UC-NRLF ji_n_*n_ REESE LIBRARY . or mi-. UNIVERSITY OF CALIFORNIA. 1 THE MANAGEMENT OF DYNAMOS THE MANAGEMENT OF DYNAMOS B 1banfcboofe ot Hbcors ant) practice FOR THE USE OF MECHANICS, ENGINEERS, STUDENTS, AND OTHERS IN CHARGE OF DYNAMOS BY G. W. LUMMIS-PATERSON ij ELECTRICAL ENGINEER IRumerous 5Uu6tration0 (UNIVERSITY) X. OF ,/ LONDON CROSBY LOCKWOOD AND SON 7 STATIONERS' HALL COURT, LUDGATE HILL 1895 " ' f \ PREFACE. IN preparing this volume, it has been the aim of the Author to keep in view the requirements of Mechanics, Engineers, Students, and others, who, having (or expecting to have) the charge of Dynamos, desire to make themselves sufficiently acquainted with their construction, as well as with those scientific principles of which some knowledge is required for the intelligent management of the dynamo. The work which has been arranged in what appeared to the Author its natural order may be regarded as consisting of three parts, although these " parts " overlap each other. In the First of such parts, comprising Chapters I. to IV., the elementary theory of the dynamo, and the elec- trical and magnetic laws and truths affecting its construction, are considered briefly, and only in so VI PREFACE. far as they relate to the management of the dynamo: in the Second part, which includes Chapters IV. to VIII., the construction and action of the different classes of dynamos in common use are described : while the Third part Chapters VIII. to XII. relates to -such matters as affect the practical management and working of dynamos. For the full theory of the dynamo the reader is referred to the works of Thompson, Kapp, Fleming, and others. H EATON, NEWCASTLE-ON-TYNE, June 1895. XTKIVERSITT CONTENTS. CHAPTER I. ELECTRICAL UNITS i CHAPTER II. MAGNETIC PRINCIPLES - 13 CHAPTER III. THEORY OF THE DYNAMO 26 CHAPTER IV. ARMATURES 39 CHAPTER V. ARMATURES IN PRACTICE 5 8 CHAPTER VI. FIELD MAGNETS - 75 CHAPTER VII. FIELD MAGNETS IN PRACTICE - 89 CHAPTER VIII. REGULATING DYNAMOS - - - - - 100 Vlli CONTENTS. PAGE CHAPTER IX. COUPLING DVSNAMOS - - - - 115 CHAPTER X. RUNNING DYNAMOS - - - 133 CHAPTER XL FAULTS IN DYNAMOS - 152 CHAPTER XII. FAULTS IN ARMATURES - - - - - 196 INDEX 210 THE MANAGEMENT OF DYNAMOS. CHAPTER I. ELECTRICAL UNITS. Electro -Motive Force. Electro -motive force, also termed electric pressure, voltage, &c., occupies the same place in relation to electricity as pressure to steam or water. Water only flows from one place to another when there is a difference of level or pressure of water between the two places, and the flow of water takes place from the place of higher level or pressure to the place of lower level or pressure. In exactly the same way electricity only flows from one place or point to another when there is a difference of electrical level or pressure, or an electro-motive force, between the two places, and the flow of electricity takes place in a direction from the higher to the lower pressure. The point where the pressure is higher is said to have a positive potential, and is usually denoted by the sign + (plus) or P; and the point where the pressure is A 2 ELECTRICAL UNITS. lower is said to have a negative potential and is denoted by the sign (minus) or N. Electrical pressure, or electro-motive force, may be produced by chemical action, as in the electric battery; by the motion of electrical conductors in a magnetic field, as in the dynamo ; and by numerous other means. Fall of Pressure. Pressure in electricity and pressure in steam or water also possess other points in analogy ; e.g., in flowing from one point to another they both become less as they recede from the source, or point of higher pressure, in proportion to the resistance met with, or in doing work which may be expressed as resistance. When a current of water flows through a long length of pipe a certain amount of pressure is always lost in overcoming the resist- ance which the pipe offers to the flow of water. Similarly, when an electric current flows through a long length of conducting cable a certain amount of pressure is always absorbed in overcoming the resistance which the cable offers to the electric flow. If the cable has a uniform resistance throughout the whole of its length, the pressure will fall uni- formly ; if, however, part of the cable has a greater resistance than another, as may be the case if different portions are made of different materials, or one portion has a greater cross sectional area than another, then the pressure falls most rapidly along the part offering the greatest resistance. The fall of pressure in a "circuit" composed of different resistances is graphically represented in Fig. I. The portions of the circuit A A A A are composed of copper conducting cable, B is a coil of german silver UNIT OF ELECTRO-MOTIVE FORCE. wire, and C is an incandescent lamp. The current flows in a direction from the positive to the negative, and, as indicated by the dotted and sloping lines, the pres- FlG. I. sure falls all along the circuit in proportion to the resistance. As will be seen only a slight fall takes place in the copper portions of the circuit, for these being composed of good conducting material offer only a small resistance, as compared with the rest of the circuit ; a rather greater fall takes place in the german silver coil, whilst the greatest fall occurs in the incandescent lamp, since this latter has the greatest resistance. Unit of Electro-Motive Force. The unit of electro-motive force or electrical pressure is called the Volt, and the instrument used in practice for measuring electrical pressure is called a Voltmeter. It is possible by means of suitable machinery to produce almost any desired pressure from a fraction of a volt upwards. The pressures most commonly used in commercial practice vary from .5 volt up to 300 volts in the low tension system, and from ^x^ese LIBS?/. / r OF THE \ v (UNIVERSITY) 4 ELECTRICAL UNITS. 300 volts up to 10,000 volts in the high tension system. Current. As electro-motive force or electrical pressure is analagous to pressure in steam or water, so is electrical current analagous to the volume or quantity of water flowing through or discharging from a pipe or other conduit. Unit of Electrical Current. The unit of electrical current is called the Ampere -, and the instrument used commercially for measuring current strength is the Ammeter. Although not strictly correct, we may compare a current of electricity of so many amperes to a current of water flowing at the rate of so many gallons per minute. The ampere is therefore the name given to a particular strength of electric flow, which may be measured in various ways by the effects which it produces, as thermal, magnetic, chemical, &c. Resistance. A current of electricity always flows in a conducting circuit when its ends are kept at different potentials, in the same way that a current of water always flows in a pipe when a certain pressure of water is supplied.' The same electrical pressure does not, however, always produce a current of electricity of the same strength, nor does a certain pressure of water always produce a current of water of the same volume or quantity. In both cases the strength or volume of the currents is dependent not only upon the pressures applied, but also upon the resistance which the conducting circuit offers to the flow in the case of electricity, and on the friction (which may be expressed as resistance) which the pipe offers to the flow in the case of water. OHM'S i Conductors and Non-Conduct^SHTO-kTtown substance is an absolute non-conductor of electricity, in the same way that no known substance is an absolute non-conductor of heat. 'Some substances, however, such as wood, glass, slate, ebonite, india- rubber, &c., offer a very considerable resistance to the electric flow, and are therefore called "non- conductors " or insulators. Other substances, such as the metals, carbon, water, &c, offer only a very slight resistance to the electric flow, and are therefore called conductors. Laws of Electrical Resistance. The laws of electrical resistance are very simple, and may be briefly stated as follows : " The resistance of a con- ductor is proportional to the length of the conductor, and inversely proportional to the cross section of the conductor, and also depends upon the material of which the conductor is made, i.e., upon its specific resistance." Unit of Electrical Resistance. The unit of electrical resistance is called the Ohm, and the ohm is defined to be equal to the resistance of 1 06 centimetres of mercury, I sq. millimetre section at zero centigrade. One yard of No. 40 B.W.G. copper wire has a resistance of approximately one ohm. Ohm's Law. It has been mentioned above that the strength of an electric current is dependent upon the difference of potential between the ends of the conducting circuit, and upon the resistance of the circuit. This relation may be shown exactly by the aid of Ohm's Law, which states that " the strength of the current varies directly as the electro-motive force or pressure, and inversely as the resistance." This ELECTRICAL UNITS. law may be expressed algebraically by the following simple equation : where C = Current in amperes E = E.M.F. or pressure in volts R = Resistance in ohms; or "the number of amperes flowing in a circuit is equal to the number of volts of pressure divided by the number of ohms of resistance " in the entire circuit. Thus if we have a circuit of I ohm total resistance, and we apply a pressure of I volt, the current flowing in the circuit will be one ampere, thus : i Volt . = i ampere. I Ohm If the pressure be doubled the current will also be doubled, thus : The current will also be doubled by halving the resistance, thus : ' = 2 amperes. .5 Ohm The above equation may also be expressed as follows : E = RxC( 3 ) By means of equation (2) the resistance of any circuit can be found if the pressure and current flowing through it is known. For example : if 20 amperes CIRCUITS. are passing through a circuit at a pressure of 100 volts, the resistance will be C 20 Equation (3) is very useful as a means of ascertaining the pressure required to send a given current through a given resistance ; e.g., the pressure required to send a current of 4 amperes through a resistance of 25 ohms will be CxR = E. 4x25 = 100 volts. It will be obvious that as the pressure E is wholly expended in forcing the current C through the re- sistance R, the above equation (3) also measures the fall of potential in any circuit or portion of a circuit. Circuits. An electrical pressure being available, it is necessary, in order to have an electric flow, to provide a continuous conducting path from the point of positive potential to the point of negative potential. This path, whether composed simply of wires, or of lamps, motors, or other applications of electric power, is called a circuit, and circuits may be divided into two kinds, viz., series circuits, and parallel or shunt circuits. In the series circuit (Fig. 2), the wires, lamps, &c , are arranged end to end, so as to form one continuous conducting path connecting the two points of higher and lower potential, and the current in flowing between these points passes in succession through each of the lamps or other appliances com- posing the circuit. In the parallel or shunt circuit (Fig. 3), two main wires or leads M 1 M 2 are connected 8 ' ELECTRICAL UNITS. to the points of higher and lower potential, and the lamps, wires, &c., are connected across the two mains, or arranged side by side so as to form a FIG. 2. number of independent paths or branches, and the current in flowing from the higher to the lower potential divides itself amongst these branches in inverse proportion to their resistance. It will be apparent that the total resistance of the parallel arrangement is less than that of any of its branches, for these being arranged side by side are equivalent 4. A M. FIG. 3. to one having a cross section equal to the sum of the cross section of the branches. If the resistances of all the branches are equal, the total resistance of the circuit will be equal to the resistance of one branch divided by the number of branches. The ACTIVITY OR POWER. 9 total resistance of the series circuit is evidently equal to the sum of the resistances of each of its separate parts, since these are included in one con- tinuous path ; and for the same reason the strength of the current flowing in a series circuit is obviously everywhere the same. A circuit is said to be "closed" when it forms a continuous conducting path, and to be " open " when a discontinuity occurs in some portion such that an electric current cannot flow. When a circuit is connected or bridged across in such a manner, by some con- ducting material, so as to offer a resistance less than its normal working resistance, it is said to be " cross " or " short " circuited. Activity or Power. The activity of an electric circuit, or the rate at which energy is being ex- pended in an electric circuit, may be expressed by any of the following equations : W==EC(i) W = C 2 R(2) where E = Electrical pressure or electro-motive force. C = Current. R = Resistance. W = Activity or rate of working. If E be in volts, C in amperes, and R in ohms, the result will be in Watts, the watt being the unit of electric power, and equal to one seven hundred and forty-sixth part of a horse-power. As most in- stallations are in practice provided with an ammeter and 'voltmeter, the current and pressure may be measured with facility, and therefore equation (i) UNIVERSITY 10 ELECTRICAL UNITS. is most used in practice in determining the activity, or power of an electric circuit To measure the electrical energy of a circuit, the instruments are arranged as represented in Fig. 4 ; D is a dynamo FIG. 4. or other generator, the positive and negative ter- minals of which are connected to the two mains M M between which the lamps L L are connected in parallel. To indicate the amount of current flow- ing in the circuit, an ammeter A is inserted in " series " in one of the mains and with the lamps, and therefore the whole of the current passing to the lamps passes through the ammeter, and is measured by the latter. A voltmeter V is connected across the two main leads, or in shunt with the dynamo, and measures the difference of potential between the two mains in volts. By taking simultaneous readings of the voltmeter and ammeter the energy being expended in the circuit can be ascertained by equation (i). For example, suppose the voltmeter to indicate 100 volts, and the ammeter 100 amperes, then by equa- tion (i) EC=W. 100x100=10,000 watts are being expended in the circuit. The output of dynamos is usually expressed in watts, as this indicates HORSE-POWER. 1 1 the actual electrical power given by the machine, irrespective of the strength of the current, or its pressure, which may be varied to any extent so long as their product remains constant. For example, a machine designed for an output of 100,000 watts may be arranged to give 1,000 amperes at a pressure of 100 volts, or 10,000 amperes at 10 volts pressure, or 100 amperes at 1,000 volts pressure. The power required to drive the machine under these varying pressures and currents will remain the same, since their product remains constant. The power required to work incandescent and arc lamps and other electrical appliances is also expressed in watts. A standard candle-power, when produced by an incandescent lamp, requires at the present time an expenditure f 3-75 watts ; when produced by an arc lamp, about .5 watts is required. By dividing the output of a machine in watts, by the watts per candle- power as given above, the total candle-power the machine is capable of supplying under the two systems of illumination may be ascertained. Kilo-watt. The watt is but a very small unit, and when used for expressing the outputs of the large dynamos in use at the present time leads to inconveniently large numbers ; therefore the outputs of such machines are frequently expressed in larger units of 1,000 watts, called Kilo-watts; e.g., a dynamo capable of generating 100,000 watts is called a 100 Kilo-watt or a 100 Unit machine. Horse-power. In practice it is frequently de- sirable to have the rate of working expressed in horse-power; in this case the energy is first measured 12 ELECTRICAL UNITS. in watts, by means of the above formulae, and afterwards converted into horse-power by dividing by 746, since 746 watts are equivalent to one horse-power. As an example of the practical appli- cation of the above, suppose we have a dynamo supplying current to 20-16 candle-power incandes- cent lamps, and we wish to ascertain the horse- power being expended in driving them ; then, as each lamp absorbs 60 watts, 20 X 60 = 1 200 watts are being expended. Dividing by 746 to bring to horse-power we get 1.6; the electrical horse-power being absorbed by the lamps is therefore 1.6 horse- power. In calculating the mechanical powers re- quired on the dynamo pulley to drive the above load, a further allowance must be made, depending upon the efficiency of the dynamo, on account of the power lost in exciting the dynamo, friction of bearings, &c. Assuming the dynamo to have a com- mercial efficiency of 85 per cent, the brake horse- power required to drive would be ijooxioo ower 746 x 85 CHAPTER II. MAGNETIC PRINCIPLES, SINCE the theory of the dynamo is essentially mag- netic, it will be necessary, before proceeding to describe its action, to consider the elementary magnetic princi- ples underlying its construction. The Magnetic Field. This is the term applied to any space within which the well-known magnetic forces of attraction or repulsion are observable. Every- one knows that there is a limited space or area sur- rounding the ends or poles of a* magnet through which small pieces of iron are attracted, or the ends or poles of other magnets are attracted or repelled, and it is to this space that the term " field of mag- netic force," or " magnetic field," is applied. The properties of the magnetic force at any point in a magnetic field may be specified, like a mechanical force, by three quantities, viz., the position or point of application, the direction, and the intensity of the magnetic force ; of these three quantities the last two only need, however, be considered in connection with the dynamo. Direction of Magnetic Force. The direction of the magnetic force at any point in a magnetic field 14 MAGNETIC PRINCIPLES. may be defined as the direction in which a small pivoted magnetic needle points when held in the field at that point. If a small suspended magnetic needle or pocket-compass be placed at various points in the magnetic field surrounding a bar magnet, as V*" FIG. 5. represented in Fig. 5, it will be found that the needle always points in a definite direction, which direction varies with its position in the field, the direction of the magnetic axis of the needle at any point repre- senting the direction of the magnetic force at that point. Lines of Force. If a magnetic needle, similar to that in the above experiment, be suspended by means of a thread over a bar magnet, and moved from the north to the south pole of the magnet, as illustrated in Fig. 6, the centre of the needle will trace out curving lines connecting the two poles. The paths or STRENGTH OF MAGNETIC FIELD. 15 lines followed by the centre of the magnetic needle are termed lines of magnetic force, and in the modern conception of a magnetic field this latter is assumed to be entirely filled up with these imaginary lines of force. These lines of force are assumed, for reasons to be hereafter understood, to have a certain positive / X / - - V ~-^ > V 4 , . - , ~ - - \ / f > & /' FIG. 6. direction, namely that direction in which a small north-seeking magnetic pole would tend to move if placed in the magnetic field ; or, in other words, the lines of force are assumed to stream or flow in a direction from the north to the south pole, as indi- cated by the arrows in Fig. 6. Intensity or Strength of Magnetic Field. The relative intensity (and this is all that is required for the present purpose) or strength of a magnetic field at different points may be conveniently expressed by the density or number of lines of force passing through a unit of area at the points in question ; i6 MAGNETIC PRINCIPLES. hence where the lines of force are few, the field is weaker than where they are more dense. Graphic Representation of Magnetic Fields. The arrangement of the lines of force in any magnetic field may be most expeditiously and conveniently represented by the well known experiment of dusting iron filings upon a sheet of cardboard placed in the magnetic field. In this experiment each of the little particles of iron become magnetised by " induction," and are for the time being transformed into small magnetic needles, which set themselves, in obedience to the attractions and repulsions of the magnetic field, along the directions of the magnetic lines, and N S FIG. 7. thus map out the directions of the magnetic force at every point in the field. The arrangement of the lines of force in the magnetic field of a permanent PERMANENT MAGNETS. bar and horse-shoe magnet, as made apparent by this method, is shown in Figs. 7 and 8. It will be seen that the filings arrange themselves in curving lines connecting the two poles of the magnets. It will also be noticed that the density of the lines and therefore the intensity of the magnetic field is greatest 1 8 MAGNETIC PRINCIPLES. near the poles or ends of the magnets, and that the strength of the field decreases as the distance from the poles increases. Electro-Magnetism. When an electric current is passing through a wire or conductor the wire is found to develop magnetic properties. It creates a mag- netic field, and attracts or repels the poles of a magnet, and is attracted or repelled by a magnet, FIG. 9. according to the nature of the pole and the direction of the current flowing in the wire. The arrangement of the lines of force in the magnetic field surrounding a straight wire or conductor through which an electric current is passing, as made apparent by passing the wire vertically through a sheet of cardboard and sprinkling iron filings thereon, is shown in Fig. 9. It will be seen that the filings arrange themselves in concentric circles around the wire, and that the strength of the field as represented by the density ot the lines is greatest immediately around the wire, and falls off as the distance from the wire increases. The wire is in fact surrounded by a sort of magnetic whirl, which may be observed at any portion of the wire, however great its length, so long as the current is passing. Solenoids. If a wire, while being traversed by an electric current, is wound up into a spiral coil, the arrangement becomes a " solenoid." The arrange - FlG. ment of the lines of force in the magnetic field surrounding a solenoid is represented in Fig. 10. It will be observed that the lines of force form con- 2O MAGNETIC PRINCIPLES. tinuous closed curves running through the interior of the coil, and issuing from one end and entering into the other end of the coil, and that the arrange- ment of the external magnetic field is very similar to that of a permanent bar magnet of cylindrical form as represented in Fig. 7. A solenoid has north and south poles, and in fact possesses all the properties of an ordinary permanent magnet, with the important difference that the magnetism is entirely under con- trol, for it is found that under all circumstances the strength of the magnetic field of a solenoid is at every point proportional to the strength of the electric current passing through its coils : if the current is increased, the magnetism is increased in proportion also ; and if the current is stopped, all trace of magnetism disappears. The magnetic effect or the magnetising power of a solenoid is also proportional to the number of turns of wire composing the coil; hence the magnetising power of I ampere flowing through 10 turns of wire is exactly equal to that of 10 amperes flowing through I turn, or to that of 5 amperes flowing through 2 turns. The product of the number of turns of a solenoid by the strength of the current flowing through them in amperes is called the ampere turns of the solenoid, and the magnetising power of a solenoid is proportional to the ampere turns of the solenoid. Professor Jamieson's Rules. If the direction of the electric current flowing through the coils of a solenoid is reversed, the polarity of the solenoid is reversed also, t.e. y that which was formerly the south pole becomes the north pole, and that which was formerly the north pole becomes the south pole. PROFESSOR JAMIESON'S RULES. 21 Professor Jamieson has devised two very useful rules, which are especially applicable in the coupling up of the coils of dynamo field magnets, for ascertaining the polarity of a solenoid when the direction of the current flowing through its coils is known, or vice versa. RULE i. To ascertain the polarity of a solenoid when the direction of the current in the windings is known : Place the right hand upon the solenoid as FIG. ii. shown in Fig. 1 1, with the fingers pointing in the direction of the current, then the thumb points in the direction of the north pole of the solenoid. RULE 2. Ascertain the north pole of the solenoid by means of a compass needle, then by placing your right hand upon the solenoid (as shown in the Fig.) so that the outstretched thumb points in the direction of the north pole (or where the magnetic lines leave 22 MAGNETIC PRINCIPLES. the coil), the fingers will point in the direction of the current passing through the windings. Electro-Magnets. If, whilst an electric current is circulating in the coils of a solenoid, a mass of iron such as an iron bar is introduced into its interior, it is found that the strength of the magnetic field is enormously increased. This increase in the strength of the field is due to the fact that the iron has a less magnetic resistance than the air, or a greater con- ductibility for the lines of force, and therefore a greater number of lines pass through the iron than what previously passed through the air. With well annealed wrought-iron the " induction," or number of lines of force, passing through a unit of area of cross section may be increased in the ratio of I : 2000, or for every line passing through a unit of area of air 2000 would pass through an equal area of wrought- iron. This property of wrought-iron is taken ad- vantage of in the construction of electro magnets, by means of which much more powerful magnetic effects may be produced than by the use of simple solenoids or permanent magnets. An electro magnet is merely a solenoid provided with an iron core of varying form. As previously mentioned, the strength of the magnetic field of a solenoid is strictly proportional to the strength of the current flowing in its coils ; this, however, is no longer true when the solenoid is pro- vided with an iron core or becomes an electro magnet, for the reason that the magnetic properties of the iron alters with the strength of the magnetic field. At first, the presence of the iron enormously increases the strength of the field ; after a time, however, as the strength of the current flowing in the exciting CURVE OF SATURATION. coils is increased, the conductibility of the iron for the lines of force appears to decrease, until a point is eventually reached when the presence of the iron core appears to have no effect whatever in increasing the strength of the field. At this stage the iron core may be regarded as being satiirated with lines of force, and any further increase of magnetising power will produce only a slight increase in the strength of the field, any such increase being that due to the effect of the coils alone acting merely as a simple solenoid. Curve of Saturation of Electro-Magnet. The magnetic behaviour of the iron core of an electro- LJ z O STRENCWEXCITINC CURRENT FIG. 12. magnet can best be studied by reference to Fig. 12, which represents the curve of saturation of the electro magnet. The strength of the magnetising current is 24 MAGNETIC PRINCIPLES. represented horizontally, and the magnetism evoked vertically. It will be seen that the curve rises from zero, at first, at a very steep angle, thus showing that a small increase in the strength of the magnetising current produces a great increase of magnetism ; after a time, however, as the exciting current is increased, the conductibility of the core for lines of force decreases, and the curve then commences to bend over as at A ; as the strength of the exciting current is still further increased the iron core becomes saturated, and adds nothing to the strength of the field, as is indicated by the curve being almost hori- zontal. The slight increase in the strength of the field, which is indicated by the curve being inclined at a small angle to the horizontal, is due solely to the effect of the coils alone, and it will be noted that a very great increase of exciting current is required at this stage to produce the small effect in the strength of the field indicated. Residual Magnetism. When a mass of iron, such as a bar, has once been magnetised, either by means of the electric current or a permanent magnet, it becomes a difficult matter to entirely remove all traces of magnetism from the iron when the mag- netising agent has been removed, and as a general rule a small amount of magnetism is permanently retained by the iron. The magnetism so retained by the iron is known as residual magnetism, and it varies in amount with the quality and physical and chemical composition of the iron. Well annealed pure wrought- iron as a rule possesses very little residual magnetism, while on the other hand wrought-iron which contains a large percentage of carbon or other impurities, or RESIDUAL MAGNETISM. 25 which has been subjected to some hardening process such as hammering, rolling, stamping, &c., and cast- iron, possesses a very large amount of residual mag- netism. This property of residual magnetism in iron is of great importance in the working of the self-exciting dynamo, and is indeed the essential principle of this class of machine. CHAPTER III. THEORY OF THE DYNAMO. THE construction and action of all dynamos is based upon the principle of electro-magnetic induction dis- covered by Faraday in 1831. Faraday found that currents of electricity are generated in all good electrical conductors by causing them to cut the lines of force contained in a magnetic field. Cutting Lines of Force. Reference to Fig. 13 will render clear what is meant by the term " cutting FIG. 13. the lines of force." In this diagram A A is a con- ductor, capable of being moved in any direction CUTTING LINES OF FORCE. 2J through the lines of force proceeding from the north to the south poles of the magnet N S. The two ends of the conductor A A are joined together by the flexible connecting conductor B B, which, not being included in the magnetic field, may be assumed to be removed from its influence. If now relative motion takes place between the conductor A A and the lines of force, it will be at once apparent that the conductor in its motion may either simply slide along, or cut through, the lines of force. If the conductor is moved along the lines of force in the direction of the arrow (i), i.e., parallel to the lines of force, it will merely slide through the lines without cutting them in any way, and in consequence no electro-motive force or current will be " induced " or generated in the conductor. Again, if the movement is in a direction coincident with the length of the con- ductor, as indicated by the arrow (2), the motion may again be regarded as merely a sliding one, and again no electro-motive force will be generated. If, however, the conductor is moved downwards in the direction of the arrow (3), i.e., in a direction at right angles to the lines of force, an E. M. F. will be at once induced in the conductor, for the latter in its motion " cuts " through the lines of force. The direction in which the E. M. F. acts, and in which the resulting current flows in the conductor, in the particular case illustrated, is indicated by the arrow marked upon the conducting circuit. The electro-motive force and current thus induced, by the relative motion of a conductor and magnetic field, only exists so long as the conductor is actually cutting the lines of force, and immediately ceases as soon as the conductor 28 THEORY OF THE DYNAMO. moves out of the magnetic field or the motion itself ceases. In all cases the value of the E. M. F. induced is directly proportional to the rate of cutting lines of force, or to the number cut per second ; the greater the speed of the conductor, and the greater the strength of the magnetic field, the greater being the value of FIG. 14. the electro-motive force induced. If the direction of motion of the conductor is reversed, i.e. y if it is moved through the lines in an upward direction, the direction of the E. M. F. induced in the conductor will be reversed also* or if, whilst the conductor is moving downwards, the direction of the lines of force is reversed by 29 changing the position of, or reversing the poles of, the magnet, the same thing will occur ; from this we see that a definite relation exists between the direc- tion of motion of the conductor, and of the magnetic lines, and of the E. M. F. induced. As in the practical applications of the dynamo it is frequently necessary to refer to this relation, a number of rules have been devised with the object of facilitating its remem- brance, of which that due to Professor Fleming, illustrated and described below, is probably the simplest and best. Professor Fleming's Rule. Spread out the thumb and first two fingers of the right hand in such a manner that each will be at right angles to the others, as re- presented in Fig. 14. Then if the thumb be pointed in the direction of motion .of the conductor, and the forefinger in the direction of the lines of force, that is, from the north pole to the south pole of the magnet, the middle finger will be pointing in the direction in which the E. M. F. induced in the conductor acts, or in which the current flows. Simple Dynamo. We have already seen that the E. M. F. and current induced in a conductor only lasts so long as the conductor is actually cutting the lines of force ; hence, in order to keep a current circulating in a conducting circuit by means of this principle, it is necessary to keep the conductor continually cutting the lines of force. This is most conveniently effected by fixing the conducting circuit upon a spindle, and revolving it in a magnetic field. An arrangement of this description is represented in Fig. 15, where A A is a spindle capable, of revolving in the magnetic field between the north and south poles of the magnet N S 30 THEORY OF THE DYNAMO. To this spindle is fixed the conducting circuit c C, the two ends of which are connected to two metallic rings fixed upon the spindle, and insulated from it FIG. 15. and from each other. Two brass brushes, Bi, B2, press upon each of these rings, and serve to convey the current generated in the conducting circuit C C to the external circuit E. If now the loop be first placed in the vertical plane, as shown, the lines of force will thread through it at right angles. As the loop is moved through the lines of force in the direction of the arrow during a complete revolution, the limbs of the loop will cut through the lines of force ; and in consequence, E. M. F.s and currents will be generated in the loop which, on applying Professor Fleming's rule, will be found to be directed as follows : Whilst the loop is passing from o to ALTERNATING CURRENTS. 31 1 80, or through half a revolution, the E. M. F. and current induced in the limb descending on the right will be directed from back to front, and in the opposite direction, i.e., from front to back, in the limb which is ascending on the left. On passing the 1 80 position, the limb which was previously descending on the right will begin to ascend on the left, and the limb which was previously ascending on the left will now begin to descend on the right. On passing the 180 position, the limbs will therefore have E. M. F.s and currents induced in them opposite in direction to those which previously flowed through them during the first half-revolution. As a result, the current flowing in the external circuit E will also be reversed at every half- revolution of the spindle, or the current will be an alternating current. As the value of the E. M. F., and consequently the strength of the current, generated in the conductor by its motion in the magnetic field is dependent upon the rate of cutting lines of force, or upon the number cut per second, we may examine how this varies during a complete revolution. As the loop moves out of the vertical plane during the first quarter- revolution, it at first moves nearly parallel to the lines of force, and consequently the rate of cutting lines is a minimum. As the rotation is continued, the rate of cutting lines gradually increases, until, upon reaching the horizontal position, the loop moves at right angles to the lines of force, and the rate of cutting lines is therefore a maximum. Upon moving out of the horizontal position the rate of cutting lines will gradually decrease until a half-revolution has been completed, when the loop UNIVERSITY 32 THEORY OF THE DYNAMO. will again be moving parallel to the lines, and con- sequently the rate of cutting lines will again be a minimum. The same thing will be repeated during the remaining half-revolution, with the difference that the E. M. F. and current will be reversed in direction, as already explained. From this it will be seen that the E. M. F. and current generated in the loop during the first quarter-revolution, or from o to 90, will rise from zero to a maximum value, and then fall to zero again during the completion EMF FIG. 16. of the half-revolution, or from 90 to 180. From 1 80 to 270 the E. M. F. will again rise from zero to a maximum, and again fall to zero as the loop moves from 270 to 360. This rise and fall of the E. M. F. during a complete revolution of the loop is graphically represented in Fig. 16, where the various positions of the loop during a complete revolution are indicated upon the horizontal line A B, which also indicates zero potential, and the vertical lines represent the value of the E. M. F. COMMUTATING CURRENT. 