Page:Popular Science Monthly Volume 43.djvu/728

710 conduits are considered. Long-distance lines, the various kinds of wire suitable for telephone use, insulators, and the exchange system are among the subjects treated of in the part of the book devoted to the mechanical construction of telephone lines. A chapter upon the propagation of energy, in which a brief account is given of the modern view of electric currents, precedes the consideration of the electrical properties of the telephone line. Among the subjects discussed in this portion of the work are self-induction, interference from outside sources—such as air and earth currents—telegraphic induction and induction from electric lighting and railway circuits, properties of metallic circuits and of cables. The work is written for the practical telephone constructor and for students, and will doubtless prove a valuable work of reference.

little manual is addressed to those who have the care of dynamos, and is clearly and directly written and free from all technicalities. Instructions are given as to properly setting the machine so as to avoid vibration, and the different parts—the field magnets, armature, and commutator—are briefly described, and instruction given for their proper care. Simple methods of determining and locating leaks are also given. The book closes with a list of the chief electrical terms, and is provided with an index.

authors of this essay state its purpose in the preface as follows:

"To know somewhat of the application of this great force, which man has discovered and called electricity, these pages are written. They are free of all technical terms. Simplicity has been the constant aim. The student's text-book on electricity has been written. The public's book has not been written. And, as we are taught to know ourselves, so should we know the forces that surround us. Especially so if we use these forces. Every subscriber of the telephone should know the rudiments of its action. This is why this book is put forward. It is intended as a primer in telephonic and other kindred instruction. . . ."

This purpose of the authors is laudable enough, and, if it had been adhered to, they might possibly have produced a useful book. Their real aim seems, however, to have been to give an exhibition of what they probably regard as fine writing, using the telephone as an excuse for their literary effort. The book is written throughout in the most approved V style of sophomoric composition, and contains very little real information about the telephone. The reader who had no previous knowledge of the subject would have a hard time indeed in trying to get any clear ideas of the Blake transmitter or induction from the description of the authors. The book has, however, one great merit. It is short.

volume of lectures and addresses before the Brooklyn Ethical Society is devoted especially to subjects of current political discussion, such as the tariff, the monetary question, the negro problem, the government of cities, and kindred subjects. To those who are familiar with the discussions before the society, or who have become acquainted with the character of the work from its previous publications, no word of commendation of the quality of these papers is necessary. The addresses are thoughtful and serious discussions of current political and economic questions, and can not fail to be welcomed by all who take an intelligent interest in public affairs. It would be impracticable to attempt to give here either a résumé or criticism of the dozen and a half addresses which compose the volume, though some features of interest may be briefly indicated. The volume was published last year, previous to the presidential election, and the addresses were selected chiefly with reference to the questions before the country during the campaign. We have therefore a discussion of the tariff from the side of both protection and free trade, a plea for sound money, and a defense of each of the great political parties. The