As the discussion of this subject is necessarily brief, no attempt will be made to review the classification of organic and chemical deposits advanced by Murray and Renard in the Challenger reports, and I will immediately pass to the consideration of some of the results obtained from researches made during the past ten years. My remarks will be for the most part confined to the discussion of deposits formed in water less than 100 fathoms deep, because recent investigation has been chiefly directed to these and because the geologist usually encounters relatively shallowwater sediments in his field-work. However, in places accumulations of pelagic foraminifera, of radiolarian earths, and of certain particular kinds of manganese nodules above present sealevel indicate that some ancient deep-sea deposits have been elevated from several thousand feet below the surface of the ocean and now form parts of dry-land areas; but the areas occupied by such . . .

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