WIWH) Hi EW1& • bEiWI9 I 'mil ■■>»■■» ■ « i'uj i mip i imm i n l M i Mmiww »ii n iii ■■■ ! ■ » eammttammBtmamm laiiHunMHaaoiME ' Digitized by the Internet Archive in 2011 with funding from Boston Library Consortium Member Libraries http://www.archive.org/details/abcofvacuumtubesOOIewi THE A B C OF VACUUM TUBES IN RADIO RECEPTION AN ELEMENTARY AND PRACTICAL BOOK ON THE- THEORY AND OPERATION OF VACUUM TUBES AS DETECTORS AND AMPLIFIERS. EXPLAINS NON-MATHEMATICALLY THE FUNDA- MENTAL PRINCIPLES UPON WHICH ALL VACUUM TUBE CIRCUITS ARE BASED Includes PRACTICAL CIRCUITS AND PRACTICAL QUESTIONS AND ANSWERS. IT IS WRITTEN ESPECIALLY FOR THE BEGINNER. ALL ELECTRICAL AND RADIO TERMS ARE FULLY EXPLAINED E. H. LEWIS u Assoc. I.R.E., Radio Instructor, East Side Y. M. C. A., New York City. FULLY ILLUSTRATED New York THE NORMAN W. HENLEY PUBLISHING CO. 2 West 45th Street 1922 Copyrighted, 1922 BY The Norman W. Henley Publishing Co. 427^7 PRINTED IN U. S. A. PREFACE The inauguration of radio-telephone broadcasting has quickly aroused an enormous general interest in radio reception of speech and music. The possibilities of this new method of broadcasting information of general interest and entertainment can hardly be estimated. The method is revolutionary and has been aptly compared to the invention of the printing press in this respect. Vacuum tubes make possible the reception of radio-telephone speech and music and radio-telegraph signals with a degree of satisfaction not approached by prior devices. The vacuum tube appears to the layman as a complicated form of incandescent electric lamp which operates in a very mysterious manner. In writing this little book the author has endeavored to overcome this impression and to clearly set forth the elementary principles of theory and operation. It is assumed that the reader has no knowledge of radio and very little, if any, of electricity. Mathematics has been especially avoided in the treatment of the subject and no technical terms are used without their meaning being made clear. The functioning of the "lamps" is fascinating to a great many people and the author hopes that the desire for elementary information regarding it will be fulfilled in the text. No attempt has been made to set forth all the possible circuit arrangements but those shown may serve as suggestions to experimenters who desire to evolve their own circuits. The practical questions and answers, it is hoped, may be of value to those who are contemplating the installation of receiving PREFACE equipment or who are getting unsatisfactory results because of insufficient information. Suggestions regarding improvement of the material pre- sented and the manner of presentation will be gratefully received from readers. April, 1922. The Author. CONTENTS PAGE CHAPTER I Introductory Electric current — Electrical pressure or Electromotive force — Resist- ance — Direct current — Alternating current — Frequency — Inductance . — Capacitance — Resonance — Oscillations — The Reception of sig- nals — Wave length — Tuning the receiving antenna — The Antenna as a complete circuit 15 CHAPTER II The Vacuum Tube as a Rectifier and Relay Without Moving Parts Tube construction — The Edison Effect — Electron emission from a heated filament — Dependence of plate current upon plate potential — Dependence of plate current upon filament current — Effect of grid potential upon plate current — Relay action — Rectification ... 38 CHAPTER III The Vacuum Tube Detector The telephone receiver — Simple detection — Detection with grid con- denser — Effect of gas in a detector tube — Heterodyne action or the production of beats 59 CHAPTER IV The Vacuum Tube Amplifier General characteristics — Audio frequency amplification — Radio fre- quency amplification — Radio frequency regenerative amplification — Autodyne production of beats 76 CHAPTER V Practical Circuits and Their Operation Methods of coupling — The variometer — Inter electrode tube capaci- tance — Wave length, Frequency and Resonance — Circuits and expla- nations of their arrangement and operation ...... 90 CONTENTS CHAPTER VI Voice Distortion PAGE Amplifier transformers — Normal grid potential — Too great regenera- tion — Telephone receiver . . . in CHAPTER VII Practical Questions and Answers Practical Questions and Answers . ......... 116 ~ List of Symbols ~ Battery — 1|| | |h- Direct Current Dynamo --- Bh M ^B ca Alternating \ ^-. re- current f Xy~ or _JQ) Generator ) ^— ^ v — Fixed Capacitance " T" (Condenser ) Variable Capacitance l b* f l^br: Condenser) /\\ 4 /vW Inductance _..^^ 7 ffiff5ff\„ (Air Core Coil) VUVVVU Variable Inductance _y"^W$x_. ^ r _i^^p_ (Air Core Coil) y^ a Variometer ( Variable Inductance) — Fixed Co up ling of Co Us — \JHlfifiil/~~ (Fixed Inductive Coupling) ^TT\Kf^\^ Variable Coupling of Coils t , "IS Transtormer— gj Iron Core Inductance ( or Reactance Coil ) -List of Symbols- Antenna Ground Wire Connections V or V —^ or No Connections of Wires Fixed Res is tctnce Variable Resistance Vacuum Tube — Telephone Receivers Voltmeter - •■ Ammeter Galvanometer — vww— GALVO. Crystal Detector *$ 2J CHAPTER I INTRODUCTORY Electric current — Electrical pressure or Electromotive force — Re- sistance — Direct current — Alternating current — Frequency — Inductance — Capacitance — Resonance — Oscillations — The reception of signals — Wave length — Tuning the receiving antenna — The antenna as a complete circuit. Before taking up the subject of vacuum tubes a brief out- line of the most common electrical and radio phenomena together with the explanation of common electrical terms will be given. It is understood that for some this may be a review of knowledge previously gained. For others it may, however, serve to fix some very vague understandings and some familiarity with these fundamental facts is necessary in order to comprehend that which follows. Electrical Current It is very commonly known that a battery and a dynamo furnish what is called a "current of electricity" and that the electrical current will not flow unless a path is provided for it. The path is called the "electrical circuit" or simply the "circuit." For example, if it is desired to ring a door-bell it is necessary to connect the bell to a battery by means of insulated wires and if the path, or circuit, is broken at any point the bell will not ring. A push button may be used to keep the circuit broken until the button is pressed, whereupon an electric current flows through the circuit and the bell rings. IS i6 A B C OF VACUUM TUBES Fig. I represents such a circuit which may be closed at will by pushing the button. Since no electricity flows when the circuit is open we may assume that it flows in all parts of the circuit when it is closed. Thus, if the current flows from the battery at "A" it must return to the battery at "B." The terminal of the battery from which the current flows is called \Push Button Contacts Positive Terminal-' B & Bell - Negative Terminal Battery Fig. i — Simple electrical path or circuit. the "positive terminal and the other the "negative" terminal. To illustrate the flow of current, a closed circuit of pipe may be used. A pump is located at "A" in Fig. 2 and the Fig. 2 — Water analogy of simple electrical circuit. pipe is considered to be full of water. When the pump is operated the water will be forced to flow, let us say, in the direction of the arrow. It flows from the pump through the pipe and returns to the pump and the same amount of water which leaves the pump in one second of time will return to INTRODUCTORY 17 it in the same length of time. In other words, there is a continuous flow of water until the pump stops. This corre- sponds to the electrical circuit and it may very easily be proven that the current is no stronger in one part than it is in any other part of the circuit. We may measure the current or rate of flow of the water in gallons per second. That is, if there is one gallon flowing in one second past any given point in the pipe the rate of flow is one gallon per second. The current or rate of flow of electricity also may be measured and the unit is called the "ampere." The rate of flow of electric current is sometimes referred to as its "strength" and if the current strength is one ampere its rate of flow is one ampere, a certain fixed quantity of electricity per second. It must not be assumed that electricity is actually a fluid like water. It is not. No one knows just what electricity is but its effects may be noted and its "flow" may be compared in many respects to that of water, i Electrical Pressure or Electro-Motive Force Electrical pressure is referred to as "electro-motive force" since in order to create a current of electricity it is necessary to provide some force to make it flow. In the case of the pipe full of water the pump must exert a force or pressure upon the water to push it through the pipe. In the case of the elec- trical circuit in Fig. 1 the battery furnishes the electrical pres- sure. Neither water nor electricity can flow unless a pressure is provided. If we wish either the water or the electric cur- rent to flow faster (at an increased rate) the pressure applied to it must be increased. Water pressure may be measured in pounds per square inch 18 A B C OF VACUUM TUBES but electrical pressure or electro-motive force is measured in volts. Sometimes electrical pressure is referred to as 'Volt- age." E. M. F. is a convenient abbreviation to use for the long expression "electro-motive force" and it will be used hereafter in this text. Resistance When water flows through a pipe there is always a certain amount of friction between the water and the pipe. This hin- ders the flow of the water, that is, reduces the rate at which the water current flows. And the reduction in rate of flow depends directly upon the increase of the friction. Likewise there is friction present in the path of the electric current which acts as a "resistance" to the current flow. If the pres- sure or E. M. F. is kept constant the rate of current flow (current strength) increases as the resistance is decreased and vice versa. If, however, the resistance is kept constant it is natural to expect the current (rate of flow) of the electricity to increase with an increase of E. M. F. and vice versa. The current thus depends upon both the resistance and the E. M. F. The unit of electrical resistance is called the "ohm" and if the resistance of a circuit is one ohm, one ampere of cur- rent will flow if the E. M. F. is one volt. This relation between current, E. M. F. and resistance is called "Ohm's Law" and is the first fundamental law of electrical circuits. Direct Current If the E. M. F. applied in a circuit is steady and only acts to force the current to flow in one direction through a circuit the resulting current is steady and is called a "direct current." INTRODUCTORY 19 If the E. M. F. rises and falls but only acts in one direction the resulting current rises and falls and is called a "pulsating direct current" or a "pulsating current." Batteries produce a steady direct current in one direction through a circuit. Many dynamos, however, produce a pulsating E. M. F. which causes a pulsating current to flow (in one direction only) through a circuit. The periodical increases and decreases of E. M. F. and current may be made very small, however, so that they are hardly perceptible. Alternating Current Imagine that instead of a battery we have a dynamic gen- erator of electrical pressure in a circuit and that the E. M. F. produced acts in first one direction, then the other, and that ^ Second of Time Current Max. in Heg. Direction Fig. 3 — One cycle of current changes and reversals. per second. Frequency 60 cycles while acting in each direction it increases to a maximum value and decreases to zero. The current created will also change its direction of flow and increase and decrease in strength periodically, as shown in Fig. 3. Such a current could be 20 A B C OF VACUUM TUBES said to "alternate" in its direction of flow and is aptly called an "alternating current." These alternations or rever- sals of current flow, with their accompanying increases and decreases in rate of flow, take place very rapidly and at per- fectly regular intervals. In this figure the current values or "rates of flow" are shown as increasing and decreasing in one direction above the horizontal line and increasing and decreasing in the opposite direction below that line. In order to distinguish the directions of flow from each other we may call one the "positive" direction and the other the "negative" direction, so that all current values along the ver- tical line and above the horizontal line are in the positive direc- tion and all those along the vertical but below the horizontal are in the negative direction. During the period of time rep- resented by the horizontal line the current has increased to a maximum value and decreased to zero in the positive direc- tion then has reversed its direction and increased to a maximum and decreased to zero again. In increasing and decreasing, the current has passed through all values from zero to maxi- mum in each direction. It has thus gone through one "cycle" of current changes and directions of flow. As long as the E. M. F. acts, the current will continue to go through these changes in a perfectly regular manner periodically. Frequency In the ordinary house lighting circuit, if it has alternating current, the periodical reversals of current flow usually take place at the rate of 60 cycles per second. It may be said then that the "frequency" of the alternating current is 60 cycles per second. In radio work extremely high frequencies, varying approxi- INTRODUCTORY 21 mately between 15,000 and 2,000,000 cycles per second, are also used. Such very high frequencies are called "radio fre- quencies." It is not within the scope of this little book tc discuss the various methods of producing alternating currents of high frequency but it may be said that all radio transmitters do produce them and that they are very essential. Inductance Inductance, or, more properly, "self inductance," is a prop- erty possessed to a greater or lesser extent by every electrical circuit. It has no effect upon a direct current but does have an effect, which will be discusssed, upon an alternating cur- k- I Cycle of Current J Fig. 4 — Effect of inductance in an alternating current circuit. rent. As shown in Fig. 4 it has the effect of causing the current to rise to its maximum value after the maximum value of E. M. F. The current is said to "lag" behind the E. M. F. "Reactance" is the name given to an "effective" resistance to alternating current which depends directly upon the value of the inductance and upon the frequency of the alternations. 22 A B C OF VACUUM TUBES In an alternating current circuit, if we for the moment disre- gard the actual resistance, the average value of current decreases as the reactance increases providing that the E. M. F. has a constant average value. That is, the reactance has the effect of a resistance although it is not true "ohmic' 'or actual resist- ance. If the circuit contains reactance and ohmic resistance, the average current value will decrease with an increase in either or both providing again that the average E. M. F. is constant. A straight wire possesses inductance to some extent and the inductance of a wire increases with its length. Given a certain length of wire, its inductance and therefore its react- ance may be very greatly increased by coiling it. Also, if more turns are added to the coil or if an iron core is placed inside of it, its inductance is increased and its reactance as well. To distinguish this type of reactance from a type considered below we may call it "inductive reactance." To sum up, then, inductive reactance depends directly upon the inductance and frequency of current. The average value of alternating cur- rent in a circuit varies inversely with the reactance. * Capacitance Capacitance, or, as it is sometimes called, "capacity," has exactly the opposite effect of inductance upon an alternating current. Capacitance has the effect of causing the current to rise to its maximum value before the E. M. F. The current in this case is said to "lead" the E. M. F., as is graphically shown in Fig. 5. * The reciprocal of the product of capacitance and fre- * If the product were 2, the reciprocal would be l / 2 . The reciprocal of 3 is 1-3, of 2x 100 it is ■ 1 — and so forth. 2 X 100 INTRODUCTORY 23 quency determines the value of a reactance which in this case may be called a "capacitive reactance." The capacitive react- ance, however, does not have the effect of a resistance to the alternating current but exactly the opposite. The average / Cycle of Current p\ I I ^ I Cycle ofE.M.F. >j Fig- 5 — Effect of capacitance in an alternating current circuit. current value depends directly upon the capacitive reactance in a circuit, providing the average value of E. M. F. is kept constant. The average value of the alternating current then increases with an increase in either the average E. M. F. or the capacitive reactance and decreases with an increase of actual resistance. Capacitive reactance decreases with an in- crease of either capacitance or frequency, and vice versa. A straight wire has some capacitance which increases with the length of the wire. Coiling the wire will also increase its capacitance. But since inductance is the predominant prop- erty the capacitance of a wire or coil is very small in com- parison. If two metallic plates are assembled with a sheet of glass between them there is produced what is known as a ' 'condenser." This arrangement would have a very appreci- able capacitance. To increase the capacitance of this con- 24 A B C OF VACUUM TUBES denser we could (i) increase the area of the glass and the metallic plates; (2) decrease the thickness of the glass (the distance separating the metallic plates) ; (3) use a substance between the plates which has a higher "dielectric constant.' ' The material between the plates, whatever it may be, is called the "dielectric" and although it may not be an absolute insu- lator it does have a very high resistance, usually, to the passage of a current. Air is assumed to have a "dielectric constant" of unity (or one) and if a condenser with the same dimensions has a dielectric which gives five times the capacity of the air condenser, the "dielectric constant" of the other material is five. Some dielectric constants in the order of their increase are: Air — 1, paraffine — 2; hard rubber — 2.5; glass — 6 to 8; mica — 8. It would be very convenient at times to have a variable capacitance whose value could be adjusted at will. If the maxi- .'Terminafs--. * si Stationary Plates-* <- Movable Plates Fig. 6 — Scheme of a variable condenser. (If the movable plates are made stationary it is a "fixed" condenser.) mum value is not necessarily very large, an air dielectric may be used. A number of movable plates could be arranged so that they interleave with a number of stationary plates without touching them. All the stationary plates are connected together and to a terminal and the movable plates are connected together and to a second terminal. There will be an increase in the INTRODUCTORY 25 maximum capacitance obtainable if more plates are used be- cause this will increase the total plate area, the dielectric being the air between the stationary and movable plates. Fig. 6 shows how the plates are interleaved and Fig. 7 illustrates a variable air condenser with and without its case. The question may be asked, "How does an electric current flow through a condenser if the dielectric is a good insulator Connecting „ , Posts Scale in Degrees^ Man die to Rotate Movable Plates Shaft upon which Movable Plates are Mounted 'Insulating Buttons .. ,, n, j ) or Washers between Movable Plates- Plates Fig. 7 — Typical variable condenser with air dielectric. and prevents the passage of current?" A direct current will not flow through a condenser and neither will an alternating current. But the alternating current will appear to flow through because in all parts of the circuit on either side of the dielectric it rises and falls in rate of flow back and forth between the dielectric and the source of E. M. F. To make the matter more clear, suppose an analogy is considered. In Fig. 8 a pipe full of water is represented with an elastic parti- tion at "A" and a pump at "B." The pump is so arranged that the to-and-fro motion of the piston exerts a pressure periodically in one direction then the other and causes the 26 A B C OF VACUUM TUBES water, therefore, to flow in each direction periodically. The water does not flow past the elastic partition at any time. But, the elasticity of the partition allows it to stretch and during the time the current is forced in the direction of the full line arrow, it stretches and exerts a back pressure upon the water exactly equal to the pressure of the pump at every instant. When the pump pushes the water in the opposite direction the partition stretches in the opposite direction and again exerts a back pressure equal at every instant to the pump pressure. There is thus a surge of water back and forth through the pipe, causing the partition to stretch in first one direction then the other, within the limit of its elasticity. And, then, as far as the pipe is concerned, there is an alternating current of water in it in spite of the partition. The dielectric of a condenser is the "partition" and it must have electrical elas- Elash'c Partition- Piston Rod-' B Pump Fig. 8 — Water analogy of alternating current in a circuit containing a condenser. ticity, otherwise it might be ruptured in the same manner that the partition in the pipe would be, if the pump pressure became too great. It is thus readily seen that while an alternating current does not actually flow through the dielectric, the cur- rent does alternate in the circuit in spite of the dielectric. INTRODUCTORY 2J Resonance Suppose two tuning forks are tuned to the same musical pitch and placed a foot or so apart. If one is struck a light blow it vibrates and a sound is heard which is the musical pitch dependant upon the rate of vibration of the fork. The fork is setting up waves in the air which reach the ear and are translated by the brain into a musical tone which is recog- nized. What is perhaps more interesting, however, is that the second tuning fork also vibrates in sympathy with the first. If the first fork is grasped in the hand to stop its vibra- tion, the second will still vibrate for a short time and emit a musical tone exactly of the same pitch as the first one. It is evident that the second fork is vibrating at the same rate as the first before it was grasped. It is said to be "in tune" or "in resonance" with the first. Suppose, however, that the first tuning fork is adjusted so that, when struck, it vibrates at a different rate. This time the second one will not vibrate in sympathy as it would if it also had been adjusted to vibrate at the same rate. The two forks are then not in tune with each other and the second \% "out of resonance" with the first. In the first case the second fork was forced to vibrate at the same mechanical frequency (of vibration) as the first fork, because it was in resonance. In the second case there was no resonance, so the second fork was unaffected. An electrical circuit in which an alternating current flows does not vibrate mechanically, but it may be thought of as vibrating electrically. Also, one electrical circuit may be ad- justed so that it is "in resonance" with another and so that an alternating current flowing in one will produce an alter- nating current in the other of the same frequency. In this 28 A B C OF VACUUM TUBES case of "electrical resonance," the second circuit is caused to 'Vibrate electrically" in sympathy with the first. Oscillations Alternating electrical currents of extremely high frequency are said to be alternating at "radio frequencies," as has been noted. And such high frequency alternating currents are -f Zero Current' <- /Cycle *l -Amplitude Jn£o5{tlve_ I Direction ' of Flow •Amplitude in Negative Direction of Flow Fig. 9 — Continuous oscillations. called "Radio frequency alternating currents." Instead of using this long name a shorter one has been selected for prac- tical use, and it is said that such alternating currents are "oscillations." A definition of oscillations may then be, "radio frequency alternating current." The maximum value of current strength attained in each direction of current flow during each cycle is called the "ampli- tude." If successive amplitudes are of equal values as long as the current flows, the oscillations are said to be "continuous oscillations." An alternating E. M. F. of constant amplitude is, of course, necessary to the production of continuous oscil- INTRODUCTORY 29 lations. Fig. 9 may assist the reader to understand this term. An ordinary, low frequency, alternating current also has con- stant amplitudes. If an E. M. F. has constantly decreasing amplitude it will produce a current of constantly decreasing amplitude. Also, if the amplitudes of the E. M. F. decrease rather rapidly, the current will cease to flow after a short period of time because of the absence of E. M. F. to force it to flow. If, then, the successive amplitudes of oscillations decrease, the •t ^■5 ^t Cycle ->\ t± 1 Train of Oscillations — ->j k — I Train of Oscillations — >| .