New theory on the earth's interior

ABSTRACT _Sky and Telescope_ of February contains a brief account ofthe theory of R. B. Borcherds which he advocated m his address as retiring chairman of the Cape Centre of the Astronomical

Society of South Africa. This theory suggests that the characteristics of tne earth's interior can be described on the basis of variations in condition rather than composition.

Assuming a temperature-gradient of one degree for every 90 ft. of depth, he finds that the observed discontinuities in the transmission of earthquake waves at depths of 7½ , 23 and 38 miles

can be attributed to changes of state due to high temperature and pressure. He describes a transitional region between 750 and 1,800 miles within which depths the temperature and pressure

are estimated to increase respectively from 44,000° to 105,000° C., and from 5,150,000 Ib. to 12,300,000 Ib. per square inch. The pressure at the centre of the earth is calculated at 50

million pounds per square inch, and in such circumstances anounce of hydrogen would be compressed into 0-001 to 0-003 of a cubic foot. If 100,000° is above the critical temperature for any

of the known elements, no pressure applied to these substances at this temperature would cause them to liquefy or solidify; hence he considers that the earth's centre is gaseous,

although highly compressed. The gas would be ionized and compounds would produce much higher densities than the known average of 5-52 for the earth. He thinks that iron would lose its

magnetic properties under the intense heat at the earth's centre, so the old iron-nickel theory of the earth's core, developed to explain the earth's magnetic properties,

cannot be sustained, and in any event is unnecessary if rotating bodies develop magnetism, as has been recently found for stars. Access through your institution Buy or subscribe This is a

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ARTICLE CITE THIS ARTICLE New Theory on the Earth's Interior. _Nature_ 164, 344 (1949). https://doi.org/10.1038/164344a0 Download citation * Issue Date: 27 August 1949 * DOI:

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