33 set up in the loop at these positions. The portion of the curve above the horizontal line indicates the positive direction of the E. M. F. generated during the first half-revolution of the loop, that portion below the line the reverse negative direc- tion produced by the second half-revolution. Commutating Current The arrangement of the loop or conducting circuit, as described above, con- stitutes what is known as an alternating current dynamo. By far the larger number of the practical applications of electricity are effected, however, by FIG. 17. means of continuous currents generated by con- tinuous current dynamos. In this class of machine the necessary alteration in the direction of the current is effected by a process called " commuta- tion," the appliance for effecting the alteration in C 34 THEORY OF THE DYNAMO. the direction of the current being called a " com- mutator." This appliance, in its simplest form, consists of two metallic segments s S, insulated from each other by means of a cylinder of box- wood or other insulating material, as shown in Fig. 17. The circuit is arranged upon a spindle as before, and the commutator is fixed upon the spindle in place of the two rings, and one end of the con- ducting coil or loop is connected to each of the segments. Two metallic brushes or springs, Bi, B2, EMF 270* SbO* (UVOUUTlON FIG. 18. press upon the segments, and convey the current generated in the coil to the external circuit E, as indicated. Upon a little consideration, it will be apparent that, if the springs are so placed that one segment slides out of contact as the other slides into contact with the brushes, at the moment the current is reversed in the coil, during certain periods of revolution, the current flowing in the external circuit will be " commutated," or will always flow in one direction, although the relative directions of XINIVERSITY PULSATING the current flowing in the revolving coil or loop will be unaffected. Pulsating Currents. Although the application of the commutator to the coil has the effect of causing the current to flow always in the same direction in the external circuit, it has no effect whatever upon the value of the E. M. F., or the strength of the current, during a complete revolution of the coil. This still remains as before, as will be seen by reference to Fig. 1 8, which represents the nature of the E. M. F. generated in the loop when fitted with a commutator. It will be seen that the current is a pulsating current, rising from zero to a maximum and then falling to zero again, but always flowing in one direction, as denoted by both curves being above the horizontal or zero line A B. Value of E. M. F. The electro-motive force set up in any conducting circuit by its motion in a magnetic field is proportional to the speed at which the conductor moves, and to the number of lines of force cut by the conductor, or E = S N. where E = Electro-motive force. S = Speed of conductor. N Number of lines of force. Hence, in order to increase the electro-motive force of the elementary form of dynamo illustrated above, we may increase either the speed of the coil or the number of lines of force threading through it, this latter being accomplished either by increasing the magnetising force applied to the electro magnet pro- ducing the magnetic field, or by winding the loop 36 THEORY OF THE DYNAMO. upon an iron core of suitable shape, thus reducing the magnetic resistance of the air space between the poles of the magnet. The E. M. F. may also evidently be increased by winding a greater number of turns or loops around the iron core, each being connected in series with the other, so that the E. M. F. of one is added to that of another, thus making the total E. M. F. of the coil equal to the sum of the E. M. F.s of each of the conductors or loops. The combination of the coil and iron core, when thus arranged, is called an "armature" and the electro magnet which creates the magnetic field in which the armature revolves is called the "field magnet;" and every dynamo consists essen- tially of these two parts, and of these two parts and a "commutator" when the dynamo is required to generate "direct" or "continuous" currents. Parts of Dynamo. The nature and uses of the different parts of a dynamo will be understood by reference to Fig. 19, which represents a complete machine. In this type of dynamo, as in the majority of continuous current dynamos, the mag- netic field is stationary whilst the armature revolves in it. The magnetic field in the particular dynamo illustrated is produced by the iron horse-shoe electro magnet M, which is excited by the current flowing in the magnetising coils E E. The ends or poles of the field magnet M are bored out so as to form a circular chamber within which the armature A rotates. This latter consists of an iron core rigidly fixed to a steel shaft or spindle S, which revolves in the two bearings F F. Upon one end of the shaft is fixed the driving pulley p. PARTS OF DYNAMO. 37 The iron core is overwound with a large number of insulated copper conductors or coils, the ends of which are connected to the circular commutator C. Two stationary metallic brushes, B B, press upon the latter, and convey the current generated in the coils of the armature through the flexible con- ductors or " leads," L L, to the terminals T T, from whence it is conveyed to the external or working FIG. 19. circuit. When the machine is in action, the arma- ture and conductors or coils are caused to rotate within the magnetic field, produced by the electro magnet M, by means of a belt passing over the pulley P. In consequence, E. M. F.s are induced in the conductors, which, on being commutated at the commutator, are transmitted through the medium of the brushes and flexible leads to the two ter- 38 THEORY OF THE DYNAMO. minals T T, giving rise to a difference of potential between the latter. This difference of potential may be wholly utilised for the purpose of supply- ing current to an external circuit, if a separate dynamo is used for exciting the field ; or the ends of the field coils may be connected to each of the terminals, when the machine .will supply current to its own field magnets. So long as merely an E. M. F. is acting in the armature, and no current is flowing in its conductors, these latter offer no resistance to the motion, and the only mechanical energy expended will be that necessary to over- come the resistance due to the friction of the bearings, &c. As soon, however, as current com- mences to flow in the conductors, a magnetic field is created around each (as represented in Fig. 9), and this, reacting on the magnetic field produced by the field magnet, exerts an attracting or re- pelling force, as the case may be, and thus tends to retard the rotation of the armature. In conse- quence, a greater amount of mechanical energy must be expended in keeping the armature rotating at its normal speed, the amount of energy so ex- pended being directly proportional, if the pressure is kept at a constant value, to the current flowing in the armature. CHAPTER IV. ARMATURES. THE elementary form of armature described in the preceding chapter (Fig. 17) possesses the disadvan- tage that the current generated in it by its motion in the magnetic field, though always flowing in one direction in the external circuit, is not absolutely con- tinuous, but is a pulsating current consisting of two sharp impulses to every revolution of the spindle. As these pulsations are evidently due to the coil moving alternately into and out of the positions of best and least actions in the magnetic field, it will be evident that if an additional coil is arranged at right angles to the existing coil, so that one coil is in the position of best action, whilst the other is in the position of least action in the magnetic field, the resulting current will be more nearly continuous. That such is the case will be seen by reference to Fig. 20, which represents the resultant curve due to such a combination of coils ; it will be seen that the crests of the curves are much closer together, and approach more nearly to the straight line, which would repre- sent the current if it were absolutely continuous. A little consideration will show that if we thus keep on arranging coils between the existing ones, a time will 40 ARMATURES. eventually be reached when the curves so overlap each other that they may be represented by a practi- cally straight line, when the resulting current will be, to all intents and purposes, continuous. It is upon this principle that the armatures in practical use are 180' FIG. 20. 270- constructed, a large number of coils being employed, suitably arranged upon an iron core, so that a large proportion of them are always actively cutting the lines of force, or moving in the positions of best action in the magnetic field. ' Types of Armatures. There are several different methods of arranging the coils upon the iron arma- ture, but the object of all of them is to obtain the practical continuity of the current. The types of armature in most extensive use at the present time are the following : The Ring or Gramme Armature, in which the coils are arranged upon an iron ring. The Drum or Siemens Armature, in which the coils are arranged upon the surface of an iron cylinder or drum. RING ARMATURE. 4! Each of these forms of armature has its special advantages, and in a general way it may be said that whilst the ring armature is more suitable for generat- ing small currents at high potentials, the drum is better adapted for producing moderate potentials and large currents. The Ring or Gramme Armature. The principle of this armature is shown diagrammatically in Fig. 21. An iron ring capable of revolving upon an axis is FIG. 21. arranged in the magnetic field between the poles N and S of an electro magnet. Upon this ring is wound a number of coils or loops of insulated copper 42 ARMATURES. wire, so as to cover the whole of the surface of the iron ring. The ends of each of the coils are con- nected to the ends of adjacent coils, so that a con- tinuous closed spiral is formed all round the ring ; and at the points where connection is made between the coils, connection is also made to strips of copper which are insulated from each other, and arranged around the axis of rotation into a circular com- mutator, as shown in the figure. Against the two strips situated at opposite ends of a diameter press two metallic brushes, Bi, B2, which, remaining stationary, serve to convey the current generated in the coils of the armature to the external circuit E. The arrangement of the lines of force in the magnetic field between the two poles N and s, when the ring is inserted therein, is shown by the dotted lines in Fig. 21. From this it will be seen that the lines of force issuing from the north pole pass by way of the armature core to the south pole of the magnet, one half of the lines passing through the upper portion of the core, and the other half passing through the lower portion of the core. Owing to this peculiar arrangement, a very intense magnetic field is created between the outer surface of the armature core and the polar faces, whilst the interior space within the core remains almost entirely free from lines of force. If the armature core be rotated in the direction of the arrow, the whole of the conductors, being immov- ably fixed to the core, must necessarily partake of the movement ; and therefore all the conductors arranged upon the exterior surface of the ring, moving in the magnetic field in the spaces between the outer sur- faces of the ring and the two polar faces, will cut the RING ARMATURE. 43 lines of force contained in this magnetic field, and therefore E. M. F.s will be generated in each of the conductors in consequence. The directions in which these E. M. F.s act, as found by Professor Fleming's rule, is indicated by the dots and crosses marked upon the conductors in Fig. 21. The dots represent the direction of the E. M. F.s when acting from back to front, and the crosses the direction when acting from front to back. As will be seen by this indica- tion, in the conductors moving in the left-hand space the E. M. F.s are directed from the back of the arma- ture to the front, whilst in all the conductors moving in the right-hand space the E. M. F.s are directed from the front to the back of the ring. As we saw in the elementary form of armature described in Chapter III., no E. M. F.s will be induced in the con- ductors moving in the spaces at the top and bottom of the ring between the two poles of the magnet, for these conductors are moving parallel to the lines of force, nor will any E. M. F.s be generated in the conductors arranged upon the interior surface of the armature, since these conductors are removed from the influence of the lines of force. These interior conductors, although inactive in the production of E. M. F.s, are essential however for the connection of the various active conductors one to another. The coils shown upon the ring in Fig. 21 being wound right-handedly, it follows that the E. M. F. induced in each of the conductors upon both sides of the ring will be added to that of the next above it ; con- sequently the E. M. F.s in all the conductors upon each side of the armature will be directed from the bottom to the top of the ring, which will therefore 44 ARMATURES. have a higher or positive potential, whilst the bottom of the ring will have a lower or negative potential, as indicated by the signs in the figure. It will be apparent that if the coils were wound left-handedly, just the reverse would take place, the E. M. F.s being all directed from the top to the bottom ; or the same thing would occur if the right-handed winding were retained, and the direction of rotation reversed. Since the total or resultant E. M. F.s of each side of the armature is equal to the sum of the E. M. F.s generated in each of the conductors arranged upon either side of the armature, it follows that if these latter are equal in number the resultant E. M. F.s will be equal and opposite ; and, consequently, if the external circuit is open, no current will flow in any portion of the windings, the E. M. F.s merely giving rise to a difference of potential between the top and bottom of the ring. If the external circuit is closed, the current which results will, owing to the two halves of the ring being in parallel, flow up the windings on each side of the ring to the top brush, and from thence through the external circuit to the bottom brush, and thus complete the circuit. The Drum or Siemens Armature. This type of armature differs essentially from the ring armature only in the manner in which the conductors are arranged upon the iron core. In the ring armature the core consists of a ring, and is overwound with conductors passing along the outer surface and through the interior ; in the drum armature, the core is in most cases a ring also, or may be regarded as a ring, and is overwound with conductors passing along the outer surface, but in place of passing through the DRUM ARMATURE. 45 interior the conductors are carried completely around it axially, in the manner represented in Fig. 22. This shows a drum arma- ture in perspective, upon which only two adjacent conductors or coils have been wound. Since the windings of the drum armature pass over the ends of the core, it is impossible to represent the whole of them in perspective, and there- FlG. 22. fore they are exhibited diagramatically in Fig. 23, which illustrates what is known as a right-handed 46 ARMATURES. winding, with eight-part commutator. In the figure shown, the windings are supposed to be viewed from the commutator or front end of the armature. The windings passing along the length of the drum are represented by the small circles, upon which are marked the dots and dashes denoting the direction of the E. M. F.s induced in the conductors, as in the ring armature. The connections passing across the back end of the drum are represented by the dotted lines, those upon the front end by the full lines. The manner in which the individual loops or coils are arranged and connected to each other and to the commutator, will be rendered clear by following the course of a single loop or coil upon the armature. Starting from the commutator segment (a), upon which the positive brush is resting at the upper portion of the armature, the conductor proceeds up the face of the drum to 6, thence along the top and across the back end to the lowest point of the drum, from whence it proceeds along the bottom of the drum to 15. From 15 the conductor is brought round the face of the drum and connected to the com- mutator segment (h\ next to the one from which it started. Another coil starts from the segment (//), and follows a similar course upon the surface of the armature, and is connected to the segment (g\ from which another coil starts, and so on all round the armature. A continuous closed spiral is thus formed all round the armature, in a somewhat similar manner to the ring armature. The arrangement of the lines of force in the magnetic field, when the armature is inserted therein, is similar to that of the ring arma- ture ; and with the armature rotating in the direction \ DRUM ARMATURE. 47 indicated by the arrow, it will be seen that the E. M. F.s and currents induced in the conductors, on either side of the armature, have the same relative directions as those induced in the conductors arranged upon the outer surface of the ring armature, the only difference being that the current flows across each end of the drum in place of flowing through the interior ; the conductors at the ends being thus the only idle portions of the winding in the drum arma- ture. With the particular winding shown in Fig. 23, i.e., a right-handed winding, the E. M. F.s will be directed from the bottom to the top of the armature, in a similar manner to the ring armature, the direc- tion of the E. M. F.s being reversed by reversing the 4 8 ARMATURES. direction of rotation, or by employing the left-handed winding shown in Fig. 24. Multipolar Ring and Drum Armatures. In practice it is found that although the ring and drum forms of armature, revolving in a bi-polar field, as described above, forms a most efficient arrangement for moderate outputs up to about 180 kilowatts, FIG. 25. when larger outputs are required from a single machine it is more economical to arrange the arma- ture in a field composed of 4, 6, 8 or more poles. In this case the conductors are arranged upon the sur- face of the ring and drum cores so as to form closed MULTIPOLAR RING ARMATURE. 49 spirals as before, the only difference being that the number of neutral points, or points of collection of the current upon the commutator, is increased in pro- portion to the number of poles ; and in the case of drum armatures, that the loops or coils span a smaller FIG. 26. proportion of the circumference of the armature. Referring to Fig. 25, which represents a ring armature rotating in a 4-pole field, it will be seen that the coils are arranged upon the core, and connected to the commutator in precisely the same manner as the bi- polar ring armature described above. The multipolar D 50 ARMATURES. armature, as shown, differs however in the fact that, when rotating, it produces two places at equal positive potentials and two places at equal negative potentials upon its commutator, at which the current may be collected, these points being indicated by the position of the brushes in the figure. To collect the current, the two brushes (A B) at equal positive potentials, and the two brushes (c D) at equal negative poten- tials, are connected together and to the external circuit, as represented. Another method of connecting, which necessitates the use of two brushes only, is illustrated in Fig. 26. In this arrangement, such bars of the commutator as are at the same potentials are connected together. In the case of a 4-pole arma- ture, each of the commutator bars are electrically connected to the one situated diametrically opposite, and the positions for the brushes are at right angles, as represented in Fig. 26 ; in a 6-pole armature, the three segments of the commutator, situated at 120 apart, are connected together, the brushes being placed 60 apart. Multipolar Drum Armatures. Figs. 27 and 28 represent diagramatically the windings of multipolar drum armatures when arranged in parallel and series groupings respectively. In the former grouping, the windings are arranged in as many parallels as there are poles ; in the 4-pole field illustrated, the armature is therefore equivalent to a pair of bi-polar drum arma- tures, each carrying half the total current. The same sequence of winding is used as in the bi-polar drum armatures (Figs. 23 and 24), the only difference being that the wires passing over the ends of the core span approximately only one-quarter in place of one-half MULTIPOLAR DRUM ARMATURE. 51 the circumference of the armature. In the series grouping (Fig. 28), the windings are arranged in two parallels, with any number of poles ; the total E. M. F. of the armature is therefore equal to the sum of the E. M. F.s induced in the conductors, arranged in series between the brushes as in the ordinary bi-polar drum FIG. 27. armature. Since in this grouping the windings are arranged in two parallels, it follows that two sets of brushes only are required, without any cross con- necting of the commutator. Their position upon the commutator varies with the number of poles ; when the field magnet consists of 4 poles, the brushes are placed 90 apart, or at right angles, asrepresented in OP THE tJNIVERSITT ARMATURES. Fig. 28 ; when consisting of 6 poles, the brushes are placed at opposite extremities of a diameter of the commutator as in bi-polar armatures ; and when con- sisting of 8 poles, they are placed 45 apart. FIG. 28. Position of Brushes on Commutator. In all dynamos, both bi- and multipolar, there are certain positions upon the commutator at which the brushes may be placed with a minimum of sparking. These positions are called the neutral points, and, as will be seen on examination of Figs. 21 to 28, the position of these neutral points varies with the type of field CAUSES OF SPARKING. 53 magnet and winding of armature. In ordinary bi- polar dynamos the neutral points lie at opposite ends of a diameter of the commutator, which diameter is called the neutral line. In most dynamos these neutral points do not occupy a fixed position upon the commutator, but vary their position from time to time as current is taken from the machine. When the armature is not supplying current to the external circuit, the neutral line, in bi-polar dynamos, occupies a position at about right angles to a line joining the middle of the pole pieces, or at right angles to the direction of the lines of force in the armature ; but as current is taken from the armature, the neutral line shifts round in the direction of rotation, when the brushes must also, be shifted round through a certain angle to the corresponding neutral points, if sparking at the brushes is to be avoided. The altered position of the brushes is known as the lead given to them, and the angle through which they are moved is known as the angle of lead. In all dynamos the lead is forward, or in the direction of rotation of the armature. Causes of Sparking. Sparking at the brushes of a dynamo is due to several causes, but mainly to the short-circuiting by the brushes of the armature coils while actively cutting the lines of force. An inspec- tion of Figs. 21 and 23 will show that the ends of each of the coils of the armature are connected to two adjacent segments of the commutator, and that each of the brushes is sufficiently broad to bear upon two bars of the commutator. Hence when each of the coils, during a certain period of the revolution, passes underneath the brushes, each will be momentarily short-circuited by the brushes bridging across the two 54 ARMATURES. segments to which the ends of the coils are connected. If this short-circuiting takes place while the brushes are on the neutral points, the coil will be moving mostly parallel to the lines of force, the E. M. F. acting in it will be almost zero, and, in consequence, no sparking will result. If however the brushes are shifted out of the neutral points, either to the right or left, the coil will be short-circuited whilst still actively cutting the lines of force, and an E. M. F. will con- sequently be acting in the coil. This E. M. F., though small, may produce a very large current, momentarily, owing to the very low resistance of the short-circuited coil. When therefore the short-circuit is opened by the rotation of the commutator, this current, owing to its property of "self-induction," or "electric inertia," does not immediately die out, but continues to flow across the gap for a brief interval, and expends its energy in the form of sparks, which rapidly wear away the commutator and brushes. Distortion of Magnetic Field. As soon as a dynamo commences to supply current to a circuit, a number of reactions between the armature and mag- netic field immediately takes place. The chiefest of these reactions is the distortion of the magnetic field, and consequent shifting of the neutral points. This distortion of the magnetic field is directly due to the fact that the armature, when working, becomes itself an electro magnet, the poles of which exert an attract- ing or repelling force upon the magnetic field. The nature of this armature magnetism will be understood by reference to Fig. 29. It will be seen that the currents generated in the windings on each side of the armature, by its motion in the magnetic field, are DISTORTION OF MAGNETIC FIELD. 55 flowing from the top to the bottom of the ring. On applying the rule given on page 21, it will be found that these currents tend to produce north and south poles on each half of the core at the points where the current enters and leaves the armature. There will thus be two north poles at the top of the ring, and FIG. 29. two south poles at the bottom ; but as these poles are adjacent to one another, the external effect will be equivalent to a single north and south pole situated at the top and bottom of the ring. The resultant effect of these two armature poles upon the magnetic field is to twist the line of force round into an oblique 50 ARMATURES. direction, as indicated in Fig. 30. Since in order to secure sparkless collection of the current, and to obtain the greatest difference of potential between the brushes, it is necessary to place these latter at points situated at right angles to the direction of the lines of force in the armature, this twisting of the lines neces- sarily involves the shifting of the brushes round the commutator in the direction of rotation, otherwise the armature coils will be short-circuited by the FIG. 30. brushes while actively cutting the lines of force, and considerable sparking at the brushes will result. Eddy Currents. Another very important reaction which occurs when the dynamo is working, is the production of eddy currents in different parts of the machine. This term is applied to the currents which are always produced when a solid metallic mass is rotated in a magnetic field, or is subjected to the EDDY CURRENTS. 57 action of a magnetic field which is undergoing change in its intensity or strength, for the reason that the currents generated always tend to flow in more or less circular paths. When produced in large solid metallic masses, the strength to which these eddy currents attain is frequently very considerable, owing to the low electrical resistance of the masses in which they flow ; and in addition to consuming a large amount of energy, they frequently occasion a large and dangerous rise in the temperature. The cores of armatures being made of iron, are, unless suitably constructed, subject to the detrimental influence of these eddy currents, as is also the case with the conductors wound upon the core if these are of large cross-sectional area. To entirely prevent the generation of these eddy currents is impossible ; they can, however, be prevented attain- ing any considerable strength, by suitably interposing resistance in their path. With this object, the cores and conductors of armatures are laminated^ or sub- divided into a number of small parts, each of which is electrically insulated from the other by some insulating material. CHAPTER V. ARMATURES IN PRACTICE. HAVING in the preceding chapter considered the principles and action of the two types of armatures at present in most extensive use, it now remains to describe briefly in detail the practical construction of such armatures. Armature Cores. The cores of all practical arma- tures are now invariably laminated, or constructed of iron wire, ribbon, or discs. This method of construc- tion is adopted in order to minimise as far as possible the generation of eddy currents, which otherwise, if the core were constructed of solid iron, would attain considerable and even dangerous proportions. Disc Armature Cores. The cores of all large armatures of the ring and drum types are as a rule built up of iron discs ; when small, however, they are frequently constructed of iron wire. The discs are stamped out of thin sheet-iron of about -%$ of an inch in thickness, with a hole in the centre of each disc sufficiently large to accommodate the shaft and driving spokes, and also the conductors in the case of ring armatures. In most cases notches or keyways are stamped on the inner periphery of ARMATURE CORES. 59 the discs (as in Fig. 31), to fit over the driving spokes, or over feathers running along the length of the shaft. These thin discs are then se- parated by some insulating material, and clamped between two thicker end discs or flanges so as to form a solid cylinder or drum. In this mode of construction the iron core, whilst carrying out its primary function of conducting the lines of force from pole to pole of the field magnet, interposes such considerable resistance in the path of the eddy currents as to effectually prevent these latter attaining any appreciable strength. Toothed Cores. Ring and drum armature cores are frequently constructed with deep channels or grooves in the outer periphery, in which the con- ductors are wound. The projections or teeth in this method of construction present an excellent means of driving and protecting the conductors, but the difficulty of insulating the latter from the core is increased by their use, and they also have a tendency to produce eddy currents in the pole pieces of the field magnets, causing a heat- ing of the latter. The FIG. 32. latter disadvantage can, however, be obviated to a great extent by making the teeth very narrow and numerous. When the 6o ARMATURES IN PRACTICE. toothed type of core is used, the discs are stamped out with projections or teeth at regular intervals around the periphery (Fig. 32), and clamped together so that the projections and interspaces form con- tinuous ridges and channels around the periphery, along the length of the core, for the reception of the conductors. Insulation of Core Discs. In order to prevent the circulation of any considerable eddy currents within the core, the core discs are electrically in- sulated from one another. Owing, however, to the very low E. M. F. of the currents, the insulation required is very slight ; some manufacturers separate each disc by a paper or mica disc of similar form to the iron disc ; others merely varnish the discs with shellac or other varnish, and this slight insulation is found to be quite effective in the prevention of dangerous eddy currents. Driving Spokes and Spiders. In most armatures the driving spoke or spider wheel serves a double FIG. 33. purpose, (a) to firmly clamp the core discs together so as to form a solid core ; (^) to firmly fix the core to the shaft. The method generally followed in clamp- VENTILATION OF ARMATURES. 6l ing and holding ring armature cores is illustrated in Fig- 33- The spiders or stars are of gun-metal, and are two in number, each having four arms or spokes, with end projections against which the thicker end flanges fit. The core discs are stamped with four notches or slots on their inner periphery, and the arms of the spiders engage in these and prevent the discs turning. The spiders fit over the shaft, and are prevented from turning thereon by feathers. One of the spiders fits against a shoulder turned upon the shaft, and the core discs are strongly compressed between this and the other spider by means of lock- FlG. 34. nuts turning upon threads cut upon the shaft. All well-constructed ring armatures are now provided with these driving spokes or spiders, but they are frequently dispensed with in drum armatures, the core discs themselves being keyed on to the shaft. In such cases the discs are clamped between two end plates, one of which is secured by a shoulder turned upon the shaft, and the other by a screw-nut and lock-nut, as shown in Fig. 34. Ventilation of Armatures. The cores of all armatures are liable to become heated through the generation of eddy currents, the transmission of the 62 ARMATURES IN PRACTICE. heat from the conductors, and other causes. In small armatures no special means are taken to get rid of this heat, the relatively large amount of surface ex- posed, and the high initial velocity of such armatures, being found sufficient to prevent any dangerous rise of temperature. In the case of large armatures, how- ever, some means of ventilation must be adopted, otherwise the armature will heat up to a dangerous extent. The method generally followed in such armatures is to cause air currents to circulate among the conductors and in the interior of the core. For this purpose the conductors are wound with air spaces between them, and cooling gaps are frequently left at intervals between the core discs. When the core discs are fixed direct on to the shaft, they are fre- quently punched with holes, so that when assembled upon the shaft continuous ventilating apertures are formed in the core, through which the air circulates and carries off any excess heat. Drivers. When a current is flowing in the con- ductors of an armature revolving in a magnetic field, the magnetic attractions and repulsions set up have a tendency to displace the conductors and drag them out of their places around the core. Means must therefore be taken to resist this injurious action, and to fix the conductors immovably to the core. In small armatures, where the displacing forces are relatively very small, simple friction is generally relied on to effect the purpose, the grip of the con- ductors upon the core, reinforced by the pressure of the binding wires, being found quite sufficient to hold the conductors in their places. In the case of large armatures, however, where the displacing force upon CONDUCTORS. 63 each conductor may amount to many pounds, some more positive means of driving the conductors must be adopted ; with this object the cores of such armatures are generally provided with drivers of metal or other substance. These drivers are arranged and fixed to the core in a variety of ways ; in some cases they consist of steel or other metal pins in- sulated with vulcanised fibre, and screwed or driven into the core for a certain distance, so that they stand up level with the conductors ; or strips of wood or fibre are arranged longitudinally along the surface of the core, being screwed to the latter, or let into grooves milled or planed in the surface of the core. Either of these forms of drivers, in conjunction with the binding wires, forms a most effective means of driving the conductors, and entirely prevent any slip of the latter over the core. Conductors. In all practical armatures the con- ductors are invariably of copper, although iron has been suggested for the purpose at different times. For small currents they are generally of circular section, and wound in two or more layers upon the surface of the core ; but for heavy currents they are always of rectangular or trapezoidal section, in order to economise the space around the periphery of the armature to the greatest extent. In both cases they are insulated with silk, or a double layer of cotton braided on and varnished with shellac or rubber varnish. Laminated Conductors. When the cross sec- tional area of the active conductors of an armature exceed a certain limit, there is great liability for eddy currents to be generated within them. To 64 ARMATURES IN . PRACTICE. prevent this occurring, many makers employ lami- nated conductors, or conductors formed of stranded copper wires. In Messrs Crompton's patent stranded armature conductors, the separate strands are var- nished or oxidised, or otherwise lightly insulated from each other, and then compressed into a bar of FIG. 35- rectangular or trapezoidal section, as shown in Fig. 35. These stranded armature bars are very effectual in the prevention of eddy currents and the accompany- ing waste of energy, Messrs Crompton having found that by their use in large armatures the efficiency of the dynamos is increased as much as 3 or 4 per cent Connectors. When the size or section of the con- ductors of drum armatures exceeds a certain limit, considerable difficulty is experienced in the winding, in bending and arranging the conductors over the ends of the drum or core, and in such armatures connectors are therefore generally employed. These connectors, as their name implies, are used for the purpose of connecting the conductors situated at opposite sides of the core together. They consist of flexible strips or stampings of thin sheet-copper, insulated with tape or other suitable material, and arranged at either ends of the core. They take a variety of forms or shapes, but the arrangements due nCTNIVI PT HOPKINSON AR^fittfeS! 6 5 to Hopkinson and Kapp appear to be most exten- sively used in practice. Dr Hopkinson's method of arranging the connectors is shown in Fig. 36. The conductors of the armature are rectangular in section, and project over the ends of the core for a longer or shorter distance alternately, as shown in the side view Fig. 36. Two commutator-like structures A A, con- sisting of a number of copper segments S S, insulated from each other, and fixed upon a wooden drum, are arranged at either end of the core, and into saw-cuts tfln.npr.toF FIG. 36 in each of these segments are soldered two thin strips of copper, c C, insulated with tape. These thin copper strips are bent in opposite directions (as shown in end view Fig. 36), and their ends are soldered into the long and short armature conductors situated at approximately opposite ends of a diameter of the core, as shown in the end view of Fig. 36. At the commutator end of the armature the copper segments are continued outwards, and connected to the com- mutator segments, as represented in the side view Fig. 36. In the system due to Mr Kapp, each of the E 66 ARMATURES IN PRACTICE. connectors consists of a stamping of thin sheet-copper of semi-circular form, shown in Fig. 37, with a tag at either end. The connectors are insulated with var- nished tape, and are built up on a cast-iron bobbin or FIG. 37- clamp, B B, fixed at either end of the armature core D. The conductors are arranged to project over the ends of the core for a longer and shorter distance alternately, as in the Hopkinson armature, and the tags of each connector are bent over, at right angles to the con- nector but in opposite directions, and soldered to the projecting ends of the long and short armature bars situated at approximately opposite ends of a diameter. At the commutator end of the armature the long bars are extended for a greater distance over the end of the core, and soldered to the lugs of the commutator, as shown in sectional view of armature Fig. 37. A com- plete drum armature, fitted with Kapp end connectors, is depicted in Fig. 38. In addition to the better mechanical construction, and ease in winding the conductors, secured by their use, these connectors offer two other important advantages, viz., (a) the end connectors can be much better insulated than is the KAPP ARMATURE. 