CHAPTER XVIII. THE AMATEUR AND THE WIRELESS LAW. WHAT IT IS; HOW TO

COMPLY; HOW TO SECURE A LICENSE.

On August 13, 1912, Congress enacted a "Wireless Law" to regulate radio communication. The whole law may be found in the appendix of this book, but briefly as far as the amateur is concerned it is as follows:

An amateur may not use transmitting apparatus which is sufficiently powerful to send radio signals across any of the boundaries of the state in which he is located and which can be detected by a sensitive receiving set located just beyond the state boundary, nor can he use apparatus which is powerful enough to interfere with the reception of signals by others from beyond the state boundaries unless he has a _license_.

An amateur may receive messages from anywhere at any time without a license provided that his station is not also fitted with transmitting apparatus.

In other words if the amateur possesses a receiving outfit only which is in working order or if he has both transmitter and receptor and the former is not powerful enough to send signals out of the state in which he lives, or to interfere with the reception of messages by another when the messages come from beyond the state boundary a _license_ is unnecessary.

This is of course somewhat unfair for those living near the center of large states for they may operate almost as they please with ordinary instruments with no fear of the signals going beyond the border, while those living within a few miles of another state must secure a license.

If an amateur has a license he may transmit messages beyond the state border, but he must not employ a wave length greater than 200 meters or a power input into the transmitter of more than 1 K.W. without special permission.

If the amateur is within five nautical miles of an army or navy station equipped with radio apparatus his power input must not be more than 1 K.W.

*Complying with Law.*—After a license is secured, or rather as a matter of fact in order to secure it, the wave length must not be greater than 200 meters. In order to secure such a wave length the effective portion of the aerial cannot usually be made greater than 115 feet in consideration of the amount which the lead-in, helix and ground wire add.

Such an aerial will serve well for transmitting purposes, but is too short for receiving very long distances. If the amateur desires to pick up long distance messages he must employ two aerials, a short one for transmitting and a long one for receiving. If it is desirable to use the long aerial for both transmitting and receiving its wave length may be brought down to 200 meters or under, while transmitting by placing a large glass plate condenser of the proper capacity in series with the aerial. It may be short-circuited with a suitable switch when receiving.

The law also says that the transmitting wave must be pure, and must be sharply tuned, which means that the wave must be of one length and not, as is very often the case, composed of two or more waves of different lengths.

In order to comply with this restriction, the use of an oscillation helix or loosely coupled helix is necessary. A rotary or quenched gap is also necessary in place of the ordinary spark gap.

The construction of all three of these instruments is described farther on.

*How to Obtain a License.*—In order to obtain a license send to the nearest Radio Inspector; Radio Inspectors are stationed at the Custom Houses at the following cities: Boston, Mass.; New York, N. Y.; Savannah, Ga.; Baltimore, Md.; Cleveland, Ohio; Chicago, Ill.; Seattle, Wash.; New Orleans, La.; San Francisco, Cal.; and obtain a copy of The Wireless Law, 8-6412, The Regulations Governing Radio Communication, The Berlin International Radio-telegraphic Convention, and the necessary Application Forms.

Look over the Wireless Law, the Regulations and the Berlin Convention pamphlet, then fill out Form 756. This is an application for an operator’s license.

If the amateur is not already in possession of a certificate of skill as an operator it will be necessary to find out, from the commandant at the nearest one of the stations, listed on page 4 of the Regulations as being the places where examinations are given, on what days the examinations are held. If the amateur is able to pass the examination, an _operator’s license_ will be issued. Then fill out Form 757 and forward it to the Radio Inspector. If he thinks your station conforms to the regulations without inspection the license will be issued; if not, the license will be issued after inspection.

There are no fees to pay in connection with securing any of the licenses.

APPARATUS REQUIRED IN MANY INSTANCES IN ORDER TO COMPLY WITH THE WIRELESS LAW.

*OSCILLATION HELIX*

The oscillation helix has almost become a necessity in order to comply with the regulations of the Wireless Law regarding wave form, except in those stations where a quenched gap is used.

The wave emitted by many stations is not pure. It is composed usually of two or three separate waves of different lengths instead of all the energy being confined to oscillations of one period. It is possible to tune such a wave in two or more places or "humps," as they are called, on the tuning coil. It is obvious that a wave possessing such humps cannot be closely tuned and is liable to interfere with the signals of another station. This is one of the principal causes of interference.

The reason for this phenomenon is simple. The action of a transmitter is to first charge a condenser. When the potential of the condenser rises to sufficient value it discharges across the spark gap and sets up oscillations in the _closed_ circuit. These oscillations immediately induce oscillations in the _open_ circuit or aerial system and part of the energy passes off into the ether as electro-magnetic waves. However, the oscillations in the _aerial_ system do not immediately die away after the oscillations in the closed circuit cease during the interim until the next condenser discharge, but continue to surge and react upon the dosed circuit to sufficient extent to induce therein currents which surge back and forth long after the current from the condenser discharge has died away.

We might call the oscillations due to the condenser discharge _primary oscillations_ and those induced in the aerial thereby _secondary oscillations_. Those which are then set up in the closed circuit by the reaction of the _secondary_ currents are _tertiary_. This third train of oscillations persist after the secondary currents have died away, and induce another set of oscillations in the aerial which send out a second set of electromagnetic waves differing in length from the first.

The oscillations which take place after the initial surge in the closed and open circuits are naturally somewhat weak. By using an oscillation helix in which the primary and secondary are separated from each other it is possible to eliminate the third and fourth trains of oscillations and all others having a tendency to follow, by placing the circuits apart so that the weak oscillations are not strong enough* to react across the intervening space. The immediate oscillations set up by the condenser discharge are strong enough to act across the space and set up powerful oscillations in the aerial.

A hot wire ammeter placed in the aerial circuit of a transmitter employing an oscillation transformer will not indicate as much current as if placed in the same position in a circuit using an ordinary helix; but in spite of the fact, a transmitter using an oscillation helix will send farther because the energy is concentrated in waves of one length.

The construction of one type of oscillation helix has already been outlined on page 92. The form shown in Fig. 152 has no special advantages over the other but is preferred by many experimenters.

It is of the "pancake" type, so-called because of the flat form of the windings which are made in the shape of a spiral of brass ribbon set in a slotted frame.

The dimensions of the helix are clearly apparent from the drawing. The primary is composed of seven turns of brass ribbon 1/2 inch wide and 1/16 inch thick. The secondary should have from 10 to 15 turns of ribbon 3/8 x 1/16. The coils may be slid back and forth on the brass rod so that the distance between them is variable. Connection is made to the coils by means of suitable clips. A clip similar to that shown on page 92, but made to snap on a flat ribbon instead of a round wire, will serve the purpose.

*QUENCHED SPARK GAP.*

A "quenched" gap is made up of a number of brass or copper disks accurately turned to a true surface and separated by mica or rubber rings about .01 inch thick. The spark discharge takes place in the air-tight space at the center of the disks, inside of the mica rings.

The quenched gap has several advantages over other forms. It is practically noiseless and the nuisance of a crashing discharge may be avoided by its use.

The large surface offered to the spark by the disks cools the spark and quickly stops the oscillations in the closed circuit, and thereby leaves the open circuit and aerial system free to vibrate in its own period and therefore radiates _pure_ waves. By pure wave a wave of one length is meant.

A quenched gap cannot be used on a set of over 1 K.W. power without artificial cooling by an air blast.

Fig. 154 shows an efficient form of quenched gap for use in stations up to 1 K.W. in power.

The disks are shown in detail in Fig. 155. They are cast out of copper and then turned perfectly true and smooth in a lathe. After surfacing, the discharge surface should be heavily silver plated and buffed smooth.

The disks are piled on a marble base with a mica ring between each. They are clamped down by a strong set screw mounted on a heavy brass yoke. Enough pressure should be brought to bear to force the plates tightly together and make them air tight.

The number of disks required is governed by the voltage of the charging condenser. Generally speaking it is one section of .01-inch gap for each thousand volts delivered by the secondary of the transformer. It is very important to secure just the proper number of disks. If properly adjusted, the quenched gap will give one discharge for each alternation of the current and produce a musical tone.

The quenched gap is placed in the same position in the transmitting circuit as any other form of gap.

*ROTARY GAPS.*

Rotary gaps are divided into two general classes, the synchronous gap and the non-synchronous gap.

