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 hear 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 sec 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