67 case with the wires passing over the ends of wire wound armatures, and as conductors at great diffe- rences of potential are not brought near to each other, short circuiting between adjacent conductors is greatly minimised ; (b) the repair of the armature FIG. 38. is also greatly facilitated, for owing to the con- ductors and connectors being entirely distinct, if a conductor becomes damaged at any time it can be unsoldered from its connectors and a new conductor soldered into its place, without disconnecting or re- moving any other portion of the winding. Binding Wires. The conductors of an armature, in addition to being subjected to the peripheral drag exerted by the magnetic field, are also subjected to the influence of the centrifugal force developed by the rotation of the armature. As most armatures are driven at a high peripheral speed, this force is often considerable ; therefore, in order to counteract the 68 ARMATURES IN PRACTICE. tendency of the conductors to be driven off by the action of this force, they are bound down to the core by means of bands of binding wires. These binding wires are usually of steel, hard brass, or phosphor- bronze, wound under tension upon bands of vulcanised fibre and mica, fixed upon the periphery of the armature, and soldered at intervals to obviate flying asunder. The Commutator. The commutator as a rule is built up separately from the armature, and consists of a number of segmental bars of brass, copper, or phosphor-bronze, insulated from each other, and fixed in a clamping sleeve which slides over and is made fast to the shaft. Construction of Commutators. The construction of commutators is illustrated by the example given FIG. 39. in Fig. 39, which represents the Kapp commutator. Two views of this commutator are given, the upper CONSTRUCTION OF COMMUTATORS. 69 half in each case being shown in section. The seg- ments B are of hard drawn copper, insulated from each other by slips of mica, M. Square clamping notches, N, are turned in the ends of the assembled bars, into which fit grooved rings of hard vulcanised fibre. These rings have a coned surface, and are cut into three segments so as to permit of slight contraction. A gun-metal bush or sleeve, G, having a cone turned upon one end, slides over the shaft S, and is pre- vented from turning thereon by the pin P. A tubular nut, T, screws on to one end of the bush, and over this slides a loose coned collar, C. The two gun- metal cones fit into the grooves in the fibre rings, and when forced together by the screw-nut T on the end of the sleeve, binds the whole of the segments firmly together. The electrical connection of the segments of the commutator to the coils of the armature is effected by means of the lugs L. These are made of thin strip copper, of a suitable length, to connect the ends of the armature coils to the segments of the commutator. A saw-cut is made in one end of each of the segments, and one end of the lug is soldered or sweated into this, the other end being bent round and soldered to the projecting ends, E, of the armature coils, as represented in the sectional view of the commutator. Brushes. The brushes bear upon the commutator, and make sliding contact with the armature and working circuits. It is needful that they should have a certain amount of flexibility, in order that they may accommodate themselves to any little inequality which may occur upon the surface of the commutator, and also to avoid cutting or scoring the latter ; with 70 ARMATURES IN PRACTICE these objects, they are usually made of copper or brass gauze, wire, or flexible strip. Gauze Brushes. This type of brush is now very extensively used, owing to its great flexibility and soft and yielding nature, resulting in decreased wear of the commutator. It is made up of a sheet of copper gauze, folded round several times, with the wires running in an oblique direction, so as to form a FIG. 40. solid flat strip of from J inch to J inch in thickness, as shown at A, Fig. 40, the thickness increasing with the volume of the current to be collected. The object of folding the gauze up with the wires running in an oblique direction is to prevent the ends of the brushes fraying or threading out, which would be the case if the gauze was folded up in any other manner. Wire Brushes. This brush (B, Fig. 40), which was much used previous to the invention of the gauze brush, is made up of a bundle of brass or copper wires, laid side by side and soldered together at one end. Being harder than the gauze brush, it is more liable to cut or score the commutator, and it is also more troublesome to trim. BRUSHES. 71 Strip Brush. This is probably the simplest form of brush, but is not very extensively used owing to its lack of flexibility. It consists of a number of strips of copper or brass, laid one upon the other and soldered at one end, as in c, Fig. 40. Carbon Brushes. When metallic brushes are used upon the commutators of high tension machines, they frequently give rise to excessive sparking, and also heating of the armature, the metallic dust given off appearing to lodge between the segments of the com- mutator, thus partially short circuiting the armature. To obviate this, carbon brushes are frequently used on such dynamos, this substance being found very effectual in the prevention of sparking. The brushes are usually in the form of oblong blocks placed " butt " end on the commutator, and fed forward as they wear away by means of a spring holder. Brush Holders. In order to secure sparkless collection of the current, and to prevent undue wear FIG. 41 of the commutator, it is needful that the pressure of the brushes upon the latter should be capable of being adjusted to meet requirempatSTgTfcalso need- " OF THE JNIVERSITY ARMATURES IN PRACTICE. ful that they should be capable of being fed forward as required, as they wear away, and that they be furnished with a movement to permit of the brushes being raised from contact with the commutator when necessary. Each maker has his own particular ar- rangement for giving these essential motions to the brushes, and, as may be conceived, they frequently differ widely. The requirements of a good brush- holder are met in a very efficient manner in the Newton-Hawkins patent brush-holder, illustrated in Fig. 41. A pair of the brush-holders mounted complete on the arms of the rocker is shown in Fig. 42. The holder consists of two parts the tail-piece T fixed immovably to the arm of the brush-rocker by means of the small set- screw D, and the mov- able brush clamp A capable of revolving through a small angle on the fixed tail-piece. Contact pressure of the brush is produced by the laminated plate-spring S (shown more clearly in Fig. 42), the tension of which is adjusted by means of a regulating screw and lock-nut R. The brush is held up from contact with the commutator by means of the hold-off catch c, composed of a vulcanised fibre cam turning on a pivot. The brush can be fed FIG. 42. BRUSH HOLDERS. 73 forward in the holder, or drawn back and adjusted, while the machine is running, by unscrewing the clamping-screw H and adjusting the regulating-screw E. The brush is connected to the terminals of the machine by means of a flexible "lead," bolted to the point P of the holder. In all well-designed dynamos not less than two brushes are used on each side of the commutator ; this allows of either brush being removed, and examined and trimmed, while the machine is running. It also allows of the brushes being adjusted upon the commutator independently of each other, any uneven wear of the commutator being thus prevented, and better contact made. Brush Rockers. As previously mentioned, when a dynamo is working, the neutral points, or the points upon the commutator where sparkless collection of the current can be made, vary in position as the load upon the dynamos varies, moving round in the direc- tion of rotation as the load increases, and vice versa. It is necessary therefore, in order to avoid sparking, to shift the brushes bodily upon the commutator from time to time, without in any way altering the ad- justments of the brush-holder springs or breaking the working circuit. To enable this to be effected the brushes with their holders are, in ordinary bi-polar dynamos, usually fixed upon a "rocker" or "yoke." Fig. 43 illustrates the form of rocker commonly used. It is of cast-iron or gun-metal, made in two pieces and bolted together. The central aperture is turned out to fit into a groove turned in one end of the bearing next to the commutator, and the rocker, when rotated by means of the handle A into the correct position for the brushes upon the commutator, is clamped in 74 ARMATURES IN PRACTICE. position by the clamping-screw s. Through holes at opposite ends of the bar project two gun-metal spindles, M M, upon which the brush-holders are FIG. 43. firmly fixed by the set-screws (D, Fig. 41). These spindles are entirely insulated from the rocker bar and from each other by the vulcanised fibre bushes and washers w w. CHAPTER VI. FIELD MAGNETS. THE field magnet, the function of which is to produce an intense magnetic field within which the armature revolves, may be either a permanent magnet or an electro magnet. Electro magnets, however, possess such a number of important advantages over perma- nent magnets, that they are now invariably used in all machines intended for practical work. The chief- est advantages of the electro magnet, as compared with the permanent magnet, lies in the power of regulating the strength of the magnetic field pro- duced by the former, by suitably adjusting the strength of the magnetising current flowing through its coils, and also in the greater magnetic effect obtained, weight for weight, from the electro magnet over the permanent magnet. Excitation of Field Magnets. The field magnets of a dynamo may be excited, either by the current furnished by an independent dynamo or battery, in which case the machine is said to be "separately excited" or by the current generated in the armature of the machine of which the field magnet forms part, when the machine is said to be self-excited. 76 FIELD MAGNETS. Self-Excitation. The latter type of machine depends for its action upon the presence of residual magnetism in its field magnet. Owing to this re- sidual magnetism, a weak magnetic field is always present between the pole pieces of a field magnet ; hence, when the armature is rotated in the armature chamber, its conductors cut the lines of force con- tained in this magnetic field, and a small E.M.F. is set up in the armature in consequence. The ends of the magnetising coils being suitably connected to the brushes, if these latter are in contact with the commutator, and a closed circuit through the field magnet windings is formed, this small E.M.F. immediately sends a minute current through the ex- citing coils; this immediately increases the strength of the magnetic field, and as a consequence an in- creased E. M. F. is induced in the armature. This results in a stronger current being sent through the exciting coils, and the increase of magnetism which follows results in an increased E.M.F. in the armature. Thus the process goes on, until eventually, for a given speed of rotation of the armature, the E.M.F. reaches a maximum value, beyond which it will not increase without a further increase in the speed of rotation ; the exciting current has then arrived at a constant value, and the magnetisation of the machine will remain at a constant strength, and maintain the E. M. F. so long as the armature rotates at its normal speed. If the armature ceases to revolve, the field magnets will of course be deprived of their exciting current, and will therefore lose their magnetism ; the iron will, however, retain a sufficient amount of residual magnetism to again start the SELF-EXCITATION. 77 process when the machine is again started. In most cases an appreciable time elapses before the voltage arrives at its maximum value : in small dynamos, a few seconds generally suffices to fully excite the machine; in the case of large shunt dynamos, it may require a minute, or even five minutes in exceptional cases. Classification of Dynamos. The manner in which the coils of the field magnets are connected to the armatures of self-exciting machines gives rise to the following classification : (1) Series Wound Dynamos. In which the coils of the field magnet are connected in series with the armature and external circuit (2) Shunt Wound Dynamos. In which the coils of the field magnet form a shunt to the armature and external circuits, and, being composed of many turns of fine wire, absorb only a fraction of the total current. (3) Compound Wound Dynamos. Wherein two coils are wound upon the field magnets, arranged in a combination of shunt and series : one coil being wound with a large number of turns of fine wire, and connected as a shunt to the armature ; the other being composed of a few turns of thick wire, and connected in series with the armature. Separately Excited Dynamos. This type of machine is not so extensively used as the self- exciting type, owing principally to the fact that an independent dynamo or battery is necessary for exciting its field magnet. It finds its chiefest appli- cation in the electric transmission of power, and in charging accumulators, and in all cases where a high 78 FIELD MAGNETS. E. M. F. is required with a varying current. The connections of this dynamo are shown in Fig. 44, where N S are the poles of an electro magnet, which is excited by the current generated by the independent dynamo or battery D. The armature A revolves in the space between the two pole pieces, and the two brushes B : B 2 press upon the com- FlG. 44- mutator C, and convey the current generated in the armature to the external circuit E. The E.M.F. and output of the dynamo is usually regulated by varying the strength of the magnetising current (produced by the dynamo or battery D) flowing in SERIES the coils of the field magnet by means of the hand- regulator R. Series Dynamos. The manner in which the connections of the series wound dynamo are arranged is shown in Fig. 45. The coils of the field magnet are wound with a few turns of thick insulated wire, FIG. 45- and being joined in series with the armature, the whole of the current generated in the latter passes direct through them, and thence to the external circuit. The current in passing through the coils of the field magnet energises the latter, and creates a magnetic field between the two poles N s, in which 8O FIELD MAGNETS. the armature revolves. A little consideration will show that the strength of this magnetic field, and therefore the E. M. F. of the machine, will vary in direct proportion to the current flowing in the ex- ternal circuit, since the current flowing in the external circuit is also the magnetising current. If the ex- ternal current is " open," no current will flow therein, and therefore the field magnets will be unexcited, and the only magnetic field will be that due to the residual magnetism of the field magnets ; the E. M. F. of the machine will, therefore, be practically nil. If, on the other hand, the external circuit is closed, so as to offer a minimum resistance, or " short cir- cuited," the field magnet will be excited to the greatest extent, and the E.M.F., and current flowing in the external circuit, will be approximately a maximum. Characteristic Curves. The behaviour of series wound and other dynamos can best be studied graphically by means of "characteristic curves" As Prof. S. P. Thompson remarks,* "the charac- teristic curve stands to the dynamo in a relation very similar to that in which the indicator-diagram stands to the steam-engine. As the mechanical engineer by looking at the indicator-diagram of a steam-engine can at once form an idea of the qualities of the engine, so the electrical engineer by looking at the characteristic of the dynamo can judge of the qualities and performance of the dynamo." The shape or form of the characteristic curve differs, of course, with the type of dynamo * "Dynamo Electric Machinery," Spon, 1892. CHARACTERISTIC OF SERIES DYNAMOS. 8l whose qualities it represents, the form of the charac- teristic of a series dynamo being entirely different from that of a shunt or compound wound machine. The characteristic of a series dynamo is given in Fig. 46. The abscissae measured horizontally re- present the number of amperes flowing in the circuit ; and the ordinates, shown vertically, the corresponding value of the terminal E.M.F., the armature rotating 20 40 60 80 100 120 140 AMPS FIG. 46. at a constant speed. It will be noticed that the curve does not begin exactly at the point o, but a little way up the vertical line ; this indicates the existence of a small E.M.F. before current is taken from, the machine, and is due to the residual magnetism of the field magnets. As current is taken from the machine, the magnetisation of the field magnets increases at first, very rapidly with the current ; and therefore the F 82 FIELD MAGNETS. electro-motive force increases also, giving the first portion of the curve. After a time, however, the cores of the field magnet become saturated ; the curve then attains a maximum height, at A ; and as more current is taken from the armature, the de-magnetising action of the latter, and the fall of pressure over the resist- ances of the machine, increase so rapidly, that the E. M. F. at the terminals of the machine is decreased, as indicated by the curve bending downwards. Series wound dynamos are chiefly used for lighting arc lamps in series, and for the electric transmission of power over long distances, and for other purposes where a high potential is required. Shunt Wound Dynamos. The shunt wound dynamo differs from the series wound machine, in that an independent circuit is used for exciting its field magnet. This circuit is composed of a large number of turns of fine insulated copper wire, which are wound round the field magnet and connected to the brushes, so as to form a shunt or " by pass " to the brushes and external circuit. Fig. 47 shows the connections of the shunt wound dynamo, from which it will be seen that two paths are presented to the current as it leaves the armature, between which it divides in the inverse ratio of the resistance ; whilst one part of the current flows through the magnetising coils, the other portion flows through the external circuit. In all well designed shunt dynamos, the resistance of the shunt circuit is always very great, as compared with the resistance of the armature and external circuit, and the strength of the current flowing in the shunt coils rarely exceeds 12 amperes in even the largest machines. SHUNT DYNAMOS. 83 Characteristic of Shunt Dynamo. The general form of the characteristic curve obtained from a shunt wound dynamo is illustrated in Fig. 48. The ordinates shown vertically represent the volts at the terminals of the machine, the abscissae the amperes flowing in the external circuit, with the FIG. 47. armature running at a constant speed. Starting with the external circuit open, the only current flowing is that in the shunt coils of the field magnet, which latter is consequently magnetised to the greatest extent, and therefore the E. M. F. at the terminals of the machine is at a maximum i 8 4 FIELD MAGNETS. value. When the external circuit is closed, as current is taken from the armature, the loss of volts over the resistance of the latter increases VOLTS 140 120 100 80 bO 40 20 AMPS 20 FIG. 48. bO 80 100 as more and -more current is taken from the machine. Hence the pressure at the brushes is reduced, and this resulting in a decrease of the CHARACTERISTIC OF SHUNT DYNAMOS. 85 magnetising current, the curve begins to fall gradu- ally downwards, until when the point A is reached the voltage has been so far reduced that the machine commences to de-magnetise or "build down," and the voltage then runs down to zero. The shunt dynamo is therefore only capable of supplying a definite maximum current, beyond which, if the resistance of the external circuit is still further reduced, the machine will de-magnetise, and cease to generate current at all. The behaviour of the shunt dynamo is thus in many respects the reverse of the series wound machine : in the latter, the E. M. F. is greatest when the current flowing in the external circuit is a maximum; in the former, the E. M. F. is a minimum under like circumstances. Owing to its non-liability to reversal of polarity, the shunt wound dynamo is extensively used for charg- ing accumulators, and for electrolytic and electro- metallurgical work, and also in central stations for the supply of electrical energy. Compound Wound Dynamos. In practice, elec- tric lamps, motors, and other applications of electrical power, are constructed for a definite pressure and current, which must be maintained constant if the appliances are to work efficiently. In incandescent lighting, where the lamps are arranged in parallel, a constant voltage must be maintained between the terminals of the lamps, no matter how few or how many are burning. Under such circumstances it will be evident that simple shunt or series wound machines would be quite unsuitable, for the pressure would vary with every variation of the current as the lamps are switched into or out of circuit. For 86 FIELD MAGNETS. the purpose of automatically maintaining a con- stant pressure in incandescent lighting, the compound wound dynamo (Fig. 49) is now generally employed. The field magnet of this dynamo is wound with two sets of coils, one set being connected in series, and the other set in parallel, with the armature and FIG. 49. external circuits. The machine is in reality a com- bination of the shunt and series wound machines, and from what has been already stated regarding the behaviour of these types of dynamos, the action of the compound dynamo will be apparent. When the external circuit is open, and no load is therefore COMPOUND DYNAMOS. 8/ on the dynamo, the shunt coil will maintain the E.M.F. at the terminals at the correct value; as the load increases, the fall of pressure at the terminals of FIG. 50. the machine, due to the loss of volts over the arma- ture resistances, and the reduced current in the shunt coils, will be compensated by the increase of induced 88 FIELD MAGNETS. E. M. F. in the armature, due to the increase of ex- citing power furnished by the series coils ; and if the series and shunt coils are correctly proportioned, the E. M. F. at the terminals of the dynamo will be maintained constant throughout the entire range of the machine. This is, however, only true when the dynamo is run at the speed for which it was designed ; at any other speed the windings will not compensate each other, and the voltage will not remain constant with a varying load. Short and Long Shunt Compound Winding. The method of connecting the coils of compound dynamos, represented in Fig. 49, in which the ends of the shunt coils are connected directly to the brushes, is known as the short shunt winding. Another method, shown in Fig. 50, in which the shunt is placed across the terminals, is known as the long shunt winding. Theoretically, the latter method is preferable, as being the most efficient; in practice, however, the gain is not very appreciable, and the former method is generally used. CHAPTER VII. FIELD MAGNETS IN PRACTICE. WHILST the construction of the armatures of different dynamos may be said to be very much the same, differing in small details only, and being confined to two types, viz., the ring and drum respectively, the construction of the field magnets varies greatly, almost every manufacturer having his own particular form and arrangement. This great variety in the form of the field magnets of different dynamos, is due in a large measure to considerations of economy involved in the manufacture by different makers, and also, to a less extent, to the different conditions under which a machine is required to work. For example, it is sometimes necessary for a machine to give a maximum of output with a minimum of weight, and under such circumstances the field magnet is con- structed wholly of wrought-iron, and this necessarily entails an entirely different method of construction and arrangement than if cast-iron were employed. Again, as a rule, the direct coupling of the arma- ture to the engine-shaft involves a different form of field magnet than would be the case if the armature were belt driven. 90 FIELD MAGNETS IN PRACTICE. Construction of Field Magnets. Owing to dif- ficulties of construction, and other considerations, field magnets are not in practice usually constructed out of a single piece of iron, but are usually built up of a combination of parts, and composed either wholly of wrought or cast iron, or of a combination of both. The construction of a typical field magnet is illus- trated in Fig. 51, from which it will be seen that it may be divided into five parts, viz. : the two limbs or cores M M, upon which the exciting coils c are wound ; the two end portions P P, called the " pole pieces," which are bored out so as to form the " armature chamber " within which the armature revolves ; and the yoke, Y, which serves to connect the two limbs together, and thus complete the magnetic circuit. The permeability of wrought-iron being very much greater than cast-iron, the portions M M of the field magnet, upon which the exciting coils are wound, are frequently constructed of this material ; these portions are also usually constructed of a circular section, and thus the amount of wire required for exciting the field magnet is economised to the utmost extent The pole pieces P P and the yoke Y are in many cases of cast-iron, bolted on to the wrought-iron limbs. Forms of Field Magnets. Although innumer- able forms of field magnets have been devised, they can all be arranged into two groups, viz., those in which the poles are " salient," and those CONSTRUCTION OF FIELD MAGNETS. 91 in which the poles are " consequent." A salient pole is the term applied to poles which are pro- duced at the ends of a bar of iron, in distinction to consequent poles, which are produced in a con- tinuous ring of iron. Salient Pole Field Magnets. The salient pole form of field magnet, being least costly to con- struct, is most frequently met with in practice. FIG. 52. Fig. 52 shows its simplest form : in this arrange- ment only one magnetising coil is required, this being wound upon the yoke, which is usually of wrought-iron, let into and bolted to the cast-iron pole pieces N S. The paths and directions of the lines of force, with the magnetising current flowing in the direction shown, is indicated by the dotted arrow heads and lines. Another form of field mag- net which is very extensively used, and in which two exciting coils are required, is shown in Fig. 53. In this type the limbs are usually of wrought-iron, 92 FIELD MAGNETS IN PRACTICE. of rectangular section, bolted to the bedplate of the machine, which therefore forms the yoke of the magnet. The magnetising coils are wound upon bobbins, which are slipped over the limbs, being held in place by the cast-iron " horns " c C, screwed on at the lower portion of the armature chamber. FIG. 53. The form of field magnet illustrated in Fig. 53 is known as the " overtype " ; when the armature is placed below the field coils and yoke, as repre- sented in Fig. 54, the arrangement becomes the " undertype." This latter type is very extensively used in large dynamos, owing to the low centre of SALIENT POLE FIELD MAGNETS. 93 gravity of the revolving armature resulting in in- creased stability and freedom from vibration ; it is also invariably employed when the armature is to be coupled direct to the engine crank-shaft. In most cases the whole of the field magnet is com- FIG. 54. posed of wrought-iron, the two limbs being formed of rectangular slabs bolted to the yoke. As a rule, this class of field magnet is supported upon a bedplate of cast-iron, and therefore it is necessary to magnetically separate its pole pieces therefrom, otherwise they will be magnetically short circuited, 94 FIELD MAGNETS IN PRACTICE. or the lines of force will flow through the bedplate in place of passing through the armature core. To effect this the pole pieces are supported at a suit- able distance from the bedplate by " footsteps," S S, or brackets of zinc, brass, or other non- magnetic substance. Consequent Pole Field Magnets. The two leading types of consequent pole field magnets are illustrated in Figs. 55 and 56. The paths and direc- tions of the lines of force in the field and armature FIG. 55- cores are indicated, as before, by the dotted arrow- heads and lines. Fig. 55, which represents the " Manchester " type of field magnet, may be looked upon as a double magnet, the exciting coils being wound upon what may be regarded as the yokes of the magnets. The directions of the electric current flowing in the magnetising coils are such that two similar poles are produced in each pole piece. In Fig. 56 two similar poles are produced in each pole CONSEQUENT POLE FIELD MAGNETS. 95 piece as in the " Manchester " type, but four exciting coils are necessary, these being wound upon the limbs FIG. 56. of the magnet, and connected up in a suitable manner to produce the requisite polarity in the pole pieces. Multipolar Field Magnets. These generally con- sist of 4, 6, 8, or more poles, arranged in alternate FIG. 57. order around the armature. They may be arranged into two classes, according as the poles are salient or consequent poles. Fig. 57 illustrates the type of mul- tipolar field magnet employed by Messrs, Crompton 9 6 FIELD MAGNETS IN PRACTICE. in their large dynamos. As will be seen, it consists of two separate and distinct magnets arranged horizontally, and supported by gun-metal brackets upon a cast-iron bedplate. The direction of the current in the magnetising coils is such that two north and two south poles are produced in alternate FIG. 58. order around the armature. Fig. 58 represents a very commonly used type of multipolar field magnet ; it consists of a ring of iron, having four pole pieces pro- jecting inwardly, over which the exciting coils are slipped, the ring forming a common yoke for all the poles. As a rule, it is made in two portions, bolted together horizontally, so that the upper portion may FIELD MAGNET WINDINGS. 97 be lifted off for examination of the armature. Fig. 59 is given as an example of the consequent pole type of multipolar field magnet. The magnet cores are of wrought-iron, bolted on to wrought-iron pole pieces, the magnetising coils being coupled up so as to pro- duce consequent poles of alternate polarity around the armature. Field Magnet Windings. The insulated wires used for the excitation of the field magnets, not being subjected to any of the detrimental influences experienced by the armature conductors, are in most cases of solid copper. As a rule, the wires are wound upon insulated spools, which are afterwards slipped OF THE UNIVERSITY 98 FIELD MAGNETS IN PRACTICE. over the limbs of the magnet ; in some cases, how- ever, they are wound direct upon the core of the field magnet, this latter being previously insulated with vulcanised fibre or other insulating material. In general, the wires used for the exciting coils of shunt wound dynamos are very thin ; hence when this is used for making connection to the terminals of the machine, it is very liable to break off near the flanges of the reel upon which it is wound. Several plans are adopted to prevent this occurring : in some cases the ends of the shunt coils are soldered to stouter wires within the flanges of the bobbins, these wires being afterwards connected to the terminals of the machine ; in other cases, the ends of the coils are soldered to large terminals fixed upon the flanges of the bobbins, these terminals being afterwards suitably connected together by strips of copper. Coupling up Field Magnet Coils. In coupling up the exciting coils of dynamo field magnets, the primary essential is to so arrange the connections of the coils that the magnetising current flowing through them produces the requisite polarity in the respective pole pieces. In those field magnets provided with a single coil only (as in Fig. 52), no mistake can obvi- ously be made ; when two or more coils are used, however, it is possible to so arrange the connections that poles are produced in the yokes or other portions of salient pole field magnets ; or in the case of conse- quent pole field magnets, the connections may even be so arranged that the coils neutralise each other, and no external field whatever is produced. The manner in which the coils of the various types of salient and consequent pole field magnets are coupled -' CONNECTING UP DYNAMOS. 99 up, will be apparent from inspection of Figs. 52 to 59; but in order to still further facilitate the coupling up of field coils the following rule is given : Practical Rule for Coupling up Field Magnet Coils. In coupling up the coils of either salient or consequent pole field magnet coils, assume each of the pole pieces to have a certain polarity (in bi-polar dynamos two poles only, a north and south pole respectively, are required ; in multipolar dynamos the poles must be arranged in alternate order around the armature, the number of N and S poles being equal), then apply the rule given on page 21 to each of the coils, and ascertain the direction in which the magnetising current must flow in each in order to produce the assumed polarity in each of the pole pieces. Having marked these directions on the coils, the coils can be coupled up in either series or parallel according to requirements, so that the current flows in the necessary direction in each. Connecting up Dynamos. The manner in which the connections of the field magnet coils, and brushes, and terminals, are connected to one another, depends entirely upon the class of dynamo. The field magnet shunt coils of shunt and compound wound dynamos, are invariably arranged in series with one another, and then connected as a shunt to the brushes or terminals of the machine, as represented in Figs. 47, 49, and 50. The series coils of series and compound wound machines, are arranged either in series or in parallel with one another, according to circumstances, and the amount of current given by the machine, and then con- connected in series to the armature and external circuits upon the principle shown in Figs. 45, 49, and 50. CHAPTER VIII. REGULATING DYNAMOS. IN the practical operation of dynamos, some means of regulating their output are always needed, so that either the voltage or the current may be maintained at a constant value, or varied as required. The out- put of a dynamo may be regulated or varied by any of the following methods, or by a combination of the same: (-1) Variation of speed of armature. (2) Varia- tion of strength of magnetic field. (3) Variation of position of brushes on commutator. (4) Variation of resistance in dynamo circuit. The application of these methods of regulation to the various classes of dynamos is considered in the succeeding paragraphs. Regulating Separately Excited Dynamos. As previously mentioned (p. 78), the voltage and output of this class of machine is most commonly governed by varying the strength of the magnetising current flow- ing through its field magnet coils. When the mag- netising current is furnished by a battery or accumu- lator, this is effected either by means of a hard regulator or rheostat inserted in the exciting circuit (as represented in Fig. 44), or by varying the number of cells in circuit, this latter being the most REGULATING SEPARATELY EXCITED DYNAMOS. IOI economical plan. In most cases, however, a smaller dynamo is used for the purpose. In this case the strength of the magnetising current flowing in the coils of the main dynamo may be regulated by either of two methods : (a) by means of a hand regulator inserted in the field circuit as before; or (ft) by varying the voltage of the smaller exciting dynamo. This latter may be effected either by varying the speed of the armature, or by varying the strength of the magnetic field, by regulating the strength of the magnetising current flowing in the field coils by means of a hand regulator. When several separately excited dynamos are running together, it is a common practice to employ a smaller exciting dynamo for the exclusive purpose of supplying the magnetising cur- rent required for the field magnets of the several dynamos. The system of regulation then adopted depends upon whether the dynamos are supplying a common circuit, or running in parallel, or supplying independent circuits. The conditions of working in the former case require that the voltage of all the machines shall be varied simultaneously, and therefore the method of regulation, by varying the voltage of the smaller exciting dynamo, may be used with advantage. In the latter case, however, since each machine supplies an independent circuit, the voltages of which may vary greatly, such a method is obviously not applicable, for any variation of current will affect all the dynamos in common. It is therefore usual in such cases to provide the field circuit of each individual dynamo with a hand regulator, so that its pressure may be adjusted independently of the others. 102 REGULATING DYNAMOS. Hand Regulators. These, when applied to the regulation of dynamos, consist of multiple contact switches, so arranged that either the resistance of the field magnet circuit may be varied, by inserting or removing resistance in series with the latter, or one or more of the exciting coils may be cut into or out of circuit, or short circuited. When arranged for performing the former operation, the regulator is usually combined with a set of resistance coils, a combination of this description being illustrated in Fig. 60. It consists of two cast-iron end frames, rigidly connected to- gether by means of two iron rods bolted into the ends of the frames. The two end frames are hollow, and each contain a slate slab, securely fixed in place by means of screws or bolts passing through the slabs, and screwing into the iron frames. The projecting edges of the slate slabs are provided FlG - 6o - with a number of brass studs or bolts, on to which are fixed the ends of spiral coils of German silver, platinoid, or iron wire. These spiral coils are all joined in series, being formed of a continuous length of wire, which passes up and down between the slate slabs. The connections of the spiral coils to the external circuit are made by means of two ter- minals, and a number of contacts fixed in the slate slab, in the bottom end frame. The terminal shown on the left of the figure is connected to the extreme left HAND REGULATORS. 