The former usually consists of one or more stationary electrodes and a rotating member made like a star wheel with projecting spokes. This rotary member is attached directly to the shaft of the alternator or motor generator and arranged so that a spoke always comes opposite a stationary member at the exact moment that the maximum of potential is obtained in the condenser. Such an arrangement permits one discharge for each alternation of the current and produces a pure musical note easily distinguished in the telephone receivers at a distant station.

In the non-synchronous rotary gap the wheel is driven at a high rate of speed without any regard to synchronism with the alternations of the current.

The rotary gap shown in Fig. 157 is of the non-synchronous type.

The rotating member is cast from an alloy of equal parts of zinc and aluminum. It is necessary to first make a wooden pattern from which the casting may be made. The details of the wheel are shown in Fig. 158. The casting must be placed in a lathe chuck and turned true. It is mounted on a hard rubber disk 2 7/8 inches in diameter and 1/4 of an inch thick. The disk serves to insulate the revolving electrodes from the motor shaft. The "rotor" is mounted upon the shaft by means of a small brass bushing which passes through the center of the disk.

The motor must be well built and capable of running at high speed. A "Juno" motor will be found very satisfactory. When running free its speed is about 4500 r.p.m. With the rotor in place the speed is about 3600 r.p.m.

The motor should be mounted on a heavy marble base capable of absorbing any little vibration that the gap may be subject to when running at high speed.

The stationary electrodes are made in the same manner as those for an ordinary gap and consists of two flanged zinc electrodes mounted upon threaded brass rods supported by two hexagonal standards. The axis of the electrodes should be the same height above the base as that of the motor shaft.

The rotor should be carefully balanced so that it is practically free from vibration by boring small holes in the back face so as to make the weight on opposite sides equal.

The motor may be driven by a battery or from the same source that supplies the transformer, in series with two or three suitable lamps. A motor wound to run directly from the 110-volt line or a higher potential must have its fields wound with very fine wire and is apt to give trouble through "burn-outs," due to "kick back." When the motor is operated on batteries or is wound for running in series with a lamp the danger is lessened.

A rotary gap is placed in the transmitting circuit in the same position as any other gap. Its use will result in a wonderful increase in the transmitting range of almost any station, for not only will the amount of energy passing through the aerial be raised, but the clear musical tone given off is more plainly distinguishable at a greater distance in the receiving station than a spark of the ordinary sort.

*"KICK BACK."*

The oscillations taking place in the closed circuit and aerial system of a wireless transmitter continue to surge after the current in the condenser has dropped below a certain value, and react upon the primary winding of the coil or transformer by induction and produce high voltage, high frequency currents termed "kick back," in wireless telegraph parlance.

"Kick back," wherever it exists to an appreciable extent, is liable to damage insulation and cause possible "burn-outs." The "kick-back" preventers illustrated in the accompanying diagrams will be found an efficient method of avoiding this danger.

The first method shows an ordinary pressed telephone condenser of about two microfarads capacity connected directly across the A. C. mains near the transformer terminals, in series with two 6-ampere fuses. The condenser is shunted by a small spark gap made of needle points with a very small space, about .005 of an inch, between them.

The second method is an elaboration of the first and shows two sets of condensers in series with fuses and bridged by spark gaps with a "ground" through a third condenser connected between. This second method is the best and is often used to prevent delicate instruments, such as a voltmeter, from the effects of "kick back."

A proper "kick-back" preventer is part of the Fire Insurance Underwriters requirements for a wireless telegraph station.

Receiving Apparatus.

*THE VARIOMETER.*

A variometer is a tuning device in which two coils of wire are placed in series and connected so that the turns can be made to oppose one another. One coil is movable and by turning it the currents flowing through the adjacent coils oppose each other and decrease the self-induction of the whole and consequently the period of the circuit.

The accompanying illustration shows the constructive details of an efficient form of variometer.

The coils are wound around two cardboard cylinders. One cylinder is 6 inches in diameter and the other 5 inches. Both are 2 inches long. The large cylinder is wound with twenty-five turns of No. 22 B. S. gauge single silk covered wire wound in two sections so as to leave a space 3/8 inch wide in the center. The small cylinder is wound in the same manner with the same size of wire but contains thirty turns so as to make the length of wire in each of the coils practically equal.

The space in the center of each of the coils allows a supporting rod to pass through without interfering with the wire. The shaft is a piece of 5/16 _brass_ rod about 7 1/2 inches long. The upper end is provided with a knob and a pointer. The large coil is mounted on the under side of a wooden cover made to fit a containing case of the proper size to receive the variometer and of a style similar to that ordinarily used to enclose a variable condenser.

The shaft passes through the larger coil, at two points diametrically opposite, but should not fit tightly. It also passes through the smaller coil but is fastened to the latter by means of a cross bar so that when the knob is turned the coil will revolve also. The coils are connected by means of a piece of braided wire or flexible conductor, long enough so as not to interfere with the movement of the inner coil.

The outside terminals of the coils terminate in binding posts mounted on the top of the case. When making a variometer be careful not to employ any iron or steel in its construction, not even iron screws.

The variometer is placed in the receiving circuit by connecting it in series with the aerial before it reaches the tuning coil or loose coupler.

*NEW CRYSTAL DETECTORS.*

*Silicon Detector.*—The silicon detector is always interesting because it was one of the first mineral rectifiers to come into extended use. The photograph shown below illustrates one of the latest forms of the silicon detector.

The large cup supported by the left-hand standard contacts several pieces of fused silicon embedded in fusible alloy. The right-hand standard supports a movable "offset" cup the same as that used on the Perikon type of Detector. A small piece of _arsenic_ is mounted in this cup and may be brought to bear against any portion of any of the silicon crystals.

*Pyron Detector.*—The Pyron detector is not new, but the photograph shows a very simple and efficient form in which a fine wire is brought to bear against a crystal of iron pyrites mounted in a small cup.

*Galena Detector.*—Although _galena_ is named in the list of sensitive minerals on page 132 it has come into such extensive use as a detector since the first edition of this book to be worthy of special attention. Galena detectors are often spoken of as "cat-whisker" detectors because of the long fine wire used to secure a delicate contact with the mineral.

The mineral is usually placed in a cup and held in position by imbedding in fusible alloy or clamped with a set screw. The best surface of the mineral should be selected by testing previous to imbedding it in the cup. Contact is made with the surface of the mineral by means of a piece of No. 30 phosphor bronze wire mounted on the end of a short brass rod fitted with an adjusting screw so that by turning or twisting the surface of the mineral may be "searched" and the tension varied.

Such an arrangement is illustrated in Fig. 164. The base is a hard rubber block 3 3/4 x 1 3/4 x 1/2. The binding posts are of the type commonly used on electrical instruments. One of the posts is pivoted by placing a spring washer under the head of the screw which holds the post to the base. A short piece of brass rod fitted with a hard rubber knob passes through the wire hole in the post. A piece of No. 30 phosphor bronze wire is soldered to the end of the rod. By twisting the post and sliding the rod any portion of the mineral surface may be selected. Twisting the rod varies the tension of the contact.

The galena detector is connected in the receiving circuit in the same manner as other detectors of the mineral type.

*THE AUDION.*

*The Audion*—is finding favor in many amateur wireless stations, because of its almost entire lack of adjustment and of the loud clear signals which it gives even when used for long distance work.

The illustration shows the latest form of audion, the plate and the grid both being on the same side of the filament.

The filament of an audion is usually lighted by means of a six-volt storage battery. A small battery rheostat placed in series with the battery serves to regulate the amount of current flowing through the filament. Only one filament is used at a time, the other being saved as a reserve in case the first burns out.

The higher voltage necessary to operate an audion is supplied by a battery consisting of fifteen flashlight batteries, each flashlight battery being composed of three separate cells. The batteries are connected to an eight-point switch so that throwing the switch on the first point will connect five sets of batteries. The second point places five more in circuit and each additional point one set only. It is also a good plan to connect a four-point switch and three separate cells of battery in series with the eight-point switch so that they may be added to the circuit one at a time and the potential varied more closely than the steps on the eight-point switch permit. The maximum voltage of such a battery is approximately 56 volts.

The diagram in Fig. 166 shows exactly how an audion is connected. The wires _A_ and _B_ are the terminals leading to the tuning coil or loose coupler. It is not necessary that the telephone receivers used with an audion be wound to a high resistance in order to secure good results.

The audion is placed in operation by turning the rheostat until the filament lights brightly. Then adjust the voltage of the high potential battery until the signals are clearest. If the voltage is too high the audion will become filled with a bluish light and the voltage should be immediately reduced. The signals will be loudest when the filament is brilliantly lighted. No more current should be passed through the filament than is necessary to render the signals plain, for if "forced" its life will be limited to only a few hours.

