172 CORAL AND ATOLLS 



many large blocks of coral in the atoll, which when returned to 

 the sea were found to float buoyantly.* These coral masses 

 are not at all uncommon on the seaward beaches, they are 

 mostly sea- worn and ancient, and, so far as I observed, all 

 belonged to one species of massive Astrcea with very large 

 zooids. The skeleton floats by reason of the many spaces 

 securely walled off by the septa. The most interesting thing 

 about these stranded lumps of coral is the fact that no species 

 at all like them is to be found living in the atoll. In the 

 ocean between the atoll and Java Heads, and in the Banka 

 Straits, I have seen these floating masses pass by the ship in 

 company with the smaller lumps of pumice which seem to be 

 for ever floating in the ocean in this part of the world. 



Some of the masses are very large ; one that I found on 

 the seaward beach of Pulu Tikus was nearly three feet in 

 diameter ; it was a difiicult undertaking to roll the great mass 

 back into the sea, and yet, when at length it reached the 

 water it floated readily. It had been long in its position at 

 the top of the beach, and it must have been a time of severe 

 storm that tossed it beyond the reach of the normal waves ; 

 for though it was left floating, no sea at that season was powerful 

 enough to heave it back again, and, after bobbing along the 

 shore of the island for many days, it was lost sight of. Por- 

 tions of this boulder would not float in fresh water, but this is 

 not invariably the case, and some floating boulders are freely 

 buoyant in fresh as well as salt water. 



(B) The Beaches of the Lagoon Shore. 



In contrast to the surf-beaten, rock-bound shore which 

 stretches along the ocean side of the islands is the calm sandy 

 beach — a place of lapping waves and gentle slopes — by which 

 the island dry land falls to the lagoon. The lagoon beach is 

 typically composed of sand of a peculiar whiteness which the 

 sunshine makes dazzling, and which is entirely composed of fine 

 particles of coral, mixed only with fragments of broken shells. 



- Scot. Geog. Maga., vol. v. No. 6, p. 287. 