103 hand spiral coil, the terminal on the right being con- nected to the lever of the multiple contact switch or regulator, shown at the bottom of the figure. This is composed of twelve contacts, each contact being electrically connected to the bottom junction of a spiral coil. By altering the position of the lever of the regulator the coils can be cut in or out of circuit, and the resistance varied, as may be required. When the regulator is arranged for performing the latter operation, the switch is not combined with a resist- ance, but the exciting coils of the field magnets are divided up into groups, and the ends are connected to the contacts or terminals in place of the resistance coils, so that by varying the position of the lever each of the exciting coils may be cut into or out of circuit, and the strength of the magnetic field adjusted accordingly. Regulating Series Dynamos. The series dynamo is ordinarily used for operating series arc lamp cir- cuits, and for the electric transmission of power, its regulation being effected by any of the following methods : (1) Variation of strength of magnetic field. (2) Variation of speed of armature. (3) Variation of position of brushes on commutator. (i.) Regulation by Variation of Strength of Mag- netic Field. Although theoretically there are several different methods of varying the strength of the magnetic field of a series dynamo, in practice, the method of shunting the exciting current in the field coils is invariably followed. The essential principle of this method consists in establishing a shunt of variable resistance across the field coils, so that a 104 REGULATING DYNAMOS. portion of the armature current is shunted through the resistance, the remainder being used for exciting the field magnets. The strength of the magnetic field being proportional (within certain limits) to the strength of the magnetising current flowing in the exciting coils, it follows that the E. M. F. of the machine will vary in proportion to the resistance of the shunt. By reducing the resistance of the latter, a larger proportion of the total current will flow through it, and the strength of the current flowing in the field coils being thus reduced, the voltage of the machine will be reduced also, or vice versa. The alteration in the resistance of the shunt can be effected by hand, with the aid of a rheostat or hand regulator, similar in principle to that represented in Fig. 60. When used for this purpose, however, the hand regulator is usually so arranged that all the resistance coils can be cut out of circuit, and the field coils short-circuited, thus allowing of the voltage of the machine being adjusted from zero to the maximum value. Automatic Regulation. In cases where an ap- proximately constant current is to be maintained in a circuit, as in series arc circuits, the adjustment of the resistance of the variable shunt is, as a rule, effected automatically by means of some electro- magnetic device, actuated by solonoids placed in the main circuit. Brush's Automatic Regulator. The automatic regulator invented and used by Brush for the purpose of maintaining a constant current in an arc circuit is shown diagramatically in Fig. 61. The current leaving the positive brush of the dynamo (D) divides at the junction of the field magnet coils (F M) and AUTOMATIC REGULATION. 105 the shunt (s) part, passing through the former, and part through the latter. Included in the shunt circuit (s) is a variable resistance (c) composed of a pile of carbon slabs or blocks, arranged one upon another in a press in such a manner that the current passing in the shunt must pass from one block to another. These slabs, when pressed together, conduct well ; but FIG. 61. when the pressure is diminished, their imperfect con- tact greatly increases the resistance of the shunt. Hence, when the lever and armature (L) is raised or lowered by the action of the current flowing in the solenoid or electro-magnet (E), which is included in the main circuit, the pressure on the slabs is increased or diminished, and the resistance of the shunt varied in proportion. If now some of the lamps be cut out IO6 REGULATING DYNAMOS. of circuit by short-circuiting them, the resistance of the circuit will be diminished, and there will be a tendency for the current to increase above its normal value. This increase of current will cause the solo- noid (s) to attract the lever (L) with greater force, resulting in an increase of pressure on the carbon slabs, and a diminution of the resistance of the shunt. As a consequence, a larger proportion of the total current flowing will be shunted across the field coils, and the magnetic field being thus weakened, the E. M. F. of the machine will be correspondingly reduced, and the current thus maintained at its normal value. Regulation by Variation of Speed of Arma- ture. The voltage and output of series dynamos can be governed to some extent by varying the speed of the armature, by opening or closing the stop-valve of the steam engine, or other motor driving the dynamo. This method of regulation is, however, only applicable in cases where the fluctuations of the load are small, since it involves constant attendance on the engine. Electric Governor. To obviate this constant at- tention to the engine when this system of regulation is adopted, an electric governor is frequently em- ployed. One of the best known types of electric governor is that of Richardson, manufactured by Messrs Robey & Co., Lincoln. This governor may be used for maintaining either a constant pressure, or a constant current in a circuit, and is shown fitted to a steam engine in Fig. 62. The governor consists of a solenoid (E), the cores of which are attached to the end of a lever (L), the short end of which presses through the medium of a plunger (p), direct upon the ELECTRIC GOVERNOR. 107 IO8 REGULATING DYNAMOS. stalk of a double-beat cornish valve. The valve fits freely into its seat, and works almost without friction. It is, however, so arranged that the steam gives it a constant pressure upwards. This is balanced at the other end by a spring, and as the leverage is six to one, the spring only needs to exert a sixth of the pressure. There are therefore two forces acting in contrary directions, and nearly balancing each other, and when an electric current is sent through the coils of the solonoid (E), which, when intended for main- taining a constant current, are included in the main circuit, the cores are drawn further in, and the valves partially closed. The parts are so balanced and adjusted that the slightest change in the strength of the current is at once felt and responded to by the engine, and the speed of the armature adjusted to suit the work being done. As an additional pre- caution, a separate small electro-magnet (E M) is included in the circuit of the solonoid, which, when the current is flowing therein, holds up the iron block (B). If from any cause the circuit is broken, the block (B) falls, and instantly cuts off the steam, thus stopping the engine. Regulation by Variation of Position of Brushes on Commutator. In both ring and drum armatures, when rotating in a bi-polar field, there are two points situated at opposite extremities of a diameter of the commutator, at one of which the potential is a maxi- mum, and at the other a minimum, and it is at these points that the brushes must be placed, in order to obtain the greatest difference of pressure. From the point of maximum potential to the point of minimum potential either way round the commutator, the REGULATING SHUNT DYNAMOS. IO9 pressure gradually decreases in value. Hence, if the brushes make contact at points on the commutator other than the neutral points or points of highest and lowest potential, the pressure between the brushes will vary in proportion to their distance from the neutral points, increasing as they approach the neutral points, and decreasing as they recede from them, until when making contact at points situated at about 90 from the neutral points, they will be at nearly the same potential. From this it follows that by merely rocking the brushes round the commutator, the pressure at the terminals of the machine may be varied and regulated as required. Such a method of regulation cannot, however, be used with advantage in ordinary dynamos, owing to the very destructive sparking which takes place at the brushes when they are moved any considerable distance from the neu- tral points. Special dynamos have been designed, notably by Statter, to meet the special requirements of this method of regulation, and in which the spark- ing at the brushes is obviated at all loads within the range of the machine, but as these have not come into general use they need not be further considered here. Regulation of Shunt Dynamos. In parallel incan- descent lighting, it is absolutely necessary to maintain the pressure at the lamps at a constant value. When the lamps are situated at a considerable distance from the machine, as in town lighting, this necessi- tates a constantly varying pressure at the machine in order to make up for the fall of pressure in the mains connecting the machine to the lamps, which fall is dependent on the amount of current flowing 10 REGULATING DYNAMOS. in the mains. The ease with which this variation of pressure can be effected in the shunt dynamo causes this class of machine to be ordinarily used in cen- tral stations for incandescent lighting, the regulation being effected by either of the following methods, or by both in conjunction, (i) Variation of strength of magnetising current. (2) Variation of speed of armature. (i.) Regulation by Variation of Strength of Magnetising Current. This is the only thoroughly efficient method of regulation for a shunt dynamo. FIG. 63. The variation in the strength of the magnetising current is effected by means of a hand regulator or rheostat, similar to that represented in Fig. 60, which is inserted in the shunt circuit of the machine, as shown diagramatically in Fig. 63. In this system of regulation, the resistances of the field magnet shunt REGULATING SHUNT DYNAMOS. Ill windings and of the regulator coils are so propor- tioned, that, when no load is on the dynamo, and all the coils of the regulator are in circuit with the shunt, the machine generates the normal pressure required at the lamps. As more and more lamps are switched on, the voltage at the lamps has a tendency to decrease, and therefore the pressure at the machine must be raised in proportion. This is effected by moving the lever of the regulator (R), so that fewer resistance coils are included in the shunt circuit ; the resistance of the latter being thus decreased, the exciting current and voltage of the machine is in- creased correspondingly. This method of regulation is common with all in which resistances are included in the circuit, wastes energy to a certain extent, but the quantity so wasted is so small in proportion to the whole that it may be considered as of little moment, especially when the advantages of the system are taken into account. It is possible, of course, to use this method in conjunction with regula- tion by means of the engine stop-valve (the stop- valve being used for large variations of pressure, and the hand regulator for small variations), but the advan- tages of the system are so few that in the generality of cases the hand regulator is solely relied on to cope with any variations in the load. The engines are then so arranged that they can be run entirely upon their governors, these being so adjusted as to merely prevent the engine racing in case of the load being suddenly taken off the machine, through a short circuit, or other breakdown, the stop-valves being fully opened as soon as the machines have taken the load. 112 REGULATING DYNAMOS. Regulation by Variation of Speed of Arma- ture. A much less satisfactory method of regulation for shunt dynamos is that of varying the speed of the armature. For small variations of pressure, the alteration of speed can be readily effected by means of an adjustable governor, the speed of the armature being varied by increasing or diminishing the tension of the governor spring, according to the pressure required at the terminals of the machine. For larger variations, however, the only effective method of regulation is by means of the stop-valve, that is to say, the main stop-valves of the engines are opened or closed in proportion to the pressure required. When a number of dynamos are running in parallel, the disadvantages of this system, as compared with the method of varying the strength of the magnetic field, become especially prominent, since, in place of a number of easily adjusted hand regulators, fixed in some central position, and operated by a single attendant, this method involves the regulation being effected by probably as many men as there are engines, each regulating the stop-valve of a particular engine. Furthermore, the regulation is not nearly so effective, owing to the difficulty of expeditiously adjusting the valves to give the pressure required. In connection with this particular system of regula- tion, a special type of voltmeter is generally employed, this being of extraordinary large dimensions, with the index or pointer about 18 inches in length, so that its indications may be seen all over the engine- room. Regulating 1 Compound Dynamos. A carefully compounded dynamo will, when run at the speed for REGULATING COMPOU which it was designed, regulate itself perfectly, and maintain a constant difference of potential at its terminals under any variation of load within its range. In practice, however, it is not always possible to work a dynamo under these exact conditions, and, more- over, in the case of large machines, the effect of temperature upon the resistance of the machine has an appreciable effect upon the voltage. Means for regulating the latter are therefore desirable. The voltage may be varied to a certain extent by suitably adjusting the governor of the driving engine, increasing or decreasing the speed ; but in many cases this is not very desirable or possible, and a much better method of obtaining the desired variation of voltage is to insert a variable resistance or hand regulator in the shunt circuit of the machine, the resistance of the shunt being suitably proportioned to give the requisite margin for regulation. Regulating Over-Compounded Dynamos. It is sometimes desirable, as in central light and power stations, to have a dynamo which will maintain a constant pressure at a point some distance from the machine. In this case the dynamo is over-com- pounded, or the series coils are wound with a greater number of turns, in order to raise the pressure at the terminals of the machine as the load increases, and thus compensate for the fall of pressure in the mains. As it is frequently necessary to vary the degree of over-compounding, the series coils of such dynamos are usually so proportioned as to give from 10 per cent, to 20 per cent, of over-compounding, and a strip or ribbon of German silver or copper is arranged as a shunt to the series coils. By suitably including a H 114 REGULATING DYNAMOS. greater or lesser length of ribbon in the circuit, the resistance of the variable shunt and the amount of current flowing in the series coils can be varied, and the percentage of over-compounding adjusted accordingly. CHAPTER IX. COUPLING DYNAMOS. WHEN it is needful to generate a large and variable amount of electrical energy, as is the case in large installations and central generating stations, apart from the question of liability to breakdown, it is neither < economical nor desirable that the whole of the energy should be furnished from a single dynamo. Since the efficiency of a dynamo is dependent upon its output at any moment, or the load at which it is worked, the efficiency varying from 95 per cent, at full load to 80 per cent, at half load, it is obviously advisable in order to secure the greatest economy in working to operate any dynamo as far as possible at full load. Under the above circumstances, when the whole of the output is generated by a single dynamo this can evidently not be effected, for the load will naturally fluctuate up and down during the working hours, as the lamps, motors, &c., are switched into and out of circuit ; and hence, although the dynamo may be working at full load during a certain portion of the day, at other times it may probably be work- ing below half load, and therefore the efficiency and economy in working in such an arrangement is very Il6 COUPLING DYNAMOS. low. In order to secure a maximum efficiency, it is usual in such cases to divide up the generating plant into a number of units, varying in size, so that as the load fluctuates it can either be shifted from one dynamo to another as the exigencies of the case requires ; or when the load exceeds the capacity of the largest dynamo in the plant, the output of one can be added to that of another, and thus the dynamos actually at work at any moment can be operated as nearly as possible at full load. As it is necessary to take certain precautions in connecting one dynamo to another, in order that the other dynamos may not be effected by the change, and that they may work satisfactorily together, it is well to consider these in connection with the different types of machines. Series and Parallel Connections. Since the out- put of a dynamo is made up of two factors, viz., the pressure and the current respectively, it follows that the output of a machine may be increased by increas- ing either the one or the other, or both at the same time. As however the systems of distribution in use at the present time involve the maintenance of either a constant current or a constant pressure in a circuit, the -methods of coupling dynamos together resolve themselves into two kinds, corresponding to the systems of distribution, viz., parallel and series con- nections. In coupling two or more machines in parallel, the pressures of all the machines are kept at a constant value, while the output of the plant is increased in proportion to the current capacities of the machines in circuit. In the series coupling, the current capacity of the plant is kept at a constant SERIES AND PARALLEL CONNECTIONS. 117 value, while the output is increased in proportion to the pressures of the machines in oircuit. Shunt Dynamos in Series. The simplest opera- tion in connection with the coupling of dynamos, and the one used probably more frequently in practice than any other, is the coupling of two Il8 COUPLING DYNAMOS. or more shunt dynamos to run either in series or in parallel. When, connected in series, the positive terminal of one machine is joined to the negative of the other, and the two outer terminals are connected through the ammeter A, fuses F x F 2 , and switch S, to the two main conductors or omnibus bars as represented in Fig. 64. The machine will operate when the connections are arranged in this manner, if the ends of the shunt coils are connected to the terminals of the respective machines ; but a better plan is to put both the coils in series with one another, so that they form one long shunt between the two main conductors, as shown in Fig. 64. When arranged in this way, the regulation of both machines may be effected simultaneously by inserting a hand regulator (R) in series with the shunt circuit, as represented. Shunt Dynamos in Parallel. The coupling of two or more shunt dynamos to run in parallel is effected without any difficulty, and is probably an operation more frequently performed than any other, it being daily practised in central generating stations on the low tension system. Fig. 65 illustrates dia- gramatically the method of arranging the connec- tions. The positive and negative terminals of each machine are connected respectively to two massive insulated copper bars, shown at the top of the dia- gram, and called omnibus bars, through the double pole switches S x S 2 , and the double pole fuses F x F 2 . Ammeters, A 1 A 2) are inserted in the main circuit of each machine, and serve to indicate the amount of current generated by each. An automatic switch or cutout, ACjACg, is also shown as being included in SHUNT DYNAMOS IN PARALLEL. 119 the main circuit of each of the machines, although this appliance is sometimes dispensed with. The pressure of each of the machines is regulated inde- pendently by means of the hand regulators RjRg, inserted in series with the shunt circuit. The shunt circuits are represented as being connected to the positive and negative terminals of the respective I2O COUPLING DYNAMOS. machines, but in many cases, where the load is sub- jected to sudden variations, and when a large number of machines are connected to the bus bars, the shunt coils are frequently connected direct to these ; and in such circumstances this method is preferable, as by means of it the fields of the idle dynamos can be excited almost at once direct from the bus bars by the current from the working dynamos, and hence if a heavy load should come on suddenly, no time need be lost in building up a new machine previous to switching it into parallel. The pressure of the lamp circuit is given by a voltmeter, whose terminals are placed across the omnibus bars ; and the pressure at the terminals of each of the machines is indicated by separate voltmeters or pilot lamps, the terminals of which are connected to those of the respective machines. Switching Dynamo into and out of Parallel. In order to put an additional dynamo into parallel with those already working, it is necessary to run the new dynamo up to full speed, and, where it excites, regulate the pressure by means of a hand regulator until the voltmeter connected to the terminals of the machines registers one or two volts more than the voltmeter connected to the lamp circuit, and then close the switch. The load upon the machine can then be adjusted to correspond with that upon the other machines by means of the hand regulator. In this class of machine there is little or no danger of overloading an armature when connecting it to the bus bars, and therefore the pressure need not be adjusted with very great accuracy ; in fact, it is common practice in central stations to judge of the SHUNT DYNAMOS IN PARALLEL. 121 voltage of the new dynamo merely by the appearance of its pilot lamp. When shutting down a machine, the load or current must first be reduced, by gradually closing the stop-valve of the engine, or inserting resistance into the shunt circuit by means of the hand regulator ; then when the ammeter indicates nine or ten amperes, the main switch is opened, and the engine stopped. By following this plan, the heavy sparking at the switch contacts is avoided, and the tendency for the engine to race reduced. Great care, however, has to be taken that the current is not reduced too far, or otherwise there is a risk of the machine being stopped, receiving a back current from the other dynamos, resulting in heavy sparking at the commutator, and in the machine being driven as a motor. To obviate this danger, and to render these precautions needless, shunt dynamos when running in parallel are frequently provided with automatic cutouts, set so as to automatically switch out the machine when the current falls below a certain minimum value. Dividing Load. If a plant composed of shunt dynamos running in parallel be subjected to varia- tions of load, gradual or instantaneous, the dynamos will, if they all have similar characteristics, each take up an equal share of the load ; if, however, as is some- times the case, the characteristics of the dynamos are dissimilar, the load will not be shared equally; the dynamos with the most drooping characteristics taking less than their share with an increase of load, and more than their share with a decrease of load. If the difference is slight, it may readily be com- pensated by means of the hand regulator increasing 122 COUPLING DYNAMOS. or decreasing the pressures of the machines, as the load varies or fluctuates. If, however, the difference is considerable, and the fluctuations of load very rapid, it becomes practically impossible to evenly divide the load by this means so that each dynamo takes up its proper share of the work. Under such circumstances, the pressure at the bus bars is liable to great variations, and there is also great liability for the fuses of the overloaded dynamos to be blown, thus precipitating a general breakdown. To cause an equal division of the load amongst all the dynamos, under such circumstances, it is needful to insert a small resistance in the armature circuits of such dynamos as possess the straightest charac- teristics, or of such dynamos as take more than their share of an increase of load. By suitably adjusting or proportioning the resistances, the pressures at the terminals of all the machines may be made to vary equally under all variations of load, and each of the machines will then take up its proper share of the load. Automatic Cutouts. Shunt and other dynamos are always liable when working to have the pressure at their terminals reduced, either through a fault in the armature or field circuits, or through a hot bearing or other cause. When a number of shunt dynamos are running in parallel, and the pressure of one falls below that of the others, the load is trans- ferred from the machine having the lower pressure to the machine with the higher pressure, until when the pressure falls below a certain minimum value a reverse current is sent through the armature of the machine whose pressure has been reduced by the SHUNT DYNAMOS IN PARALLEL. I2 3 machines having the higher pressure. This results in the machine being driven as a motor, and in great sparking at the commutators of all the dynamos, and also in an overload of the driving dynamos, and pro- bably in the blowing out of all the fuses. -In order to prevent this occurring, shunt dynamos when running in parallel are each as a rule provided with an auto- matic switch, placed between one or both of the machine terminals and the omnibus bars, whose duty it is to switch off automatically the machine in the event of a reduc- tion of its voltage from any of the above - mentioned causes. The prin- ciple and action of this instrument will be understood by reference to Fig. 66, which re- presents the form manufactured and used for this purpose by Messrs Crompton & Co. Briefly described, the instrument consists of an electro-magnet, fixed upon a slate base, and shown in the upper portion of the figure ; and an iron armature fixed to the ends of the pivoted levers of the switch, shown in the lower portion of the figure. The electro-magnet is included in series with the FIG. 66. 124 COUPLING DYNAMOS. switch and armature circuit, and while the pressure of the machine to which the instrument is connected remains at its normal value, the current flowing in its coils is sufficiently strong to enable it to hold up the iron armature against its pole pieces. If from any cause the voltage of the machine is reduced, the current flowing in its armature is decreased also, until when it falls below a certain minimum value at which the automatic switch is arranged to act, the strength of the electro - magnet has been so far diminished that it can no longer hold up the arma- ture against the weight of the levers, and these latter therefore drop and switch the machine out of circuit. A fusible cutout is shown in the centre of the figure, which, when the current exceeds the safe capacity of the machine, melts, and cuts out the armature, thus saving it from destruction. Coupling Series Dynamos in Series. Series wound dynamos will run satisfactorily together with- out special precautions when coupled in series, if the connections are arranged as in Fig. 67. The positive terminal of one dynamo is connected to the negative terminal of the other, and the two outer terminals are connected directly to the two main conductors or bus bars through the ammeter A, fuse F, and switch s. If it be desired to regulate the pressure and output of the machines, variable resistances, or hand regulators R! R 2 , may be arranged as shunts to the series coils, as represented, so as to divert a portion or the whole of the current therefrom. Series Dynamos in Parallel. Simple series wound dynamos not being well adapted for the purpose of maintaining a constant pressure, are seldom in SERIES DYNAMOS IN SERIES. 125 practice coupled in parallel ; the conditions of work- ing, however, derive importance from the fact that compound dynamos, being provided with series coils, are subject to similar conditions when working in parallel, which is frequently the case. In coupling two or more plain series dynamos in parallel, the 126 COUPLING DYNAMOS. same procedure cannot be followed as in the case of plain shunt dynamos, for the reason that if the voltage of the new dynamo is exactly equal to that of the bus bars when connected in parallel, the combination will be unstable. If from any cause the pressure at the terminals of one of the dynamos falls below that of the others, it immediately takes a smaller propor- tion of the load ; as a consequence, the current in its field coils is at once reduced, and a further fall of pressure immediately takes place owing to this circumstance. This increased fall of pressure again causes the dynamo to relinquish a portion of its load, and again occurs a further fall of pressure. Thus the process goes on, until finally the dynamo ceases to supply current, and the current from the other dynamos flowing in its field coils in the reverse direction reverses its magnetism, and causes it to run as a motor against the driving power in the opposite direction to that in which it previously ran as a dynamo. Under such circumstances the arma- ture is liable to be destroyed if the fuse is not immediately blown, and in any case is subjected to a very detrimental shock. This tendency to reversal in series dynamos can be effectually prevented by the simple expedient of connecting the field coils of all the dynamos in parallel, as was first suggested by Gramme. This is effected in practice by connecting the ends of all the series coils where they join on to the armature circuit by a third connection, called the " equalising connection," or " equaliser," as shown in Fig. 68. The immediate effect of this equalising connection is to cause the whole of the current gene- rated by the plant to be divided among the series SERIES DYNAMOS IN PARALLEL. TJNIVERSITT 128 COUPLING DYNAMOS. coils of the several dynamos in the inverse ratio of their resistance, without any regard as to whether this current comes from one armature, or is divided among the whole. The fields of the several dynamos being thus maintained constant, or at any rate caused to vary equally, the tendency for the pressure of one dynamo to fall below that of the others is much diminished, reversal of polarity is entirely obviated, and the machines will run together under all con- ditions of load. Coupling Compound Dynamos in Series. Since compound dynamos may be regarded as a combina- tion of the shunt and series wound machines, and as no special difficulties are experienced in running these latter in series, analogy at once leads to the conclusion that compound dynamos under similar circumstances may be coupled together with equal facility. This is found to be the case in practice, it being only necessary, in order that two compound dynamos may run satisfactorily together in series, to connect the series coils of each together, as repre- sented in Fig. 67 ; the shunt windings must be con- nected as a single shunt, as in Fig. 64, which may either extend simply across the outer brushes of the machines, so as to form a double short shunt, or may be a shunt to the bus bars or external circuit, so as to form a double long shunt. Compound Dynamos in Parallel. Compound dynamos will not run satisfactorily together in parallel, unless all their series coils are connected together by an equalising connection, as in series dynamos. Two methods of arranging the connec- tions are adopted in practice, these being illustrated COMPOUND DYNAMOS IN PARALLEL. I2 9 in Figs. 69 and 70. Either of these methods is satisfactory, but that shown in Fig. 70 is preferable, as by means of it the idle machines are completely disconnected from those at work. The same re- ference letters are common in both diagrams S t S 2 SERIES COILS Si SERJtS COILS SHWT COLS -AAMM/W FIG. 69. are switches ; F 1 F 2 fuses ; A t A 2 are ammeters, which indicate the total amount of current generated by each of the machines ; AC X AC 2 are automatic switches, arranged for automatically switching out a machine in the event of the pressure at its terminals being reduced through any cause ; R x R 2 I 130 COUPLING DYNAMOS. are hand regulators, inserted in the shunt circuits of each of the machines, by means of which the pressures of the individual machines may be varied and the load upon each adjusted. The pressure at the bus bars is given by the voltmeter V, one vwvwvw FIG. 70. terminal of which is connected to each of the bars ; a second voltmeter may be used, to give the pressure of any individual machine, by connecting " voltmeter keys " to the terminals of each of the machines, or a separate voltmeter may be used for each individual machine. The only essential difference between the COMPOUND DYNAMOS IN PARALLEL. two diagrams is, that in Fig. 69 the equaliser is con- nected direct to the positive brushes of all the dynamos, whilst in Fig. 70 the equaliser is brought up to the switchboard and arranged between the two bus bars, a switch being fitted for disconnecting it from the circuit when the machine to which it is connected is not working. In connection with this latter arrange- ment the form of switch shown in Fig. 71 is gene- rally used. This consists of three contacts, insulated from each other, and fixed upon a slate base ; the two contacts at the sides are respectively connected to the positive and nega- tive conductors, while the central contact is con- nected to the equaliser. The circuits are opened or closed simultaneously by means of three levers, which are forced between the contacts by the handle. These levers are each pro- vided with removable knife FI G- contacts for taking the spark at breaking contact, and are insulated from each other, and rigidly fixed upon a spindle which is capable of a small angular movement in the bearings, shown in the lower part of the figure. Switching Dynamo into and out of Parallel. If the characteristics of all the dynamos are similar, and the connections are arranged as in either Figs. 69 or 70, the only precaution to be observed in switching a new machine into parallel is to have its voltage equal, or nearly equal, to that of the bus bars previous to closing the switch. If this is the case, the 132 COUPLING DYNAMOS. new machine will instantly take up its due share of the load without disturbance or shock of any kind. If a dynamo is to be cut out of circuit, it will first be necessary to reduce the load to a few amperes, as in the case of shunt dynamos, either by easing down the engine, or by cutting resistance into the shunt circuit by means of the hand regulator, and then open the switch. Previous to this, however, it is advisable to increase the voltage at the bus bars to a slight extent, as while slowing down the engine the load upon the outgoing dynamo is transferred to the other dynamo armatures, and the current in their series coils not being increased in proportion the voltage at the bus bars is consequently reduced somewhat. Dividing Load. When a number of compound dynamos of different outputs, size, or make are running together in parallel, it frequently happens that all their characteristics are not exactly similar, and therefore the load is unequally distributed amongst them, some being overloaded, whilst others do not take up their proper share of the work. If the difference is small, it may be compensated by means of the hand regulator ; if large, however, other means must be taken to cause the machines to take up their due proportion of the load. If the series coils of the several dynamos are provided with small adjustable resistances, in the form of german silver or copper ribbon inserted in series with the coils, the distribution of the current in the latter may be altered by varying the resistance attached to the individual coils, and thus the effect of the series coils upon the individual armatures in raising the pressure may be adjusted, and the load thus evenly divided among the machines. CHAPTER X. RUNNING DYNAMOS. Dynamo Foundations. The first essential for success in dynamo running is to have the machine firmly and securely fixed upon a good and sound foundation ; for no dynamo, however well constructed and managed, will run well unless this is the case, the vibration engendered by a bad foundation resulting in sparking at the brushes, and in other evils which greatly tend to reduce the life of the commutator and other parts of the machine. It is also advisable, if the machine is belt or rope driven, to mount it upon a sliding bedplate provided with brackets and tightening screws for aligning and adjusting the ten- sion of the belt while the machine is running. The foundation may be of wood, stone, brick, or concrete. Wood, as a rule, is only used in making foundations of a temporary character, the other materials being used for more permanent foundations. Brick or Stone Foundations. In making either brick, stone, or concrete foundations, the excavation should be carried far enough down to secure a good bottom. The foundation, if of brick or stone, should be built up in cement to a suitable height, and a large flat stone cemented on the top. In the case of small 134 RUNNING DYNAMOS. dynamos, it will only be necessary to carry the holes for the holding-down bolts from 6 to 8 inches into the foundation. With large dynamos, however, the holes should be carried as far down as possible, and the holding-down plates, of wrought or cast iron, built in. Underneath each of the plates hand holes should be made, so that the cotters may be inserted into the bolts when these latter are being fixed in position. Concrete Foundations. In making concrete foundations, the simplest plan, for small dynamos, is to make a few taper wooden boxes, a few inches square and of suitable length, and nail them on to a template of the base of the machine where the holding-down bolts will come. Having firmly fixed the template, with the boxes in position, the concrete may be run in. When hard, the boxes and template may be removed, leaving holes in the concrete for the hold- ing-down bolts. In the case of large dynamos, the holding-down bolts should be built in at the time the foundation is made. In this case, the bolts, provided with holding-down plates and narrow taper boxes, or metal tubes of suitable length, are slung in the holes in the template, and the concrete is run in. The bolts being loose in the boxes, are thus capable of a little lateral play while firmly fixed longitudinally. Height of Foundations. It is advisable, in all cases, to carry the top of the foundations of both large and small dynamos to a few inches above the surface of the surrounding ground or floor. The dynamo is thus kept clear of any water which may accumulate. In the case of small dynamos, it will DYNAMO generally be found necessary, in order to keep the belt from coming into contact with the ground, and to enable the brushes to be more conveniently ad- justed, to carry the top of the foundation up to from 12 to 24 inches above the surface of the ground. Fixing Dynamos. In fixing either direct or belt- driven dynamos, it will first be necessary to ascertain, with a spirit-level and long straight-edge, whether the top of the foundation is level and true. If this is found to be the case, the holding-down bolts should be dropped into the holes in the foundation, if they are not already built in, and the dynamos carefully placed thereon, the ends of the bolts being passed through the holes in the bedplate and secured by a few turns of the nuts. The dynamo should then, if belt driven, be carefully aligned with the driving pulley or fly-wheel. In order that the belt may run true on the pulleys, it is needful that a straight line joining the two pulleys should pass through the centre of the face of the driving pulley and the centre of the face of the dynamo pulley. To effect this, when both pulleys are equal in width across the face, a fine cord is stretched perfectly straight from one pulley to the other across the edges lying in one plane ; then, by adjusting the position of the dynamo, the cord can be made to touch the two edges of one side of the driving pulley and the two edges of one side of the dynamo pulley, when the pulleys will be truly aligned, and the machine set square with the driving shaft. If one of the pulleys is wider across the face than the other, the difference should be carefully noted, and allowance made when lining off. Too much attention cannot be paid to 136 RUNNING DYNAMOS. getting the pulleys truly aligned, as the belt is liable to drop off when the machine is started if this is not the case. The dynamo bedplate, and also, if possible, the armature shaft, should next be carefully and finally tested with a spirit-level, and if not found truly level, the machine should be packed up until perfectly level either way. Having carefully aligned the pulleys and levelled the machine, it should next be grouted with thin cement This is effected by arranging a wall of bricks or a few wooden battens around the bedplate of the machine, leaving a few inches clear all round, and stopping up all holes with clay or stiff cement Thin cement is then run in until the holding-down bolt-holes are full, and the cement has risen to the level of the underside of the bedplate. When the cement is set hard, the bricks or wooden battens may be removed, and the edges of the foundation trimmed off, and the nuts of the holding -down bolts screwed up tight and the machine securely fixed. Preliminary Examination of Machine. When the machine has been securely fixed, and previous to the first starting, the whole of the machine should be carefully examined to see that all parts are in good order, and have not been damaged. The field magnet circuit should first be inspected to see that none of the wires or connections have been broken or are loose, and that the coils are correctly coupled up. The caps of the bearings should next be taken off, and these and the journals carefully cleaned from all grit and dirt. They should then be oiled, and the caps replaced and screwed up with the hand only. The gaps between the outer surface of the armature and EXAMINATION OF MACHINE. 