Actions of Volcanoes. 287 
banks, add to the heap of calcareous matter, without being 
properly concerned in the erection of the structures. Fre- 
quently also, holothuriz, and other soft worms, are found in 
the reefs, and haye by careless observers been mistaken for the 
coral animais. 
To describe, or even to enumerate, the different islands and 
rocks which owe their existence to the labours of the coral 
worms, would be to enter on a wide field of geography. The 
narratives of many navigators, such as Cook, Kotzebue, Flin- 
ders, and others, may be consulted by the reader who is 
desirous of more minute information on this subject; as it 
would exceed the necessary limits of this communication, to 
go into itinany detail. A very brief notice of a few remarkable 
examples is alone admissible. 
Nearly all the islands that lie on the south of the equator, 
between New Holland and the western coast of America, derive 
either the whole or a great part of their structure from these 
animals. The whole of that sea, and indeed of some others, 
abounds in coral rocks and reefs, which are in a state of daily 
and rapid increase, and are probably destined at some future 
day to elevate themselves to the level of the water; to become 
first the seats of vegetation ; and, in process of time, the habita- 
tions of man; and perhaps ultimately to produce scarcely less 
than a continent in this extensive ocean. 
Among other places, these reefs abound particularly between 
New Holland, New Caledonia, and New Guinea; and they are 
well known to exist in great abundance in the seas of the Indian 
Archipelago, as at Chagos, Juan de Nova, Cosmoledo, Assump- 
tion, Cocos, Amirante, and the Laccadive and Maldive islands. 
They are numerous also, in the east side of the gulf of Florida ; 
and it is well known that they form a daily increasing impedi- 
ment to the navigation of the Red Sea. 
The extent of these reefs and islands is an object of great 
curiosity and surprise when we consider the apparent feebleness 
of the means by which they are produced, and the minuteness 
of the agents. An instance or two of this must suffice here. 
Tongataboo, described by Cook under this misapprehended 