*APPENDIX.*

[PUBLIC No. 264.]

[S. 6412.]

An Act to Regulate Radio Communication.

_Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled._ That a person, company, or corporation within the jurisdiction of the United States shall not use or operate any apparatus for radio communication as a means of commercial intercourse among the several States, or with foreign nations, or upon any vessel of the United States engaged in interstate or foreign commerce, or for the transmission of radiograms or signals the effect of which extends beyond the jurisdiction of the State or Territory in which the same are made, or where interference would be caused thereby with the receipt of messages or signals from beyond the jurisdiction of the said State or Territory, except under and in accordance with a license, revocable for cause, in that behalf granted by the Secretary of Commerce and Labor upon application therefor; but nothing in this Act shall be construed to apply to the transmission and exchange of radiograms or signals between points situated in the same State: _Provided_, That the effect thereof shall not extend beyond the jurisdiction of the said State or interfere with the reception of radiograms or signals from beyond said jurisdiction; and a license shall not be required for the transmission or exchange of radiograms or signals by or on behalf of the Government of the United States, but every Government station on land or sea shall have special call letters designated and published in the list of radio stations of the United States by the Department of Commerce and Labor. Any person, company, or corporation that shall use or operate any apparatus for radio communication in violation of this section, or knowingly aid or abet another person, company, or corporation in so doing, shall be deemed guilty of a misdemeanor, and on conviction thereof shall be punished by a fine not exceeding five hundred dollars, and the apparatus or device so unlawfully used and operated may be adjudged forfeited to the United States.

SEC. 2. That every such license shall be in such form as the Secretary of Commerce and Labor shall determine and shall contain the restrictions, pursuant to this Act, on and subject to which the license is granted; that every such license shall be issued only to citizens of the United States or Porto Rico or to a company incorporated under the laws of some State or Territory or of the United States or Porto Rico, and shall specify the ownership and location of the station in which said apparatus shall be used and other particulars for its identification and to enable its range to be estimated; shall state the purpose of the station, and, in case of a station in actual operation at the date of passage of this Act, shall contain the statement that satisfactory proof has been furnished that it was actually operating on the above-mentioned date; shall state the wave length or the wave lengths authorized for use by the station for the prevention of interference and the hours for which the station is licensed for work; and shall not be construed to authorize the use of any apparatus for radio communication in any other station than that specified. Every such license shall be subject to the regulations contained herein, and such regulations as may be established from time to time by authority of this Act or subsequent Acts and treaties of the United States. Every such license shall provide that the President of the United States in time of war or public peril or disaster may cause the closing of any station for radio communication and the removal therefrom of all radio apparatus, or may authorize the use or control of any such station or apparatus by any department of the Government, upon just compensation to the owners.

SEC. 3. That every such apparatus shall at all times while in use and operation as aforesaid be in charge or under the supervision of a person or persons licensed for that purpose by the Secretary of Commerce and Labor. Every person so licensed who in the operation of any radio apparatus shall fail to observe and obey regulations contained in or made pursuant to this Act or subsequent Acts or treaties of the United States, or any one of them, or who shall fail to enforce obedience thereto by an unlicensed person while serving under his supervision, in addition to the punishments and penalties herein prescribed, may suffer the suspension of the said license for a period to be fixed by the Secretary of Commerce and Labor not exceeding one year. It shall be unlawful to employ any unlicensed person or for any unlicensed person to serve in charge or in supervision of the use and operation of such apparatus, and any person violating this provision shall be guilty of a misdemeanor, and on conviction thereof shall be punished by a fine of not more than one hundred dollars or imprisonment for not more than two months, or both, in the discretion of the court, for each and every such offense: _Provided_, That in case of emergency the Secretary of Commerce and Labor may authorize a collector of customs to issue a temporary permit, in lieu of a license, to the operator on a vessel subject to the radio ship Act of June twenty-fourth, nineteen hundred and ten.

SEC. 4. That for the purpose of preventing or minimizing interference with communication between stations in which such apparatus is operated, to facilitate radio communication, and to further the prompt receipt of distress signals, said private and commercial stations shall be subject to the regulations of this section. These regulations shall be enforced by the Secretary of Commerce and Labor through the collectors of customs and other officers of the Government as other regulations herein provided for.

The Secretary of Commerce and Labor may, in his discretion, waive the provisions of any or all of these regulations when no interference of the character above mentioned can ensue.

The Secretary of Commerce and Labor may grant special temporary licenses to stations actually engaged in conducting experiments for the development of the science of radio communication, or the apparatus pertaining thereto, to carry on special tests, using any amount of power or any wave lengths, at such hours and under such conditions as will insure the least interference with the sending or receipt of commercial or Government radiograms, of distress signals and radiograms, or with the work of other stations.

In these regulations the naval and military stations shall be understood to be stations on land.

REGULATIONS.

NORMAL WAVE LENGTH.

First. Every station shall be required to designate certain definite wave length as the normal sending and receiving wave length of the station. This wave length shall not exceed six hundred meters or it shall exceed one thousand six hundred meters. Every coastal station open to general public service shall at all times be ready to receive messages of such wave lengths as are required by the Berlin convention. Every ship station, except as hereinafter provided, and every coast station open to general public service shall be prepared to use two sending wave lengths, one of three hundred meters and one of six hundred meters, as required by the international convention in force: _Provided_, That the Secretary of Commerce and Labor may, in his discretion, change the limit of wave length reservation made by regulations first and second to accord with any international agreement to which the United States is a party.

OTHER WAVE LENGTHS.

Second. In addition to the normal sending wave length all stations, except as provided hereinafter in these regulations, may use other sending wave lengths: _Provided_, That they do not exceed six hundred meters or that they do exceed one thousand six hundred meters: _Provided further_, That the character of the waves emitted conforms to the requirements of regulations third and fourth following.

USE OF A "PURE WAVE"

Third. At all stations if the sending apparatus, to be referred to hereinafter as the "transmitter," is of such a character that the energy is radiated in two or more wave lengths, more or less sharply defined, as indicated by a sensitive wave meter, the energy in no one of the lesser waves shall exceed ten per centum of that in the greatest.

USE OF A "SHARP WAVE."

Fourth. At all stations the logarithmic decrement per complete oscillation in the wave trains emitted by the transmitter shall not exceed two-tenths, except when sending distress signals or signals and messages relating thereto.

USE OF "STANDARD DISTRESS WAVE."

Fifth. Every station on shipboard shall be prepared to send distress calls on the normal wave length designated by the international convention in force, except on vessels of small tonnage unable to have plants insuring that wave length.

SIGNAL OF DISTRESS.

Sixth. The distress call used shall be the international signal of distress: dot dot dot, dash dash dash, dot dot dot.

USE OF "BROAD INTERFERING WAVE" FOR DISTRESS SIGNALS.

Seventh. When sending distress signals, the transmitter of a station on shipboard may be tuned in such a manner as to create a maximum of interference with a maximum of radiation.

DISTANCE REQUIREMENT FOR DISTRESS SIGNALS.

Eighth. Every station on shipboard, wherever practicable, shall be prepared to send distress signals of the character specified in regulations fifth and sixth with sufficient power to enable them to be received by day over sea a distance of one hundred nautical miles by a shipboard station equipped with apparatus for both sending and receiving equal in all essential particulars to that of the station first mentioned.

FOR DISTRESS SIGNALS.

Ninth. All stations are required to give absolute priority to signals and radiograms relating to ships in distress; to cease all sending on hearing a distress signal; and, except when engaged in answering or aiding the ship in distress, to refrain from sending until all signals and radiograms relating thereto are completed.

REDUCED POWER FOR SHIPS NEAR A GOVERNMENT STATION.

Tenth. No station on shipboard, when within fifteen nautical miles of a naval or military station, shall use a transformer input exceeding one kilowatt, nor, when within five nautical miles of such a station, a transformer input exceeding one-half kilowatt, except for sending signals of distress, or signals or radiograms relating thereto.

INTERCOMMUNICATION.

Eleventh. Each shore station open to general public service between the cost and vessels at sea shall be bound to exchange radiograms with any similar shore station and with any ship station without distinction of the radio systems adopted by such stations, respectively, and each station on shipboard shall be bound to exchange radiograms with any other station on shipboard without distinction of the radio systems adopted by each station respectively.

It shall be the duty of each such shore station, during the hours it is in operation, to listen in at intervals of not less than fifteen minutes and for a period not less than two minutes, with the receiver tuned to receive messages of three hundred meter wave lengths.