-Amplitudes in Positive Direction \ Zero Current '' Is % \ / ''^Amplitudes in Negative Direction or Flow Fig. 10 — Damped oscillations. oscillations may be said to be "damped," and there is produced what are called "damped oscillations." Sometimes continuous oscillations are referred to as "undamped oscillations," because their successive amplitudes are not damped. When damped oscillations finally cease they are said to be "damped out." Fig. 10 will assist in understanding this matter. Two series, or groups, of damped oscillations are shown, and each series may be referred to as a "train" of damped oscillations. If an electrical shock were given to a circuit containing inductance and capacitance, that is, if an electrical pressure 3 o A B C OF VACUUM TUBES were suddenly applied and immediately withdrawn, the circuit would vibrate electrically in the same manner as the struck tuning fork vibrated mechanically. An alternating current would be produced in the circuit, providing its resistance were not too great, but the successive amplitudes would decrease and the oscillations would die out just as the vibrations of the tuning fork die out a short while after the fork is struck. In the second circuit, just as with the second fork, even though there is resonance the vibrations die out after a short time. If, however, the first tuning fork were tapped very lightly at the end of each swing it would continue to vibrate as long as the tapping took place at the proper times and in the proper amounts to maintain these vibrations (or swings). The regu- lar periodical tapping may be compared to a regular periodical E. M. F. applied in an electrical circuit. If the E. M. F. is applied at the proper times and always in the same amounts, the oscillations will not decrease in amplitude but will be "con- tinuous." Now, in the case of the tuning forks, if the vibra- tions of the first one are continuous (due to continuously applied taps), the vibrations of the second one will continue and be of constant amplitude. Likewise, in a second electrical circuit, if the oscillations in the first are continuous those in the second will also be continuous. Continuous oscillations in a second circuit are then the result of a continuously applied E. M. F. in that circuit due, in turn, to a continuously applied E. M. F. (and therefore oscillations of continuous amplitude) in the first circuit. The action of producing oscillations in a second circuit by creating oscillations in a primary circuit is called "induction," and we may say that when oscillations are produced in a sec- ondary circuit they are "induced" therein. INTRODUCTORY 31 The Reception of Signals It should now be quite clear that if oscillations are produced in a suitable circuit at a transmitting station oscillations will be produced by induction in a suitable circuit at a receiving station, when the two circuits are in resonance with each other. Each of the circuits is called an "antenna," or sometimes, an "aerial," since each is frequently erected so that it extends some distance from the earth up into the air. When vibrations are induced in a tuning fork by another, the air between them is set in motion and it is this air which transmits the motion from one fork to the other. That is, the first fork sets the air into vibration and the vibrating air sets the second fork into vibration. Another illustration would be the dropping of a stone into a quiet pond of water. Water waves radiate from the point where the stone strikes the water until they reach a cork located a distance away. The cork is set into motion and bobs up and down, or oscillates. But the cork does not move further away from or closer to the point where the oscillations were created in the water. This proves that the water itself does not travel from one place to another but that the oscillating motion is transmitted or radi- ated from the point where the disturbance occurs. In the case of either the air or the water it is the oscillatory or vibratory motion which is transmitted. This throws some light upon electrical induction, But in the case of oscillations produced in a secondary electrical circuit neither air nor Water is necessary to transmit the mo- tion. In fact, electrical oscillations in a circuit have no effect upon either air or water. There must be some medium, how- ever, which is capable of being set into vibration by the elec- trical oscillations and will, in turn, create electrical oscillations 32 A B C OF VACUUM TUBES in a distant circuit. This medium is called the "ether," and is one which pervades all space. It is present in the entire universe where water and air may be entirely absent. It is, in fact, the ether which is set into vibration by the oscillations in a transmitting antenna. These vibrations spread out in circles just like the ripples in the water after a stone is dropped and when they reach a receiving antenna, create elec- trical oscillations in that circuit. The whole purpose of "radio" is to create ether vibrations and to translate them at a distant point. Now, assume that continuous oscillations or recurrent trains of damped oscillations are produced in a transmitting antenna and either continuous or recurrent trains of damped oscilla- tions are induced in the receiving antenna. We still lack, a device to make the received oscillations perceptible to one of our senses. But in a following chapter means for accom- plishing this necessary result are considered. Wave Length The ether vibrations or oscillations have the same frequency as the electrical oscillations which create them. Moreover, this oscillatory motion of the ether is projected through it with the speed of light, light being only ether vibration at considerably different frequencies. This rate of speed is 300,000,000 meters (approximately 186,000 miles) per sec- ond of time. Almost too rapid a rate to conceive — in fact, ether oscillations caused by electrical oscillations travel over seven times around the earth in one second. The ripples created in a pond of water by the dropping of a stone travel about 10 to 100 centimeters per second, a centi- meter being roughly equivalent to one-hundredth of a yard. INTRODUCTORY 33 The ripples are, of course, small water waves, and if we know their rate of travel and their frequency of production, we can easily calculate the length of one wave. For example, one wave is produced each second and travels a distance of one yard in that length of time. What is the length of the wave? It is, of course, the rate of travel (one yard in one second) divided by the frequency of wave production (one cycle per second or one wave per second), and equals, in this case, one yard. Likewise, if an ether wave travels 300,000,000 meters per second and the frequency of its oscillation is 300,000, its length must be 1,000 meters. That is, the wave length (length of one wave) is the result of dividing the velocity (distance traveled per second) by the frequency (number of waves per second). There are, of course, the same number of waves per second as cycles of oscillation. In speaking of these ether vibrations it is customary to think of their wave length rather than their frequency. If a transmitting station is said to "radiate" a "wave length" of 200 meters, what is meant is that the ether in the neighborhood of the transmitting antenna is set into vibration at the rate of 1,500,000 times per second (frequency equals 1,500,000) and that the length of each ether wave created is 200 meters Tuning the Receiving Antenna Under "Inductance" and "Capacitance" it was brought out that inductive reactance has the effect of a resistance upon an alternating current and that capacititive reactance has just the the opposite effect. It was also brought out that inductive reactance increases and capacitive reactance diminishes with increased frequency and vice versa. If, then, a circuit has an inductance and a capacitance selected at random there will be a certain frequency at which the two reactances are equal and, 34 A B C OF VACUUM TUBES since they are exactly opposite, the total reactance is zero. This frequency is called the "resonance frequency." On the other hand, if a certain frequency is selected at random then the two reactances must be adjusted so that they are equal for this fre- quency and, since they are opposite, they will then neutralize each other and the total reactance will be zero. Now, when a receiving antenna is acted upon by ether vibra- tions of a certain definite frequency (the frequency of the oscil- lations in the transmitting antenna) an alternating (oscillating) E.M.F. is produced and an oscillating current will tend to flow in the antenna. Whether or not the current will actually flow and whether it will be of maximum value for the E.M.F. applied, will depend upon both the actual resistance and the total reactance (effective resistance) in the antenna circuit. The actual resistance may be assumed to be and in practice is, fairly low, and with an antenna already erected it is, on the whole, a fixed value. The current then depends upon the total reactance which, as has been stated, may be made zero by the proper adjustment of inductive and capacitive reactance. If the reactances are made equal for this definite applied frequency then the antenna may be said to be "tuned" or "in resonance" with the frequency and therefore with the frequency of oscilla- tions in the transmitting antenna. Since inductive reactance may be increased and decreased by varying the number of turns of wire on a coil and since capacitive reactance may be increased and decreased by allowing the movable plates of a variable air condenser to interleave to a greater or lesser extent, tuning may be accomplished by either a variable coil or a variable condenser. Increasing the inductance of the coil or the capacitance of the condenser means that the resonant frequency is decreased, pro- viding the coil and condenser are in series with each other in the INTRODUCTORY 35 circuit. That is, if the circuit is in resonance with a certain fre- quency and either the inductance of the coil or the capacitance of the condenser is increased, the circuit is no longer in resonance with this frequency but would be in resonance with a lower frequency of ether oscillations produced by, perhaps, some other transmitting antenna. The counter condition is of course true, that if the coil inductance or the condenser capacitance were de- creased, the circuit would then be in resonance with a higher frequency of ether oscillations produced, possibly, by still an- other transmitting station. Either one of these stations or any one of possibly a large number of stations might then, of course, be picked up at will by simply tuning the receiving an- tenna circuit in this manner. Wave-length of ether oscillations is perhaps thought of more popularly than frequency, and under "Wave Length" it was pointed out that as the frequency of oscillations increases their wave length diminishes and vice versa. If, then, we wish to speak in terms of wave-length, we may say that an increase of inductance or capacitance in a receiving circuit increases the wave length at which that circuit is in resonance and that a de- crease of either of them decreases this wave length. Speaking still in terms of wave length rather than frequency, it may now be said that tuning is simply the process of adjusting inductive reactances (coils) and capacitive reactances (condensers) in a circuit so that, for the wave length of the ether oscillations act- ing upon the (antenna) circuit, the two reactances are equal and, being opposite, neutralize each other to reduce the total reactance to zero. The Antenna as a Complete Circuit As a general rule, the antenna appears not to be a complete circuit. If Fig. 1 1 is considered it is seen that there is a capaci- 36 A B C OF VACUUM TUBES tance effect (or a condenser effect) between the free end of the antenna and the end connected to earth or to a "counterpoise" consisting of a number of wires stretched beneath the antenna. That is, every inch of the antenna has a capacitance to earth (or to the counterpoise) so that considering the antenna as a Antenna ■% Supported • here y Note < There is Distributed Inductance over the Length of Antenna and Down-Lead <-■ Antenna Down -Lead { ^Antenna Terminal Variable Coil ( Variable Lumped Inductance) jx - ---- Antenna Supported here Effective . Capacitance ' 'Distributed) # Ground Terminal--'*! Variable Condenser (Variable Lumped Capacitance) ~ Earth or Counterpoise Fig. II — Scheme of antenna as a complete circuit. whole, it may be regarded as one plate of a condenser, with the earth or counterpoise acting as the other plate. There is then a circuit which is closed so far as alternating current (especially radio- frequency alternating current) is concerned and cur- rent readily flows in the circuit under the proper conditions mentioned above. The reason that an antenna, particularly a transmitting an- tenna, has to be elevated a considerable distance above the earth is in order to allow a large amount of ether to be acted upon and set in motion by the antenna oscillations. It is readily seen that the higher the antenna the larger the amount of ether there is between its top and the surface of the earth. In the case of a receiving antenna this also applies to a considerable extent, since in this case it is desirable to have as large an amount of INTRODUCTORY 37 vibrating ether acting upon the circuit as possible. The re- sponse in a device to make signals perceptible to our senses depends very greatly upon the auxiliary devices used, and it is possible to provide such sensitive apparatus and to amplify cur- rents so greatly that a low receiving antenna may be entirely permissible. The devices to be considered in the following chapters are indeed so sensitive and can be made to amplify currents to such great extents that receiving antennae may even be done away with in practise. It must be borne in mind, however, that no matter how efficient the receiving apparatus may be, better results are obtained with the use of antennae which are the better, the higher they are erected. In the following chapters the little lamps called "vacuum tubes" "audions," "radiotrons," and so forth, are considered. Results obtained with them are truly remarkable and it is due to their adoption that such long ranges are now possible in radio communication without any increase in the power of transmitting stations. Their action is truly absorbingly inter- esting. CHAPTER II. THE VACUUM TUBE AS A RECTIFIER AND RELAY WITHOUT MOVING PARTS Tube construction — The Edison Effect — Electron emission from a heated filament — Dependence of plate current upon plate potential — Dependence of plate current upon filament current — Effect of grid poten- tial upon plate current — Relay action — Rectification. Tube Construction A vacuum tube is somewhat similar in construction to an ordinary incandescent electric lamp which has a filament sup- ported inside a glass tube or bulb from which the air has been exhausted. When an electric current flows through the lamp filament it is heated to incandescence and produces light. A vacuum tube also has a filament which may be made incan- descent by allowing electric current to flow through it, but the production of light in this case is merely an accompaniment of more essential phenomena as will be explained. When air is exhausted from any kind of a vessel a vacuum remains and the degree of vacuum depends upon the degree of air exhaustion. The vacuum within a so-called "vacuum tube" is very much higher than that within an incandescent electric lamp. What are known as "hard" tubes have an extremely high vacuum, -often indeed the highest possible vacuum attainable. Others known as "soft" tubes contain a small amount of gas and, therefore, a somewhat lower vacuum. Each class of tube has its particular uses, although the "hard" tubes may be used for all purposes. Regardless of the degree of vacuum, a tube contains, in 38 VACUUM TUBE AS RECTIFIER AND RELAY 39 addition to a filament, a "grid" and a "plate" arranged, for example, as in Fig. 12. The grid is always placed between the filament and the plate. The filament is usually of very fine tungsten wire and may be straight, "V" shaped or shaped like a "W." The apexes Spiral Grid Filament — - Plate Support - Filament Support Glass Stem-- Cement Holds Tube in Base ~- Glass Wall of Tube ■-Filament Support \ (Springy) Plate (cut away) Grid Support -Wires Sealed here <■ Leading-in Wires -Brass Shell Base <— -Prongs Fig. 12 — Construction of a typical vacuum tube. of the "V" and "W" shaped filaments are upwards. No matter what the filament shape, it is supported in such a manner as to prevent its displacement when jarred. The tube of Fig. 12 has a straight tungsten filament supported at its upper end by a nickle rod, to which it is carefully welded. The lower end of the filament wire is welded to a shorter nickle rod and both rods are anchored into a glass stem. The longer rod is springy, so that it will hold the filament taught. 40 VACUUM TUBE RECTIFIER The grid may be a mesh of nickle wire wound about two supports. In the figure it is shown as a spiral or helix, so supported by a nickle rod that the filament becomes the axis of the spiral. Each turn of the spiral grid is welded to a nickle supporting rod, the lower end of which is anchored into Fig. 13 — Various forms of vacuum tubes and sockets. the glass stem. The grid must, in any case, be rigid enough to withstand considerable jarring. The plate may be of molybdenum, nickle or thin sheet steel. It is quite often cylindrical in shape, but may also be flat or shaped like a cylinder flattened out on two sides. The plate VACUUM TUBE AS RECTIFIER AND RELAY 41 ---> 'urrenf Neg. Filament Terminal Plate Pos. Potential on Plate Pos . Battery + T erminal Fila- ment Rheo- Bat- tery Plate = Battery — <• Neg. BatteryK Terminal >» ^oo/y Current Indicating Device (A) Plate Current Flows. Gr/a' /\ ment Plate Neg. Potential on Plate Neg. Filament Terminal Neg. Battery ■ 0_ Terminal Plate Battery Pos. Battery^ -t-" Terminal **Ooff Current Indicating Device (B) No Plate Current Flows. Fig. 14 — The Edison Effect or one way conduction of electric current within a vacuum tube. 42 A B C OF VACUUM TUBES must also be rigidly supported. In the figure there is a cylin- drical plate of nickle so supported by a nickle rod that it encloses the grid and, therefore, the filament. The filament is then the axis of both the spiral grid and the cylindrical plate. The plate support is welded to the plate and the lower end of the support is securely anchored into the glass stem. There are, then, three members called "electrodes," the filament, the grid and the plate. A vacuum tube is seen to be a somewhat more complicated device than the incandescent electric lamp. The four prongs which extend below the base of the tube are for connection into a circuit. Each of these is welded to a leading-in wire which connects it to a support. In this manner the two filament ends, the grid and the plate are each connected to a prong. The leading-in wires are very carefully welded to the supports and sealed into the glass stem, so that at no future time may there be any leakage of air into the tube. Air leakage would render the tube unfit for use. Fig. 13 illustrates a few of the various forms of tubes and some tube sockets or receptacles. When a tube is inserted into a socket, each tube prong makes contact with a spring contact piece which is connected to a terminal binding post. Two binding posts are for the filament connections and one each is for the grid and the plate. This provides a convenient way of holding a tube and connecting it into a circuit. The Edison Effect In both Fig. 14- A and 14-B there is a battery called the "plate" or "B" battery connected between the plate and one of the filament leads. In each figure, also, a very sensitive current indicating device is connected into the plate circuit. Current may be allowed to flow through the filament from a VACUUM TUBE AS RECTIFIER AND RELAY 43 smaller battery called the "filament" or "A" battery. The current flowing through the filament may be controlled by a variable resistance in the filament circuit. This variable resistance is called a "rheostat.' ' Increasing this resistance causes decreased filament current arid vice versa. Also, of course, if the filament rheostat is turned off, no current flows in the filament. When there is no current flowing in the filament it is cold, but when current is allowed to flow, the filament is thereby heated to a temperature depending upon the current strength. The filament rheostat may, there- fore, be used to control the filament temperature by controlling the filament current. Suppose that the filament current is turned off (filament cold) and the positive terminal of the plate battery is con- nected to the plate, as in Fig. 14-A. Observation of the current indicating device shows that no current flows in the plate