Wireless Telegraphy, Its History, Theory and

Practice. A.Frederick Collins. 297 pp. 6x9 in.

323 Illustrations. $3.00. Supplied by Amateur

Work.

This volume may properly be classed as one of the most enterprising, instructive and inspiring treatises of the year.

It is a book written (not compiled) by one who has gone into wireless work with the genuine enthusiasm of the hobbyist; and the personal observations of the writer prove fully as valuable as the descriptive text. The illustrations are appropriate and up-to-date, the references liberal and exact as to title, volume and number.

The first sixty pages cover in detail the theory of Ether, Electric Waves, and the method of propagating waves by means of disruptive discharges. The chapters devoted to oscillations are especially thorough in their treatment, as well as those on capacity, inductance and resistance, with numerous formulae provided to explain the mathematical values in wireless telegraphy.

In the chapters on Induction Coils and their Operation, the author provides full specifications of coil construction and explains many points pertaining to coil windings, which we never have before seen in print. Especially valuable are the illustrated descriptions of vibrators and interruptors.

The articles on transmission, aerial wires and receptors describe the apparatus, both experimental and practical, in use in America and foreign countries, and many of the illustrations are directly from photographs made especially for this volume.

All the systems of merit in use in this and other countries, find full treatment with one exception, that of Mr. John Stone Stone of Cambridge, mention of whom is made in paragraphs on multiplex systems and predetermined length of waves. We believe more hacognition of this system will appear in later editions ien the results of government tests become public, as Mr. Collins has shown every evidence of impartiality throughout his book.

We commend this treatise to both the amateur and the professional. In the reference library it will prove a fitting companion to the able volumes of Vreeland and Lodge.

Machine Shop Tools and Methods. A. S. Leonard, 562 pp. 9 X5 1/2 in. 700 Illustrations. Cloth. John Wiley & Sons, New York. Price $4.00. Supplied by Amateur Work.

This book is an enlarged edition, for the first time in book form, of loose leaf instruction papers for the students of Michigan Agricultural College. It is undoubtedly much the best thing which has yet been published upon the subjects included therein, which in general include the tools to be found in a well equipped machine shop and the uses thereof. The opening chapter deals with tools for measuring, followed by hammers, chisels, files, surface plates and scrapers, the vise and accessories, drilling machines, drills, drill-sockets, chucks and accessories, lathes, planers, shapers, slotting machines, milling machines, grinding machines, and the various attachments accompanying each.

Anyone interested in metal working, be he amateur or professional, and especially manual training school teachers, will find this book of great value, and we cordially recommend its purchase.

Modern Industrial Progress. Charles H. Cochrane

647 pp. 9 X 6 in. Numerous illustrations. Cloth. J.

B. Lippencott Co., Philadelphia, Pa. Price $3.00 net. Supplied by Amateur Work.

A pleasing feature of this book, which at once attracts the attention of the reader, is the excellence of the illustrations, which are both numerous and well selected to supplement the text. The author has a singular adaptability for his work and keen appreciation of what is necessary to make a book of this general character both interesting and valuable.

It is not possible in the space available to more than indicate the wide range of subjects presented; electricity, in its numerous developments, is given a prominent place, flying machines, vessels of all kinds, implements of warfare, iron from the mine to finished tools of many kinds, and hundreds of other interesting topics, making it virtually a reference book of industrial progress. It will be found of great value to anyone desirous of being informed upon the industries-of the day. It would seem especially adapted for pub lic library use, and readers who may not find it convenient to purchase are recommended to propose it to the proper committee of their library.

The extreme length of Mexico is 1600 miles and it* greatest width 750 miles. The lofty Rocky Mountain plateau fills it nearly from ocean to ocean leaving but a narrow strip of coast. Its total area is 765,560 square miles, and the population about 14,000,000.