This volume contains three articles reviewing a broad spectrum of topics.
each of them having considerable importance in the development of
contemporary condensed matter science. The first is devoted to a generally
accessible account of the present state of the theory of the transition
temperature, T,, of superconductors. Philip B. Allen and BoZidar MitroviC,
its authors, note that the prediction of T, remains largely an unsolved
problem. Their detailed account of the Migdal-Eliashberg theory
is to be welcomed, as is their critical discussion of the more popular approximate
T, equations. In the second article, J. C. Phillips presents a
polycluster model, analogous to his earlier model for chalcogenide
glasses, for the structure of tetrahedrally coordinated oxide glasses. He
critically examines the vibrational spectra of oxide glasses and concludes
that these spectra are consistent with his model but inexplicable by the
continuous random network models. Though there may be considerable
disagreement with his analyses and conclusions, Phillips raises and treats
important issues in the spectroscopy of glasses in a stimulating and provocative
manner