Wireless Telegraphy and Telephony Simply Explained

Transcriber's Note

This book was transcribed from scans of the original found at Google
Books. I have not transcribed the original book's index. Variant
spelling are not corrected. Some illustrations are rotated.

WIRELESS TELEGRAPHY

AND TELEPHONY

SIMPLY EXPLAINED,

A PRACTICAL TREATISE

Embracing Complete and Detailed Explanations of

the Theory and Practice of Modern Radio

Apparatus and its Present Day Applications,

together with a chapter on the

Possibilities of its Future Development

BY ALFRED P. MORGAN

EDITOR MECHANICAL AND ELECTRICAL DEPARTMENT OF THE "BOY'S MAGAZINE,"

AUTHOR OF

WIRELESS TELEGRAPH CONSTRUCTION FOR AMATEURS, ETC.

VERY FULLY ILLUSTRATED

NEW YORK

THE NORMAN W. HENLEY PUBLISHING CO.

132 NASSAU STREET

1916

COPYRIGHT 1915 AND 1912 BY

THE NORMAN W. HENLEY PUBLISHING COMPANY

Composition, Electrotyping and Printing

By J. J. LITTLE & Ives Co., New York

PREFACE

Probably no marvel of modern science so grips the imagination as the
mystery of those quivering impulses which go forth invisibly to link a
ship sailing over the seas with the shores of the distant land.

The author has endeavored to furnish a comprehensive explanation, in
simple language, of the theory and practice of this wonderful art, and
to explain, as far as possible, the importance of the position occupied
by wireless telegraphy to-day and the possibilities of to-morrow.

The title of this book naturally limits the amount of discussion that
can be undertaken, and so, in the space at command, there has not been
any real attempt made to enter into any engineering or constructive
details further than is necessary to make the text clear.

Much that might properly be made a part of the preface has been embodied
in the book, in order to avoid repetition, and to also bring certain
matter to the attention of those readers who consider a preface to be
merely an opportunity for the author of a book to express opinions very
often quite foreign to the title, and so unconcernedly skip it with
hardly more than a passing glance.

The author wishes to extend his sincere thanks to Mr. H. W. Young,
Editor of Popular Electricity; to Mr. John Firth, to Colonel George P.
Scriven, and to the Scientific American, for their kindness in supplying
photographs for some of the illustrations, and to his friend, Mr.
Safford Adams, who has kindly read the proofs and made many valuable
suggestions.

ALFRED P. MORGAN. May, 1915.

TO

NIKOLA TESLA

WHOSE GENIUS HAS HARNESSED ELECTRICITY TO THE DAILY WORK OF MAN AND
WHOSE INVENTIONS ARE THE BASIS OF ALL MODERN WIRELESS TRANSMISSION, THIS
BOOK IS DEDICATED.

TABLE OF CONTENTS

    PREFACE

    CHAPTER I. INTRODUCTORY: WIRELESS TRANSMISSION AND RECEPTION. THE
    ETHER. ELECTRICAL OSCILLATIONS. ELECTROMAGNETIC WAVES.

    CHAPTER II. THE MEANS FOR RADIATING AND INTERCEPTING ELECTRIC WAVES.
    AERIAL SYSTEMS. EARTH CONNECTION.

    CHAPTER III. THE TRANSMITTING APPARATUS.

    CHAPTER IV. THE RECEIVING APPARATUS.

    CHAPTER V. TUNING AND COUPLING, DIRECTIVE WAVE TELEGRAPHY.

    CHAPTER VI. THE DIGNITY OF WIRELESS. ITS APPLICATIONS AND SERVICE.
    WIRELESS IN THE ARMY AND NAVY. WIRELESS ON AN AEROPLANE. HOW A
    MESSAGE IS SENT AND RECEIVED.

    CHAPTER VII. THE EAR. HOW WE HEAR. SOUND AND SOUND WAVES. THE VOCAL
    CHORDS. THE STRUCTURE OF SPEECH.

    CHAPTER VIII. THE TELEPHONE TRANSMITTER AND RECEIVER. THE PHOTO
    PHONE. THE THERMOPHONE. THE SELENIUM CELL. THE SPEAKING ARC.

    CHAPTER IX. THE WIRELESS TELEPHONE.

    CHAPTER X. REMARKS. THEORY. ACCOMPLISHMENTS. MAXWELL'S HERTZ'S
    DISCOVERY. THE FUTURE.

    CATALOGUE OF GOOD, PRACTICAL BOOKS

LIST OF ILLUSTRATIONS

Fig. 1.—Throw a stone into a pool of water and little waves will radiate
from the spot where the stone struck.

Fig. 2.—A Leyden jar is a glass jar lined inside and outside with
tinfoil for about two-thirds of its height.

Fig. 3.—A static machine, connected to a Leyden jar.

Fig. 4.—A Leyden jar discharging through a coil of wire.

Fig. 5.—Curved line representing an oscillatory discharge of a Leyden
jar.

Fig. 6.—Navy type of Leyden jars.

Fig. 7.—The simplest practical transmitter.

Fig. 8.—A cross-section of the aerial and atmosphere.

Fig. 9.—Under the same conditions, but viewed from above.

Fig. 10.—A simple receiving arrangement.

Fig. 11.—An amateur aerial and station.

Fig. 12.—The Army wireless station at Fort Gibbons.

Fig. 13.—Lightning discharge near Montclair, N. J.

Fig. 14.–Photo of double lightning discharge passing to earth near the
First Orange Mountain, Montclair, N. J.

Fig. 15.—Vertical aerials of the grid, fan and inverted pyramid types.

Fig. 16.—A diagram showing pyramid aerial.

Fig. 17.–A diagram illustrating the directive action of a flat-top
aerial.

Fig. 18.—Aerials of the "V" and inverted "L" types.

Fig. 19.—A diagram showing the arrangement of a "T" aerial.

Fig. 20.—Flat top aerials of the inverted "U" and "T" types.

Fig. 21.—Umbrella aerial.

Fig. 22.—An amateur aerial (flat top).

Fig. 23.—Diagram showing the difference between loop and straightaway
aerials.

Fig. 24.—Showing how wires are arranged and insulated.

Fig. 25.—Aerial insulator.

Fig. 26.—Leading-in insulator.

Fig. 27.–A side view of the aerial shown in Fig. 22.

Fig. 28.—Diagram showing how batteries may be arranged.

Fig. 29.—The power plant of a Marconi transatlantic station.

Fig. 30.—If a magnet be suddenly plunged into a hollow coil of wire a
momentary current will be induced in the coil.

Fig. 31.—Magnetic phantom formed by a bar magnet.

Fig. 32.—Magnetic phantom formed by a wire carrying current.

Fig. 33.—Magnetic phantom formed by a coil of wire carrying current.

Fig. 34.—Diagram of induction coil.

Fig. 35.—Induction coil for wireless telegraph purposes.

Fig. 36.—Induction coil primary and secondary.

Fig. 37.—Interrupter for induction coil.

Fig. 38.—Electrolytic interrupter.

Fig. 39.—Open and closed core transformers.

Fig. 40.—Lines representing direct and intermittent direct currents.

Fig. 41.—Diagram representing alternating current.

Fig. 42.—High potential humming transformer.

Fig. 43.—High potential closed core transformer for wireless work.

Fig. 44.—Leyden jar set for oil immersion.

Fig. 45.—Oil immersed condenser.

Fig. 46.—Diagram showing construction of condenser.

Fig. 47.–Tubular condenser.

Fig. 48.—Helix.

Fig. 49.—Close coupled helix.

Fig. 50.—Spark gap.

Fig. 51.—Circuit showing tuned transmitting system employing close
coupled helix.

Fig. 52.—Photo of spark gap.

Fig. 53.—Quenched spark gap.

Fig. 54.—Diagram of aerial switch.

Fig. 55.—Photo of aerial switch.

Fig. 56.—Anchor gap.

Fig. 57.–Wireless key.

Fig. 58.—Photo of wireless key.

Fig. 59.—Key and aerial switch.

Fig. 60.—Portable receiving set and case.

Fig. 61.—Complete receiving outfit.

Fig. 62.—Portable pack set.

Fig. 63.—Complete receiving set.

Fig. 64.—Showing the construction of a watch case telephone receiver.

Fig. 65.—Pickard adjustable telephone receivers.

Fig. 66.—Illustrating the valve action of a rectifying detector.

Fig. 67.—A new type of silicon detector.

Fig. 68.—Diagram drawing analogy between rectifying action of a detector
and pump.

Fig. 69.—Pyron detector.

Fig. 70.—Perikon detector.

Fig. 71.—Silicon detector.

Fig. 72.—Electrolytic detector.

Fig. 73.—Electrolytic detector in circuit.

Fig. 74.—Potentiometer.

Fig. 75.—Diagram showing how potentiometer is connected in a circuit.

Fig. 76.—Analogy between swinging and tuning.

Fig. 77.—Receiving a message in a Marconi transatlantic station.

Fig. 78.—Tuning coil of the double slide type.

Fig. 79.—Diagram showing fixed condenser in circuit.

Fig. 80.–Fixed condenser.

Fig. 81.—Rotary variable condenser.

Fig. 82.—Interior of rotary variable condenser, showing construction.

Fig. 83.—Dr. Seibt's rotary variable condenser.

Fig. 84.—Sliding plate variable condenser.

Fig. 85.—Diagram showing arrangement of rotary variable condenser in
receiving circuit.

Fig. 86.—Chain and ball arranged to illustrate the effect of tuning.

Fig. 87.—Loose coupled helix.

Fig. 88.—Hot-wire ammeter.

Fig. 89.—The principle of the hot-wire ammeter.

Fig. 90.—Diagram showing loose coupled helix in circuit.

Fig. 91.—Loose coupled tuning coil.

Fig. 92.—Loose coupled tuner.

Fig. 93.—Diagram showing position of loose coupler in circuit.

Fig. 94.–Fort Gibbons, Alaska, wireless station.

Fig. 95.—Transmitting condenser.

Fig. 96.—Braun's method for directing wireless telegraph signals.

Fig. 97.—Bellini-Tosi radio-goniometer.

Fig. 98.—Arrangement of Bellini and Tosi for directive wireless
telegraphy.

Fig. 99.—Complete receiving and transmitting outfit.

Fig. 100.—Special lightweight wireless telegraph set for airship
service.

Fig. 101.—Telefunken wireless cart, showing transmitter.

Fig. 102.—Telefunken wireless cart for military service.

Fig. 103.—Telefunken wireless wagon set in operation at Fort Leavenworth.

Fig. 104.—Wireless room aboard the U. S. transport "Buford".

Fig. 105. The apparatus set up for operation.

Fig. 106.—Wireless equipped automobile.

Fig. 107.—Co. Signal Corps at San Antonio.

Fig. 108.—U. S. Signal Corps pack set shown open and closed.

Fig. 109.—The receiving apparatus of the airship "America".

Fig. 110.—Interior of the N. Y. Herald Press station.

Fig. 111.—Operating the U. S. Signal Corps airship wireless apparatus.

Fig. 112.—The N. Y. Herald station, showing aerial.

Fig. 113.—Operator Jack Irwin overhauling the wireless apparatus for the
dirigible balloon "America".

Fig. 114.—Morse code.

Fig. 115.—Continental code.

Fig. 116.—Transmitting equipment of the high-power station at Nauen.

Fig. 117.—Duplex receiving apparatus.

Fig. 118.—Breaking-in system.

Fig. 119.—The receiving apparatus of the station at Nauen.

Fig. 120.—Diagram of the ear.

Fig. 121.—The ossicles.

Fig. 122.—Bon jour.

Fig. 123.—Experiment showing sounding bodies are in vibration.

Fig. 124.—Method of registering vibrations of a tuning fork.

Fig. 125.—Way line made by a bristle attached to a tuning fork prong in
vibration when passed over smoked glass.

Fig. 126.—Illustrating the action of air waves.

Fig. 127.—The vocal chords in position for making a sound.

Fig. 128.—The vocal chords when relaxed.

Fig. 129.–Koenig's manometric flame apparatus.

Fig. 130.—Appearance of manometric flame in revolving mirror.

Fig. 131.—Diagram of a telephone transmitter.

Fig. 132.—Diagram showing the principle and construction of the
telephone receiver.

Fig. 133.—The photophone.

Fig. 134.—Photophone receiving apparatus.

Fig. 135.—Photophone transmitting apparatus.

Fig. 136.—Powerful searchlight arranged to transmit speech over a beam
of light.

Fig. 137.—The electric arc.

Fig. 138.—Circuit showing how a singing arc is arranged.

Fig. 139.—A logical form of wireless telephone which is impractical.

Fig. 140.—DeForest wireless telephone equipment.

Fig. 141.—Wireless telephone receiving apparatus (induction method).

Fig. 142.—Fessenden wireless telephone transmitting phonograph music.

Fig. 143.—Diagram illustrating why damped oscillations will not carry
the voice.

Fig. 144.—How the sound waves of the voice are impressed upon undamped
oscillations.

Fig. 145.—Arrangement of the speaking arc.

Fig. 146.—Diagram showing how a wireless telephone transmitting system
is arranged.

Fig. 147.—Poulsen wireless telephone equipment.

Fig. 148.—The Majorana wireless telephone transmitter.

Fig. 149.—Showing the brush discharge from a Marconi transatlantic
aerial at night.

Fig. 150.—An amateur wireless' telegraph station.

Fig. 151.—The high-power naval wireless telegraph station under
construction at Washington, D. C.

Fig. 152.—The curved lines represent the radius of the government
high-power wireless stations and show the zones over which direct
communication may be had with ships.

Fig. 153.—The aerial system of a transatlantic station.

Fig. 154.—Fong Yee, a Chinese amateur wireless operator.

Fig. 155.—Tesla world power plant.

Fig. 156.—Twenty-five-foot sparks from a Tesla transformer.

CHAPTER I. INTRODUCTORY: WIRELESS TRANSMISSION AND RECEPTION. THE ETHER.
ELECTRICAL OSCILLATIONS. ELECTROMAGNETIC WAVES.

Wireless telegraphy, that marvelous art which has made possible the
instantaneous transmission of intelligence between widely distant parts
having no apparent physical connection save that of the earth, air, and
water, is one of those wonders of science which appeal to the average
mind as either incomprehensible or only explainable through the use of
highly technical language. Contrary to this general opinion, however,
the whole theory and practice of the wireless transmission of messages
is capable of the simplest explanation.

[Illustration: FIG. 1.—Throw a stone into a pool of water and little
waves will radiate from the spot where the stone struck.]

Throw a stone into a pool of water. A disturbance is immediately
created, and little waves will radiate from the spot where the stone
struck the water, gradually spreading out into enlarging circles until
they reach the shores or die away. By throwing several stones in
succession with varying intervals between them it would be possible to
so arrange a set of signals that they would convey a meaning to one who
is initiated, standing on the opposite side of the pool. The little
waves are the vehicle which transmits the intelligence, and the water
the medium in which the waves travel.

Wireless telegraph instruments are simply a means for creating and
detecting waves in a great pool of ether.

Scientists suppose that all space and matter is pervaded with a
hypothetical medium of extreme tenuity and elasticity, called
luminiferous ether, or simply ether.

Although ether is invisible, odorless, and practically weightless, it is
not merely the fantastic creation of speculative philosophers, but is as
essential to our existence as the air we breathe and the food we eat. By
imagining and accepting its reality, it is possible to explain and
understand many scientific puzzles. The universe is a vast pool of
ether. It is all-pervading. There is no void. It is diffused even among
the molecules of which solid bodies are composed. The study of this
substance is, perhaps, one of the most fascinating and important duties
of the physicist.

Ninety million miles away from our earth is a huge flaming body of
vapors and gases, called the sun. This seething mass of flame and heat
furnishes us more than mere winter and summer and night and day, for we
on this earth are not living on our own resources, and the real work of
the world so necessary for even bare existence is accomplished by the
energy of the sun stored up in coal, in plants and trees and mountain
torrents.

Light is known to be vibrations of an extremely rapid
period—*electromagnetic waves*, they are called. Heat can be shown to be
of the same nature. Traveling at the rate of over 180,000 miles per
second, these two great gifts of the sun come streaming continually down
to us over the inconceivable distance of almost 100,000,000 miles. Both
require a medium for their propagation. The ether supplies it. It is the
substance with which the universe is filled. Incidentally it is also the
seat of all electrical and magnetic forces.

[Illustration: FIG. 2.—A Leyden jar is a glass jar lined inside and out
with tinfoil for about two-thirds of its height.]

In throwing the stone into the pool of water, muscular energy of the arm
is transferred to the stone, and the latter, upon striking the surface
of the pond, imparts a portion of that stored energy to the little waves
which are immediately created in the water. In setting up
electromagnetic waves for wireless communication the energy imparted to
the ether is electrical energy, developed by certain interesting
instruments explained further on.

Let us consider briefly how the waves are created in a wireless
telegraph station. Almost every one has seen and heard the brilliant
snapping spark produced by the discharge of a Leyden jar. A Leyden jar
in its common form is a glass jar lined inside and out with tinfoil for
about two thirds of its height. A brass rod, terminating in a knob,
connects below with the inner coating, usually by means of a loose
chain. It may be described as a device which is capable of storing
electricity in the form of energy and discharging this energy again in
actual electricity.

This discharge has been the subject of many interesting investigations
of direct interest.

[Illustration: FIG. 3.—A static machine connected to a Leyden jar.]

The inner and outer coatings are connected to the terminals of a static
electric machine (an apparatus for generating electricity), and the
machine set in rotation. After the jar has been charged, the electric
machine is disconnected and one end of a coil of heavy wire connected to
the outside coating, while the other end of the wire is made to approach
the knob connected with the inner coating. Before the end of the wire
reaches the knob a discharge occurs through the coil, producing a noisy
brilliant spark between the wire and the knob. The discharge appears
like a single spark, but in reality it is composed of a great many
following each other in rapid succession. The jar discharges its energy,
first by a tremendous rush of current in one direction, and then another
discharge somewhat smaller than the first in the opposite direction.
There is a series of these discharges in reverse directions, but each
discharge is less and less, until the whole amount of energy is
expended. The complete series of discharges takes place in an almost
immeasurable fraction of time. It is from this phenomenon that the
electrical term "high frequency oscillations," so often heard of in
"wireless" parlance, is derived.

[Illustration: FIG. 4.—A Leyden jar discharging through a coil of wire
produces a brilliant spark and high frequency oscillations are created.]

[Illustration: FIG. 5.—Curved line representing an oscillatory discharge
of a Leyden jar.]

[Illustration: FIG. 6.—Navy type of Leyden jars. Coated with copper
deposited upon the surface of the glass.]

High frequency oscillations are the "pebbles" which, dropped into the
vast pool of ether, everywhere, set up "ripples" called electromagnetic
waves (identical with the electromagnetic waves of light, but longer and
so beyond the limits of our spectrum and the vision of the eye). The
manner in which this is accomplished may be explained by saying that the
charge creates a state of strain in the surrounding ether, and then
abruptly releases it. Ether possesses a high degree of elasticity, so
that when the state of strain is thus suddenly released, it immediately
returns to its former state. The sudden motion of the ether results in
waves which spread out from their source in enlarging circles.

Wireless telegraphy, as it is practiced to-day, is based upon the fact
that a system of wires or circuits, through which high frequency
oscillations are surging, becomes a source of electromagnetic waves.
Various methods have been devised for making the system more efficient
and capable of giving better results with a given amount of power.

[Illustration: FIG. 7.—The simplest practical transmitter that it is
possible to devise for the purpose of sending messages.]

Fig. 7 is a diagram showing the simplest practical transmitter that it
is possible to devise for the purpose of sending messages a sufficient
distance to be of any value.

It would be impractical to use a static electric machine for wireless
transmission, and so an induction coil or transformer is employed. These
latter instruments are for the purpose of raising electric currents of a
comparatively low voltage to the high potential, where they have the
power of generating high frequency oscillations.

In the illustration the current from a battery is led into the primary
of an induction coil. The primary is simply a coil consisting of a few
turns of wire, which induces a high voltage in a second coil consisting
of a larger number of turns, and called the secondary. The terminals of
the secondary are led to a spark gap—an arrangement composed of two
polished brass balls, separated by a small air space. One of the balls,
in turn, is connected to a metal plate buried in the earth, and the
other to a network of wires suspended high in the air and insulated from
all surrounding objects.

As noted above, a Leyden jar consists of two metallic coatings,
separated by a wall of glass. The purpose of the coatings is to form a
conductor and carry an electric charge. A Leyden jar possesses a
characteristic called, in electricity, capacity. Any two conductors
separated by an insulating medium possess "capacity" and all the
properties of a Leyden jar or condenser.

The waves generated by a Leyden jar would be somewhat weak and confined
to its own immediate neighborhood, so recourse is had to the aerial and
ground, in order to increase the area over which the oscillations exert
their influence in setting up the electric waves. The aerial system
corresponds to one coating of the Leyden jar, and the ground to the
other. The insulating medium in between, corresponding to the glass, or
dielectric, is the atmosphere.

When the key connected to the induction coil is pressed, the battery
current flows through the primary and induces a high voltage current in
the secondary, which charges the aerial and ground exactly as the static
machine charges the two coatings of the Leyden jar. A spark then leaps
across the spark gap and the current surges back and forth through the
aerial, generating "high frequency oscillations" which, in turn, set up
a state of strain in the surrounding ether, and cause the waves to
travel out from the system.

[Illustration: FIG. 8. If a cross section of the aerial and atmosphere
could be made in the same manner that an apple is sliced with a knife
and the waves held stationary, they would appear as above.]

These waves follow the contour of the earth, and so may cross mountains
and valleys, and travel anywhere. They radiate from the aerial like the
ripples from a pebble in a pool of water, in gradually enlarging
circles. If a cross section of the aerial and atmosphere could be made
in the same manner that an apple can be sliced with a knife, and the
waves held stationary long enough to see them, they would appear as in
Fig. 8. The curved lines represent the lines of strain induced by the
oscillations. Each group of lines represents a wave. It will be noticed
as they radiate farther from the aerial that they become larger and
spread out.

[Illustration: FIG. 9.—Under the same conditions, but when viewed from
above, the appearance would be that of a series of concentric circles.]

The electromagnetic waves have the power of exciting oscillations in a
conductor on which they impinge. This is made use of for the purpose of
receiving the messages. When the waves strike the aerial of a distant
station they set up high frequency oscillations, which are usually too
weak to make their presence known except with the aid of a sensitive
device, called a detector.

[Illustration: FIG. 10.—A simple receiving arrangement. The detector
rectifies the oscillatory currents passing from the aerial to the
ground so that they will flow through the telephone receiver and
register as sound.]

The most prominent type of detector in use to-day is a crystal of
silicon, iron pyrites, zincite or certain other minerals. The mineral is
placed between two contact points, one or both of which are adjustable
so that the most sensitive portion of the mineral may be selected. A
telephone receiver is connected across the terminals of the detector.
When the electromagnetic waves from the transmitting station strike the
aerial of the receiving station, they set up therein a series of high
frequency oscillations, corresponding to the Morse signals emitted from
the transmitter. The oscillations flow back and forth through the aerial
and ground, striking the mineral detector on their journey. The high
frequency oscillations are alternating currents, because they reverse
their direction many thousand times per second. Such a current will not
pass through the telephone receiver, because the little magnets
contained therein exert a choking action on alternating currents of high
frequency and effectually block their passage. The mineral detector acts
as a valve, allowing the current to pass through in one direction, but
not permitting it to return or go in the opposite direction. The result
is a series of impulses flowing in one direction only, and therefore
called a direct current. Such a current will flow through a telephone
receiver and produce a motion of the diaphragm which imparts its motion
to the surrounding air, the result being sound waves audible to the ear.
By varying the periods during which the key is pressed and the
oscillations are being produced, according to a prearranged code, the
sounds in the receiver may be made to assume an intelligible meaning.

CHAPTER II. THE MEANS FOR RADIATING AND INTERCEPTING ELECTRIC WAVES.
AERIAL SYSTEMS. EARTH CONNECTION.

Every radiotelegraphic station may be summed up as comprising these
elements: first of all, certain appliances collectively forming the
transmitter and serving to create the waves; secondly, the receiving
apparatus, whose function is to detect the signals of some far-distant
sending station, and lastly, an external organ called the aerial, or
antenna, consisting of a huge system of wires elevated high in the air
above all surrounding objects, either vertically or sloping, or partly
horizontal and partly vertical, which radiates or intercepts the
electromagnetic waves, accordingly as the station is transmitting or
receiving.

The antenna is at once both the mouth and the ear of the wireless
station. Its site and arrangement will greatly determine the efficiency
and range of the apparatus.

The site selected is preferably such that the aerial will not be in the
immediate neighborhood of any tall objects, such as trees, smokestacks,
telephone wires, etc., because such objects not only absorb an
appreciable amount of energy when the station is transmitting messages,
but also noticeably shield the aerial from the effects of incoming
signals and limit its range.

The nature of the ground over which the waves must travel also enters
into the question, and is always considered in locating a station. In
gliding over the surface of the earth, the waves generate weak currents
in the earth itself. If the ground is very stony or dry, these earth
currents encounter considerable resistance, and the possible distance of
transmission over soil of this sort is very much less than if it were
moist. Moist soil and water offer very little resistance, and the
difference in the results obtainable at the receiving station when the
waves travel over an area of this sort is very marked.

[Illustration: FIG. 11.—An amateur aerial and station.]

A station which can only send 100 miles over land can send messages
three or four hundred miles over the ocean.

Forests exert a very decided effect upon the electric waves. Each
individual tree acts as an antenna, reaching up into the air and
absorbing part of the energy. The difference in the range of a station
during the summer months and that of the same station in winter is
considerable. In summer the trees are full of sap and, being much better
conductors of electricity when in this condition, act in the capacity of
innumerable aerials rising in the air, and able to absorb appreciable
amounts of energy. During these same months the air becomes highly
ionized, in which state the air molecules carry an electric charge, and
are particularly opaque to the waves. This condition also usually exists
in the presence of sunlight, the result being that the most favorable
time for the wireless transmission of messages are the hours around
midnight.

[Illustration: FIG. 12.—The Army wireless station at Fort Gibbons,
Alaska, showing steel lattice work mast and aerial system.]

Locality is another factor which usually receives a fair share of
attention in selecting the site. Certain sections of the country, for
seemingly no apparent reason, are very hard to transmit messages, either
to or from. Wireless stations located on the Pacific Coast, for
instance, are more efficient than those situated along the Atlantic
seaboard, while those in the tropical regions are only able to send
short distances in comparison to those farther north or south. Messages
seem to travel better in the direction of the lines of longitude than
along the lines of latitude.

[Illustration: FIG. 13.—Lightning discharge near Montclair, N. J.]

"Static," that "bugbear" of the wireless operator, is very much more in
evidence in the eastern parts of the United States and in South America
than it is on the western coast of the country. If any one should ask a
wireless operator what "static" is, he would probably reply, "a
nuisance." In reality, it is caused by atmospheric electricity. When
atmospheric electricity "jumps," it is called "lightning." A lightning
discharge sets up very powerful waves in the ether, which strike the
aerial of the wireless station and produce a peculiar rumbling,
scratching sound in the telephone receivers, and sometimes seriously
interfere with a message. In fact, it is possible for a wireless
operator to predict a thunder shower by many hours from the sounds he is
able to hear in his telephone receivers.

The cause of lightning is the accumulation of electric charges in the
clouds. The electricity resides on the surface of the particles of water
in the cloud. These charges grow stronger as the particles of water
coalesce to form larger drops, because, as they unite, the surface
increases proportionally less than the volume and, being forced to lodge
on a smaller space, the electricity becomes more "concentrated," so to
speak. For this reason the combined charge on the surface of the larger
drop is more intense than were the charges on the separate particles,
and the "potential" is increased. As the countless multitudes of drops
grow larger and larger, in the process of forming rain, the cloud soon
becomes heavily charged.

