l Treatise on Secondary
Batteries."

* * * * *

EDWIN J. HOUSTON, Ph.D.
Professor of Physics, Franklin Institute, Pennsylvania; Joint Inventor
of Thomson-Houston System of Arc Lighting; Electrical Expert and
Consulting Engineer.
Joint Author of "The Electric Telephone," "The Electric Telegraph,"
"Alternating Currents," "Arc Lighting," "Electric Heating," "Electric
Motors," "Electric Railways," "Incandescent Lighting," etc.

* * * * *

WILLIAM J. HOPKINS
Professor of Physics in the Drexel Institute of Art, Science, and
Industry, Philadelphia.
Author of "Telephone Lines and their Properties."

[Illustration: GROSSE POINT EXCHANGE RACK Detroit Home Telephone
Company, Detroit, Mich. _The Dean Electric Co._]

[Illustration: LINE SIDE OF LARGE MAIN DISTRIBUTING FRAME]

Foreword

The present day development of the "talking wire" has annihilated both
time and space, and has enabled men thousands of miles apart to get into
almost instant communication. The user of the telephone and the
telegraph forgets the tremendousness of the feat in the simplicity of
its accomplishment; but the man who has made the feat possible knows
that its very simplicity is due to the complexity of the principles and
appliances involved; and he realizes his need of a practical, working
understanding of each principle and its application. The Cyclopedia of
Telephony and Telegraphy presents a comprehensive and authoritative
treatment of the whole art of the electrical transmission of
intelligence.

The communication engineer--if so he may be called--requires a knowledge
both of the mechanism of his instruments and of the vagaries of the
current that makes them talk. He requires as well a knowledge of plants
and buildings, of office equipment, of poles and wires and conduits, of
office system and time-saving methods, for the transmission of
intelligence is a business as well as an art. And to each of these
subjects, and to all others pertinent, the Cyclopedia gives proper space
and treatment.

The sections on Telephony cover the installation, maintenance, and
operation of all standard types of telephone systems; they present
without prejudice the respective merits of manual and automatic
exchanges; and they give special attention to the prevention and
handling of operating "troubles." The sections on Telegraphy cover both
commercial service and train dispatching. Practica