356 REMARKS AND OPINIONS. 



in other seas, and especially in the Atlantic Ocean, 

 of a volcanic nature. The Mariana islands form, 

 in the first province, a mountain chain, running 

 parallel with the PhiHp})ines, and which might be 

 compared with the Forelands that bound the ocean 

 basin ; it contains, like them, especially towards 

 the north, volcanoes that are still burning, whereas 

 the islands that lie separate, in the middle of the 

 basin, seem to be for the most part extinguished. 

 A volcano burns at Tofua, in the west of the 

 second province ; and Mouna Wororai, in Owhyee 

 of the Sandwich islands, discharged a stream of 

 lava by a lateral eruption, so late as the year 

 1801. In the Friendly and Marquesas islands 

 primitive kinds of rocks occur ; in Woahoo we 

 found only porphyry and almond-stone. 



The low islands, that is, the coral islands, and reefs 

 as they are called, present us with a quite peculiar 

 formation, which we had no want of favourable 

 opportunity to examine, and which we more par- 

 ticularly describe in our paper upon Radack, from 

 which our knowledge and observations- on this 

 subject were chiefly derived. 



These islands, and circular island-groups, are 

 table mountains, which rise perpendicularly fjom 

 the depths of the ocean, and near which the lead 

 finds no bottom. The surface of the table is below 

 water ; only a broad dam round the circumference 

 of it (the reef), reaches the surface at low water, 

 and bears on its ridge or back, the sand banks, 



14 