Through the effects of a phenomenon called "induction," a charge of the
opposite kind is produced on a neighboring cloud or some object of the
earth beneath. These charges continually strive to burst across the
intervening air and neutralize each other. As soon as the potential
becomes sufficient to break down this layer of air, a lightning stroke
from one to ten miles long takes place. The heated air in the path of
the lightning expands with great force, but immediately other air rushes
in to fill the partial vacuum, thus producing atmospheric waves, which
impress the ear as the sound called thunder.

Wireless stations belonging to the United States navy and located on
land are usually housed in a small building in the immediate
neighborhood of the tall wooden mast which supports the aerial.
Commercial stations are usually situated on the top floor of a high
office building, or a hotel, and the aerials supported by a steel
lattice-work tower. Amateurs place a small pole on the roof of the
house, or in a tree, and locate their station in any convenient room
near the top of the house.

[Illustration: FIG. 14.—Photo of double lightning discharge passing
to earth near the First Orange Mountain, Montclair, N. J.]

[Illustration: FIG. 15.—Vertical aerials of the "grid," "fan"
and "inverted pyramid" types.]

Aerials are of numerous classes and forms, but the most prominent types
can be divided into two main groups, called respectively, the "Flat-top"
and "vertical" antenna.

The vertical aerials are the older form, and are usually employed for
long-distance work or ultra-powerful stations. The aerials intended for
transmission from Europe to America, installed by Marconi, consisted of
huge inverted pyramids, supported by four heavy lattice-work towers,
over 200 feet high. Vertical aerials also sometimes take the form of an
umbrella, or fan, where only one supporting pole is available. Iron pipe
masts may be employed for the purpose, by setting on an insulating base.
The umbrella aerial is used extensively in the army and portable sets.

The flat-top aerials are gradually coming into very extended use. They
are used to the exclusion of all others on shipboard. They need not be
so high as a vertical type aerial in order to be as efficient. Flat-top
aerials consist of a vertical portion and a nearly horizontal portion.
The horizontal portion is practically useless, as far as its work in
radiating waves is concerned, it being used for the purpose of
increasing the capacity of the aerial. An increase in capacity in an
aerial means that more energy can be stored and radiated. Flat-top
aerials have the objection, however, of possessing a directive action;
that is, they receive, or radiate waves, better in one direction than in
the other. A flat-top aerial always receives or transmits better in the
direction that the ends point than in a direction at right angles to the
wires.

[Illustration: FIG. 16.—A diagram showing pyramid aerial.]

The accompanying diagram is an illustration to show the effects of the
directive action of a flat-top aerial. The black lines marked A B, and
appearing very much like a little grating, represent an aerial of the
inverted "L" type, looking down on it from above. B is the free end of
the aerial, and A the closed end, or end to which the wires leading down
to the station are attached. If a snapshot of the lines of strain
produced in the ether as the waves move away from the aerial could be
taken, they would appear like the curved lines in the illustration. It
can be readily seen that those passing outward from the aerial in a
direction opposite to that in which the free end points are the
strongest, and that the radiation in that direction is the best.

[Illustration: FIG. 17.–A diagram illustrating the directive action
of a flat-top aerial.]

[Illustration: FIG. 18.—Aerials of the "V" and inverted "L" types.]

The "V" aerial and also the inverted "L" type both receive waves much
better when they come from a direction opposite to that in which the
free end points.

[Illustration: FIG. 19.—A diagram showing the arrangement of a "T"
aerial.]

Probably the most interesting feature of the directive action of aerials
lies in the fact that a land station is able to determine the
approximate bearing of a ship signaling with a horizontal aerial.

[Illustration: FIG. 20.—Flat top aerials of the inverted "U" and "T"
types.]

It is beyond the scope of the book to enter into all of the engineering
details pertaining to the installation of a wireless station, but a few
remarks and instructions for the benefit of those who may be interested
in this phase of the subject may be appreciated.

The flat-top "T" aerial gives the best "all around" results. The
vertical and umbrella forms are close seconds.

[Illustration: FIG. 21.—Umbrella aerial.]

For the very best results, the top or horizontal portion of a "T" aerial
should be slightly shorter than the vertical section.

The umbrella type of antenna is very efficient. Instead of a wooden
mast, an iron pipe terminating above in a system of wires, inclining
downward and serving both as part of the aerial and as guys to support
the pole, is often used. The bottom of the pole is placed on an
insulating base, protected from the rain by a small shelter. The wires
are insulated near the lower ends by strain-insulators. The action of
the wires is to serve as a capacity extension to the aerial.

[Illustration: FIG. 22.—An amateur aerial (flat-top).]

Vertical aerials are not as efficient as either of those forms just
mentioned. They require to be 50 per cent. higher than a flat-top
aerial, in order to be of the same value.

The "L" and "V" types are somewhat directional. They are used where the
highest point must be near the station, with a lower point some distance
away. It is possible to secure excellent results with either type.

The terms straightaway and loop denote the method of connecting the
aerial wires. In the first form the upper or free ends of the wires
terminate at the insulators. In the loop form they are all connected
together, and divided into two sections, each of which is led separately
into the operating room.

[Illustration: FIG. 23.—Diagram showing the difference between "loop" and
"straightaway" aerials.]

The straightaway aerial is the most efficient in most cases, but
wherever great height cannot be obtained, or the aerial is necessarily
short, the loop aerial will give the best results.

Bare copper wire is the best, and is generally used for aerials.
Wherever the stretch is 100 feet or over, however, so that the wires are
subjected to considerable strain from their own weight, phosphor bronze
is used because of its greater tensile strength. Commercial and navy
stations employ stranded wire. High frequency currents have the peculiar
property of traveling near the surface of wires and conductors. They do
not permeate to the center of the wire, as do normal currents. The
surface of a stranded wire is greater in comparison to its cross-section
than a solid conductor of the same diameter, and therefore is often
employed because it offers less resistance to currents of this sort.

[Illustration: FIG. 24.—Showing how wires are arranged and insulated.]

Aluminum wire is very light, and causes very little strain on the pole
or cross-arms. It offers more resistance than copper, but some of the
larger sizes may be used with equally good results.

Iron wire must never be used, even if galvanized or tinned. It possesses
a certain reactance tending to choke off the high frequency currents.

[Illustration: FIG. 25.—Aerial insulator.]

The aerial is always very carefully insulated from its supports and
surrounding objects by special insulators, capable of withstanding
severe strains, made of a moulded material having an iron ring imbedded
in each end.

[Illustration: FIG. 26.—Leading-in insulator.]

The wires leading from the aerial to the operating room are called the
"rat-tail," or "lead-in." They must be very carefully insulated by
leading through a bushing placed in the wall or window of the operating
room.

One of the most important factors in a wireless station is the proper
earthing arrangement. The usual method is to use large copper plates
buried in moist earth, or thrown in the sea. On shipboard it is merely
necessary to connect the earth wire to the metallic plates of which the
hull of the vessel is built. Amateurs employ the water or gas pipes in
the house, the former being preferred. Connections are established by
means of a ground clamp.

In the country, where water-pipes are not available, the best way is to
bury a sheet of copper three or four feet deep in moist earth.

A very efficient earth can be formed by spreading a large area of
chicken wire netting over the ground. This method is the best where the
earth is very dry or sandy, and no other way is readily convenient.

[Illustration: FIG. 27.—A side view of the aerial shown in Fig. 22.]

CHAPTER III. THE TRANSMITTING APPARATUS.

The principal instruments composing the apparatus used for sending the
wireless messages comprise an induction coil, or in its place a
transformer, a key, a spark gap, a condenser, and a helix.

The current supply available will determine the type of the instruments,
and whether an induction coil or a transformer is used. Unless current
mains for light and power are already installed, it must be generated by
an engine and dynamo, or recourse had to batteries. Induction coils may
be operated on either direct or alternating current. Dry cells are most
commonly employed to furnish the current for small induction coils, but
a storage or some form of renewable primary cell, such as the Fuller and
Edison, is necessary if the coil is a large one. When dry cells are
used, they should be connected in series multiple, as shown in the
accompanying diagram. This method of connecting distributes the load,
and considerably lengthens the life of the battery.

[Illustration: FIG. 28.—Diagram showing how batteries may be arranged
in "series" or "series multiple."]

[Illustration: FIG. 29.—The power plant of a Marconi transatlantic
station, showing engine and generator.]

When the source of current supply is alternating, an induction coil may
be operated as a transformer. Both induction coils and transformers are
instruments for raising the voltage of the ordinary available current
from a comparatively low value, 6-220 volts, to a quantity
(15,000–20,000 volts), where it can properly charge the aerial and
create a state of strain, or, as it is called in technical parlance, an
electro-static field.

[Illustration: FIG. 30.—If a magnet is suddenly plunged into a hollow
coil of wire a momentary electric current will be induced in the coil.]

Both the induction coil and transformer depend for their operation upon
the principles of magnetic induction. In 1831, Michael Faraday, a famous
English chemist and physicist, discovered that if a magnet be suddenly
plunged into a hollow coil of wire, that a momentary current of
electricity is generated in the coil. As long as the magnet remains
motionless, it induces no current in the coil, but when it is moved back
and forth, it sets up the currents. The source of electrical energy is
the mechanical work done in moving the magnet. The medium which changes
the mechanical energy into electricity is called the magnetic field. The
magnetic field is a peculiar state or condition of the space in the
immediate neighborhood of a magnet. Its real nature is very hard to
explain and not easily understood. Suffice it to say, however, that the
current is induced in the coil of wire only when the magnetic field is
changing, either decreasing or increasing. The change is produced by
moving the magnet because its influence on the coil will be great or
small accordingly as it is near or far.

[Illustration: FIG. 31.—Magnetic phantom formed by bar magnet.]

It is possible to show the existence of the magnetic field by placing a
sheet of glass over a bar magnet and then sprinkling iron filings on the
glass. They will settle down in curving lines as in Fig. 31, forming a
magnetic phantom. The curved lines formed by the filings represent the
direction of the lines of force which make up the magnetic field.

If we should examine the space in the immediate neighborhood of a coil
of wire carrying a current of electricity it would be found that a
similar state of affairs existed there and that the coil also possessed
a magnetic field composed of lines of force flowing around it.

This is readily shown by punching a small hole in a piece of cardboard
and passing a wire carrying a current of electricity through the hole.
If iron filings are sprinkled on the cardboard, they will arrange
themselves in circles around the wires, forming a magnetic phantom and
showing that a coil of wire carrying a current of electricity generates
a magnetic field in its vicinity. By forming the wire into a coil the
magnetic field generated is much stronger, for the then combined effect
of the wires is secured.

[Illustration: FIG. 32.—Magnetic phantom formed by wire carrying
current.]

[Illustration: FIG. 33.—Magnetic phantom formed by coil of wire carrying
current.]

The induction coil and transformer are simply instruments utilizing the
principle that a coil of wire carrying a current possesses a magnetic
field which will induce a current of electricity in another neighboring
coil.

[Illustration: FIG. 34.—Diagram of an induction coil.]

The induction coil consists essentially of a primary winding of heavy
wire wound around a soft iron core and surrounded by a secondary coil
consisting of many thousand turns of fine wire, carefully insulated. The
current from a battery is sent through the primary coil and sets up a
magnetic field. The magnetic field induces a current in the secondary
whose voltage is approximately proportional to the ratio of the turns of
the secondary to the primary. Thus, if the secondary contains one
hundred times as many turns of wire as the primary the induced voltage
will be one hundred times the voltage of the original primary current.
The purpose of the iron core is to concentrate the magnetic field and
make the coil more efficient. Since currents are only induced in the
secondary when the magnetic field is changing, an automatic device
called an interrupter or sometimes a vibrator, is employed to rapidly
turn the current flowing through the primary on and off. The interrupter
consists of a spring carrying a platinum point against which presses a
second piece of platinum on the end of an adjustable thumbscrew.
Platinum is necessary because the current of electricity would quickly
oxidize and burn up any other material. The interrupter spring is placed
near the end of the core so that the magnetism of the latter will draw
it forward away from the thumbscrew and interrupt the current. As soon
as the current ceases to flow the core loses its magnetism and the
spring returns to its former position repeating the cycle very rapidly a
large number of times per second. The interrupter is fitted with a
condenser shunted across its terminals to stop sparking at the platinum
points and also to make the currents in the secondary more intense.

[Illustration: FIG. 35.—Induction coil for wireless telegraph purposes.]

[Illustration: FIG. 36.—Induction coil, primary and secondary.]

The voltage of the currents in the secondary is high enough to leap
across an air gap in a torrent of sparks. The spark of an induction coil
intended for wireless work should be thick and heavy. It should be
sufficiently hot and flaming to ignite a piece of paper. A rapid
vibrator giving a high pitched spark is better than a slow one not only
because it causes a more intense and powerful spark but because the
human ear is the most sensitive to high pitched sounds and such a spark
is more easily read at the receiving station.

[Illustration: FIG. 37.—Interrupter for induction coil.]

[Illustration: FIG. 38.—Electrolytic interrupter.]

When the coil is a very large one and operated on the 110 volt current
an electrolytic interrupter is substituted for the mechanical type. One
pole of the current is connected to a lead plate placed in a jar
containing a mixture of sulphuric acid and water. The other side of the
current is connected to a platinum wire placed in a porcelain tube so
that only a small part of the lower end is in contact with the solution.
When the current passes a bubble forms at the end of the wire shielding
it from the liquid, and thus interrupting the current. The bubble is
almost immediately discharged however and the current allowed to flow an
instant before a new one forms. This operation is repeated continuously
at a frequency sometimes as high as a thousand per second. An
electrolytic interrupter is both an expensive and a troublesome device.
There are other types of interrupters of value in wireless service but
the limitations of space prohibit any account.

[Illustration: FIG. 39.—Open and closed core transformers.]

The transformer is acknowledged to be the best practice as a means of
stepping up the voltage of a circuit for wireless telegraph purposes.

Alternating current is necessary to operate a transformer. There are two
distinct types of transformers known as the "open" and "closed core"
accordingly as the shape of the latter is straight like that of an
induction coil or in the form of a hollow rectangle. The closed core
transformer consists of two coils of insulated wire, forming a primary
and a secondary, wound upon a rectangular core like that shown in Fig.
39B. The core is built up of sheets of iron called laminations, to
reduce the heating and increase the efficiency of the machine.

[Illustration: FIG. 40.—Lines representing direct and intermittent
direct currents.]

As noted above currents are only induced in a coil when the magnetic
field is changing. The interrupter is employed to rapidly "make" and
"break" the circuit. Every time that the circuit is made the primary
coil creates a field and every time it is broken it is destroyed. A
direct current is a current which passes in one direction only. It may
be represented by a straight line as A in Fig. 40. Its voltage is
usually very constant and does not vary greatly. In the case of electric
lighting circuits the normal voltage is usually 110. If an interrupter
is included in the circuit the current may be represented by a broken
line, the spaces corresponding to the periods when the current is
"broken" and the lines to the periods it is flowing. The interrupter
creates an intermittent direct current.

[Illustration: FIG. 41.—Diagram representing alternating current.]

An alternating current is one which reverses its direction and passes
first one way and then the other. It may be represented by the curved
line shown in Fig. 41. It starts at zero and rises to a maximum,
gradually dying away to zero, then passes in the opposite direction,
rising to a maximum and dying away again. This is repeated a definite
number of times per second; when the current rises from zero, reverses
and returns to zero it is said to have passed through a cycle. From a to
c represents a cycle—from a to b is an alternation. The usual frequency
of commercial alternating currents is 60 cycles or 7200 alternations per
minute.

[Illustration: FIG. 42.—High potential "Humming" transformer.]

[Illustration: FIG. 43.—High potential closed core transformer
for wireless work.]

[Illustration: FIG. 44.—Leyden jar set for oil immersion to prevent
losses from brush discharges.]

From these facts we may readily see why the troublesome interrupter may
be eliminated when alternating current is used. Every time that the
current rises and falls the magnetic field changes.

Considerable care must be used in proportioning the windings so that
they possess sufficient reactance. Reactance is the tendency of a coil
to resist the flow of an alternating current. A reactance coil is
sometimes placed in circuit with an open core transformer to prevent the
spark from arcing. Arcing is the tendency of the spark to pass across
the gap without charging the condenser and creating any high frequency
oscillations.

[Illustration: FIG. 45.—Oil immersed condenser]

The condenser, it will be remembered is the means of storing up the
energy, which suddenly rushing across the spark gap, produces the
oscillations necessary to generate the electric waves. A battery of
leyden jars may be used as a transmitting condenser in connection with
small induction coils. Their objection in large stations is that they
are very cumbersome and some energy is lost by the brush discharges
around the tops of the jars. The usual form of condenser consists of
alternate sheets of tinfoil and glass plates arranged in a pile. The
alternate sheets of tinfoil are connected together to form the terminals
of the instrument. The condenser is usually encased in a wooden box
poured full of wax or oil to increase the insulation and efficiency.
Condensers are arranged in units so that any desired capacity may be
readily secured by adding the proper number of units. The capacity of a
condenser is its relative ability to receive and retain an electrical
charge.

[Illustration: FIG. 46.—Diagram showing construction of condenser.]

The helix is an instrument consisting of copper or brass wire wound
around a frame of hard rubber or seasoned wood. A certain amount of
inductance is necessary in a wireless telegraph circuit in order to
develop high frequency oscillations. Inductance is the property of an
electric circuit by virtue of which lines of force are developed around
it. The helix furnishes the inductance in the circuit or at least the
greater part. Connections are established to the turns of the helix by
means of clips which snap on and off the wires.

[Illustration: FIG. 47.—Tubular condenser.]

[Illustration: FIG. 48.—Helix.]

[Illustration: FIG. 49.—Close coupled helix.]

[Illustration: FIG. 50.—Spark gap.]

[Illustration: FIG. 51.—Circuit showing tuned transmitting system
employing close coupled helix.]

The spark gap is the medium for discharging the aerial and condenser and
setting up the oscillations. It usually consists of a pair of electrodes
supported by suitable standards and so arranged that the distance
between the electrodes can be accurately adjusted. The electrodes
usually take the form of hollow faced cylindrical rods having flanges to
radiate the heat generated and prevent the spark from arcing. Various
metals are used for spark gaps. Silver is probably the best but its
expense is prohibitive. A special hard zinc alloy is most generally
used.

[Illustration: FIG. 52.—Photo of spark gap.]

[Illustration: FIG. 53.—Quenched spark gap.]

[Illustration: FIG. 54.—Diagram of aerial switch.]

[Illustration: FIG. 55.—Photo of aerial switch.]

Spark gaps take other forms, two of which are interesting and important
enough to describe here. The first is the rotary gap.

This consists of a number of small electrodes set around the periphery
of a wheel mounted upon the shaft of an electric motor. Two other
adjustable electrodes are so mounted that the small electrodes on the
revolving member pass between. When the motor is set in operation the
wheel revolves at a high rate of speed interrupting the spark and
causing a peculiar musical pitch to be emitted. A rotary spark gap
almost entirely eliminates the arcing of the spark.

The quenched gap consists of a number of disks of brass about five
inches in diameter having thin mica washers set between and arranged in
a pile as in the illustration. The quenched gap radiates considerably
more energy than any other form of gap and also has the advantage of
being practically noiseless. The crashing discharge of an ordinary gap
produces a very disagreeable penetrating noise hard to eliminate. In
most commercial stations the spark is muffled to a certain extent by
enclosing it in a cylinder of micanite or some other insulating
substance.

[Illustration: FIG. 56.—Anchor gap.]

The aerial switch is necessary for quickly connecting the aerial and
ground to either the transmitting or receiving apparatus. Amateurs very
often employ a small "double pole double throw" switch. The switch used
in commercial stations is built in the manner shown in Fig. 55.

[Illustration: FIG. 57.—Wireless key.]

An anchor gap is a simple little device consisting of a hard rubber ring
bearing two or three small electrodes or sparking points. It is a
necessary part of the transmitting apparatus wherever a loop aerial is
used. One electrode is connected to the transmitting apparatus and the
other two to the opposite sides of the aerial so that the currents
divide between the two halves and equalize.

[Illustration: FIG. 58.—Photo of wireless key.]

The key is a hand operated switch which controls the electric currents
passing through the transformer or coil shutting them on or off at will
and so controlling the electric oscillations in the antenna to send out
short or long trains of ether waves in accordance with the dot or dash
signals of the Morse alphabet.

[Illustration: FIG. 59.—Key and aerial switch.]

The key used in a wireless station is necessarily much larger and
heavier than those employed in ordinary Morse line work, in order to
carry the heavy currents used by the transmitter. In spite of their size
and weight, however, such keys when properly designed may be handled
with perfect ease.

CHAPTER IV. THE RECEIVING APPARATUS.

The receiving instruments form the most interesting and ingenious part
of a wireless station. They are the ears of the wireless station. They
are wondrously sensitive but yet simple and incapable of much
complication. The receiving station forms an exact counterpart of the
transmitter, and the train of actions taking place are the reverse of
those of the latter. The purpose of the transmitter is to change
ordinary electric currents into electrical oscillations and thus set up
electric waves, while the receptor converts the waves into oscillations
and thence into currents which are capable of manifesting themselves in
a telephone receiver. The instruments necessary for receiving comprise a

Detector

Telephone Receivers

Fixed Condenser

Tuning Device

[Illustration: FIG. 60.—Portable receiving set and case.]

Other instruments such as a potentiometer, test buzzers, variometers,
variable condensers, etc., complete the outfit and improve its
selectivity and sensitiveness.

[Illustration: FIG. 61.—Complete receiving outfit.]

The detector forms the most vital part of the receptor. In explaining
its action it may be well to recall and enlarge upon the description
already set forth on page 11, where it was explained that
electromagnetic or as they are more commonly called when identified with
wireless telegraphy, Hertzian waves have the power of exciting
oscillations in any conductor upon which they impinge. Electrical
oscillations, it will be remembered, are alternating currents of very
high frequency. They are generated in the aerial of the receiving
station by the action of the waves coming from the distant transmitting
station. These currents are exceedingly feeble, too feeble in fact to
operate any form of electrical apparatus except a telephone receiver,
which is one of the most sensitive instruments in existence.

[Illustration: FIG. 62.—Portable pack set. The receiving outfit is
contained in the left hand case; also the key and interrupter. The
tubular condenser, spark gap, and induction coil may be seen in the
right hand case.]

[Illustration: FIG. 63.—Complete receiving set, consisting of two
"Perikon" detectors, potentiometer, loose coupler, variable condenser,
etc.]

There are probably more different forms of detector than any other piece
of radiotelegraph apparatus. Those in most common use to-day are the
mineral detectors. A small crystal of certain minerals, iron pyrites,
silicon, galena, etc., is placed between two contact points which are
adjustable so that the pressure may be regulated and the most sensitive
portion of the mineral selected. A telephone receiver is shunted across
the terminals of the detector.

[Illustration: FIG. 64.—Showing construction of a "watch case"
telephone receiver.]

A telephone is shown in diagram in Fig. 64. It consists of a U shaped
permanent magnet of bar steel, so mounted as to exert a polarizing
influence upon a pair of little electromagnets, before the poles of
which an iron diaphragm is mounted. For convenience these elements are
assembled within a small cylindrical casing usually of hard rubber. The
permanent magnet exerts a continual pull upon the diaphragm tending to
distort it, concave inwards. When alternating currents are sent through
the receiver coils, that part of the alternation which is flowing in the
proper direction to form a magnetic field flowing in the same direction
as that of the permanent magnet will strengthen the latter and assist it
in attracting the diaphragm and causing it to further approach the
magnet. That portion of the current flowing in the opposite direction
detracts from the magnetic pull and allows the diaphragm to recede from
the magnet. The diaphragm thus takes up a vibrating motion corresponding
to the electrical waves supplied to the coil and it imparts motion to
the surrounding air, the result being sound.

[Illustration: FIG. 65.—Pickard adjustable telephone receivers for
wireless purposes.]

It might reasonably be asked why a telephone receiver could not be
directly connected to the aerial and ground so that it would respond
directly to the high frequency currents generated by the incoming waves
without the medium of a detector. There are two very good reasons why
such a method would not be possible, the first being that the little
magnet coils contained in the telephone receivers exert a choking action
upon alternating currents of high frequency which effectually blocks
their passage. Low frequency alternating currents, intermittent direct
currents and continuous direct currents will readily pass, producing a
sound-each time there is any change in their value. The purpose and
action of most types of detectors is to act as a valve allowing the
current to pass through in one direction but not permitting it to pass
in an opposite one. The high frequency oscillating currents may be
represented by a curved line crossing and recrossing a zero line and
gradually decreasing in amplitude as shown by A in Fig. 66.

[Illustration: FIG. 66.—Illustrating the valve action of a rectifying
detector.]

[Illustration: FIG. 67.—A new type of silicon detector in which a
crystal of arsenic may be brought to bear against the surface of one
of several silicon crystals.]

The detector, acting as a valve, eliminates one half of the alternating
current so that the result may be represented by B, in reality a
pulsating direct current which rises and falls but is able to flow
through the telephone receiver and produce a motion of the diaphragm
with consequent sound waves audible to the ear.

[Illustration: FIG. 68.—Diagram drawing analogy between rectifying
action of a detector and a pump.]

The accompanying sketches and the following analogy drawn between the
electric currents and the flow of a stream of water may serve to render
a better conception of how it is possible for the valve action of a
detector to rectify an alternating flow, continuously reversing its
direction to an intermittent current passing in one direction only. The
illustration shows two pumps A and B. Each pump is immersed in a pool of
water and consists of a cylindrical tube T and T' having a small
opening, O and O', at the lower end to admit the water and a piston, P
and P', operating up and down inside the tube. Every time that the
piston P is raised in the pump A it will draw in water through the small
hole O. As soon as it descends, however, the water will reverse its
direction and pass out. The action of the water represents that of an
alternating current because it passes in first one direction and then in
the other. The pump B is fitted with a valve whose action is to permit
the water to flow in one direction only. The valve is fitted to the
piston P'. It is a little flap which opens a hole in the piston when the
latter is descending and closes when it is rising. Suppose that the
piston is raised. Water will be drawn in through the little hole O'. As
soon as the piston reaches the limit of the stroke it commences to
descend. In falling it exerts a slight pressure on the valve which opens
and allows the water to pass through. The hole in the piston is larger
than the hole in the pump and so there is almost none of the water
forced back into the pool. The next up stroke of the piston draws more
water in, that which is on top flowing out through the overflow. The
nature of the stream passing through the hole O' is intermittent,
passing principally in one direction. It may be likened to the
intermittent direct current produced by the detector.

[Illustration: FIG. 69.—Pyron detector in which a fine wire is brought
to bear against a crystal of iron pyrites.]

Some of the many forms of detectors are interesting because of the
ingenious manner in which equivalent results are attained. The
illustration shows a type of detector known as the "Perikon." Two
minerals, zincite (oxide of zinc) and chalcopyrites (copper-iron
sulphide), are mounted in adjustable cups so arranged that the surfaces
of the minerals can be brought into variable contact with one another.

[Illustration: FIG. 70.—Perikon detector.]

Another very good rectifying detector is that consisting of a flat
surface of highly polished silicon mounted in a small cup. A flat brass
point mounted on the end of an adjustable thumbscrew is brought to bear
on the silicon.

[Illustration: FIG. 71.—Silicon detector.]

Other mineral detectors of value are the Pyron, molybenite and galena.

[Illustration: FIG. 72.—Electrolytic detector.]

The carborundum detector is a form of crystal rectifier consisting of a
fragment of carborundum held between two carbon blocks.

The electrolytic detector consists of a very fine platinum wire
(.001-.0003 of an inch in diameter) dipping into a small cup of dilute
nitric acid. A large platinum electrode is sealed in the bottom of the
cup so as to make an electrical connection with the liquid. This form of
detector is exceedingly sensitive, probably more so than any other. The
electrolytic detector requires a battery. When a slight current passes
through the circuit, very minute bubbles are formed at the wire,
insulating it from the liquid and thus shutting off the battery current
from the telephone receivers. However, upon the arrival of any electric
waves and consequent high frequency oscillations the latter destroy the
bubbles clustering around the little wire and permit the current to
flow. Upon the cessation of the high frequency currents the bubbles
immediately form again, only to become broken down by each train of
oscillations produced in the aerial. The intermittent currents can be
detected by a buzz in the telephone receivers.

