STRATIFIED ROCKS OF ORGANIC ORIGIN--ILLUSTRATIONS FROM
ANIMAL LIFE.
Nature of Organic Rocks--Carbonate of Lime extracted from the
Sea by the Intervention of minute Animalcules--Chalk Rock--its
vast Extent--supposed to be of Organic Origin--A Stratum
of the same kind now growing up on the Floor of the Atlantic
Ocean--Coral Reefs and Islands--their general Appearance--their
Geographical Distribution--their Organic Origin--Structure
of the Zoophyte--Various Illustrations--Agency of the
Zoophyte in the Construction of Coral Rock--How the sunken
Reef is converted into an Island--and peopled with Plants and
Animals--Difficulty proposed and considered--Hypothesis of
Mr. Darwin--Coral Limestone in the solid Crust of the Earth, 118