P. A. Paly — Problems of the Pacific Islands. 161 



fall under three heads : first, the distribution and origin of the 

 islands containing rocks of the continental type : secondly, the 

 nature of volcanic action in general : and lastly, the origin of 

 the limestone formations, including coral reefs. Each of these 

 topics has long been the object of research, but for none of 

 them is there uniformity in expert opinion. 



Islands Showing Outcrops of Continental Rocks. 



The vast Eastern Archipelago, extending from Sumatra and 

 the Philippines to New Guinea, has been formed by compli- 

 cated movements of the earth's crust. In large part the 

 included seas — the Banda, Java, Celebes, Mindoro, and China 

 seas — seem to be due to the local submergence of crustal 

 blocks which were once parts of a continental area. The 

 satellitic islands close to New Guinea have been separated 

 from that large island by subsidence. Evidence of such 

 founderings are found in the detailed structures of the islands, 

 as well as in the mineralogical content or petrography of the 

 rocks. Crystalline schists, granitic masses, and old, deformed 

 sediments — staple rocks of continental mountain ranges — 

 constitute the great bulk of the Eastern Archipelago. How 

 far do similar formations characterize Oceania proper ? This is 

 an old question, still without a satisfactory answer. Archi- 

 pelagoes one thousand miles offshore from New Guinea or 

 Australia are known to contain continental types of rock. 

 In Oceania, outside of the Eastern Archipelago just de- 

 scribed, continental types of rock appear in about thirty 

 different islands. Most of these islands are located in the 

 following groups : Bismarck, Bonin, Caroline, Chatham, Fiji, 

 Kermadec, New Caledonia, Pelew, and Solomon. Deformed 

 Miocene limestone is reported from Espiritu Santo island of 

 the New Hebrides, and gneiss (?) from Malekula of the same 

 group. Ellis described the occurrence of " quartz-feldspar 

 rock" in Borabora of the Society group, but the report needs 

 confirmation. Quartzose rocks are described from Norfolk, 

 Bounty, Campbell, and The Snares — all isolated islands. 

 Commander Thomson stated that he found granite and slate in 

 Easter island. 



Every one of these composite islands needs thorough study 

 by able geologists, who are also trained in petrography. The 

 Carolines, the Santa Cruz group, and the Tonga group are 

 specially critical and deserve immediate attention. The reports 

 of granitic rocks in Borabora and in Easter island should be 

 checked by field work. Systematic investigation ought to 

 replace the haphazard mode of discovery that has commonly 

 ruled in regions of assumed continental fragmentation. The 