[Illustration: FIG. 73.—Electrolytic detector in circuit.]

The carborundum detector also requires a battery although its action is
somewhat different from that just described.

[Illustration: FIG. 74.—Potentiometer.]

When a battery is used in connection with a detector, an instrument
known as a potentiometer becomes necessary. A potentiometer is simply a
device for accurately adjusting the voltage of a battery to a value
where it will render the detector the most responsive to the incoming
signals.

[Illustration: FIG. 75.—Diagram showing how potentiometer is connected
in circuit.]

The Tuning Coil is a device for accurately adjusting the oscillation
circuits to receive the waves.

Its action may be illustrated to a certain extent by pressing down the
loud pedal of a piano and at the same time whistling a note loudly and
clearly. Listen carefully and some of the wires in the piano will be
heard sounding the note whistled. At each vibration of the note of the
whistle a wave of pressure went forth from the lips and reaching the
wires gave them all a tiny impulse. The impulses followed each other
rapidly at definite intervals giving each of the wires the same push
each time. The wires which are tuned to produce the note on the piano
corresponding to that of the whistle will vibrate energetically enough
to produce a sound themselves. They are the wires to which the impulses
are rightly tuned so that each one adds to the motion it has already
acquired. We all know how a child sitting in a swing may be made to
swing back and forth by giving a succession of little impulses properly
timed. The small pushes are superimposed on one another, the result
being a single large motion.

[Illustration: FIG. 76.—Analogy between swinging and tuning.]

The "impulses" generated in the receiving aerial are exceedingly weak
and in order to produce an effect must be timed so as to follow one
another in proper succession. Tuning devices are for this purpose and by
their means the receiving circuits and instruments may be carefully
adjusted to the same wave length or "note" as the transmitter so that
the high frequency currents in the aerial will arrive at the proper time
to oscillate or surge back and forth to produce the maximum results.

In this way it is possible to convey intelligence over long distances by
the repetition of small impulses without it being necessary to send any
very energetic ones. By arranging the stations so that each one emits
its own definite wave different in period or length from that of the
others it is possible to operate several stations at the same time in
the same neighborhood without interfering with one another. The
apparatus is then said to be selective because the instruments can be
adjusted in a few seconds to receive from any desired station and to
exclude others.

[Illustration: FIG. 77.—Receiving a message in a Marconi transatlantic
station.]

The tuning coil consists of a cylinder wound with bare copper wire
spaced so that the turns do not touch one another. Variable contacts
called "sliders" are so arranged that connection can be made almost
instantly to any desirable turn of wire. The tuning coil is connected to
the aerial and receiving apparatus in the manner illustrated in Fig. 79.
By moving the sliders back and forth the wave length of the system may
be added to or detracted from and any desired "tune" quickly reached so
that it is possible to listen to any station desirable and exclude the
others. The cylinder over which the wire is wound usually consists of a
thick cardboard tube treated so as to be moisture proof. Bare wire is
preferable to all forms of insulated wire. The coil is usually three to
four inches in diameter and eight to twelve inches long.

[Illustration: FIG. 78.—Tuning coil of the double slide type.]

[Illustration: FIG. 79.—Diagram showing fixed condenser in circuit.]

Tuning coils are known as "single slide," "double slide" and "three
slide" according to the number of contacts they are fitted with.

[Illustration: FIG. 80.—Fixed condenser.]

The loading coil is a supplementary tuning coil used to furnish extra
inductance in case it is desirable to obtain a greater range of
resonance or tuning.

It is merely a single slide tuning coil connected in series with the
regular tuning device. It is not always a necessity but is often part of
the equipment when it may be necessary to adjust the apparatus to
receive long wave lengths.

Condensers are devices for collecting and storing electricity. They play
a very important part in both the transmitting and receiving operations.
Condensers and Leyden jars have already been described in connection
with the transmitting apparatus.

The condensers used in receiving are very much smaller in size and
capacity but are the same in principle. There are two general types of
receiving condensers called "fixed" and "variable" accordingly as the
capacity is alterable or not.

Fixed condensers consist of a few sheets of tinfoil interposed between
sheets of paraffined paper or in some cases mica. The condenser is
inclosed in a suitable case, usually a hollow molded block of insulating
composition, and is provided with suitable terminals to facilitate
connection.

[Illustration: FIG. 81.—Rotary variable condenser.]

When a conductor is charged with electricity it has the power of
exerting an opposite charge in any adjacent conductors. The two halves
of a condenser constitute adjacent conductors, the separating medium in
between being called the dielectric. An alternating current will pass
through a condenser because the charge on the plates keeps changing from
negative to positive and back from positive to negative again. A direct
current will not pass through a condenser.

These facts are utilized to considerable advantage in the receptor of a
wireless station. As has already been explained, the high frequency
oscillatory currents will not readily pass through the coils of the
telephone receivers, but a path is provided through the condenser. The
detector rectifies the alternating current into a direct current which
the condenser opposes and forces to pass through the telephone receiver
and produce sounds.

When a battery is used in connection with a detector a condenser is also
necessary to oppose the direct current of the battery and prevent it
from flowing around through the tuning coil instead of through the
detector. The capacity of the condenser may be smaller if the resistance
of the telephone receiver is very great for the reason that as the wire
grows smaller it offers greater impedance to the current. The opposite
also holds true and condensers of large capacity are better fitted for
use with telephone receivers of low resistance.

[Illustration: FIG. 82.—Interior of rotary variable condenser showing
construction.]

Variable condensers are divided into two general types, the "rotary" and
the "sliding" plate, accordingly as the plates forming the condenser are
adjusted with a rotary or a sliding motion. The rotary type consists of
a number of movable semi-circular aluminum plates which swing between a
series of fixed semi-circular plates of a slightly larger diameter. The
plates must not touch one another and move back and forth with perfect
freedom. The dielectric is formed by the air spacing between the plates.

[Illustration: FIG. 83.—Dr. Seibt's rotary variable condenser. The plates
are turned from a solid casting and the separation between is only .01
inch.]

The advantage of an air dielectric is that no losses of energy take
place through hysterisis. Hysterisis is the lagging which takes place in
the process of charging and discharging. A thumb knob is fitted to the
movable plates and provided with a pointer moving over a graduated scale
so that the degree of capacity in use is indicated.

[Illustration: FIG. 84.—Sliding plate variable condenser.]

In the sliding plate type of variable condenser the plates are either
square or rectangular in shape and move back and forth in grooves cut in
a hardwood frame as shown in the illustration.

Variable condensers are used for tuning and adjusting the receiving
circuit in the same way that a tuning coil is employed, namely to
increase or decrease the electrical length of the circuit so that it
will respond to different wave lengths. The condensers are capable of
finer adjustment than tuning coils because the change is gradual and
even and is not in jumps from one step to another as from one turn to
the next turn of the coil. If the desired point of resonance should
happen to come between two wires of the coil and not in a position to be
reached by the slider, the variable condenser can be adjusted to reach
the exact degree of resonance and thus bring the circuit into finer
adjustment than would otherwise be possible. The exact way in which this
is accomplished and the effect upon the circuit will be left to the next
chapter.

[Illustration: FIG. 85.—Diagram showing arrangement of rotary variable
condenser in receiving circuit.]

CHAPTER V. TUNING AND COUPLING, DIRECTIVE WAVE TELEGRAPHY.

Tuning has been mentioned in several places but not explained in any
greater measure than was necessary to render a conception which would
enable the reader to follow the text intelligently in order not to
depart from the subjects under discussion there and consequently defeat
the purpose of clearness.

The great importance and value of properly "tuning" the circuit of
radiotelegraphic apparatus cannot be overestimated and for that reason
the subject can hardly be passed without some further explanation. Its
effects are two-fold. In the first place it is always desirable and
highly important that wireless messages should be, so far as is
possible, selective, inasmuch as there are often several stations in the
same immediate neighborhood operating at the same time. This result is
reached by tuning and it is possible for them all to transmit different
messages at the same time without confusion by the proper arrangement of
the wave length. The second effect is the transmission of messages over
long distances with the comparative consumption of small amount of power
by adjusting the "period" or electrical length of the circuits until the
oscillations "flow in harmony" with each other and resonance is secured.

Perhaps the only way that these results may be made clearly intelligible
is by resort to a graphical example. Suppose that a very heavy weight
were suspended from a chain as shown in the illustration and that it is
struck at regular intervals, once every second, with a hammer.

Every time that the hammer strikes the ball it will give it an impulse
and cause it to swing slightly. If the chain is short, the ball will
swing faster, while if it is long it will swing more slowly. We will
suppose that the ball is struck from such a direction that it starts to
swing over toward A. The ball is so heavy and the hammer so light in
comparison however that the ball does not swing very far and soon
commences a return journey. If it should return to the point B just as
the hammer delivers another blow the force of the blow will be expended
in stopping the ball rather than adding to its motion because they are
both traveling in opposite directions. However if the chain is
lengthened so that it has a period of swing lasting one second, the
succeeding blow will strike the ball after it has reached the point C
and is on its return journey, thus imparting fresh energy because both
the ball and hammer come together at the right time when they are both
swinging together. Proper adjustment of the length of the chain will
make it possible for the hammer to always descend at the right moment to
add its energy and motion to that previously given the ball. The result
will be considerable increase in the amplitude of the swing.

[Illustration: FIG. 86.—Chain and ball arranged to illustrate effect
of tuning.]

From this we may easily perceive how it is possible by shortening or
lengthening the period of an electrical circuit to so adjust it that
resonance is secured and each succeeding oscillation will take place at
the proper time to assist the previous one, not dying away after one or
two surges and becoming what is known in technical language as rapidly
"damped."

[Illustration: FIG. 87.—Loose coupled helix.]

The instruments for accomplishing these things consist as previously
explained, in the case of a transmitter, of the helix and in the
receiving station of various tuning coils and condensers.

[Illustration: FIG. 88.—Hot-wire ammeter.]

Helix and tuning coils are divided into the "inductive" or "loose" and
the "direct" or close coupled types. Inductive tuning coils are known as
"loose-couplers" and "receiving transformers." Inductive helixes consist
simply of two helixes, separated from one another as shown in the
accompanying illustration. The upper helix, called the secondary, can be
raised or lowered upon a central support. Varying the distance between
the primary and secondary is varying the "coupling." There are several
advantages derived by using loose coupled sending helixes, the chief of
which lie in the fact that it is possible to radiate larger amounts of
energy and also decrease the "damping."

[Illustration: FIG. 89.—The principle of the hot-wire ammeter.]

In order to tune a transmitter, the "hot-wire" ammeter is necessary.
This instrument makes use of the property which electrical conductors
possess to become heated and expand when a current is passed through
them.

The accompanying diagram serves to illustrate the principle of the
"hot-wire" meter. A piece of platinum wire is stretched tightly between
two rigidly fixed posts. A thread leads from the center of the "hot
wire" to a small spindle around which it passes once or twice. The
spindle is also connected to a spring which exerts a continual tendency
to turn the spindle but is prevented from so doing by the thread
attaching to the hot wire. Any tendency on the part of the string to
slacken a little, however, will immediately permit the spring to turn
the spindle. When a high frequency current is passed through the
platinum wire it becomes heated and expands. The expansion of the wire
allows the thread to slacken slightly with the immediate result that the
spindle turns. The spindle carries a pointer at the upper end which
shows the amount of turning. It is therefore easy to tell the
comparative strength of current flowing accordingly as the deflection is
great or small.

[Illustration: FIG. 90.—Diagram showing loose coupled helix in circuit.]

The meter is placed in series with the aerial and when the high
frequency currents pass through it they heat and expand a fine wire,
causing the needle to move over a graduated scale and indicate the
amount of current passing. The apparatus is "tuned" or in resonance when
the length of the spark gap, the condenser and the helix have been so
adjusted that the oscillations flow freely through the system and the
maximum amount of current is indicated by the ammeter.

[Illustration: FIG. 91.—Loose coupled tuning coil.]

[Illustration: FIG. 92.—Loose coupled tuner.]

The loose coupled tuning coil consists of two windings wound over two
concentric cylinders, forming a primary and a secondary. The secondary
is the smaller winding and slides in and out of the primary so that the
"coupling" is variable. The primary is adjustable by means of a slider
and the secondary by means of a multi-pointed switch. The slider is
usually connected to the aerial and one end of the coil to the ground.
The detector, etc., are connected to the terminals of the secondary.
Variable condensers may be added with good results to both the primary
and secondary circuits.

[Illustration: FIG. 93.—Diagram showing position of loose coupler
in circuit.]

Loose couplers also take the form of doughnut tuners in which the
secondary revolves instead of slides. The coupling is variable in such
an instrument by simply turning the secondary.

The wave emitted from a transmitter is in reality made up of two waves
of different lengths. The variation in the lengths of these two waves is
dependable upon a factor known as the coefficient of coupling. It is
almost impossible to clearly explain the phenomenon and in order not to
confuse and complicate by a rather lengthy explanation it may be well to
simply state that its effect is to make selective tuning difficult
unless the coupling of the receiving station can be varied to correspond
with that of the transmitter and ask the reader to take it for granted.
Varying the coupling adjusts the difference in the two wave lengths and
when properly accomplished renders the apparatus highly selective.

[Illustration: FIG. 94.–Fort Gibbons, Alaska, wireless station.]

[Illustration: FIG. 95.—Transmitting condenser (molded dielectric).]

Directive Wireless Telegraphy is an interesting phase of this new art
which is receiving considerable attention in the hands of investigators
and has resulted in the devisement of several successful systems for
confining the propagation of the electric waves to certain directions.

[Illustration: FIG. 96.—Braun's method for directing wireless telegraph
signals.]

A general diffusion of waves is often very undesirable for the reasons
that the message may be received by an unfriendly neighbor or enemy and
also because it is wasteful of energy. By so directing the waves that
they may be sent over the earth to any desired point of the compass and
only in that direction, it is possible to communicate without disturbing
another station and also for a vessel at sea to secure its bearings and
position by tuning its apparatus to respond to electric waves from two
different known stations.

The manner in which the problem has been solved varies considerably
according to the inventor. All are interesting and ingenious.

It will be remembered that electric waves possess all the
characteristics and properties of light waves, etc., and may be
reflected, refracted and polarized.

Ferdinand Braun has devised a system consisting of a number of metallic
strips arranged to compose a parabolic surface. Another similar set of
strips below the first set completes the arrangement. The two sets are
connected to the terminals of a spark gap and induction coil. This
apparatus acts as a huge reflector and sends out waves in one direction
only, but however interesting and ingenious it may be is not entirely
practical.

[Illustration: FIG. 97.—Bellini-Tosi radio-goniometer for directive
wireless telegraphy.]

Another method devised by Braun employs two or more aerials at certain
distances apart. The alternating currents used to excite the
oscillations differ in phase, i. e. are so arranged that they have
different comparative values at the same moment. It is possible to send
very strong signals in a direction lying in the same plane as the
aerials. By the use of three or more antennae suitably differing in
their phase of excitation and situated at the vertices of a triangle it
is possible to send strong signals in certain directions only.

[Illustration: FIG. 98.—Arrangement of Bellini and Tosi for directive
wireless telegraphy.]

Messrs. Bellini and Tosi have devised a very ingenious method of
directively transmitting and receiving electric waves as shown in the
accompanying diagrams. The antenna consists of two closed or nearly
closed circuits of triangular shape arranged in two perpendicular
planes. The two aerials each contain a circular coil of wire
perpendicular to each other with their windings in the planes of the
antenna circuits respectively. A third coil is connected to the
receiving apparatus when the messages are incoming and to the condenser,
spark gap and coil when the signals are to be transmitted.

Waves coming in from any particular direction produce oscillations in
the two aerial circuits whose intensity varies according to the
direction in which the waves These currents passing through the coils
generate a magnetic field having a direction perpendicular to that from
which the waves come. The strength of the currents in the movable coil
will depend upon its position in the resultant magnetic field and will
be at a maximum when the coil embraces as many as possible of the lines
of magnetic force.

[Illustration: FIG. 99.—Complete receiving and transmitting outfit.]

By providing the movable coil with a pointer it is possible to thereby
determine the plane in which the station producing the signals lies. Any
ambiguity regarding the final position of the station, whether it is
located in the same direction indicated by the pointer or in the
opposite one, is only removed by general knowledge of the location of
existing stations.

The processes involved in sending messages are the reverse of those
entering into the receiving apparatus. The movable coil being connected
with the condenser, gap and transformer or induction coil creates a
magnetic field which induces oscillating currents in the other two coils
and consequent waves in the aerial whose strongest exertions will lie in
a plane determined by the third coil. Changing the position of the
latter will send the messages in any direction desired.

CHAPTER VI. THE DIGNITY OF WIRELESS. ITS APPLICATIONS AND SERVICE.
WIRELESS IN THE ARMY AND NAVY. WIRELESS ON AN AEROPLANE. HOW A
MESSAGE IS SENT AND RECEIVED.

Wireless telegraphy and that precocious infant, wireless telephony, have
outlived all the speculative and tentative achievements of their early
days and have established themselves in an important and settled
position among our methods of conveying intelligence.

The field has been so greatly enlarged in recent years and the apparatus
and methods so improved that the broadest possible view of its future
development and importance is justified. And there must inevitably come
the time when our merchant marine and wireless service will come under
such reasonable regulation that it will be removed from any dependence
upon stock jobbing wireless telegraph and telephone companies.

[Illustration: FIG. 100.—Special light weight wireless telegraph set
for airship service.]

Official sources show that the equipping of sea-going vessels with
wireless apparatus is progressing at a rapid rate and it is not
difficult in the face of certain facts to appreciate the enormous volume
of business that sooner or later will be handled by wireless. Three
hundred and sixty-three United States naval vessels and about eight
hundred merchant vessels are equipped at this writing. The large number
of commercial shore stations, army forts and posts, and those used by
corporations, isolated stations, etc., for various private purposes
comprise a list which reaches an enormous total.

[Illustration: FIG. 101.—Telefunken wireless cart, showing
transmitter.]

Whatever may have been the status of wireless previous to the Titanic
disaster, it now occupies a position far more important than that taken
merely from any commercial standpoint, for it is no longer merely a
convenience to business or a means of furnishing the latest news for the
entertainment of passengers, but is a life-saving proposition taking its
place with the elaborate and costly systems of railroad signals.

[Illustration: FIG. 102.—Telefunken wireless cart for military service,
showing receiving apparatus.]

[Illustration: FIG. 103.—Telefunken wireless wagon set in operation
at Fort Leavenworth, Kansas. The aerial is of the umbrella type
supported by a steel pole resting on a porcelain base.]

It is a curious fact that many of the most startling and newest
inventions find ready and peculiar application as an aid in modern
warfare. The nerves of every war vessel and fort are the wires of the
telephones, telegraphs, telautographs, dynamos, storage batteries etc.,
that transmit orders by speech or in writing, find the range, fire the
guns, explode the mines and seek out the enemy with a powerful
searchlight.

Every battle-ship, cruiser, etc., of the United States Navy is now
equipped and with the completion of the new ultrapowerful station at
Washington the War Department will be enabled to issue instructions to a
ship no matter where it may be on the ocean or in what harbor it may
lie.

The government maintains an elaborate equipment at the Brooklyn Navy
Yard where the future wireless operators of the Navy are given a course
extending from seven to ten weeks. The first few days are spent in
mastering the theory. The second week usually commences alternate study
and practice of the Continental Code which lasts throughout the entire
course or until thoroughly mastered. Each week some special branch of
study is given out such as repairing and overhauling certain
instruments. At the end of seven weeks the student can usually send and
receive 15 words a minute. He is then given two weeks to prepare for an
examination which if passed rates him as an electrician, third class,
and qualifies him for active work.

[Illustration: FIG. 104.—Wireless room aboard the U. S. transport
"Buford." It is certain that wireless telegraphy and telephony will
be important factors in military campaigns of the future. For coast
defense, wireless is as valuable as on the ocean.]

[Illustration: FIG. 105.—The apparatus set up for operation.]

This method of transmitting army orders is quite dependable. With the
most recent developments and improvements it is now possible to direct
the movements of a great army and navy simultaneously from a centrally
located point.

[Illustration: FIG. 106.—Wireless equipped automobile.]

One of the most interesting and spectacular applications of wireless
telegraphy in military service is the wireless telegraph automobile.

The automobile is a stock pattern touring car of 30 H. P. provided with
a special body arranged to carry six passengers. The seats are elevated
so as to afford storage space below for the entire wireless equipment
and a truly astonishing amount of miscellaneous supplies.

[Illustration: FIG. 107.—Company D Signal Corps at San Antonio Texas,
1911, showing pack sets and telescoping pole carried by pack mules.]

The mast used to elevate the aerial is of light steel construction
divided into eight sections which nest into one another with admirable
economy of space. The socket for the foot of the mast is located in the
center of the tonneau. Only a few minutes are required to raise the mast
and aerial. The same gasoline motor employed to drive the automobile
also drives a small dynamo which supplies the electric current for the
transmitting apparatus.

Two of these cars have been experimentally operated over a number of the
old battle-fields of the Civil War.

[Illustration: FIG. 108.—U. S. Signal Corps pack sets shown open and
closed. Receiving apparatus on the left.]

The tests were made under all sorts of road and weather conditions but
no great difficulty was experienced in establishing communication over
distances varying from 35 to 50 miles.

There is probably no application of wireless telegraphy, however, quite
as picturesque as the combination of wireless and an aeroplane and the
idea of a double seated aeroplane carrying an aviator and a wireless
operator hovering over a hostile country to keep the commanding officer
informed of all conditions and movements of the enemy.

[Illustration: FIG. 109.—The receiving apparatus of the airship
"America" (Wellman expedition).]

The huge dirigible balloon Akron in which Melville Vanniman proposed to
cross the Atlantic Ocean was fitted with wireless equipment in order to
transmit news of the expedition en route to various of the daily
newspapers of New York and London and also in case of an accident or
emergency to summon aid.

[Illustration: FIG. 110.—Interior of the N. Y. "Herald" (O. H. X.)
press station.]

The equipment is interesting because of the peculiar conditions imposed
upon instruments to be used under such circumstances. A three kilowatt
transformer, the latest type of musical rotary gap and a valve detector
were included in the outfit. It was proposed to obtain the necessary
ground connection by trailing a 1200 foot phosphor bronze ground lead in
the ocean. The frame of the balloon was to be used as the aerial. Should
it have become necessary to take the lifeboat which the balloon carried,
a kite would have been raised and by substituting a copper wire in lieu
of a string an aerial provided, and once more a CQ D and its appeal for
aid would have gone vibrating forth through the ether.

[Illustration: FIG. 111.—Operating the U. S. Signal Corps airship
wireless apparatus.]

Several enterprising newspapers have recognized the value of wireless
telegraphy in collecting shipping news and have installed outfits for
the assistance of their reporting bureau. This innovation in modern
journalism has quickly developed into a useful feature of those
publications which have seen fit to adopt it. When the baseball season
is under way every steamship within calling distance wants the latest
baseball scores or sporting results.

[Illustration: FIG. 112.—The N. Y. "Herald" station, showing aerial.]

[Illustration: FIG. 113.—Operator Jack Irwin overhauling the wireless
apparatus for the dirigible balloon "America."]

Railroads have found an auxiliary wireless service to be of the utmost
value in relieving the heavily loaded wire lines between important
centers. During some of the winter storms and blizzards, when miles of
wires were down in all directions, wireless has been the sole means of
communication in certain instances.

The process of sending a wireless message is very simple. The aerial
switch is usually kept in such a position that the receiving instruments
are connected to the ground and aerial so that the operator is always
able to hear any one calling him. We will suppose for illustration that
the land station at 42 Broadway, New York City, wishes to transmit a
message to the steamer "Horatio Hall."

[Illustration: FIG. 114.—Morse code.]

Every wireless station on land or sea has assigned to it two or more
"call letters," which distinguish it from all other stations, and serve
as the key to messages intended for it to receive and when signed to a
message as an indication of its origin. The "call" of the land station
in this case is N. Y., and that of the steamer, J. H.

[Illustration: FIG. 115.—Continental code.]

In order to send the message to the ship, N. Y. throws the aerial into
position for sending. This act also starts the motor generator set
supplying current to the transformer. Pressing the key, the operator
then signals in the telegraph code J. H., J. H., J. H.—M. S. G.–N.
Y.—and gives the "finish" signal. M. S. G. is the abbreviation for
message. The N. Y. operator then throws his switch back into the
receiving position and waits for a reply. If one is not forthcoming
shortly the calling process is repeated.

[Illustration: FIG. 116.—Transmitting equipment of the high power
station at Nauen, twenty-five miles northwest of Berlin, Germany,
showing six induction coils (in the foreground) arranged to charge
the Leyden jars (composed of 360 units).]

[Illustration: FIG. 117.—Duplex receiving apparatus. The set to
the left may be adjusted to receive short wave lengths and that to
the right to receive long waves. When the handle of the "listening"
key, shown in the center of the illustration, is in the center,
the left hand phone of the head set is connected to the instruments
on the left and the right hand phone to those on the right, so
that the operator is always ready to receive either short or long
waves if received. Swinging the key connects both phones to
either set at will.]

As soon as the operator on board the steamer hears the call, he waits
until the finish signal is received, and then responds in the following
manner: N. Y., N. Y., N. Y.—J. H.—O. K., O. K.—G. A.—G. A.—N. Y., J.
H.—and gives the "finish signal." O. K. is the abbreviation for "all
right," and G. A. means "go ahead." Upon receipt of this, the land
station transmits the body of the message, and signs its call and finish
signal. If the steamer understands the message, she replies "O. K.," and
signs.

[Illustration: FIG. 118.—Breaking-in system.]

There are two Codes in general use for wireless telegraph purposes, the
Morse and Continental. It takes about five per cent. longer space of
time to send a message in Continental than it does in Morse, but the
former has the advantage of not containing any letters requiring proper
spacing in order to be recognizable. American coastwise steamers use the
Morse code; transatlantic ships use the Continental code.

One of the greatest disadvantages of most systems of wireless telegraphy
lies in the fact that no arrangement is provided for simultaneously
transmitting and receiving wireless signals. It is usually necessary for
one operator listening to another to have to wait until the finish
signal is given before he can reply or interrupt in case he cannot
understand part of the message, because the receiving apparatus of the
transmitting station is necessarily disconnected from the aerial and the
ground during the period a message is being sent. If it were to be
connected at this time the powerful currents of the transmitter would
rush through the receiving apparatus into the ground without setting up
any very powerful waves in the aerial and seriously injure the delicate
receiving instruments.

The Breaking-in-System is a method of simultaneously transmitting and
receiving wireless signals. This is accomplished by providing the
transmitting key with a second set of contacts, so arranged that when
the key is released between the dots and dashes of the code the aerial
and ground are automatically connected to the receiving apparatus. When
the key is pressed the receptor is automatically cut off. The advantages
of such a system are more or less obvious. When interference or a
misunderstanding occurs the fact can be immediately signaled to the
sending operator, and the message commenced over again.

[Illustration: FIG. 119.—The receiving apparatus of the station at Nauen.
The message is being printed on tape by a recording device.]

CHAPTER VII. THE EAR. HOW WE HEAR. SOUND AND SOUND WAVES. THE VOCAL
CHORDS. THE STRUCTURE OF SPEECH.

On either side of the head, lodged in a cavity which they do not
completely fill, and situated in the midst of a dense and solid mass of
bone, entering into the base of the skull and forming the temporal bone,
are two membraneous bags called the membraneous labyrinth and the scala
media of the cochlea. Each bag is filled with a liquid, and is also
surrounded and supported by a fluid which fills the cavity in which they
are lodged. Certain small, hard bodies, free to move around, lie in the
fluid of the bag. The ends of the auditory nerve of hearing are
distributed around the wall of the sac, so that they are subjected to
the blows of the little particles of calcareous sand, or otoconia, as
they are called, whenever the fluid in the bags is disturbed.