DIVISION OF TIME.

Twelfth. At important seaports and at all other places where naval or military and private or commercial shore stations operate in such close proximity that interference with the work of naval and military stations can not be avoided by the enforcement of the regulations contained in the foregoing regulations concerning wave lengths and character of signals emitted, such private or commercial shore stations as do interfere with the reception of signals by the naval and military stations concerned shall not use their transmitters during the first fifteen minutes of each hour, local standard time. The Secretary of Commerce and Labor may, on the recommendation of the department concerned, designate the station or stations which may be required to observe this division of time.

GOVERNMENT STATIONS TO OBSERVE DIVISION OF TIME.

Thirteenth. The naval or military stations for which the above mentioned division of time may be established shall transmit signals or radiograms only during the first fifteen minutes of each hour, local standard time, except in case of signals or radiograms relating to vessels in distress, as hereinbefore provided.

USE OF UNNECESSARY POWER.

Fourteenth. In all circumstances, except in case of signals or radiograms relating to vessels in distress, all stations shall use the minimum amount of energy necessary to carry out any communication desired.

GENERAL RESTRICTIONS ON PRIVATE STATIONS.

Fifteenth. No private or commercial station not engaged in the transaction of bona fide commercial business by radio communication or in experimentation in connection with the development and manufacture of radio apparatus for commercial purposes shall use a transmitting wave length exceeding two hundred meters, or a transformer input exceeding one kilowatt, except by special authority of the Secretary of Commerce and Labor contained in the license of the station: _Provided_, That the owner or operator of a station of the character mentioned in this regulation shall not be liable for a violation of the requirements of the third or fourth regulations to the penalties of one hundred dollars or twenty-five dollars, respectively, provided in this section unless the person maintaining or operating such station shall have been notified in writing that the said transmitter has been found, upon tests conducted by the Government, to be so adjusted as to violate the said third and fourth regulations, and opportunity has been given to said owner or operator to adjust said transmitter in conformity with said regulations.

SPECIAL RESTRICTIONS IN THE VICINITIES OF GOVERNMENT STATIONS.

Sixteenth. No station of the character mentioned in regulation fifteenth situated within five nautical miles of a naval or military station shall use a transmitting wave length exceeding two hundred meters or a transformer input exceeding one-half kilowatt.

SHIP STATIONS TO COMMUNICATE WITH NEAREST SHORE STATIONS.

Seventeenth. In general, the shipboard stations shall transmit their radiograms to the nearest shore station. A sender on board a vessel shall, however, have the right to designate the shore station through which he desires to have his radiograms transmitted. If this can not be done, the wishes of the sender are to be complied with only if the transmission can be effected without interfering with the service of other stations.

LIMITATIONS FOR FUTURE INSTALLATIONS IN VICINITIES OF GOVERNMENT STATIONS.

Eighteenth. No station on shore not in actual operation at the date of the passage of this Act shall be licensed for the transaction of commercial business by radio communication within fifteen nautical miles of the following naval or military stations, to wit: Arlington, Virginia; Key West, Florida; San Juan, Porto Rico; North Head and Tatoosh Island, Washington; San Diego, California; and those established or which may be established in Alaska and in the Canal Zone; and the head of the department having control of such Government stations shall, so far as is consistent with the transaction of governmental business, arrange for the transmission and receipt of commercial radiograms under the provisions of the Berlin convention of nineteen hundred and six and future international conventions or treaties to which the United States may be a party, at each of the stations above referred to, and shall fix the rates therefor, subject to control of such rates by Congress. At such stations and wherever and whenever shore stations open for general public business between the coast and vessels at sea under the provisions of the Berlin convention of nineteen hundred and six and future international conventions and treaties to which the United States may be a party shall not be so established as to insure a constant service day and night without interruption, and in all localities wherever or whenever such service shall not be maintained by a commercial shore station within one hundred nautical miles of a naval radio station, the Secretary of the Navy shall, so far as is consistent with the transaction of governmental business, open naval radio stations to the general public business described above, and shall fix rates for such service, subject to control of such rates by Congress. The receipts from such radiograms shall be covered into the Treasury as miscellaneous receipts.

SECRECY OF MESSAGES.

Nineteenth. No person or persons engaged in or having knowledge of the operation of any station or stations shall divulge or publish the contents of any messages transmitted or received by such station, except to the person or persons to whom the same may be directed, or their authorized agent, or to another station employed to forward such message to its destination, unless legally required so to do by the court of competent jurisdiction or other competent authority. Any person guilty of divulging or publishing any message, except as herein provided, shall, on conviction thereof, be punishable by a fine of not more than two hundred and fifty dollars or imprisonment for a period of not exceeding three months, or both fine and imprisonment, in the discretion of the court.

PENALTIES.

For violation of any of these regulations, subject to which a license under sections one and two of this Act may be issued, the owner of the apparatus shall be liable to a penalty of one hundred dollars, which may be reduced or remitted by the Secretary of Commerce and Labor, and for repeated violations of any of such regulations, the license may be revoked.

For violation of any of these regulations, except as provided in regulation nineteenth, subject to which a license under section three of this Act may be issued, the operator shall be subject to a penalty of twenty-five dollars, which may be reduced or remitted by the Secretary of Commerce and Labor, and for repeated violations of any such regulations, the license shall be suspended or revoked.

SEC. 5. That every license granted under the provisions of this Act for the operation or use of apparatus for radio communication shall prescribe that the operator thereof shall not wilfully or maliciously interfere with any other radio communication. Such interference shall be deemed a misdemeanor, and upon conviction thereof the owner or operator, or both, shall be punishable by a fine of not to exceed five hundred dollars or imprisonment for not to exceed one year, or both.

SEC. 6. That the expression "radio communication" as used in this Act means any system of electrical communication by telegraphy or telephony without the aid of any wire connecting the points from and at which the radiograms, signals, or other communications are sent or received.

SEC. 7. That a person, company, or corporation within the jurisdiction of the United States shall not knowingly utter or transmit, or cause to be uttered or transmitted, any false or fraudulent distress signal or call or false or fraudulent signal, call, or other radiogram of any kind. The penalty for so uttering or transmitting a false or fraudulent distress signal or call shall be a fine of not more than two thousand five hundred dollars or imprisonment for not more than five years, or both, in the discretion of the court, for each and every such offense, and the penalty for so uttering or transmitting, or causing to be uttered or transmitted, any other false or fraudulent signal, call, or other radiogram shall be a fine of not more than one thousand dollars or imprisonment for not more than two years, or both, in the discretion of the court, for each and every such offense.

SEC. 8. That a person, company, or corporation shall not use or operate any apparatus for radio communication on a foreign ship in territorial waters of the United States otherwise than in accordance with the provisions of sections four and seven of this Act and so much of section five as imposes a penalty for interference. Save as aforesaid, nothing in this Act shall apply to apparatus for radio communication on any foreign ship.

SEC. 9. That the trial of any offense under this Act shall be in the district in which it is committed, or if the offense is committed upon the high seas or out of the jurisdiction of any particular State or district the trial shall be in the district where the offender may be found or into which he shall be first brought.

SEC. 10. That this Act shall not apply to the Phillippine Islands.

SEC. 11. That this Act shall take effect and be in force on and after four months from its passage.

Approved, August 13, 1912.

LIST OF WORKS

ON

ELECTRICAL SCIENCE

PUBLISHED AND FOR SALE BY

D. VAN NOSTRAND COMPANY,

*25 Park Place, New York.*

*ABBOTT, A. V. The Electrical Transmission of Energy.* A Manual for the Design of Electrical Circuits. _Fifth Edition, enlarged and rewritten._ With many Diagrams, Engravings and Folding Plates. 8vo., cloth, 675 pp Net, $5.00

*ARNOLD, E. Armature Windings of Direct-Current Dynamos.* Extension and Application of a general Winding Rule. Translated from the original German by Francis B. DeCress. Illustrated. 8vo. cloth, 124 pp $2.00

*ASHE, S. W. Electricity Experimentally and Practically Applied.* _Second Edition._ 422 illustrations. 12mo., cloth, 375 pp. Net, $2.00

*ASHE, S. W., and KEILEY, J. D. Electric Railways Theoretically and Practically Treated.* Illustrated. 12mo., cloth.