137 the polar faces should be examined in order to ascer- tain whether any foreign body, such as a small screw or nail, has lodged therein. If such is the case, it should be carefully removed with a bit of wire. The guard plates protecting the armature windings should also be removed, and the windings carefully inspected by slowly .rotating the armature, to see that they are not damaged, and that the insulation is perfect. The armature should then be finally rotated by hand to see that it revolves freely, and that the bearings are securely fixed. The commutator and brushes should next receive attention, the commutator, to see that it is not damaged in any way through one or more of the segments being knocked in, or the lugs being forced into contact with one another ; and the brush- holders and brushes, to see that the latter are clean and make good contact with the brush-holders or flexible leads, and the former to see that they work freely on the spindle, and that the hold-off catches work properly. In the subsequent working of the dynamo it will of course not be necessary to follow the whole of these proceedings every time the machine is started, as it is extremely unlikely that the machine will be damaged from external causes whilst working without the attendant being aware of the fact. Having ascertained that the machine is not injured in any way, and that the armature revolves freely, the adjustment, of the brushes should next be proceeded with. Adjustment of Brushes. The adjustment of the brushes upon the commutator requires careful atten- tion if sparking is to be avoided. The points upon the commutator at which the tips of the brushes, 138 RUNNING DYNAMOS. carried by opposite arms of the rocker, bear upon the commutator, should be, in bi-polar dynamos, at opposite extremities of a diameter. In multipolar dynamos the positions vary with the number of poles and the nature of the armature winding. In order to facilitate the correct setting of the brushes upon the commutator, setting marks are usually cut in the collar of the commutator next to the bearing. In bi-polar dynamos, these setting marks divide the circumference of the commutator into equal parts. In adjusting the brushes, the tips of all the brushes carried by one arm of the rocker are set in correct line with the commutator segment marked out by one setting mark, and the tips of the brushes carried by the other arm or arms are set in correct line with the segments marked out by the other mark or marks. If one or more brushes in a set are out of line with their setting mark, it will be necessary to adjust the brushes up to this mark by pushing them out or drawing them back, as may be required, afterwards clamping them in position. When adjusting the brushes the armature should always be rotated, so that the setting marks are horizontal. The rocker can then be rotated into position, and the tips of both sets of brushes conveniently adjusted to their marks. In those brush-holders provided with an index or pointer for adjusting the brushes the set- ting marks upon the commutator are absent, the length of the pointer being so proportioned that when the tips of the brushes are in line with the extreme tips of the pointers, the brushes bear upon the correct positions on the commutator. Bedding Brushes. Having adjusted the brushes ADJUSTMENT OF BRUSHES. 139 to their correct positions upon the commutator, their tips or rubbing ends should next be examined, whilst in position, to see that they bed accurately on the surface of the commutator. In many instances it will be found that this is not the case, the brushes some- times bearing upon the point or toe, and sometimes upon the heel, so that they do not make contact with the commutator throughout their entire thickness and width. The angle of the rubbing ends will therefore need to be altered by filing to make them lie flat. Filing Brushes. When the brushes do not bed properly upon the commutator, and filing has to be resorted to in order to alter the angle of the brush tips or ends, it will be found necessary to fix the brush in a holder or filing clamp, in order that the correct angle may be conveniently obtained. This, as a rule, is supplied with the machine, and consists of two pieces of metal, both shaped at one end to the correct angle (usually 45), to which the brushes must be filed. One of the pieces of metal (the back part) has a groove sufficiently large to accommodate the brush, which is clamped in position by the other piece of metal and a pinching screw. If the clamp is not supplied, a convenient substitute can be made out of two pieces of wood about the same width as the brush. One end of each piece of wood is sawn to the correct angle, and the brush is placed between the two. In filing, the brush is fixed in the clamp, with the toe or tip projecting slightly over the edge of the clamp, and the latter being fixed in a vice, the brush is filed by single strokes of a smooth file made outwards, the file being raised from contact with the brush when making the back stroke. 140 RUNNING DYNAMOS. Pressure of Brushes upon Commutator. Hav- ing ascertained that the brushes are correctly placed and bedded upon the commutator, it remains to adjust their pressure upon the latter. This is effected by regulating the tension of the springs provided for the purpose upon the brush-holders. The tension of the springs should be just sufficient to cause the brushes to make a light yet reliable contact with the commu- tator. The contact must not be too light, otherwise the brushes will vibrate, and thus cause sparking; nor must it be too heavy, or they will press too hard upon the commutator, grinding and scoring and wearing away the latter and themselves to an undesirable extent, and, moreover, giving rise to great heating and sparking. The correct pressure is attained when the brushes collect the full strength of current without sparking, while their pressure upon the commutator is just sufficient to overcome any ordinary vibration due to the rotation of the commutator. Adjusting Lubricators. As a rule, sight feed lubricators are used in all but the smallest machines. Previous to starting, these should be examined to see that they feed the lubricant properly, and that the oil passages are not clogged. They should then be adjusted to feed an ample supply of oil on to the armature spindle, The amount required will of course depend upon the load and the nature of the oil used, but from 3 to 12 drops per minute of any ordinary heavy hydro-carbon oil is generally sufficient for a load varying from 6 to 30 horse- power. Starting Dynamos. Having attended to the above preliminaries, and having cleared all keys, spanners, STARTING DYNAMOS. 141 bolts, &c., out of the immediate neighbourhood of the machine, and having raised the brushes from contact with the commutator by means of the hold-off catches, the dynamo may be started and allowed to run light. Whilst thus running, the bearings should be tested from time to time to ascertain if they heat unduly, and an opportunity is also afforded, while the dynamo is thus running, for cleaning the commutator, if this is dirty, with finest emery cloth, afterwards wiping clean with a linen rag. The connections of the machine and external circuits should be verified, and all ter- minals, &c., cleaned and examined. If found correct, the brushes should be let down on to the commutator, and their tips adjusted by rotating the rocker into the neutral points. The tips of the brushes carried by one arm of the rocker will, in bi-polar dynamos with vertical field magnets, bear exactly upon the top or highest point of the commutator, while the tips of those carried by the other arm will bear exactly upon the bottom or lowest point of the commutator. In other types of machines, the positions for the brushes will vary according to the class or form of the field magnet and the system of armature winding. The positions of the brushes in most of the types of dynamos in common use are illustrated in Figs. 21 to 28. If the machine is compound or shunt wound, all switches controlling the external circuits should be opened, as the machine excites best when this is the case; and when the machine is provided with a rhestat or hand regulator and resistance coils, these latter should all be cut out of circuit, or short circuited, until the machine excites, when they can be gradually cut in as the voltage rises. When the 142 RUNNING DYNAMOS. machine is giving the correct voltage, as indicated by the voltmeter or pilot lamp, the machine may be switched into connection with the external or work- ing circuits. When the machine is series wound, it is absolutely necessary to have the external circuit closed, otherwise a closed circuit will not be formed through the field magnet windings, and the machine will not excite. Attention to Dynamo. When the machine is started and at work, it will need a certain amount of attention to keep it running in a satisfactory and efficient manner. The first point to which attention should be paid is the adjustment of the " lead " of the brushes. If this is neglected, the machine will probably spark badly, and the commutator and brushes will constantly require filing and trimming. The " lead " is the term applied to the slight forward movement which it is found necessary to give to the brushes of most dynamos in order to avoid sparking with an increase of load. This lead in all good dynamos is very small, and varies with the load and class of machine. The best lead to give to the brushes can in all cases be found by rotating the rocker and brushes in either direction to the right or left of the neutral points, until sparking com- mences increasing with the movement. The posi- tion midway between these two points is the correct position for the brushes, for at this position the least sparking occurs, and it is at this position that the brushes should be fixed by clamping the rocker. In series dynamos giving a constant current, such as for arc lamps in series, the brushes require practi- cally no lead. In shunt and compound dynamos the ATTENTION TO DYNAMOS. 143 lead varies with the load, and therefore the brushes must be rotated in the direction of rotation of the armature with an increase of load, and in the opposite direction with a decrease of load. In cases where the dynamos are subjected to a rapidly varying or fluctuating load, it is of course not possible to constantly shift the brushes as the load varies, there- fore the brushes should be fixed in the positions where the least sparking occurs at the moment of adjustment. If at any time very violent sparking occurs, which cannot be reduced or suppressed by varying the position of the brushes by rotating the rocker, the machine should be shut down at once, otherwise the commutator and brushes are liable to be destroyed, or the armature burnt up. This especially refers to high tension machines. As soon as any abnormal sparking is seen at the commutators of such machines, their speed should be at once reduced, and the commutator cleaned up, and the brushes readjusted. Another very important point to be looked to is the lubrication of the machine. The lubricators should be inspected from time to time, to see that they feed the lubricant properly, and that none of the waste oil passages are clogged. The oil should on no account be allowed to get on to the commutator or brushes, or into the wind- ings of the armature, as it is liable to cause sparking at the brushes, and to destroy the insulation of the armature. In filling the lubricators, oil cans made of some non- magnetic material such as copper, brass, or zinc, should always be used. If iron cans are used, they are liable to be attracted by the field magnets, and thus possibly catch in the armature, and destroy 144 RUNNING DYNAMOS. the insulation of the latter. The bearings, and also the field magnet coils, should be tested at intervals, to see that they do not become unduly heated. When testing the temperature of low tension machines, the hand may be used as a guide for judging when the machine is running at a safe temperature. If the heat of any portion can be easily borne by the naked hand, it may be taken that the temperature of the machine is within safe limits. In the case of high tension machines, how- ever, the naked hand cannot be brought with safety into contact with any portion of the machine, and therefore the only way to ascertain if the windings or other electrical parts are at a safe temperature is to apply a thermometer. It may be taken as a safe rule that no part of a working dynamo should have a temperature of more than 80 Fahr. above that of the surrounding air. Hence, if the temperature of the engine-room is noted before applying the thermometer to the machine, it can at once be seen if the latter is working at a safe temperature. In taking the temperature, the bulb of the thermometer should be wrapped in a woollen rag. The screws and nuts securing the different con- nections and cables should be examined occasionally, as they frequently work loose through the vibration. Attention to Brushes and Commutator. The brushes and commutator are the most troublesome parts, of a dynamo, and require most attention. To keep them in a satisfactory working condition, the main thing to be guarded against is the production of sparking at the brushes. If care be taken in the first instance to properly adjust the brushes to their set- ATTENTION TO BRUSHES. 145 ting marks, and their pressure upon the commutator, and afterwards to attend to the lead as the load varies, so that little or no sparking occurs, and to keep the brushes and commutator free from dirt, grit, &c., and excessive oil, the surface of the commutator will assume a dark burnished appearance, and all wear will practically cease. Under these circumstances the commutator will run cool, and free from sparking, and will give very little trouble. In order to main- tain these conditions it will only be necessary to see that the brushes are properly trimmed and fed for- ward to their setting marks, as described above, as they wear away, and that the commutator is occasion- ally polished with the finest emery cloth. If, on the other hand, the pressure of the brushes upon the commutator is too great, or their adjustment is faulty, or the commutator is allowed to get into a dirty condition, sparking will inevitably result, and, if not at once attended to and remedied, the brushes will quickly wear away, and the surface of the commu- tator will be destroyed. If this condition of things is allowed to continue, matters will rapidly get worse. In the earlier stages, the surface of the commutator will become roughened or scored, resulting in jumping of the brushes, and increased sparking ; in the later stages, the commutator will become untrue and worn into ruts, and owing to the violent sparking which takes place through this circumstance, the machine will quickly be rendered useless for practical purposes. When once started, the only way to remedy this condition of things is to repolish the commutator and readjust the brushes, as directed above. If the commutator is merely scored, a smooth file applied XJNIVERSITT 146 RUNNING DYNAMOS. while the armature is revolving, with a final polishing with coarse and fine emery cloth, will generally put things into a satisfactory condition. If, however, the commutator is worn into deep ruts, or is untrue, nothing short of putting the armature in the lathe, and re-turning the commutator, will make a good job of it. When carbon brushes are used, a little extra special attention should be given in keeping the commutator perfectly clean, otherwise it is liable to heat up through short circuits, caused by carbon dust lodging between the segments. When carbon brushes are working properly, the fact is indicated by a uniform greyish tinge being imparted to the commu- tator, with a total absence of heating or sparking of any description. If the surface of the commutator assumes a mottled or streaky appearance, accompanied by small sparks flashing from segment to segment, it is advisable to slow down the machine and clean up the commutator at once. When either metal or carbon brushes are used, the surface of the commu- tator is bound in course of time to undergo a certain amount of wear, even when the greatest care is taken to reduce sparking. In order to prevent this wear giving rise to ruts or ridges upon the surfaces of the commutator, it is advisable to shift the brush-holders and brushes upon the rocker arm, if this is possible, from time to time. The unequal wear of the commu- tator may also be prevented by so arranging the brushes carried by one arm of the rocker that they cover the gaps between the brushes carried by the other arm of the rocker. The armature spindle or shaft is also given a little end play in order to prevent this grooving. TRIMMING BRUSHES. 147 Lubricant on Commutator. In most cases it will be found that a little lubricant is needed on the commutator in order to prevent cutting of the latter by the brushes, and this is especially the case when hard strip brushes are used. The quantity of oil so used should be very small a few drops smeared upon a piece of clean rag, and applied to the commutator while running, being quite sufficient. It is advisable to use mineral oil, such as vaseline, or any other hydro-carbon. Animal or vegetable oils should be avoided, as they have a tendency to carbonise, and thus cause short-circuiting of the commutator, with attendant sparking. Trimming Brushes. At certain intervals, accord- ing to the care taken to reduce sparking, and the length of time the machine runs, the brushes will fray out or wear unevenly, and will therefore need trim- ming. They should then be removed from the brush- holders, and their contact ends or faces examined. If not truly square, they should be filed or clipped with a pair of shears, the course of treatment differing with the type of brush. If metal strip brushes, the feathered-out ends should be clipped square with a pair of shears, the ends thoroughly cleaned from any dirt or carbonised oil, and replaced in their holders. Gauze and wire brushes require a little more attention. When their position on the commutator has been well adjusted and looked after, so that little or no spark- ing has taken place, it will generally be only found necessary to wipe them clean, and clip off the fringed edges and corners with the shears, or a pair of strong scissors. If, however, the machine has been sparking, the faces will be worn or burnt away, and probably 148 RUNNING DYNAMOS. fused. If such is the case, they will need to be put in the filing clamp and filed up square and true, as directed above. If the contact faces of the brushes are very dirty and covered with a coating of carbon- ised oil, &c., it will be necessary to clean them with benzoline or soda solution before replacing. The handiest way of trimming carbon brushes, or of bed- ding a complete new set of metal brushes, is to bind a piece of emery cloth or sand paper, face outwards, around the commutator after the current has been shut off, and then mount the carbon or metal brushes in the holders, adjusting the tension of the springs so that the brushes bear w r ith a moderately strong pres- sure upon the emery cloth or sand paper. Then let the machine run slowly until the ends of the brushes are ground to the proper form. Care should be taken, however, that the carbon or metal dust given off does not get into the commutator connections or armature windings, or short circuiting will result. If it be- comes necessary, through sparking or other causes, to trim the brushes while the machine is working, one brush at a time should be removed from the holders. The brush to be removed should first be raised care- fully from the commutator ; then, if excessive sparking or heating occurs, the brush should be let down again, and the tension of the springs of the brushes tempo- rarily increased until the brushes are trimmed. This of course only applies to machines provided with at least two brushes to each set. If only one brush is provided, the machine must be stopped before the brushes can be trimmed. Shutting down Dynamo. When shutting down a machine, the load should first'be gradually -reduced, if SHUTTING DOWN DYNAMOS. 149 possible, by easing down the engine ; then, when the machine is supplying little or no current, the main switch should be opened. This reduces the sparking at the switch contacts, and prevents the engine racing. When the voltmeter almost indicates zero, the brushes should be raised from contact with the commutator. This prevents the brushes being damaged in the event of the engine making a backward motion, which it often does, particularly when it is a gas-engine. On no account, however, should the brushes be raised from the commutator while the machine is generating any considerable voltage ; for not only is the insula- tion of the machine liable to be damaged by this proceeding, but in the case of large shunt dynamos an exceedingly violent shock is liable to be adminis- tered to the person lifting the brushes. When the dynamo is at rest, or only revolving slowly, and the brushes are raised from the commutator, the latter should be cleaned up, if this is necessary. In dusty places, such as flour mills, sugar works, cement works, &c., it will probably be necessary to clean off the commutator with benzoline, and finally with finest emery cloth, at the end of every run. In places free from dust, it will only be necessary to wipe the revolving surface perfectly clean, or until it will not soil a white rag, and occasionally to apply a little fine emery cloth before stopping. When the machine is stopped it should be thoroughly cleaned up. The armature should be dusted with a pretty stiff brush from any adherent copper dust, dirt, &c., and the other portions of the machine should be thoroughly cleaned with linen rags. Waste should not be used, as it is liable to leave threads, fluff, &c., on the r 150 RUNNING DYNAMOS. projecting parts, terminals, and other parts of the machine, and on the windings of the armature, which is very difficult to remove. The brushes should be examined, and if necessary trimmed and adjusted, and all terminals, screws, bolts, &c., carefully cleaned and screwed up ready for the next run. The brush- holders should receive special attention, as when dirty they are liable to stick and cause sparking. All dirt and oil should be removed from the springs and contacts, and pivots and other working parts. It is advisable at stated intervals to entirely remove the brush-holders from the rocker arms, and give them a thorough clean up, by taking them to pieces, and cleaning each part separately with emery cloth and benzoline or soda solution. Another point to which particular attention should be given is the cleaning of the brush rocker. This being composed wholly of metal, and the two sets of positive and negative brushes being only separated from it by a few thin insulating washers, it follows that if any copper dust given off by the brushes is deposited in the neighbour- hood of these washers, there is considerable liability for a dead short circuit of the machine to occur, by the dust bridging across the insulation. These par- ticular parts should therefore be kept scrupulously clean, and free from any conducting matter. It is a good plan, when the machine has been thoroughly cleaned up and all connections made secure, to occasionally test the insulation of the different parts and also that of the entire machine from earth with an Ohmeter or Wheatstone Bridge. If a record is kept of these tests, any deterioration of the insulation of the machine can at once be detected, localised, and SHUTTING DOWN DYNAMOS. 151 remedied before it has got far enough to cause a breakdown. As a means of protecting the machine from any moisture, dirt, &c., while standing idle, it is advisable to cover it up with a suitable waterproof cover. CHAPTER XI. FA ULTS IN D YNAMOS. No matter how well designed and constructed a dynamo may be, it is liable at some period or other of its life to develop irregularities in its working which may either wholly or partially incapacitate it from performing its duties. The abnormal per- formance may arise from a variety of causes, some purely electrical, others purely mechanical, or to both in combination. It may be due to some simple defect which is at once apparent on a little inspec- tion of the machine, or on the other hand it may have its origin in some obscure cause which may almost defy detection. In any case, the source of the trouble should be diligently and patiently sought for, and when located, the appropriate remedy, if any, applied as soon as possible. Testing Battery and Galvanometer. As in the detection of electrical faults in dynamos a testing battery and galvanometer are indispensable, a few words regarding the construction and use of the most suitable types may not be out of place. In regard to the battery, a few cells of any of the well- known types as used in bell and telephone work, TESTING BATTERY AND GALVANOMETER. 153 such as the Leclanche, Dry, Daniell, &c., are suit- able. In reference to the galvanometer, a lineman's detector, or any ordinary sensitive galvanometer, will answer the purpose. A form of testing battery and galvanometer, specially designed and constructed for this class of work, is illustrated in Fig. 72. The battery consists of a number of small Leclanche cells, each contained in a sealed ebonite case. The FIG. 72. cells are connected in series, and contained in a hardwood outer case, which also contains the galvanometer when not in use. The positive and negative poles of the battery are connected to two brass terminals fixed upon the outside of the case, by means of which the battery may be connected to the galvanometer or the appliance, or circuit under test. The galvanometer consists of a pair of astatic magnetic needles, suitably arranged 154 FAULTS IN DYNAMOS. between a pair of bobbins or coils wound with fine insulated wire. The ends of the coils or bobbins are connected to two brass terminals, which are fixed upon two ebonite insulating blocks projecting through the brass case. When an electric current flows through the wire coils a magnetic field is created, and the needles are deflected to a greater or lesser degree in accordance with the strength of the current flowing in the coils. In testing for faults, two methods of connecting up the battery and gal- vanometer to the circuit under test are employed, these being termed the conductivity test and the insulation test respectively. Testing for Conductivity. In making this test, the instruments are connected as represented in FIG. 73. Fig. 73- B is the battery, G the galvanometer, and S is a coil of wire being tested for electrical continuity or conductivity. As will be seen, the positive pole -f v TESTING FOR CONDUCTIVITY. 155 of the battery is connected to one terminal of the galvanometer, and the other or negative pole is con- nected to one of the ends of the coil under test. The other terminal of the galvanometer is connected to the other end of the coil. If the connecting wires are making good electrical contact with the respective terminals, and the wire of the coil being tested is unbroken, the needle of the galvanometer will be deflected as soon as a closed circuit is made by the end of the coil coming into contact with the galvano- meter terminal. If the wire of the coil is broken in some part, or the ends of the connecting wires do not make good electrical contact with the terminals, the needle will not be deflected. In order to prevent mistakes, it is advisable to test the battery and galvanometer connections and contacts by short circuiting or bringing the ends of the wires con- necting the terminal of the galvanometer and nega- tive pole of the battery together, before starting to test the circuit or coil. If the needle is deflected, the connections are all right ; if undeflected, there is a bad contact somewhere which must be made good before the test can proceed. Testing for Insulation. The object of this test is to ascertain whether the insulation of a circuit or of the wire wound upon a metal spool or core, such as a magnet core, has broken down or is in good order. In making the test, the instruments and connections are arranged as shown in Fig. 74. The battery and galvanometer are connected to one another, as in the conductivity test described above. The unconnected terminal of the battery is connected to one end of the coil under test, the other end of the coil remain- 156 FAULTS IN DYNAMOS. ing free and unconnected. Some portion of the metal core, say the end, is then cleaned bright with a knife or emery cloth, and the unconnected terminal of the galvanometer is brought into contact with this bright or clean part of the core. If then some portion of the insulation of the wire has been abraded or destroyed, thus bringing the bare wire into contact with the metal core, as at A in the I I I II h B FIG. 74. figure, the needle of the galvanometer will be de- flected, since a closed circuit is formed through the core and wire. If, on the contrary, the insulation is perfect, the needle will be undeflected. It will thus be seen that in the conductivity test it is needful that the needle should be deflected to prove that all is right, whilst in the insulation test the converse holds good. If the needle is deflected, it proves that the insulation has broken down. V FAILURE TO EXCITE. 157 Faults in Dynamos. The chiefest irregularities to which a dynamo is subject may be enumerated as follows : A. Failure to excite. B. Sparking at brushes. C. Excessive heating. D. Excessive noise or vibration. E. Variation or decrease of speed. F. Variation of voltage. Each of these irregularities may be due to a number of causes, acting either singly or in com- bination. A list of the defects or faults tending to produce a given irregularity is given under each heading when the same is under consideration in the succeeding paragraphs, and it will be necessary to test for each in turn until the true defect or fault producing the abnormal performance is located. A. Failure to Excite. If, when a reasonable time has elapsed, the machine (shunt, series, or compound) fails to excite, the following defects or faults should be sought or tested for in the order given, until the machine excites : (i.) Brushes out of neutral points. (2.) Defective contacts. (3.) Hand regulator incorrectly adjusted. (4.) Incorrect connections. (5.) Insufficient speed. (6.) Open circuits. (7.) Short circuits or heavy loads in external circuit. (8.) Insufficient residual magnetism. 158 FAULTS IN DYNAMOS. (9.) Reversed magnetism in fields. (10.) Field coils acting in opposition. (11.) Short circuits in dynamo. A (i.) Brushes out of Neutral Points. The first point to be observed, if the machine fails to excite, is the position of the brushes upon the commutator. If these are not on or near the neutral points, the whole of the E. M. F. of the armature will not be utilised, and will probably be insufficient to excite the machine. The correct positions for the brushes have already been described in Chapter X. (Running Dynamos). If in doubt as to the correct positions, the brushes should be rotated by means of the rocker into various points on the commutator, sufficient time, say five minutes, being given the machine to excite before moving them into a new position. A (2.) Defective Contacts. If the different points of contact of the connections of the machine are not kept thoroughly clean and free from oil, &c., it is probable that such resistance will be interposed in the path of the exciting current as to prevent the machine building or exciting. It may be remarked that the battery and galvanometer is not a decisive test for this fault, as the needle may be deflected through a resistance, due to a bad contact, much too great to allow of the small E. M. F., generated on first starting the machine, to send a current suffi- ciently great to build the machine. Each of the contacts should therefore be examined, and cleaned, and screwed up tight. The chief point to which attention should be given is the contact faces of the brushes and surface of the commutator. These are very frequently covered with a slimy coating of oil UNIVERSITY FAILURE TO and dirt, which is quite sufficient to prevent the machine exciting. The brushes and commutator should be cleaned up as directed in Chapter X. (Running Dynamos). A (3.) Hand Regulator incorrectly adjusted. Shunt and compound wound machines are very frequently provided with hand regulators for in- serting or removing resistance into the field circuit. When such is the case, it is possible the resistance in circuit may be too great to allow of the necessary strength of exciting current passing through the field windings. Therefore, in all cases before start- ing, remove by cutting out or short circuiting the whole of the resistance coils from circuit. The field coils of series machines are sometimes provided with short circuiting switches or resistances arranged to shunt the current across the field coils. In this case there may not be sufficient resistance in circuit, and therefore almost the whole of the exciting current will be shunted across in place of passing through the field coils. The remedy in this case is to open the switch completely, or, if this cannot be effected, to cut in sufficient resistance to enable sufficient current to pass through the field windings to excite the machine. A (4.) Incorrect Connections. When the machine is first erected, the failure to build may proceed from incorrect connections. The whole of these latter should therefore be traced or followed out, and com- pared with the diagrams of field and dynamo connec- tions given in Figs. 44 to 59. A (5.) Insufficient Speed. In shunt and compound dynamos there is a certain critical speed below which 160 FAULTS IN DYNAMOS. they will not excite. If the normal speed of the machine is known it can at once be seen whether the failure to build arises from this cause, by measuring the speed of the armature with a speed indicator. In all cases it is advisable, if the machine does not excite in the course of a few minutes, to increase the speed to a certain extent. As soon as the voltage rises, the speed may be reduced to its normal value. A (6.) Open Circuits. The manner in which the different types of machines are affected by open circuits is dependent upon the class of machine. In the shunt machine it is necessary to have the ex- ternal circuit open before it will build, whilst in the series machine it is needful to have it closed under like circumstances. Open circuits are most likely to occur in (a) Armature circuit ; () Field circuit ; (<:) External circuit. (fi) Open Circuit in Armature. The localisation and repair of faults in this circuit are described in Chapter XII. (Faults in Armatures). When the open circuit is due to the brushes not making good contact with the commutator, simple examination generally reveals the defect, which may be remedied as directed in A (2) (Defective Contacts). (b} Open Circuit in Field Circuit. This may be caused by bad contacts at the terminals, or broken connections, or fracture of the coil windings. Nothing but rigid inspection and testing of the entire field circuit will locate the fault. If the machine is shunt wound, it may occur in the hand regulator through a broken resistance coil or bad contact. Very fre- quently the fault occurs in the connecting wires leading from the machine to the hand regulator FAILURE TO EXCITE. l6l fixed upon the switchboard, or in the short wires connecting the field coils to the terminals or brushes. The insulation of a wire will sometimes hold the two ends of a broken wire together so as to defy any but the most careful inspection or examination ; there- fore, in order to avoid loss of time, it is advisable to disconnect the wires if possible, and test each sepa- rately for conductivity with a battery and galvano- meter connected, as in Fig. 73. If the fault is not located in the various connections, the magnet coils should be tested with the battery and galvanometer coupled up as in Fig. 73, care being first taken to disconnect the ends of each of the coils. A faulty coil will not show any deflection of the galvanometer. Having located the faulty coil, the discontinuity or break should be searched for and rectified. In the shunt coils of shunt and compound dynamos, and these are most liable to this defect, the break in- variably occurs at the point where the wire passes through the flanges of the spool or bobbin. In most cases a little of the wood or metal of which the flange o is made can be gouged or chipped out, and a new connecting wire soldered on to the broken end of the coil without much difficulty. If it is necessary to take the magnets apart at any time, great care should be taken in putting them together again to wipe all faces perfectly clean, and screw up firmly into contact, the connections of the coils being made as before taken apart. If the faulty coil cannot be repaired quickly, and the machine is urgently required, the coil may be cut out of circuit entirely, or short circuited, and the remaining coils coupled up so as to produce the correct polarity in the pole pieces. L 162 FAULTS IN DYNAMOS. In this case, however, as the coils are liable to heat up to a greater extent than formerly, owing to the increased current, it is advisable to proceed cautiously in starting the dynamo, in case the temperature exceeds a safe limit. If this occurs, a resistance may be put in circuit with the field coils, or the speed of the dynamo reduced. (c) Open Circuit in External Circuit. Series wound machines are only affected by this occurrence. If the disconnection is complete, the fault may readily be located by the battery and galvanometer coupled up as in Fig. 73. If only partial, however, this fault is very elusive, for the reasons mentioned in A (2) (De- fective Contacts). If the external circuit tests out apparently all right, and no defective contacts are apparent in any part of the machine, and all short circuiting switches, &c., are cut out of circuit, and the machine still refuses to excite, short circuiting the terminals of the machine should be tried. This should be effected very cautiously, especially if a high tension machine. It is advisable to have, if possible, only a portion of the load in circuit, and the short circuit should be effected as shown in Fig. 75 AB. The short circuit may be made by momentarily bridging across the two terminals of the machine with a single piece of wire. As this, how- ever, is liable to burn the terminals, a better plan is to fix a short piece of scrap wire in one terminal, and then with another piece of insulated wire make momentary contacts with the other terminal and the short piece of wire. If the machine excites, it will be at once evident by the arc which occurs between the two pieces of wire. As the voltage of a series machine FAILURE TO EXCITE. I6 3 when induced to build in this manner generally rises very rapidly, great care should be taken that the contact is at first only momentary, merely a rubbing or scraping touch of the wires. The contact may be prolonged if the machine does not excite at the first contact. Compound wound machines can often be FIG. 75. made to build quickly by short circuiting their terminals in this manner. A (7.) Short Circuits or Heavy Load in External Circuit. A shunt machine will not excite under these circumstances, for the reason that practically the whole of the current generated in the armature passes direct to the external circuit, and the differ- 164 FAULTS IN DYNAMOS. ence of potential between the shunt terminals is practically nil. If it is suspected that the failure to excite arises from this cause, the main leads should be taken out of the dynamo terminals, when, if due to this cause, the machine will excite. When the machine is compound or series wound, a fault of this description causes the machine to overload and blow the fuses. If due to overload, this latter should be removed as directed in B (4) (Overload of Dynamo). A (8.) Insufficient Residual Magnetism. This fault is not of frequent occurrence, and it is almost impos- sible for it to take place if the field magnets are of cast-iron. It always occurs when the dynamo is a new one, or when the field magnets have been taken apart for repairs, &c. It may be remedied by pass- ing the current from a few storage cells, or another dynamo, for some time in the proper direction through the field coils. If a heavy current, such as is obtainable from a storage battery, is not available, and the machine is shunt or compound wound, a few Leclanch or dry cells, arranged as in Fig. 76, will generally effect the purpose. The flexible " lead " (L) of the dynamo (D) is disconnected from the positive terminal of the machine, and is connected to the negative or zinc pole of the battery (B), the other or positive carbon pole being connected to the terminal, from which the lead was removed, and shunt circuit (s). As thus arranged, it will be seen that the battery (B) is in series with the armature and shunt circuit, and therefore its E. M. F. will be added to any small E. M. F. generated in the armature. When the machine is started, the combined E. M. F.s will probably be able to send sufficient current through FAILURE TO EXCITE. 