[Illustration: FIG. 120.—Diagram of the ear.]

The membraneous lining on which the ultimate ends of the nerves are
spread is virtually a sensitive beach, and the little otoconia, showers
of pebbles and sand, which are raised and let fall by each succeeding
wavelet of sound. This wonderful mechanism constitutes the inner ear.

The ear, as a whole, consists of three parts: the outer ear, which is a
trumpet-shaped passageway called the pinna serving to collect the sound
waves and pass them on through the auditory canal to a small membrane
called the eardrum; the ossicles, a series of three little bones, the
hammer, the anvil, and the stirrup, they are called; and the inner ear
just described.

[Illustration: FIG. 121.—The ossicles.]

The foot of the stirrup is connected with an oval membrane, which closes
a hole in the inner ear.

Sounds passing through the auditory canal cause the drum to vibrate and
send tremors through the bones to the liquid in the little sacs. The
tumbling of the "pebbles" against the filaments of the auditory nerve
sends the intelligence to the brain.

The impression which the mind receives through the organ of hearing is
called sound.

All bodies which produce sounds are in a state of vibration, and they
communicate their vibrations to the surrounding air and thus set it into
waves, just as a stick waved back and forth in a pool of water creates
ripples.

Sound implies vibration, and whenever a sound is heard some substance, a
solid, a liquid, or a gas is in vibration and the surrounding air is in
unison with it.

[Illustration: FIG. 122.—Bon jour ("good day" in French) as represented
by a wave picture. The picture was made by a mirror arranged to move
under the influence of the voice and to cast a beam of light upon a
strip of sensitized paper.]

Sound has been likened to a picture painted not in the space and color
of substance but in time and motion. What really passes out from the
source is merely a rhythmical motion of the air particles, manifesting
themselves as changes in pressure, spreading out in ever-widening
spheres through the atmosphere. The order of these compressions is
different for every sound. The musical sounds of an orchestra embody a
different set of vibrations for each note of each particular instrument.
If the fluctuations in pressure of a sound wave are irregular and
non-periodic, the sound is called a noise; if they are cyclic, and
follow a regular and sufficiently rapid periodic lag, the sound is
musical.

We may easily satisfy ourselves that in every instance in which the
sensation of sound is produced the body from whence the sound comes must
have been thrown into a state of rapid tremor, implying the existence of
a motion to and fro of the particles of which it consists.

[Illustration: FIG. 123.—Experiment showing sounding bodies are in
vibration.]

If the face of a tuning fork prong be touched with a small ball of cork
suspended from a fine silk fiber, after the fork has been struck and
caused to emit its note, the cork will be violently repelled from the
latter. Why? Because the prong of the fork is in vibration.

If a small wire or bristle is fastened to the prong of the fork and a
piece of smoked glass drawn across it while the fork is giving forth a
sound, the trace of the point will appear as a wavy line, showing that
while the glass was drawn along the prong went to and fro many times.

The vibrations or disturbances set up in the air by a sound emitting
body are known as sound waves. These waves consist of a series of
condensations and rarefactions succeeding each other at regular
intervals, each air particle swinging to and fro in a very short path.

[Illustration: FIG. 124.—Method of registering vibrations of a
tuning fork.]

Air waves cannot be seen by the naked eye, but their nature may be
easily represented or illustrated. Fig. 126 gives a pictorial
representation of the crowding together of the air particles during the
passage of a wave. The loudness of the sound depends upon the amount and
suddenness of the change in pressure, and the note or pitch on the
number of complete to and fro motions of the particles per second.

[Illustration: FIG. 125.—Wavy line made by a bristle attached to a
tuning fork prong in vibration when passed over smoked glass.]

The timbre of a sound or the quality that distinguishes the note of a
violin from that of a piano depends upon the smoothness or abruptness of
the changes in pressure. Therein lies the difficulty of the production
of sound by means of a phonograph or telephone, for the sound waves must
resemble each other in every detail in order that the result may be like
the original.

[Illustration: FIG. 126.—Illustrating the action of air waves.]

The mechanism with which we speak or sing is composed of two flexible
membranes, stretched side by side across a small cylindrical box located
at the top of the windpipe. The membranes are called the vocal chords,
and the box the larynx. The chords are so arranged and controlled by
muscles that their tension may be changed at will. In breathing, the air
to and from the lungs passes freely between the chords. When the
controlling muscles are tightened, so as to stretch the chords, the
edges are also brought parallel and quite close to each other. If the
breath from the lungs is then forced through the narrow slit between
them, they vibrate like the reed of a musical instrument, and produce
the sounds of the voice. The multitude of sounds which it is possible
for a human being to produce are the result of various degrees of
stretching of the vocal chords, together with the movements of the
mouth, lips and tongue.

[Illustration: FIG. 127.—The vocal cords in position for making a
sound.]

[Illustration: FIG. 128.—The vocal when relaxed.]

Speech is the sound produced by the vocal chords of a human being,
modified by the movements of the lips, tongue, and cavity of the mouth.
The consonants are made by movements of the tongue and lips obstructing
the sounds at their beginning or end, while the vowels are formed by a
steady voice modified by the resonance of the different shapes or sizes
given the parts of the mouth. The waves produced in this manner are
transmitted to the ear, and the sensation of sound is caused by the
impact of the otoconia against the auditory nerve, giving a series of
impressions, musical or unmusical, pleasing or displeasing, as the case
may be. Many interesting experiments showing the nature of the sounds of
the human voice may be performed by means of a simple apparatus invented
by Koenig of Paris. A box is separated into two compartments by a rubber
membrane. Gas is led into one of these compartments by a rubber tube,
and then allowed to issue to a burner. The other compartment is
connected to a megaphone.

[Illustration: FIG. 129.—Koenig's manometric flame apparatus.]

[Illustration: FIG. 130.—Appearance of manometric flames in a revolving
mirror.]

Two pieces of mirror are arranged so as to revolve in front of the
lighted jet or burner. When the human voice is produced in front of the
megaphone, the air waves strike the membrane and cause changes of
pressure in the gas. The height of the flames varies with each change in
the pressure, and when viewed in the mirror resemble a band of light
having an edge like a saw. The teeth are faithful representations of the
changes in the voice, and immediately take on a new appearance when a
new sound is emitted. The shape of the teeth changes with the tone, and
the number of teeth with the pitch. Fig. 130 shows the flames produced
by singing the sound oo, as in tool. The same sound an octave lower in
pitch will show as in B, where there are just one-half as many teeth or
vibrations. The sound of oo is a simple sound. If o on the note is sung
into the megaphone, the image in the mirror will appear like that shown
by C, being made up of alternating large and small teeth, the former
corresponding to every alternate vibration of the octave of the higher
sound coinciding with a vibration of the octave below.

[Illustration: FIG. 130 a.]

The sound causing the flame to appear, as in D, is made up of two simple
vibrations combined.

CHAPTER VIII. THE TELEPHONE TRANSMITTER AND RECEIVER. THE PHOTO PHONE.
THE THERMOPHONE. THE SELENIUM CELL. THE SPEAKING ARC.

The telephone is an instrument for the transmission of sounds to a
distance by the agency of electricity, wherein the speaker talks to an
elastic plate of thin sheet-iron, which vibrates and transmits its every
movement, electrically, causing it to vibrate in an identical manner and
emit the same sounds.

The transmission of the vibrations depends upon well known principles of
electricity, and consists, not of an actual transmission of the sounds,
but the passage of electric waves, or impulses, which keep perfect
accord and agree in phase and period with the atmospheric waves produced
by the voice. These in turn, through the medium of an electromagnet,
cause vibrations of a plate or membrane, which agitates the air in a
manner similar to the original disturbance, and thus emits sounds.

The parts of the apparatus which take up the sound waves and change them
into electric currents compose the transmitter. In the form of
transmitter most commonly used, the motions of the diaphragm cause
variations in the strength of a current flowing from a battery by
varying the resistance in the path of the electric current.

The sounds are directed to the mouthpiece, which causes the vibrations
of the air to strike the diaphragm, on the back and center of which is
fastened a small cup shaped piece of carbon. A second cup is mounted in
a rigid position directly in back of the first. The space between is
filled with small polished granules of carbon.

[Illustration: FIG. 131.—Diagram of a telephone transmitter.]

When these are in a perfectly free and loose state their resistance to
an electric current is very great, and they allow almost none to flow.

When slightly compressed their resistance is greatly lowered, and they
permit the current to pass. The vibrations of the diaphragm exert a
varying pressure upon the granules, with a corresponding variation in
their resistance and the amount of current flowing.

[Illustration: FIG. 132.—Diagram showing the principle and
construction of the telephone receiver.]

The receiver, as has already been explained, consists of a thin iron
disk, placed very near but not quite touching the end of a small bar of
steel, permanently magnetized, about which is wound a coil of fine
insulated wire. The ends of this coil are connected to the wires leading
from the transmitter and battery. The varying currents of electricity,
produced by the transmitter, generate corresponding changes in the
magnetism of the receiving instrument, and thus, by alternately
attracting and repelling the diaphragm, cause it to vibrate and emit
sounds.

[Illustration: FIG. 133.—The photophone.]

Alexander Graham Bell, the ingenious inventor of the telephone, with the
aid of Sumner Tainter was the first who achieved success in the attempts
to transmit speech without the aid of connecting wires between the
source of intelligence and the receptor.

In 1873 Willoughby Smith announced that the element selenium possesses
the abnormal property of changing its electrical resistance under the
influence of light. Bell and Tainter took advantage of this discovery,
and devised selenium cells, in which selenium is formed into narrow
strips between the edges of broad conducting plates of brass. The
resistance of the cell in the darkness is approximately twice the
resistance when illuminated.

[Illustration: FIG. 134.—Photophone receiving apparatus.]

[Illustration: FIG. 135.—Photophone transmitting apparatus, using
acetylene flame to furnish light.]

This property of the cell was immediately applied to the construction of
the photophone, an instrument which transmits sounds to a distance by
means of a beam of light reflected to a distant spot from a thin mirror
thrown into vibration by the voice. Over fifty different forms were
devised but the most successful consisted of a transmitter composed of a
glass disk, silvered to reflect a pencil of light focused from the sun,
or an arc lamp. This glass disk was used as a diaphragm similar to that
of an ordinary telephone transmitter, except that the rear side of it
was made free to reflect the beam of light. Bell used for this purpose
disks about two inches in diameter and the thickness of ordinary paper.
The receiver consisted of a parabolic reflector, with a selenium cell
placed at its focus. In series with the cell was placed a battery and
telephone receiver.

When the membrane was set into vibration by the sound waves, it became
alternately concave and convex, the normally parallel rays of light
correspondingly converging and diverging. The receiving station was thus
under the influence of light rays of rapidly varying intensity in
perfect phase with the vibrations of the voice. The reflector
concentrated the rays on the selenium cell, and their varying strength
changed its resistance and caused a pulsating current to flow through
the receiver and reproduce the speech produced at the transmitter.

In another arrangement employed by Bell and Tainter, they used the rays
of a powerful electric arc lamp, and by varying the electric current
supplying the arc caused the light to fluctuate and produce the same
results at the receiver.

These ingenious inventors also devised a method of transmitting speech
called the thermophone. The transmitter remained the same as in the
photophone–a thin silvered membrane, or glass diaphragm, stretched
across the back of a mouthpiece, and arranged to reflect the rays of the
sun, or the light of an arc lamp.

The receiver was a small glass bulb containing a plate of mica covered
with lampblack, or little charred pieces of cork. The glass bulb was
placed in the focus of a reflector, which collected the rays and
concentrated them. The variations in the intensity of the heat
radiations caused the air in the bulb to expand or contract with each
vibration. Rubber tubes extended from the bulb to the ears of the
observer, and the pulsations of air, traveling through the tube as sound
waves, would strike the ear-drum and reproduce the speech.

[Illustration: FIG. 136.—Powerful searchlight arranged to transmit
speech over a beam of light.]

Both of these methods were later very much improved by the employment of
Koenig's manometric flame in place of the silvered mirror as a
transmitter. As explained in the last chapter, speech delivered into the
mouthpiece causes the gas to become compressed or rarefied in direct
accordance with the sound waves, and the flame rises and falls with a
rapidity too great to be detected by the naked eye. These rapid
alterations in the intensity of the illumination of the flame act on the
selenium cell, and reproduce the original voice perfectly in the
telephone receiver.

[Illustration: FIG. 137.—The Electric arc.]

It is obvious, however, that such methods as these are only capable of
transmitting speech over very limited distances, and if greater ranges
are to be traversed much more powerful transmitters must be employed for
the purpose.

Ernest Ruhmer, after long and laborious researches, finally succeeded in
transmitting speech many miles by taking advantage of the speaking arc,
discovered by Simon, who observed that an arc lamp gave out a loud
rattling noise if its current supply was interfered with. An electric
arc consists of two carbon rods, connected to a generator. When the
carbons are brought into contact for a moment and then drawn apart to a
short distance, a kind of electric flame or arc is produced between the
points of carbon, and a brilliant white light is emitted by the white
hot points of the carbon electrodes.

Ruhmer immediately made the arc serve as a telephone receiver and speak
by utilizing the pulsating current of a telephone transmitter to vary
the current supplying the arc.

[Illustration: FIG. 138.—Circuit showing how a singing arc is arranged.]

The arc could thus be made to sing, whistle or reproduce music and the
human voice perfectly, if the sounds were clearly conveyed into the
transmitter. Further investigations showed that every alteration of
current caused by the action of the transmitter also caused an
alteration in the intensity of the light and radiation of the lamp. The
speaking arc could therefore be used as a perfect photophone transmitter
by directing the rays toward the receiving station with the aid of a
parabolic reflector.

In 1902 Ruhmer performed a series of experiments in Germany on the
Wannsee, near Berlin. A large motorboat, the Germania, was fitted with
an electric searchlight connected with a microphone, so as to form a
speaking arc. The receiving station was located on the shore, so that
the distance between the stations could be easily enlarged by moving the
boat.

The receptor was an ordinary selenium cell, placed at the focus of a
large reflector and connected with a telephone receiver and battery. No
difficulty was encountered in reproducing the speech over varying
distances up to about three miles.

CHAPTER IX. THE WIRELESS TELEPHONE.

The applications of any of the wireless telephone systems thus far
described are very limited, for at the best they only operate under the
most favorable conditions, and then over rather limited distances. In
the case of any system whereby the speech must be transmitted over a
beam of light, the great resulting limitations are that the transmission
can only take place in a straight line over water or clear country, and
that stormy weather or a fog will interrupt communication.

None of these objections are present, however, when recourse is had to
Hertzian, or electromagnetic waves. Wireless transmission of speech has
therefore followed in the wake of wireless telegraphy, and the methods
and apparatus employed are very similar.

Some who have followed the text closely might reasonably ask why it
would not be possible to establish wireless telephony by simply
connecting a telephone transmitter in some manner to an ordinary
wireless telegraph, and by directing speech into the latter, vary the
strength of the oscillations emitted.

Such a system, at first thought, seems very plausible, and many
experimenters have devised countless methods trying to attain this
result, only to meet with ultimate failure. The reason is very simple.

Suppose that an induction coil, having a high-speed interruptor, and
therefore able to produce a very rapid stream of sparks at the gap, is
connected to the aerial and ground in the usual manner and a telephone
transmitter placed in series with the ground wire. When the coil is set
in operation the sparks jump across the gap, each spark setting up a
train of oscillations. If speech is conveyed into the transmitter, the
resistance in the path of the oscillations will be varied and
correspondingly also the strength of the waves emitted. The sounds will
be reproduced to a certain extent by the receptor. Whistling, certain
musical tones, and words containing many vowels are sometimes heard in
the receptor, with sufficient distinctness to be recognizable. The voice
cannot, however, be heard at all times, and the system is of no real
value other than an interesting experiment.

[Illustration: FIG. 139.—A "logical" form of wireless telephone which
is impracticable.]

[Illustration: FIG. 140.—De Forest wireless telephone equipment.]

The reason is very simple and readily explained. For the sake of
clearness we will suppose that the speed of the interruptor attached to
the coil is 100 per second. It will therefore produce 100 sparks per
second at the spark gap if the electrodes are close together. The
passage of the sparks is not continuous, each one only occupying a very
small space of time. The pause between each is very distinct, although
it could not be detected with the naked eye. The ten straight lines in
Fig. 141 represent ten sparks which cover a period of one-tenth of a
second, since they pass at the rate of 100 per second. Each spark
produces a train of oscillations, which surge back and forth in the
aerial, rapidly dying out, however, or becoming damped in the manner
already explained.

[Illustration: FIG. 141.–Wireless telephone receiving apparatus
(induction method).]

[Illustration: FIG. 142.—Fessenden wireless telephone transmitting
phonograph music.]

It may now readily be realized that there are long pauses between the
sparks when there are no oscillations in the aerial, and, consequently,
no electromagnetic waves passing between the transmitter and receptor
during those periods.

The wavy line, C, represents the vibrations of the human voice when
producing speech. Part of it has been represented by a continuous line,
and part by a dotted line. The portions represented by the dotted line
occur when there are no oscillations in the aerial, and consequently
these portions are not transmitted. The continuous portions are the only
ones reaching the receptor. Literally, there are "holes in the voice,"
and the result is a jumble of sounds, sometimes bearing a resemblance to
speech, but usually untranslatable.

[Illustration: FIG. 143.—Diagram illustrating the reason why damped
oscillations will not carry the voice.]

The fault lies in the method of producing the oscillations which are
damped and therefore do not exist continuously. If they could be made to
keep on swinging and at a sufficiently high speed so that their tone
would be inaudible and not confuse the speech, the problem would be
solved. In other words, three things are necessary for the successful
operation of a wireless telephone.

1.  A means of producing and radiating a stream of undampened electrical
    waves sufficiently continuous to transmit the upper harmonics of the
    voice, on which the quality and recognition of the speech depends.
2.  Means for varying or modulating the stream of electrical waves in
    accordance with the sound waves.
3.  A receiver, continuously responsive and capable of corresponding
    with sufficient rapidity to the speech harmonics.

In order to obtain the desired result, recourse is had to an arc lamp as
a generator of undamped high frequency oscillations.

When an arc is properly connected with a condenser and an impedance coil
it will emit a musical note. The note is due to rapid changes in the
arc, a very important factor which led to its recognition as a a value
in wireless telephony.

[Illustration: FIG. 144.—How the sound waves of the voice are impressed
upon undamped oscillations.]

When the condenser and inductance are shunted across an arc supplied
with direct current, the condenser immediately becomes charged, and the
current through the arc is diminished. The potential difference across
the latter is therefore instantly increased, tending to further charge
the condenser. This increase of charge reacts on the arc, increasing its
current. The condenser discharges, through the inductance coil, and
becomes charged in the opposite direction, just like a spring, which
released, goes beyond its normal position and then returns.

The operation is repeated many times per second (usually over
1,000,000), setting up persistent undamped oscillations.

[Illustration: FIG. 145.—Arrangement of the speaking arc.]

Perhaps a better conception of how it is possible for a continuous
current, such as that which supplies the arc, to change into alternating
current, vibrating backward and forward, may be gained by comparison
with the steady forward motion of a violin bow, which produces a to and
fro motion of the strings.

[Illustration: FIG. 146.—Diagram showing how a wireless telephone
transmitting system is arranged.]

It was later discovered by Poulsen that if one of the arc electrodes was
kept cool by making it of copper and passing water through it that the
efficiency was greatly increased. A further improvement was obtained by
burning the arc in an atmosphere of coal gas or hydrogen. By surrounding
the arc with a powerful magnetic field, its resistance is greatly
increased and the voltage raised.

[Illustration: FIG. 147.—Poulsen wireless telephone equipment. The
condenser shunted around the are usually consists of a number of metal
plates, placed above one another in a tank of insulating oil. The
inductance is simply a single helix or bare wire.]

By connecting a telephone transmitter to the arc in the same manner that
it is connected to the speaking arc, the oscillations can be varied in
accordance with the vibrations of the voice. The apparatus is connected
to the aerial and the earth through the medium of a loose-coupled helix,
formed by providing the helix in series with the arc and condenser, with
a secondary winding.

[Illustration: FIG. 148.—The Majorana wireless telephone transmitter.]

The ordinary carbon transmitter, in its common form, is unsuited for
wireless telephonic work, on account of its inability to handle large
amounts of power. Many modifications have been designed, the usual
procedure being to make it on a larger scale.

One of the most interesting forms, and also probably the best, is that
devised by an Italian inventor, Majorana.

Its action will be clear from the illustration. T is a tube in which
water or some other liquid is allowed to flow in the direction of the
arrow. The bottom of the tube is contracted so that the stream will
issue in a fine jet. The tube is made of strong, rigid material, except
at one point, D, where an opening is covered with a thin elastic
diaphragm. This diaphragm is connected by means of a short rod to a
second diaphragm, which is provided with a mouthpiece. The water
normally flows out of the jet in a smooth, unbroken column, breaking
into drops at about the point A. As soon as it is disturbed in any way,
however, the distance from the outlet of the tube and the point where
the drops commence becomes shortened. The vibrations of the voice,
thrown into the mouthpiece and striking the diaphragm, are transmitted
to the membrane through the medium of the little rod, and so cause
corresponding changes in the pressure of the fluid in the tube. Each
variation or disturbance in the pressure increases or decreases the
length of the stream before it breaks into drops.

A pair of fine wires are inserted in the stream where the contractions
are the strongest.

Connection is established between the wires by the liquid. If the stream
is narrow its resistance will be greater than if it were expanded at
that point. The contracted portion of the liquid will jump up and down
with the vibrations of the voice, and thus alter the amount of current
flowing.

The receiving apparatus consists of some form of detector and a
telephone receiver and battery. The usual form of detector employed is
the electrolytic. The currents generated in the receiving aerial by the
incoming waves vary in amplitude with those of the transmitting aerial,
and, being in perfect accordance with the vibrations conveyed into the
transmitter, cause the detector and telephone transmitter to reproduce
the speech perfectly.

Experiments in wireless telephony have developed an interesting type of
detector, known as the "Audion." This consists of a six-volt,
low-candlepower, incandescent lamp, having a small, nickel plate
fastened a short distance from the filament, and a "grid" bent from wire
placed midway between the two. When the filament is lighted from a
battery, it throws off a stream of extremely small particles charged
with electricity and called "ions."

These ions pass through the grid and discharge against the plate. When
the aerial is connected to the "grid," and the plate to the ground, the
stream of ions carries that part of the alternating current in the
aerial which flows in the same direction, across, but does not allow the
current tending to pass in the opposite direction. In reality it is a
valve, or "rectifier," opening one way and closing the other; thus
changing the current into an intermittent, direct current, capable of
manifesting itself in a telephone receiver.

[Illustration: FIG. 149.—Showing the brush discharge from a Marconi
transatlantic aerial at night.]

The Audion is a very sensitive device, and is much employed for wireless
telephone purposes.

With such a system it has been found possible to transmit speech and
music to a distance of two hundred miles. In fact, even greater
distances have been covered, and there does not seem to be any good
reason why it is limited to any range.

Transmission by wireless telephone is considerably more distinct than by
wire line, and the fine inflections of the voice are brought out much
better.

Unlike the ordinary line telephone, no rumbling or roaring noises are
heard which confuse the speech, and there is absolute silence in the
wireless telephone receiver, except when talking is going on. Any noises
or sounds produced in the transmitting station, such as walking about
the room, or the breathing of the person speaking into the transmitter,
are reproduced faithfully at the receiving station many miles away.

CHAPTER X. REMARKS. THEORY. ACCOMPLISHMENTS. MAXWELL'S HERTZ'S DISCOVERY.
THE FUTURE.

The history of wireless telegraphy and telephony is a striking example
of how it is possible for scientists laboring in the field of pure
research and stimulated by accumulated knowledge and imagination to
arrive at discoveries of the most vital importance. Heinrich Hertz and
Clerk Maxwell in experimental effort to attain other results unwittingly
laid the foundation of this art.

In 1867 Maxwell proposed the theory that light is not mere mechanical
motion of the ether, but consists of electrical undulations. These
undulations are partly magnetic and partly electrical. Moreover,
according to the theory, the phenomena of electromagnetism and also that
of light are due to certain modes of motion in the ether, electric
currents, and magnetism, being due to whirls, or body displacements in
the substance of the ether, while light is due to vibrations to and fro.

Twenty years later Hertz discovered the most convincing experimental
proofs of Maxwell's wonderful theory, and succeeded in producing
electromagnetic waves in such a manner that their propagation through
space could be examined, and it readily showed that while they were much
longer than the ordinary waves of light, they possessed the same
properties, were capable of being reflected, polarized, refracted, etc.,
and traveled at the same speed.

The waves that Hertz produced are the electromagnetic or Hertzian waves
of radiotelegraphy.

Many thousand commercial wireless stations dot the face of the earth.
Daily time signals, weather reports and storm warnings flash to ships
far out in the ocean from government observatories. Late at night, in
the midnight hours, when the world is asleep, powerful land stations
commence to whisper press dispatches, and the next morning the ocean
daily, containing the same news as our morning paper, is laid on the
breakfast table of the ocean greyhound. A distress signal sends revenue
cutters scurrying along the coast, and brings rescue to hundreds of
imperiled lives. The Navy Department issues an order, and a few minutes
later it is in the hands of the commanding officer of a fleet, a
thousand miles away. Wireless links two continents across a table, and
yet this wonderful apparatus is so simple that a sixteen-year-old boy
can build instruments with a little guidance and listen to a far-distant
station, 1,500 miles away, spell out its news.

[Illustration: FIG. 150.—An amateur wireless telegraph station.]

[Illustration: FIG. 151.—The high-power Naval wireless telegraph
station under construction at Washington, D. C.]

Wireless telegraphy is part of the established order of things. The
wireless telephone is practical for limited distance, but is not a
commercial rival of the telegraph. Great distances are claimed, but they
are matters for proof and speculation.

There is no immediate possibility that wireless telephony will take the
place of local exchanges. If the time ever does come that it in any way
tends to supplant the line telephone for some uses, it is more than
probable that each subscriber must have his own generating station and
call up direct.

There is a very decided field of opportunity for wireless telephony for
long-distance work. The present systems of long-distance wires are very
expensive to construct and maintain, and are subject to the whims of
storms and the elements.

Wireless telephones will not only transmit the speech more clearly and
distinctly, but have the further advantages that the initial cost is
very much lower than that of wire lines, the maintenance is almost nil
in comparison, the depreciation is smaller, the number of employees
required is less, and a break-down is limited to the inside of the
station, where it could be quickly remedied by the substitution of a
duplicate spare piece of apparatus.

Furthermore, no franchises or rights of way would need to be purchased.
No serious difficulty would be encountered because of interference.

Wireless telephony, like wireless telegraphy, but to an even greater
extent, is peculiarly suited for the conveyance of marine intelligence.
Wireless telephony occupies a unique position in this regard-no operator
is required. The additional expense of an operator is an objection to
the wireless telegraph in many cases, and forbids its installation.
Anybody can operate the wireless telephone. It is also much
quicker-words can be spoken more rapidly than they can be put into Morse
signals and translated.

[Illustration: FIG. 152.—--The curved lines represent the radius of
the government high power wireless stations and show the zones over
which direct communication may be had with ships.]

[Illustration: FIG. 153.—The aerial system of a transatlantic station.]

The wireless telephone enables a passenger on board ship to communicate
direct with his home by relaying the message over the line wires. By the
same means the captain of a ship can call his home office and
communicate with the owner of the vessel.

Telegraphs and telephones are the nerves of the world, carrying swift
messages from its brain centers to its hands, annihilating distance in
thought. All differences between men as individuals and people as
nations can be traced to the lack of close contact. Reduce or annihilate
all distance in thought and action, and mankind would possess unbounded
opportunities for peaceful economic and healthful development. No force
more vital than the possibilities of wireless has ever presented itself
or could be demanded to attain such an end. Such a statement, in the
light of actual developments, might even be considered conservative, and
is neither absurd nor the dream of a vivid imagination. The greatest
obstacle to all efforts in radically new directions is the resistance of
the human race. The antagonism of prejudice and skepticism can only
disappear when the world as a whole grasps a new proof and learns to
appreciate it. Inertia must be overcome, and the great masses set to
thinking and striving toward an end before the aweing genie finally
bursts forth and amazes the Aladdins of science.