circuit. With the filament still cold (rheostat turned off) the plate battery connections are reversed so that the negative terminal of the battery is connected to the plate, Fig. 14-B. Observa- tion again shows that there is no current flowing through the indicating device. The negative terminal of the plate battery is still connected to the plate and the rheostat is now turned on, allowing enough current to flow through the filament to heat it to incandescence. Observation once again shows no current in the plate circuit through the indicating device. Now, with the filament still glowing, the plate battery connections are changed back again so that the positive battery terminal is connected to the plate, as in Fig. 14-A. This time there is an appreciable current indicated as flowing in the plate circuit from the positive terminal of the battery to 44 A B C OF VACUUM TUBES the plate, across the space within the tube to the filament and back to the battery. This is an interesting state of affairs. A direct current of electricity is flowing from the plate to the filament through the vacuum of the tube. There is elec- trical conduction between these two points, but only when the filament i glowing and the plate is connected to the positive terminal of the plate battery. This phenomenon of one way conduction of electric current through a vacuum was noted by Thomas A. Edison and is termed "the Edison effect." Like numerous other discoveries, however, it was not fully investigated and used until some time later. Electric current always flows or tends to flow from a point of high to a point of low potential, This may be compared to the flow of water down a hill. A point in the stream at the top of the hill is at a higher "potential" than a point in the same stream at the bottom of the bill. In the case of elec- tricity, the high potential point is said to be the point of "positive" potential and the lower potential point that of "negative" potential. An electric current, therefore, flows or tends to flow always from a point of positive to a point of negative potential. When the positive terminal of the plate battery is connected to the plate, the potential of the plate is positive with respect to that of the filament, because current will flow from the plate to the filament, inside the tube, providing the filament is lighted. The glowing filament, in this case, causes the path or circuit from plate to filament to be closed. Electron Emission from a Heated Filament The smallest possible particle of negative electricity is called an "electron." The word means "carrier of electricity." An VACUUM TUBE AS RECTIFIER AND RELAY 45 electron is then the smallest possible negative electric charge and is, moreover, a carrier of electricity. When the filament is heated, by the electric current flowing through it, thousands of these electrons are projected at high velocity from it like buckshot from a shotgun. The higher the filament tempera- ture the more electrons there will be projected in any given length of time. Now, when the filament projects an electron from itself, it loses a minute portion of its negative charge and, since the negative and positive charges are normally equal, if the filament loses some of its negative charge, the charge remaining upon it is positive. If there is nothing to prevent it, then, the filament will attract electrons back to itself at the same rate as they are emitted. Considering the space within the tube, there are electrons in constant motion, some away from and some back to the filament. It must be remembered that unlike charges of electricity attract each other and that like charges repel each other. If the plate, however, is now given a positive charge by connecting it to the positive terminal of a battery, as in Fig. 14-A, it will attract to itself at least a portion of the electrons present in the tube space. These electrons, being current carriers, then cause a current of electricity to flow from the plate to the filament and back through the battery, the battery being the source of the current. That is, when electrons are attracted to the plate the space between it and the filament is made conducting and a current flows from the battery. The strength (or rate of flow) of this plate current depends upon the number of electrons (current carriers) which bridge the filament-plate space per unit of time. In other words, the current depends upon the rate at which electrons are attracted to the plate. If the plate is negatively charged (its potential negative 46 A B C OF VACUUM TUBES with respect to the filament) no plate current can flow because the plate repels the electrons. (Like charges repel). That is, if there are no electrons bridging the space between filament and plate no conduction can take place. This, then, explains why there is electrical conduction through a vacuum when the filament is glowing and the plate is positively charged and, also, why there is no conduc- tion when the plate is negatively charged or the filament is cold. Dependence of Plate Current upon Plate Potential The positive potential of the plate determines the number of electrons which may be attracted to it per unit of time and, therefore, the strength of the plate current. But suppose that the plate potential has been increased up to the point where electrons are attracted just as rapidly as they are shot from the filament into the tube space. A higher plate potential will not be able to attract them in any greater numbers, per unit of time, because it is already attracting them just as fast as they are being emitted from the filament. There is a limit, then, to the increase of plate current with an increase of plate potential. If larger plate current is desired, electrons must be projected from the filament in greater numbers. The value of the positive potential on the plate depends upon the voltage of the plate battery. Therefore, in view of the foregoing, the plate current increases with the battery voltage only up to a certain point, providing no change is made in the filament current. If the filament current is increased by a certain amount, the plate current increases, with increase in battery voltage, up to a new point, after which no further current increase may be had unless the VACUUM TUBE AS RECTIFIER AND RELAY 47 filament current is again increased. There is, of course, a limit to the current which may be made to flow through the fila- ment if it is not to be burned out. There is then a final limit to the current which can flow in the plate circuit no matter how high the plate battery voltage may be made. In practice, it is desirable to burn the filament at a moderate temperature and to secure the desired plate current by selecting the proper plate battery voltage. This will lengthen the life of the tube filament. Dependence of Plate Current upon Filament Current The rate of electron emission increases, as has been said, with the increase of filament current (increase of filament temperature). If the plate potential is held at a constant value and the filament current is increased, there will be an increase of plate current up to a certain point. The point where no further increase of plate current is had with increasing filament current is that at which the filament is emitting elec- trons as fast as the plate can attract them. Then, no matter how much faster the electrons are shot from the filament into the tube space, the plate will only attract a certain number of them per unit of time. If the electrons are emitted at still increasing rates there will be no increase of plate current unless the potential of the plate is raised (plate battery voltage increased) in order that the plate may attract them in greater numbers per unit of time. If there are more electrons emitted by the filament per unit of time than the plate can attract, some of the electrons in the tube space are continually reaching the plate while others are falling back upon the filament. Another way of viewing this matter is to consider the 48 A B C OF VACUUM TUBES lumped effect of all the electrons in the tube space between filament and plate. Since each electron is a negative charge, the total electric charge in the space is negative. There are, then, two electric charges acting upon the electrons just leaving the filament. One is the positive charge of the plate and the other is the negative charge of the space (negative space charge). If the positive charge of the plate is greater than the negative charge of the space, electrons will be drawn to the plate from the space and others will be pulled into the space (from the filament) to take their places. But if the positive plate charge is exactly neutralized by the negative space charge, this space charge will repel one electron back to the filament for every extra electron projected from the filament into the space. Only a certain number of electrons per unit of time are, therefore, attracted to the plate and the plate current is at maximum value. This is called the "space charge effect." Suppose that some concrete hypothetical examples are con- sidered. The plate potential is assumed to be at such a posi- tive value (due to plate battery voltage) that it can attract iooo electrons per second. The filament temperature is low, at the start, and only ioo electrons are emitted from it per second. The ioo electrons are shot into the tube space each second to make the negative space charge at all times equal to that of ioo electrons. The plate charge is greater, however, and pulls electrons out of the tube space at the rate of ioo per second. This corresponds to a certain value of plate current. Now, the filament temperature is increased and 500 electrons are emitted per second. The plate will attract 500 electrons per second and the plate current is increased. The effect of the plate charge is still greater than that of the space charge. The filament temperature is again increased and VACUUM TUBE AS RECTIFIER AND RELAY 49 to such an extent, this time, that 1000 electrons are emitted per second. The plate now attracts 1000 electrons per second from the space. The effect of the plate charge is now equal to that of the space charge, so that for every electron shot into the space, one is attracted to the plate. But now suppose that the filament temperature is again increased until 1500 electrons are emitted per second. There are now 1500 electrons present in the space each second. The plate can only attract 1000 of them from the space so the negative space charge repels the extra 500 back to the filament. The plate current does not increase, because no matter how many electrons over 1000 per second are emitted, only that number per second are actually drawn to the plate from the space. If the potential of the plate is raised until it is able to attract 1500 electrons per second, the plate current increases until the plate is actually attracting 1500 electrons to it each second. Then the space charge again equals the plate charge and if electrons are emitted at a still greater rate, say 2000 per second, there are still only 1 500 reaching the plate per second and the plate current remains constant at the higher value. Effect of Grid Potential upon Plate Current It has been pointed out that the grid electrode is located be- tween the filament and the plate of a tube. The grid must then, of course, be situated in the region of the space charge. If a positive potential is applied to the grid by a grid battery, as in Fig. 15, its potential is positive with respect to the filament and the positive charge thus placed upon the grid neutralizes some of the effect of the space charge. The result is an increase in plate current and the grid may be said to be adding the effect of its positive charge to that of the plate in order to cause more electrons per second to be attracted to the latter. If the positive 5o A B C OF VACUUM TUBES charge on the grid is sufficiently increased, however, the plate current ceases to increase because electrons are then being at- tracted to the plate just as rapidly as possible. A saturation point is then reached. When the grid is positively charged it will also attract some electrons to itself and cause a current to 6rid Meg. Battery Grid A Fil. Plate + <\Pos Plate ~=~ Battery - §Neg. Current Indicating Device Fig. 15 — One method of varying the grid potential. flow in the grid circuit, from grid to filament inside the tube. This grid current also increases, up to a certain point, with the increase in positive grid potential. If a negative potential is applied to the grid from the grid battery, its effect will be added to that of the space charge. The result is a decrease of plate current and the grid may be said to be opposing the effect of the plate. When the grid is negatively charged, it repels electrons back to the filament and therefore no grid current flows. Electrons in large numbers may, how- ever, pass through the spaces between the grid wires because of VACUUM TUBE AS RECTIFIER AND RELAY 51 their high velocity and be attracted by the plate. If the grid potential is too negative it will completely neutralize the effect of the positive plate charge and cause the plate current to be c <0 3 O 80 70 60 50 40 30 5 20 JO o- 60 Volts *y ^y ^ / <7 J) / \^ 7 -3 -2 + 6 +7 -I 0+1+2+3 +4 +5 Grid Poten+ials (arbitrary units) Fig. 16 — Characteristic curves of grid potentials and corresponding plate current values. reduced to zero. This value of negative grid potential is called the "cut-off" potential. The external portion (part outside of the tube) of the grid circuit is connected at one end to the grid and at the other to the filament. Therefore when potentials are applied to the grid, they are either positive or negative with respect to the filament. That is to say, when a higher potential is applied to the grid than to the filament its potential is "positive" with respect to the filament. The reverse is also, of course, true. A graph is shown in Fig. 16, which pictures the effect of 52 A B C OF VACUUM TUBES various grid potentials upon plate current for three different values of plate potential, the filament current being the same in all cases. It is to be noted that the variation of plate current with grid potential is not linear at all times, but that the "charac- teristic" graphs are curved at their upper and lower portions. This is a characteristic of vacuum tubes which is very valuable, as will be seen more clearly later on. The graph of grid poten- tials plotted against plate current is, therefore, called a "char- acteristic curve." Relay Action The action of a grid may be compared to that of a telegraph relay, schematic circuit of which is shown in Fig. 17. The armature of the relay is Line Relay Magnet Coils 1<— Spring '• — o Sounder ^Contacts { MS .."7 : ---^ Relay Backstop Spring Armature Local Battery + local Circuit ,_i 'Pivot , Fig. 17 — Circuits of telegraph relay. magnetically attracted over toward the poles of the electro- magnets when the key in the line is closed and current flows through the magnet coils. When the armature is attracted, a VACUUM TUBE AS RECTIFIER AND RELAY 53 contact is made and a local circuit through a battery and a tele- graph sounder is closed. The potential applied to the terminals of the magnet coils may be very small but when the contact is closed a comparatively large current is allowed to pass through the sounder coils and operate the sounder. A relay is then a device which allows a small cause to produce a large effect. In the case of the vacuum tube, the grid is placed much closer to the filament than is the plate. Small potentials when applied to the grid therefore have a larger effect upon the plate current than they would if applied to the plate. The vacuum tube is, then, a relay. Its grid is comparable to the armature of the telegraph relay and the plate circuit of the tube is comparable to the local sounder circuit. The very interesting feature of the vacuum tube is, however, that it has no moving parts. It is true that the electrons move, but they have no weight (are not af- fected by gravity) and cannot be considered as parts of the tube. As far as can be seen, no action takes place within a tube except the heating of the filament to produce light. Rectification In Fig. 18 a generator of alternating E.M.F. is connected into the grid circuit in place of the battery of Fig. 15. Refer- ring now to Fig. 19, the normal potential of the grid is assumed to be the same as that of the filament, that is, it is zero with respect to the filament. A certain steady value of plate current then flows, depending upon the plate potential and filament current. This may be called the "normal" value of plate cur- rent. The alternating potentials applied to the grid circuit by the generator cause the grid to alternately become positive and negative with respect to the filament. When the grid is positive the plate current increases above the normal value. When the 54 A B C OF VACUUM TUBES grid is negative the plate current decreases below the normal. There are variations or alternations of plate current above and below this normal value which are in step with the grid poten- tial variations. Note particularly, however, that the increases are, in this particular case, larger than the decreases. That is, that equal variations of grid potential cause unequal variations of plate current. This being the case, the average value of the Grid /\ Fila- ment Generator ©of Alternating E.M.E Plate •f QPos . , Plate Battery JrTegr. & Current Indicating Device Fig. 18— Continuous variations of grid potentials. plate current is at every instant greater than the normal value. If the generator were started and stopped periodically this average value would rise when the generator is running and fall back tc normal when the generator is momentarily stopped. There would then be periodical increases and decreases of average plate current in step with the starting and stopping of the generator. As far as this average value is concerned there appears to be what is called a "rectification" of the more rapid plate current variations. This is "apparent recti- VACUUM TUBE AS RECTIFIER AND RELAY o;> .2 c o ."H b£ ■*-> ■i— G C o s > 1. (s|iun X"aej4iqiB) ^.uajJOQ aieid 56 A B C OF VACUUM TUBES fication" of the plate current. Coincident with this action there is also an actual rectification of the grid current. That is, when the grid receives a positive charge from the generator it attracts electrons to itself and a current flows in the grid circuit. But when the grid receives a negative charge it repels electrons and no current can flow in the grid circuit. The action of the grid therefore changes the alternating current which would otherwise flow under the influence of applied alternating E.M.F. into a pulsating current. This is actual rectification. If, by means of a grid battery (Fig. 20), there is a certain normal positive potential applied to the grid, the normal plate Grid Battery ^Generator of (r^j) A Item dh'ng V 7 E.M.F. Fit. Pos. =EZ Plate =- Battery Battery —==- 'O ff ■ Neg.%^ Current Indicating Device. Fig. 20 — One method of applying a desired normal grid potential. current is increased to a greater steady value. In this case the same equal variations of grid potential produced by the generator alternately increase and reduce the positive potential VACUUM TUBE AS RECTIFIER AND RELAY 57 on the grid. This again causes unequal variations of plate cur- rent above and below the new normal value, but the decreases are greater than the increases. The variations are, however, still in step with the grid potential variations. Since a grid cur- rent is always flowing, there is no actual rectification of grid current but only an apparent rectification. There still is, never- theless, apparent rectification of the plate current. It is interesting to note that both the more rapid variations of plate current and the slower variations of average plate current may take place in the circuit at the same time if the generator is periodically started and stopped. Under favorable conditions currents of both the higher and lower frequencies may flow in the plate circuit. It is a characteristic of vacuum tubes that the increase and decrease of plate current with variations of grid potential is not linear. This has been previously mentioned, but it may be pointed out here that this very characteristic may be made use of in operating the tube as a rectifier. Straight lines drawn to indicate values of grid potential and plate current are seen, in Fig. 19, to cross each other on the graph indicating the relation between the two. If two such lines are drawn to indicate the normal grid potential and the coincident normal plate current, the point where they cross on the characteristic curve may be called the "operating point," since variations in both take place about this point. It is obvious, therefore, that the operating point may be shifted at will by the application of the required normal grid potential. In order to secure apparent rectification of plate current vari- ations it then becomes necessary to have the operating point on either the upper or lower bend of the characteristic curve. It is most always brought to the lower bend to avoid grid current flow and very high values of plate current which add nothing 58 A B C OF VACUUM TUBES to the efficiency of the tube, but actually result in poorer operation. With the characteristic curve of Fig. 19 a grid current will flow in the tube at certain times because the grid potential is allowed to become positive periodically even though the operat- ing point is on the lower bend of the curve. All tubes, however, do not have the same characteristics and in some cases it might be necessary to apply a normal negative potential to the grid to bring the operating point to the lower bend of the curve. If, then, the applied alternating potentials never exceed this value of negative potential, no grid current will flow at any time. There is no rectification of grid current, but there is still apparent rectification of plate current. In the next chapter the practical application of the rectify- ing action to radio reception is brought out. CHAPTER III THE VACUUM TUBE DETECTOR The telephone receiver — Simple detection — Detection with grid con- denser — Effect of gas in a detector tube — Heterodyne action or the pro- duction of beats. The Telephone Receiver When ether waves are produced at a distant transmitting station and, in turn, cause oscillating electric current to flow in a receiving antenna, it is necessary to provide some kind of an indicator which will make the presence of these oscillations manifest to one of the senses. It is customary to translate these Cap Thready /Permanent hard steel magnets ■Soft Stee/ Pole Pieces ■'Binding Post Electromagnet Coils Soft Iron Diaphragm Ordinary Receiver Fig. 21 — Construction of a typical telephone receiver. oscillations into audible sound so that signals may be perceived by the sense of hearing. A telephone receiver, the construction of which is shown in Fig. 21, has two coils of wire, each wound in many layers around an iron core to produce two electro-magnets. A metal diaphragm is so supported that it may be attracted by