EVIDENCES OF nPHEATAL. 259 



even under the assumption of the subsidence, they still could 

 find only a forced explanation by the help of some other agency. 



To guide us in this enquiry, it will be well to collect and 

 coUate the facts which may directly prove a recent upheaval 

 in the Pelew Archipelago. 



Evidences of recent upheaval in the Pelew Islands. — I 

 have already pointed out that the huge blocks of coral lying on 

 the outer margin of the western reef, in my opinion, can only be 

 regarded as evidence of a recent upheaval. Since, however, this 

 may be disputed on familiar, though not perhaps very strong, 

 grounds, I will not attribute to it any great importance. 



The following stronger grounds, on the other hand, can 

 hardly be doubted. Most of the islands are high ; to the south 

 they rise to 200 or even 300 feet (at most), while on Babel- 

 thuap there are hills said to be 2,000 feet high. Their structure 

 sufficiently proves that they owe their origin to a volcanic 

 upheaval in quite recent times. 



Between the islands of the north and south a marked con- 

 trast is visible ; while the former are almost exclusively volcanic, 

 by far the greater number of the latter are formed of upheaved 

 and partly metamorphic coralline limestone. This contrast is 

 so sharply defined that even the natives have distinctive names 

 to express the difference ; the islands formed of coralline lime- 

 stone they call ' Kokeal,' the volcanic islands ' Eoyoss.' 



A recent work by Dr. Wiechmann treats of the geological 

 structure of the northern islands. This geologist ""' has come to 

 the conclusion, which is confirmed by Herr Giimbel (inspector 

 of mines), who examined my collection of minerals, that the 

 eruptive rock is augitic Andesite. "Wiechmann also came to 

 the conclusion — without having been to the islands, and simply 

 from studying the minerals collected there by Dr. Kubary — that 

 the eruption must have been submarine — a view I had long 

 since taken, from a study of the islands themselves. He also 

 approximately determined the period of the eruption ; he is of 

 opinion that the upheaval must have taken place during the 

 latest period of the tertiary epoch. A remarkable feature, not 

 mentioned by Wiechmann, is the distribution of the various 

 volcanic rocks in Babelthuap. The solid eruptive rock, Andesite 