Within the memory of older men and women are primers of science, which
speculate about the developments of electrical force, and guardedly
discuss its possibilities.

And now, electricity—this mysterious agent-has multiplied the muscular
strength of man a billion times. The tasks of Hercules are now but
chores to be accomplished by the closing of a switch. Mighty rivers roar
through intake and turbine to drive the wheels of industry in a distant
city and turn the night into day. Any attempt to chronicle all the
applications of this wondrous power would be absurd. Such is electricity
to-day.

Only a few years ago Langley launched his famous aerodrome over the
waters of the Potomac, while the world stood by and sneered, ridiculed a
man whose work is now one of the classics of aeronautical literature,
and scoffed at a machine whose principles embodied the conclusions of
years of careful thought and scientific effort.

A decade later and aeroplanes have become a living reality. A man and a
little frame of sticks and canvas can throw off the fetters of gravity
and go soaring dizzily two miles up into the blue sky, and daring more,
come skimming and diving back to earth with motor dead. Such wonders
only came to pass, however, when numbers of men accepted the problem as
one to be solved by trying, and bent their energies toward its solution.
Science has not reached the limits of its resources. It never will. The
art of wireless may always be embarrassed by novelty in many directions.

[Illustration: FIG. 154.–Fong Yee, a Chinese amateur wireless operator
at Oakland, Cal., who is also an aviator and has been summoned home by
the republican Chinese government to demonstrate apparatus of his own
invention to the Chinese army.]

One of the greatest steps forward toward the day when methods and
appliances regarded as permanent as the mountains will pass and be
considered only as the curious remnants of a cruder age is the interest
of 200,000 wireless amateurs in the United States. Some of these will
develop into men who will bring some of the wonders of the future to
their full fruition.

[Illustration: FIG. 155.—Tesla world power plant (experimental
station).]

What is this great change that can be coolly and precisely forecast?
Along what lines will these wonderful developments come? The answer is
"wireless"-not the wireless of a Marconi or a De Forest, but the
wireless of a Tesla--of "high potential magnifying transmitters"-of
"nodes" and "loops"--of oscillatory currents that leave their conductors
behind-the "wireless" of the day when a system is introduced enabling
any person to reach any other on the globe, not simply through a spoken
word or thought conveyed, but visually a perfect transmission of images
which will enable one person to see another, as though that other were
by his side-"wireless" of a time when the great operations of commerce
and industry will be vitalized by huge wireless power stations, turning
the machinery of factories, lighting cities, or sending swift aeroplanes
and ships darting to the farthest points of the earth.

Of course, there may be something of the dramatic in such assertions,
but they are founded upon scientific facts, and, if imaginary, are
scientifically imaginary. The wonderful mysteries of oscillatory
currents, whose natural medium is the ether, currents which object to
being confined to wires and cables, and defy all ordinary laws; currents
that will melt masses of metal with the violence of an explosion, but
yet pass through the human body without producing any sensation;
currents that will instantly manifest themselves 2,000 miles away from
their source, with no visible means of propagation, are the open sesame
to the treasures of a wonderful future.

There are many places in the world where water power is available
capable of generating almost unlimited electrical energy. The present
difficulty lying in the way of its utilization is the limitation of
electrical transmission by wire, for not only is the cost of long lines
of copper tremendous, but power can only be carried in this manner for
limited distances. Central distributing wireless power stations could
send the power of Niagara, which alone might be made to supply a fifth
of all the power in the United States, and the energy of Victoria to the
ends of the earth with little loss. The Great Falls of Zambesi, in the
heart of Africa, could be made to run the subway trains, the factories,
lights, railroads, ferries, trucks, heaters, etc., in that vast, most
complex, most bewildering and inspiring city of the Western World, the
City of New York. Ocean vessels would no longer carry thousands of tons
of coal, locomotives would not wheeze and cough a trail of soot and
smoke through the country, chimneys would cease to belch, and aeroplanes
would travel silently and swiftly overhead.

[Illustration: FIG. 156.—Twenty-five foot sparks from a Tesla
transformer.]

It is easy, in the face of certain facts, to conjure up situations which
would be pleasant and make for the betterment of the world. Any one
whose imagination is vivid enough can make a prediction, but when the
great truth is accidentally revealed, or experimentally confirmed, as
the case may be, and rendered absolutely sure of accomplishment, will
its incalculable consequences continue to baffle the imagination and
carry us further into the land of wonderment? Only the future knows.

THE END.



BOOKS FOR HOME STUDY

OPPORTUNITY

PRACTICAL SCIENTIFIC

TECHNICAL

EACH BOOK IN THIS CATALOGUE IS WRITTEN BY

AN EXPERT AND IS WRITTEN SO YOU

CAN UNDERSTAND IT

THE NORMAN W. HENLEY PUBLISHING COMPANY

Publishers of Scientific and Practical Books 132 Nassau Street

New York, U. S. A.

Any book in this Catalogue sent prepaid on receipt of price.


CATALOGUE OF GOOD, PRACTICAL BOOKS

AUTOMOBILE

THE MODERN GASOLINE AUTOMOBILE-ITS DESIGN, CONSTRUCTION, MAINTENANCE AND
REPAIR. By VICTOR W. PAGE, M. E. The latest and most complete treatise
on the Gasoline Automobile ever issued. Written in simple language by a
recognized authority, familiar with every branch of the automobile
industry. Free from technical terms. Everything is explained so simply
that anyone of average intelligence may gain a comprehensive knowledge
of the gasoline automobile, The information is up-to-date and includes,
in addition to an exposition of principles o construction and
description of all types of automobiles and their components, valuable
money-saving hints on the care and operation of motor cars propelled by
internal combustion engines. Among some of the subjects treated might be
mentioned: Torpedo and other symmetrical body forms designed to reduce
air resistance; sleeve valve, rotary valve and other types of silent
motors; increasing tendency to favor worm-gear power-transmission;
universal application of magneto ignition; development of automobile
electric-lighting systems; block motors; underslung chassis; application
of practical self-starters; long stroke and offset cylinder motors;
latest automatic lubrication systems; silent chains for valve operation
and change-speed gearing; the use of front wheel brakes and many other
detail refinements. By a careful study of the pages of this book one can
gain practical knowledge of automobile construction that will save time,
money and worry. The book tells you just what to do, how and when to do
it. Nothing has been omitted, no detail has been slighted. Every part of
the automobile, its equipment, accessories, tools, supplies, spare parts
necessary, etc., have been discussed comprehensively. If you are or
intend to become a motorist, or are in any way interested in the modern
Gasoline Automobile, this is a book you cannot afford to be without
Nearly 600 6 x 9 pages—and more than 500 new and specially made detail
illustrations as well as many full page and double page plates, showing
all parts of the automobile. Including nine large folding plates. Price
$2.50

BALLOONS AND FLYING MACHINES

MODEL BALLOONS AND FLYING MACHINES. WITH A SHORT ACCOUNT OF THE PROGRESS
OF AVIATION. By J. H. ALEXANDER. This book has been written with a view
to assist those who desire to construct a model airship or flying
machine. It contains five folding plates of working drawings, each sheet
containing a different sized machine. Much instruction and amusement can
be obtained from the making and flying of these models. A short account
of the progress of aviation is included, which will render the book of
greater interest. Several illustrations of full sized airship and flying
machines of the latest types are scattered throughout the text. This
practical work gives data, working drawings, and details which will
assist materially those interested in the problems of flight. 127 pages,
45 illustrations, 5 folding plates. Price $1.50

BRAZING AND SOLDERING

BRAZING AND SOLDERING. By JAMES F. HOBART. The only book that shows you
just how to handle any job of brazing or soldering that comes along;
tells you what mixture to use, how to make a furnace if you need one.
Full of valuable kinks. The fifth edition of this book has just been
published, and to it much new matter and a large number of tested
formulas for all kinds of solders and fluxes have been added.
Illustrated. 25 cents.

CHARTS

MODERN SUBMARINE CHART WITH 200 PARTS NUMBERED AND NAMED. A
cross-section view, showing clearly and distinctly all the interior of a
Submarine of the latest type. You get more information from this chart,
about the construction and operation of a Submarine, than in any other
way. No details omitted-everything is accurate and to scale. It is
absolutely correct in every detail, having been approved by Naval
Engineers. All the machinery and devices fitted in a modern Submarine
Boat are shown, and to make the engraving more readily understood all
the features are shown in operative form, with Officers and Men in the
act of performing the duties assigned to them in service conditions.
This CHART IS REALLY AN ENCYCLOPEDIA OF A SUBMARINE. It is educational
and worth many times its cost. Mailed in a Tube for 25 cents.

BOX CAR CHART. A chart showing the anatomy of a box car, having every
part of the car numbered and its proper name given in a reference list.
20 cents.

GONDOLA CAR CHART. A chart showing the anatomy of a gondola car, having
every part of the car numbered and its proper reference name given in a
reference list. 20 cents.

PASSENGER CAR CHART. A chart showing the anatomy of a passenger car,
having every part of the car numbered and its proper name given in a
reference list. 20 cents.

WESTINGHOUSE AIR-BRAKE CHARTS. Chart I.—Shows (in colors) the most
modern Westinghouse High Speed and Signal Equipment used on Passenger
Engines, Passenger Engine Tenders, and Passenger Cars. Chart II.—Shows
(in colors) the Standard Westinghouse Equipment for Freight and Switch
Engines, Freight and Switch Engine Tenders, and Freight Cars. Price for
the set 50 cents.

TRACTIVE POWER CHART. A chart whereby you can find the tractive power or
drawbar pull of any locomotive, without making a figure. Shows what
cylinders are equal, how driving wheels and steam pressure affect the
power. What sized engine you need to exert a given drawbar pull or
anything you desire in this line. 50 cents.

HORSE POWER CHART. Shows the horse power of any stationary engine
without calculation. No matter what the cylinder diameter of stroke; the
steam pressure or cut-off; the revolutions, or whether condensing or
non-condensing, it's all there. Easy to use, accurate, and saves time
and calculations. Especially useful to engineers and designers. 50
cents.

BOILER ROOM CHART. By GEO. L. FOWLER. A Chart-size 14 x 28
inches-showing in isometric perspective the mechanisms belonging in a
modern boiler room. Water tube boilers, ordinary grates and mechanical
stokers, feed water heaters and pumps comprise the equipment. The
various parts are shown broken or removed, so that the internal
construction is fully illustrated. Each part is given a reference
number, and these, with the corresponding name, are given in a glossary
printed at the sides. This chart is really a dictionary of the boiler
room--the names of more than 200 parts being given. It is
educational-worth many times its cost. 25 cents.

CIVIL ENGINEERING

HENLEY'S ENCYCLOPEDIA OF PRACTICAL ENGINEERING AND ALLIED TRADES. Edited
by JOSEPH G. HORNER, A. M. I. E. M. This set of five volumes contains
about 2,500 pages with thousands of illustrations, including
diagrammatic and sectional drawings with full explanatory details.. This
work covers the entire practice of Civil and Mechanical Engineering. The
best known experts in all branches of engineering have contributed to
these volumes. The Cyclopedia is admirably well adapted to the needs of
the beginner and the self-taught practical man, as well as the
mechanical engineer, designer, draftsman, shop superintendent, foreman,
and machinist. The work will be found a means of advancement to any
progressive man. It is encyclopedic in scope, thorough and practical in
its treatment of technical subjects, simple and clear in its descriptive
matter, and without unnecessary technicalities or formulae. The articles
are as brief as may be and yet give a reasonably clear and explicit
statement of the subject, and are written by men who have had ample
practical experience in the matters of which they write. It tells you
all you want to know about engineering and tells it so simply, so
clearly, so concisely, that one cannot help but understand. As a work of
reference it is without a peer. $6.00 per single volume. For complete
set of five volumes, $25.00

COKE

COKE-MODERN COKING PRACTICE; INCLUDING THE ANALYSIS OF MATERIALS AND
PRODUCTS. By T. H. BYROM and J. E. CHRISTOPHER. A handbook for those
engaged in Coke manufacture and the recovery of By-products. Fully
illustrated with folding plates, It has been the aim of the authors, in
preparing this book, to produce ore which shall be of use and benefit to
those who are associated with, or interested in, the modern developments
of the industry. Contents: I. Introductory. II. General Classification
of Fuels. III. Coal Washing. IV. The Sampling and Valuation of Coal,
Coke, etc. V. The Calorific Power of Coal and Coke. VI. Coke Ovens. VII:
Coke Ovens, continued. VIII. Coke Ovens, continued. IX. Charging and
Discharging of Coke Ovens, X. Cooling and Condensing Plant. XI. Gas
Exhausters. XII. Composition and Analysis of Ammoniacal Liquor. XIII.
Working-up of Ammoniacal Liquor. XIV. Treatment of Waste Gases from
Sulphate Plants. XV. Valuation of Ammonium Sulphate. XVI. Direct
Recovery of Ammonia from Coke Oven Gases. XVII. Surplus Gas from Coke
Oven. Useful Tables. Very fully illustrated. Price $3.50 net.

COMPRESSED AIR

COMPRESSED AIR IN ALL ITS APPLICATIONS. By GARDNER D. HISCOX. This is
the most complete book on the subject of Air that has ever been issued,
and its thirty-five chapters include about every phase of the subject
one can think of. It may be called an encyclopedia of compressed air. It
is written by an expert, who, in its 665 pages, has dealt with the
subject in a comprehensive manner, no phase of it being omitted.
Includes the physical properties of air from a vacuum to its highest
pressure, its thermodynamics, compression, transmission and uses as a
motive power; in the Operation of Stationary and Portable Machinery, in
Mining, Air Tools, Air Lifts, Pumping of Water, Acids, and Oils; the Air
Blast for Cleaning and Painting, the Sand Blast and its Work, and the
Numerous Appliances in which Compressed Air is a Most Convenient and
Economical Transmitter of Power for Mechanical Work, Railway Propulsion,
Refrigeration, and the Various Uses to which Compressed Air has been
applied. Includes forty-four tables of the physical properties of air,
its compression, expansion, and volumes required for various kinds of
work, and a list of patents on compressed air from 1875 to date. Over
500 illustrations, 5th Edition, revised and enlarged. Cloth bound,
$5.00. Half Morocco, price. $6.50

CONCRETE

ORNAMENTAL CONCRETE WITHOUT MOLDS. By A. A. HOUGHTON. The process for
making ornamental concrete without molds has long been held as a secret,
and now, for the first time, this process is given to the public. The
book reveals the secret and is the only book published which explains a
simple, practical method whereby the concrete worker is enabled, by
employing wood and metal templates of different designs, to mold or
model in concrete any Cornice, Archivolt, Column, Pedestal, Base Cap,
Urn or Pier in a monolithic form-right upon the job. These may be molded
in units or blocks, and then built up to suit the specifications
demanded. This work is fully illustrated, with detailed engravings.
Price $2.00

CONCRETE FROM SAND MOLDS. By A. A. HOUGHTON. A Practical Work treating
on a process which has heretofore been held as a trade-secret by the few
who possessed it, and which will successfully mold every and any class
of ornamental concrete work. The process of molding concrete with sand
molds is of the utmost practical value, possessing the manifold
advantages of a low cost of molds, the ease and rapidity of operation,
perfect details to all ornamental designs, density, and increased
strength of the concrete, perfect curing of the work without attention
and the easy removal of the molds regardless of any undercutting the
design may have. 192 pages. Fully illustrated. Price $2.00

CONCRETE WALL FORMS. By A. A. HOUGHTON. A new automatic wall clamp is
illustrated with working drawings. Other types of wall forms, clamps,
separators, etc., are also illustrated and explained. 50 cents.

CONCRETE FLOORS AND SIDEWALKS. By A. A. HOUGHTON. The molds for molding
squares, hexagonal and many other styles of mosaic floor and sidewalk
blocks are fully illustrated and explained. 50 cents.

PRACTICAL CONCRETE SILO CONSTRUCTION. By A. A. HOUGHTON. Complete
working drawings and specifications are given for several styles of
concrete silos, with illustrations of molds for monolithic and block
silos. The tables, data and information presented in this book are of
the utmost value in planning and constructing all forms of concrete
silos. 50 cents.

MOLDING CONCRETE CHIMNEYS, SLATE AND ROOF TILES. By A. A. HOUGHTON. The
manufacture of all types of concrete slate and roof tile is fully
treated. Valuable data on all forms of reinforced concrete roofs are
contained within its pages. The construction of concrete chimneys by
block and monolithic systems is fully illustrated and described. А
number of ornamental designs of chimney construction with molds are
shown in this valuable treatise. 50 cents.

MOLDING AND CURING ORNAMENTAL CONCRETE. By A. A. HOUGHTON. The proper
proportions of cement and aggregates for various finishes, also the
methods of thoroughly mixing and placing in the molds, are fully
treated. An exhaustive treatise on this subject that every concrete
worker will find of daily use and value. 50 cents.

CONCRETE MONUMENTS, MAUSOLEUMS AND BURIAL VAULTS. By A. A. HOUGHTON. The
molding of concrete monuments to imitate the most expensive cut stone is
explained in this treatise, with working drawings of easily built molds.
Cutting inscriptions and designs is also fully treated. 50 cents.

MOLDING CONCRETE BATH TUBS, AQUARIUMS AND NATATORIUMS. By A. A.
HOUGHTON. Simple molds and instruction are given for molding many styles
of concrete bath tubs, swimming pools, etc. These molds are easily built
and permit rapid and successful work. 50 cents.

CONCRETE BRIDGES, CULVERTS AND SEWERS. By A. A. HOUGHTON. A number of
ornamental concrete bridges with illustrations of molds are given. A
collapsible center or core for bridges, culverts and sewers is fully
illustrated with detailed instructions for building 50 cents.

CONSTRUCTING CONCRETE PORCHES. By A. A. HOUGHTON. A number of designs
with working drawings of molds are fully explained so any one can easily
construct different styles of ornamental concrete porches without the
purchase of expensive molds. 50 cents.

MOLDING CONCRETE FLOWER POTS, BOXES, JARDINIERES, ETC. By A. A.
HOUGHTON. The molds for producing many original designs of flower pots,
urns, flower boxes, jardinières, etc., are fully illustrated and
explained, so the worker can easily construct and operate same. 50
cents.

MOLDING CONCRETE FOUNTAINS AND LAWN ORNAMENTS. By A. A. HOUGHTON. The
molding of a number of designs of lawn seats, curbing, hitching posts,
pergolas, sun dials and other forms of ornamental concrete for the
ornamentation of lawns and gardens, is fully illustrated and described.
50 cents.

CONCRETE FOR THE FARM AND SHOP. By A. A. HOUGHTON. The molding of drain
tile, tanks, cisterns, fence posts, stable floors, hog and poultry
houses and all the purposes for which concrete is an invaluable aid to
the farmer are numbered among the contents of this handy volume. 50
cents.

POPULAR HANDBOOK FOR CEMENT AND CONCRETE USERS. By MYRON H. LEWIS, This
is a concise treatise of the principles and methods employed in the
manufacture and use of cement in all classes of modern works. The author
has brought together in this work all the salient matter of interest to
the user of concrete and its many diversified products. The matter is
presented in logical and systematic order, clearly written, fully
illustrated and free from involved mathematics. Everything of value to
the concrete user is given including kinds of cement employed in
construction, concrete architecture, inspection and testing,
waterproofing, coloring and painting, rules, tables, working, and cost
data. The book comprises thirty-three chapters, as follows:
Introductory. Kinds of Cements and How They are Made. Properties,
Testing and Requirements of Hydraulic Cement. Concrete and its
Properties. Sand, Broken Stone and Gravel for Concrete. How to
Proportion the Materials. How to Mix and Place Concrete. Forms for
Concrete Construction. The Architectural and Artistic Possibilities of
Concrete. Concrete Residences. Mortars, Plasters and Stucco and How to
Use Them. The Artistic Treatment of Concrete Surfaces. Concrete Building
Blocks. The Making of Ornamental Concrete. Concrete Pipes, Fences,
Posts, Etc. Essential Features and Advantages of Reenforced Concrete.
How to Design Reenforced Concrete Beams, Slabs and Columns. Explanations
of the Methods and Principles in Designing Reenforced Concrete Beams and
Slabs. Systems of Reenforcement Employed. Reenforced Concrete in Factory
and General Building Construction. Concrete in Foundation Work. Concrete
Retaining Walls, Abutments, and Bulkheads. Concrete Arches and Arch
Bridges. Concrete Beam and Girder Bridges. Concrete in Sewerage and
Drainage Works. Concrete Tanks, Dams and Reservoirs. Concrete Sidewalks,
Curbs and Pavements. Concrete in Railroad Constructions. The Utility of
Concrete on the Farm. The Waterproofing of Concrete Structure. Grout or
Liquid Concrete and Its Use. Inspection of Concrete Work. Cost of
Concrete Work. Some of the special features of the book are: 1. The
Attention Paid to the Artistic and Architectural Side of Concrete Work.
2. The Authoritative Treatment of the Problem of Waterproofing Concrete.
3. An Excellent Summary of the Rules to be Followed in Concrete
Construction. 4. The Valuable Cost Data and Useful Tables given. A
valuable Addition to the Library of Every Cement and Concrete User.
Price $2.50

WATERPROOFING CONCRETE. By MYRON H. LEWIS. Modern Methods of
Waterproofing Concrete and Other Structures. A condensed statement of
the Principles, Rules, and Precautions to be Observed in Waterproofing
and Damp-proofing Structures and Structural Materials. Paper binding.
Illustrated. Price 50 cents.

DICTIONARIES

STANDARD ELECTRICAL DICTIONARY. By T. O'CONOR SLOANE. An indispensable
work to all interested in electrical science. Suitable alike for the
student and professional. A practical hand-book of reference containing
definitions of about 5,000 distinct words, terms and phrases. The
definitions are terse and concise and include every term used in
electrical science. Recently issued. An entirely new edition. Should be
in the possession of all who desire to keep abreast with the progress of
this branch of science. Complete, concise and convenient. 682 pages. 393
illustrations. Price $3.00

DIES-METAL WORK

DIES: THEIR CONSTRUCTION AND USE FOR THE MODERN WORKING OF SHEET METALS.
By J. V. WOODWORTH. A most useful book, and one which should be in the
hands of all engaged in the press working of metals; treating on the
Designing, Constructing, and Use of Tools, Fixtures and Devices,
together with the manner in which they should be used in the Power
Press, for the cheap and rapid production of the great variety sheet
metal articles now in use. It is designed as a guide to the production
of sheet metal parts at the minimum of cost with the maximum of output.
The hardening and tempering of Press tools and the classes of work which
may be produced to the best advantage by the use of dies in the power
press are fully treated. Its 505 illustrations show dies, press fixtures
and sheet metal working devices, the descriptions of which are so clear
and practical that all metal-working mechanics will be able to
understand how to design, construct and use them. Many of the dies and
press fixtures treated were either constructed by the author or under
his supervision. Others were built by skilful mechanics and are in use
in large sheet metal establishments and machine shops. Price $3.00

PUNCHES, DIES AND TOOLS FOR MANUFACTURING IN PRESSES. By J. V.
WOODWORTH. This work is a companion volume to the author's elementary
work entitled "Dies, Their Construction and Use." It does not go into
the details of die making to the extent of the author's previous book,
but gives a comprehensive review of the field of operations carried on
by presses. A large part of the information given has been drawn from
the author's personal experience. It might well be termed an
Encyclopedia of Die Making. Punch Making, Die Sinking, Sheet Metal
Working, and Making of Special Tools, Sub-presses, Devices and
Mechanical Combinations for Punching, Cutting, Bending, Forming,
Piercing, Drawing, Compressing and Assembling Sheet Metal Parts, and
also Articles of other Materials in Machine Tools. 2nd Edition. Price.
$4.00

DROP FORGING, DIE SINKING AND MACHINE FORMING OF STEEL. By J. V.
WOODWORTH.

This is a practical treatise on Modern Shop Practice, Processes,
Methods, Machines, Tools, and Details, treating on the Hot and Cold
Machine-Forming of Steel and Iron into Finished shapes; Together with
Tools, Dies, and Machinery involved in the manufacture of Duplicate
Forgings and Interchangeable Hot and Cold Pressed Parts from Bar and
Sheet Metal. This book fills a demand of long standing for information
regarding drop forging, die-sinking and machine forming of steel and the
shop practice involved, as it actually exists in the modern drop forging
shop. The processes of die-sinking and force-making, which are
thoroughly described and illustrated in this admirable work, are rarely
to be found explained in such a clear and concise manner as is here set
forth. The process of die-sinking relates to the engraving or sinking of
the female or lower dies, such as are used for drop forgings, hot and
cold machine forging, swedging and the press working of metals. The
process of force-making relates to the engraving or raising of the male
or upper dies used in producing the lower dies for the press-forming and
machine-forging of duplicate parts of metal.

In addition to the arts above mentioned the book contains explicit
information regarding the drop forging and hardening plants, designs,
conditions, equipment, drop hammers, forging machines, etc., machine
forging, hydraulic forging, autogenous welding and shop practice. The
book contains eleven chapters, and the information contained in these
chapters is just what will prove most valuable to the forged metal
worker. All operations described in the work are thoroughly illustrated
by means of perspective half-tones and outline sketches of the machinery
employed. 300 detailed illustrations. Price $2.50

DRAWING-SKETCHING PAPER

LINEAR PERSPECTIVE SELF-TAUGHT. By HERMAN T. C. KRAUS. This work gives
the theory and practice of linear perspective, as used in architectural,
engineering, and mechanical drawings. Persons taking up the study of the
subject by themselves will be able by the use of the instruction given
to readily grasp the subject, and by reasonable practice become good
perspective draftsmen. The arrangement of the book is good; the plate is
on the left-hand, while the descriptive text follows on the opposite
page, so as to be readily referred to. The drawings are on sufficiently
large scale to show the work clearly and are plainly figured. The whole
work makes a very complete course on perspective drawing, and will be
found of great value to architects, civil and mechanical engineers,
patent attorneys, art designers, engravers, and draftsmen. $2.50

PRACTICAL PERSPECTIVE. By RICHARDS and COLVIN. Shows just how to make
all kinds of mechanical drawings in the only practical perspective
isometric. Makes everything plain so that any mechanic can understand a
sketch or drawing in this way. Saves time in the drawing room, and
mistakes in the shops. Contains practical examples of various classes of
work. 3rd Edition. 50 cents.

SELF-TAUGHT MECHANICAL DRAWING AND ELEMENTARY MACHINE DESIGN. By F. L.
SYLVESTER, M.E., Draftsman, with additions by ERIK OBERG, associate
editor of "Machinery." This is a practical treatise on Mechanical
Drawing and Machine Design, comprising the first principles of geometric
and mechanical drawing, workshop mathematics, mechanics, strength of
materials and the calculations and design of machine details. The
author's aim has been to adapt this treatise to the requirements of the
practical mechanic and young draftsman and to present the matter in as
clear and concise a manner as possible. To meet the demands of this
class of students, practically all the important elements of machine
design have been dealt with, and in addition algebraic formulas have
been explained, and the elements of trigonometry treated in the manner
best suited to the needs of the practical man. The book is divided into
20 chapters, and in arranging the material, mechanical drawing, pure and
simple, has been taken up first, as a thorough understanding of the
principles of representing objects facilitates the further study of
mechanical subjects. This is followed by the mathematics necessary for
the solution of the problems in machine design which are presented
later, and a practical introduction to theoretical mechanics and the
strength of materials. The various elements entering into machine
design, such as cams, gears, sprocket wheels, cone pulleys, bolts,
screws, couplings, clutches, shafting and flywheels have been treated in
such a way as to make possible the use of the work as a textbook for a
continuous course of study. It is easily comprehended and assimilated
even by students of limited previous training. 330 pages, 215
engravings. Price. $2.00

A NEW SKETCHING PAPER. A new specially ruled paper to enable you to make
sketches or drawings in isometric perspective without any figuring or
fussing. It is being used for shop details as well as for assembly
drawings, as it makes one sketch do the work of three, and no workman
can help seeing just what is wanted. Pads of 40 sheets, 6 x 9 inches, 25
cents. Pads of 40 sheets, 9 x 12 inches. 50 cents; 40 sheets, 12 x 18,
Price $1.00.