the magnet poles or released, depending upon the strength of magnetism in the poles. An increase of 59 6o A B C OF VACUUM TUBES electric current through the magnet windings causes the dia- phragm to be attracted and a decrease of current causes it to be released, because the strength of magnetism is thereby in- creased and decreased. If the diaphragm is attracted and re- leased periodically it is caused to vibrate, and if the mechanical frequency of vibration (number of attractions and releases per second) is somewhere between 15 and 15,000 vibrations per second, the air waves thereby created will produce audible sound in the human ear. The more rapid the vibrations are, the higher the pitch of the sound which is produced. The telephone receiver is a very sensitive indicator or translator and is very extensively used in radio work for this purpose. Simple Detection In Fig. 22 there is an antenna circuit containing a coil and a condenser, both of which are variable to provide for the tuning of the circuit. The opposite terminals of the coil are connected to the grid and filament of a vacuum tube as shown. Suppose that continuous oscillations are present in the an- tenna and, therefore, flowing in the coil. If the antenna is in resonance with a transmitting antenna, these oscillations will be of maximum amplitude and will set up radio frequency oscillations of potential at the coil terminals, which will also be of maximum amplitude. Now, the coil terminals are connected to grid and filament so that the oscillating potentials must be applied to the grid and filament of the tube. The oscillating potentials at the coil terminals have now replaced the alternat- ing E.M.F. produced by the generator of Fig. 18, and their frequency is very much higher than the alternating E.M.F. then considered. The plate current variations now take place at radio frequency instead of at the frequency of generator VACUUM TUBE DETECTOR 61 E.M.F. or potential variations. Fig. 19 may be referred to again and the operating point considered to be on the lower bend of the curve. Equal variations of grid potential at the radio frequency produce unequal variations of plate current at radio frequency. Now, radio frequency is always entirely be- yond the frequency range of audible sound, so that if the tele- Anienna Plate ' Batfery Variable Inductance Variable Capacitance telephone , Receiver Filament Rheostat -=- Grouncf Fig. 22 — Simple detector circuit. phone receiver diaphragm vibrates, it does so at a rate which is too high to produce sound. As a matter of fact, however, the diaphragm does not vibrate at such frequency because of its weight and because very little current of radio- frequency can flow through the magnet windings. It must be remem- bered that the reactance of a coil (or coils) increase with the frequency and with the insertion of an iron core. The react- 62 A B C OF VACUUM TUBES ance of an ordinary telephone receiver winding is very high indeed to currents of radio- frequency. The current that does flow through the receiver windings is the average value of direct current in the plate circuit. In the case under consid- eration this average current is higher than the normal value and remains constant so long as the amplitudes of the antenna oscillations do not vary. Therefore, when unmodified un- damped waves are radiated by a transmitting station no sound is produced in a telephone receiver at the receiving station with a simple detector circuit. Suppose, however, that damped waves are radiated by the transmitting, station. In this case it will be remembered that there are groups (or trains) of oscillations produced in the re- ceiving antenna, each composed of radio frequency oscillations whose amplitudes decay from a maximum value to zero peri- odically. The grid and filament circuit of Fig. 22 then being still connected across the antenna coil, radio-frequency potential variations are applied to the grid, whose amplitudes decay from a maximum to zero during each group of oscillations, as shown in Fig. 23. As also shown in the graph of this figure, the radio- frequency plate current variations also decrease in amplitude during each group or train of oscillations and there is a variation in the average plate current which rises and falls once for each oscillation train. If the frequency of the oscil- lation trains is within the limits of audibility (15 to 15,000 per second) the frequency of the variations of average plate current is also an audible frequency or, as it is called, an "audio- frequency." Current variations of such comparatively low fre- quency pass through the receiver windings and cause the dia- phragm to vibrate and to produce sound waves of the same frequency which, being audible, are heard by the human ear. The sound heard depends then upon the frequency of the oscil- VACUUM TUBE DETECTOR 63 o -+- CD a. Norma/ Plate -a Current- Zero Radio Frequency-.^ — Frequency of "Oscillation Trains "same as Wave Train Frequency. (Only One Train Shown) Fig. 23 — Rectification effect in plate current with damped grid potential variations. 64 A B C OF VACUUM TUBES lation trains and increases in pitch with that frequency. Sup- pose a case in point is considered. There is a transmitter at a distant station which creates in the transmitting antenna oscil- lations whose frequency is iooo per second. The transmitter could be a 500 cycle synchronous rotary gap or quenched gap spark transmitter. Ether wave trains are set up whose fre- quency is also 1000. These ether waves cause trains of oscil- lations in the receiving antenna, variations of average plate cur- rent, receiver diaphragm vibrations and, finally, sound waves, all of the some frequency, 1000 per second. If the distant transmitter were a 240 cycle set, ether wave trains of 480 per second would be created and the frequency of the sound waves produced by the receiver diaphragm would be 480 per second. The pitch of the tone would be higher in the first case than in the second, although both tones would be musical. Damped oscil- lations, being modified radio frequency oscillations, produce audible sound in a telephone receiver. If the undamped oscillations generated by a transmitter are modified by auxiliary apparatus in such a manner as to vary the amplitudes of the radio- frequency oscillations at an audio- frequency rate (frequency with the limits of audible sound), air waves of the same audible frequency will be produced by the receiver diaphragm. The radio- frequency oscillations are molded into groups and that group frequency is selected which will give the most pleasing pitch of tune in the telephone re- ceiver. Such a process of molding is called "modulation." Fig. 24 illustrates the effect of modulated continuous oscilla- tions in a simple detector circuit. The group frequency is maintained at a constant value, usually, so that the tone does not change at any time. Different transmitting stations may, however, select different group frequencies and therefore pro- duce tones in a receiver which differ from each other. A trans- VACUUM TUBE DETECTOR 65 mitting station can then often be identified by its tone fre- quency. A radio-telephone transmitter must use a generator of con- tinuous radio frequency oscillations but, in this case, the radio 1 ' ogfaSS? c o Q. / Radio Frequency Plate Current Variations ^ — Normal Grid Potential —Audio Frequency Grid Potential Variations. (Only one Cycle shown.) "■Radio Frequency Grid Potential Variations. Fig. 24 — Detection of modulated continuous oscillations at a constant group frequency. frequency current amplitudes are not always varied at the same audible frequency as is usually the case with modulation for telegraphic purposes. The frequency of the sound waves cre- ated by the human voice averages around 800 per second, but constantly increases and decreases with the pitch of tone. Every change in inflection of the speaking voice and every change in 66 A B C OF VACUUM TUBES tone of the singing voice means a change in the frequency of the air waves created. In the case of music produced by various instruments, every change in tone also means a change in air wave frequency. In the operation of a radio-telephone trans- mitter, devices are provided which will cause the originally generated undamped radio frequency oscillations to be molded or modulated constantly in amplitude at constantly varying tone frequency. The constant changes in tone (group) frequency therefore produced in the receiving antenna cause constantly varying changes in the current flowing through a telephone re- ceiver of the simple detector circuit. The result is, of course, air waves and sound created by the receiver diaphragm of con- stantly changing frequency in step with the frequency of the sound waves acting upon the distant transmitter. Fig. 25 gives an idea of how this is accomplished in the receiving circuits. In all of the above considerations it is, of course, understood that the receiving antenna must be tuned to the radio fre- quency oscillations no matter what the group or tone frequency may be. Detection with Grid Condenser In the case of simple detection there may be actual or appar- ent rectification of grid current, depending upon the normal grid potential. If a small condenser is connected into the grid circuit close to the grid, however, the rectification of grid cur- rent is actual. There is also apparent rectification of the plate current variations. The mode of functioning is some- what different, however, when a grid condenser is used. Assume that, due to resonance with a transmitting antenna, there are damped radio frequency oscillations of maximum possible amplitudes induced in the receiving antenna Radio VACUUM TUBE DETECTOR 67 7ero Radio Frequency Grid Potential Variations — \ N Radio Frequency Plate Current Variations Fig. 25 — Detection of voice modulated continuous oscillations at a varying group frequency. 68 A B C OF VACUUM TUBES frequency alternating potentials are applied to the grid through the grid condenser. When the grid receives a positive charge from the circuit it attracts electrons to itself, a grid current flows and the plate current is momentarily increased, since the operating point is now assumed to be on the straight portion of the curve. (Fig. 26). The grid then receives a negative charge, repels electrons, no grid current can flow and the plate current is reduced. But, when the grid was positive and elec- trons were attracted to it these electrons were trapped on the grid because of the "blocking" action of the grid condenser. When, during succeeding alternations of the applied potential, the grid receives a positive charge more electrons are attracted to the grid and are trapped. During one group of oscillations then, the grid accumulates electrons, its negative potential increases and the average plate current decreases. (Electrons are negative charges.) It may be pointed out here that the normal potential of the grid with respect to the filament is always zero. During a group of oscillations the negative charge on the grid is built up to a comparatively large value and, unless the charge leaks off of the grid, the grid potential will not be zero at the beginning of the next group of oscillations. During the group of oscillations just con- sidered the operating point has slid down the characteristic curve. If this negative grid charge does not entirely leak off, the next group of oscillations will cause the negative grid potential to increase and the operating point to slide still further down the curve. It is obvious that the cut-off grid potential might be reached and the plate current stopped entirely. When this happens the tube is said to be "blocked" or "choked." It is paralyzed until the grid charge is allowed to leak off, for example by placing the ringers on the grid terminal. It is quite necessary, therefore, to provide a path VACUUM TUBE DETECTOR 69 One Train of Radio Frequency Antenna Oscillations Fig. 26 — Rectification or detection of damped oscillations with a grid condenser. 70 ABC OF VACUUM TUBES through which the negative charge may leak when it becomes large, so that the grid potential may be returned to zero and the plate current to normal in time for the next group. This may be accomplished by connecting a resistance called a "grid leak resistance" across the grid condenser terminals or directly between the grid and the filament. The value of resistance must be high enough to prevent any great flow of current through it until the maximum charge has accumulated upon the grid. It should not be too high, however, because the charge would not then leak off quickly enough, but might accu- mulate until it leaks off through the glass walls of the tube, the dielectric of the grid condenser or the vacuuous space between filament and grid. This might cause a thumping noise in the telephone receiver. In the next section tubes containing gas are described. If such a tube is used as a detector the negative grid charge may leak from the grid to the filament because of the comparatively good conducting path then offered. If the gas content of the tube is high enough no grid leak is necessary. Modern gas content tubes, however, usually require a grid leak resistance when used with a grid condenser. In Chapter V various practical circuits are described which show the schematic connections of grid condensers and grid leaks. No grid battery is ever needed with a grid condenser. The rectification of plate current oscillations does not depend entirely upon the location of the operating point because it is the cumulative effect of the negative grid charge which causes the plate current decrease during each group of oscil- lations. As a matter of fact, however, it is desirable to have the normal operating point on the straight portion of the curve so that the decrease of grid potential caused by accumulation of negative charge will produce the greatest VACUUM TUBE DETECTOR 71 possible change in plate current. Reference to Fig. 26 will make all these points more clear. The effect of the grid condenser does not change the relation between the group frequency of the antenna oscillations and the group frequency of the plate current variations. The latter is still the same as the former and the frequency of air waves (pitch of sound) is still the same as the group frequency of oscillations in the antenna circuit. The detector with grid con- denser may be used for the reception of damped waves, modu- lated undamped waves for telegraphic purposes or voice modulated undamped waves as in radio-telephony. Later on it will be shown how straight undamped waves may also be de- tected by modifying the radio- frequency oscillations in the receiving circuit. Effect of Gas in a Detector Tube Under "Tube Construction" in the preceding chapter it was stated that some tubes, called "soft" tubes, contain a small amount of gas. This gas is rarefied, of course, since the vacuum within the tube is still comparatively high, although not as per- fect as it might be made. Electrons are not matter in any shape or form, but gas is most certainly a form of matter. Therefore if there is gas within a tube, the tube space is not absolutely devoid of matter, except for the electrodes, but has matter be- tween the filament, grid and plate. Its action also cannot, therefore, be exactly like a very high vacuum, or "hard," tube. The smallest possible particle of gas is called an "atom." It is too small to be seen but, nevertheless, has weight because it can be acted upon by gravity. Electrons do not have weight because they cannot be acted upon by gravity. Each atom of gas has a central nucleus which carries a positive charge of elec- 72 A B C OF VACUUM TUBES tricity. This nucleus is surrounded by electrons (negative charges) so that, normally, the sum of all the negative charges of the electrons equals the positive charge of the central nucleus. If an electron projected at high velocity from a filament collides with an atom of gas, it may very easily cause one or more electrons to be torn away from the atom. When such a thing occurs, the positive charge of the atom over-balances its remaining negative charges and it acts like a positive charge of electricity. In this condition it is called an "ion." That is, an atom is known as an "ion" after it has lost one or more electrons. It is quite con- ceivable that if there are thousands of electrons projected from the filament per second, all at high velocity, many collisions might take place between them and the gas atoms. Many ions would then be created. Such action is called "ionization by col- lision." Now, under the influence of a positively charged plate, the electrons emitted by the filament and those set free by collision move* toward the plate and are attracted to it at a rate depending upon its potential. The ions are repelled by the plate toward the filament. Suppose that electrons are not projected in sufficient numbers per second from the filament to equal the rate of attraction of the plate. If additional electrons are pro- duced by collision, they may make up the deficiency and cause the plate current to be increased without the increase of filament temperature. Care must be taken, however, to keep the plate potential below the value which causes too large plate current. When too much plate current flows there will be a visible blue glow inside the tube and the plate current will not be appreci- ably affected by the grid potential variations. The result is very erratic action of the tube and a decrease in volume of sound from the telephone receiver. The "soft" tube is more sensitive as a detector than the "hard" tube, but it has its disadvantages. VACUUM TUBE DETECTOR 73 The most marked disadvantage is probably the critical adjust- ment of filament temperature and plate potential necessary to satisfactory operation. Another is the shortened life of the tube caused by the bombardment by the comparatively heavy ions which are driven against it when they are repelled by the plate. Heterodyne Action, or the Production of Beats It has been pointed out that unmodulated (unmodified) un- damped radio frequency oscillations will not produce sound in 1,000- Telephone Current--' Fig. 27 — The principle of heterodyne action. a telephone receiver. If, however, oscillations of a different frequency are generated locally and forced to flow in an antenna circuit there is an interaction between the two frequencies which produces oscillations of a third frequency equal to the numeri- 74 A B C OF VACUUM TUBES cal difference between the other two. The third frequency must then, of course, be lower than either of the other two. This action is called ''heterodyne action" and the oscillations of the third and lower frequency are called "beats." The curves of Fig. 2.J show this graphically. There are, in this case, oscilla- tions induced in the antenna circuit (by a distant transmitter) whose frequency is 100,000 cycles per second and oscillations V Plate Battery Ffl. Battery - Oscillation Generator Filament Rheostat 7~\ Fig. 28 — Schematic circuit for the production of beats. produced by a local oscillation generator whose frequency is 101,000 cycles per second. Both are radio frequencies and neither by itself produces any audible response in the telephone receiver. Now, the local oscillations are forced to flow in the antenna circuit although the latter is not tuned to them. This is because of a strong inducing action of the local generator upon the antenna circuit. The amplitude of the forced oscilla- VACUUM TUBE DETECTOR 75 tions (of 101,000 cycle frequency) in the antenna circuit is not maximum, but that makes no difference. The frequency of the third set of oscillations in the antenna circuit is 1000 cycles per second (within the limits of audible sound) and will cause the average plate current to vary or pulsate 1000 times per second and the telephone receiver diaphragm to vibrate at the same frequency. The sound waves produced are, then,, at the rate of 1000 per second and the same tone is heard as would be if the transmitter at the distant station were a 500 cycle spark set. In this manner the undamped waves are modified by heterodyning at the receiving station and made to produce an audible response in the telephone receiver. Various schematic circuits are illustrated in a following chapter, which show how connections may be made to produce this heterodyne action. The local oscillations may be generated by an entirely separate generator, as in Fig. 28, or the detector circuit may be slightly changed so that it acts as an oscillation generator at the same time that it acts as a detector. CHAPTER IV THE VACUUM TUBE AMPLIFIER General characteristics — Audio frequency amplification — Radio fre- quency amplification — Radio frequency regenerative amplification — Auto- dyne production of beats. General Characteristics Because of the relay action of a tube, a certain amount of amplification takes place even when the tube is functioning as a detector. Amplification may be said to be an inherent property of all vacuum tubes. If a steady potential is applied to the grid which brings the operating point to a position on the straight portion of the characteristic curve, equal variations of grid potential will cause equal changes of plate current. No distortion of plate current is then caused, even with damped oscillations, and its variations are not only in step with the antenna oscillations but its amplitudes are proportional to the amplitudes of antenna oscillations at every instant. See Figs. 29 (a) and (b). If radio-telegraph signals only are received, distortion of the oscillating plate current is not such a serious drawback. But when radio-telephone speech and music are received it is impera- tive that no distortion takes place or the sounds heard may not be accurate reproductions of the sounds at the transmitting sta- tion. They may, in fact, be so greatly distorted that they are extremely difficult to understand or absolutely unintelligible. An ideal amplifier is, then, one in which the antenna current is amplified without distortion regardless of the combination of frequencies involved. 