* Where living rocks. l. 90. The immense and dangerous rocks built by the swarms of coral insects which rise almost perpendicularly in the southern ocean like walls are described in Cook's voyages, a point of one of these rocks broke off and stuck in the hole which it had made in the bottom of one of his ships, which would otherwise have perished by the admission of water. The numerous lime-stone rocks which consist of a congeries of the cells of these animals and which constitute a great part of the solid earth shew their prodigious multiplication in all ages of the world. Specimens of these rocks are to be seen in the Lime-works at Linsel near Newport in Shropshire, in Coal-brook Dale, and in many parts of the Peak of Derbyshire. The insect has been well described by M. Peyssonnel, Ellis, and others. Phil. Trans. Vol. XLVII. L. LII, and LVII.
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