ELECTRICITY

ARITHMETIC OF ELECTRICITY. By Prof. T. O'CONOR SLOANE. A practical
treatise on electrical calculations of all kinds reduced to a series of
rules, all of the simplest forms, and involving only ordinary
arithmetic; each rule illustrated by one or more practical problems,
with detailed solution of each one. This book is classed among the most
useful works published on the science of electricity covering as it does
the mathematics of electricity in a manner that will attract the
attention of those who are not familiar with algebraical formulas. 20th
Edition. 160 pages. Price $1.00

COMMUTATOR CONSTRUCTION. By WM. BAXTER, JR. The business end of any
dynamo or motor of the direct current type is the commutator. This book
goes into the designing, building, and maintenance of commutators, shows
how to locate troubles and how to remedy them; everyone who fusses with
dynamos needs this. 25 cents.

DYNAMO BUILDING FOR AMATEURS, OR HOW TO CONSTRUCT A FIFTY-WATT DYNAMO.
By ARTHUR J. WEED, Member of N. Y. Electrical Society. A practical
treatise showing in detail the construction of a small dynamo or motor,
the entire machine work of which can be done on a small foot lathe.
Dimensioned working drawings are given for each piece of machine work
and each operation is clearly described. This machine, when used as a
dynamo, has an output of fifty watts; when used as a motor it will drive
a small drill press or lathe. It can be used to drive a sewing machine
on any and all ordinary work. The book is illustrated with more than
sixty original engravings showing the actual construction of the
different parts. Among the contents are chapters on 1. Fifty Watt
Dynamo. 2. Side Bearing Rods. 3. Field Punchings. 4. Bearings. 5.
Commutator. 6. Pulley. 7. Brush Holders. 8. Connection Board. 9.
Armature Shaft. 10. Armature. 11. Armature Winding. 12. Field Winding.
13. Connecting and Starting. Price, paper, 50 cents. Cloth. $1.00.

ELECTRIC FURNACES AND THEIR INDUSTRIAL APPLICATIONS. By J. WRIGHT This
is a book which will prove of interest to many classes of people; the
manufacturer who desires to know what product can be manufactured
successfully in the electric furnace, the chemist who wishes to post
himself on the electro-chemistry, and the student of science who merely
looks into the subject from curiosity. The book is not so scientific as
to be of use only to the technologist, nor so unscientific as to suit
only the tyro in electro-chemistry; it is a practical treatise of what
has been done, and of what is being done, both experimentally and
commercially with the electric furnace. In important processes not only
are the chemical equations given, but complete thermal data are set
forth and both the efficiency of the furnace and the cost of the product
are worked out, thus giving the work a solid commercial value aside from
its efficacy as a work of reference. The practical features of furnace
building are given the space that the subject deserves. The forms and
refractory materials used in the linings, the arrangement of the
connections to the electrodes, and other important details are
explained. 288 pages. New Revised Edition. Fully illustrated. Price
$3.00

ELECTRIC LIGHTING AND HEATING POCKET BOOK. By SYDNEY F. WALKER. This
book puts in convenient form useful information regarding the apparatus
which is likely to be attached to the mains of an electrical company.
Tables of units and equivalents are included and useful electrical laws
and formulas are stated. One section is devoted to dynamos, motors,
transformers and accessory apparatus; another to accumulators, another
to switchboards and related equipment, a fourth to a description of
various systems of distribution, a fifth section to a discussion of
instruments, both for portable use and switchboards; another section
deals with electric lamps of various types and accessory appliances, and
the concluding section is given up to electric heating apparatus. In
each section a large number of commercial types are described, frequent
tables of dimensions being included. A great deal of detail information
of each' line of apparatus is given and the illustrations shown give a
good idea of the general appearance of the apparatus under discussion.
The book also contains much valuable information for the central station
engineer. 438 pages. 300 engravings. Bound in leather pocket book form.
Price $3.00

ELECTRIC WIRING, DIAGRAMS AND SWITCHBOARDS. By NEWTON HARRISON. A
thoroughly practical treatise covering the subject of Electric Wiring in
all its branches, including explanations and diagrams which are
thoroughly explicit and greatly simplify the subject. Practical
every-day problems in wiring are presented and the method of obtaining
intelligent results clearly shown. Only arithmetic is used. Ohm's law is
given a simple explanation with reference to wiring for direct and
alternating currents. The fundamental principle of drop of potential in
circuits is shown with its various applications. The simple circuit is
developed with the position of mains, feeders and branches; their
treatment as a part of a wiring plan and their employment in
house-wiring clearly illustrated. Some simple facts about testing are
included in connection with the wiring. Molding and conduit work are
given careful consideration; and switchboards are systematically
treated, built up and illustrated, showing the purpose they serve, for
connection with the circuits, and to shunt and compound wound machines.
The simple principles of switchboard construction, the development of
the switchboard, the connections of the various instruments including
the lightning arrester, are also plainly set forth. Alternating current
wiring is treated, with explanations of the power factor, conditions
calling for various sizes of wire and a simple way of obtaining the
sizes for single-phase, two-phase and three-phase circuits. This is the
only complete work issued showing and telling you what you should know
about direct and alternating current wiring. It is a ready reference.
The work is free from advanced technicalities and mathematics,
arithmetic being used throughout. It is in every respect a handy,
well-written, instructive, comprehensive volume on wiring for the
wireman, foreman, contractor, or electrician. 272 pages; 105
illustrations. Price $1.50

ELECTRIC TOY MAKING, DYNAMO BUILDING, AND ELECTRIC MOTOR CONSTRUCTION.
By PROF. T. O'CONOR SLOANE. This work treats of the making at home of
electrical toys, electrical apparatus, motors, dynamos and instruments
in general, and is designed to bring within the reach of young and old
the manufacture of genuine and useful electrical appliances. The work is
especially designed for amateurs and young folks. Thousands of our young
people are daily experimenting, and busily engaged in making electrical
toys and apparatus of various kinds. The present work is just what is
wanted to give the much needed information in a plain, practical manner,
with illustrations to make easy the carrying out of the work. 19th
Edition. Price $1.00

ELECTRICIAN'S HANDY BOOK. By PROF. T. O’CONOR SLOANE. This work of 768
pages is intended for the practical electrician who has to make things
go. The entire field of electricity is covered within its pages. Among
some of the subjects treated are: The Theory of the Electric Current and
Circuit, Electro-Chemistry, Primary Batteries, Storage Batteries,
Generation and Utilization of Electric Powers, Alternating Current,
Armature Winding, Dynamos and Motors, Motor Generators, Operation of the
Central Station Switchboards, Safety Appliances, Distribution of
Electric Light and Power, Street Mains, Transformers, Arc and
Incandescent Lighting, Electric Measurements, Photometry, Electric
Railways, Telephony, Bell-Wiring, Electro-Plating, Electric Heating,
Wireless Telegraphy, etc. It contains no useless theory; everything is
to the point. It teaches you just what you want to know about
electricity. It is the standard work published on the subject. Forty-one
chapters, 610 engravings, handsomely bound in red leather with title and
edges in gold. Price: $3.50

ELECTRICITY IN FACTORIES AND WORKSHOPS, ITS COST AND CONVENIENCE.

By ARTHUR P. HASLAM.

A practical book for power producers and power users showing what a
convenience the electric motor, in its various forms, has become to the
modern manufacturer. It also deals with the conditions which determine
the cost of electric driving, and compares this with other methods of
producing and utilizing power.

Among the chapters contained in the book are: The Direct Current Motor;
The Alternating Current Motor; The Starting and Speed Regulation of
Electric Motors; The Rating and Efficiency of Electric Motors; The Cost
of Energy as Affected by Conditions of Working, The Question for the
Small Power User; Independent Generating Plants; Oil and Gas Engine
Plants; Steam Plants; Power Station Tariffs; The Use of Electric Power
in Textile Factories; Electric Power in Printing Works; The Use of
Electric Power in Engineering Workshops Miscellaneous Application of
Electric Power; The Installation of Electric Motors; The Lighting of
Industrial Establishments 312 pages. Very fully illustrated. Price $2.50

ELECTRICITY SIMPLIFIED. By PROF. T. O'CONOR SLOANE. The object of
"Electricity Simplified" is to make the subject as plain as possible and
to show what the modern conception of electricity is; to show how two
plates of different metals immersed in acid can send a message around
the globe; to explain how a bundle of copper wire rotated by a steam
engine can be the agent in lighting our streets, to tell what the volt,
ohm and ampere are, and what high and low tension mean; and to answer
the questions that perpetually arise in the mind in this age of
electricity. 172 pages. Illustrated. Price $1.00

HOUSE WIRING. By THOMAS W. POPPE. This work describes and illustrates
the actual installation of Electric Light Wiring, the manner in which
the work should be done, and the method of doing it. The book can be
conveniently carried in the pocket. It is intended for the Electrician,
Helper and Apprentice. It solves all Wiring Problems, and contains
nothing that conflicts with the rulings of the National Board of Fire
Underwriters. It gives just the information essential to the Successful
Wiring of a Building. Among the subjects treated are: Locating the
Meter. Panel Boards. Switches. Plug Receptacles. Brackets. Ceiling
Fixtures. The Meter Connections. The Feed Wires. The Steel Armored Cable
System. The Flexible Steel Conduit System. The Ridig Conduit System. A
digest of the National Board of Fire Underwriters' rules relating to
metallic wiring systems. Various switching arrangements explained and
diagrammed. The easiest method of testing the Three and Four-way
circuits explained. The grounding of all metallic wiring systems and the
reason for doing so shown and explained. The insulation of the metal
parts of lamp fixtures and the reason for the same described and
illustrated. 125 pages. Fully illustrated. Flexible cloth. Price 50
cents.

HOW TO BECOME A SUCCESSFUL ELECTRICIAN. By PROF. T. O'CONOR SLOANE.
Every young man who wishes to become a successful electrician should
read this book. It tells in simple language the surest and easiest way
to become a successful electrician. The studies to be followed, methods
of work, field of operation and the requirements of the successful
electrician are pointed out and fully explained. Every young engineer
will find this an excellent stepping-stone to more advanced works on
electricity which he must master before success can be attained. Many
young men become discouraged at the very out-start by attempting to read
and study books that are far beyond their comprehension. This book
serves as the connecting link between the rudiments taught in the public
schools and the real study of electricity. It is interesting from cover
to cover. Fifteenth edition. 202 pages. Illustrated. Price $1.00

MANAGEMENT OF DYNAMOS. By LUMMIS-PATERSON. A handbook of theory and
practice. This work is arranged in three parts. The first part covers
the elementary theory of the dynamo. The second part, the construction
and action of the different classes of dynamos in common use are
described; while the third part relates to such matters as affect the
practical management and working of dynamos and motors. The following
chapters are contained in the book: Electrical Units; Magnetic
Principles; Theory of the Dynamo; Armature; Armature in Practice; Field
Magnets; Field Magnets in Practice; Regulating Dynamos; Coupling
Dynamos; Installation, Running, and Maintenance of Dynamos; Faults in
Dynamos; Faults in Armatures; Motors. 292 pages. 117 illustrations.
Price $1.50

STANDARD ELECTRICAL DICTIONARY. By T. O'CONOR SLOANE. An indispensable
work to all interested in electrical science. Suitable alike for the
student and professional. A practical hand-book of reference containing
definitions of about 5,000 distinct words, terms and phrases. The
definitions are terse and concise and include every term used in
electrical science. Recently issued. An entirely new edition. Should be
in the possession of all who desire to keep abreast with the progress of
this branch of science. In its arrangement and typography the book is
very convenient. The word or term defined is printed in black-faced type
which readily catches the eye, while the body of the page is in smaller
but distinct type. The definitions are well worded, and so as to be
understood by the non-technical reader. The general plan seems to be to
give an exact, concise definition, and then amplify and explain in a
more popular way. Synonyms are also given, and references to other words
and phrases are made. A very complete and accurate index of fifty pages
is at the end of the volume; and as this index contains all synonyms,
and as all phrases are indexed in every reasonable combination of words,
reference to the proper place in the body of the book is readily made.
It is difficult to decide how far a book of this character is to keep
the dictionary form, and to what extent it may assume the encyclopedia
form. For some purposes, concise, exactly worded definitions are needed;
for other purposes, more extended descriptions are required. This book
seeks to satisfy both demands, and does it with considerable success.
Complete, concise, and convenient. 682 pages. 393 illustrations. Twelfth
edition. Price $3.00

SWITCHBOARDS. By WILLIAM BAXTER, JR. This book appeals to every engineer
and electrician who wants to know the practical side of things. It takes
up all sorts and conditions of dynamos, connections and circuits and
shows by diagram and illustration just how the switchboard should be
connected. Includes direct and alternating current boards, also those
for arc lighting, incandescent, and power circuits. Special treatment on
high voltage boards for power transmission. 2nd Edition. 190 pages.
Illustrated. Price $1.60

TELEPHONE CONSTRUCTION, INSTALLATION, WIRING, OPERATION AND MAINTENANCE.
By W. H. RADCLIFFE and H. C. Cushing. This book gives the principles of
construction and operation of both the Bell and Independent instruments;
approved methods of installing and wiring them; the means of protecting
them from lightning and abnormal currents; their connection together for
operation as series or bridging stations; and rules for their inspection
and maintenance. Line wiring and the wiring and operation of special
telephone systems are also treated. Intricate mathematics are avoided,
and all apparatus, circuits and systems are thoroughly described. The
appendix contains definitions of units and terms used in the text.
Selected wiring tables, which are very helpful, are also included. Among
the subjects treated are Construction, Operation, and installation of
Telephone Instruments, Inspection and Maintenance of Telephone
Instruments; Telephone Line Wiring; Testing Telephone Line Wires and
Cables; Wiring and Operation of Special Telephone Systems; etc. 100
pages, 125 illustrations. $1.00

WIRELESS TELEGRAPHY AND TELEPHONY SIMPLY EXPLAINED. By ALFRED P. MORGAN.

This is undoubtedly one of the most complete and comprehensible
treatises on the subject ever published, and a close study of its pages
will enable one to master all the details of the wireless transmission
of messages. The author has filled a long felt want and has succeeded in
furnishing, a lucid, comprehensible explanation in simple language of
the theory and practice of wireless telegraphy and telephony. Among the
contents are: Introductory; Wireless Transmission and Reception—The
Aerial System, Earth Connections—The Transmitting Apparatus, Spark Coils
and Transformers, Condensers, Helixes, Spark Gaps, Anchor Gaps, Aerial
Switches—The Receiving Apparatus, Detectors, etc.—Tuning and Coupling,
Tuning Coils, Loose Couplers, Variable Condensers, Directive Wave
Systems-Miscellaneous Apparatus: Telephone Receivers, Range of Stations,
Static, Interference Wireless Telephones, Sound and Sound Waves, The
Vocal Cords and Ear—Wireless Telephones, How Sounds are changed into
Electric Waves Wireless Telephones, The Apparatus-Summary. 200 pages.
150 engravings. Price $1.00

WIRELESS TELEPHONES AND HOW THEY WORK. By JAMES ERSKINE-MURRAY.

This work is free from elaborate details and aims at giving a clear
survey of the way in which Wireless Telephones work. It is intended for
amateur workers and for those whose knowledge of electricity is slight.
Chapters contained: How We Hear; Historical; The Conversion of Sound
into Electric Waves; Wireless Transmission; The Production of
Alternating Currents of High Frequency; How the Electric Waves are
Radiated and Received; The Receiving Instruments; Detectors;
Achievements and Expectations; Glossary of Technical Words, Cloth. Price
$1.00

WIRING A HOUSE. By HERBERT PRATT.

Shows a house already built; tells just how to start about wiring it;
where to begin; what wire to use; how to run it according to Insurance
Rules; in fact just the information you need. Directions apply equally
to a shop. Fourth edition. 25 cents.

FACTORY MANAGEMENT, ETC.

MODERN MACHINE SHOP CONSTRUCTION, EQUIPMENT AND MANAGEMENT.

By O. E. PERRIGO, M.E.

The only work published that describes the modern machine shop or
manufacturing plant from the time the grass is growing on the site
intended for it until the finished product is shipped. By a careful
study of its thirty-two chapters the practical man may economically
build, efficiently equip, and successfully manage the modern machine
shop or manufacturing establishment. Just the book needed by those
contemplating the erection of modern shop buildings, the re-building and
re-organization of old ones, or the introduction of modern shop methods,
time and cost system. It is a book written and illustrated by a
practical shop man for practical shop men who are too busy to read
theories and want facts. It is the most complete all around book of its
kind ever published. It is a practical book for practical men, from the
apprentice in the shop to the president in the office. It minutely
describes and illustrates the most simple and yet the most efficient
time and cost system yet devised. Price $6.00

FUEL

COMBUSTION OF COAL AND THE PREVENTION OF SMOKE. By WM. M. BARR. This
book has been prepared with special reference to the generation of heat
by the combustion of the common fuels found in the United States, and
deals particularly with the conditions necessary to the economic and
smokeless combustion of bituminous coals in Stationary and Locomotive
Steam Boilers. The presentation of this important subject is systematic
and progressive. The arrangement of the book is in a series of practical
questions to which are appended accurate answers, which describe in
language, free from technicalities, the several processes involved in
the furnace combustion of American fuels; it clearly states the
essential requisites for perfect combustion, and points out the best
methods for furnace construction for obtaining the greatest quantity of
heat from any given quality of coal. Nearly 350 pages, fully
illustrated. Price $1.00

SMOKE PREVENTION AND FUEL ECONOMY. By BOOTH and KERSHAW. A complete
treatise for all interested in smoke prevention and combustion, being
based on the German work of Ernst Schmatolla, but it is more than a mere
translation of the German treatise, much being added. The authors show
as briefly as possible the principles of fuel combustion, the methods
which have been and are at present in use, as well as the proper
scientific methods for obtaining all the energy in the coal and burning
it without smoke. Considerable space is also given to the examination of
the waste gases, and several of the representative English and American
mechanical stoker and similar appliances are described. The losses
carried away in the waste gases are thoroughly analyzed and discussed in
the Appendix, and abstracts are also here given of various patents on
combustion apparatus. The book is complete and contains much of value to
all who have charge of large plants. 194 pages. Illustrated. Price $2.80

GAS ENGINES AND GAS

GASOLINE ENGINES: THEIR OPERATION, USE AND CARE. By A. HYATT VERRILL.
The Simplest, Latest and Most Comprehensive popular work published on
Gasoline Engines describing what the Gasoline engine is; its
construction and operation; how to install it; how to select it; how to
use it and how to remedy troubles encountered. Intended for owners,
Operators and Users of Gasoline Motors of all kinds. This work fully
describes and illustrates the various types of Gasoline engines used in
Motor Boats, Motor Vehicles and Stationary Work. The parts, accessories
and Appliances are described, with chapters on ignition, fuel,
lubrication, operation and engine troubles. Special attention is given
to the care, operation and repair of motors with useful hints and
suggestions on emergency repairs and make-shifts. A complete glossary of
technical terms and an alphabetically arranged table of troubles and
their symptoms form most valuable and unique features of this manual.
Nearly every illustration in the book is original, having been made by
the author. Every page is full of interest and value. A book which you
cannot afford to be without. 320 pages. Nearly 150 specially made
engravings. Price $1.50

GAS, GASOLINE, AND OIL ENGINES. By GARDNER D. HISCOX. Just issued, 20th
revised and enlarged edition. Every user of a gas engine needs this
book. Simple, instructive, and right up-to-date. The only complete work
on the subject. Tells all about the running and management of gas,
gasoline and oil engines, as designed and manufactured in the United
States. Explosive motors for stationary, marine and vehicle power are
fully treated, together with illustrations of their parts and tabulated
sizes, also their care and running are included. Electric ignition by
induction coil and jump spark' are fully explained and illustrated,
including valuable information on the testing for economy and power and
the erection of power plants. The rules and regulations of the Board of
Fire Underwriters in regard to the installation and management of
gasoline motors is given in full, suggesting the safe installation of
explosive motor power. A list of United States Patents issued on gas,
gasoline, and oil engines and their adjuncts from 1875 to date is
included. 484 pages. 410 engravings Price $2.50

MODERN GAS ENGINES AND PRODUCER GAS PLANTS. By R. E. MATHOR, M.E. A
guide for the gas engine designer, user, and engineer in the
construction, selection, purchase installation, operation, and
maintenance of gas engines. More than one book on gas engines has been
written, but not one has thus far even encroached on the field covered
by this book. Above all Mr. Mathor's work is a practical guide.
Recognizing the need of a volume that would assist the gas engine user
in understanding thoroughly the motor upon which he depends for power,
the author has discussed his subject without the help of any mathematics
and without elaborate theoretical explanations. Every part of the gas
engine is described in detail, tersely, clearly, with a thorough
understanding of the requirements of the mechanic. Helpful suggestions
as to the purchase of an engine, its installation, care, and operation
form a most valuable feature of the work. 320 pages. 175 detailed
illustrations. Price $2.50

GAS ENGINE CONSTRUCTION, OR HOW TO BUILD A HALF-HORSE-POWER GAS ENGINE.
By PARSELL and WEED. A practical treatise of 300 pages describing the
theory and principles of the action of Gas Engines of various types and
the design and construction of a half-horse power Gas Engine, with
illustrations of the work in actual progress, together with the
dimensioned working drawings giving clearly the sizes of the various
details; for the student, the scientific investigator and the amateur
mechanic. This book treats of the subject more from the standpoint of
practice than that of theory. The principles of operation of Gas Engines
are clearly and simply described and then the actual construction of a
half-horse power engine is taken up, step by step, showing in detail the
making of the Gas Engine. 3d Edition. 300 pages. Price $2.50

THE GASOLINE ENGINE ON THE FARM: ITS OPERATION, REPAIR AND USES. By XENO
W. PUTNAM. This is a practical treatise on the Gasoline and Kerosene
engine intended for the man who wants to know just how to manage his
engine and how to apply it to all kinds of farm work to the best
advantage. The book includes selecting the most suitable engine for farm
work, its most convenient and efficient installation, with chapters on
troubles, their remedies and how to avoid them. The care and management
of the farm tractor in plowing, harrowing, harvesting and road grading
are fully covered; also plain directions are given for handling the
tractor on the road. Special attention is given to relieving farm life
of its drudgery by applying power to the disagreeable small tasks which
must otherwise be done by hand. Many homemade contrivances for cutting
wood, supplying kitchen, garden and barn with water, loading, hauling
and unloading hay, delivering grain to the bins or the feed trough are
included; also full directions for making the engine milk the cows,
churn, wash, sweep the house and clean the windows, etc. Very fully
illustrated with drawings of working parts and cuts showing Stationary,
Portable and Tractor Engines doing all kinds of farm work. 300 pages.
Nearly 150 engravings. 12mo. Price $1.50

CHEMISTRY OF GAS MANUFACTURE. By H. M. ROYLES. This book covers points
likely to arise in the ordinary course of the duties of the engineer or
manager of a gas works not large enough to necessitate the employment of
a separate chemical staff. It treats of the testing of the raw materials
employed in the manufacture of illuminating coal gas, and of the gas
produced. The preparation of standard solutions is given as well as the
chemical and physical examination of gas coal including among its
contents-Preparations of Standard Solutions, Coal, Furnaces, Testing and
Regulation. Products of Carbonization. Analysis of Crude Coal Gas.
Analysis of Lime. Ammonia. Analysis of Oxide of Iron. Naphthalene.
Analysis of Fire-Bricks and Fire-Clay. Weldom and Spent Oxide.
Photometry and Gas Testing. Carburetted Water Gas. Metropolis Gas.
Miscellaneous Extracts. Useful Tables. $4.50

GEARING AND CAMS

BEVEL GEAR TABLES. By D. AG. ENGSTROM. A book that will at once commend
itself to mechanics and draftsmen. Does a way with all the trigonometry
and fancy figuring on bevel gears and makes it easy for anyone to lay
them out or make them just right. There are 36 full-page tables that
show every necessary dimension for all sizes or combinations you're apt
to need. No puzzling figuring or guessing. Gives placing distance, all
the angles (including cutting angles), and the correct cutter to use. A
copy of this prepares you for anything in the bevel gear line. $1.00

CHANGE GEAR DEVICES. By OSCAR E. PERRIGO. A practical book for every
designer, draftsman, and mechanic interested in the invention and
development of the devices for feed changes on the different machines
requiring such mechanism. All the necessary information on this subject
is taken up, analyzed, classified, sifted, and concentrated for the use
of busy men who have not the time to go through the masses of irrelevant
matter with which such a subject is usually encumbered and select such
information as will be useful to them. It shows just what has been done,
how it has been done, when it was done, and who did it. It saves time in
hunting up patent records and re-inventing old ideas. 88 pages. $1.00

DRAFTING OF CAMS. By Louis ROUILLION.

The laying out of cams is a serious problem unless you know how to go at
it right. This puts you on the right road for practically any kind of
cam you are likely to run up against. 25 cents.

HYDRAULICS

HYDRAULIC ENGINEERING. By GARDNER D. HISCOX. A treatise on the
properties, power, and resources of water for all purposes. Including
the measurement of streams, the flow of water in pipes or conduits; the
horse-power of falling water; turbine and impact water-wheels, wave
motors, centrifugal, reciprocating, and airlist pumps.

With 300 figures and diagrams and 36 practical tables. All who are
interested in water-works development will find this book a useful one,
because it is an entirely practical treatise upon a subject of present
importance, and cannot fail in having a far-reaching influence, and for
this reason should have a place in the working library of every
engineer. Among the subjects treated are: Historical-Hydraulics,
Properties of Water; Measurement of the flow of Streams; Flow from
Subsurface orifices and nozzles; Flow of water in Pipes; Siphons of
various kinds; Dams and Great Storage Reservoirs; City and Town Water
Supply; Wells and their reenforcement; Air lift methods of raising
water; artesian wells; Irrigation of Arid districts; Water Power, Water
Wheels; Pumps and Pumping Machinery; Reciprocating Pumps; Hydraulic
Power Transmission; Hydraulic Mining; Canals; Ditches; Conduits and Pipe
Lines; Marine Hydraulics; Tidal and Sea Wave power, etc. 320 pages.
Price $4.00

ICE AND REFRIGERATION

POCKET BOOK OF REFRIGERATION AND ICE MAKING. By A. J. WALLIS-TAYLOR This
is one of the latest and most comprehensive reference books published on
the subject of refrigeration and cold storage. It explains the
properties and refrigerating effect of the different fluids in use, the
management of refrigerating machinery and the construction and
insulation of cold rooms with their required pipe surface for different
degrees of cold; freezing mixtures and non-freezing brines, temperatures
of cold rooms for all kinds of provisions, cold storage charges for all
classes of goods, ice making and storage of ice, data and memoranda for
constant reference by refrigerating engineers, with nearly one hundred
tables containing valuable references to every fact and condition
required in the installment and operation of a refrigerating plant.
Illustrated. (5th Edition, revised.) Price $1.50

INVENTIONS PATENTS

INVENTOR'S MANUAL, HOW TO MAKE A PATENT PAY.

