CORAL REEFS OF THE PACIFIC. 320 



corals upon volcanic products, is an evident proof 

 that their formation was subsequent to the emission 

 of the lava upon which they had planted themselves 

 when it was sufficiently cool. But polyps live under 

 water. The lava therefore, in this instance, must 

 have been of submarine origin ; the ocean-bed thus 

 formed was long afterwards upheaved to the light of 

 day. 



By far the greater part of the surface of a group of 

 islands situated a little to the east of Java, is com- 

 posed of beds of coral, in all respects similar to those 

 which are still in formation, and which constitute 

 the well-known dangerous reefs of the Pacific. It 

 is obvious that, in this instance also, the coral pol} ])i 

 had taken up their abode on the cooled lava, ai.d 

 that the whole mass was afterwards elevated above 

 the ocean, as in the case of Mauritius. 



In the island of Pulo Nyas, to the westward of 

 Sumatra, beds of coral, similar to those of the neigh- 

 bouring seas, have been raised to a height of many 

 hundreds of yards. 



In the earthquake which, in 1820, destroyed a 

 part of Acapulco (as described in a previous chapter), 

 the level of the sea remained during two hours 

 about 30 feet below its ordinary level, in conse- 

 quence of the land having been raised to that 

 extent. On the other hand, we remark a permanent 



