m 
VOYAGE TO THE 
Cook on his second voyage and visited several of the coral islands, and 
was founded, no doubt, upon the experience which he had derived 
upon that voyage. But considering the extent of some of these islands, 
it is evident that if this be their form, the lithophy tes, the animals which 
construct them, must commence their operations at very great depths, 
a fact which is doubted by naturalists. The general opinion now is, 
that they have their foundations upon submarine mountains, or upon 
extinguished volcanoes, which are not more than four or five hundred 
feet immersed in the ocean ; and that their shape depends upon the figure 
of the base whence they spring. It would be immaterial which of these 
theories were correct, were it not that in the latter instance the lagoon 
that is formed in all the islands of this description might be occasioned 
by the shape of the crater alone, whereas, in the former, it must 
result from the propensity of the coral animals, and this, if true, forms 
a remarkable and interesting feature in their natural history. Mr- 
Forster* thought this peculiarity might arise from the instinct of the 
animalcules forming the reefs, which from a desire to shelter their 
habitation from the impetuosity of the winds, and the power and rage 
of the ocean, endeavoured to construct a ledge, within which was a 
lagoon entirely screened against the power of the elements, and where 
a calm and sheltered place was by these means afforded to the animals 
in the centre of the island. 
Another reason why the consideration of the nature of their founda- 
tion is not immaterial is, that if the form of the islands arose from the 
peculiar shape of the craters, and it be admitted that the lithophy tes are 
unable to exist at greater depths than those above-mentioned, we shall 
have examples of craters of considerably larger dimensions, and more 
complete in their outline, than any that are known upon the land, which, 
if true, is a curious fact. Until the voyage of the Blossom, it was not 
generally known that the lagoons in these islands were of such depths, or 
that the wall of coral which encircles them was so narrow and perfect, as in 
almost every instance it has been found ; nor that the islands were of such 
dimensions, as they were designated groups, or chains of islands, in conse- 
* Forster’s Observations, 4to, page 150. 
