Thermodynamic evidence supports the experimental suggestion of a previous paper that at ordinary temperatures sufficiently high pressures are capable of breaking down the quantum structure of atoms, reducing matter to an electrical gas of electrons and protons. We may, therefore look for atomic dissociation under two sorts of conditions: high temperatures and comparatively low pressures, such as we have in the stellar atmospheres, and high pressures and comparatively low temperatures, which we may surmize we have in the interiors of stars, possibly in stars like the sun, and almost certainly in stars of the enormous density of the dark Sirius type. The possibility of two sorts of dissociation, together with the more rapid increase of pressure than density when the diameter of a star is reduced, offers the possibility of a critical condition determining whether a star is of the dark Sirius type or not.

• Received 4 October 1926

DOI:https://doi.org/10.1103/PhysRev.29.188