This is a book designed as a guide to inventors in perfecting their
inventions, taking out their patents and disposing of them. It is not in
any sense a Patent Solicitor's Circular, nor a Patent Broker's
Advertisement. No advertisements of any description appear in the work.
It is a book containing a quarter of a century's experience of a
successful inventor, together with notes based upon the experience of
many other inventors. Among the subjects treated in this work are: How
to Invent. How to Secure a Good Patent. Value of Good Invention. How to
exhibit an Invention. How to Interest Capital. How to Estimate the value
of a Patent. Value of Design Patents. Value of Foreign Patents. Value of
Small Inventions. Advice on Selling Patents. Advice on the formation of
Stock Companies. Advice on the Formation of Limited Liability Companies.
Advice on Disposing of Old Patents. Advice as to Patent Attorneys.
Advice as to Selling Agents. Forms of Assignments. License and
Contracts. State Laws Concerning Patent Rights. 1900 Census of the
United States by counties of over 10,000 population. Revised edition.
120 pages. Price $1.00

KNOTS

KNOTS, SPLICES AND ROPE WORK. By A. HYATT VERRILL. This is a practical
book giving complete and simple directions for making all the most
useful and ornamental knots in common use, with chapters on Splicing,
Pointing, Seizing, Serving, etc. This book is fully illustrated with one
hundred and fifty original engravings which show how each knot, tie or
splice is formed and its appearance when finished. The book will be
found of the greatest value to Campers, Yachtsmen, Travelers, Boy Scouts
in fact to anyone having occasion to use or handle rope or knots for any
purpose. The book is thoroughly reliable and practical and is not only a
guide but a teacher. It is the standard work on the subject. Among the
contents are: 1. Cordage, Kinds of Rope, Construction of Rope, Parts of
Rope Cable and Bolt Rope, Strength of Rope, Weight of Rope. 2. Simple
knots and Bends. Terms used in Handling Rope. Seizing Rope. 3. Ties and
Hitches. 4. Noose, Loops and Mooring Knots. 5. Shortenings, Grommets and
Selvages. 6. Lashings. Seizings and Splices. 7. Fancy Knots and Rope
Work. 128 pages. 150 original engravings. Price 60 cents.

LATHE WORK

MODERN AMERICAN LATHE PRACTICE. By OSCAR E. PERRIGO. This is a new book
from cover to cover, and the only complete American work on the subject
written by a man who knows not only how work ought to be done, but who
also knows how to do it, and how to convey this knowledge to others. It
is strictly up-to-date in its descriptions and illustrations, which
represent the very latest practice in lathe and boring mill operations
as well as the construction of and latest developments in the
manufacture of these important classes of machine tools. Lathe history
and the relations of the Lathe to manufacturing are given; also a
description of the various devices for Feeds and Thread Cutting
mechanisms from early efforts in this direction to the present time.
Lathe design is thoroughly discussed, including Back Gearing, Driving
Cones, Thread Cutting Gears, and all the essential elements of the
modern Lathe. The classification of Lathes is taken up, giving the
essential differences of the several types of Lathes, including, as is
usually understood, Engine Lathes, Bench Lathes, Speed Lathes, Forge
Lathes, Gap Lathes, Pulley Lathes, Forming Lathes, Multiple Spindle
Lathes, Rapid Reduction Lathes, Precision Lathes, Turret Lathes, Special
Lathes, Electrically Driven Lathes, etc. 424 pages. 314 illustrations.
Price $2.50

PRACTICAL METAL TURNING. By JOSEPH G. HORNER. This important and
practical subject is treated in a full and exhaustive manner and nothing
of importance is omitted. The principles and practice and all the
different branches of Turning are considered and well illustrated. All
the different kinds of Chucks of usual forms, as well as some unusual
kinds, are shown. A feature of the book is the important section devoted
to modern Turret practice; Boring is another subject which is treated
fully; and the chapter on Tool Holders illustrates a large number of
representative types. Thread Cutting is treated at reasonable length;
and the last chapter contains a good deal of information relating to the
High-Speed Steels and their work. The numerous tools used by machinists
are illustrated, and also the adjuncts of the lathe. In fact, the entire
subject is treated in such a thorough manner as to make this book the
standard one on the subject. It is indispensable to the manager,
engineer, and machinist as well as to the student, amateur, and
experimental, man who desires to keep up-to-date. 400 pages, fully
illustrated. Price $3.50

TURNING AND BORING TAPERS. By FRED H. COLVIN. There are two ways to turn
tapers; the right way and one other. This treatise has to do with the
right way; it tells you how to start the work properly, how to set the
lathe, what tools to use and how to use them, and forty and one other
little things that you should know. Fourth edition. 25 cents.

LIQUID AIR

LIQUID AIR AND THE LIQUEFACTION OF GASES. By T. O'CONOR SLOANE. This
book gives the history of the theory, discovery, and manufacture of
Liquid Air, and contains an illustrated description of all the
experiments that have excited the wonder of audiences all over the
country. It shows how liquid air, like water, is carried hundreds of
miles and is handled in open buckets. It tells what may be expected from
it in the near future. A book that renders simple one of the most
perplexing chemical problems of the century. Startling developments
illustrated by actual experiments. It is not only a work of scientific
interest and authority, but is intended for the general reader, being
written in a popular style-easily understood by every one. Second
edition. 365 pages. Price $2.00

LOCOMOTIVE ENGINEERING

AIR-BRAKE CATECHISM. By ROBERT H. BLACKALL. This book is a standard text
book. It covers the Westinghouse Air-Brake Equipment, including the No.
5 and the No. 6 E. T Locomotive Brake Equipment; the K (Quick-Service)
Triple Valve for Freight Service; and the Cross-Compound Pump. The
operation of all parts of the apparatus is explained in detail, and a
practical way of finding their peculiarities and defects, with a proper
remedy, is given. It contains 2,000 questions with their answers, which
will enable any railroad man to pass any examination on the subject of
Air Brakes. Endorsed and used by air-brake instructors and examiners on
nearly every railroad in the United States. 25th Edition. 350 pages,
fully illustrated with folding plates and diagrams. $2.00

AMERICAN COMPOUND LOCOMOTIVES. By FRED. H. COLVIN.

The only book on compounds for the engineman or shopman that shows in a
plain, practical way the various features of compound locomotives in
use. Shows how they are made, what to do when they break down or balk.
Contains sections as follows:-A Bit of History. Theory of Compounding
Steam Cylinders. Baldwin Two-Cylinder Compound. Pittsburg Two-Cylinder
Compound. Rhode Island Compound. Richmond Compound. Rogers Compound.
Schenectady Two-Cylinder Compound. Vauclain Compound. Tandem Compounds.
Baldwin Tandem. The Colvin-Wightman Tandem. Schenectady Tandem. Balanced
Locomotives. Baldwin Balanced Compound. Plans for Balancing. Locating
Blows. Breakdowns. Reducing Valves. Drifting. Valve Motion.
Disconnecting. Power of Compound Locomotives. Practical Notes. Fully
illustrated and containing ten special "Duotone" inserts on heavy Plate
Paper, showing different types of Compounds. 142 pages. Price $1.00

APPLICATION OF HIGHLY SUPERHEATED STEAM TO LOCOMOTIVES. By ROBERT GARBE.

A practical book. Contains special chapters on Generation of Highly
Superheated Steam; Superheated Steam and the Two-Cylinder Simple Engine;
Compounding and Superheating; Designs of Locomotive Superheaters;
Constructive Details of Locomotives using Highly Superheated Steam;
Experimental and Working Results. Illustrated with folding places and
tables. Price $2.50

COMBUSTION OF COAL AND THE PREVENTION OF SMOKE. By WM. M. BARR. This
book has been prepared with special reference to the generation of heat
by the combustion of the common fuels found in the United States, and
deals particularly with the conditions necessary to the economic and
smokeless combustion of bituminous coal in Stationary and Locomotive
Steam Boilers. The presentation of this important subject is systematic
and progressive. The arrangement of the book is in a series of practical
questions to which are appended accurate answers, which describe in
language, free from technicalities, the several processes involved in
the furnace combustion of American fuels; it clearly states the
essential requisites for perfect combustion, and points out the best
methods of furnace construction for obtaining the greatest quantity of
heat from any given quality of coal. Nearly 350 pages, fully
illustrated. Price $1.00

DIARY OF A ROUND HOUSE FOREMAN. By T. S. REILLY. This is the greatest
book of railroad experiences ever published. Containing a fund of
information and suggestions along the line of handling men, organizing,
etc., that one cannot afford to miss. 176 pages. Price $1.00

LINK MOTIONS, VALVES AND VALVE SETTING. By FRED H. COLVIN, Associate
Editor of "American Machinist."

A handy book for the engineer or machinist that clears up the mysteries
of valve setting. Shows the different valve gears in use, how they work,
and why. Piston and slide valves of different types are illustrated and
explained. A book that every railroad man in the motive power department
ought to have. Contains chapters on Locomotive Link Motion, Valve
Movements, Setting Slide Valves, Analysis by Diagrams, Modern Practice,
Slip of Block, Slide Valves, Piston Valves, Setting Piston Valves,
Joy-Allen Valve Gear, Walschaert Valve Gear, Gooch Valve Gear,
Alfree-Hubbell Valve Gear, etc., etc. Fully illustrated. Price 50 cents.

LOCOMOTIVE BOILER CONSTRUCTION. By FRANK A. KLEINHANS. The construction
of boilers in general is treated, and following this, the locomotive
boiler is taken up in the order in which its various parts go through
the shop. Shows all types of boilers used; gives details of
construction; practical facts, such as life of riveting, punches and
dies; work done per day, allowance for bending and flanging sheets, and
other data. Locomotive boilers present more difficulty in laying out and
building than any other type, and for this reason the author uses them
as examples. Anyone who can handle them can tackle anything. Contains
chapters on Laying Out Work; Flanging and Forging; Punching; Shearing:
Plate Planing; General Tables; Finishing Parts; Bending; Machinery
Parts; Riveting; Boiler Details; Smoke Box Details; Assembling and
Caulking; Boiler Shop Machinery, etc., etc. There isn't a man who has
anything to do with boiler work, either new or repair work, who doesn't
need this book. The manufacturer, superintendent, foreman, and boiler
worker all need it. No matter what the type of boiler, you'll find a
mint of information that you wouldn't be without. Over 400 pages, five
large folding plates. Price: $3.00

LOCOMOTIVE BREAKDOWNS AND THEIR REMEDIES. By GEO. L. FOWLER. Revised by
WM. W. Wood, Air-Brake Instructor. Just issued. Revised pocket edition.
It is out of the question to try and tell you about every subject that
is covered in this pocket edition of Locomotive Breakdowns. Just imagine
all the common troubles that an engineer may expect to happen some time,
and then add all of the unexpected ones, troubles that could occur, but
that you had never thought about, and you will find that they are all
treated with the very best methods of repair. Walschaert Locomotive
Valve Gear Troubles, Electric Headlight Troubles, as well as Questions
and Answers on the Air Brake are all included. 294 pages. 7th Revised
Edition. Fully illustrated. $1.00

LOCOMOTIVE CATECHISM. By ROBERT GRIMSHAW. The revised edition of
"Locomotive Catechism," by Robert Grimshaw, is a New Book from Cover to
Cover. It contains twice as many pages and double the number of
illustrations of previous editions. Includes the greatest amount of
practical information ever published on the construction and management
of modern locomotives. Specially Prepared Chapters on the Walschaert
Locomotive Valve Gear, the Air Brake Equipment and the Electric Head
Light are given. It commends itself at once to every Engineer and
Fireman, and to all who are going in tor examination or promotion. In
plain language, with full complete answers, not only all the questions
asked by the examining engineer are given, but those which the young and
less experienced would ask the veteran, and which old hands ask as
"stickers." It is a veritable Encyclopedia of the Locomotive, is
entirely free from mathematics, easily, understood and thoroughly
up-to-date. Contains over 4,000 Examination Questions with their
Answers. 825 pages, 437 illustrations and three folding plates. 28th
Revised Edition. $2.50

PRACTICAL INSTRUCTOR AND REFERENCE BOOK FOR LOCOMOTIVE FIREMEN AND
ENGINEERS. By CHAS. F. LOCKHART. An entirely new book on the Locomotive.
It appeals to every railroad man, as it tells him how things are done
and the right way to do them. Written by a man who has had years of
practical experience in locomotive shops and on the road firing and
running. The information given in this book cannot be found in any other
similar treatise. Eight hundred and fifty-one questions with their
answers are included, which will prove specially helpful to those
preparing for examination. Practical information on: The Construction
and Operation of Locomotives. Breakdowns and their Remedies; Air. Brakes
and Valve Gears. Rules and Signals are handled in a thorough manner. As
a book of reference it cannot be excelled. The book is divided into six
parts, as follows: 1. The Fireman's Duties. 2. General description of
the Locomotive. 3. Breakdowns and their Remedies. 4. Air Brakes. 5.
Extracts from Standard Rules. 6. Questions for examination. The 851
questions have been carefully selected and arranged. These cover the
examinations required by the different railroads. 368 pages. 88
illustrations. Price $1.50

PREVENTION OF RAILROAD ACCIDENTS, OR SAFETY IN RAILROADING. By GEORGE
BRADSHAW. This book is a heart-to-heart talk with Railroad Employees,
dealing with facts, not theories, and showing the men in the ranks, from
every-day experience, how accidents occur and how they may be avoided.
The book is illustrated with seventy original photographs and drawings
showing the safe and unsafe methods of work. No visionary schemes, no
ideal pictures. Just plain facts and Practical Suggestions are given.
Every railroad employee who reads the book is a better and safer man to
have in railroad service. It gives just the information which will be
the means of preventing many injuries and deaths. All railroad employees
should procure a copy, read it, and do your part in preventing
accidents. 169 pages. Pocket Size. Fully illustrated. Price 50 cents.

TRAIN RULE EXAMINATIONS MADE EASY. By G. E. COLLINGWOOD. This is the
only practical work on train-rules in print. Every detail is covered,
and puzzling points are explained in simple, comprehensive language,
making it a practical treatise for the Train Dispatcher, Engineman,
Trainman, and all others who have to do with the movements of trains.
Contains complete and reliable information of the Standard Code of
Train. Rules for single track. Shows Signals in Colors, as used on the
different roads. Explains fully the practical application of train
orders, giving a clear and definite understanding of all orders which
may be used. The meaning and necessity for certain rules are explained
in such a manner that the student may know beyond a doubt the rights
conferred under any orders he may receive or the action required by
certain rules. As nearly all roads require trainmen to pass regular
examinations, a complete set of examination questions, with their
answers, are included. These will enable the student to pass the
required examinations with credit to himself and the road for which he
works.

256 pages. Fully illustrated with Train Signals in colors. Price $1.26

TRAIN RULES AND DESPATCHING. By H. A. DALBY. Every railroad man, no
matter what department he's in, needs a copy of this book. It gives the
standard rules for both single and double track, shows all the signals,
with colors wherever necessary, and has a list of towns where time
changes, with a map showing the whole country. The rules are explained
wherever there is any doubt about their meaning or where they are
modified by different railroads. It's the only practical book on train
rules in print. Over 220 pages. Leather cover. Price $1.50

THE WALSCHAERT AND OTHER MODERN RADIAL VALVE GEARS FOR LOCOMOTIVES. By
WM. W. Wood. If you would thoroughly understand the Walschaert Valve
Gear you should possess a copy of this book, as the author takes the
plainest form of a steam engine-a stationary engine in the rough, that
will only turn its crank in one direction and from it builds up—with the
reader's help—a modern locomotive equipped with the Walschaert Valve
Gear, complete. The points discussed are clearly illustrated; two large
folding plates that show the positions of the valves of both inside or
outside admission type, as well as the links and other parts of the gear
when the crank is at nine different points in its revolution, are
especially valuable in making the movement clear. These employ sliding
cardboard models which are contained in a pocket in the cover. The book
is divided into five general divisions, as follows: I. Analysis of the
gear. II. Designing and erecting the gear. III. Advantages of the gear.
IV. Questions and answers relating to the Walschaert Valve Gear. V.
Setting valves with the Walschaert Valve Gear; the three primary types
of locomotive valve motion; modern radial valve gears other than the
Walschaert; the Hobart All-free valve and valve gear, with questions and
answers on breakdowns; the Baker-Pilliod valve gear; the Improved
Baker-Pilliod Valve Gear, with questions and answers on breakdowns. The
questions with full answers given will be especially valuable to firemen
and engineers in preparing for an examination for promotion. 245 pages.
Third Revised Edition. Price $1.50

WESTINGHOUSE E-T AIR-BRAKE INSTRUCTION POCKET BOOK. By WM. W. Wood,
Air-Brake Instructor. Here is a book for the railroad man, and the man
who aims to be one. It is without doubt the only complete work published
on the Westinghouse E-T Locomotive Brake Equipment. Written by an Air
Brake Instructor who knows just what is needed. It covers the subject
thoroughly. Everything about the New Westinghouse Engine and Tender
Brake Equipment, including the Standard No. 5 and the Perfected No. 6
Style of brake, is treated in detail. Written in plain English and
profusely illustrated with Colored Plates, which enable one to trace the
flow of pressures throughout the entire equipment. The best book ever
published on the Air Brake. Equally good for the beginner and the
advanced engineer. Will pass any one through any examination. It informs
and enlightens you on every point. Indispensable to every engineman and
trainman. Contains examination questions and answers on the E-T
equipment. Covering what the E-T Brake is. How it should be operated.
What to do when defective. Not a question can be asked of the engineman
up for promotion on either the No. 5 or the No. 6 E-T equipment that is
not asked and answered in the book. If you want to thoroughly understand
the E-T equipment get a copy of this book. It covers every detail. Makes
Air Brake troubles and examinations easy. Price $1.50

MACHINE SHOP PRACTICE

AMERICAN TOOL MAKING AND INTERCHANGEABLE MANUFACTURING. By J. V.
WOODWORTH.

A "shoppy" book, containing no theorizing, no problematical or
experimental devices, there are no badly proportioned and impossible
diagrams, no catalogue cuts, but a valuable collection of drawings and
descriptions of devices, the rich fruits of the author's own experience.
In its 500-odd pages the one subject only, Tool Making, and whatever
relates thereto, is dealt with. The work stands without a rival. It is a
complete practical treatise on the art of American Tool Making and
system of interchangeable manufacturing as carried on to-day in the
United States. In it are described and illustrated all of the different
types and classes of small tools, fixtures, devices, and special
appliances which are in general use in all machine manufacturing and
metal working establishments where economy, capacity, and
interchangeability in the production of machined metal parts are
imperative. The science of jig making is exhaustively discussed, and
particular attention is paid to drill jigs, boring, profiling and
milling fixtures and other devices in which the parts to be machined are
located and fastened within the contrivances. All of the tools,
fixtures, and devices illustrated and described have been or are used
for the actual production of work, such as parts of drill presses,
lathes, patented machinery, typewriters, electrical apparatus,
mechanical appliances, brass goods, composition parts, mould products,
sheet metal articles, drop forgings, jewelry, watches, medals, coins,
etc. 531 pages. Price $4.00

HENLEY'S ENCYCLOPEDIA OF PRACTICAL ENGINEERING AND ALLIED TRADES. Edited
by JOSEPH G. HORNER, A.M.I., M.E. This set of five volumes contains
about 2,500 pages with thousands of illustrations, including
diagrammatic and sectional drawings with full explanatory details. This
work covers the entire practice of Civil and Mechanical Engineering. The
best known expert in all branches of engineering have contributed to
these volumes. The Cyclopedia is admirably well adapted to the needs of
the beginner and the self-taught practical man, as well as the
mechanical engineer, designer, draftsman, shop superintendent, foreman,
and machinist. The work will be found a means of advancement to any
progressive man. It is encyclopedic in scope, thorough and practical in
its treatment of technical subjects, simple and clear in its descriptive
matter, and without unnecessary technicalities or formulae. The articles
are as brief as may be and yet give a reasonably clear and explicit
statement of the subject, and are written by men who have had ample
practical experience in the matters of which they write. It tells you
all you want to know about engineering and tells it so simply, so
clearly, so concisely, that one cannot help but understand. As a work of
reference it is without a peer. $6.00 per volume. For complete set of
five volumes, price $25.00

MACHINE SHOP ARITHMETIC. By COLVIN-CHENEY. This is an arithmetic of the
things you have to do with daily. It tells you plainly about: how to
find areas of figures; how to find surface or volume of balls or
spheres; handy ways for calculating; about compound gearing; cutting
screw threads on any lathe; drilling for taps; speeds of drills, taps,
emery wheels, grindstones, milling cutters, etc.; all about the Metric
system with conversion tables; properties of metals; strength of bolts
and nuts; decimal equivalent of an inch. All sorts of machine shop
figuring and 1,001 other things, any one of which ought to be worth more
than the price of this book to you, and it saves you the trouble of
bothering the boss. 6th Edition. 131 pages. Price 50 cents.

MODERN MACHINE SHOP CONSTRUCTION, EQUIPMENT AND MANAGEMENT. By OSCAR E.
PERRIGO. The only work published that describes the Modern Machine Shop
or Manufacturing Plant from the time the grass is growing on the site
intended for it until the finished product is shipped. Just the book
needed by those contemplating the erection of modern shop buildings, the
rebuilding and reorganization of old ones, or the introduction of Modern
Shop Methods, time and cost systems. It is a book written and
illustrated by a practical shop man for practical shop men who are too
busy to read theories and want facts. It is the most complete all-around
book of its kind ever published. 400 large quarto pages. 225 original
and specially-made illustrations. Price $5.00

MECHANICAL APPLIANCES, MECHANICAL MOVEMENTS AND NOVELTIES OF
CONSTRUCTION. By GARDNER D. HISCOX. This is a supplementary volume to
the one upon mechanical movements. Unlike the first volume, which is
more elementary in character, this volume contains illustrations and
descriptions of many combinations of motions and of mechanical devices
and appliances found in different lines of machinery. Each device being
shown by a line drawing with a description showing its working parts and
the method of operation. From the multitude of devices described, and
illustrated, might be mentioned, in passing, such items as conveyors and
elevators, Prony brakes, thermometers, various types of boilers, solar
engines, oil-fuel burners, condensers, evaporators, Corliss and other
valve gears, governors, gas engines, water motors of various
descriptions, air ships, motors and dynamos, automobile and motor
bicycles, railway block signals, car couplers, link and gear motions,
ball bearings, breech block mechanism for heavy guns, and a large
accumulation of others of equal importance. 1,000 specially made
engravings. 396 octavo pages. Price $2.50

MECHANICAL MOVEMENTS, POWERS, AND DEVICES. By GARDNER D. HISCOX. This is
a collection of 1,890 engravings of different mechanical motions and
appliances, accompanied by appropriate text, making it a book of great
value to the inventor, the draftsman, and to all readers with mechanical
tastes. The book is divided into eighteen sections or chapters in which
the subject matter is classified under the following heads: Mechanical
Powers; Transmission of Power; Measurement of Power, Steam Power; Air
Power Appliances; Electric Power and Construction, Navigation and Roads;
Gearing; Motion and Devices; Controlling Motion; Horological; Mining;
Mill and Factory Appliances; Construction and Devices; Drafting Devices:
Miscellaneous Devices, etc. 12th edition. 400 octavo pages. Price $2.50

MACHINE SHOP TOOLS AND SHOP PRACTICE. By W. H. VANDERVOORT. A work of
555 pages and 673 illustrations, describing in every detail the
construction, operation, and manipulation of both hand and machine
tools. Includes chapters on filing, fitting, and scraping surfaces; on
drills, reamers, taps, and dies; the lathe and its tools; planers,
shapers, and their tools; milling machines and cutters; gear cutters and
gear cutting; drilling machines and drill work; grinding machines and
their work; hardening and tempering; gearing, belting and transmission
machinery: useful data and tables. 6th edition, Price $3.00

THE MODERN MACHINIST. By JOHN T. USHER. This is a book showing, by plain
description and by profuse engravings, made expressly for the work, all
that is best, most advanced, and of the highest efficiency in modern
machine shop practice, tools, and implements, showing the way by which
and through which, as Mr. Maxim says, "American machinists have become
and are the finest mechanics in the world." Indicating as it does, in
every line, the familiarity of the author with every detail of daily
experience in the shop, it cannot fail to be of service to any man
practically connected with the shaping or finishing of metals. There is
nothing experimental or visionary about the book, all devices being in
actual use and giving good results. It might be called a compendium of
shop methods, showing a variety of special tools and appliances which
will give new ideas to many mechanics, from the superintendent down to
the man at the bench. It will be found a valuable addition to any
machinist's library, and should be consulted whenever a new or difficult
job is to be done, whether it is boring, milling, turning, or planing,
as they are all treated in a practical manner. Fifth Edition. 320 pages.
250 illustrations. Price $2.50

MODERN MILLING MACHINES: THEIR DESIGN, CONSTRUCTION AND OPERATION. By
JOSEPH G. HORNER. This book describes and illustrates the Milling
Machine and its work in such a plain, clear, and forceful manner, and
illustrates the subject so clearly and completely, that the up-to-date
machinist, student, or mechanical engineer cannot afford to do without
the valuable information which it contains. It describes not only the
early machines of this class, but notes their gradual development into
the splendid machines of the present day, giving the design and
construction of the various types, forms, and special features produced
by prominent manufacturers, American and foreign. Milling cutters in all
their development and modernized forms are illustrated and described,
and the operations they are capable of producing upon different classes
of work are carefully described in detail, and the speeds and feeds
necessary are discussed, and valuable and useful data given for
determining these usually perplexing problems. The book is the most
comprehensive work published on the subject. 304 pages. 300
illustrations. Price $4.00

"SHOP KINKS." By ROBERT GRIMSHAW. A book of 400 pages and 222
illustrations, being entirely different from any other book on machine
shop practice. Departing from conventional style, the author avoids
universal or common shop usage and limits his work to showing special
ways of doing things better, more cheaply and more rapidly than usual.
As a result the advanced methods of representative establishments of the
world are placed at the disposal of the reader. This book shows the
proprietor where large savings are possible, and how products may be
improved. To the employee it holds out suggestions that, properly
applied, will hasten his advancement. No shop can afford to be without
it. It bristles with valuable wrinkles and helpful suggestions, It will
benefit all, from apprentice to proprietor. Every machinist, at any age,
should study its pages. Fifth Edition. Price $2.50

THREADS AND THREAD CUTTING. By COLVIN and STABEL. This clears up many of
the mysteries of thread-cutting, such as double and triple threads,
internal threads, catching threads, use of hobs, etc. Contains a lot of
useful hints and several tables. 3rd Edition. Price 25 cents.

TOOLS FOR MACHINISTS AND WOOD WORKERS, INCLUDING INSTRUMENTS OF
MEASUREMENT. By JOSEPH G. HORNER. The principles upon which cutting
tools for wood, metal, and other substances are made are identical,
whether used by the machinist, the carpenter, or by any other skilled
mechanic in their daily work, and the object of this book is to give a
correct and practical description of these tools as they are commonly
designed, constructed, and used. 340 pages, fully illustrated. Price
$3.50

MANUAL TRAINING

ECONOMICS OF MANUAL TRAINING. By LOUIS ROUILLION. The only book
published that gives just the information needed by all interested in
Manual Training, regarding Buildings, Equipment, and Supplies. Shows
exactly what is needed for all grades of the work from the Kindergarten
to the High and Normal School. Gives itemized lists of everything used
in Manual Training Work and tells just what it ought to cost. Also shows
where to buy supplies, etc. Contains 174 pages, and is fully
illustrated. 2nd Edition. Price $1.50

MARINE ENGINEERING

MARINE ENGINES AND BOILERS, THEIR DESIGN AND CONSTRUCTION. By Dr. G.
BAUER, LESLIE S. ROBERTSON, and S. BRYAN DONKIN. in the words of. Dr.
Bauer, the present work owes its origin to an oft felt want of a
Condensed Treatise, embodying the Theoretical and Practical Rules used
in Designing Marine Engines and Boilers. The need for such a work has
been felt by most engineers engaged in the construction and working of
Marine Engines, not only by the younger men, but also by those of
greater experience. The fact that the original German work was written
by the chief engineer of the famous Vulcan Works, Stettin, is in itself
a guarantee that this book is in all respects thoroughly up-to-date, and
that it embodies all the information which is necessary for the design
and construction of the highest types of marine engines and boilers. It
may be said that the motive power which Dr. Bauer has placed in the
fast German liners that have been turned out of late years from the
Stettin Works, represent the very best practice in marine engineering of
the present day. This work is clearly written, thoroughly systematic,
theoretically sound; while the character of its plans, drawings, tables,
and statistics is without reproach. The illustrations are careful
reproductions from actual working drawings, with some well-executed
photographic views of completed engines and boilers.