76 VACUUM TUBE AMPLIFIER 77 By this time it has probably become self-evident that the volume of sound produced in a telephone receiver depends upon the amplitudes of the diaphragm vibrations back and forth. y Equal Grid ? Potential Variations Fig. 29 (a) — Amplification of continuous oscillations. These amplitudes in turn depend upon the amplitudes of the audio- frequency plate current variations passing through the receiver magnet-coils. The coils smooth out the variations somewhat, but their amplitudes depend nevertheless upon the amplitudes of the oscillations in the antenna circuit. Because of inherent amplification these audio- frequency current ampli- 78 A B C OF VACUUM TUBES tudes in the plate circuit are usually larger than those in the antenna. They may not, however, be large enough to create the Damped 6 rid Pofenfiaf Variations Fig. 29 (b) — Amplification of damped oscillations. desired amplitudes of sound waves and therefore the volume of sound from the telephone receiver. Amplification must then be increased in some manner. VACUUM TUBE AMPLIFIER 79 Amplification Factor It has been stated that if the filament current and plate po- tential are kept constant, the plate current varies with the grid potential. It is also true that if both filament current and grid potential are kept constant, the plate current varies with the plate potential. There are then two possible ways to vary the plate current when the filament current is constant. But the reason the potential variations due to signals are applied to the grid rather than to the plate is that they have greater effect upon the plate current in the former case than in the latter. There would otherwise be no object in having a grid electrode. The ratio of plate potential variation to grid potential variation re- quired to produce any given change in plate current is called the "voltage amplification factor." For example, if a certain increase in grid potential will produce a certain increase in plate current and it takes an increase of plate potential six times that of grid potential to produce the same increase of plate current, the voltage amplification factor is six. The value of any given vacuum tube as an amplifier depends upon this amplification factor. In general, all other conditions being equal, the amplification factor of a tube depends upon two things. The first is the relation between the distance of the plate from the filament and the distance from the grid to fila- ment. That is, with a given distance between plate and filament, the closer the grid is to the filament the greater this amplifica- tion factor will be. The second is the spacing between the grid wires (or distance between turns). The amplification factor increases with a decrease of spacing and vice versa. Tubes may thus be compared with each other and their relative values as amplifiers roughly judged. With any given tube, the amplification factor also depends 80 A B C OF VACUUM TUBES to some extent upon the plate and grid potentials. It cannot, therefore, be considered as an actual constant. If, however, only the straight portions of characteristic curves are consid- ered the effect of plate and grid potentials upon amplification constant may be ignored. The value of a tube as an amplifier also depends upon the degree of vacuum and the very "hard" tubes are considered far superior to the "soft" tubes for amplification purposes. Now, the slope of the grid-potential, plate-current curve de- pends upon the amplification factor, other things being equal. If this characteristic curve for one tube is steeper than that for another, grid potential variations in the first tube will produce larger plate current variations than will be produced in the second tube by the same grid potential variations. This may be seen by comparing Fig. 30 with Fig. 29 (a). In the case of an amplifier tube it is only the straight portion of any characteris- tic curve which is of interest, since operation on a bend of the curve would result in unsymmetrical variations of plate current. Audio Frequency Amplification If it is desired to amplify the audio- frequency current in the plate circuit of a detector tube, the primary of a small closed core transformer may be connected between the plate and the positive terminal of the plate battery. The secondary of the transformer is then connected into the grid circuit of another tube and the normal potential on the grid of this second tube is so adjusted that its operating point is on the straight portion of its characteristic curve. Usually a certain amount of steady negative potential must be applied to the grid of this amplifier tube to accomplish this result. This may, of course, be done by inserting a grid battery of proper voltage into the grid circuit VACUUM TUBE AMPLIFIER 81 and connecting the negative battery terminal to the grid. Another and better method is to include a portion of the fila- 100 90 80 70 +.-60 c I 50 o 40 30 20 10 v'^/ P/<«fe Potential and Filament Current Constant Opt >rat/ht 7 \ v .___. .___ Po/h'i t. P/afe &///< ent s Norm il PI a te Cut i rent *a / / / / ■*-. / / / t. — , — i ■fc -A/_. _\Z_ '-■ — l<3 ! ^ < 6 -5 -4 - Gr 3 - id P 2 - orent 1 Q +1 +2+3 +4 +5 +6 ial 5 Sr/i/ Pofentia/ ^ > ~~ ^ Fig. 30 — Amplification of continuous oscillations ment rheostat resistance in the grid circuit as shown in Fig. 3 1 . This places a negative potential upon the grid which is equal to the potential difference between the points "X" and "Y." 82 A B C OF VACUUM TUBES The audiofrequency variations of plate current in the detec- tor tube now cause grid potential variations in the amplifier tube which are larger in amplitude than the grid potential vari- Transformer Grid-, Plate To Plate Circuit of DetectorTube u Amplif ier \lub e JL' r Filament ■? %4-*/s Rheostat'' Filament ) Battery'' •=" Plate — Battery -© Telephone. Receiver Fig. 31 — Customary method of placing a normal negative potential on the grid of an amplifier tube. ations applied to the detector tube by the antenna oscillations. These variations of amplifier grid potential will be at die audible frequency rate because radio frequency current vari- ations cannot readily flow in the detector plate circuit due to the high reactance of the transformer primary. Audio- frequency currents will then flow in the plate circuit of the amplifier tube and through the telephone receiver. The receiver diaphragm will vibrate with greater amplitude because the current variations are of magnified amplitude and, as a final result, the sound heard in the telephone receiver is louder. This can easily be verified by plugging a telephone receiver into the jack of the detector circuit and then into the jack of the first stage of an audio- frequency amplifier. If still further increase in audibility (or volume of sound) is required one or more "stages" of amplification may be used in the same manner. Such amplification is referred to as "cascade amplification." Usually two stages of audio frequency ampli- fication (two amplifier tubes in cascade connection) are the VACUUM TUBE AMPLIFIER 83 limit, although if care is taken three stages may sometimes be managed. The signals must, of course, be put through a detector tube and rectified before they are applied to an audio- frequency amplifier. With cascade amplification sufficient current may frequently be secured in the plate circuit of the last tube to operate a relay or a device known as a "loud speaker." If the relay is used, telegraph signals may be sent over a land wire from the radio receiving station to a distant office where an- other relay opens and closes a local sounder circuit. If the loud speaker is used both radio telegraph signals and radio-telephone speech and music may be reproduced with sufficient volume to be heard considerable distances away from the instruments. Radio Frequency Amplification The amplitudes of the grid potential variations in any tube control the audio- frequency variations oi average plate current. These grid potential variations of course depend upon the am- plitudes of the antenna oscillations. If the antenna oscillations are weak, that is, if the signal is weak, the grid potential vari- ations are also weak (of small amplitude) and a detector tube may not be made to function propertly and possibly not at all. This is because the sensitiveness of a detector depends upon the square of the potentials applied to the grid by the signal current. For example, if a certain voltage applied to the grid produces a certain change in plate current, twice the applied voltage will produce four times the change in plate current. It is obvious that the amplitudes of the antenna oscillations might at times be too small to operate the detector tube. In this case there would be no amplification of the very weak signal by means of audio- frequency amplification because the signal can not operate the detector in the first place. 84 A B C OF VACUUM TUBES When signals are very weak it is then of very great advan- tage to amplify them before they are rectified. That is, to am- plify the antenna oscillations until the potential variations are high enough to operate a detector tube to good advantage. To do this it is necessary to amplify radio frequency oscillations before rectification. The circuit shown in Fig. 32 may be referred to. In this circuit there is resistance inserted in the plate circuit of the first 'Antenna Filament Plate Grid, Variable Inductance\ Variable / Capacitance V\ Ampli fier w. Plate Battery 1 -T, Coupling lube 9p. fS -® ®- JSl^c .s^e 1 — vJ?.Q.QQQy si .QOQOib-^ - T — ^nn^p — .AA/ «=C „V\ Tpm^- /\s\ t >nW *~™*"™ vfiJULr* >i— VW H^I 1 lOflOi H + -=■ q Li: r-vW ? t — W + ;*" ■1* ^ > ft *£ 0= J$ Pf 4l I M k ex G ft r Registered Letter CATALOGUE OF GOOD, PRACTICAL BOOKS AUTOMOBILES THE MODERN GASOLINE AUTOMOBILE— ITS DESIGN, CONSTRUC- TION, MAINTENANCE AND REPAIR. By Victor W. Page, M.E. The latest and most complete treatise on the Gasoline Automobile ever issued. 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Cloth, 6x9, 962 pages, 750 illustrations Price $5.00 3 CATALOGUE OF GOOD, PRACTICAL BOOKS THE MODEL T FORD CAR, ITS CONSTRUCTION, OPERATION AND REPAIR, INCLUDING THE FORDSON FARM TRACTOR, F. A. LIGHT- ING AND STARTING SYSTEM, FORD MOTOR TRUCK. By Victor W. Page. This is the most complete and practical instruction book ever published on the Ford car and Fordson tractor. All parts of the Ford Model T car and Fordson tractor are described and illustrated in a comprehensive manner. The construction is fully treated and operating principle made clear to everyone. Complete instructions for driving and repairing are given. To the New Revised Edition matter has been added on the Ford Truck and Tractor Conversion Sets and Genuine Fordson Tractor. All parts are described. All repair processes illustrated and fully explained. "Written so all can understand — no theory, no guesswork. New revised and enlarged Edition just published. 153 illustrations, 410 pages, 2 large folding plates. Price . $2.00 AUTOMOBILE STARTING, LIGHTING AND IGNITION SYSTEMS. By Victor W. Page, M.E. This practical volume has been written with special reference to the requirements of the non-technical reader desiring easily understood, explanatory matter, relating to all types of automobile ignition, starting and lighting systems. It can be understood by anyone, even without electrical knowledge, because elementary electrical principles are considered before any attempt is made to discuss features of the various systems. These basic principles are clearly stated and illustrated with simple diagrams. All the leading systems of starting, lighting and ignition have been described and illustrated with the co-operation of the experts employed by the manufacturers. Wiring diagrams are shown in both technical and non-technical forms. All symbols are fully explained. It is a comprehensive review of modern starting and ignition system practice, and includes a complete exposition of storage battery construction, care and repair. All types of starting motors, generators, magnetos, and all ignition or lighting system units are fully explained. The systems of cars already in use as well as those that are to come are considered. Every person in the automobile business needs this volume. 5Mx7>£. Cloth. 815 pages, 492 illustrations, 3 folding plates. New revised and enlarged edition. Price $3.00 GASOLINE AND KEROSENE CARBURETORS, CONSTRUCTION, IN- STALLATION AND ADJUSTMENT. By Victor W. Page. A new up- to-date Book on Modern Carburetion Practice. This is a simple, comprehensive, and authoritative treatise for practical men ex- plaining all basic principles pertaining to carburetion, showing how liquid fuels are vaporized and turned into gas for operating all types of internal combustion engines in- tended to operate on vapors of gasoline, kerosene, benzol, and alcohol. All leading types of carburetors are described in detail, special attention being given to the forms devised to use the cheaper fuels such as kerosene. Carburetion troubles, fuel system troubles, carburetor repairs and installation, electric primers and economizers, hot spot mani- folds and all modern carburetor developments are considered in a thorough manner. Methods of adjusting all types of carburetors are fully discussed as well as sugges- tions for securing maximum fuel economy and obtaining highest engine power. This book is invaluable to repairmen, students, and motorists, as it includes the most complete exposition on kerosene carburetors ever published. The drawings showing carburetor construction are made from accurate engineering designs and show all parts of late types of carburetors. 213 pages. 89 illustrations. . $2.00 HINTS AND TIPS FOR AUTOMOBILISTS. By Victor W. Page. The book is ideal for the busy man or woman who wants to know about car operation and upkeep because of the economies possible when an automobile is intelligently operated. It contains many money-saving hints and a brief simple exposition of location and remedy of roadside troubles apt to occur under ordinary operating conditions. Price 75 cents CATALOGUE OF GOOD, PRACTICAL BOOKS AUTOMOBILE REPAIRING MADE EASY. By Victor W. Page, M.E. A comprehensive, practical exposition of every phase of modern automobile repairing practice. Outlines every process incidental to motor car restoration. Gives plans for workshop construction, suggestions for equipment, power needed, machinery and tools necessary to carry on the business successfully. Tells how ±o overhaul and repair all parts of all automobiles. Everything is explained so simply that motorists and students can acquire a full working knowledge of automobile repairing. This work starts with the engine, then considers carburetion, ignition, cooling and lubrication systems. The clutch, change-speed gearing and transmission system are considered in detail. Contains instructions for repairing all types of axles, steering gears and other chassis parts. Many tables, short cuts in figuring and rules of practice are given for the mechanic. Explains fully valve and- magneto timing, "tuning" engines, systematic location of trouble, repair of ball and roller bearings, shop kinks, first aid to injured and a multi- tude of subjects of interest to all in the garage and repair business. This book contains special instructions on electric starting, lighting and ignition systems, tire repairing and rebuilding, autogenous welding, brazing and soldering, heat treatment of steel, latest timing practice, eight and twelve-cylinder motors, etc. 5Mx8. Cloth. 1060 pages, 1,000 illustrations, 11 folding plates. Price $4.00 WHAT IS SAID OP THIS BOOK : *' 'Automobile Repairing Made Easy' is the best book on the subject I have ever seen and the only book I ever saw that is of any value in a garage." — Fred Jeffrey, Martins- burg, Neb. "I wish to thank you for sending me a copy of 'Automobile Repairing Made Easy/ I do not think it could be excelled." — S. W. Gisriel, Director of Instruction, Y. M. C. A., Philadelphia, Pa. QUESTIONS AND ANSWERS RELATING TO MODERN AUTOMOBILE CONSTRUCTION, DRIVING AND REPAIR. By Victor W. Page, M.E. A practical self-instructor for students, mechanics and motorists, consisting of thirty- seven lessons in the form of questions and answers, written with special reference to the requirements of the non-technical reader desiring easily understood, explanatory matter relating to all branches of automobiling. The subject-matter is absolutely correct and explained in simple language. If you can't answer all of the following questions, you need this work. The answers to these and nearly 2000 more are to be found in its pages. Give the name of all important parts of an automobile and describe their functions? Describe action of latest types of kerosene carburetors? What is the difference between a "double" ignition system and a "dual" ignition system? Name parts of an induction coil? How are valves timed? What is an electric motor starter and how does it work? What are advantages of worm drive gearing? Name all important types of ball and roller bearings? What is a " three- quarter" floating axle? What is a two-speed axle? What is the Vulcan electric gear shift? Name the causes of lost power in automobiles? Describe all noises due to deranged mechanism and give causes? How can you adjust a carburetor by the color of the exhaust gases? What causes "popping" in the carburetor? What tools and supplies are needed to equip a car? How do you drive various makes of cars? What is a differential lock and where is it used? Name different systems of wire wheel construction, etc., etc. A popular work at a popular price. 5^x7^. Cloth. 701 pages, 387 illustrations, 3 folding plates. New revised edition. Price $2.50 WHAT IS SAID OP THIS BOOK: "If you own a car — get this book." — The Glassworker. "Mr. Page has the faculty of making difficult subjects plain and understandable." — Bristol Press. "We can name no writer better qualified to prepare a book of instruction on auto- mobiles than Mr. Victor W. Page." — Scientific American. "The best automobile catechism that has appeared." — Automobile Topics. " There are few men, even with long experience, who will not find tbis book useful. Great pains have been taken to make it accurate. Special recommendation must be given to the illustrations, which have been made specially for the work. Such ex- cellent books as this greatly assist in fully understanding your automobile." — En- gineering News. CATALOGUE OF GOOD, PRACTICAL BOOKS HOW TO RUN AN AUTOMOBILE. By Victor W. Page. This treatise gives concise instructions for starting and running all makes of gasoline automobiles, how to care for them, and gives distinctive features of control. De- scribes every step for shifting gears, controlling engine, etc. Among the chapters contained are: I. Automobile Parts and Their Functions. II. General Starting and Driving Instructions. III. Control Systems — Care of Automobiles. Thoroughly illustrated. 178 pages. 72 illustrations. Price $1.50 THE AUTOMOBILISTS POCKET COMPANION AND EXPENSE RECORD* By Victor W. Page. This book is not only valuable as a convenient cost record, but contains much in- formation of value to motorists. Includes a condensed digest of auto laws of all States, a lubrication schedule, hints for care of storage battery, and care of tires, location of road troubles, anti-freezing solutions, horse-power table, driving hints and many useful tables and recipes of interest to all motorists. Not a technical book in any sense of the word, just a collection of practical facts in simple language for the every-day motorist. Convenient pocket size. Price $1.50 AUTOMOBILE WELDING WITH THE OXY-ACETYLENE FLAME. By M. Keith Dunham. Explains in a simple manner apparatus to be used, its care, and how to construct necessary shop equipment. Proceeds then to the actual welding of all automobile parts, in a manner understandable by everyone. Gives principles never to be for- gotten. This book is of utmost value, since the perplexing problems arising when metal is heated to a melting point are fully explained and the proper methods to overcome them shown. 167 pages. Fully illustrated. Price $1.50 UTOMOBILE, AVIATION AND MOTORCYCLE CHARTS AVIATION CHART— LOCATION OF AIRPLANE POWER PLANT TROUBLES MADE EASY. By Major Victor W. Page, A.S., S.C.U.S.R. A large chart outlining all parts of a typical airplane power plant, showing the points where trouble is apt to occur and suggesting remedies for the common defects. In- tended especially for aviators and aviation mechanics on school and field duty. Price 35 cents CHART. GASOLINE ENGINE TROUBLES MADE EASY— A CHART SHOW- ING SECTIONAL VIEW OF GASOLINE ENGINE. Compiled by Victor W. Page, M.E. It shows clearly all parts of a typical four-cylinder gasoline engine of the four-cycle type. It outlines distinctly all parts liable to give trouble and also details the de- rangements apt to interfere with smooth engine operation. Valuable to students, motorists, mechanics, repairmen, garagemen, automobile sales- men, chauffeurs, motorboat owners, motor-truck and tractor drivers, aviators, motor- cyclists, and all others who have to do with gasoline power plants. It simplifies location of all engine troubles, and while it will prove invaluable to the novice, it can be used to advantage by the more expert. It should be on the walls of every public and private garage, automobile repair shop, clubhouse or school. It can be carried in the automobile or pocket with ease, and will insure against loss of time when engine trouble manifests itself. This sectional view of engine is a complete review of all motor troubles. It is prepared by a practical motorist for all who motor. More information for the money than ever before offered. No details omitted. Size 25x38 inehes. Securely mailed on receipt of 35 cents CATALOGUE OF GOOD, PRACTICAL BOOKS CHART. LOCATION OF FORD ENGINE TROUBLES MADE EASY. Com- piled by Victor W. Page, M.E. This shows clear sectional views depicting all portions of the Ford power plant and auxiliary groups. It outlines clearly all parts of the engine, fuel supply system, igni- tion group and cooling system, that are apt to give trouble, detailing all derangements that are liable to make an engine lose power, start hard or work irregularly. This chart is valuable to students, owners, and drivers, as it simplifies location of all engine faults. Of great advantage as an instructor for the novice, it can be used equally well by the more expert as a work of reference and review. It can be carried in the tool- box or pocket with ease and will save its cost in labor eliminated the first time engine trouble manifests itself. Prepared with special reference to the average man's needs and is a practical review of all motor troubles because it is based on the actual ex- perience of an automobile engineer-mechanic with the mechanism the chart describes. It enables the non-technical owner or operator of a Ford car to locate engine de- rangements by systematic search, guided by easily recognized symptoms instead of by guesswork. It makes the average owner independent of the roadside repair shop when touring. Must be seen to be appreciated. Size 25x38 inches. Printed on heavy bond paper. Price 35 cents CHART. LUBRICATION OF THE MOTOR CAR CHASSIS. Compiled by Victor W. Page, M.E. This chart presents the plan view of a typical six-cylinder chassis of standard design and all parts are clearly indicated that demand oil, also the frequency with which they must be lubricated and the kind of oil to use. A practical chart for all interested in motor-car maintenance. Size 24x38 inches. Price 35 cents CHART. LOCATION OF CARBURETION TROUBLES MADE EASY. Com- piled by Victor W. Page, M.E. This chart shows all parts of a typical pressure feed fuel supply system and gives causes of trouble, how to locate defects and means of remedying them. Size 24x38 inches. Price 35 cents CHART. LOCATION OF IGNITION SYSTEM TROUBLES MADE EASY. Compiled by Victor W. Page, M.E. In this diagram all parts of a typical double ignition system using battery and magneto current are shown, and suggestions are given for readily finding ignition troubles and eliminating them when found. Size 24x38 inches. Price 35 cents CHART. LOCATION OF COOLING AND LUBRICATION SYSTEM FAULTS. Compiled by Victor W. Page, M.E. This composite diarijram shows a typical automobile power plant using pump circulated water-cooling system and the most popular lubrication method. Gives suggestions for curing all overhearing and loss of power faults due to faulty action of the oiling or cooling group. Size 24x38 inches. Price 35 cents CHART. LOCATION OF STARTING AND LIGHTING SYSTEM FAULTS. The most complete chart yet devised, showing all parts of the modern automobile starting, fighting and ignition systems, giving instructions for systematic location of all faults in wiring, lamps, motor or generator, switches and all other units. Invalu- able to motorists, chauffeurs and repairmen. Size 24x38 inches. Price . 