Early work on chemical bonding in relation to solid state physics

A symposium on the beginnings of solid state physics, organized by Sir Nevill Mott, F. R. S., was held by the Royal Society from 30 April to 2 May 1979, and 26 papers contributed to this symposium were published in Proc. R. Soc. Lond . A 371, 1-177 (1980). One aspect of solid state physics, that dealing with the nature of the chemical bond in solids, was presented to only a quite limited extent. The present paper, which emphasizes my own early work in this field, has been written to supplement the symposium papers.