*Vol. I. Rolling Stock.* _Second Edition._ 285 pp Net, $2.50

*Vol. II. Substations and Distributing Systems.* 296 pp Net, $2. 50

*ATKINSON, A. A. Electrical and Magnetic Calculations.* For the use of Electrical Engineers and others interested in the Theory and Application of Electricity and Magnetism. _Fourth Edition_, revised Illustrated. 12mo, cloth, 310 pp Net, $1.50

*ATKINSON, PHILIP. The Elements of Dynamic Electricity and Magnetism.* _Fourth Edition._ Illustrated. 12mo., cloth, 405 pp. $2.00

- *Elements of Electric Lighting,* including Electric Generation, Measurement, Storage, and Distribution. _Tenth Edition_, fully revised and new matter added. Illustrated. 12mo., cloth, 280 pp $1.50 - *Power Transmitted by Electricity and Applied by the Electric Motor,* including Electric Railway Construction. Illustrated. _Fourth Edition_, fully revised and new matter added. 12mo., cloth, 241 pp. $2.00

*AUSTIN, E. Single-Phase Electric Railways.* 346 illustrations 8 x 11, cloth, 308 pp Net, $5.00

*AYRTON, HERTHA. The Electric Arc.* Illustrated. 8vo., cloth, 479 pp Net, $5.00

*BAKER, J. T. The Telegraphic Transmission of Photographs.* 63 illustrations. 12mo., cloth, 155 pp Net, $1.25

*BARHAM, G. B. Development of the Incandescent Electric Lamp.* 25 illustrations, 2 plates, 5 x 8 cloth. 206 pp $2.00

*BEDELL, FREDERICK. Direct and Alternating Current Manual.* With directions for testing and a discussion of the theory of electrical apparatus. _Second Edition, greatly enlarged_. Assisted by C. A. Pierce. Illustrated. 6 x 9, cloth, 373 pp Net, $2.00

*BLAINE, ROBERT G. The Calculus and Its Applications.* A practical treatise for beginners especially engineering students. 79 illustrations. 12mo., cloth, 330 pp Net, $1.50

*BONNEY, G. E. The Electro-Plater’s Hand Book.* A Manual for Amateurs and Young Students of Electro-Metallurgy. _Fifth Edition, enlarged._ 61 Illustrations. 12mo., cloth, 208 pp $1.20

*BOTTONE, S. R. Magnetos For Automobilists; How Made and How Used* A handbook of practical instruction on the manufacture and adaptation of the magneto to the needs of the motorist. _Second Edition, enlarged_. 52 illustrations. 12mo., cloth, 118 pp Net, $1.00

*BROADFOOT, S. K. Motors, Secondary Batteries and Accessory Apparatus.* 16 illustrations. 16mo., cloth. 100pp. (Installation Manuals Series) Net, 0.75

*BROUGHTON, H. H. Electric Canes.* Their design, construction and application. 600 illustrations and plates. 120 tables, 6 x 9, cloth, 848 pp Net, $9.00

*CHILD, C. D. Electric Arcs.* Experiments upon arcs between different electrodes in various environments and their explanation. 58 illustrations. 5 x 7, cloth, 203 pp Net, $2.00

*COLLIS, A. G. High and Low Tension Switchgear Design.* 94 illustrations and folding plates, 6 x 9, cloth, 233 pp Net, $3.50

- *Switchgear and The Control of Electric Circuits.* 47 illustrations. 4 1/2 x 6 1/2, cloth, 85 pp. (Installation Manuals Series) Net, 0.50

*COMSTOCK, D. F., and TROLAND, L. T. The Nature of Matter and Electricity.* An outline of modern views. Illustrated. 5 x 7, cloth, 200 pp Net, $2.00

*COOPER, W. R. Primary Batteries: their Theory, Construction, and Use* _New Edition in Press_

*CRAIG, J. W., and WOODWARD, W. P. Questions and Answers About Electrical Apparatus.* Third edition revised and enlarged. Illustrated. 4 x 6 Leather, 256 pp Net, $1.50

*CRAMP, W. Continuous Current Machine Design.* 137 illustration. 8vo., cloth, 240 pp Net, $2.50

*CREED Y, F. Single-Phase Commutator Motors.* 98 illustrations, 6 x 9, cloth, 120 pp Net, $2.00

*CROCKER, F. B. Electric Lighting.* A Practical Exposition of the Art for the use of Electricians, Students, and others interested in the Installation or Operation of Electric Lighting Plants.

- *Vol. I. The Generating Plant*. _Seventh Edition, entirely revised_. Illustrated. 8vo., cloth, 482 pp $3.00 - *Vol. II. Distributing System and Lamps.* _Sixth Edition_. Illustrated 8vo., cloth, 505 pp.

*CROCKER, F. B., and ARENDT, M. Electric Motors: Their Action, Control, and Application.* _Second Edition, Revised and Enlarged_. 169 illustrations. 6 1/4 x 9 1/4, cloth, 315 pp Net, $2.50

*CROCKER, F. B., and WHEELER, S. S. The Management of Electrical Machinery.* Being a _thoroughly revised and rewritten edition_ of the authors’ "Practical Management of Dynamos and Motors." _Eighth Edition._ Illustrated. 16mo., cloth, 232 pp Net, $1.00

*CUSHING, H. C., Jr. Standard Wiring for Electric Light and Power* Illustrated. 16mo., leather, 156 pp $1.00

*CUSHING, H. C., Jr. and HARRISON, N. Central Station Management.* 5 1/2 x 7 1/4 cloth, 417 pp Net, $2.00

*DAVIES, F. H. Electric Power and Traction.* Illustrated. 8vo., cloth 293 pp. (Van Nostrand’s Westminster Series.) Net, $2.00

- *Foundations and Machinery Fixing.* 52 illustrations. 16mo., cloth, 146 pp. (Installations Manuals Series) Net, $1.00

*DEL MAR, W. A. Electric Power Conductors.* _Second edition revised._ 69 illustrations. 5 1/2 x 8, cloth, 330 pp Net, $2.00

*DEVEY, R. G. Mill and Factory Wiring.* 126 illustrations. 16mo., cloth, 209 pp. (Installation Manuals Series) Net, $1.00

*DINGER, Lieut. H. C. Handbook for the Care and Operation of Naval Machinery.* _Second Edition._ 124 Illustrations. 16mo., cloth, 302 pp Net, $2.00

*DUNCAN, W. G. and PENMAN, D. Electrical Equipment of Collieries.* 157 illustrations, 6 1/2 x 8 3/4, cloth, 329 pp Net, $4.00

*DWIGHT, H. B. Transmission Line Formulas for Electrical Engineers and Engineering Students.* 27 illustrations. 2 folding plates, 12mo, cloth, 143 pp Net, $2.00

*DYNAMIC ELECTRICITY:* Its Modern Use and Measurement, chiefly in its application to Electric Lighting and Telegraphy, including: 1. Some Points in Electric Lighting, by Dr. John Hopkinson. 2. On the Treatment of Electricity for Commercial Purposes, by J. N. Shoolbred. 3. Electric-Light Arithmetic, by R. E. Day, M.E. _Fourth Edition._ Illustrated. 16mo., boards, 166 pp. (No. 71 Van Nostrand’s Science Series.) 50 cents

*ECK, J. Light, Radiation and Illumination.* Translated from the German of Paul Hogner. 59 illustrations. 5 1/2 x 8, cloth, 100 pp. Net, $2.50

*ECCLES, W. H. Wireless Telegraphy and Telephony.* Illustrated. 5 x 8 1/2 half leather, 418 pp Net, $4.50

*EDDY, L. C. Laboratory Manual of Alternating Currents.* 21 illustrations, 5 1/2 x 8, cloth, 26 pp Net, 50 cents

*EDLER, R. Switches and Switchgear.* Translated by Ph. Laubach. 335 illustrations. 6 1/2 x 9, cloth, 412 pp Net, $4.00

*EDGCUMBE, K. Industrial Electrical Measuring Instruments.* Illustrated. 8 vo., cloth, 227 pp.