35 cents CHART. MOTORCYCLE TROUBLES MADE EASY. Compiled by Victor W. Page, M.E. A chart showing sectional view of a single-cylinder gasoline engine. This chart simplifies location of all power-plant troubles. A single-cylinder motor is shown for simplicity. It outlines distinctly all parts liable to give trouble and also details the derangements apt to interfere with smooth engine operation. This chart will prove of value to all who have to do with the operation, repair or sale of motorcycles. No details omitted. Size 30x20 inches. Price 35 cents CATALOGUE OF GOOD, PRACTICAL BOOKS AVIATION A B C OF AVIATION. By Major Victor W. Page\ This book describes the basic principles of aviation, tells how a balloon or dirigible is made and why it floats in the air. Describes how an airplane flies. It shows in detail the different parts of an airplane, what they are and what they do. Describes all types of airplanes and how they differ in construction; as well as detailing the advantages and disadvantages of different types of aircraft. It includes a complete dictionary of aviation terms and clear drawings of leading airplanes. The reader will find simple instructions for unpacking, setting up, and rigging airplanes. A full description of airplane control principles is given and methods of flying are dis- cussed at length. This book answers every question one can ask about modern aircraft, their con- struction and operation. A self-educator on aviation without an equal. 274 pages. 130 specially made illustrations with 7 plates. Price $2.50 AVIATION ENGINES— DESIGN; CONSTRUCTION; REPAIR. By Major Victor W. Page, A.S., S.C.U.S.R. This treatise, written by a recognized authority on all of the practical aspects of internal combustion engine construction, maintenance, and repair, fills the need as no other book does. The matter is logically arranged; all descriptive matter is simply expressed and copiously illustrated, so that anyone can understand airplane engine operation and repair even if without previous mechanical training. This work is invaluable for anyone desiring to become an aviator or aviation mechanic. The latest rotary types, such as the Gnome Monosoupape, and LeRhone, are fully explained, as well as the recently developed Vee and radial types. The subjects of carburetion, ignition, cooling, and lubrication also are covered in a thorough manner. The chapters on repair and maintenance are distinctive and found in no other book on this subject. Not a technical book, but a practical, easily understood work of reference for all interested in aeronautical science. 589 pages. 253 illustrations. Price, net $3.00 GLOSSARY OF AVIATION TERMS — ENGLISH-FRENCH; FRENCH- ENGLISH. By Major Victor W. Page, A.S., S.C.U.S.R., and Lieut. Paul Montariol, of the French Flying Corps. A complete glossary of practically all terms used in aviation, having lists in both French and English with equivalents in either language. Price, net . . $1.00 APPLIED AERODYNAMICS. By G. P. Thompson. This is a scientific and mathematical treatise that has a special appeal to the student and engineer who are seeking exact information on the aerodynamics of heavier-than- air craft and data on airplane design testing. This book gives an up-to-date presen- tation of the existing state of Aeronautical Science. In addition to a very full diL cussion of the qualities which determine the speed and rate of climb of an aeroplane and the method by which they can be calculated, special attention is paid to stability — a problem now fairly well understood, and to controllability — our knowledge of which is at present in a much more elementary state. Attention is directed to the numerous directions in which further information is required, especially in the form of full-scale experiments. 312 pages (7 x 10). Illustrated with over 142 Diagrams and Graphic Charts. Price $12.50 AVIATION CHART— LOCATION OF AIRPLANE POWER PLANT TROUBLES MADE EASY. By Major Victor W. Page, A.S., S.C.U.S.R. A large chart outlining all parts of a typical airplane power plant, showing the points where trouble is apt to occur and suggesting remedies for the common defects. In- tended especially for aviators and aviation mechanics on school and field duty. Price 35 cents 8 CATALOGUE OF GOOD, PRACTICAL BOOKS 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 conies along ; it 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 formulae for all kinds of solders and fluxes have been added. Illustrated. . 35 cents SOLDERING AND BRAZING. By Raymond Francis Yates. This treatise gives all the necessary "kinks" that will enable one to accomplish suc- cessful soldering. If a mechanic has not succeeded in his soldering, this book may tell him just what he needs to produce good work — something that he may hereto- fore have forgotten. Price 75 cents CHARTS 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. All the machinery and devices fitted in a modern Submarine Boat are shown 35 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 35 cent* 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 35 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 35 cents STEEL HOPPER BOTTOM COAL CAR. A chart showing the anatomy of a steel Hopper Bottom Coal Car, having every part of the car numbered and its proper name given in a reference list 35 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 puU 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 of 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 14x28 inches — showing in isometric perspective the mechanisms be- longing in a modern boiler room. 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 35 centi 9 CATALOGUE OF GOOD, PRACTICAL BOOKS CHEMISTRY HOW TO MAKE AND USE A SMALL CHEMICAL LABORATORY. By Raymond Francis Yates. The treatise covers all of the essentials of elementary chemistry. The law ©f definite proportions, solutions, crystalloids, colloids, electrolysis, etc., are explained. The second part of the book is devoted to chemical and electro-chemical experiments. Only those experiments that will tend to broaden the reader's knowledge of chemistry in general have been chosen. Price 75 cents CONCRETE JUST PUBLISHED— CONCRETE WORKERS' REFERENCE BOOKS. A SERIES OF POPULAR HANDBOOKS FOR CONCRETE USERS. Prepared by A. A. Houghton Each 75 cents The author, in preparing this Series, has not only treated on the usual types of construction, but explains and illustrates molds and systems that are not patented, but which are equal in value and often superior to those restricted by patents. These molds are very easily and cheaply constructed and embody simplicity, rapidity of operation, and the most successful results in the molded concrete. Each of these Twelve books is fully illustrated, and the subjects are exhaustively treated in plain English. CONCRETE WALL FORMS. By A. A. Houghton. A new automatic wall clamp is illustrated with working drawings. Other types ol wall forms, clamps, separators, etc., are also illustrated and explained. (No. 1 of Series) 75 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. (No. 2 of Series) . . 75 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. (No. 3 of Series) 75 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. A number of ornamental designs of chimney construction with molds are shown in this valuable treatise. (No. 4 of Series.) 75 cents MOLDING AND CURING ORNAMENTAL CONCRETE. By A. A. Houghton. The proper proportions of cement and aggregates for various finishes, also the method 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 (No. 5 of Series.) 75 cents CONCRETE MONUMENTS, MAUSOLEUMS^AND BURIAL VAULTS. By A. A. Houghton. The molding of concrete monuments to imitate the most expensive cut stone is ex- plained in this treatise, with working drawings of easily built molds. Cutting in- scriptions and designs are also fully treated. (No. 6 of Series.) ... 75 cents 10 CATALOGUE OF GOOD, PRACTICAL BOOKS MOLDING CONCRETE BATHTUBS, AQUARIUMS AND NATATORIUMS. By A. A. Houghton. Simple molds and instruction are given for molding many styles of concrete oath tubs, swimming-pools, etc. These molds are easily built and permit rapid and successful work. (No. 7 of Series.) 75 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 de» tailed instructions for building. (No. 8 of Series.) 75 cents CONSTRUCTING CONCRETE PORCHES. By A. A. Houghton. A number of designs with working drawings of molds are fully explained so anyone can easily construct different styles of ornamental concrete porches without the pur- chase of expensive molds. (No. 9 of Series.) 75 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, jardinieres, etc., are fully illustrated and explained, so the worker can easily construct and operate same. (No. 10 of Series.) 75 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 gar- dens, is fully illustrated and described. (No. 11 of Series) 75 cents 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 $3.00 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 tem- plates 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 FOR THE FARM AND IN THE SHOP. By H. Colin Campbell, C.E., E.M. A new book illustrating and describing in plain, simple language many of the numerous applications of concrete within.the range of the home worker. Among the subjects treated are: Principles of reinforcing ; methods of protecting concrete so as to insure proper harden- ing; home-made mixers; mixing by hand and machine; form construction, described and illustrated by drawings and photographs; construction of concrete walls and fences; concrete fence posts; concrete gate posts; corner posts; clothes line posts; grape arbor posts; tanks; troughs; cisterns; hog wallows; feeding floors and barn- yard pavements ; foundations ; well curbs and platforms ; indoor floors ; sidewalks ; steps ; concrete hotbeds and cold frames ; concrete slab roofs ; walls for buildings ; repairing leaks in tanks and cisterns, etc., etc. A number of convenient and practical tables for estimating quantities, and some practical examples, are also given. (5 x 7). 149 pages, 51 illustrations. Price $1.00 II CATALOGUE OF GOOD, PRACTICAL BOOKS 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, 430 pages, 126 illustrations. Price $3.00 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 Dampproofing Structures and Structural Materials. Price .... 75 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 handbook of reference containing definitions in about 5000 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. Nearly 800 pages. Nearly 500 illustrations. New Revised and Enlarged Edition. Price $5.00 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 pres- 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 of 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. 6th Edition. 400 pages, 523 illustrations. Price $3.50 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- {wesses, Devices and Mechanical Combinations for Punching, Cutting, Bending, Form- ng, Piercing, Drawing, Compressing and Assembling Sheet-Metal Parts, and also Arti- cles of other Materials in Machine Tools. 3rd Edition. 483 pages, 702 illustrations. Price $4.50 I? CATALOGUE OF GOoO, PRACTICAL BOOKS DRAWING— SKETCHING PAPER PRACTICAL PERSPECTIVE. By Richards and Colvin. Shows just how to make all kinds of mechanical drawings in the only practical per- spective 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. 4th Edition. 75 cents 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 arrange- ment 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. There is included a self-explanatory chart which gives all information necessary for the thorough understanding of perspective. This chart alone is worth many times over the price of the book. 2d Revised and enlarged Edition $3.00 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 draf tsman 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 neces- sary 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 fly-wheels, have been treated in such a way as to make possible the use of the work as a text-book for a continuous course of study. 333 pages, 218 engravings. Price. . . . $2.50 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, 6x9 inches, 40 cents. Pads of 40 sheets, 9x12 inches, 75 cents; 40 sheets, 12x18, Price $1.50 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. 22nd Edition. 196 pages. Price $1.50 13 CATALOGUE OF GOOD, PRACTICAL BOOKS 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. 5th Edition . .35 cents CONSTRUCTION OF A TRANSATLANTIC WIRELESS RECEIVING SET. By L. G. Pacent and T. S. Curtis. A work for the Radio student who desires to construct and operate apparatus that will permit of the reception of messages from the large stations in Europe with an aerial of amateur proportions. 36 pages. 23 illustrations, cloth. Price . 35 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 Punching. 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, cloth, $1.00 DESIGN DATA FOR RADIO TRANSMITTERS AND RECEIVERS. By Milton B. Sleeper. Far from being a collection of formulas, Design Data takes up in proper sequence the problems encountered in planning all types of receiving sets for short, medium and long wave work, and spark coil, transformer and vacuum tube transmitters operating on 200 meters. Tables have been worked out so that values can be found without the use of mathematics. Radio experimenters will find here information which will enable them to have the most modern and efficient equipment. Price . . 75 cents DYNAMOS AND ELECTRIC MOTORS AND ALL ABOUT THEM. By Edward Trevert. This volume gives practical directions for building a two H. P. Dynamo of the Edison type capable of lighting about fifty mazda lamps of the 20-watt size. In addition, it gives directions for building two small electric motors suitable for running sewing machines. The concluding chapter describes the construction of a simple bichromate battery adapted for running electric motors. 96 pages. Fully illustrated with detail drawings. Cloth. Price $1.00 ELECTRIC BELLS. By M.- B. Sleeper. A complete treatise for the practical worker in installing, operating, and testing bell circuits, burglar alarms, thermostats, and other apparatus used with electric bells. Both the electrician and the experimenter will find in this book new material which is essential in their work. Tools, bells, batteries, unusual circuits, burglar alarms, annunciators, systems, thermostats, circuit breakers, time alarms, and other apparatus used in bell circuits are described from the standpoints of their applica- tion, construction, and repair. The detailed instructions for building the apparatus will appeal to the experimenter particularly. The practical worker will find the chapters on Wiring Calculation of Wire Sizes and Magnet Windings, Upkeep of Systems and the Location of Faults of the greatest value in their work. 124 pages. Fully illustrated. Price 75 cents 14 CATALOGUE OF GOOD, PRACTICAL BOOKS EXPERIMENTAL HIGH FREQUENCY APPARATUS — HOW TO MAKE AND USE IT. By Thomas Stanley Curtis. This book tells you how to build simple high frequency coils for experimental purpose in the home, school laboratory, or on the small lecture platform. The book is really a supplement to the same author's "High Frequency Apparatus." The experimental side only is covered in this volume, which is intended for those who want to build small coils giving up to an eighteen-inch spark. The book contains valuable in- formation for the physics or the manual training teacher who is on the lookout for interesting projects for his boys to build or experiment with. The apparatus is simple, cheap and perfectly safe, and with it some truly startling experiments may be performed. Among the contents are: Induction Con Outfits Operated on Battery Current. Kicking Coil Apparatus. One-Half Kilowatt Transformer Outfit. Parts and Materials, etc., etc. 69 pages. Illustrated. Price 50 cents HIGH FREQUENCY APPARATUS, ITS CONSTRUCTION AND PRACTICAL APPLICATION. By Thomas Stanley Curtis. The most comprehensive and thorough work on this interesting subject ever produced. The book is essentially practical in its treatment and it constitutes an accurate record of the researches of its author over a period of several years, during which time dozens of coils were built and experimented with. The work has been divided into six basic parts. The first two chapters tell the uninitiated reader what the high frequency current is, what it is used for, and how it is produced. The second section, comprising four chapters, describes in detail the principles of the transformer, condenser, spark gap, and oscillation transformer, and covers the main points in the design and con- struction of these devices as applied to the work in hand. The third section covers the construction of small high frequency outfits designed for experimental work in the home laboratory or in the classroom. The fourth section is devoted to electro- therapeutic and X-Ray apparatus. The fifth describes apparatus for the cultivation of plants and vegetables. The sixth section is devoted to a comprehensive discussion of apparatus of large size for use upon the stage in spectacular productions. The closing chapter, giving the current prices of the parts and materials required for the construction of the apparatus described, is included with a view to expediting the purchase of the necessary goods. The Second Edition includes much new matter along the line of home-made therapeutic outfits for physicians' use. The matter on electro plant culture has also been elaborated upon. Second Revised and Enlarged Edition. 266 pages. New second edition. Fully illustrated. 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 employ- ment in house wiring clearly illustrated. Some simple facts about testing are included in connection with the wiring. Molding and conduit work are given careful considera- tion; 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 develop- ment 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. 3rd edition, revised and enlarged. 315 pages; 137 illustrations. Price $2.50 IS CATALOGUE OF GOOD, PRACTICAL BOOKS 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 want- ed to give the much needed information in a plain, practical manner, with illustrations to make easy the carrying out of the work. 20th Edition. 210 pages, 77 illustrations. Price $1.50 ELECTRICIANS* HANDY BOOK. By Prof. T. O'Conor Sloane. This work 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, Alter- nating 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, Electric-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- six chapters, 600 engravings. New 5th Edition, Revised and Enlarged. Price $4.00 ELECTRICITY SIMPLIFIED. By Prof. T. Q'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 metal, 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. 15th Revised Edition. 218 pages. Illustrated. Price . . $1.50 EXPERIMENTAL WIRELESS STATIONS. By P. E. Edelman. The theory, design, construction and operation is fully treated including Wireless Telephony, Vacuum Tube, and quenched spark systems. The new enlarged edition is just issued and is strictly up to date, correct and complete. This book tells how to make apparatus to not only hear all telephoned and telegraphed radio mes- sages, but also how to make simple equipment that works for transmission over rea- sonably long distances. Then there is a host of new information included. The first and only book to give you all the recent important radio improvements, some of which have never before been published. This volume anticipates every need of the reader who wants the gist of the art, its principles, simplified calculations, appara- tus dimensions, and understandable directions for efficient operation. Vacuum tube circuits; amplifiers; long-distance sets; loop, coil, and underground receivers; tables of wave-lengths, capacity, inductance; such are a few of the sub- jects presented in detail that satisfies. It is independent and one of the few that describe all modern systems. Endorsed by foremost instructors for its clear accuracy, preferred by leading amateurs for its dependable designs. The new experimental Wireless Stations is sure to be most satisfactory for your purposes. 27 chapters, 392 pages. 167 illustra- tions. Price $3.00 RADIO TIME SIGNAL RECEIVER. By Austin C. Lescarboura. This new book, "A Radio Time Signal Receiver," tells you how to build a simple outfit designed expressly for the beginner. You can build the outfits in your own workshop and install them for jewelers either on a one-payment or a rental basis. The apparatus is of such simple design that it may be made by the average amateur mechanic possessing a few ordinary tools. 42 pages. Paper. Price . . 35 cents 16 CATALOGUE OF GOOD, PRACTICAL BOOKS 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 he done, and the method of doing it. The book can be conveniently carried in the pocket. It is intended for the Electrician, Helps, 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 informa- tion 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 or 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. 208 pages. 4th Edition, revised and enlarged. 160 illustrations. Flexible cloth. Price $1.00 HOW TO BECOME A SUCCESSFUL ELECTRICIAN. By Prof. T. 0'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 requirement, of the successful electrician are pointed out and fully explained. Every young en- gineer 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 dis- couraged at the very outstart 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 inter- esting from cover to cover. 19th Revised Edition, just issued. 205 pages. Illus- trated. Price $1.50 RADIO HOOK-UPS. By Milton B. Sleeper. In this book the best circuits for different instruments and various purposes have been carefully selected and grouped together. All the best circuits for damped and un- damped wave receiving sets, buzzer,§spark coil and transformer sending equipment, as well as vacuum tube telegraph and telephone transmitters, wavemeters, vacuum tube measuring instruments, audibility meters, etc., are shown in this book. . 75 cents STANDARD ELECTRICAL DICTIONARY. By T. O'Ccnor Sloane. An indispensable work to all interested in electrical science. Suitable alike for the student and professional. A practical handbook 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 en- tirely 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 con- venient. 