165 the shunt to excite the machine. As the voltage rises and the strength of the current in the shunt windings increases, the flexible lead may be again inserted into the terminal from which it was removed. B FIG. 76. The battery will thus be short circuited, and may be cut out of circuit without any danger of breaking the shunt circuit, and thus causing the machine to demagnetise. 1 66 FAULTS IN DYNAMOS. A (9.) Reversed Magnetism in Fields. This also is a fault of infrequent occurrence. It may be caused by the proximity of other dynamos, but is generally due to reversed connections of the field coils. Under such conditions the field coils tend to produce a polarity opposed to the magnetisation to which they owe their current, and therefore the machine will refuse to excite until the field connections are reversed, or a current is sent from another dynamo or a battery through the field coils in a direction to produce the correct polarity in the pole pieces. A (10.) Field Coils acting in Opposition. This may occur when the dynamo is a new one, or the coils have been removed for repairs. It may be caused either through the coils having been put on the field cores the wrong way, or through incorrect coupling up. Under these circumstances, the dynamo, if bi-polar, will fail to excite ; and if multipolar, poles will be produced in the yokes, &c. It may be remedied by removing one of the coils from the core and putting it on the reverse way, or by reversing its connections. The connections of all the coils should be verified by applying Professor Jamieson's rule given on page 21. The manner of coupling up the coils of the different types of field magnets will be under- stood by reference to Figs. 52 to 59. In compound dynamos it sometimes happens that the machine will excite properly, but that the series coils tend to reverse the polarity of the dynamo, thus reducing the voltage as the load upon the machine increases. This may be detected when the machine is loaded by short circuiting the series coils ; not the terminals. If the voltage rises in doing this, the series coils are FAILURE TO EXCITE. l6/ acting in opposition to the shunt coils, and the con- nections of the series coils must be reversed. A (11.) Short Circuits in Dynamo. A dynamo may refuse to excite through some portion of its windings or connections being short circuited, for the reason that the field magnets are deprived of the necessary current required for building the machine. Short circuits most frequently occur in (a) Terminals ; (b) Brush-holders ; (c) Commutator ; (d) Armature coils ; (i) Field coils. (a) Short Circuits in Terminals. The terminals of the various circuits of the machine are liable to be short circuited, either through metallic dust bridging across the insulation, or through the terminals making direct contact with the frame of the machine. The various terminals should be examined, and if the fault cannot be located by inspection, they should each be disconnected from their circuits and tested with a battery and galvanometer arranged as in Fig. 77. B is the battery, one pole of which is placed in contact with the frame of the machine at a point which has previously been well scraped and cleaned; the other pole is connected to one of the galvano- meter terminals as shown. The other terminal of the galvanometer is connected to each of the dynamo terminals (T T) under test in turn. If a deflection of the needle is produced when the galvanometer ter- minal is in contact with either, the terminals are in contact with the frame, and they should then be removed, and the fault repaired by additional in- sulation or by reinsulating. (b) Short Circuits in Brush- holders. As previously mentioned, the brush-holders are liable to be short 1 68 FAULTS IN DYNAMOS. circuited through the rocker by metallic- dust lodging in the insulating washers. These points should there- fore be examined and cleaned, and the two sets of brush-holders tested for short circuits between them. To test the brush-holders, the brushes should be FRAME OF DYNAMO FIG. 77. raised from contact with the commutator by means of the hold-off catches, and all connecting cables removed. The galvanometer and battery should then be coupled up, as in Fig. 74, and one terminal of the galvanometer connected to one set of brushes, FAILURE TO EXCITE. 169 and the other set placed in connection with the un- connected terminal of the battery. If the needle is deflected when thus connected, the brush-holders are short circuited through some point, when they should be taken out of the rockers and the fault repaired. (c) Short Circuits in Commutator ; (d) Short Cir- cuits in Armature Coils. The localisation and repair of faults in these parts of a dynamo are fully described in Chapter XII. (Faults in Armatures). (e) Short Circuits in Field Coils. When short circuits occur in the field coils or circuit, the machine as a rule refuses to excite. The short circuit may be in the terminals or connections, and these should first be examined and tested as described above (a). When in the field coils, the fault may be detected by measuring the resistance of each of the coils with an Ohmeter or Wheatstone Bridge. The faulty coils will show a much less resistance than the perfect coils. The fault may also be discovered and located by passing a strong current from a battery or another dynamo through each of the coils in turn, and ob- serving the relative magnetic effects produced by each upon a bar of iron held in their vicinity. Some series dynamos are provided with a resist- ance, arranged in parallel or shunt with the field coils, to divert a portion of the current therefrom, and thus regulate the output. When making a series dynamo excite, all resistances and controlling devices should be temporarily cut out of circuit by opening the shunt circuit. Series machines have frequently a switch which short circuits the field coils. Care should be taken that this is open, or otherwise the machine will not excite. FAULTS IN DYNAMOS. B. Sparking at Brushes. In all good dynamos there are certain positions upon the commutator for the brushes at which there will be absolutely no sparking so long as the commutator is kept clean and in good condition. In other dynamps, badly designed or constructed, sparking occurs at all posi- tions, no matter where the brushes are placed, and in such dynamos it is therefore impossible to prevent sparking at the brushes, no matter how well they are adjusted. When sparking occurs at the brushes of a good dynamo, two kinds may generally be dis* tinguished by the practised eye, viz., those sparks due to bad adjustment of the brushes, generally of a bluish colour, small when near the neutral points, and increasing in violence and brilliancy as the brushes recede from the correct positions upon the commu- tator; and those due to dirty and neglected state of the commutator and brushes, these being distinguished by a reddish colour and a spluttering or hissing. When due to this last-mentioned cause, it is impos- sible to suppress the sparking until the commutator and brushes have been cleaned up. In the former case, the sparks will disappear as soon as the brushes have been rotated into the neutral points. Another class of sparks appear when there is some more or less developed fault, such as a short circuit, or dis- connection in the armature or commutator. These are similar in character to those produced by bad adjustment of the brushes, but are distinguished from the latter by their not decreasing in violence as the brushes are rotated towards the neutral points. Having distinguished the classes of sparks which appear at the commutator of a dynamo, it remains SPARKING AT BRUSHES. 171 to enumerate the causes tending to produce sparking. These are : (i.) Bad adjustment of brushes. (2.) Bad condition of brushes. (3.) Bad condition of commutator. (4.) Overload of dynamo. (5.) Loose connections, terminals, &c. (6.) Disconnections in armature circuit. (7.) Short circuits in armature circuit. (8.) Short circuits or disconnections in field magnet circuit. B (i.) Bad Adjustment of Brushes. When sparking is produced by bad adjustment of the brushes, it may be detected by rotating or shifting the rocker, by the indication that the sparking will vary with each move- ment. To obtain good adjustment of the brushes, it will be necessary to rock them gently backwards and forwards, as directed in Chapter X., until a position is found in which the sparking disappears. If a position cannot be found at which the sparking dis- appears, it is probable that the brushes are not placed diametrically apart upon the commutator, or that the neutral points are not situated in their true theoretical positions upon the commutator through some defect in the winding, &c. In this last-mentioned case, the brushes may be strictly adjusted to their theoretically correct positions before starting the machine ; then, when the machine is started and the load put on, violent sparking occurs, which cannot be suppressed by shifting the rocker. If, however, one set of brushes only is observed, it will generally be found that, at a certain position, the sparking at the set OF THE IVERSITT 1/2 FAULTS IN DYNAMOS. of brushes under observation ceases or is greatly reduced, while sparking still occurs at the other set. When this position is found, the rocker should be fixed by the clamping screw, and the brushes of the other set at which sparking is still occurring adjusted by drawing them back or pushing them forward in their holders until a position is found at which the sparking ceases, at which they should be fixed. Correct position of the brushes upon the commutator and the suppression of sparking is a matter of great importance, and any time spent in carefully adjusting will be amply repaid by the decreased attention and wear of the brushes and commutator. B (2.) Bad Condition of Brushes. If the contact faces of the brushes are fused or covered with car- bonised oil, dirt, &c., there will be bad contact between the brushes and commutator, and consequently great heating and sparking. Simple examination will generally reveal whether this is the case. The remedy is to remove the brushes, one at a time if the machine is running, clean, file if necessary, trim, and readjust. If the brushes are exceedingly dirty, or saturated with oil, it will be necessary to clean them with turpentine, benzoline, or soda solution, before re- placing. B (3.) Bad Condition of Commutator. If the surface of the commutator is rough, worn into grooves, or eccentric, or has one or more segments loose, or set irregularly, the brushes will be thrown into vibration, and sparking will result. A simple examination of the commutator will readily detect these defects. The remedy for a rough commutator is to file it up SPARKING AT BRUSHES. 1/3 while running with a dead-smooth file, afterwards polishing with finest emery cloth. If the com- mutator is untrue, the fact will be indicated when the machine is slowed down by a visible excentricity, or by holding the hand, or a stick in the case of high tension machines, against the surface while revolving, when any irregularity or excentricity will be apparent by the vibration or movement of the stick. The only remedy for an excentric commutator is to re-turn it as directed in the succeeding paragraph. Loose or high or low segments may be detected by the same means. The remedy for high segments is to tap them gently down with a small hammer or mallet, and if possible tighten up the clamping cones at the ends of the commutator. If it is impossible to hammer the segments down, they should be filed down level with the rest of the commutator, or the commutator re-turned. For low segments, the only remedy is to pull out the segments as directed in Chapter XII. (Faults in Armatures), or turn com- mutator down to their level. Re-turning Commutator. In re-turning the com- mutator, the armature should first be carefully taken out of the armature chamber, avoiding knocks or blows of any kind. The whole of the windings should then, in order to prevent any particles of metal finding their way on to the surface of the armature at the time the commutator is being turned, be entirely wrapped in calico or canvas before the armature is put into the lathe. The armature should on no account be rolled upon the floor, or subjected to blows or knocks while being put into the lathe, the winding is liable to be ruined if this takes place. 174 FAULTS IN DYNAMOS. In re-turning the commutator, a sharp-pointed tool should be used with a very fine feed. A broad-nosed tool ought not to be used, as it is liable to burr over the segments. After turning, the commutator should be lightly filed up with a dead-smooth file, and finally polished with coarse and fine emery cloth. After the commutator has been turned and polished, the insula- tion between the segments should be lightly scraped with the tang of a small file to remove any particles or burrs of metal which may be likely to short circuit the commutator. The points where the armature wires are soldered to the lugs should also be carefully cleaned with a brush from any adherent copper dust, and should then receive a coat or two of shellac varnish. While the commutator is being turned, care should be taken that the setting marks for the adjust- ment of the brushes are not turned out if these are present. The same care should be used in putting the armature back into the armature chamber as was used in taking it out, otherwise the insulation is liable to be seriously damaged. B (4.) Overload of Dynamo. It may happen through some cause or other that a greater output is taken from the machine than it can safely carry. When this is the case, the fact is indicated by exces- sive sparking at the brushes, great heating of the armature and other parts of the dynamo, and possibly by the slipping of the belt (if a belt-driven machine), resulting in a noise. The causes most likely to pro- duce overload are : (a) Excessive voltage ; () Ex- cessive current ; (c} Reversal of polarity of dynamo ; (d) Short circuits or grounds in dynamo, or external circuits. SPARKING AT BRUSHES. 1 75 (a) Excessive Voltage. This will be indicated by the voltmeter, and by the brightness of the pilot lamp. It may be caused either by excessive excita- tion of the field magnets, or by excessive speed. In the former case, resistance should be introduced into the field circuit to diminish the current flowing therein if a shunt machine ; or if a series machine, a portion of the current should be shunted across the field coils by means of a resistance arranged in parallel with the series coils ; or the same effect may be produced in both cases by reducing the speed of the armature if this is possible. If due to excessive speed, which will be indicated by a speed indicator, the natural remedy is to reduce the speed of the motor driving the dynamo, or, if this is not possible, insert resistance into the dynamo circuit, as described above. (b) Excessive Current. This will be indicated by the ammeter. If the dynamo is supplying arc lamps, the excessive current may possibly be caused by the bad feeding of the lamps. If this is the case, the fact will be indicated by the oscillations of the ammeter needle, and by the unsteadiness of the light. If incan- descent lamps are in circuit, the fault may be caused by there being more lamps in circuit than the dynamo is designed to carry. Under such circumstances, another dynamo should be switched into circuit in parallel, or, if this is not possible, lamps should be switched off until the defect is remedied. When electro-motors are in circuit, sparking frequently results at the dynamo commutator, owing to the fluctuating load. In such cases the brushes should be adjusted to a position at which the least sparking occurs with the average load. . v 1/6 FAULTS IN DYNAMOS. (V) Reversal of Polarity of Dynamo. When com- pound or series wound dynamos are running in parallel, their polarity is occasionally reversed while stopping by the current from the machines at work. Under such conditions, when the machine is again started, the E. M. F. of one is added to that of another, or the machines are connected in series, so that a closed circuit is formed, and as a consequence an enormous current results. Before the machine can be again coupled in parallel, it will be necessary to send a current through the field coils in the reverse direction ,. (d] Short Circuits or Grounds in Dynamo or Exter- nal Circuits. A dynamo is liable to be overloaded through bad insulation of the dynamo or external circuits, resulting in a considerable leakage of current, in which case the ammeter will probably not indicate the fact. To ascertain if this is the case, connect a piece of insulated wire to one of the terminals of the machine while running, and then make short momentary contacts with the ground through a water pipe, or frame of the dynamo, or other body in good connection with the earth. If a flash occurs, it proves that the insulation is defective somewhere. This test should be applied to each of the terminals in turn. The fault should next be located by taking the mains to the external circuit out of the terminals of the machine, and again testing as before. If a flash again occurs, it proves that the defect exists in the dynamo, which should be stopped, and the terminals, &c., tested with a battery and galvanometer, as directed in A (11) (Short Circuits in Dynamo). It must be clearly understood that a fault of this description is SPARKING AT BRUSHES. 1 77 just as likely to occur in the external circuit, and therefore, if after removing the mains from the terminals of the machine, and again testing, the flash disappears, it may be taken that the fault is in the external circuit, which should be tested in a similar manner to the dynamo. B (5.) Loose Connections, Terminals, &c. When any of the connecting cables, terminal screws, &c., securing the different circuits are loose, sparking at the brushes, as a rule, results, for the reason that the vibration of the machine tends to continually alter the resistance of the various circuits to which they are connected. When the connections are excessively loose, sparking also results at their points of contact, and by this indication the faulty connections may be readily detected. When this sparking at the contacts is absent, the whole of the connections should be carefully examined and tested as in A (2) (Defective Contacts). B (6.) Disconnections in Armature Circuit. If there is a broken circuit in the armature, as sometimes happens, through a fracture of the armature connec- tions, &c, there will be serious flashing or sparking at the brushes, which cannot be suppressed by adjusting the rocker. As a rule it results in the production of " flats " upon one or more bars of the commutator. If it is impossible to stop the machine, the sparking may be much reduced by placing one of the brushes in each set a little in advance of the others, so as to bridge across the disconnection. If the machine is only provided with one brush on each side of the commutator, a bit of copper wire may be fixed in each holder, so as to project slightly in front of the M 1/8 FAULTS IN DYNAMOS. brushes, and thus bridge over the broken circuit. The localisation and repair of this fault is described in Chapter XII. (Faults in Armatures). B (7.) Short Circuits in Armature Circuit. This fault is indicated by sparking at the commutator, and in bad cases by an excessive heating of the armature, dimming of the light, and slipping of the belt, and in the case of drum armatures by a sudden cessation of the current. The localisation and repair of the different classes of short circuits is referred to in the succeeding chapter (Faults in Armatures). B (8.) Short Circuits or Disconnections in Field Magnet Circuit. Either of these faults is liable to give rise to sparking at the commutator. If one of the coils is short circuited, the fact will be indicated by the faulty coil remaining cool while the perfect coil is overheated. The fault may arise through some of the connections to the coils making contact with the frame of the machine or each other. To ascertain this, examine all the connections, and test with a battery and galvanometer in the manner described in A (2), A (6), A (i i). A total disconnection in one or more of the field coils may readily be detected by means of the battery and galvanometer. A partial disconnection is not, however, so readily discovered, for the reason that the coil wires may be in sufficiently close contact to give a deflection of the galvanometer needle. The only methods of detecting this fault is by measuring the resistance of the coils with an Ohmeter or Wheatstone Bridge, or by placing an ammeter in circuit with each coil in turn, and com- paring the amount of current flowing in each. If the short circuit is not accessible, the only way to remedy EXCESSIVE HEATING. the fault is to re-wind the coil, and the same applies to a disconnection if in the interior of the coil. C. Excessive Heating". The excessive heating of the constituent parts of a dynamo is probably the most common and at the same time the most annoy- ing fault which arises in the working of the dynamo. It may be due to various causes, electrical or mechani- cal ; and may occur in any one or more of the com- ponent parts of the dynamo : (i.) Connections. (2.) Armature, commutator, brushes. (3.) Field magnets. (4.) Bearings. It may be detected by applying the hand to the different portions of the machine if low tension, or a thermometer if high tension, as directed in Chapter X. (Running Dynamos), and also by a smell of over- heated insulation and paint or varnish. When this last indication is felt, it is advisable to stop the machine at once, otherwise the insulation is liable to be destroyed. C (i.) Heating of Connections. This may proceed from either or both (^ OF THE Jk UNIVERSITY) OF y 202 FAULTS IN ARMATURES. nearly always on the commutator end in the last half of the winding, where the wires pass down through the first half terminals. This applies to an unequal winding. In armatures where the windings are equal, it is as liable to occur at one point as at another. With this method a defect can be found and remedied in a few moments, for it has always been a simple matter to repair it when discovered. These results can be observed in a perfect armature by connecting the opposite sections of the commutator. The above will be understood to apply to armatures having Siemens winding." Faults of this description can frequently be discovered by a careful inspection of the windings of the armature without recourse to testing. When located, the fault can usually be repaired with a hardwood wedge, as explained above, or a piece of mica or vulcanised fibre cemented in place with shellac varnish. (c) Short Circuits between Sections through Frame or Core of Armature. The localisation of this fault can be effected by the methods described above, and by disconnecting the whole of the armature coils from the commutator and from each other, and testing each separately with a battery and galvanometer coupled up as in Fig. 74, one wire being connected to the shaft and the other to the end of the coil under test. As a rule, there is no way of remedying this fault other than unwinding the defective coils, reinstating the core, and rewinding new coils. (d) Short Circuits between Sections through Bind- ing Wires. This fault is the result of a loose winding, and is caused by the insulation upon which the bind- ing wires are wound giving way, thus bringing coils GROUNDS IN ARMATURES. 203 at different potentials together. As a consequence to the heavy current which flows, the binding wires are as a rule unsoldered or burned. The location of the fault can therefore be effected by simple inspection. To remedy, it will be necessary to unwind and rewind on new binding wires, on bands of mica or vulcanised fibre, soldering at intervals to obviate flying asunder. (i) Partial Short Circuits in Armatures. This is, as a rule, due to the presence of moisture in the windings. To remedy, the armature should be taken out and exposed to a moderate dry heat, or sub- jected to a current equal to that ordinarily given by the dynamo. Under the action of heat or of this current the moisture will be gradually dispersed. When thoroughly dry, and whilst still warm, a coat of shellac or rubber varnish should be applied to the whole of the windings. (2.) Grounds in Armatures. (#.) Armature Coils grounded or connected to Core or Frame of Armature. When this fault is confined to a single coil, it is not in itself liable to do any damage. If, however, a similar fault develops in some other part of the dynamo, or in the external circuit, the coil is liable to be burned out. Mr F. Bain, in the Western Electrician, has described a simple method of locating a coil grounded to the frame of an armature, which is reprinted below. Fig. 80 clearly shows the arrangements of the details. B is a battery or dynamo circuit, giving a current of a few amperes through the armature by its own brushes (i and 2). At A, a roughly-made galvanometer, to carry some 25 amperes or so, is placed, one terminal being in connection with the shaft of the armature, and the 2O4 FAULTS IN ARMATURES. other attached to a movable brush (3). Since the function of the particular galvanometer is simply to show a deflection when a current is passing, and to mark zero when there is none, a coil of thick wire, with a pocket-compass in the centre, will do all that is required, but care must be taken to remove it sufficiently far away from the disturbing effects of the armature magnetism. The manner of testing is as follows : Assume a steady current to be flowing FIG. 80. from battery (B) through the armature, touch the com- mutator with brush (3), and a current will flow through (G). Slowly rotate the armature or the brush (3), until the galvanometer (G) shows no deflection. The coil in contact with 3 will be found to be grounded or con- nected to the frame. A hand regulator or rheostat (R) may be inserted in series with the battery or dynamo circuit to regulate the strength of the current passing. The main advantage of this test is that the damaged DISCONNECTIONS IN ARMATURES. 205 coil can be located without unsoldering the coils from the commutator, which is sometimes a difficult opera- tion without proper tools ; and further, the fault can frequently be repaired without disconnecting any of the wires if its exact position be determined. (3.) Disconnections in Armature Circuit. A partial or complete disconnection in the armature circuit is always characterised by heavy sparking at the commutator, but not, as a rule, by an excessive heating of the armature or slipping of the belt, and this enables this fault to be distinguished from a short circuit. The faulty part can always be readily located by the " flat " which it produces upon the surface of the commutator. The armature circuit being open at the faulty part, heavy sparking results at every half revolution as the brushes pass over it, and as a consequence the corresponding segments are "pitted" or " flattened " with respect to the others, and may easily be discovered on examination. The fault may occur in either the commutator or in the coils of the armature. To ascertain whether it is in the latter, carefully examine the winding of the faulty coil. The defect may be sought for more particularly at the commutator end of the armature, as breaks in the wire are most frequent where the connections are made with the commutator segments. If no break can be discerned, try passing a heavy current through the faulty coil by means of the brushes. If a discon- nection exists in sufficient contact to pass a current, the coil will be heated in the neighbourhood of the disconnection, and may be discovered by running the fingers over the coil. When located, the fault may be repaired by rewinding the coil, or carefully 2O6 FAULTS IN ARMATURES. cleaning the broken ends and jointing. The fault may also be temporarily repaired by soldering the adjacent commutator segments together without disconnecting the coil. (4.) Flats on Commutator. This is the name given to a peculiar fault which develops on one or more bars of the commutator. It is not confined to dynamos of bad design or construction, but frequently appears on those of the highest class, and may be recognised as a " pitting " or " flattening " of one or more segments. It is always accompanied by spark- ing at the brushes, and may be due to a periodical jumping of the brushes, caused by a bad state of the commutator, or a bad joint in the driving belt, or to a flaw, or a difference in the composition of the metal of the particular bar upon which it appears. But more frequently it may be traced to a more or less developed fault, such as a disconnection, either partial or complete, in the armature coil. The dis- connection may occur either in the coil itself, or at the point where its ends make connection with the lug of the commutator, or at the point where the lug is soldered to the segment of the commutator. To remedy the fault, the brushes should be examined to see if any periodical vibration takes place. If such is the case, the cause should be removed, and the flat carefully filed or turned out, and the brushes readjusted. If it is due to a difference in the com- position of the metal of which the segment is made, the flat will exist as long as the particular segment is in use, and will need to be periodically turned out if a new segment is not fitted into the commutator. Now that the construction of commutators has been FLATS ON COMMUTATORS. 2O? improved, however, by the use of hard-drawn copper or phosphor-bronze segments, this fault is rarely due to this last-mentioned cause. It is more frequently due to bad soldering, or jointing of the conductors to the lugs, or of the lugs to the segments. In all cases of flats, if the disconnection in the armature circuit is not complete, and cannot be readily located, the effect of re-soldering or sweating the ends of the coils into the lugs should be tried. Flats may also frequently be cured by drilling and tapping a small hole in the junction between the lug and the segment, and inserting a small screw, or bit of screwed copper FIG. 81. or brass wire, as shown in Fig. 81, afterwards filing down level with the surface of the commutator. (5.) Short Circuits in Commutator. These are of frequent occurrence, and result in heating of the armature and sparking at the brushes. They are caused either by metallic dust or particles lodging in the insulation between the segments, or by the deterioration of the commutator insulation. To remedy, the insulation between the segments should be carefully examined, and any metallic dust, filings, or burrs cleaned or scraped out. When the com- 2O8 FAULTS IN ARMATURES. mutator is insulated with asbestos or pasteboard (as is oftentimes the case in dynamos of continental make), short circuits very frequently occur through the insulation absorbing moisture or oil, which is subsequently carbonised by the sparking at the brushes. In faults of this description the only remedy is to expel all moisture from the commutator insulation by means of heat, and scrape out all metallic dust which may be embedded in the surface of the insulation. If this does not effect a cure, it will be necessary to dig out the insulation, as far as possible, with a sharp tool, and drive in new insulation ; oil should not be used on commutators insulated with these materials, but only asbestos dust or French chalk. (6.) Rough and Uneven Surface of Commutator. This fault is due to bad adjustment of brushes, bad construction of commutator, and to neglect generally. If allowed to continue, it results in heavy sparking at the brushes, and the eventual destruction of the commutator. The fault may be remedied by filing or turning up the commutator in the manner explained in Chapter XL (Re-Turning Commutator). (7.) Segments Loose or Knocked in. When the segments are loose, it is an indication that the clamping ring or cone has worked loose. This should therefore be tightened up, and the commutator turned up. When the commutator receives an accidental blow, one or more of the segments is invariably forced below the level of the others. In this con- dition the commutator is practically useless. To remedy, two courses are open : the commutator surface may be turned down to the level of the SEGMENTS KNOCKED IN. knocked-in segment, or the latter may be pulled out again to its former level, this latter being the preferable method, if it can possibly be effected. To pull out the segment, a hand vice is firmly clamped to the lug, or a loop of copper wire is passed round the conductor where it joins on to the commutator. A bar of iron to act as a lever is supported on a fulcrum over the commutator, and one end of the bar is passed through the loop or vice. On pressure being applied to the other end, the knocked-in segment can generally be brought up to its former level. The commutator can then be filed up with a dead smooth file. INDEX. PAGE A CTIVITY, electrical - 9 ^*" Ammeter - 4 Armatures 36 types of - - - 40 ring - - - - 41, 48 drum - - - 44, 48, 50 multipolar - - - 48, 50 cores of - - 58, 59, 60 ventilation of - - 61 conductors of - 63 connectors of - - 64 grounds in - - - 203 driving spokes or spiders of - - - - 60 drivers of - - 62 Armature, incorrectly placed in armature chamber - 187 knocking against pole pieces - - 191, 193 out of balance - - 191 Automatic cutouts - 122 regulation - - - 104 regulator brushes - - 104 TDATTERY, testing - - 152 *-* Bearings, heating of 180, 183 dirt, grit, etc., in 185 Bearings (continued) : badly proportioned - 189 out of line - - -189 defective -' - 185, 193 knocking of shaft against 190 end pressure of shaft against - - - 186 Belts --- 135 joints in - - 190, 195 too tight - - - 185 slack or dirty - - 193 Binding wires - - - 67 Brushes - - - - 69 gauze .... 