823 



the rate of movement and the continual morphological change of 

 the geanticline, which have often been so iiitluential in the develop- 

 ment of the leefcaps. In the case illustrated in Fig. 1 the reef, 

 originally formed on the south coast lies', in the next stage, on the 

 northern slope of the enlarged island, so that it is hardly permissible 

 to speak of a more marked upheaval of the south coast. It may 

 even be conceived that also B is situated north of the coastline of 

 the new island, so that in that case the original island is covered 

 entirely by tlie sea, while a new island has emerged farther soutli. 



Elevated reefs of the Sermata group. 



It has been said above that the reefs, formed at a certain epoch 

 in the history of mountain building along the coasts of a geanticline, 

 may perform various movements in the subsequent stages. The rate 

 as well as the direction of the movement sometimes differ conside- 

 rably at a comparatively short distance. This is clearly illustrated 

 by the movements of the reefs in the period of development of the 

 geanticline, in which only its highest parts emerge from the sea as 

 a group of smaller islands. We shall dwell more particularly on the 

 movements of the islands of Luang, Moa, Kisser, and Letti. 



According to my observations in Luang this island, built up 

 entirely of permiau rocks, is together with two islets near the 

 South-eastern extremity, fringed by a very broad reef, extending far in 

 the direction of Sermata and also far to the West. Green islets far from 

 the north coast and barren, dry portions far from the south coast, 

 mark the limits in northern 'and southern direction; beyond them 

 the sea floor declines rapidly. At ebb-tide part of the reef gets dry. 

 Luang as well as the two islets close to it, to the South-east, rise up 

 steeply from this broad reef; no trace of elevated reefs was detected, 

 so that proofs of a period of upheaval are lacking. The island of 

 Luang and the two islets near it, impress us as having originally 

 formed one coulintious whole, and as having been separated by a 

 positive movement, which may also account for the formation of 

 the broad encircling reef, which is bordered hei'e and there by green 

 islets. Post-glacial upheaval of the seasiirface renders the subsidence 

 of the land only apparent. 



Now let us look at the island of Moa, more particularly its 

 eastern half. For the most part the island consists of a low, very 

 broad plateau of coral limestone, which rises scarcely more than 

 10 — 20 m. above the sea, and from which in the eastern part rises 



