2c8 CORALS AND CORAL LSLANDS. 



most they can do is to produce a thin layer of brackish water 

 over the sea within the channels. 



e. The following figure of the harbour of Falifa, Upolu, 

 represents another coral harbour, as surveyed by Lieutenant 

 Emmons. At its head there is a stream twenty-five or thirty 

 yards wide and three feet deep. Notwithstanding the unusual 

 size of the river, the coral reef lies near its mouth, and pro- 

 jects some distance in front of it. Its surface is dead, but 

 corals are growing upon its outer slope. 



/. The harbour of Rewa, in the Feejees, may be again 

 alluded to. The waters received by the bay amount to at least 

 500,000 cubic feet a minute. Yet there is an extensive reef 

 inclosing the bay, lying but three miles from the shores, and 

 with only two narrow openings for ships. 

 ^.^ The case is so remarkable that we can 



hardly account for the facts without 

 supposing the river's mouth to have 

 neared the reef by depositions of de- 

 tritus since the inner parts of the reef 

 were formed ; and there is some evi- 

 dence that this was the case, though 

 HARBOUR OF FALIFA. ^o what distancc wc cannot definitely 



state. With this admission, the facts 

 may still surprise us ; yet they are explained on the principle 

 that fresh water does not sink in the ocean, but is super- 

 ficial, and runs on in a distinct channel ; its effect is almost 

 wholly through hydrostatic pressure, increasing the force of 

 the underwater currents, and through their depositions of 

 detritus. Besides these instances, there are many others 

 in the Feejees, as will be observed on the chart at the 

 end of this volume. Mokungai has a large harbour, with- 

 out a stream of fresh water ; — so also Vakea and Direction 

 Island. 



The instances brought forward are a fair example of what is 

 to be found throughout coral seas ; and they establish, beyond 

 dispute, that while much in harbour-making should be attri- 

 buted to the transported sand or earth of marine and fresh- 



