. The depths of the ocean; a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic. Oceanography. iv DEPTHS AND DEPOSITS OF THE OCEAN 159 Associated with the glauconite in certain localities, more Phosphatic especially off the Cape of Good Hope and off the Atlantic coast concretlons- of the United States, irregular concretions, largely made up of phosphate of lime, have been dredged. The concretions vary greatly in size and form, with a greenish or brownish glazed external surface, and are ma
. The depths of the ocean; a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic. Oceanography. iv DEPTHS AND DEPOSITS OF THE OCEAN 159 Associated with the glauconite in certain localities, more Phosphatic especially off the Cape of Good Hope and off the Atlantic coast concretlons- of the United States, irregular concretions, largely made up of phosphate of lime, have been dredged. The concretions vary greatly in size and form, with a greenish or brownish glazed external surface, and are made up of heterogeneous fragments derived from the deposit containing the concretions (grains of glauconite and other minerals or remains of organisms), cemented by phosphatic material, which consti- tutes the principal part of the concre- tions. When the cemented particles are purely mineral, the phosphatic matter acts simply as a cement, but when the remains of calcareous organ- isms are included in the concretions, the phosphatic material plays a more important part, filling the internal chambers, and often the calcium car- bonate of the shell is pseudomor- phosed into calcium phosphate. When the filling up of a foraminifer, for example, and the pseudomorphism of its shell, are complete, the phosphate, attracted around this little centre con- tinues to be added at the surface, and thus a phosphatic granule is formed, the external appearance of which no longer recalls that of the organism around which the phosphate has grouped itself. These phosphatic con- cretions occur chiefly along coasts bathed by waters subject at times to great and rapid changes of tempera- ture, which cause the destruction on a large scale of marine life, the decomposition of the organic remains, sometimes thickly covering the sea-floor in such locali- ties, giving rise to the phosphate of lime to be permanently fixed in the phosphatic nodules. Just as the silicate glauconite occurs in the terrigenous P
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