*ENGINEERING AS A CAREER.* By Prominent Engineers. Edited by C. E. Drayer and F. H. Newell. 5 1/4 x 7 1/2, 226 pp. Paper 75 cents, cloth $1.00

*EWING, J. A. Magnetic Induction in Iron and other Metals.* _Third Edition, revised_. Illustrated. 8vo., cloth, 393 pp Net, $4.00

*FISHER, H. K. C., and DARBY, W. C. Students’ Guide to Submarine Cable Testing.* _Fourth Edition, enlarged._ Illustrated. 8vo., cloth, 252 pp Net, $3.50

*FLEMING, J. A., Prof. The Alternate-Current Transformer in Theory and Practice.*

*Vol. I.: The Induction of Electric Currents.* _Fifth Issue._ Illustrated. 5vo., cloth, 641 pp: Net, $5.00

*Vol. II.: The Utilization of Induced Currents.* _Third Issue._ Illustrated. 8vo., cloth, 587 pp Net, $5.00

- *Propagation of Electric Currents in Telephone and Telegraph Conductors.* Illustrated. 6 1/2 x 9 1/2, cloth, 323 pp Net, $3.00 - *Handbook for the Electrical Laboratory and Testing Room.* Two Volumes. Illustrated. 8vo., cloth, 1160 pp. Each vol Net, $5.00

*FOSTER, H. A. With the Collaboration of Eminent Specialists. Electrical Engineers’ Pocket Book.* A handbook of useful data for Electricians and Electrical Engineers. With innumerable Tables, Diagrams, and Figures. The most complete book of its kind ever published, treating of the latest and best Practice in Electrical Engineering. _Seventh Edition, completely revised and enlarged._ Fully Illustrated. Pocket Size. Leather. Thumb Indexed. 1636 pp $5.00

- *Engineering Valuation of Public Utilities and Factories.* 50 blank forms. 6 x 9, cloth, 361 pp Net, $3.00 - *Electrical Cost Data, Estimates and Working Tables.* _In Press_

*FOWLE, F. F. The Protection of Railroads from Overhead Transmission Line Crossings.* 35 illustrations. 12mo., cloth, 76 pp Net, $1.50.

*FREUDEMACHER, P. W. Electrical Mining Installations.* 36 illustrations. 16mo., cloth, 192 pp. (Installation Manuals Series) Net, $1.00

*FRITH, J. Alternating Current Design.* 27 illustrations. 6 x 9, cloth, 131 pp Net, $2.00

*GARRARD, C. C. Electric Switch and Controlling Gear.* 423 illustrations, 5 3/4 x 8 3/4, cloth, 656 pp Net, $6.00

*GANT, L. W. Elements of Electric Traction for Motormen and Others.* Illustrated with Diagrams. 8vo., cloth, 217 pp Net, $2.00

*GEAR, H. B. and WILLIAMS, P. F. Electric Central Station Distribution Systems. Their Design and Construction.* _Second Edition, revised and enlarged_. 187 illustrations. 5 1/2 x 7 1/2, cloth, 455 pp Net, 3.50

*GERHARDI, C. H. W. Electricity Meters; their Construction and Management.* A practical manual for engineers and students. Illustrated. 8vo., cloth, 337 pp Net, $4.00

*GOLDSMITH, RUDOLF. The Alternating Current Commutator Motor. The Leakage of Induction Motors.* In one volume. 247 illustrations. 5 1/4 x 8 3/4, cloth Net, $3.00

*GORE, GEORGE. The Art of Electrolytic Separation of Metals (Theoretical and Practical).* Illustrated. 8vo., cloth, 295 pp Net $3.50

*GROTH, L. A. Welding and Cutting Metals by Aid of Gases or Electricity.* 124 illustrations. 8 vo., cloth, 280 pp. (Van Nostrand’s Westminister Series) Net, $2.00

*HALLER, G. F. and CUNNINGHAM, E. T. The Tesla High Frequency Coil; its construction and uses.* 12mo., cloth, 56 illustrations, 130 pp Net, $1.25

*HASKINS, C. H. The Galvanometer and its Uses. A Manual for Electricians and Students.* _Fifth Edition, revised_. Illustrated. 16mo., morocco, 75 pp $1.50

*HAUSMANN, E. Telegraph Engineering. A Manual for Practicing Telegraph, Engineers and Engineering Students.* 192 Illustrations. cloth, 416 pp Net, $3.00

*HAY, ALFRED. An Introductory Course of Continuous-Current Engineering.* Illustrated. 8vo., cloth, 327 pp Net, $2.50

*HAYES, H. V. Public Utilities, Their Cost New and Depreciation.* 5 3/4 x 8 1/2, cloth, 275 pp Net, $2.00

- *Public Utilities; Their Fair Present Value and Return.* 5 1/2 x 8 1/2, cloth, 200 pp Net, $2.00

*HEATHER, H. J. Electrical Engineering for Mechanical and Mining Engineers.* 183 illustrations. 5 x 8, cloth, 344 pp Net, $3.50

*HEAVISIDE, O. Electromagnetic Theory. Two Volumes with Many Diagrams.* 8vo., cloth, 1006 pp. Each Vol Net, $5.00

*Vol. III.* 529 pp Net, $7.50

*HOBART, H. M. Heavy Electrical Engineering.* Illustrated. 8vo., cloth, 338 pp Net, $4.50

- *Design of Static Transformers.* 101 illustrations. 6 x 9, cloth, 189 pp Net, $2.00 - *Electricity. A text-book designed in particular for engineering students.* 115 illustrations. 43 tables. 8vo.. cloth, 266 pp, Net, $2.00 - *Electric Trains.* 88 illustrations. 8vo., cloth, 220 pp Net, $2.50 - *Electric Propulsion of Ships.* 44 illustrations. 8vo., cloth, 167 pp. Net, $2.00

*HOBBS, W. R. P. The Arithmetic of Electrical Measurements.* With numerous examples, fully worked. _Sixteenth Edition, revised and edited with six additional chapters by A. R. Palmer._ 12mo. cloth, 126 pp 50 cents.

*HOUSTOUN, R. A. Studies in Light Production.* 22 illustrations. 5 3/4 x 8 3/4, cloth, 120 pp Net, $2.00

*HUTCHINSON, R. W., Jr. Long-Distance Electric Power Transmission:* Being a Treatise on the Hydro-Electric Generation of Energy; Its Transformation, Transmission, and Distribution. _Second Edition._ Illustrated. 12mo., cloth, 350 pp Net, $3.00

- *and THOMAS, W. D. Electricity in Mining.* Being a theoretical and practical treatise on the construction, operation and maintenance of electrical mining machinery. 12mo., cloth _In Press_

*INCANDESCENT ELECTRIC LIGHTING.* A Practical Description of the Edison System, by H. Latimer. To which is added: The Design and Operation of Incandescent Stations, by C. J. Field; A Description of the Edison Electrolyte Meter, by A. E. Kennelly; and a Paper on the Maximum Efficiency of Incandescent Lamps, by T. W. Howell. _Fifth Edition._ Illustrated. 16mo., cloth, 140 pp. (No. 57 Van Nostrand’s Science Series.) 50 cents

*INDUCTION COILS: How Made and How Used.* _Eleventh Edition_. Illustrated. 16mo., cloth, 123 pp. (No. 53 Van Nostrand’s Science Series.) 50 cents

*JEHL, FRANCIS. The Manufacture of Carbons for Electric Lighting and other purposes.* Illustrated with numerous Diagrams, Tables, and Folding Plates. 8vo., cloth, 232 pp Net, $4.00

*JOHNSON, J. H. Arc Lamps and Accessory Apparatus.* 20 illustrations. 16mo., cloth, 135 pp. (Installation Manuals Series) Net, 75 cents.

*JOHNSON, T. M. Ship Wiring and Fitting.* 47 illustrations. 16mo., cloth, 92 pp. (Installation Manuals Series) Net, 75 cents.

*JONES, HARRY C. The Electrical Nature of Matter and Radioactivity.* _Third Edition, revised._ 5 1/2 x 8 1/2, cloth, 218 pp Net, $2.00

*KAPP, GISBERT. Alternate-Current Machinery.* Illustrated. 16mo., cloth, 190 pp. (No. 96 Van Nostrand’s Science Series) 50 cents

*KAPPER, F. Overhead Transmission Lines and Distributing Circuits.* 297 illustrations. 2 plates, 7 1/4 x 10, cloth, 310 pp Net, $4.00

*KENNEDY, R. Electrical Installations of Electric Light, Power, and Traction Machinery.* Illustrated. 8vo., cloth, 5 vols. The set $15.00. Each $3.50

*KENNELLY, A. E. Theoretical Elements of Electro-Dynamic Machinery.* Vol. I. Illustrated. 8vo., cloth, 90 pp $1.50

*KERSHAW, J. B. C. The Electric Furnace in Iron and Steel Production.* Illustrated. 8vo., cloth, 74 pp Net, $1.50

- *Electrometallurgy.* Illustrated. 8vo., cloth, 303 pp. (Van Nostrand’s Westminster Series.) Net, $2.00

*KINZBRUNNER, C. Continuous-Current Armatures; their Winding and Construction.* 79 Illustrations. 8vo., cloth, 80 pp Net, $1.50

