On the Nature of the Earth's Core

In a previous paper (M. N., 108, 406, 1948) the author has suggested that the density jump at the boundary of the Earth's core is due to a phase transition under pressure, and not to the appearance of a new material such as iron. A metallic type of structure was proposed for the material in the core. In the present paper the transition to the metallic phase is explained in greater detail. Seismological data are used to prove that the core cannot be composed of either iron or an alloy of nickel and iron. It is shown how the theory removes certain difficulties arising from the hypothesis of an iron core, and how it can account for features not hitherto explained.