800 pages. Nearly 500 illustrations. New Revised and Enlarged Edition. Price . , , . , $5.00 J7 CATALOGUE OF GOOD, PRACTICAL BOOKS ^1 I H ■■■III! ■M^MIIIIIII I M _|. „_ ■IWIBW ■■■! Illll III1IIIIW ■■ I ■ I "^"^^ STORAGE BATTERIES SIMPLIFIED. By Victor W. Page, M.S.A.E. A complete treatise on storage battery operating principles, repairs and applications. The greatly increasing application of storage batteries in modern engineering and mechanical work has created a demand for a book that will consider this subject completely and exclusively. This is the most thorough and authoritative treatise ever published on this subject. It is written in easily understandable, non-technical language so that anyone may grasp the basic principles of storage battery action as well as their practical industrial applications. All electric and gasoline automobiles use storage batteries. Every automobile repairman, dealer or salesman should have a good knowledge of maintenance and repair of these important elements of the motor car mechanism. This book not only tells how to charge, care for and rebuild storage batteries but also outlines all the industrial uses. Learn how they, run street cars, locomotives and factory trucks. Get an understanding of the important functions they perform in submarine boats, isolated lighting plants, railway switch and signal systems, marine applications, etc. This book tells how they are used in central station standby service, for starting automobile motors and in ignition systems. Every practical use of the modern storage battery is outlined in this treatise. 208 pages. Fully illus- trated. Price $2.00 TELEPHONE CONSTRUCTION, INSTALLATION, WIRING, OPERATION AND MAINTENANCE. By W. H. Radcliffe and H. G. Cushinq. This book is intended for the amateur, the wireman, or the engineer who desires to establish a means of telephonic communication between the rooms of his home, office, or shop. It deals only with such things as may be of use to him rather than with theories. 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 thor- oughly 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 Instru- ments; Inspection and Maintenance of Telephone Instruments; Telephone Line Wiring; Testing Telephone Line Wires and Cables ; Wiring and Operation of Special Telephone Systems, etc. 2nd Edition, revised and enlarged. 223 pages. 154 illustrations $1.50 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 Telephone, How Sounds Are Changed into Electric Waves — Wireless Telephones, The Apparatus — Summary. 154 pages. 156 engravings. Price $1.50 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 informa- tion you need. Directions apply equally to a shop. Fourth edition , , 35 cents 18 CATALOGUE OF GOOD, PRACTICAL BOOKS ELECTROPLATING THE MODERN ELECTROPLATER. By Kenneth M. Coggeshall. This is one of the most complete and practical books on electroplating and allied processes that has been published as a text for the student or professional plater. It is written in simple language and explains all details of electroplating in a concise yet complete manner. It starts at the beginning and gives an elementary outline of electricity and chemistry as relates to plating, then considers shop layout and equipment and gives all the necessary information to do reliable and profitable electro- plating in a modern commercial manner. Full instructions are given for the prepara- tion and finishing of the work and formulae and complete directions are included for making all kinds of plating solutions, many of these having been trade secrets until published in this instruction manual. Anyone interested in practical plating and metal finishing will find this book a valuable guide and complete manual of the art. Cloth. 142 illustrations. 276 pages. Price $3.00 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-six 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 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. 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. 384 pages. 219 illustrations. Price $5.00 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 ar- rangement 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. 5th Edition. Nearly 350 pages, fully illustrated. Price. . . . $1.50 19 CATALOGUE OF GOOD, PRACTICAL BOOKS GAS AND OIL ENGINES 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. This book abounds with hints and helps for the farm and suggestions for the home and housewife. There is so much of value in this book that it is impossible to ade- quately describe it in such small space. Suffice to say that it is the kind of a book every farmer will appreciate and every farm home ought to have. 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 home- made 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. All money-making farms utilize power. Learn how to utilize power by reading the pages of this book. It is an aid to the result getter, invaluable to the up-to-date farmer, student, blacksmith, implement dealer and, in fact, all who can apply practical knowledge of stationary gasoline engines or gas tractors to advan- tage. 530 pages. Nearly 180 engravings. Price $3.00 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 makeshifts. 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. 275 pages. 152 specially made engravings. Price $2.00 GAS, GASOLINE, AND OIL ENGINES. By Gardner D. Hiscox. Just issued, 23d 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 are 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. 640 pages. 435 engrav- ings. Folding plates. Price $3.00 20 CATALOGUE OF GOOD, PRACTICAL BOOKS GAS ENGINES AND te PRODUCER-GAS PLANTS. By R. E. Mathot, M.E. This is a practical treatise, setting forth the principles of gas engine and producer design, the selection and installation of an engine, conditions of perfect operation, producer-gas engines and their possibilities ; the care of gas engines and producer-gas plants, with a chapter on volatile hydrocarbon and oil engines. A practical guide for the gas engine designer, user and engineer in the construction, selection, purchase, in- stallation, operation and maintenance of gas engines. Every part of the gas engine is de- scribed in detail, tersely, clearly and with a thorough understanding of the requirements of the mechanic. Recognizing the need of a volume that would assist the gas engine user in understanding the motor upon which he depends for power, the author has discussed the subject without the help of any mathematics. Helpful suggestions as to the purchase of an engine, its installation, care and operation, form a most valuable feature of the book. 6x9inches. Cloth. 314 pages. 152 illustrations. Price.. $3 .00 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 dimen- sioned 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 $3.00 HOW TO RUN AND INSTALL GASOLINE ENGINES. By C. Von Culin. Eevised and enlarged edition just issued. The object of this little book is to furnish a pocket instructor for the beginner, the busy man who uses an engine for pleasure or profit, but who does not have the time or inclination for a technical book, but simply to thoroughly understand how to properly operate, install and care for his own engine. The index refers to each trouble, remedy, and subject alphabetically. Being a quick reference to find the cause, remedy and prevention for troubles, and to become an expert with his own engine. Pocket size. Paper binding. Price , , 25 cents GEARING AND CAMS BEVEL GEAR TABLES. By D. Ag. Engstrom. A book that will at once commend itself to mechanics and draftsmen. Does away with all the trigonometry and fancy figuring on bevel gears, and makes it easy for any- one 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 any- thing in the bevel-gear line. 3d Edition. 66 pages $1.50 CHANGE GEAR DEVICES. By Oscar E. Perrigo. A practical book for every designer, draftsman, and mechanic interested in the inven- tion and development of the devices for feed changes on the different machines requir- ing 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 usu- ally 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. 3rd Edition. 101 pages $1.50 DRAFTING OF CAMS. By Louis Rottillion. 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. 3d Edition, ,,,......., 35 centf 21 CATALOGUE OF GOOD, PRACTICA L BOOKS Mi 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, recipro- cating and air-lift pumps. With 300 figures and diagrams and 36 practical tables. All who are interested in water-works development will find this book a useful ono, 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- ing Water Suface 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 Reinforcement; 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; Dredges; Conduits and Pipe Lines; Marine Hydraulics; Tidal and Sea Wave Power, etc. 320 pages. Price $4.50 ICE AND REFRIGERATION POCKETBOOK 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 con- dition required in the installment and operation of a refrigerating plant. New edition just published. Price $2.00 INVENTIONS— PATENTS INVENTORS' 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 Con- tracts. State Laws Concerning Patent Rights. 1900 Census of the United States by Counts of Over 10,000 Population. New revised and enlarged edition. 144 pages. Illustrated. Price. , , .- - ,..,,,,« $1.50 33 CATALOGUE OF GOOD, PRACTICAL BOOKS 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 appear- ance when finished. The book will be found of the greatest value to Campers, Yachts- men, 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 ana Bends. Terms Used in Handling Rope. Seizing Rope. 3. Ties and Hitches. 4. Noose, Loops and Mooring Knots. 5. Shortenings, Grommets and Salvages. 6. Lashings, Seizings and Splices. 7. Fancy Knots and Rope Work. 104 pages. 154 original engravings. Price $1.00 LATHE WORK LATHE DESIGN, CONSTRUCTION, AND OPERATION, WITH PRACTICAL EXAMPLES OF LATHE WORK. By Oscar E. Perrigo. A new revised edition, 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 now to convey this knowledge to others. It is strictly up-to-date in its descriptions and illustrations. Lathe history and the relations of the lathe to manu- facturing 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. In addi- tion to the complete exposition on construction and design, much practical matter on lathe installation, care and operation has been incorporated in the enlarged 1915 edi- tion. All kinds of lathe attachments for drilling, milling, etc., are described and complete instructions are given to enable the novice machinist to grasp the art of lathe operation as well as the principles involved in design. A number of difficult machining operations are described at length and illustrated. The new edition has nearly 500 pages and 350 illustrations. Price . , $3.00 LATHE WORK FOR BEGINNERS. By Raymond Francis Yates. A simple, straightforward text-book for those desiring to learn the operation of a wood-turning or metal-turning lathe. The first chapter tells how to choose a lathe and all of the standard types on the market are described. Simple and more advanced lathe work is thoroughly covered and the operation of all lathe attachments such as millers, grinders, polishers, etc., is described. The treatment starts from the very bottom and leads the reader through to a point where he will be able to handle the larger commercial machines with very little instruction. The last chapter of the book is devoted to things to make on the lathe and includes a model rapid-fire naval gun. This is the only book published in this country that treats lathe work from the standpoint of the amateur mechanic. 162 illustrations. About 250 pages, 12mo. Price $2.00 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. Fifth edition. Price ....,.,,, 35 cents 23 CATALOGUE OF GOOD, PRACTICAL BOOKS 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 ex- pected 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 everyone. Third edition. Revised and Enlarged. 394 pages. New Edition. Price . . . $3.00 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 instruc- tors and examiners on nearly every railroad in the United States. 28th Edition. 411 pages, fully illustrated with colored plates and diagrams. 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. Presentation of this important subject is systematic and progressive. The ar- rangement 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 $1.50 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. 158 pages. Price $1.50 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, Slice Valves, Piston Valves, Setting Piston Valves, Joy-Allen Valve Gear, Walschaert Valve Gear, Gooch Valve Gear, Alfree- Hubbell Valve Gear, etc., etc. 3rd Edition, 101 »ages. Fully illustrated. Price 75 cents 24 CATALOGUE OF GOOD, PRACTICAL BOOKS 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. Including the recent Locomotive Boiler Inspection Laws and Examination Questions with their answers for Government Inspectors. 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 Calking; 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 informa- tion that you wouldn't be without. 451 pages, 334 illustrations, five large folding plates. Price $3.50 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 have never thought about, and you will find that they are all treated with the very best methods of repahr. Walschaert Locomotive Valve Gear Troubles, Electric Headlight Troubles, as well as Questions and Answers on the Air Brake are all included. 293 pages. 8th Revised Edition. Fully illustrated. $1.50 PRACTICAL INSTRUCTOR AND REFERENCE BOOK FOR LOCOMOTIVE FIREMEN AND ENGINEERS. By Chas. F. Lockhabt. 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 $2.50 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 vision- ary 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 CATALOGUE OF GOOD, PRACTICAL BOOKS 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 be may receive or the action required by certain rules. < As nearly all roads require trainmen to pass regular exami- nations, 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. Second Edition revised. 234 pages. Fully illus- trated with Train- Signals in Colors. 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 tip — 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: 1. Analysis of the gear. 2. Designing and erecting the gear. 3. Advantages of the gear. 4. Questions and answers relating to the Walschaert Valve Gear. 5. Setting valves with the Wal- schaert 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 engi- neers in preparing for an examination for promotion. 245 pages. Fully illustrated. Third Revised New Edition. Price $2.50 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 anyone 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. Second Revised and Enlarged Edition. Price $2.50 26 CATALOGUE OF GOOD, PRACTICAL BOOKS MACHINE-SHOP PRACTICE AMERICAN TOOL MAKING AND INTERCHANGEABLE MANUFACTUR- ING. 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 what- ever 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 pro- duction of machined metal parts are imperative. The science of jig making is exhaus- tively 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 devicas illustrated and de- scribed have been or are used for the actual production of work, such as parts of drill presses, lathes, patented machinery, typewriters, electrical apparatus, mechanical ap- pliances, brass goods, composition parts, mould products, sheet metal articles, drop- forgings, jewelry, watches, medals, coins, etc. 3rd Edition* 531 pages. Price $4.50 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 in 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. 7th edition. 131 pages. Price 75 cents MODERN MACHINE-SHOP CONSTRUCTION, EQUIPMENT AND MAN- AGEMENT. By Oscar E. Perrigo. The only work published that describes the Modern 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 prac- tical shop man for practical shop men who are too busy to read theories and want facts. It is the most complete all-round book of its kind ever published. . 384 pages. 219 original and specially-made illustrations. Revised and Enlarged Edition. Price $5.00 "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. 5th edition. Price $3.00 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. 4th edition. Price ._ 35 €@nt§ 27 CATALOGUE OF GOOD, PRACTICAL BOOKS THE WHOLE FIELD OF MECHANICAL MOVEMENTS COVERED BY MR. HISCOX'S TWO BOOKS We publish two books by Gardner D. Hiscox that will keep you from "inventing'* things that have been done before, and suggest ways of doing things that you have not thought of before. Many a man spends time and money, pondering over some mechanical problem, only to learn, after he has solved the problem, that the same thing has been accomplished and put in practice by others long before. Time and money spent in an effort to accom- plish what has already been accomplished are time and money LOST. The whole field of mechanics, every known mechanical movement, and practically every device is covered by these two books. If the thing you want has been invented, it is illustrated in them. If it hasn't been invented, then you'll find in them the nearest things to what you want, some movements or devices that will apply in your case, perhaps; or which will give you a key from which to work. No book or set of books ever published is of more real value to the Inventor, Draftsman, or practical Mechanic than the two volumes described below. 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 follow- ing 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. 15th edition enlarged. 400 octavo pages. Price . $4.00 MECHANICAL APPLIANCES, MECHANICAL MOVEMENTS AND NOVEL- TIES 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 lock 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. 4th Edition enlarged. Price $4.00 SHOP PRACTICE FOR HOME MECHANICS. By Raymond Francis Yates. A thoroughly practical and helpful treatment prepared especially for those who have had little or no experience in shop work. The introduction is given over to an ele- mentary explanation of the fundamentals of mechanical science. This is followed by several chapters on the use of small tools and mechanical measuring instruments. Elementary and more advanced lathe work is treated in detail and directions given for the construction of a number of useful shop appliances. Drilling and reaming, heat treatment of tool steel, special lathe operations, pattern making, grinding, and grinding operations, home foundry work, etc., make up the rest of the volume. The book omits nothing that will be of use to those who use tools or to those who wish to learn the use of tools The great number of clear engravings (over 300) add tremendously to the text matter and to the value of the volume as a visual instructor. Octavo, 320 pages, 309 engravings. Price ♦ ,,,,,,,... $3.00 28 CATALOGUE OF GOOD, PRACTICAL BOOKS MACHINE-SHOP TOOLS AND SHOP PRACTICE. By W. H. Vandervoort. A work of 552 pages and 672 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. 7th Edition. 552 pages. 672 illustrations. Price $4.50 COMPLETE PRACTICAL MACHINIST. By Joshua Rose. The new, twentieth revised and enlarged edition is now ready. This is one of the best-known books on machine-shop work, and written for the practical workman in the language of the workshop. It gives full, practical instructions on the use of all kinds of metal-working tools, both hand and machine, and tells how the work should be properly done. It covers lathe work, vise work, drills and drilling, taps and dies, hardening and tempering, the making and use of tools, tool grinding, mark- ing out work, machine tools, etc. No machinist's library is complete without this TOlume. 20th Edition. 547 pages. 432 illustrations. Price .... $3.00 HENLEY'S ENCYCLOPEDIA OF PRACTICAL ENGINEERING AND ALLIED TRADES. Edited by Joseph G. Horner, A.M.LMech.E. This book covers the entire practice of Civil and Mechanical Engineering. Tho 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. It is a moderm treatise in five volumes. Handsomely bound in half morocco, each volume containing nearly 500 pages, with thousands of illustrations, including dia- grammatic and sectional drawings with full explanatory details. Five large volumes. Price $30.00 MODEL MAKING Including Workshop Practice, Design and Construction of Models. Edited by Raymond F. Yates. Editor of "Everyday Engineering Magazine." This book will help you to become a better mechanic. It is full of suggestions for those who like to make things, amateur and professional alike. It has been prepared es- pecially for men with mechanical hobbies. Some may be engineers, machinists, jew- elers, pattern makers, office clerks or bank presidents. Men from various walks of life have a peculiar interest in model engineering. Model Making will be a help and an inspiration to such men. It tells them "how-to-do" and "how-to-make" things in simple, understandable terms. Not only this, it is full of good, clear working drawings and photographs of the models and apparatus described. Each model has been constructed and actually works if it is made according to directions. 379 pages. 300 illustrations. Price , $3.00 ABRASIVES AND ABRASIVE WHEELS. By Fred B. Jacobs. A new book for everyone interested in abrasives or grinding. A careful reading of the book will not only make mechanics better able to use abrasives intelligently, but it will also tell the shop superintendent of many short cuts and efficiency-increasing kinks. The economic advantages in using large grinding wheels are fully explained, together with many other things that will tend to give the superintendent or workman a keen insight into abrasive engineering. 340 pages. 174 illustrations. This is an indispensable book for every machinist. Price $3.00 HOME MECHANIC'S WORKSHOP COMPANION. By Andrew Jackson, Jr. This treatise includes a compilation of useful suggestions that cannot fail to interest the handy man, and while it is not intended for mechanical experts or scientists, it will prove to be a veritable store of information for anyone who desires to rig up a small shop where odd jobs can be carried on. Price 75 cents 29 CATALOGUE OF GOOD, PRACTICAL BOOKS MARINE ENGINEERING THE NAVAL ARCHITECT'S AND SHIPBUILDER'S POCKETBOOK. Of Formulae, Rules, and Tables and Marine Engineer's and Surveyor's Handy Book of Reference. By Clement Mackrow and Lloyd Woollard. The twelfth revised and enlarged edition of this most comprehensive work has just been issued. It is absolutely indispensable to all engaged in the Shipbuilding Industry, as it condenses into a compact form all data and formulaeithat are ordinarily required. The book is completely up to date, including among other subjects a section on Aeronautics. 760 pages, limp leather binding. Price $6.00 MARINE ENGINES AND BOILERS— THEIR DESIGN AND CONSTRUC- TION. THE STANDARD BOOK. By_Dn. 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 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 in- formation 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. The work is clearly written, thoroughly systematic, theoretically sound; while the character of the 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. Fifth impression. ,744 pages. 