48 CORAL FORMATIONS. 
an estimate. Adjacent to the larger islands, such as those of Vanua 
Levu and New Holland, the error might be of the opposite kind; for 
the slopes of the land are of a more complex or irregular character 
than on the smaller islands. In the latter they may be shown to 
belong generally to a single elevation of igneous origin, or.at the most 
to two or three combined; while in the former they may pertain to 
different ranges of hills or mountains. For correct results in any 
instance, the land and its declivities should be carefully studied before- 
hand, and the system in its inclinations determined by observation. 
With regard to Tahiti and Upolu, information bearing upon this point 
was obtained, and the above conclusions may be received with much 
confidence. Many of the Feejee reefs, on the same principle, cannot 
be less than 2000 feet in thickness. 
Such accumulations of calcareous rock may appear to be an in- 
credible work for the coral polyp, but only because we are not ac- 
customed to contemplate the results which may proceed from the 
smallest agencies long continued. ‘The operatives in the inorganic 
world are invisible molecules; and so among living organisms, it is 
the lowest grade, the minims of existence, that have accomplished 
the grandest results in the earth’s history. 
3. CORAL ISLANDS. 
a. Forms and general features of coral islands. 
A barrier reef, and a lagoon enclosed by it, are the prominent fea- 
tures of a coral island, though there are a few of small size in which 
the lagoon is wanting. In the larger islands, the waters within look 
like the ocean, and are similarly roughened by the wind, though not 
to the same extent. Standing on the north shore of the Raraka lagoon, 
(in the Paumotus,) the eye scanning over it descries nothing but blue 
waters. [ar in the distance, to the right or left, a few faint dots are 
distinguished ; these gradually enlarge into lines of palms and other 
verdure, which sweep around into distinct groves as they near the 
observer. At Dean’s Island, another of the Paumotus, and at many 
of the Carolines, the resemblance to the ocean is still more striking. 
The lagoon is in fact but a fragment of the ocean cut off by more or 
less perfect walls of coral reef-rock; aud the reef is here and there 
surmounted by verdure, forming a series of islets. 
In many of the smaller coral islands, the lagoon has lost its ocean 
