PREFACE. It is with some little trepidation that this book is put before the public, in view of the frequent important, and even radical, changes that up to the present have characterized the development of electrical engineering. It has, however, been thought that the science has now reached a stage which renders necessary some manual that will be of assistance to the active worker in the various branches. This book is not an encyclopedia, nor is it intended for a text-book, but it is hoped that as a compendium of useful data it may assist the practicing electrician and engineer. The matter included is representative of American practice, and no effort has been made to include any other, except in special cases. No excuse is offered for the very considerable amount of matter taken from trade publications of the larger electrical manufacturers, as in this country the engineers retained by such works are specialists often the best in their various branches; and it is an accident of condition only that in some cases has compelled the use of more of the publications of one company than of another, based upon available published material. Manufacturers have been most kind in supplying any special data and descriptions asked for; and the author's thanks are in particular due to a large circle of asso |