550 illustrations, and numerous tables. Cloth. Price . . . $10.00 MANUAL TRAINING «■— — !■■■ r» i...m ^ i ^^^wt ECONOMICS OF MANUAL TRAINING. By Louis Routllion. 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 1 174 pages, and is fully illustrated. 2d edition. Price $2.00 MOTOR BOATS MOTOR BOATS AND BOAT MOTORS. By Victor W. Page and A. C. Leitch. All who are interested in motor boats, either as owners, builders or repairmen, will find this latest work a most comprehensive treatise on the design, construction, opera- tion and repair of motor boats and their power plants. It is really two complete books in one cover as it consists of two parts, each complete in itself. Part One deals with The Hull and Its Fittings, Part Two considers The Power Plant and Its Auxiliaries. A valuable feature of this book is the complete set of dimensioned working drawings detailing the construction of five different types of boats ranging from a 16-foot shallow draft, tunnel stern general utility craft to a 25-foot cabin cruiser. These plans are by A. C. Leitch, a practical boat builder and expert naval architect, and are complete in every particular. Full instructions are given for the selection of a power plant and its installation in the hull. Valuable advice is included on boat and engine operation and latest designs of motors are described and illustrated. The instructions for overhauling boat and engine are worth many times the small cost of the book. It is a comprehensive work of reference for all interested in motor boating in any of its phases. Octavo. Cloth. 372 illustrations. 524 pages. Price $4.00. 3° CATALOGUE OF GOOD, PRACTICAL BOOKS MOTORCYCLES MOTORCYCLES AND SIDE CARS, THEIR CONSTRUCTION, MANAGE- MENT AND REPAIR. By Victor W. Page, M.E. The only complete work published for the motorcyclist and repairman. Describes fully all leading types of machines, their design, construction, maintenance, operation and repair. This treatise outlines fully the operation of two- and four-cycle power plants and all ignition, carburetion and lubrication systems in detail. Describes all representative types of free engine clutches, variable speed gears and power trans* mission systems. Gives complete instructions for operating and repairing all types. Considers fully electric self-starting and lighting systems, all types of spring frames and spring forks and shows leading control methods. For those desiring technical information a complete series of tables and many formulae to assist in designing are included. The work tells how to figure power needed to climb grades, overcome air resistance and attain high speeds. It shows how to select gear ratios for various weights and powers, how to figure braking efficiency required, gives sizes of belts and chains to transmit power safely, and shows how to design sprockets, belt pulleys, etc. This work also includes complete formulas for figuring horse-power, shows how dyna- mometer tests are made, defines relative efficiency of air- and water-cooled engines, plain and anti-friction bearings and many other data of a practical, helpful, engineering nature. Kemember that you get this information in addition to the practical de- scription and instructions which alone are worth several times the price of the book. 2nd Edition Revised and Enlarged. 693 pages. 371 specially made illustrations. Cloth. Price $3.00 WHAT IS SAID OF THIS BOOK: " Here is a book that should be in the cycle repairer's kit." — American Blacksmith. " The best way for any rider to thoroughly understand his machine, is to get a copy of this book; it is worth many times its price." — Pacific Motorcyclist. PATTERN MAKING PRACTICAL PATTERN MAKING. By F. W. Barrows. This book, now in its second edition, is a comprehensive and entirely practical treatise on the subject of pattern making, illustrating pattern work in both wood and metal, and with definite instructions on the use of plaster of Paris in the trade. It gives specific and detailed descriptions of the materials used by pattern makers and de- scribes the tools, both those for the bench and the more interesting machine tools; having complete chapters on the Lathe, the Circular Saw, and the Band Saw. It gives many examples of pattern work, each one fully illustrated and explained with much detail. These examples, in their great variety, offer much that will be found ot interest to all pattern makers, and especially to the younger ones, who are seeking information on the more advanced branches of their trade. In this second edition of the work will be found much that is new, even to those who have long practiced this exacting trade. In the description of patterns as adapted to the Moulding Machine many difficulties which have long prevented the rapid and economical production of castings are overcome; and this great, new branch of the trade is given much space. Stripping plate and stool plate work and the less expen- sive vibrator, or rapping plate work, are all explained in detail. Plain, everyday rules for lessening the cost of patterns, with a complete system of cost keeping, a detailed method of marking, applicable to all branches of the trade, with complete information showing what the pattern is, its specific title, its cost, date of production, material of which it is made, the number of pieces and core- boxes, and its location in the pattern safe, all condensed into a most complete card record, with cross index. The book closes with an original and practical method for the inventory and valua- tion of patterns. 2nd Edition. Containing nearly 350 pages and 170 illustra- tions. Price $2.50 3i CATALOGUE OF GOOD, PRACTICAL BOOKS PERFUMERY PERFUMES AND COSMETICS, THEIR PREPARATION AND MANUFAC- TURE. By G. W. Askinson, Perfumer. A comprehensive treatise, in which there has been nothing omitted that could be of value to the perfumer or manufacturer of toilet preparations. 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, including a chapter on synthetic products, with formulas for their use. A book of general, as well as professional in- terest, meeting the wants not only of the druggist and perfume manufacturer, but also of the general public. Fourth Edition much enlarged and brought up-to-date. Nearly 400 pages, illustrated. Price $5.00 WHAT IS SAID OF THIS BOOK: •' The most satisfactory work on the subject of Perfumery that we have ever seen. •' We feel safe in saying that here is a book on Perfumery that will not disappoint you, for it has practical and excellent formulae that are within your, ability to prepare readily. " We recommend the volume as worthy of confidence, and say that no purchaser will be disappointed in securing from its pages good value for its cost, and a large dividend on the same, even if he should use but one per cent of its working formulae. There is money in it for every user of its information." — Pharmaceutical Record. 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 mechan- ical drawing. 2. Perspective versus mechanical drawing in showing plumbing con- struction. 3. Correct and incorrect methods in plumbing drawing; plan and elevation explained. 4. 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. Drawings 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. Ele- vations of separate parts of the plumbing system. 16. Elevations from the architect's plans. 17. Drawings of detail plumbing connections. 18. Architect's plans and plumb- ing elevations of residence. 19. Plumbing elevations of residence (continued) ; plumb- ing plans for cottage. 20. Plumbing elevations; roof connections. 21. Plans and plumbing elevations for six-flat building. 22. Drawing of various parts of the plumb- ing 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, radia- tors, coils, etc. 26. Drawing of piping to illustrate heating systems. 150 illustrations. Price $2.00 32 CATALOGUE OF GOOD, PRACTICAL BOOKS 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, laun- dry waste, fines 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 con- tinuous venting; continuous venting for two-floor work; continuous venting for two lines of fixtures on three or more floors; continuous venting of water closets; plumb- ing for cottage house; construction for cellar piping; plumbing for residence, use of special fittings; plumbing for two-flat house; plumbing for apartment building, plumb- ing for double apartment building; plumbing for office building; plumbing for public toilet rooms; plumbing for public toilet rooms, continued; plumbing for bath estab- lishment; 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; construc- tion 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; sug- gestion for estimating plumbing construction. 407 octavo pages, fully illustrated by 58 full-page engravings. Third, revised and enlarged edition just issued. Price . $5.00 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 connec- tions; 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 . , , ,_, , . $3,50 33 CATALOGUE OF GOOD, PRACTICAL BOOKS RECIPE BOOK HENLEY'S TWENTIETH CENTURY BOOK OF RECIPES, FORMULAS AND PROCESSES. Edited by Gardner D. Hiscox. The most valuable Techno-chemical Formula'Book published, including over 10,000 selected scientific, chemical, technological, and practical recipes and processes. This is the most complete Book of Formulas ever published, giving thousands of recipes for the manufacture 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, and is 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 immeasurably 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 manufacture, 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, a*id Mucilages, the Compounder of Alloys, the Cook, the Physician, the Druggist, the Electrician, the Brewer, the Engineer, the Poundryman, the Machinist, the Potter, the Tanner, the Confectioner, the Chiropodist, the Manicure, the Manufacturer of Chem- ical 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 Dairy- man, the Paper Maker, the Wood and Metal Worker, the Chandler and Soap Maker, the Veterinary Surgeon, and the Technologistjn 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. Every home needs this book; every office, every factory, every store, every public and private en- terprise — EVERYWHERE — shouldj have a copy. 800 pages. Cloth Bound. Price $4.00 WHAT IS SAID OF THIS BOOK: "Your Twentieth Century Book of Recipes, 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. Trxjx, 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." — Merchants' Record and Show Window. "I purchased your book 'Henley's Twentieth Century Book of Recipes, Formulas and Processes' about a year ago and it is worth its weight in gold." — Wm. H. Murray, ; .Bennington, Vt. ''THE BOOK WORTH THREE HUNDRED DOLLARS" "On close examination of your 'Twentieth Century Receipt Book,' I find it to be a very valuable and useful book with the very best of practical information obtainable. The price of the book, $4.00, is very small in comparison to the benefits which one can obtain from it. I consider the book worth fully three hundred dollars to anyone." — Dr. A. C. Spetts, New York. "ONE OF THE WORLD'S MOST USEFUL BOOKS" " Some time ago, I got one of your ' Twentieth Century Books of Formulas ' and have made my living from it ever since. I am alone since my husband's death with two small children to care for and am trying so hard to support them. I have customers who take from me Toilet Articles I put up, following directions given in the book, and I have found every one of them to be fine." — Mrs. J. H. McMaken, West Toledo, Ohio. - 34 CATALOGUE OF GOOD, PRACTICAL BOOKS ~— — ^ — *^— ^— — — — — -■— — ^ — "— ■ ~— *^ ■■ - — — *~ » — — — * ~ ■— — ■ ■■ ~^ — — ^ ^— «■» ' m i l » RUBBER RUBBER HAND STAMPS AND THE MANIPULATION OF INDIA RUBBER. By T. O'Conok 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 Solu- tions, 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 . $1.50 SAWS SAW FILING 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 rim 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 filing, and is a practical aid to those who use saws for any purpose. Complete tables of proper shape, pitch, and saw teeth as well as sizes and number of teeth of various saws are included. Fourth edition, revised and enlarged. Illustrated. Price $1.50 SCREW CUTTING THREADS AND THREAD-CUTTING. By Colvin and Stable. 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. Fourth Edition. Price ...... 35 cents STEAM ENGINEERING 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 Examin- ing 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. 3d Edition. . . . $3.50 35 CATALOGUE OF GOOD, PRACTICAL BOOKS 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 anyone 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 prevent- ing "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; hard- ened 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 roots; 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. Third edition. 311 pages. 131 Illustrations. Price. . . . $2.50 ENGINE RUNNER'S CATECHISM." By Robert Grimshaw. A practical treatise for the stationary engineer, telling how to erect, adjust, and run the principal steam 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 and 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 HORSE-POWER CHART. Shows the horse-power of any stationary engine without calculation. No matter what the cylinder diameter of stroke, the steam pressure of 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 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- foua 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 beginneF 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 36 CATALOGUE OF GOOD, PRACTICAL BOOKS STEAM ENGINEER'S ARITHMETIC. By Golvin-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 of the little kinks in figuring what- ever 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 a thousand and one other things; and everything is plain and simple — not the hardest way to figure, but the easiest. Second Edition 75 cents STEAM ENGINE TROUBLES. By H. Hamkens. It is safe to say that no book has ever been published which gives the practical en- gineer such valuable and comprehensive information on steam engine design and troubles. Not only does it describe the troubles the principal parts of steam engines are subject to; it contrasts good design with bad, points out the most suitable material for certain parts, and the most approved construction of the same; it gives directions for correct- ing existing evils by following which breakdowns and costly accidents can be avoided. Just look into the nature of the information this book gives on the following sub- jects. There are descriptions of cylinders, valves, pistons, frames, pillow blocks and other bearings, connecting rods, wristplates, dashpots, reachrods, valve gears, gover- nors, piping, throttle and emergency valves, safety stops, fly-wheels, oilers, etc. If there is any trouble with these parts, the book gives you the reasons and tells how to remedy them. The principal considerations in the building of foundations are given with the size, area and weight required for the same, also the setting of templets and lining up, and a complete account of the erection and "breaking in" of new engines in the language, of the man on the job. Contains special chapters on: I. Cylinders. II. Valves. III. Piping and Separa- tors. IV. Throttle and Emergency Valves. V. Pistons. VI. Frames. VII. Bear- ings, VIII. Connecting Rods. IX. Hockrods. X. Dashpots. XI. Governors. XII. Releasing Gears. XIII. Wristplates and Valve Motions. XIV. Rodends and Bonnets. XV. Oilers. XVI. Receivers. XVII. Foundations. XVIII. Erection. XIX. Valve-Setting. XX. Operation. 284 pages. 276 illustrations. Price $2,50 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 nubject and has been pre- pared for the use of all engaged in the business of steam, hot- water heating, and ventila- tion. 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 every- one 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 ventila- tion. 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. Miscella- neous 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. XXVIII. Rules, tables, and useful information. 402 pages. 300 detailed engravings. Third Edition — Revised. Price ••»#•••.... $3.56 37 CATALOGUE OF GOOD, PRACT ICAL BOOKS p— — ~ , ~^"" — — — — — — BOO PLAIN ANSWERS TO DIRECT QUESTIONS ON STEAM, HOT-WATER, VAPOR AND VACUUM HEATING PRACTICE. By Alfred G. King. This work, just off the press, is arranged in question and answer form ; it is intended a3 u guide and text-book for the younger, inexperienced fitter and as a reference book for all fitters. This book tells "how" and also tells "why." No work of its kind has ever been published. It answers all the questions regarding each method or system that would be asked by the steam fitter or heating contractor, and may be used as a text or reference book, and for examination questions by Trade Schools or Steam ^Fitters' Associations. Rules, data, tables and descriptive methods are given, to- gether with much other detailed information of daily practical use to those engaged in or interested in the various methods of heating. Valuable to those preparing for examinations. Answers every question asked relating to modern Steam, Hot- Water, Vapor and Vacuum Heating. Among the contents are: The Theory and Laws of Heat. Methods of Heating. Chimneys and Flues. Boilers for Heating. Boiler Trimmings and Settings. Radiation. Steam Heating. Boiler, Radiator and Pipe Connections for Steam Heating. Hot Water Heating. The Two-Pipe Gravity System of Hot Water Heating. The Circuit System of Hot Water Heating. The Overhead System of Hot Water Heating. Boiler, Radiator and Pipe Connections for Gravity Systems of Hot Water Heating. Accelerated Hot Water Heating. Ex- pansion Tank Connections. Domestic Hot Water Heating. Valves and Air Valves. Vacuum Vapor and Vacuo- Vapor Heating. Mechanical Systems of Vacuum Heating. ^Non-Mechanical Vacuum Systems. Vapor Systems. Atmospheric and Modulating Systems. Heating Greenhouses. Information, Rules and Tables. 214 pages, 127 illustrations. Octavo. Cloth. Price. . . . . * , . . , , . $2.00 STEEL BTEEL: ITS SELECTION, ANNEALING, HARDENING, AND TEMPERING. 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 the 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, harden- ing, 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; harden- ing steel; drawing the temper after hardening; examples of hardening; pack harden- ing; case hardening; spring tempering; making tools of machine steel; special steels; steel for various tools, causes of trouble; high speed steels, etc. 400 pages. Very fully illustrated. Fourth Edition. Price $3.00 HARDENING, TEMPERING, ANNEALING, AND FORGING OF STEEL. INCLUDING HEAT TREATMENT OF MODERN ALLOY STEELS. By J. V. WoQDWORTH. A new work treating in a clear, concise manner all modern processes for the heating, annealing, forging, welding, hardening, and tempering of high and low grade 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 satis- factory 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 adaptation of machinery steel for tools of various kinds. 5th Edition, 321 pages. 201 illustrations, >?rice $3.00 38 CATALOGUE OF GOOD, PRACTICAL BOOKS TRACTORS MODERN GAS TRACTOR: ITS CONSTRUCTION, UTILITY, OPERATION AND REPAIR. By Victor W. Page. An enlarged and revised edition that treats exclusively on the design and construction of farm tractors and tractor power plants, and gives complete instructions on their care, operation and repair. All types and sizes of gasoline, kerosene and oil tractors are described, and every phase of traction engineering practice fully covered. In- valuable to all desiring reliable information on gas motor propelled traction engines? and their use. All new 1921 types of tractors are described and complete instructions are given for their use on the farm. The chapter on engine repairing has been greatly enlarged and complete and detailed instructions are now given for repairing weh- known and widely used tractor power plants, numerous new forms of which are described. Valuable information compiled by Government experts on laying out- fields for tractor plowing and numerous practical suggestions for hitches so all types; of agricultural machinery can be operated by tractors, are outlined. The chapter- on tractor construction and upkeep has been more than doubled in size. Over 10O new illustrations have been added and the book greatly enlarged. Full instructions: are now given for using kerosene and distillate as fuel. The 1921 edition is 38> per- cent larger than the second edition and is more than ever the acknowledged authemiy' on farm tractors and their many uses. 5 \i x 1 X A inches. Cloth, nearly 700 pages*- and about 300 illustrations, 3 folding plates. Price _• . $3.00 WELDING MODERN WELDING METHODS. By Victor W. Page 1 . One of the most instructive books on all methods of joining metals yet published for the mechanic and practical man. It considers in detail oxy-acetylene welding, the Thermit process and all classes of electric arc and resistance welding. It shows all the apparatus needed and how to use it. It considers the production of welding gases, construction and operation of welding and cutting torches of all kinds. It details the latest approved methods of preparing work for welding. All forms of gas and electric welding machines are described and complete instructions are given for installing electric spot and butt welders. Cost data are given and all methods of doing the work economically are described. It includes instructions for forge and dip brazing and manufacture of hard solders and spelters. It shows and explains soft soldering processes and tells how to make solders for any use. Complete instruc- tions are given for soldering aluminum and authoritative formulas for aluminum solders are included. 292 pages. 200 illustrations. 1921 edition. Price . . '$3.00 AUTOMOBILE WELDING WITH THE OXY-ACETYLENE FLAME. By M. Keith Dunham. Explains in a simple manner apparatus to be used, its care, and how to construct necessary shop equipment. Proceeds then to the actual welding of all automobile parts, in a manner understandable by everyone. Gives principles never to be for- gotten. This book is of utmost value, since the perplexing problems arising when metal is heated to a melting point are fully explained and the proper methods to overcome them shown. 167 pages. Fully illustrated. Price . , ♦ , , $1,50 39 MTC , a. .DATE DUE J-73U 1 SEP ~l 1993 JAM \ \ 2 2004 UNIVERSITY PRODUCTS, INC. #859-5503 142757 BOSTON COLLEGE Pill lill I llllll III! 3 9031 01460939 i ^^-msMBKmtamm ' BOSTON COLLEGE LIBRARY UNIVERSITY HEIGHTS CK siNUT HILL, MASS. Books may be kept for two weeks and may be renewed for the same period, unless reserved. Two cents a day is charged for each book kept overtime. If you cannot find what you want, ask the Librarian who will be glad to help you. The borrower is responsible for books drawn on his card and for all fines accruing on the same.