Abstract
III.
AMONG the mineral constituents of meteorites the unstable sulphides, it is hardly necessary to observe, could with difficulty be conceived as continuing permanently undecomposed, or as being even formed under the ordinary conditions of rock formation on our globe; and the same remark may be extended, though with some limitation, to the metallic iron that is so characteristic and ubiquitous a constituent of almost every, if, indeed, not (as maintained by Dr. Lawrence Smith) of every meteorite. On the other hand, it is to be remembered that the rocks that we are acquainted with oh our globe are only those composing its outer crust; rocks which represent the results of the corrosive action of the atmospheric agencies, oxygen, carbonic acid, and water, and their counterpart, the ocean, on whatever material the consolidated surface of our planet offered for their action. The endless cycle of mechanical and chemical disintegration, decomposition, and reconstruction would be limited to a shallow shell, and even the fresh matter forced out to the surface in volcanoes, through the contraction of the cooling globe, would consist in all likelihood only of the lower-lying layers of an already to a certain degree metamorphosed material. Whether the inner core of this planet is still in the meteoric condition—that is to say, still may contain such minerals as native iron, associated with nickel, not to say magnesium or calcium sulphides, is a question not to be lost sight of in explaining the high specific gravity of our globe as compared with that of the rocks that form its crust.
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MASKELYNE, N. Some Lecture Notes on Meteorites † . Nature 12, 520–523 (1875). https://doi.org/10.1038/012520a0
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DOI: https://doi.org/10.1038/012520a0