70 wire - - - - 70 strip - - 71 carbon - - - - 71 adjustment of 137, 171, 190 adjustment of, bad 171, 190 attention to - - 145 trimming - - 147 sparking at - 53, 170 position of - - - 52 bedding - - 138 filing - - - - 139 pressure of - - - 52 out of neutral points - 158 bad condition of - - 172 INDEX. 211 Brush-holders short circuits in Brush rockers Brush's automatic regulator - PAGE 71 167 73 105 /CARBON Brushes - ^ Circuits 71 7 fall of pressure in 3 open - - 9, 160, 162 Commutator, segments of, loose or knocked in - 208 Kapp 68 lugs - - - - 69 Commutators - - - 33, 68 construction of - - 68 position of brushes on 52, 108 attention to - - 144, 149 lubricant on - - - 147 flats on - 206 short circuits in 71, 146, 169, 1 80, 207 bad condition of - 172, 208 re-turning - - 173 heating of - - 180 Conductivity, testing for - 154 Conductors and non-conductors 5 armature 63 laminated 63 Connections, incorrect - 159, 195 loose - - 177, 190 heating of - 179 Contacts, defective 158, 179, 190 Cores, armature - - - 58 disc ... 58 toothed - - - 59 insulation of- - - 60 eddy currents in - - 181 Current, electrical - - 4 unit of - - - - 4 commutating 33 pulsating - 35 Current (continued) : excessive - 175, 179, 1 80 Currents, eddy - 56, 181, 182 Curve of saturation - - 23 Curves, characteristic - - 80, 83 TT\ RIVERS 62 ^-^ Dynamo, foundations of 133 simple - - - 29 parts of - - - 36 Dynamos, classification of - 77 separately excited - - 77 series - - - - 79 shunt - - - - 82 compound - - - 85 fixing - - - - 135 attention to - - - 142 characteristic curves of - 80, 83 shutting down - - 148 connecting up - - 99 self-excitation of - - 76 failure to excite - - 157 heating of - - - 179^ vibration of - - - 189 variation of voltage of - 194 variation of speed of - 192 short circuits in - 167, 176 overload of - - 174, 192 reversal of polarity of - 176 182 106 i currents 56, 181, *-** Electric governor - Electrical pressure - - resistance ... current- ... Electro-magnetism - Electro-magnets - - curve of saturation of Electro-motive force - unit of - 22 4 18 , 75 23 212 INDEX. PAGE Electro-motive force (continued] : Heating of dynamos - PAGE 179 induced - - - 27, 30 armatures 180 value of - - - 28, 31 field magnets 181 direction of - - 27, 29, 31 bearings 183 of armatures- 35, 43, 47, 51 connections - 179 E.M.F., value of - - 35 Height of foundations - 134 Excessive current 175, 179, 180 Holders, brush - 7 1 voltage - - 175, 195 Hopkinson connectors - 65 Excitation of field magnets - 75 armature 65 self-excitation - - 76 Horse-power n TT^IELDS, magnetic- - 13 Field coils, coupling up 98, 99 acting in opposition - 166 short circuits in T NDUCTION, electro- * magnetic Insulators - 26 5 169, 178, 182, 195 open circuits in Insulation, testing for - defective 155 176 1 60, 178, 182, 195 of core discs 60 moisture of - - 182 Fixing dynamos - - 135 Filing brushes - - 139 JAMIESON'S rules 20 Flats on commutators - - 206 Journals too tight 184 Fleming's rule 29 badly fitted - I8 5 Foundations of dynamo - 133 brick .... 133 stone .... 133 T^" APP commutator - 68 concrete - - 134 connectors 66 bad .... 190 armatures - 66,67 Kilo-watt - ii PALVANOMETER- Knocked-in segments - 208 ^-* testing - - 152 Gauze brushes - - - 70 Governor, electric - - 106 T AM IN ATED conductors 63 Gramme armature - - 41 Laws of ^electrical re- Grounds in armatures - - 203 sistance - 5 dynamos - - - 176 Lines of force 14 external circuit - - 176 cutting 26 Loose segments - 208 Lubricators, adjusting - 140 TJ" AND regulators - - 102 Lubricant on commutator 1 47 ^ incorrectly adjusted - 159 Lubrication, defective - 184 INDEX. 213 PAGE TV/TAGNETIC fields - 13 *X* intensity of - 15 graphic representation of 16 distortion of - - 54 Magnetism, electro- - - 18 residual 24 insufficient - - - 14 Magnets, electro- - - 22 field .... 89 construction of - - 90 forms of - - - 90 salient pole - - - 91 consequent pole - - 94 multipolar - - - 95 windings of - - - 97 Moisture in field coils - - 182 armatures - - 181, 203 Multipolar field magnets - 95 armatures - - - 48, 50 ring .... 48 drum - - - - 50 "\J EGATIVE potential - 2 Neutral points - - 49, 53 brushes out of - 1 58 Neutral lines - - - 53 -' Open circuits in arma- tures - 1 60, 177, 195 field coils 1 60, 178, 195 external circuit - 162 Overload of dynamos - 174? 192 Over-compounded dynamos - 113 PARALLEL circuits - 7 * connections - - 116 shunt dynamos in - 1 1 8 series dynamos in - 124 compound dynamos in 128 PAGE Points, neutral - - - 49> 53 brushes out of Pole pieces - - - - 90 armature knocking against - - 191, 193 Potential, difference of 5 positive i negative ... 2 Power, electrical - - - 9 horse - - - - II unit of - - - - 9 Pressure, electrical - - I fall of - 2 Pulsating currents - - 35 T3 EGULATING series dynamos - - - 103 shunt dynamos - - 109 separately excited dynamos 100 compound dynamos - 112 over-compounded dynamos 113 Regulators, hand - - 102 Residual magnetism - - 24 insufficient - - - 164 Resistance, electrical - - 4 laws of 5 unit of - - - - 5 Reversal of polarity of dynamos - - - 176 Ring armature - - - 41 Rockers, brush 73 Rules, Professor Jamieson's 21 Professor Fleming's - 29 practical, for coupling up field coils - - 99 C ALIENT pole field mag- ^ nets - - - - 91 Self-exciting dynamos - - 25 -excitation - - - 76 2I 4 INDEX. Series dynamos - connections - shunt dynamos in - series dynamos in compound dynamos in - 128 circuits armature winding - Shaft, bent or badly turned - 186 couplings, straining of - 191 Short circuits in field coils - 169, 178, 182, 195 armatures 169, 178, 180, 193, i brush-holders terminals commutators 169, I external circuit - n dynamos - - r Shunt dynamos - circuits Shutting down dynamos Siemens armature Solenoids - Sparking, causes of at brushes - Speed, insufficient reduced irregularities of variation of - Spokes, driving, or spiders - Starting dynamos Strip brushes '"TESTING battery and galvanometer PAGE 79 Testing for insulation - PAGE 155 116 for conductivity - 154 117 Terminals, short circuits in - 167 124 loose .... 177 128 7 5* 186 UNIT of electro-motive force 3 191 of electrical current 4 of electrical resistance - 5 . 195 of electrical power 9 193, , 196 > A y\s 167 167 WARIATION of speed of voltage - 192 193 , 207 Ventilation of armatures 61 , 176 Vibration - ... 189 , 176 Volt .... 3 82 Voltage .... i 7 variation of - 193 148 excessive - - 175, 195 44 Voltmeter - ... 3 19 53 170 W ATT - VV kilo 9 ii 159 Wires, binding - - - 67 192 Wire brushes 70 194 Wires, armature - 63 192 60 Windings, armature 41, 44, 4^ V J . 50 armature, series - 51 140 armature, parallel 50 7i field magnet 97 short shunt - 88 long shunt - 88 152 compound - 85 ADVERTISEMENTS. USEFUL WORKS FOR ELECTRICIANS. Crown 8vo, Second Edition, y& pp., ivith 113 Illustrations. Price 73. 6d. cloth. DYNAMO CONSTRUCTION: A Practical Handbook for the use of Engineer-Constructors and Electricians-in-Charge BY JOHN W. URQUHART, ELECTRICIAN. SUMMARY OF CONTENTS. Chap. I. Elements of the Dynamo. Chap. II. Elementary Prin- ciples. Chap. III. Dynamo Field Magnets. Chap. IV. Calculations Respecting Exciting Coils. Chap. V. Details Respecting Exciting Coils. Chap. VI. Form of the Field Magnet. Chap. VII. The Armature. Chap. VIII. The Armature Core. Chap. IX. Armature Winding. Chap. X. Ring Armature Winding. Chap. XI. Drum Armature Winding. Chap. XII. Economic Design. Chap. XIII. Dynamo Governing. Chap. XIV. Output and Efficiency. Chap. XV. Graphical Records. Chap. XVI. Dynamos in Series and Parallel. Chap. XVII. The Dynamo in Electric Lighting. Chap. XVIII. Operative Notes. Chap. XIX. Electro-Depositing Dynamos. Chap. XX. Typical Dynamos. Chap. XXI. The Dynamo as a Motor. Crown 8vo, Second Edition, 300 pages, with 95 Illustrations. Price 53. cloth. ELECTRIC LIGHT FITTING: A HANDBOOK FOR WORKING ELECTRICAL ENGINEERS. BY JOHN W. URQUHART, ELECTRICIAN. SUMMARY OF CONTENTS. Chap. I. Central Station Work. Chap. II. Localising Dynamo Faults, and Observations Respecting Accumulators. Chap. III. Switch-Board and Testing Work. Chap. IV. Arc Light Wiring and Fitting. Chap. V. Wiring for Incandescent Lamps. Chap. VI. Incandescent Lighting of Ships. Chap. VII. Specifications. Chap. VIII. Electrical Fire Riski Chap. IX. Miscellaneous Information. Crown 8vo, 294 //., with 88 Illustrations. Price 73. 6d. cloth. ELECTRIC SHIP -LIGHTING: A Handbook on the Practical Fitting and Running of Ships' Electrical Plant, BY JOHN W. URQUHART, ELECTRICIAN. SUMMARY OF CONTENTS. Chap. I. Shipbuilders' Pre-arrangements. Chap. II. Engines for Electrical Ship-Lighting. Chap. III. Dynamos for Ship-Lighting. Chap. IV. Management of Ship Dynamos. Chap. V. Search Light and Arc Lamps. Chap. VI. Wiring and Fitting of Ships. Chap. VII. Lamp*, Switches, and Cut-Outs. Chap. VIII. Conductivity and Insulation Testing. Chap. IX. Accumulators in Ship-Lighting. Chap. X. Typical Installation. [Continued on next Page. LONDON: CROSBY LOCKWOOD & SON, 7 STATIONERS' HALL COURT, E.C. ADVERTISEMENTS. USEFUL WORKS FOR ELECTRICIANS -Continued. Crown 8vo, Fifth Edition, carefully revised, with large additions, 428 pages, with 153 Illustrations. Price 7s. 6d. cloth. ELECTRIC LIGHT, Its Production and Use. BY JOHN W. URQUHART, ELECTRICIAN. SUMMARY OF CONTENTS. Chap. I. Introduction. Chap. II. Primary and Secondary Batteries. Chap. III. Thermo-Electric Batteries. Chap. IV. Magneto-Electric Generators. Chap. V. Electro-Magneto Electric Machines. Chap. VI. Dynamo-Electric Machines. Chap. VII. General Observations on Machines. Chap. VIII. Transformers and Electricity Meters. Chap. IX. Arc and Incandescent Lamps. Chap. X. Electrical Distribution and Circuits. Chap. XI. Measurement of the Arc Light. Chap. XII. Mathematical Notes. Chap. XIII. Present Application and Cost of the Electric Light. Chap. XIV. Notes on Ship Lighting. Chap. XV. Wiring Tests. Just Published, containing upwards of 3,000 Definitions. Crown $>vo, 630 //., with 350 Illustrations. Price 75. 6d. cloth. THE STANDARD ELECTRICAL DICTIONARY. A Popular Dictionary of Words and Terms used in the Practice of Electrical Engineering. Containing upwards of 3,000 Definitions. By T. O'CONNOR SLOANE, A.M., Ph.D. " The work has many attractive features in it, and is, beyond doubt, a well put together and useful publication. The amount of ground covered may be gathered from the fact that in the index about 5,000 references will be found. The inclusion of such comparatively modern words as 'impedence,' ' reluctance," &c. , shows that the author has desired to be up to date, and indeed there are other indications of carefulness of compilation. The work is one which does the author great credit, and it should prove of great value, especially to students. "Electrical Re-view. Second Edition, thoroughly Revised, with Additions, 308 pages, pocket size, with 60 Illustrations. Price 53. leather. THE ELECTRICAL ENGINEER'S POCKET-BOOK of Modern Rules, Formulae, Tables, and Data. By H, R, KEMPE, M.Jnst.E.E,, AJ.Inst.C.E,, Technical Officer, Postal Telegraphs, SUMMARY OF CONTENTS. The Volume is divided into Twenty-one Sections, as follows : i. Weights and Measures. 2. Units. 3. Temperature. 4. Electro-Chemistry, Primary Batteries, and Accumulators. 5. Electro-Metallurgy. 6. Current. 7. Resistances. 8. Capacity, o. Galvanometers. TO. Fault Testing. n. Wire. 12. Insulated Wire. 13. Electric Light Leads. 14. Electric Lamps, Dynamos, Transformers, Motors, and Electric Locomotion. 15. Rules and Regulations. 16. Telegraph Apparatus. 17. Telephones. 18. Miscellaneous. 19. Mathematical Tables. 20. Foreign Money. 21. Dictionary of Technical Terms. LONDON : CROSBY LOCKWOOD & SON, 7 STATIONERS' HALL COURT, E.C. t3T For Complete Lists, see Catalogue. 7, STATIONERS' HALL COURT, LONDON, E.G. April, 1895. CATALOGUE OF BOOKS INCLUDING NEW AND STANDARD WORKS IN ENGINEERING: CIVIL, MECHANICAL, AND MARINE; ELECTRICITY AND ELECTRICAL ENGINEERING; MINING, METALLURGY; ARCHITECTURE, BUILDING, INDUSTRIAL AND DECORATIVE ARTS; SCIENCE, TRADE AND MANUFACTURES; AGRICULTURE, FARMING, GARDENING; AUCTIONEERING, VALUING AND ESTATE AGENCY; LAW AND MISCELLANEOUS. PUBLISHED BY CROSBY LOCKWOOD & SON. MECHANICAL ENGINEERING, etc. D. K. Clark's Pocket-Book for Mechanical Engineers. THE MECHANICAL ENGINEER'S POCKET-BOOK OF TABLES, FORMULA, RULES AND DATA. A Handy Book of Reference for Daily Use in Engineering Practice. By D. KINNEAR CLARK, M.Inst.C.E., Author of " Railway Machinery," " Tramways," &c. Second Edition, Re- vised and Enlarged. Small 8vo, 700 pages, gs. bound in flexible leather covers, with rounded corners and gilt edges. SUMMARY OF CONTENTS. MATHEMATICAL TABLES. MEASUREMENT OF SURFACES AND SOLIDS. ENGLISH WEIGHTS AND MEASURES. FRENCH METRIC WEIGHTS AND MEA- SURES. FOREIGN WEIGHTS AND MEASURES. MONEYS. SPECIFIC GRAVITY WEIGHT AND VOLUME. MANUFACTURED METALS. STEEL PIPES. BOLTS AND NUTS. SUNDRY ARTICLES IN WROUGHT AND CAST IRON, COPPER, BRASS, LEAD, TIN, ZINC. STRENGTH OF MATERIALS. STRENGTH OF TIMBER. STRENGTH OF CAST IRON. STRENGTH OF WROUGHT IRON. STRENGTH OF STEEL. TENSILE STRENGTH OF COPPER, LEAD, ETC. RESISTANCE OF STONES AND OTHER BUILD- ING MATERIALS. RIVETED JOINTS IN BOILER PLATES. BOILER SHELLS WIRE ROPES AND HEMP ROPES. CHAINS AND CHAIN CABLES. FRAMING. HARDNESS OF METALS, ALLOYS AND STONES. LABOUR OF ANIMALS. MECHANICAL PRIN- CIPLES. GRAVITY AND FALL OF BODIES. ACCELERATING AND RETARDING FORCES. MILL GEARING, SHAFTING, ETC. TRANSMISSION OF MOTIVE POWER. HEAT. COMBUSTION: FUELS. WARMING, VENTILATION, COOKING STOVES. STEAM. STEAM ENGINES AND BOILERS. RAILWAYS. TRAMWAYS. STEAM SHIPS. PUMPING STEAM ENGINES AND PUMPS. COAL GAS, GAS ENGINES, ETC. AIR IN MOTION. COMPRESSED AIR. HOT AIR ENGINES. WATER POWEK. SPEED OF CUTTING TOOLS. COLOURS. ELECTRICAL ENGINEERING. %* OPINIONS OF THE PRESS. " Mr. Clark manifests what is an innate perception ot what is likely to be useful In a pocket' book, and he is really unrivalled in the art of condensation. Very frequently we find the informa- tion on a given subject is supplied by giving a summary description of an experiment, and a state- ment of the results obtained. There is a very excellent steam table, occupying five and-a-half pages ; and there are rules given for several calculations, which rules cannot be found in other pocket-books, as, for example, that on page 497, for getting at the quantity of water io the shape of priming in any kaown weight of steam. It is very difficult to hit upon any mechanical engineer- in? subject concerning which this work supplier no information, and the excellent index at the end adds to its utility. In one word, it is an exceedingly Ivindy and efficient tool, possessed of which the engineer will be saved many a wearisoma calculation, or yet more wearisome hunt through rarious text-books and treatises, and, as such, we can heartily recommend it to our readers, who must not runaway with the idea that Mr. Clark's Pocket-book is only Molesworth in another form. On the contrary, each contains what is not to be found in the other ; and Mr. Clark takes more room and deals at more length with many subjects than Molesworth possibly could." The Engineer. " Jt would be found difficult to compress more matter within a similar compass, or produce a book of 650 pages which should be more compact or convenient for pocket reference. . . . Will be appreciated by mechnaical engineers of all classes." Practical Engine er. "Just the kind of work that practical men require to have near to them. "English Mechanit 2 CROSBY LOCK WOOD <> SON'S CATALOGUE. MR. MUTTON'S PRACTICAL HANDBOOKS. Handbook for Works 9 Managers. THE WORKS' MANAGER'S HANDBOOK OF MODERN RULES, TABLES, AND DATA. For Engineers, Millwrights, and Boiler Makers; Tool Makers, Machinists, and Metal Workers; Iron and Brass Founders, &c. By W. S. HUTTON, Civil and Mechanical Engineer, Author of "The Practical Engineer's Handbook." Fifth Edition, carefully Re- vised, with Additions. In One handsome Volume, medium 8vo, price 155. strongly bound. [Just published. 13" The Author having compiled Rules and Data for his own use in a great variety of modern engineering work, and having found his notes extremely useful, decided to publish them revised to date believing that a practical work, suited to (he DAILY REQUIREMENTS OF MODERN ENGINEERS, would be favourably received. In the Fourth Edition the First Section has been re~written and improved by the addition of numerous Illustrations and new matter relating to STEAM ENGINES and GAS ENGINES. The Second Section has been enlarged and Illustrated, and through- out the book a great number of emendations and alterations have been made, with the object of rendering the book more generally useful. ** OPINIONS OF THE PRESS. " The author treats every subject from the point of view of one who has collected workshop notes for application in workshop rracf '"'*, rather than from the theoretical or literary aspect. The volume contains a great deal oi that kin* of information which is gained only by practical experi- ence, and is seldom written in books.'' Engineer.* "The volume is an exceedingly useful one. brimful with engineers' notes, memoranda, and rules, and well worthy of being on. every mechanical engineer's bookshelf." Mechanical World. " The information is precisely thdt likely to be required in practice. . . . The work forms a desirable addition to the library not only of the works' manager, but of anyone connected with general engineering." Mining Journal. "A formidable mass of facts and figures, readily accessible through an elaborate index . . . . Such a volume will be found absolutely necessary as a book of reference in all sorts of ' works ' connected with the metal trades." Ry land's Iron Trades Circular. " Brimful of useful information, stated in a concise form, Mr. Hutton's books have met a press- ng want among engineers. The book must prove extremely useful to every practical maa possessing a copy." Practical Engineer. New Manual for Practical Engineers. THE PRACTICAL ENGINEER'S HAND-BOOK. Comprising a Treatise on Modern Engines and Boilers': Marine, Locomotive and Sta- tionary. And containing a large collection of Rules and Practical Data relating to recent Practice in Designing and Constructing all kinds of Engines, Boilers, and other Engineering work. The whole constituting a comprehensive Key to the Board of Trade and other Examinations lor Certi- ficates of Competency in Modern Mechanical Engineering. By WALTER S. HUTTON, Civil and Mechanical Engineer, Author of "The Works' Manager's Handbook for Engineers," &c. WiTh upwards of 370 Illustrations. Fourth Edition, Revised, with Additions. Medium 8vo, nearly 500 pp., price i8s. Strongly bound. t3- This work is designed as a companion to the Author's "WORKS' MANAGER'S HAND-BOOK." It possesses many new and original features, and con- tains, like its predecessor, a quantity of matter not originally intended for publica- tion, but collected by the author for his own use in the construction of a great variety of MODERN ENGINEERING WORK. The information is given in a condensed and concise form, and is illustrated by upwards of 370 Woodcuts ; and comprises a quantity of tabulated matter of great value to all engaged in de signing, construct ing, or estimating for ENGINES, BOILERS, and OTHER ENGINEERING WORK. %* OPINIONS OF THE PRESS. " We have kept It at hand for several weeks, referring to it as occasion arose, and we ave not on a single occasion consulted its pages without finding the information of which we were in quest. Athenaum. " A thoroughly good practical handbook, which no engineer can go through without k aiming something that wifl be of service to him." Marine 'Engineer. " An excellent book of reference for engineers, and a valuable text-book for students 01 engineering." Scotsman. "This valuable manual embodies the results and experience of the leading authorities on mechanical engineering." Building IVeivs. " The author has collected together a surprising quantity of rules and practical data, and has shown much judgment in the selections he has made. . . . There is no doubt that this book is one of the most useful of its kind published, and will be a very popular compendium." Engineer. " A mass of information, set down in simple language, and in such a form that it can be easily referred to at any time. The matter is uniformly good and well chosen and is greatly elucidated by the illustrations. The book will find its way on to most engineers' shelves, where it will rank as one of the most useful books of reference." Practical Engineer. " Full of useful information and should be found on the office shelf of all practical engineers." English Mechanic MECHANICAL ENGINEERING, etc. MR. MUTTON'S PRACTICAL HANDBOOKS continued. Practical Treatise on Modern Steam-Boilers. STEAM-BOILER CONSTRUCTION. A Practical Handbook for Engineers, Boiler-Makers, and Steam Users. Containing a large Col- lection of Rules and Data relating to Recent Practice in the Design, Con- struction, and Working of all Kinds of Stationary, Locomotive, and Marine Steam-Boilers. By WALTER S. HUTTON, Civil and Mechanical Engineer, Author of "The Works' Manager's Handbook," "The Practical Engineer's Handbook," &c. With upwards of 300 Illustrations. Second Edition. Medium 8vo, i8s. cloth. tS" This work is issued in continuation of the Series of Handbooks written by the Author, viz ; "THE WORKS' MANAGER'S HANDBOOK'' and "THE PRACTI- CAL ENGINEER'S HANDBOOK," which are so highly appreciated by Engineers for the practical nature of their information ; and is consequently written in the same style as those works. The A uthor believes that the concentration, in a convenient form for easy refer- ence, of such a large amount of thoroughly practical information on Steam-Boilers, will be of considerable service to those for whom it is intended, and he trusts the booh may be deemed worthy of as favourable a reception as has been accorded to its predecessors, *** OPINIONS OF THE PRESS. "Every detail, both In boiler design and management, is clearly laid before the reader. The volume shows that boiler construction has been reduced to the condition of one of the most exact sciences ; and such a book is of the utmost value to the fin de siecle Engineer and Works' Manager. " Marine Engineer. " There has long been room for a modern handbook on steam boilers ; there is not that room now, because Mr. Hutton has filled it. It is a thoroughly practical book for those who are occu- pied in the construction, design, selection, or use of boilers." Engineer. " The book is of so important and comprehensive a character that it must find its way into the libraries of everyone interested in boiler using or boiler manufacture if they wish to be thoroughly informed. We strongly recommend the book for the intrinsic value of its contents." Machinery Market. " The value.t>f this book can hardly be over-estimated. The author's rules, formulae, &c., an all very fresh, and it is impossible to turn to the work and not find what you want. No practical engineer should be without it." Colliery Guardian. Mutton's "Modernised Templeton*" THE PRACTICAL MECHANICS' WORKSHOP COM- PANION. Comprising a great variety of the most useful Rules and Formulae in Mechanical Science, with numerous Tables of Practical Data and Calcu- lated Results for Facilitating Mechanical Operations. By WILLIAM TEMPLE- TON, Author of "The Engineer's Practical Assistant," &c. &c. Seventeenth Edition, Revised, Modernised, and considerably Enlarged by WALTER S. HUTTON, C.E., Author of "The Works' Manager's Handbook," "The Practical Engineer's Handbook,' 1 &c, Fcap. 8vo, nearly 500 pp., with 8 Plates and upwards of 250 Illustrative Diagrams, 6s., strongly bound for workshop or pocket wear and tear. *** OPINIONS OF THE PRESS. " In Its modernised form Hutton's ' Templeton 'should have a wide sale, for It contains much valuable information which the mechanic will often find of use, and not a few tables and notes which he might look for in vain in other works. This modernised edition will be appreciated by all who have learned to value the original editions of ' Templeton.' ' English. Mechanic. " It has met with great success in the engineering workshop, as we can testify ; and there are a great many men who, in a great measure, owe their rise in life to this little book." Building Ne-uts, " This familiar text-book well known to all mechanics and engineers is of essential service ta the every-day requirements of engineers, millwrights, and the various trades connected with engineering and buil !ing. The new modernised edition is worth its weight in gold." Building News. (Second Notice.) " This well-known and largely used book contains information, brought up to date, of the sort so useful to the foreman and draughtsman. So much fresh information has been introduced as to constitute it practically a new book. It will be largely used in the office and workshop." Mechanical World. " The publishers wisely entrusted the task of revision of this popular, valuable, and useful book to Mr. Hutton, than whom a more competent man they could not have found." Iron. Templeton's Engineer's and Machinist's Assistant. THE ENGINEER'S, MILLWRIGHT'S, and MACHINIST'S PRACTICAL ASSISTANT. A collection of Useful Tables, Rules and Data. By WILLIAM THMPLETON. 7th Edition, with Additions. i8mo, zs. 6d. cloth. *** OPINIONS OF THE PRESS. " Occupies a foremost place among books of this kind. A more suitable present to an app: en- tice to any of the mechanical trades could not possibly be made." Buildi-ny Nevis. "A deservedly popular work. It should be in the ' drawer' of every mechanic." r.nylish 4 CROSBY LOCK WOOD & SON'S CATALOGUE. Foley's Office Reference Book for Mechanical Engineers. THE MECHANICAL ENGINEER'S REFERENCE BOOK, for Machine and Boiler Construction. In Two Parts. Part I. GENERAL ENGINEERING DATA. Part II. BOILER CONSTRUCTION. With 51 Plates and numerous Illustrations. By NELSON FOLEY. M.I.N.A. Second Edition, Revised throughout and much Enlarged. Folio, 3 35. net half-bounf 1 . SUMMARY OF CONTENTS. [Just published. PART I. MEASURES. CIRCUMFERENCES AND AREAS, &c., SQUARES, CUBES, FOURTH POWERS. SQUARE AND CUBE ROOTS. SURFACE OF TUBES RECIPROCALS. LOGARITHMS. MENSURATION. SPE- CIFIC GRAVITIES AND WEIGHTS. WORK AND POWER. HEAT. COMBUS- TION. EXPANSION AND CONTRACTION. EXPANSION OF GASES. STEAM. STATIC FORCES. GRAVITATION AND ATTRACTION. MOTION AND COMPUTA- TION OF RESULTING FORCES. ACCU- MULATED WORK. CENTRE AND RADIUS OF GYRATION. MOMENT OF INERTIA, CENTRE OF OSCILLATION. ELEC- TRICITY. STRENGTH OF MATERIALS. ELASTICITY. TEST SHEETS OF METALS. FRICTION. TRANSMISSION OF POWER. FLOW OF LIQUIDS. FLOW OF GASES. AIR PUMPS, SURFACE CON* DENSERS, &c. SPEED OF STEAMSHIPS. PROPELLERS. CUTTING TOOLS. FLANGES. COPPER SHEETS AND TUBES. SCREWS, NUTS, BOLT HEADS, &c. VARIOUS RECIPES AND MISCEL- LANEOUS MATTER. WITH DIAGRAMS FOR VALVE-GEAR, BELTING AND ROPES, DISCHARGE AND SUCTION PIPES, SCREW PROPELLERS, AND COPPER PIPES. PART II. TREATING OF, POWER OF BOILERS. USEFUL RATIOS. NOTES ON CON- STRUCTION. CYLINDRICAL BOILER SHELLS. CIRCULAR FURNACES. FLAT PLATES. STAYS. GIRDERS. RIVETING. BOILER SETTING, CHIM- NEYS, AND MOUNTINGS. FUELS, &c. EXAMPLES OF BOILERS AND SPEEDS OF STEAMSHIPS. NOMINAL AND NORMAL HORSE POWER. SCREWS. HYDRAULIC TESTS. WITH DIAGRAMS FOR ALL BOILER CALCULATIONS AND DRAWINGS OF MANY VARIETIES OF BOILERS. *** OPINIONS OF THE PRESS. " The book is one which every mechanical engineer may, with advantage to himself add to his library." Industries. " Mr. Foley is well fitted to compile such a work. . . . The diagrams are a great feature of the work. . . . Regarding the whole work, it may be very fairly stated that Mr. Foley has produced a volume which will undoubtedly fulfil the desire of the author and become indispen- sable to ah mechanical engineers." Marine Engineer. " We have carefully examined this work, and pronounce it a most excellent reference book for the use of marine engineers." Journal of American Society tf 'Naval Engineers. " A veritable monument of industry on the part of Mr. Fole>, who has succeeded in producing what is simply invaluable to the engineering profession." Steamship. Coal and Speed Tables. A POCKET BOOK OF COAL AND SPEED TABLES, for Engineers and Steam-users. By NELSON FOLEY, Author of " The Mechanical Engineer's Reference Bock>" Pocket-size, 35. 6d. cloth. "These tables are designed to meet the requirements of every-day use ; they are of suffi- cient scope for most practical purposes, and may be commended to engineers and users of steam.?' /r. " This pocket-book well merits the attention of the practical engineer. Mr. Foley has com- piled a very useml set of tables, the information contained in which is frequently required by engineess, coal consumers and users of steam." Iron and Coal Tradtt Review, Steam Engine. TEXT-BOOK ON THE STEAM ENGINE. With a Sup- plement on Gas Engines, and PART II. ON HEAT ENGINES. By T. M. GOODEVE, M.A., Barrister-at-Law, Professor of Mechanics at the Royal College of Science, London; Author of "The Principles of Mechanics," "The Elements of Mechanism," &c. Twelfth Edition, Enlarged. With nu- merous Illustrations. Crown 8vo, 6s. cloth. "Professor Gpodeve has given us a treatise on the steam engine which will bear comparison with anything written by Huxley or Maxwell, and we can award it no higher praise." Engineer. " Mr. Goodeve's text-book is a work of which every young engineer should possess himself." Mining Journal. MECHANICAL ENGINEERING, etc. Gas Engines. ON GAS-ENGINES. With Appendix describing a Recent Engine with Tube Igniter. By T. M. GOODEVE, M.A. Crown 8vo, zs. 6d. cloth. [Just published. " Like all Mr. Goodeve's writings, the present is no exception in point of general excellence. It is a valuable little volume." Mechanical World, Steam Engine Design. A HANDBOOK ON JHE STEAM ENGINE, with especial Reference to Small and Medium-sized Engines. For the Use of Engine- Makers, Mechanical Draughtsmen, Engineering Students and Users of Steam Power. By HERMAN HAEDER, C.E. English Edition, Re-edited by the Author from the Second German Edition, and Translated, with considerable Additions and Alterations, by H. H. P. POWLES, A.M.I.C.E., M.I.M.E. With nearly 1,100 Illustrations. Crown 8vo, gs. cloth. " A perfect encyclopaedia of the steam engine and its details, and one which must take a per- manent place in Engl ; sh drawing-offices and workshops." A Foreman Pattern-maker. " This is an excellent book, and should be in the hands of all who are interested in the con- struction and design of medium-sized stationary engines. ... A careful study of its contents and the arrangement of the sections leads to the conclusion that there is probably no other book amiy may claim a complete achievement ol this idea." Mature. " There can be no question as to its value. We cordially commend it to all concerned in the like it in this country. The volume aims at showing the results of practical experience, and it - Tiis &<&." Nature. We cordially comm design and construction of the steam engine." Mechanical World. Steam Rollers. A TREATISE ON STEAM BOILERS: Their Strength, Con- struction, and Economical Working. By ROBERT WILSON, C.E. Fifth Edition. i2rao, 6s. cloth. "The best treatise that has ever been published on steam boilers." Engineer. "The author shows himself perfect master of his subject, and we heartily recommend all em ploying steam power to possess themselves of the work." Ryland's Iron Trade Circular. Boiler Chimneys. BOILER AND FACTORY CHIMNEYS; Their Draught-Power and Stability. With a Chapter on Lightning Conductors. By ROBERT WILSON, A.I.C.E., Author of "A Treatise on Steam Boilers," &c, Second Edition. Crown 8vo, $s. 6d. cloth. "A valuable contribution to the literature of scientific building." The Builder. Boiler Making. THE BOILER-MAKER'S READY RECKONER & ASSIST- A NT. With Examples of Practical Geometry and Templating, for the Use of Platers, Smiths and Riveters. By JOHN COURTNEY, Edited by D. K. CLARK, M.I.C.E. Third Edition, 480 pp., with i4olllusts. Fcap. 8vo, 7$. half-bound. " No workman or apprentice should be without this book." Iron Ttade Circular. Locomotive Engine Development. THE LOCOMOTIVE ENGINE AND ITS DEVELOPMENT. A Popular Treatise on the Gradual Improvements made in Railway Engines between 1803 and 1894. By CLEMENT E. STRETTON, C.E., Author of " Safe Ra'lway Working," &c. Third Edition, Revised and Enlarged. With 95 Illustrations. Crown 8vo, 2S. 6d. cloth gilt. [Just published. " Students of railway history and all who are interested in the evolution of the modern locomo- tive will find much to attract and entertain in this volume." The Times. " The author of this work is well known to the railway world, and no one probably has a better knowledge of the history and development of the locomotive. The volume btfoie i : should be of value te all connected with the railway system of this country." Nature. Estimating for Engineering Work, uzum. " As a text-book we should advise all surveyors to place It in their libraries, and study well the matured instructions afforded in its pages." Colliery Guardian. " The author brings to his work a fortunate union of theory and practical experience which, aided by a clear and lucid style of writing, renders the book a very useful one" Builder. Surveying, Land and Marine. LAND AND MARINE SUR V EYING, in Referee ce to the Pre- paration of Plans for Roads and Railways ; Canals, Rivers, Towns' Water Supplies; Docks and Harbours. With Description and Use of Surveying Instruments. By W. D. HASKOLL, C.E., Author of " Bridge and Viaduct Con- struction," &c. Second Edition, Revised, with Additions. Large cr.Svo, gs, cl. " This book must prove of great value to the student. We have no hesitation in recommend- ing it, feeling assured that it will more than repay a careful study." Mechanical World. "A most useful and well arranged book. We can strongly recommend it as a carefully-written and valuable text-book. It enjoys a well-deserved repute amongr surveyors." Builder. " This volume cannot fail to prove of the utmost practical utility. It may be safely recommended to all students who aspire to become clean and expert surveyors." Mining Journal. Field-BooJe for Engineers. THE ENGINEER'S, MINING SURVEYOR'S, AND CON- TRACTOR'S FIELD-BOOK. Consisting of a Series of Tables, with Rules, Explanations of Systems, and use of Theodolite for Traverse Surveying and Plotting the Work with minute accuracy by means of Straight Edge and Set Square only ; Levelling with the Theodolite, Casting-out and Reducing Levels to Datum, and Plotting Sections in the ordinary manner; setting-out Curves with the Theodolite by Tangential Angles and Multiples, with Right and Left-hand Readings of the Instrument: Setting-out Curves without Theodolite, on the System of Tangential Angles by sets of Tangents and Off- sets ; and Earthwork Tables to 80 feet deep, calculated for every 6 inches in depth. By W. D. HASKOLL, C.E. Fourth Edition. Crown 8vo, i2s. cloth. "The book is very handy; the separate tables of sines and tangents to every minute will make It useful for many other purposes, the genuine traverse tables existing all the same."Athemzum, " Every person engaged in engineering field operations will estimate the importance of such a work and the amount of valuable time which will be saved by reference to a set of reliable tables prepared with the accuracy and fulness of those given in this volume." Rail-way Newt. Levelling. A TREATISE ON THE PRINCIPLES AND PRACTICE OF LEVELLING. Showing its Application to purposes of Railway and Civil Engineering, in the Construction of Roads; with Mr. TELFORD'S Rules for the same. By FREDERICK W. SIMMS, F.G.S., M.Inst.C.E. Seventh Edition, with the addition of LAW'S Practical Examples for Setting-out Railway Curves, and TRAUTWINE'S Field Practice of Laying-out Circular Curves. With 7 Plates and numerous Woodcuts. 8vo, 8s. 6d. cloth. *#* TRAUTWINE on Curves may be had separate, 55. " The text-book on levelling in most of our engineering schools and colleges." Engineer. " The publishers have rendered a substantial service to the profession, especially to the younger members, by bringing out the present edition of Mr. Simms's useful book "Engineer. CIVIL ENGINEERING, SURVEYING, etc. 15 Trigonometrical Surveying. AN OUTLINE OF THE METHOD OF CONDUCTING A TRIGONOMETRICAL SURVEY, for the Formation of Geographical and Topographical Maps and Plans, Military Reconnaissance, Levelling, 6-c., with Useful Problems, Formulae, and Tables. By Lieut.-General FROME, R.E. Fourth Edition, Revised and partly Re- written by Major General Sir CHARLES WARREN, G.C.M.G., R.E. With 19 Plates and 115 Woodcuts. Royal 8vo, ifis. cloth. " The simple fact that a fourth edition has been called for Is the best testimony to Its merits. No words of praise from us can strengthen the position so well and so steadily maintained by this work. Sir Charles Warren has revised the entire work, and made such additions as were necessary to bring every portion of the contents up to the present date."r0ad Arrov. Field Fortification. A TREATISE ON FIELD FORTIFICATION, THE ATTACK OF FORTRESSES, MILITARY MINING, AND RECONNOITRING. By Colonel I. S. MACAULAY, late Professor of Fortification in the R.M.A., Wool- wich, Sixth Edition. Crown 8vo, with separate Atlas of la Plates, izs. cloth. Tunnelling. PR A CTICAL TUNNELLING. Explaining In detail the Setting, out of the works, Shaft-sinking and Heading-driving, Ranging the Lines and Levelling underground, Sub-Excavating, Timbering, and the Construction of the Brickwork of Tunnels, with the amount of Labour required for, and the Cost of, the various portions of the work. By FREDERICK W. SIMMS, F.G.S., M.Inst.C.E. Third Edition, Revised and Extended by D. KINNEAR CLARK, M.Inst.C.E. Imperial 8vo, with ai Folding Plates and numerous Wood Engravings, 30$. cloth. " The estimation in which Mr. Slmms's book on tunnelling has been held for over thirty years cannot be more truly expressed than in the words of the late Prof. Rankine : ' The best source of in- formation or the subject of tunnels is Mr.F.W.Simms's work on Practical Tunnelling.' "Architect. " It has been regarded from the first as a text-book of the subject. . . . Mr. Clark has added Immensely to the value of the book." Engineer. Tramways and their Wording. TRAMWAYS : THEIR CONSTRUCTION AND WORKING. Embracing a Comprehensive History of the System ; with an exhaustive Analysis of the various Modes of Traction, including Horse-Power, Steam, Cable Traction, Electric Traction, &c.; a Description of the Varieties of Roll- ing Stock ; and ample Details of Cost and Working Expenses. New Edition, Thoroughly Revised, and Including the Progress recently made in Tramway Construction, &c. &c. By D. KINNEAR CLARK. M.Inst.C.E. With numerous Illustrations and Folding Plates. In One Volume, 8vo, 780 pages, price 285., bound in buckram. [ Just published. " All interested in tramways must refer to it, as all railway engineers have turned to the author's work ' Railway Machinery." " Engineer. " An exhaustive and practical work on tramways, In which the history of this kind of locomo- tion, and a description and cost of the various modes of laying tramways, are to be found.'' Building Nevis. " The best form of rails, the best mode of construction, and the best mechanical appliances are so fairly indicated in the work under review, that any engineer about to construct a tramway will be enabled at once to obtain the practical information which will be of most service to him." Athenceum. Curves, Tables for Setting-out. TABLES OF TANGENTIAL ANGLES AND MULTIPLES for Setting-out Curves from 5 to 200 Radius. By ALEXANDER BEAZELEY, M.Inst.C.E. Fourth Edition. Printed on 48 Cards, and sold in a cloth box, waistcoat-pocket size, 35. 