conciliated by the kit dly tact of Lieut.-Com- 

 mander C. F. Oldham, to whom I am indebted tor much assistance in 

 my pursuits. But from the circumstances in which I was placed, both on 

 board and on shore, it was necessary, in order to accomplish much, to dare 

 a little. 



This archipelago includes seven or eight large islands, some of which are 

 from 70 to 80 miles in length, and the highest from 8000 to 10,000 feet in 

 height. Besides these, there are a great number of smaller islands and islets, 

 some of volcanic and others of recent calcareous formations. Restricting my 

 remarks to those islands which are wholly or in part composed of these cal- 

 careous rocks, I may observe that, although only able to become acquainted with 

 a small portion of the Solomon Group, the islands which I examined represent 

 the different types of islands that there exist. The larger islands, composed in 

 mass of ancient volcanic rocks flanked on the lower slopes of their sea-borders by 

 more recent calcareous formations, are represented by St Christoval. Among 

 the smaller islands, the following types occur : — in the first place, there are 

 those which are made up in bulk of a soft Foraminiferous deposit encrusted 

 only by coral limestone, as in the island of Ugi. Then there are those which 

 are composed in great part of these soft deposits and coral limestones, but 

 partly also of volcanic rocks, as in the Shortland Islands. In the next place, 

 there are islands, usually small and of no great height, which are entirely of 

 •coral rock, as in the case of Stirling Island. Santa Anna represents probably 

 an uncommon type of island, being an upraised atoll with its foundations 

 vol. xxxii. part hi. 4 x 