- *Alternate-Current Windings; their Theory and Construction.* 89 Illustrations. 8vo., cloth, 80 pp Net, $1.50 - *The Testing of Alternating Current Machines in Laboratories and Test Rooms.* A practical work for students and engineers. Vol I. General Tests; Transformers, Alternators. 141 illustrations. 5 1/2 x 8 3/4, cloth, 164 pp Net, $2.00

*KLINGENBERG, G. Large Electric Power Stations.* Their design and construction, with examples of existing stations. 180 illustrations, 7 plates, 7 x 10, cloth, 260 pp Net, $5.00

*KOESTER, F. Hydroelectric Developments and Engineering.* A practical and theoretical treatise on the development, design, construction, equipment and operation of hydroelectric transmission plants. _Second Edition_. 500 illustrations. 4to., cloth, 475 pp. Net, $5.00

- *Steam-Electric Power Plants.* A practical treatise on the design of central light and power stations and their economical construction and operation. Second Edition. Fully Illustrated. 4to., cloth 455 pp Net, $5.00

*LANCASTER, M. Electric Cooking, Heating and Cleaning.* Edited by W. E. Lancaster, American Edition by S. L. Coles, 305 illustrations, 6 x 8 1/2, cloth 340 pp Net, $1.00

*LARNER, E. T. The Principles of Alternating Currents for Students of Electrical Engineering.* Illustrated with Diagrams. 12mo., cloth, 144 pp Net, $1.25

*LEMSTROM, S. Electricity in Agriculture and Horticulture.* Illustrated. 8vo., cloth Net, $1.50

*LIVERMORE, V. P., and WILLIAMS, J. How to Become a Competent Motorman:* Being a practical treatise on the proper method of operating a street-railway motor-car; also giving details how to overcome certain defects. Second Edition. Illustrated. 16mo., cloth, 247 pp Net, $1.00

*LIVINGSTONE, R. Mechanical Design and Construction of Generators.* 122 illustrations. 5 1/2 x 8 3/4, cloth, 228 pp Net, $3.50

- *Mechanical Design and Construction of Commutators.* 62 illustrations, 5 1/2 x 8 3/4, cloth, 93 pp Net, $2.25

*LOCKWOOD, T. D. Electricity, Magnetism, and Electro-Telegraphy.* A Practical Guide and Handbook of General Information for Electrical Students, Operators, and Inspectors. _Fourth Edition._ Illustrated. 8vo., cloth, 374 pp $2.50

*LODGE, OLIVER J. Signalling Across Space Without Wires:* Being a description of the work of Hertz and his successors. _Third Edition_ Illustrated. 8vo., cloth Net, $2.00

*LORING, A. E. A Handbook of the Electro-Magnetic Telegraph* _Fourth Edition, revised._ Illustrated. 16mo., cloth, 116 pp. (No. 39 Van Nostrand’s Science Series.) 50 cents

*LUCKTESH, M. Color and Its Application.* 126 illustrations, 4 color plates. 6 x 9, cloth, 350 pp $3.00

- *Light and Shade and Their Applications.* 135 illustrations, 10 tables, 6 1/4 x 9 1/4, cloth, 278 pp Net, $2.50

*MALCOLM, W. H. Theory of the Submarine Telegraph Cable.* _In Press_

*MANSFIELD, A. N. Electromagnets: Their Design and Construction.* _Second Edition._ Illustrated. 16mo M cloth, 155 pp. (No. 64 Van Nostrand’s Science Series.) 50 cents

- *Manufacture of Electric Light Carbons.* Illustrated. 5 1/2 x 8, cloth. Net, $1.00

*MASSIE, W. W., and UNDERBILL, C. R. Wireless Telegraphy and Telephony Popularly Explained.* With a chapter by Nikola Tesla. Illustrated. 12mo., cloth, 82 pp Net, $1.00

*MAURICE, W. Electrical Blasting Apparatus and Explosives, with special reference to colliery practice.* Illustrated. 8vo., cloth. 167 pp Net, 3.50

- *The Shot Firer’s Guide.* A practical manual on blasting and the prevention of blasting accidents. 78 illustrations. 8vo., cloth. 212 pp Net, $1.50

*MIESSNER, B. F. Radiodynamics.* The wireless control of torpedoes and other mechanisms. 112 illustrations, 5 1/2 x 8 1/4, cloth, 211 pp. Net, $2.00

*MONCKTON, C. C. F. Radio Telegraphy.* 173 Illustrations. 8vo cloth, 272 pp. (Van Nostrand’s Westminster Series.) Net, $2.00

*MONTGOMERY, J. W. Electric Wiring Specifications* 4 x 6 1/2, cloth, 107 pp Net, $1.50

*MORECROFT, J. H. and HEHRE, F. W. A Short Course in Testing of Electrical Machinery.* _Third Edition._ Illustrated. 8vo., cloth, 160 pp Net, 1.50

*MORGAN, ALFRED P. Wireless Telegraph Construction for Amateurs.* _Third Edition._ 167 illustrations. 5 1/2 x 7 1/2, cloth, 236 pp Net, $1.50

*NERZ, F. Searchlights, Their Theory, Construction and Application.* Translated by C. Rodgers. 47 illustrations. 6 x 8,, cloth, 145 pp. Net, $3.00

*NIPHER, FRANCIS E. Theory of Magnetic Measurements.* With an Appendix on the Method of Least Squares. Illustrated. 12mo., cloth, 94 pp $1.00

*OHM, G. S. The Galvanic Circuit Investigated Mathematically.* Berlin, 1827. Translated by William Francis. With Preface and Notes by Thos. D. Lockwood. _Second Edition._ Illustrated. 16mo., cloth, 269 pp. (No. 102 Van Nostrand’s Science Series.) 50 cents

*OLSSON, ANDREW. Motor Control as used in Connection with Turret Turning and Gun Elevating.* (The Ward Leonard System.) 13 illustrations. 12mo., paper, 27 pp. (U. S. Navy Electrical Series No. 1.) Net, .50

*OUDIN, MAURICE A. Standard Polyphase Apparatus and Systems.* _Sixth Edition, revised._ Illustrated with many Photo-reproductions, Diagrams, and Tables. 8vo., cloth, 369 pp Net, $3.00

*PALAZ, A. Treatise on Industrial Photometry.* Specially applied to Electric Lighting. Translated from the French by G. W. Patterson, Jr., and M. R. Patterson. _Second Edition._ Fully Illustrated. 8vo., cloth, 324 pp $4.00

*PARR, G. D. A. Electrical Engineering Measuring Instruments for Commercial and Laboratory Purposes.* With 370 Diagrams and Engravings. 8vo., cloth, 328 pp Net, $3.50

*PARSHALL, H. P., and HOBART, H. M. Armature Windings of Electric Machines.* _Third Edition._ With 140 full-page Plates, 65 Tables, and 165 pages of descriptive letter-press. 4vo., cloth, 300 pp. $7.50

- *Electric Railway Engineering.* With 437 Figures and Diagrams and many Tables. 4to., cloth, 475 pp Net, $7.50 - *Electric Machine Design.* Being a revised and enlarged edition of "Electric Generators." 648 Illustrations. 4vo., half morocco, 601 pp Net, $12.50

*PATCHELL W. H. Application of Electric Power to Mines and heavy Industries.* 91 illustrations 6 1/2 x 9 1/4, cloth, 203 pp Net, 4.00

*PATTERSON, G. W. L. Wiring Calculations for Light and Power Installations.* 139 illustrations, 5 1/4 x 7 1/4. cloth, 203 pp Net, $2.00

- *Electric Mine Signalling and Installations.* Illustrated. 5 1/4 x 7 1/8, 110 pp Net, $1.50

*PERRINE, F. A. C. Conductors for Electrical Distribution: Their Manufacture and Materials the Calculation of Circuits, Pole Line Construction, Underground Working, and other Uses.* _Second Edition._ Illustrated. 8vo., cloth, 287 pp Net, $3.50

*POPE, F. L. Modern Practice of the Electric Telegraph.* A Handbook for Electricians and Operators. _Seventeenth Edition_. Illustrated. 8vo., cloth, 234 pp $1.50

*RAPHAEL, F. C. Localization of Faults in Electric Light Mains.* _Third Edition In Press_

*RASCH, E. Electric Arc Phenomena.* Translated by K. Tornberg. 52 illustrations. 5 x 7, cloth, 187pp Net, $2.00

