The materials surveyed include porcelain, modified porcelains, cordierite ceramics, normal and low-loss steatite, alumina and zircon porcelains, sintered alumina and other oxides, the semi-conducting ceramics and the dielectric materials based on titania and other oxides.Ranges of composition and/or the general nature of the materials used, methods of forming insulators or capacitors from such mixes, limitations of manufacturing methods and the limits of firing temperatureare detailed.The relationship between the type and amount of glassy phase in the insulating ceramics and their physical properties (particularly their electrical properties) is discussed. The limitations or outstanding qualities of each material are considered.The theory of semi-conductors, the principles underlying their production and certain of their important uses are surveyed.A broad outline of the dielectric ceramics is given, and the most important properties of several of the best known groups of ceramic materials are tabulated.