l Engineering, American School of Correspondence

* * * * *

JAMES DIXON, E.E.
American Institute of Electrical Engineers

* * * * *

HARRIS C. TROW, S.B., _Managing Editor_
Editor-in-Chief, Textbook Department, American School of Correspondence

Authorities Consulted

The editors have freely consulted the standard technical literature of
America and Europe in the preparation of these volumes. They desire to
express their indebtedness particularly to the following eminent
authorities, whose well-known works should be in the library of every
telephone and telegraph engineer.

Grateful acknowledgment is here made also for the invaluable
co-operation of the foremost engineering firms and manufacturers in
making these volumes thoroughly representative of the very best and
latest practice in the transmission of intelligence, also for the
valuable drawings, data, suggestions, criticisms, and other courtesies.

* * * * *

ARTHUR E. KENNELY, D.Sc.
Professor of Electrical Engineering, Harvard University.
Joint Author of "The Electric Telephone." "The Electric Telegraph,"
"Alternating Currents," "Arc Lighting," "Electric Heating,"
"Electric Motors," "Electric Railways," "Incandescent Lighting," etc.

* * * * *

HENRY SMITH CARHART, A.M., LL.D.
Professor of Physics and Director of the Physical Laboratory,
University of Michigan.
Author of "Primary Batteries," "Elements of Physics," "University
Physics," "Electrical Measurements," "High School Physics," etc.

* * * * *

FRANCIS B. CROCKER, M.E., Ph.D.
Head of Department of Electrical Engineering, Columbia University,
New York; Past-President, American Institute of Electrical Engineers.
Author of "Electric Lighting;" Joint Author of "Management of
Electrical Machinery."

* * * * *

HORATIO A. FOSTER
Consulting Engineer; Member of American Institute of Electrical
Engineers; Member of American Society of Mechanical Engineers.
Author of "Electrical Engineer's Pocket-Book."

* * * * *

WILLIAM S. FRANKLIN, M.S., D.Sc.
Professor of Physics, Lehigh University.
Joint Author of "The Elements of Electrical Engineering,"
"The Elements of Alternating Currents."

* * * * *

LAMAR LYNDON, B.E., M.E.
Consulting Electric