Radio-activity and the Rocks

Abstract

IN the course of some observations which I have recently made with regard to the pleochroic halos sometimes seen round inclusions in various rock-forming minerals, certain points have suggested themselves as possibly of considerable significance. It may be premised that Prof. Joly's suggestion that the halos are due to the α rays emitted by radium appears fully borne out by their remarkable constancy in size and by the fact that they are invariably connected with minerals independently known to be strongly radio-active, that is, comparatively speaking. The only qualification that need be made respecting this view is with regard to the possibility of radio-active substances other than radium producing the observed effects.