In this work, the author has endeavored to present a book embracing practical information for those who may wish to build for private or experimental use a set of wireless instruments which are more than toys but yet not so expensive as the commercial apparatus.

Many books have been published on the subject of wireless telegraphy, but in them the interests of the novice have been rather neglected and in order to build an outfit he has been forced to rely upon a series of disconnected articles published in the amateur periodicals.

It is the object of this book to show the construction of simple, efficient instruments by means of clear drawings, and to give enough elementary theory and practical hints to enable the experimenter to build a size and type in keeping with his needs and resources.

The tiresome "how to make" style has been avoided as far as possible. History and all unimportant details are omitted to give in their place a concise explanation of the parts played by the different instruments and the influence of developing their various factors.

A small lathe and a set of taps and dies are necessary to produce apparatus having a good appearance, but a little ingenuity displayed in adapting screws and parts of old electrical instruments oftentimes at hand will make these tools unnecessary.

Ordinary precaution and plenty of time should be used in the work. It is obvious that if a large coil is to be made, it is well to insure its successful completion by painstaking care and the use of proper materials. Neither is it wise to strain an instrument through becoming impatient and using it before it is properly completed and adjusted.

Wherever possible instructions have been given regarding the adjustment of the apparatus, but it is only by actual practice that the operator will acquaint himself with the most efficient manipulation.

Extracts from articles contributed by the Author to Popular Electricity have been used in the chapters on Spark Gaps, Oscillation Detectors and Telephone Receivers, through the courtesy of the editor, Mr. H. W. Young.

In conclusion, the writer wishes to express his thanks to the United Wireless Telegraph Company for views of their apparatus and to the other firms who have loaned electrotypes and supplied information. To those who have assisted in the preparation of the book, more especially to Mr. Safford Adams, for numerous suggestions and criticisms, the Author desires to express his full acknowledgments.

ALFRED POWELL MORGAN.

UPPER MONTCLAIR, N.J.

June, 1910.