*RAYMOND, E. B. Alternating-Current Engineering, Practically Treated.* _Third Edition, revised_. With many Figures and Diagrams. 8vo., cloth, 244 pp Net, $2.50

*REDFERN, T. B. and SAVIN, J. Bells, Indicators, Telephones, Fire and Burglar Alarms.* 85 illustrations. 4 1/2 x 6 3/4, cloth, 123 pp. (Installation Manuals Series) .50

*RICHARDSON, S. S. Magnetism and Electricity and the Principles of Electrical Measurement.* Illustrated. 12mo., cloth, 596 pp. Net, $2.00

*ROBERTS, J. Laboratory Work in Electrical Engineering—Preliminary Grade.* A series of laboratory experiments for first and second-year students in electrical engineering. Illustrated with many Diagrams. 8vo., cloth, 218 pp Net, $2.00

*ROLLINS, W. Notes on X-Light.* Printed on deckle edge Japan paper 400 pp. of text, 152 full-page plates. 8vo., cloth Net, $5.00

*RUHMER, ERNST. Wireless Telephony in Theory and Practice.* Translated from the German by James Erskine-Murray. Illustrated. 5vo., cloth, 224 pp Net, $3.50

*RUSSELL, A. The Theory of Electric Cables and Networks.* 71 Illustrations. 8vo., cloth, 275 pp Net, $3.00

*SAYERS, H. M. Brakes for Tramway Cars.* 6 x 9, cloth, 76 pp. Net, 1.25

*SEVER, G. F. Electrical Engineering Experiments and Tests on Direct-Current Machinery.* _Second Edition, enlarged_. With Diagrams and Figures. 8vo., pamphlet, 75 pp Net, $1.00

*SEVER, G. F., and TOWNSEND, F. Laboratory and Factory Tests in Electrical Engineering.* _Second Edition, revised and enlarged._ Illustrated. 8vo., cloth, 269 pp Net, $2.50

*SEWALL, C. H. Wireless Telegraphy. With Diagrams and Figures.* _Second Edition, corrected_. Illustrated . 8vo., cloth, 229 pp Net, $2.00

- *Lessons in Telegraphy.* Illustrated. 12mo., cloth, 104 pp Net, $1.00

*SEWELL, T The Construction of Dynamos (Alternating and Direct Current).* A Text-book for students, engineering contractors, and electricians-in-charge. Illustrated. 8vo., cloth, 316 pp $3.00

*SHELDON, S., and HAUSMANN, E Dynamo-Electric Machinery: Its Construction, Design, and Operation.*

*Vol.1.: Direct-Current Machines.* _Ninth Edition, completely re-written._ Illustrated. 12mo., cloth, 281 pp Net, $2.50

*Vol. II.: Alternating-Current Machines:* _Tenth Edition, rewritten._ cloth, 353 pp Net, $2.50

- *Electric Traction and Transmission Engineering* 127 illustration. 12mo., cloth, 317 pp Net, $2.50

*SLOANE, T. O’CONOR. Elementary Electrical Calculations.* A Manual of Simple Engineering Mathematics, covering the whole field of Direct Current Calculations, the basis of Alternating Current Mathematics, Networks, and typical cases of Circuits, with Appendices on special subjects. 8vo., cloth. Illustrated. 304 pp Net, $2.00

*SMITH, C. F. Practical Alternating Currents, and Alternating Current Testing.* _Third Edition._ 236 illustrations. 5 3/4 x 8 3/4, cloth, 476 pp. Net $2.60

*SMITH, C. F. Practical Testing of Dynamos and Motors.* _Third Edition_, 108 illustrations. 5 1/4 x 8 3/4, cloth, 322 pp Net, $2.00

*SNELL, ALBION T. Electric Motive Power.* The Transmission and Distribution of Electric Power by Continuous and Alternating Currents. With a Section on the Applications of Electricity to Mining Work. _Second Edition_. Illustrated. 8vo., cloth, 411 pp Net, $4.00

*SODDY, F. Radio-Activity; an Elementary Treatise from the Standpoint of the Disintegration Theory.* Fully Illustrated. 8vo., cloth, 214 pp Net, $3.00

*SOLOMON, MAURICE. Electric Lamps.* Illustrated. 8vo., cloth. (Van Nostrand’s Westminster Series.) Net, $2.00

*SWINBURNE, JAS., and WORDINGHAM, C. H. The Measurement of Electric Currents. Electrical Measuring Instruments. Meters for Electrical Energy.* Edited, with Preface, by T. Commerford Martin. Folding Plate and Numerous Illustrations. 16mo., cloth, 241 pp. (No. 109 Van Nostrand’s Science Series.) 50 cents

*SWOOPE, C. WALTON. Lessons in Practical Electricity: Principle Experiments, and Arithmetical Problems. An Elementary Textbook.* With numerous Tables, Formulae, and two large Instruction Plates. _Fifteenth Edition, revised_. Illustrated. 5vo., cloth, 462 pp Net, $2.00

*THIESS, J. B. and JOY, G. A. Toll Telephone Practice.* 273 illustrations. 8vo., cloth, 433 pp Net, $3.50

*THOM, C., and JONES, W. H. Telegraphic Connections, embracing recent methods in Quadruplex Telegraphy.* 20 Colored Plates. 8vo., cloth, 59 pp $1.50

*THOMPSON, S. P., Prof. Dynamo-Electric Machinery.* With an Introduction and Notes by Frank L. Pope and H. R. Butler. Illustrated 16vo., cloth, 214 pp. (No. 66 Van Nostrand’s Science Series.) 50 cents

- *Recent Progress in Dynamo-Electric Machines.* Being a Supplement to "Dynamo-Electric Machinery." Illustrated. 16mo., cloth, 113 pp. (No. 75 Van Nostrand’s Science Series.) 50 cents

*TOWNSEND, FITZHUGH. Alternating Current Engineering.* Illustrated. 8vo, paper, 32 pp Net, 75 cents

*UNDERBILL, C. R. Solenoids, Electromagnets and Electromagnetic Windings.* _Second Edition_. 218 Illustrations. 12mo., cloth, 345 pp Net, $2.00

*URQUHART, J. W. Electroplating.* _Fifth Edition_. Illustrated. 12mo., cloth, 230 pp $2.00

- *Electrotyping.* Illustrated. 12mo., cloth, 228 pp $2.00

*VOSMAER, A. Ozone.* Its Manufacture and Uses. 76 illustrations. 6 x 9, cloth, 210 pp Net, $2.50

*WADE, E. J. Secondary Batteries: Their Theory, Construction, and Use.* _Second Edition, corrected_ 265 illustrations. 8vo., cloth, 501 pp. Net, $4.00

*WADSWORTH, C. Primary Battery Ignition.* A simple practical pocket guide on the construction, operation, maintenance, and testing of primary batteries for automobile, motorboat, and stationary engine ignition service. 26 illustrations. 5 x 7, cloth, 79 pp Net, 0.50

*WALKER, FREDERICK. Practical Dynamo Building for Amateurs. How to Wind for any Output.* _Third Edition_. Illustrated. 16mo., cloth, 104 pp. (No. 68 Van Nostrand’s Science Series.) 50 cents.

- *Electricity in Mining.* Illustrated. 8vo., cloth, 385 pp $.50

*WATT, ALEXANDER. Electroplating and Refining of Metals* _New Edition_, rewritten by Arnold Philip. Illustrated 8vo., cloth, 704 pp Net, $4.50

- *Electro-metallurgy* _Fifteenth Edition_. Illustrated 12mo., cloth, 225 pp $1.00

*WEBB, H. L. A Practical Guide to the Testing of Insulated Wires and Cables* _Sixth Edition_. Illustrated. 12mo., cloth., 118pp $1.00

*WILKINSON, H. D. Submarine Cable-Laying, Repairing, and Testing.* _Second Edition, completely revised_. 313 illustrations. 8vo., cloth, 580 pp Net, $6.00

*WILSON, J. F. Essentials of Electrical Engineering.* 300 illustrations. 6 x 9, cloth, 355 pp Net, $2.50

*WRIGHT, J. Testing, Fault Localization and General Hints for Linemen.* 19 Illustrations. 16mo., cloth, 88 pp. (Installation Serious Manuals.) Net, 50 cents.

*YOUNG, J. ELTON. Electrical Testing for Telegraph Engineers.* Illustrated. 8vo., cloth, 264 pp Net, $4.00

*ZEIDLER, J., and LUSTGARTEN, J. Electric Arc Lamps: Their Principles, Construction and Working.* 160 Illustrations. 8vo., cloth, 188 pp Net, $2.00

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