550 illustrations and numerous tables. $9.00 net

MODERN SUBMARINE CHART. A cross-section view, showing clearly and
distinctly all the interior of a Submarine of the latest type. You get
more information from this chart, about the construction and operation
of a Submarine, than in any other way. No Details omitted-everything is
accurate and to scale. It is absolutely correct in every detail, having
been approved by Naval Engineers. All the machinery and devices fitted
in a modern Submarine Boat are shown and to make the engraving more
readily understood all the features are shown in operative form with
Officers and Men in the act of performing the duties assigned to them in
service conditions. This CHART IS REALLY AN ENCYCLOPEDIA OF A SUBMARINE.
It is educational and worth many times its cost. Mailed in a Tube for 25
cents. 744 pages.

MINING

ORE DEPOSITS, WITH A CHAPTER ON HINTS TO PROSPECTORS. By J. P. JOHNSON
This book gives a condensed account of the ore-deposits at present known
in South Africa. It is also intended as a guide to the prospector. Only
an elementary knowledge of geology and some mining experience are
necessary in order to understand this work. With these qualifications,
it will materially assist one in his search for metalliferous mineral
occurrences and, so far as simple ores are concerned, should enable one
to form some idea of the possibilities of any he may find. Among the
chapters given are: Titaniferous and Chromiferous Iron
Oxides–Nickel–Copper–Cobalt–Tin–Molybdenum–Tungsten–Lead–Mercury
–Antimony–Iron-Hints to Prospectors. $2.00

PHYSICS AND CHEMISTRY OF MINING. By T. H. BYROM. A practical work for
the use of all preparing for examinations in mining or qualifying for
colliery managers' certificates. The aim of the author in this excellent
book is to place clearly before the reader useful and authoritative data
which will render him valuable assistance in his studies. The only work
of its kind published. The information incorporated in it will prove of
the greatest practical utility to students, mining engineers, colliery,
managers, and all others who are specially interested in the present-day
treatment of mining problems. Among its contents are chapters on: The
Atmosphere; Laws Relating to the Behavior of Gases; The Diffusion of
Gases; Composition of the Atmosphere: Sundry Constituents of the
Atmosphere; Water; Carbon; Fire-Damp; Combustion; Coal Dust and Its
Action; Explosives; Composition of Various Coals and Fuels; Methods of
Analysis of Coal; Strata Adjoining the Coal Measures; Magnetism and
Electricity; Appendix; Useful Tables, etc.; Miscellaneous Questions. 160
pages. Illustrated. $2.00

PRACTICAL COAL MINING. By T. H. COCKIN. An important work, containing
428 pages and 213 illustrations, complete with practical details, which
will intuitively impart to the reader, not only a general knowledge of
the principles of coal mining, but also considerable insight into allied
subjects. This treatise is positively up to date in every instance, and
should be in the hands of every colliery engineer, geologist, mine
operator, superintendent, foreman, and all others who are interested in
or connected with the industry. 2nd Edition. $2.50

PATTERN MAKING

PRACTICAL PATTERN MAKING. By F. W. BARROWS. This is a very complete and
entirely practical treatise on the subject of pattern making,
illustrating pattern work in wood and metal. From its pages you are
taught just what you should know about pattern making. It contains a
detailed description of the materials used by pattern makers, also the
tools, both those for hand use, and the more interesting machine tools;
having complete chapters on the band saw, The Buzz Saw, and the Lathe.
Individual patterns of many different kinds are fully illustrated and
described, and the mounting of metal patterns on plates for molding
machines is included. Rules, Formulas and Tables are included,
containing simple and original methods for finding the weight of
castings, both from the pattern itself and from the drawings. This
section contains some new and practical formulas, which will be found
very useful in estimating weights, with the accuracy required for
quotations to prospective customers. Ali of these rules are simple, and
can be put to practical use by the ordinary, every-day man, and they
have been proved by years of actual use. Plain rules for keeping down
the cost of patterns, with a complete system for checking the cost of
and marking the patterns, and a card record showing what the pattern is,
material used, where located in safe, with its cost and date of
production, is included. The book closes with an original and practical
method for the inventory and valuation of patterns. Containing 326 pages
and 150 detailed illustrations. Price $2.00

PERFUMERY

HENLEY'S TWENTIETH CENTURY BOOK OF RECEIPTS, FORMULAS AND PROCESSES.
Edited by G. D. HISCOX. The most valuable Techno-chemical Receipt Book
published. Contains over 10,000 practical receipts, many of which will
prove of special value to the perfumer, a mine of information,
up-to-date in every respect. Price, Cloth, $3.00; half morocco $4.00

PERFUMES AND THEIR PREPARATION. By G. W. ASKINSON, Perfumer. A
comprehensive treatise, in which there has been nothing omitted that
could be of value to the Perfumer. Complete directions for making
handkerchief perfumes, smelling-salts, sachets, fumigating pastilles:
preparations for the care of the skin, the mouth, the hair, cosmetics,
hair dyes and other toilet articles are given, also a detailed
description of aromatic substances: their nature, tests of purity, and
wholesale manufacture. A book of general, as well as professional
interest, meeting the wants not only of the druggist and perfume
manufacturer, but also of the general public. Third edition. 312 pages.
Illustrated. $3.00

PLUMBING

MECHANICAL DRAWING FOR PLUMBERS. By R. M. STARBUCK. A concise,
comprehensive and practical treatise on the subject of mechanical
drawing in its various modern applications to the work of all who are in
any way connected with the plumbing trade. Nothing will so help the
plumber in estimating and in explaining work to customers and workmen as
a knowledge of drawing, and to the workman it is of inestimable value if
he is to rise above his position to positions of greater responsibility,
Among the chapters contained are: 1. Value to plumber of knowledge of
drawing; tools required and their use; common views needed in mechanical
drawing. 2. Perspective versus mechanical drawing in showing plumbing
construction. 3. Correct and incorrect methods in plumbing drawing; plan
and elevation explained. 3. Floor and cellar plans and elevation; scale
drawings; use of triangles. 5. Use of triangles; drawing of fittings,
traps, etc. 6. Drawing plumbing elevations and fittings. 7. Instructions
in drawing plumbing elevations. 8. The drawing of plumbing fixtures;
scale drawings. 9. Drawing of fixtures and fittings. 10. Inking of
drawings. 11. Shading of drawings. 12. Shading of drawings. 13.
Sectional drawings; drawing of threads. 14. Plumbing elevations from
architect's plan. 15. Elevations of separate parts of the plumbing
system. 16. Elevations from architect's plans. 17. Drawing of detail
plumbing connections. 18. Architect's plans and plumbing elevations of
residence. 19. Plumbing elevations of residence (continued); plumbing
plans for cottage. 20. Plumbing elevations; roof connections. 21. Plans
and plumbing elevations for six-flat building. 22. Drawing of various
parts of the plumbing system; use of scales. 23. Use of architect's
scales. 24. Special features in the illustrations of country plumbing.
25. Drawing of wrought iron piping, valves, radiators, coils, etc. 26.
Drawing of piping to illustrate heating systems. 150 illustrations.
Price $1.50

MODERN PLUMBING ILLUSTRATED. By R. M. STARBUCK. This book represents the
highest standard of plumbing work. It has been adopted and used as a
reference book by the United States Government, in its sanitary work in
Cuba, Porto Rico, and the Philippines, and by the principal Boards of
Health of the United States and Canada. It gives connections, sizes and
working data for all fixtures and groups of fixtures. It is helpful to
the master plumber in demonstrating to his customers and in figuring
work. It gives the mechanic and student quick and easy access to the
best modern plumbing practice. Suggestions for estimating plumbing
construction are contained in its pages. This book represents, in a
word, the latest and best up-to-date practice, and should be in the
hands of every architect, sanitary engineer and plumber who wishes to
keep himself up to the minute on this important feature of construction.
Contains following chapters, each illustrated with a full-page plate:
Kitchen sink, laundry tubs, vegetable wash sink; lavatories, pantry
sinks, contents of marble slabs; bath tub, foot and sitz bath, shower
bath; water closets, venting of water closets; low-down water closets,
water closets operated by flush valves, water closet range; slop sink,
urinals, the bidet: hotel and restaurant sink, grease trap;
refrigerators, safe wastes, laundry waste; lines of refrigerators, bar
sinks, soda fountain sinks; horse stall, frost-proof water closets;
connections for S traps, venting; connections for drum traps; soil pipe
connections; supporting of soil pipe; main trap and fresh air inlet;
floor drains and cellar drains, subsoil drainage; water closets and
floor connections; local venting; connections for bath rooms;
connections for bath rooms, continued; connections for bath rooms,
continued; connections for bath rooms, continued; examples of poor
practice; roughing-work ready for test; testing of plumbing system;
method of continuous venting; continuous venting for two-floor work;
continuous venting for two lines of fixtures on three or more floors;
continuous venting of water closets; plumbing for cottage house;
construction for cellar piping; plumbing for residence, use of special
fittings; plumbing for two-flat house; plumbing for apartment building;
plumbing for double apartment building; plumbing for office building;
plumbing for public toilet rooms; plumbing for public toilet rooms,
continued; plumbing for bath establishment; plumbing for engine house,
factory plumbing; automatic flushing for schools, factories, etc.; use
of flushing valves; urinals for public toilet rooms; the Durham system,
the destruction of pipes by electrolysis; construction of work without
use of lead; Automatic sewage lift, automatic sump tank; country
plumbing; construction of cesspools; septic tank and automatic sewage
siphon; country plumbing; water supply for country house; thawing of
water mains and service by electricity; double boilers; hot water supply
of large buildings; automatic control of hot water tank; suggestions for
estimating plumbing construction. 400 octavo pages, fully illustrated by
55 full-page engravings. Price $4.00

STANDARD PRACTICAL PLUMBING. By R. M. STARBUCK. A complete practical
treatise of 450 pages covering the subject of Modern Plumbing in all its
branches, a large amount of space being devoted to a very complete and
practical treatment of the subject of Hot Water Supply and Circulation
and Range Boiler Work. Its thirty chapters include about every phase of
the subject one can think of, making it an indispensable work to the
master plumber, the journeyman plumber, and the apprentice plumber,
containing chapters on: the plumber's tools; wiping solder, composition
and use; joint wiping; lead work; traps; siphonage of traps; venting;
continuous venting; house sewer and sewer connections; house drain; soil
piping, roughing; main trap and fresh air inlet;' floor, yard, cellar
drains, rain leaders, etc.; fixture wastes: water closets; ventilation;
improved plumbing connections; residence plumbing; plumbing for hotels,
schools, factories, stables, etc.; modern country plumbing; filtration
of sewage and water supply; hot and cold supply; range boilers;
circulation; circulating, pipes; range boiler problems; hot water for
large buildings; water lift and its use; multiple connections for hot
water boilers; heating of radiation by supply system; theory for the
plumber; drawing for the plumber. Fully illustrated by 347 engravings.
Price $3.00

RECEIPT BOOK

HENLEY'S TWENTIETH CENTURY BOOK OF RECEIPTS, FORMULAS AND PROCESSES.
Edited by GARDNER D. HISCOX. The most valuable Techno-chemical Receipt
Book published, including over 10,000 selected scientific, chemical,
technological, and practical receipts and processes. This is the most
complete Book of Receipts ever published, giving thousands of receipts
for the manufacturer of valuable articles for everyday use. Hints,
Helps, Practical Ideas, and Secret Processes are revealed within its
pages. It covers every branch of the useful arts and tells thousands of
ways of making money an just the book everyone should have at his
command. Modern in its treatment of every subject that properly falls
within its scope, the book may truthfully be said to present the very
latest formulas to be found in the arts and industries and to retain
those processes which long experience has proven worthy of a permanent
record. To present here even a limited number of the subjects which find
a place in this valuable work would be difficult. Suffice to say that in
its pages will be found matter of intense interest and immeasurable
practical value to the scientific amateur and to him who wishes to
obtain a knowledge of the many processes used in the arts, trades and
manufactures, a knowledge which will render his pursuits more
instructive and remunerative. Serving as a reference book to the small
and large manufacturer and supplying intelligent seekers with the
information necessary to conduct a process, the work will be found of
inestimable worth to the Metallurgist, the Photographer, the Perfumer,
the Painter, the Manufacturer of Glues, Pastes, Cements, and Mucilages,
the Compounder of Alloys, the Cook, the Physician, the Druggist, the
Electrician, the Brewer, the Engineer, the Foundryman, the Machinist,
the Potter, the Tanner, the Confectioner, the Chiropodist, the Manicure,
the Manufacturer of Chemical Novelties and Toilet Preparations, the
Dyer, the Electroplater, the Enameler, the Engraver, the Provisioner,
the Glass Worker, the Goldbeater, the Watchmaker, the Jeweler, the Hat
Maker, the Ink Manufacturer, the Optician, the Farmer, the Dairyman, the
Paper Maker, the Wood and Metal Worker, the Chandler and Soap Maker, the
Veterinary Surgeon, and the Technologist in general. A mine of
information, and up-to-date in every respect. A book which will prove of
value to EVERYONE, as it covers every branch of the Useful Arts. 800
pages. Price $3.00

WHAT IS SAID OF THIS BOOK:

"Your Twentieth Century Book of Receipts, Formulas and Processes duly
received. I am glad to have a copy of it, and if I could not replace it
money couldn't buy it. It is the best thing of the sort I ever saw."
(Signed) M. E. TRUX, Sparta, Wis. "There are few persons who would not
be able to find in the book some single formula that would repay several
times the cost of the book." Merchant's Record and Show Window.

RUBBER

RUBBER HAND STAMPS AND THE MANIPULATION OF INDIA RUBBER.

By T. O'CONOR SLOANE. This book gives full details on all points,
treating in a concise and simple manner the elements of nearly
everything it is necessary to understand for a commencement in any
branch of the India Rubber Manufacture. The making of all kinds of
Rubber Hand Stamps, Small Articles of India Rubber, U. S. Government
Composition, Dating Hand Stamps, the Manipulation of Sheet Rubber, Toy
Balloons, India Rubber Solutions, Cements, Blackings, Renovating
Varnish, and Treatment for India Rubber Shoes, etc.; the Hektograph
Stamp Inks, and Miscellaneous Notes, with a Short Account of the
Discovery, Collection, and Manufacture of India Rubber are set forth in
a manner designed to be readily understood, the explanations being plain
and simple. Including a chapter on Rubber Tire Making and Vulcanizing;
also a chapter on the uses of rubber in Surgery and Dentistry. Third
revised and enlarged edition 175 pages. Illustrated. $1.00

SAWS

SAW FILINGS AND MANAGEMENT OF SAWS. By ROBERT GRIMSHAW. A practical hand
book on filing, gumming, swaging, hammering, and the brazing of band
saws, the speed, work, and power to run circular saws, etc. A handy book
for those who have charge of saws, or for those mechanics who do their
own filing, as it deals with the proper shape and pitches of saw teeth
of all kinds and gives many useful hints and rules for gumming, setting,
and tiling, and is a practical aid to those who use saws for any
purpose. New edition, revised and enlarged. Illustrated. Price $1.00

STEAM ENGINEERING

AMERICAN STATIONARY ENGINEERING. By W. E. CRANE. This book begins at the
boiler room and takes in the whole power plant. A plain talk on
every-day work about engines, boilers, and their accessories. It is not
intended to be scientific or mathematical. All formulas are in simple
form so that any one understanding plain arithmetic can readily
understand any of them. The author has made this the most practical book
in print; has given the results of his years of experience, and has
included about all that has to do with an engine room or a power plant.
You are not left to guess at a single point. You are shown clearly what
to expect under the various conditions; how to secure the best results;
ways of preventing "shut downs" and repairs; in short, all that goes to
make up the requirements of a good engineer, capable of taking charge of
a plant. It's plain enough for practical men and yet of value to those
high in the profession. A partial list of contents is: The boiler room,
cleaning boilers, firing, feeding; pumps; inspection and repair;
chimneys, sizes and cost; piping; mason work; foundations; testing
cement; pile driving; engines, slow and high speed; valves; valve
setting; Corliss engines, setting valves, single and double eccentric;
air pumps and condensers; different types of condensers; water needed;
lining up; pounds; pins not square in crosshead or crank; engineers'
tools; pistons and piston rings; bearing metal; hardened copper; drip
pipes from cylinder jackets; belts, how made, care of; oils; greases;
testing lubricants; rules and tables, including steam tables; areas of
segments; squares and square root; cubes and cube root; areas and
circumferences of circles. Notes on: Brick work; explosions; pumps; pump
valves; heaters, economizers; safety valves; lap, lead, and clearance.
Has a complete examination for a license, etc., etc. Second edition. 285
pages. Illustrated. Price $2.00

EMINENT ENGINEERS. By DWIGHT GODDARD. Everyone who appreciates the
effect of such great inventions as the Steam Engine, Steamboat,
Locomotive, Sewing Machine, Steel Working, and other fundamental
discoveries, is interested in knowing a little about the men who made
them and their achievements. Mr. Goddard has selected thirty-two of the
world's engineers who have contributed most largely to the advancement
of our civilization by mechanical means, giving only such facts as are
of general interest and in a way which appeals to all, whether mechanics
or not. 280 pages. 35 illustrations. Price $1.50

ENGINE RUNNER'S CATECHISM. By ROBERT GRIMSHAW. A practical treatise for
the stationary engineer, telling how to erect, adjust and run the
principal stearn engines in use in the United States. Describing the
principal features of various special and well-known makes of engines:
Temper Cut-off, Shipping and Receiving Foundations, Erecting and
Starting, Valve Setting, Care and Use, Emergencies, Erecting and
Adjusting Special Engines. The questions asked throughout the catechism
are plain and to the point, and the answers are given in such simple
language as to be readily understood by anyone. All the instructions
given are complete ad up-to-date; and they are written in a popular
style, without any technicalities or mathematical formulae. The work is
of a handy size for the pocket, clearly and well printed, nicely bound,
and profusely illustrated. To young engineers this catechism will be of
great value, especially to those who may be preparing to go forward to
be examined for certificates of competency; and to engineers generally
it will be of no little service, as they will find in this volume more
really practical and useful information than is to be found anywhere
else within a like compass. 387 pages. Seventh edition. Price $2.00

ENGINE TESTS AND BOILER EFFICIENCIES. By J. BUCHETTI. This work fully
describes and illustrates the method of testing the power of steam
engines, turbines and explosive motors. The properties of steam and the
evaporative power of fuels. Combustion of fuel and chimney draft; with
formulas explained or practically computed 255 pages, 179 illustrations.
$3.00

HORSEPOWER CHART. Shows the horsepower of any stationary engine without
calculation. No matter what the cylinder diameter of stroke; the steam
pressure or cut off; the revolutions, or whether condensing or
non-condensing, it's all there. Easy to use, accurate, and saves time
and calculations. Especially useful to engineers and designers. 50
cents.

MODERN STEAM ENGINEERING IN THEORY AND PRACTICE. By GARDNER D. HISCOX.
This is a complete and practical work issued for Stationary Engineers
and firemen dealing with the care and management of boilers, engines,
pumps, superheated steam, refrigerating machinery, dynamos, motors,
elevators, air compressors, and all other branches with which the modern
engineer must be familiar. Nearly 200 questions with their answers on
steam and electrical engineering, likely to be asked by the Examining
Board, are included. Among the chapters are: Historical; steam and its
properties; appliances for the generation of steam; types of boilers;
chimney and its work; heat economy of the feed water; steam pumps and
their work; incrustation and its work; steam above atmospheric pressure;
flow of steam from nozzles; superheated steam and its work; adiabatic
expansion of steam; indicator and its work; steam engine proportions;
slide valve engines and valve motion; Corliss engine and its valve gear;
compound engine and its theory; triple and multiple expansion engine.
steam turbine; refrigeration; elevators and their management; cost of
power; steam engine troubles; electric power and electric plants. 487
pages. 405 engravings. Price $3.00

STEAM ENGINE CATECHISM. By ROBERT GRIMSHAW. This unique volume of 413
pages is not only a catechism on the question and answer principle; but
it contains formulas and worked-out answers for all the Steam problems
that appertain to the operation and management of the Steam Engine.
Illustrations of various valves and valve gear with their principles of
operation are given. Thirty-four Tables that are indispensable to every
engineer and fireman that wishes to be progressive and is ambitious to
become master of his calling are within its pages. It is a most valuable
instructor in the service of Steam Engineering. Leading engineers have
recommended it as a valuable educator for the beginner as well as a
reference book for the engineer. It is thoroughly indexed for every
detail. Every essential question on the Steam Engine with its answer is
contained in this valuable work. Sixteenth edition. Price $2.00

STEAM ENGINEER’S ARITHMETIC. By COLVIN-CHENEY. A practical pocket book
for the steam engineer. Shows how to work the problems of the engine
room and shows "why." Tells how to figure horse-power of engines and
boilers; area of boilers; has tables of areas and circumferences; steam
tables; has a dictionary of engineering terms. Puts you on to all all of
the little kinks in figuring whatever there is to figure around a power
plant. Tells you about the heat unit; absolute zero; adiabatic
expansion; duty of engines; factor of safety; and 1,001 other things;
and everything is plain and simple--not the hardest way to figure, but
the easiest. 2nd Edition. 50 cents.

STEAM HEATING AND VENTILATION

PRACTICAL STEAM, HOT-WATER HEATING AND VENTILATION. By A. G. KING.

This book is the standard and latest work published on the subject and
has been prepared for the use of all engaged in the business of steam,
hot water heating, and ventilation. It is an original and exhaustive
work. Tells how to get heating contracts, how to install heating and
ventilating apparatus, the best business methods to be used, with
"Tricks of the Trade" for shop use. Rules and data for estimating
radiation and cost and such tables and information as make it an
indispensable work for everyone interested in steam, hot water heating,
and ventilation. It describes all the principal systems of steam, hot
water, vacuum, vapor, and vacuum-vapor heating, together with the new
accelerated systems of hot water circulation, including chapters on
up-to-date methods of ventilation and the fan or blower system of
heating and ventilation. Containing chapters on: I. Introduction. II.
Heat. III. Evolution of artificial heating apparatus. IV. Boiler surface
and settings. V. The chimney flue. VI. Pipe and fittings. VII. Valves,
various kinds. VIII. Forms of radiating surfaces. IX. Locating of
radiating surfaces. X. Estimating radiation. XI. Steam-heating
apparatus. XII. Exhaust-steam heating. XIII. Hot-water heating. XIV.
Pressure systems of hot-water work. XV. Hot-water appliances. XVI.
Greenhouse heating. XVII. Vacuum vapor and vacuum exhaust heating.
XVIII. Miscellaneous heating. XIX. Radiator and pipe connections. XX.
Ventilation. XXI. Mechanical ventilation and hot-blast heating. XXII.
Steam appliances. XXIII. District heating. XXIV. Pipe and boiler
covering. XXV. Temperature regulation and heat, control. XXVI. Business
methods. XXVII. Miscellaneous. XXVII. Rules, tables and useful
information. 367 pages. 300 detailed engravings. Price $3.00

STEAM PIPES

STEAM PIPES: THEIR DESIGN AND CONSTRUCTION. By WM. H. BOOTH. The work is
well illustrated in regard to pipe joints, expansion offsets, flexible
joints, and self-contained sliding joints for taking up the expansion of
long pipes. In fact, the chapters on the flow of steam and expansion of
pipes are most valuable to all steam fitters and users. The pressure
strength of pipes and method of hanging them are well treated and
illustrated. Valves and by-passes are fully illustrated and described,
as are also flange joints and their proper proportions, exhaust heads
and separators. One of the most valuable chapters is that on superheated
steam and the saving of steam by insulation with the various kinds of
felting and other materials with comparison tables of the loss of heat
in thermal units from naked and felted steam pipes. Contains 187 pages.
Price $2.00

STEEL

AMERICAN STEEL WORKER. By E. R. MARKHAM. This book tells how to select,
and how to work, temper, harden, and anneal steel for everything on
earth. It doesn't tell how to temper one class of tools and then leave
the treatment of another kind of tool to your imagination and judgment,
but it gives careful instructions for every detail of every tool,
whether it be a tap, a reamer or just a screw-driver. It tells about
tempering of small watch springs, the hardening of cutlery, and the
annealing of dies. In fact there isn't a thing that a steel worker would
want to know that isn't included. It is the standard book on selecting,
hardening, and tempering all grades of steel. Among the chapter headings
might be mentioned the following subjects: Introduction; the workman;
steel; methods of heating; heating tool steel; forging; annealing;
hardening baths; baths for hardening; hardening steel; drawing the
temper after hardening; examples of hardening; pack hardening; case
hardening; spring tempering; making tools of machine steel; special
Steels; steel for various tools; causes of trouble; high speed steels,
etc. 366 pages. Illustrated. $2.50

HARDENING, TEMPERING, ANNEALING, AND FORGING OF STEEL. By J. V.
WOODWORTH. A new work treating in a clear, concise manner all modern
processes for the heating, annealing forging, welding, hardening, and
tempering of steel, making it a book of great practical value to the
metal-working mechanic in general, with special directions for the
successful hardening and tempering of all steel tools used in the arts,
including milling cutters, taps, thread dies, reamers, both solid and
shell, hollow mills, punches and dies, and all kinds of sheet metal
working tools, shear blades, saws, fine cutlery, and metal cutting tools
of all description, as well as for all implements of steel both large
and small. In this work the simplest and most satisfactory hardening and
tempering processes are given. The uses to which the leading brands of
steel may be adapted are concisely presented, and their treatment for
working under different conditions explained, also the special methods
for the hardening and tempering of special brands. A chapter devoted to
the different processes for Case-hardening is also included, and special
reference made to the adoption of machinery steel for tools of various
kinds. 4th Edition 288 pages. 201 Illustrations. Price $2.50

TURBINES

MARINE STEAM TURBINES. By DR. G. BAUER and O. LASCHE. Assisted by E.
Ludwig and H. Vogel. Translated from the German and edited by M. G. S.
Swallow. This work forms a supplementary volume to the book entitled
"Marine Engines and Boilers." The authors of this book, Dr. G. Bauer and
O. Lasche, may be regarded as the leading authorities on turbine
construction. The book is essentially practical and discusses turbines
in which the full expansion of steam passes through a number of separate
turbines arranged for driving two or more shafts, as in the Parsons
system, and turbines in which the complete expansion of steam from inlet
to exhaust pressure occurs in a turbine on one shaft, as in the case of
the Curtis machines. It will enable a designer to carry out all the
ordinary calculations necessary for the construction of steam turbines,
hence it fills a want which is hardly met by larger and more theoretical
works. Numerous tables, curves and diagrams will be found, which explain
with remarkable lucidity the reason why turbine blades are designed as
they are, the course which steam takes through turbines of various
types, the thermodynamics of steam turbine calculation, the influence of
vacuum on steam consumption of steam turbines, etc. In a word, the very
information which a designer and builder of steam turbines most
requires. The book is divided into parts as follows: 1. Introduction. 2.
General remarks on the design of a turbine installation. 3. The
calculation of steam turbines. 4. Turbine design. 5. Shafting and
propellers. 6. Condensing plant. 7. Arrangement of turbines. 8. General
remarks on the arrangement of steam turbines in steamers. 9.
Turbine-driven auxiliaries. 10. Tables. Large octavo. 214 pages. Fully
illustrated and containing 18 tables. Including an entropy chart. Price,
net, $3.60

WATCH MAKING

WATCHMAKER'S HANDBOOK. By CLAUDIUS SAUNIER. This famous work has now
reached its seventh edition and there is no work issued that can compare
to it for clearness and completeness. It contains 498 pages and is
intended as a workshop companion for those engaged in Watch-making and
allied Mechanical Arts. Nearly 250 engravings and fourteen plates are
included. Price $3.00


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