118 CORAL FORMATIONS. 
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 detritus since the inner parts 
of the reef were formed ; and there is some evidence that this was the 
case, though to what distance, we 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 
superficial, and runs on in a distinct channel; its effect is almost 
wholly through hydrostatic pressure, and detritus depositions. Besides 
these instances, there are many others in the Feejees, as will be ob- 
served on the Expedition charts. Mokungai has a large harbour, 
without 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 attributed to the transported 
sand or earth of marine and fresh-water currents, in preventing the 
growth of coral, but little is due to the freshening influence of the 
streams of the islands. 
But while observing that currents have so decided an influence on 
the condition of harbours, we should remember another prevalent 
cause, already remarked upon, and perhaps more wide in its effects 
than those just considered. I refer to the features of the supporting 
land, or the character of soundings off a coast. 
We need not repeat here what has already 
been dwelt upon, showing that many of the 
(( a interruptions of reefs have thus arisen. The 
\\ wide break off Matavai may be of this kind. 
\\ The widening of the inner channel at Papieti, 
A forming a space for a harbour, may be another 
| example of it; for the reef here is removed to 
\ a greater distance from the shores, as if be- 
(/ cause the waters shallowed more gradually 
y \( outward off this part of the coast. The same 
wid i \\ cause—the depth of soundings—has more or 
7 Seon ed on less influence about all reefs in determining 
NM, a SSN their configuration and the outlines of har- 
cae ee bours. A remarkable instance of the latter is 
exemplified in the annexed chart of Whippey 
Harbour, Viti Lebu, reduced from the chart 
of the Expedition to the scale of half an inch to the mile. 
WHIPPEY HARBOUR, VITI LEBU. 
