ON THE FORMATION OF CORAL ISLANDS. 335 



level, or producing, in the course of a few days or 

 weeks, what might have required the labour of cen- 

 turies. Geology therefore finds two distinct sources 

 of interest in the study of these islands. If the proofs 

 which they afford of elevating forces, connected with 

 volcanoes and acting beneath the surface of the earth, 

 are valuable, the simple history of the Coral islands, 

 independently of this interference, is scarcely less 

 worthy of notice. It cannot at least be less interest- 

 ing to study the formation of immense masses of 

 calcareous rock by living animals, than by the accu- 

 mulation of the spoils of dead ones. It is, in many 

 respects, even more so ; not less from the illustration 

 which it affords relating to the antient calcareous rocks 

 of the globe, than from the tangible nature of what, in 

 these analogous cases, is only matter of inference, 

 and from the comparative feebleness of the agents 

 concerned in the production of these important 

 effects. 



With respect to all the organic fossils, their chief 

 interest is derived from the relations which they bear 

 to the existing species, and from the effects which 

 they have on the structure of the earth. We are sur- 

 prised at the immense accumulation of the shells 

 which form the secondary calcareous strata, and with 

 the enormous additions which the earth has received 

 from the labours of animals, generating mountains 

 out of the habitations which they had formed for 

 themselves. Yet these results rarely strike us; as 

 the very fact indeed has been doubted or denied. It 

 can at least be denied no longer; for it is before us, 

 if under another form. They do not strike us, 

 because we see these rocks long deserted by the sea, 

 associated with others, and without traces of a living 

 origin except to the eye of a geologist. We contemplate 



