HOPKINS.—THE TELEPHONE: Outlines of the Development of Transmitters and Receivers. By William J. Hopkins, Professor of Physics in the Drexel Institute, Philadelphia; Author of 'Telephone Lines and their Properties,' etc. With 7 Full-page Illustrations and 39 Diagrams. Crown 8vo., 3s. 6d.

PREECE AND SIVEWRIGHT.—TELEGRAPHY. By Sir W. H. Preece, K.C.B., F.R.S., V.P.Inst., C.E., etc., Engineer-in-Chief and Electrician, Post Office Telegraphs; and Sir J. Sivewright, K.C.M.G., General Manager, South African Telegraphs. With 267 Illustrations. Fcp. 8vo., 6s.