6d. " Each table is printed on a small card, which, being placed on the theodolite, leaves the hands free to manipulate the instrument no small advantage as regards the rapidity of work." Engineer. " Very handy ; a man may know that all his day's work must fall on two of these cards, which he puts into his own card-case, and leaves the rest behind." A thenaum. Earthwork. EARTHWORK TABLES. Showing the Contents in Cubic Yards of Embankments, Cuttings, &c., of Heights or Depths up to an average of 80 feet. By JOSEPH BROADBENT, C.E., and FRANCIS CAMPIN, C.E. Crown 8vo, 55. cloth. " The way in which accuracy Is attained, by a simple division of each cross section Into three elements, two in which are constant and one variable, is ingenious." Athenaeum. 16 CROSBY LOCK WOOD & SON'S CATALOGUE. Water Supply and Water-Works. THE WATER SUPPLY OF TOWNS AND THE CON- STRUCTION OF WATER-WORKS: A Practical Treatise for the Use of Engineers and Students of Engineering. By W. K. BURTON, A.M.Inst.C E., Professor of Sanitary Engineering in the Imperial University, Tokyo, Japan, and Consulting Engineer to the Tokyo Water-works. With an Appendix on the Effects of Earthquakes on Waterworks, by JOHN MILNE, F.R.S., Pro- fessor of Mining in the Imperial University of Japan. With numerous Plates and Illustrations. Super-royal 8vo, 255. buckram. [Just published. ' The whole art of waterworks construction is dealt with in a clear and comprehensive fashion in this handsome volume. . . . Mr. Burton's practical treatise shows in all its sections the fruit of independent study and individual experience. It is largely based upon his own practice in the branch of engineering of which it treats, and with such a basis a treatise can scarcely fail to be sug- gestive and useful." Saturday Review. "Professor Burton's book is sure of a warm welcome among engineers. It is written in clear and vigorous language and forms an exhaustive treatise on a branch of engineering the claims ot which it would be difficult to over-estimate." Scotsman. "The subjects seem to us to be ably discussed, with a practical aim to meet the requirements of all its probable readers. The volume is -.veil got up, and the illustrations are excellent." The Lancet. Seat, Expansion by. EXPANSION OF STRUCTURES BY HEAT. By JOHN KEILV, C.E., late of the Indian Public Works and Victorian Railway Depart- ments, Crown 8vo, 33. 6d. cloth. SUMMARY OF CONTENTS. Section I. FORMULAS AND DATA, Section II. METAL BARS. Section III. SIMPLE FRAMES. Section IV. COMPLEX FRAMES AND PLATES. Section V. THERMAL CONDUCTIVITY. Section VI. MECHANICAL FORCE OF HEAT. Section VII. WORK OF EXPANSION AND CONTRACTION. Section VIII. SUSPENSION BRIDGES. Section IX. MASONRY STRUCTURES. " The aim the author has set before him, viz., to show the effects of heat upon metallic and other structures, is a laudable one, for this is a branch of physics upon which the engineer or archi- tect can find but little reliable and comprehensive data in books." Builder. " Whoever is concerned to know the effect of changes of temperature on such structures as suspension bridges and the like, could not do better than consult Mr. Keily's valuable and handy exposition of the geometrical principles involved in these changes." Scotsman. Earthwork, Measurement of. A MANUAL ON EARTHWORK. By ALEX. J. S. GRAHAM, C.E. With numerous Diagrams. Second Edition. i8mo, 2s. 6d. cloth. " A great amount of practical information, very admirably arranged, and available for rough estimates, as well as for the more exact calculations required in the engineer's and contractor'! offices. 'Artisan. Strains in Ironwork. THE STRAINS ON STRUCTURES OF IRONWORK; with Practical Remarks on Iron Construction. By F. W. SHEILDS, M.InstC.E. Second Edition, with 5 Plates. Royal 8vo, 55. cloth. The student cannot find a better little book on this subject" Engineer. Cast Iron and other Metals, Strength of. A PRACTICAL ESSAY ON THE STRENGTH OF CAST IRON AND OTHER METALS. By THOMAS TREDGOLD, C.E. Fifth Edition, including HODGKINSON'S Experimental Researches. 8vo, its. cloth. Oblique Arches. A PRACTICAL TREATISE ON THE CONSTRUCTION OF OBLIQUE ARCHES. By JOHN HART. Third Edition, with Plates. Im- perial Bvo, 8s. cloth. Girders, Strength of. GRAPHIC TABLE FOR FACILITATING THE COMPUTA- TION OF THE WEIGHTS OF WROUGHT IRON AND STEEL GIRDERS, etc., for Parliamentary and other Estimates. By J. H. WATSCN BUCK, M.Inst.C.E. On a Sheet, zs, 6d. MARINE ENGINEERING, NAVIGATION, etc. MARINE ENGINEERING, SHIPBUILDING, NAVIGATION, etc. Focket-Bookfor Naval Architects and Shipbuilders, THE NAVAL ARCHITECT'S AND SHIPBUILDER'* POCKET-BOOK of Formula, Rules, and Tables,and MARINE ENGINEER'S AND SURVEYOR'S Handy Book of Reference. By CLEMENT MACKROW, Member of the Institution of Naval Architects, Naval Draughtsman. Fifth Edition, Revised and Enlarged to 700 pages, with upwards of 300 Illustra- tions. Fcap., I2S. 64. strongl} bound in leather. SUMMARY OF CONTENTS. SIGNS AND SYMBOLS, DECIMAL FRAC- TIONS. TRIGONOMETRY. PRACTICAL GEOMETRY. MENSURATION. CEN- TRES AND MOMENTS OF FIGURES. MOMENTS OF INERTIA AND RADII OF GYRATION. ALGEBRAICAL EXPRES- SIONS FOR SIMPSON'S RULES. ME- CHANICAL PRINCIPLES. CENTRE OF GRAVITY. LAWS OF MOTION. DIS- PLACEMENT, CENTRE OF BUOYANCY. CENTRE OF GRAVITY OF SHIP'S HULL. STABILITY CURVES AND METACEN- TRES. SEA AND SHALLOW-WATER WAVES. ROLLING OF SHIPS. PRO- PULSION AND RESISTANCE OF VESSELS. SPEED TRIALS. SAILING, CENTRE OF EFFORT. DISTANCES DOWN RIVERS, COAST LINES. STEERING AND RUD- DERS OF VESSELS. LAUNCHING CAL- CULATIONS AND VELOCITIES. WEIGHT OF MATERIAL AND GEAR. GUN PAR- TICULARS AND WEIGHT. STANDARD GAUGES. RIVETED JOINTS AND RIVET- ING. STRENGTH AND TESTS OF MATE- RIALS. BINDING AND SHEARING STRESSES.ETC. STRENGTH OF SHAFT- ING, PILLARS, WHEELS, ETC. HY- DRAULIC DATA, ETC. CONIC SECTIONS, CATENARIAN CURVES. MECHANICAL POWERS, WORK. BOARD OF TRADE REGULATIONS FOR BOILERS AND EN- GINES. BOARD OF TRADE REGULA- FOR BOILERS. LLOYD'S WEIGHT OF CHAINS. LLOYD'S SCANTLINGS FOR SHIPS. DATA OF ENGINES AND VES- SELS. - SHIPS' FITTINGS AND TESTS. SEASONING PRESERVING TIMBER. MEASUREMENT OF TIMBER. ALLOYS, PAINTS, VARNISHES. DATA FOR STOWAGE. ADMIRALTY TRANSPORT REGULATIONS. RULES FOR HORSE- POWER, SCREW PROPELLERS, ETC. PERCENTAGES FOR BUTT STRAPS. ETC. PARTICULARS OF YACHTS. MASTING AND RIGGING VESSELS. DISTANCES OF FOREIGN PORTS. TONNAGE TABLES. VOCABULARY OF FRENCH AND ENGLISH TERMS. ENGLISH WEIGHTS AND MEASURES FOREIGN WEIGHTS AND MEASURES. DECIMAL EQUIVALENTS. FOREIGN MONEY. DISCOUNT AND WAGE TABLES. USE- FUL NUMBERS AND READY RECKONERS TABLES OF CIRCULAR MEASURES. TABLES OF AREAS OF AND CIRCUM- FERENCES OF CIRCLES. TABLES OF AREAS OF SEGMENTS OF CIRCLES. TABLES OF SQUARES AND CUBES AND ROOTS OF NUMBERS. TABLES OF LOGARITHMS OF NUMBERS. TABLES OF HYPERBOLICLOGARITHMS. TABLES OF NATURAL SINES, TANGENTS, ETC. TABLES OF LOGARITHMIC SINES, TANGENTS, ETC. TIONS FOR SHIPS. LLOYD'S RULES " In these days of advanced knowledge a work like this is of the greatest value. It contains a vast ^amount of information. We unhesitatingly say that it is the most valuable compilation for its specific purpose that has ever been printed. No naval architect, engineer, surveyor, or seaman, wood or iron shipbuilder, can afford to be without this work." Nautical Magazine. "Should be used by all who are engaged in the construction or designs of vessels. . . . Will be found to contain the most useful tables and formulae required by shipbuilders, carefully collected from the best authorities, and put together in a popular and simple form." Engineer. " The professional shipbuilder has now, in a convenient and accessible form, reliable data for solving 1 many of the numerous problems that present themselves in the course of his work." Iron. ''There is no doubt that a pocket-book of this description must be a necessity in the ship- building trade. . . . The volume contains a mass of useful information clearly expressed and presented in a handy form." Marine Engineer. Marine Engineering. MARINE ENGINES AND STEAM VESSELS (A Treatise on). By ROBERT MURRAY, C.E. Eighth Edition, thoroughly Revised, with considerable Additions by the Author and by GEORGE CARLISLE, C.E., Senior Surveyor to the Board of Trade at Liverpool. i2mo, 55. cloth boards. " Well adapted to give the young steamship engineer or marine engine and boiicr maker a general introduction into his practical work." Mechanical World. " We feel sure that this thoroughly revised edition will continue to be as popular in the future as it has been in the past, as, for its size, it contains more useful information than ny similar treatise. " Industries. " As a compendious and useful guide to engineers of our mercantile and royal na-.al services, we should say it cannot be surpassed." Building Nevis. " The information given is both sound and sensible, and well qualified to direct young sea- going hands on the straight road to the extra chief's certificate. . . . Most useful 1o surveyors, inspectors, draughtsmen, and young engineers." Glasgow Herald. C i8 CROSBY LOCKWOOD & SON'S CATALOGUE. Poc/cet-BooTc for Marine Engineers. A POCKET-BOOK OF USEFUL TABLES AND FOR- MULJE FOR MARINE ENGINEERS. By FRANK PROCTOR, A.I.N.A, Third Edition. Royal 32010, leather, gilt edges, with strap, 45. "We recommend it to our readers as going far to supply a long-felt want." Naval Science, "A most useful companion to all marine engineers." United Service Gazed = :/=, Introduction to Marine Engineering. ELEMENTARY ENGINEERING: A Manual for Young Marine Engineers and Apprentices. In the Form of Questions and Answers on Metals, Alloys, Strength of Materials, Construction and Management ;'ot Marine Engines and Boilers, Geometry, &c. &c. With an Appendix of Useful Tables. By JOHN SHERREN BREWER, Government Marine Surveyor, Hong- kong. Second Edition, Revised. Small crown 8vo, zs. cloth. " Contains much valuable information for the class for whom it is intended, especially In the chapters on the management of boilers and engines." Nautical Magazine. " A useful introduction to the more elaborate text-books." Scotsman. " To a student who has the requisite desire and resolve to attain a thorough knowledge, Mr. Brewer offers decidedly useful help." Athenaum. Navigation. PRACTICAL NAVIGATION. Consisting of THE SAILOR'S SEA-BOOK, by JAMES GREENWOOD and W. H. ROSSER together with the requisite Mathematical and Nautical Tables for the Working of the Problems, by HENRY LAW, C.E., and Professor J. R. YOUNG. Illustrated. i2mo, 75. strongly half-bound. Drawing for Marine Engineers. LOCKIKS MARINE ENGINEER'S DRAWING -BOOK. Adapted to the Requirements of the Board ot Trade Examinations. By JOHN LOCKIE, C.E. With 22 Plates, Drawn to Scale. Royal Svo, 35. 6d. cloth. " The student who learns from these drawings will have nothing to unlearn." Engineer. " The examples chosen are essentially practical, and are such as should prove of service to engineers generally, while admirably fulfilling their specific purpose." Mechanical World. Sailmaking. THE ART AND SCIENCE OF SAILMAKING. By SAMUEL B. SADLER, Practical Sailmaker, late in the employment of Messrs. Ratsey and Lapthorne, of Cowes and Gosport. With Plates and other Illustrations. Small 4to, 125. 6d. cloth. SUMMARY OF CONTENTS. CHAP. I. THE MATERIALS USED AND THEIR RELATION TO SAILS. II. ON THE CENTRE OF EFFORT. III. ON MEASURING. IV. ON DRAWING. V. ON THE NUMBER OF CLOTHS REQUIRED. VI. ON ALLOWANCES. VII. CALCU- LATION OF GORES. VIII. ON CUTTING OUT. IX. ON ROPING. X. ON DIA- GONAL-CUT SAILS. XI. CONCLUDING REMARKS. " This work is very ably written, and is illustrated by diagrams and carefully- worked calcula- tions. The work should be in the hands of every sailmaker, whether employer or employed, as it cannot fail to assist them in the pursuit of their important avocations." Isle of Wight Herald. " This extremely practical work gives a complete education in all the branches of the manu- facture, cutting out, roping, seaming, and goring. It is copiously illustrated, and will form a first- rate text-book and guide." Portsmouth Times. " The author of this work has rendered a distinct service to all interested in the art of sail- making. The subject of which he treats is a congenial one. Mr. Sadler is a practical sailmaker, and has devoted years of careful observation and study to the subject ; and the results of the experience thus gained he has set forth in the volume before us." Steamship. Chain Cables. CHAIN CABLES AND CHAINS. Comprising Sizes and Curves of Links, Studs, &c., Iron for Cables and Chains, Chain Cable and Chain Making, Forming and Welding Links, Strength of Cables and Chains, Certificates for Cables, Marking Cables, Prices of Chain Cables and Chains, Historical Notes, Acts of Parliament, Statutory Tests, Charges for Testing, List of Manufacturers of Cables, &c. &c. By THOMAS W.TRAILL.F.E.R.N., M. Inst. C.E., Engineer Surveyor in Chief, Board of Trade, Inspector of Chain Cable and Anchor Proving Establishments, and General Suoerin- tendent, Lloyd's Committee on Proving Establishments. With numerous Tables, Illustrations and Lithographic Drawings. Folio, 2 M. cloth, bevelied boards. " It contains a vast amount of valuable Information. Nothing seems to be wanting to m Jce it a compHti and standard work of reference on the subject." Nautical Maerazint. MINING AND METALLURGY. 19 MINING AND METALLURGY. Mining Machinery. MACHINERY FOR METALLIFEROUS MINES : A Practical Treatise for Mining Engineers, Metallurgists, and Managers of Mines. By E. HENRY DAVIES, M.E., F.G.S. Crown 8vo, 580 pp., with upwards of 300 Illustrations, 125. 6d. cloth. [Just published. " Mr. Davies, in this handsome volume, has clone the advanced student and the manager of mines good service. Almost every kind of machinery in actual use is carefully described, and the woodcuts and plates are good.:'Athenczuni. " From cover to cover the work exhibits all the same characteristics which excite the confi- dence and attract the attention of the student as he peruses the hrst page. The work may safely be recommended. By its publication the literature connected with the industry will be enriched, and the reputation of its author enhanced." Mining Journal. "Mr. Davies lias endeavoured to bring before his readers the best of everything in modern mining- appliances. His work carries internal evidence of the author's impartiality, and this con- stitutes oae of the great merits of the book. Throughout his %vork the criticisms are based on his own or other reliable experience.' Iron and Steel Trades' Journal. " The work deals with nearly every class of machinery or apparatus likely to be met with or required in connection with metalliferous mining, and is one which we have every confidence in recommen ding. ' 'Practical Engineer. Metalliferous Minerals and Mining. A TREATISE ON METALLIFEROUS MINERALS AND MINING. By D. C. DAVIES, F.G.S., Mining Engineer, &c., Author of "A Treatise on Slate and Slate Quarrying." Fifth Edition, thoroughly Revised and much Enlarged, by his Son, E. HENRY DAVIES, M.E., F.G.S. With about 150 Illustrations. Crown 8vo, ias. 6d. cloth. "Neither the practical miner nor the general reader interested In mines can have a better book for his companion and his guide." Mining Journal. \_Mining World. "We are doing our readers a service in calling their attention to this valuable work." " A book that will iiot only be useful to the geologist, the practical miner, and the metallurgist but also very interesting to the general public." Iron. "As a history of the present state of mining throughout the world this book has a real value and it supplies an actual want." Athentzum. Earthy Minerals and Mining. A TREATISE ON EARTHY 6- OTHER MINERALS AND MINING. By D. C. DAVIES, F.G.S., Author of " Metalliferous Minerals," &c. Third Edition, revised and Enlarged, by his Son, E. HENRY DAVIES, M.E., F.G.S. With about 100 Illustration?. Crown 8vo, las. 6d. cloth. 1 ' We do not remember to have met with any English work on mining matters that contains the same amount of information packed in equally convenient form." Academy. " We should be inclined to rank it as among the very best of the handy technical and trades manuals which have recently appeared." Britis h Quarterly Review. Metalliferous Mining in the United Kingdom. BRITISH MINING : A Treatise on the History .Discovery, Practical Development, and Future Prospects of Metalliferous Mines in the United King' dom. By ROBERT HUNT, F.R.S., Editor of " Ure's Dictionary of Arts, Manufactures, and Mines," &c. Upwards of 950 pp., with 230 Illustrations. Second Edition, Revised, Super-royal 8vo, 2 2S. cloth. " One of the roost valuable works of reference of modern times. Mr. Hunt, as Keeper of Mining Records of the United Kingdom, has had opportunities for such a task not enjoyed by anyone else and has evidently made the most of them. . . . The language and style adopted are good, and the treatment of the various subjects laborious, conscientious, and scientific." Engineering. "The book is, in fact, a treasure-house of statistical information on minine subjects, and wa know of no other work embodying so great a mass ef matter of this kind. Were this the only merit of Mr. Hunt s volume, it would be sufficient to render it indispensable in the library of everyone interested in the development of the mining and metallurgical industries of this country. Athenaum. " A mass of Information not elsewhere available, and of the greatest value to those who may be Interested in our great mineral industries." Engineer. Underground Pumping Machinery. MINE DRAINAGE. Being a Complete and Practical Treatise on Direct-Acting Underground Steam Pumping Machinery, with a Descrip- tion of a large number of the best known Engines, their General Utility and the Special Sphere of their Action, the Mode of their Application, and their merits compared with other forms of Pumping Machinery. By STEPHEN MICHELL. 8vo, 155. cloth. "Will be highly esteemed by colliery owners and lessees, mining engineers, and students generally who require to be acquainted with the best means of securing the drainage of mines. It is a most valuable work, and stands almost alone In the literature of steam pumping machinery. ' Colliery Guardian. " Much valuable Information Is given, so that the book Is thoroughly worthy of an extensive circulation amongst practical men and purchasers of machinery." Mining journal. 20 CROSBY LOCK WOOD & SON'S CATALOGUE. Prospecting for Gold and other Metals. THE PROSPECTOR'S HANDBOOK: A Guide for the Pro- spector and Traveller in Search of Metal-Bearing or other Valuable Minerals. By J. W. ANDERSON, M.A. (Camb.), F.R.G.S., Author of "Fiji and New Caledonia." Sixth Edition, thoroughly Revised and much Enlarged. Small crown 8vo, 3$. 6d. cloth ; or, 45. 6d. leather, pocket-book form, with tuck. [Just published. "Will supply a much felt want, especially among 1 Colonists, In whose way are so orten thrown, many mineralogical specimens the value of which it is difficult to determine." Engineer. "How to find commercial minerals, and how to identify them when they are found, are the leading points to which attention is directed. The author has managed to pack as much practical detail into his pages as would supply material for a book three times its size." Mining Journal. Mining Notes and Formulae. NOTES AND FORMULAE FOR MINING STUDENTS. By JOHN HERMAN MERIVALE, M.A., Certificated Colliery Manager, Professor of Mining in the Durham College of Science, Newcastle-upon-Tyne. Third Edition, Revised and Enlarged. Small crown 8vo, zs. 6d. cloth. " Invaluable to anyone who is working up for an examination on mining subjects." Iron and Coal Trades Review. " The author has done his work In an exceedingly creditable manner, and has produced a book that will be of service to students, and those who are practicaWy engaged in mining operations." Engineer Handy book for Miners. THE MINER'S HANDBOOK : A Handy Book of Reference on the Subjects of Mineral Deposits, Mining Operations, Ore Dressing, &c. For the Use of Students and others interested in Mining matters. Compiled by JOHN MILNE, F.R.S., Professor of Mining in the Imperial University of Japan. Revised Edition. Fcap. 8vo, 75. 6d. leather. [Just published* " Professor Milne's handbook is sure to be received with favour by all connected with mining, and will be extremely popular among students." Athenaum. Miners 9 and Metallurgists' Focket-BooJc. A POCKET-BOOK FOR MINERS AND METALLURGISTS. Comprising Rules, Formulae, Tables, and Notes, for Use in Field and Office Work. By F. DANVERS POWER, F.G.S., M.E. Fcap. 8vo, gs. leather. " This excellent book is an adm'rable example of its kind, and ought to find a large sale amongst English-speaking prospectors and mining engineers." Engineering. " A useful -vade-mecum containing- a mass of rules, formulas, tables, and various other informa tion, necessary for daily reference." Iron. Mineral Surveying and Valuing. THE MINERAL SURVEYOR AND VALUER'S COMPLETE GUIDE, comprising a Treatise on Improved Mining Surveying and the Valua- tion of Mining Properties, with New Traverse Tables. By WM. LINTERN. Third Edition, Enlarged, izmo, 45. cloth. " A valuable and thoroughly trustworthy guide." Iron and Coal Trades Review, Asbestos and its Uses. ASBESTOS: Its Properties, Occurrence, and Uses. With some Account of the Mines of Italy and Canada. By ROBERT H. JONES. With Eight Collotype Plates and other Illustrations. Crown 8vo, izs. 6d. cloth. "An interesting and invaluable work." CW/terv Guardian. Explosives. A HANDBOOK ON MODERN EXPLOSIVES. Being a Practical Treatise on the Manufacture and Application of Dynamite, Gun- Cotton, Nitro-Glycerine, and other Explosive Compounds. Including the Manufacture of Collodion-Cotton. By M. EISSLER, Author of " The Metal- lurgy of Gold," &c. Crown 8vo, los. 6d. cloth. " Useful not only to the miner, but also to officers of both services to whom blasting and the use of explosives generally may at any time become a necessary auxiliary." Nature. " A veritable mine of information on the subject of explosives employed for military, mining and blasting purposes." Army and Navy Gazette. Iron, Metallurgy of. METALLURGY OF IRON. Containing History of Iron Manu- facture, Methods of Assay, and Analyses of Iron Ores, Processes of Manu- facture of Iron and Steel. &c. By H. BAUERMAN, F.G.S., A.R.S.M. With numerous Illustrations. Sixth Edition, Enlarged, izmo, 55. 6d. cloth. MINING AND METALLURGY. 21 Colliery Management. THE COLLIERY MANAGER'S HANDBOOK: A Compre- hensive Treatise on the Laying-out and Working of Collieries, Designed as a Book of Reference for Colliery Managers, and for the Use of Coal-Mining Students preparing for First-class Certificates. By CALEB PAMELY, Mining Engineer and Surveyor ; Member of the North of England Institute of illustrations, second nauion, Kevisea, \ 700 pages. Price i 55. strongly bound. SUMMARY OF CONTENTS. GEOLOGY. SEARCH FOR COAL. MINERAL LEASES AND OTHER HOLD- INGS. SHAFT SINKING. FITTING UP THE SHAFT AND SURFACE ARRANGE- MENTS. STEAM BOILERS AND THEIR TITTINGS. TIMBERING AND WALLING. NARROW WORK AND METHODS OF WORKING. UNDERGROUND CONVEY- ANCE. DRAINAGE. THE GASES MET WITH IN MINES ; VENTILATION. ON THE FRICTION OF AIR IN MINES. THE PRIESTMAN OIL ENGINE ; PETRO- LEUM AND NATURAL GAS SURVEYING AND PLANNING. SAFETY LAMPS AND FIRE-DAMP DETECTORS. SUNDRY AND INCIDENTAL OPERATIONS AND APPLI- ANCES. COLLIERYEXPLOSIONS. MIS- CELLANEOUS QUESTIONS & ANSWERS. Appendix: SUMMARY OF REPORT OF H.M. COMMISSIONERS ON ACCIDENTS IN MINES. *** OPINIONS OF THE PRESS. " Mr. Pamely has not only given us a comprehensive reference book of a very high order, suitable to the requirements of mining engineers and colliery managers, but at the same time has provided mining students with a class-book that is as interesting as it is instructive." Colliery Manager. " Mr. Pamely 's work is eminently suited to the purpose for which it is intended being clear, interesting, exhaustive, rich in detail, and up to date, giving descriptions of the very latest machines in every department. ... A mining engineer could scarcely go wrong who followed this work." Colliery Guardian. " This is the most complete ' all round ' work on coal-mining published in the English language. . . . No library of coal-mining books is complete without it." Colliery Engineer (Scranton, Pa., U.S.A.). " Mr. Pamely 's work is in all respects worthy of our admiration. No person in any responsible position connected with mines should be without a copy." Westminster Review. Coal and Iron. THE COAL AND IRON INDUSTRIES OF THE UNITED KINGDOM. Comprising a Description of the Coal Fields, and of the Principal Seams of Coal, with Returns of their Produce and its Distribu- tion, and Analyses of Special Varieties. Also an Account of the occurrence of Iron Ores in Veins or Seams ; Analyses of each Variety ; and a History ot the Rise and Progress of Pig Iron Manufacture. By RICHARD MEADE, Assistant Keeper of Mining Records. With Maps. 8vo, i 8s. cloth. " The book is one which must find a place on the shelves of all Interested In coal and Iron production, and in the iron, steel, and other metallurgical industries." Engineer. " Of this book we may unreservedly say that it is the best of its class which we have ever met. ... A book of reference which no one engaged in the Iron or coal trades should omit from his library. Iron and Coal Trades Review. Coal Mining. COAL AND COAL MINING: A Rudimentary Treatise on. By the late Sir WARINGTON W. SMYTH, M.A., F.R.S., &c., Chief Inspector of the Mines of the Crown. Seventh Edition, Revised and Enlarged. With numerous Illustrations. i2mo, 4$. cloth boards. "As an outline is given of every known coal-field In this and other countries, as well as of the principal methods of working, the book will doubtless interest a very large number of readers." Subterraneous Surveying. SUBTERRANEOUS SURVEYING, Elementary and Practical Treatise on, with and without the Magnetic Needle. By THOMAS FEN WICK, Surveyor of Mines, and THOMAS BAKER, C,E. Illust. izmo, 35. cloth boards. Granite Quarrying. GRANITES AND OUR GRANITE INDUSTRIES. By GEORGE F. HARRIS, F.G.S., Membre de la Societe Beige de Geologic, Lec- turer on Economic Geology at the Birkbeck Institution, &c. With Illustra- tions. Crown 8vo, zs. 6d. cloth. " A clearly and well-written manual on the granite Industry." - Scotsman. " An interesting work, which will be deservedly esteemed." Colliery Guardian. " An exceedingly interesting and valuable monograph on a subject which has hitherto received unaccountably little attention in the shape of systematic literary treatment." Scottish Leader. 22 CROSBY LOCKWOOD &- SON'S CATALOGUE. Gold, Metallurgy of. THE METALLURGY OF GOLD : A Practical Treatise on the Metallurgical Treatment of Gold-bearing Ores. Including the Processes of Concentration and Chlorination, and the Assaying, Melting, and Refining oi Gold. By M. EISSLER, Mining Engineer and Metallurgical Chemist, formerly Assistant Assayer of the U. S. Mint, San Francisco. Third Edition, Revised and greatly Enlarged. With 187 Illustrations. Crown 8vo, izs. 6d. cloth. " This book thoroughly deserves its title of a ' Practical Treatise." The -whole process of gold milling, from the breaking of the quartz to the assay of the bullion, is described in clear and orderly narrative and with much, but not too much, fulness of detail." Saturday Review. " The work is a storehouse of information and valuable data, and we strongly recommend it to all professional men engaged in the gold-mining industry." Mining jfournal. Gold Extraction* THE CYANIDE PROCESS OF GOLD EXTRACTION : and its Practical Application on the Witwatersrand Gold Fields in South Africa. By M. EISSLER, M.E., Mem. Inst. Mining and Metallurgy, Author of "The Metallurgy of Gold," &c. With Diagrams and Working Drawings. Large crown 8vo, 75. 6d. cloth. [Just published. " This book is just what was needed to acquaint mining men with the actual working of a pro- cess which is not only the most popular, but is, as a general rule, the most successful for the extrac- tion of gold from tailings." Mining Journal. " The work will prove invaluable to all interested in gold mining, whether metallurgists or as investors." Chemical News. Silver, Metallurgy of. THE METALLURGY OF SILVER : A Practical Treatise on the Amalgamation, Roasting, and Lixiviation of Silver Ores. Including the Assaying, Melting and Refining, of Silver Bullion. By M. EISSLER, Author of "The Metallurgy of Gold," &c. Second Edition, Enlarged. With 150 Illustrations. Crown 8vo, T.OS. 6d. cloth. "A practical treatise, and a technical work which we are convinced will supply a long-felt want amongst practical men, and at the same time be of value to students and others indirectly connected with the industries." Mining Journal. " From first to last the book is thoroughly sound and reliable." Colliery Guardian, " For chemists, practical miners, assayers, and investors alike, we do not know of any work on the subject so handy and yet so comprehensive." Glasgow Herald. Lead, Metallurgy of. THE METALLURGY OF ARGENTIFEROUS LEAD: A Practical Treatise on the Smelting of Silver-Lead Ores and the Refining of Lead Bullion. Including Reports on various Smelting Establishments and Descriptions of Modern Smelting Furnaces and Plants in Europe and America. By M. EISSLER, M.E., Author of "The Metallurgy of Gold," &c, Crown 8vo, 400 pp., with 183 Illustrations, 12$. 6d. cloth. " The numerous metallurgical processes, which are fully and extensively treated of, embrace all the stages experienced in the passage of the lead from the various natural states to its issue from the refinery as an article of commerce." Practical Engineer. " The present volume fully maintains the reputation of the author. Those who wish to obtain a thorough insight into the present state of this industry cannot do better than read this volume, and all mining engineers cannot far! to find many useful hints and suggestions in it." Industries. " It is most carefully written and illustrated with capital drawings and diagrams. In fact, it is the work of an expert for experts, by whom it will be prized as an indispensable text-book." Bristol Mercury. Iron Mining. THE IRON ORES OF GREAT BRITAIN AND IRELAND : Their Mode of Occurrence, Age, and Origin, and the Methods of Searching for and Working them, with a Notice of some of the Iron Ores of Spain. By J. D. KENDALL, F.G.S., Mining Engineer. Crown 8vo, i6s. cloth. " The author has a thorough practica knowledge of his subject, and has supplemented a care- ful study of the available literature by unpublished information derived from his own observations. The result is a very useful volume which cannot fail to be of value to all interested in the iron industry of the country." Industries. " Mr. Kendall is a great authority on this subject and writes from personal observation." Colliery Giiardiato. " Mr. Kendall's book is thoroughly well done. In it there are the outlines of the history of ore mining in every centre and there is everything that we want to know as to. the character of the ores of each district, their commercial value and the cost of working them. ' Iron and Stcei Journal. ELECTRICITY, ELECTRICAL ENGINEERING, etc. 23 ELECTRICITY, ELECTRICAL ENGINEERING, etc. Electrical Engineering. THE ELECTRICAL ENGINEER'S POCKET-BOOK OF MODERN RULES, FORMULA, TABLES, AND DATA. By H. R. KEMPE, M.Inst.E.E., A.M.Iust.C.E., Technical Officer, Postal Telegraphs, Author of " A Handbook of Electrical Testing," &c. Second Edition, thoroughly Revised, with Additions. With numerous Illustrations. Royal 32010, oblong, 55. leather. "There is very little in the shape of formulae or data which the electrician is likely to want In a hurry which cannot be found in its pages." Practical Engineer. >'A very useful book of reference for daily use in practical electrical engineering and its various applications to the industries of the present day." Iron. " It is the best book of its kind." Electrical Engineer. "Well arranged and compact. The ' Electrical Engineer's Pocket-Book ' is a good one." "Strongly recommended to those engaged in the various electrical industries. "Electrical Review. Electric Lighting. ELECTRIC LIGHT FITTING: A Handbook for Working Electrical Engineers, embodying Practical Notes on Installation Manage- ment. By JOHN W. URQUHART, Electrician, Author of " Electric Light, 1 ' &c. With numerous Illustrations. Second Edition, Revised, with Additional Chapters. Crown 8vo, 55. cloth. " This volume deals with what may be termed the mechanics of electric lighting, and Is addressed to men who are already engaged in the work or are training for it. The work traverses a great deal of ground, and may be read as a sequel to the same author's useful work on ' Electric Light." " Electrician. " This is an attempt to state In the simplest language the precautions which should be adopted In installing the electric light, and to give information, for the guidance of those who have to run the plant when installed. The book is well worth the perusal of the workmen for whom it is written." Electrical Review. " We have read this book with a good deal of pleasure. We believe that the book will be of use to practical workmen, who will not be alarmed by finding mathematical formulae which they are unable to understand." Electrical Plant. " Eminently practical and useful. . . . Ought to be in the hands of everyone in charge cf an electric light plant.^ Electrical Engineer. " Mr. Urquhart has succeeded in producing a really capital book, which we have no hesitation In reconunanding to the notice of working electricians and electrical engineers." Mechanical World, Electric Light. - ELECTRIC LIGHT : Its Production and Use. Embodying Plain Directions for the Treatment of Dynamo-Electric Machines, Batteries, Accumulators, and Electric Lamps. By J. W. URQUHART, C.E., Author of "Electric Light Fitting," "Electroplating," &c. Fifth Edition, carefully Revised, with Large Additions and 145 Illustrations. Crown 8vo, 73. 6d. cloth. ' The whole ground of electric lighting is more or less covered and explained in a very clear and concise manner." Electrical Review. "Contains a good deal' of very interesting information, especially in the parts where the author gives dimensions and working costs." Electrical Engineer. " A miniature vade-mecum of the salient facts connected with the science of electric light- ing. " Etectricia n . "You cannot for your purpose have a better book than 'Electric Light,' by Urquhart." n ineer. " The book is by far the best that we have yet met with on the subject." Athentzum. Construction of Dynamos. DYNAMO CONSTRUCTION : A Practical Handbook for the Use of Engineer Constructors and Electricians-in-Charge. Embracing Frame- work Building, Field Magnet and Armature Winding and Grouping, Com- pounding, &c. With Examples of leading English, American, and Conti- nental Dynamos and Motors. By J. W. URQUHART, Author of "Electric Light," " Electric Light Fitting," &c. Second Edition, Revised and En- larged. With 114 Illustrations. Crown 8vo, 75. 6d. cloth. \_Just published. " Mr. Urquhart's book is the first one which deals with these matters in such a way that the engineering student can understand them. The book is very readable, and the author leads his readers up to difficult subjects by reasonably simple tests." Engineering Review. " The author deals with his subject in a style so popular as to make his volume a handbook of great practical value to engineer contractors and electricians in charge of lighting installations." Scotsman. " ' Dynamo Construction ' more than sustains the high character of the author's previous publications. It is sure to be widely read by the large and rapidly-increasing number of practical electricians." Glasgow Herald. " A book for which a demand has long existed." Mechan-U al World. _. 24 CROSBY LOCKWOOD & SON'S CATALOGUE. A New Dictionary of Electricity. THE STANDARD ELECTRICAL DICTIONARY. A Popu- lar Dictionary of Words and Terms Used in the Practice of Electrical Engi- neering. Containing upwards of 3,000 Definitions. By T. O'CONNOR SLOANE A.M., Ph.D., Author of "The Arithmetic of Electricity," &c. Crown 8vo, 630 pp., 350 Illustrations, 75, 6d. cloth. [Just published. " The work has many attractive features in it, and is beyond doubt, a well put together and useful publication. The amount of ground covered may be gathered from the fact that in the index about 5,000 references will be found. The inclusion of such comparatively modern words as ' impedence," 'reluctance,' &c., shows that the author has desired to be un to date, and indeed there are other indications SON'S CATALOGUE. DECORATIVE ARTS, etc. Woods and Marbles (Imitation of). SCHOOL OF PAINTING FOR THE IMITATION OF WOODS AND MARBLES, as Taught and Practised by A. R. VAN DER BURG and P. VAN DER BURG, Directors of the Rotterdam Painting Institution. Royal folio, 18$ by i2\ in., Illustrated with 24 full-size Coloured Plates; also 12 plain Plates, comprising rs4 Figures. Second and Cheaper Edition, Price 1 ns.6d. List of Plates. i. Various Tools required for Wood Painting a, 3. Walnut: Preliminary Stages of Graining and Finished Specimen 4. Tools used for Marble Painting and Method of Manipulation S, 6. St. Remi Marble: Earlier Operations and Finished Specimen 7. Methods of Sketching different- Grains, Knots, &c. 8, 9. Ash: Pre- liminary Stages and Finished Specimen 10. Methods of Sketching Marble Grains ir, ia. Breche Marble : Preliminary Stages of Working and Finished Specimen 13. Maple : Methods of Producing the different Grains 14, 15. Bird s- . . Hminary Stages and Finished Specimen 34, 36. Waulsort Marble: Varieties of Grain, I finished and Finished Specimens. of Producing the different Grains 14, 15. Bird's- eye Maple: Preliminary Stages and Finished Specimen 16. Methods of Sketching the dif- Finished Specimen 19. M of various Grains and M Mahogany : Specimens ethods of Manipulation . ai. Mahogany: Earlier Stages and Finished Specimen 22, 23, 24. Sienna Marble : Varieties of Grain, Preliminary Stages and Finished Specimen 25, 26, 27. Juniper Wood : Methods of producing Grain, &c. : Preliminary Stages Vert de :thods Speci- Tools f producing and Finished Specimen 28, 29, 30. Mer Marble : Varieties of Grain and Methods of Working Unfinished and Finished S mens 31. 32. 33. Oak: Varieties of Grain, 33. Oak : nd Meth< Employed, and Methods of Manipulation, Pre- ferent Species of White Marble 17, 18. White Marble: Preliminary Stages of Process and ' Those who desire to attain skill in the art of painting woods and marbles will find advantage In consulting this book. . . . Some of the Working Men's Clubs should give their young men the opportunity to study it." Builder. " A comprehensive guide to the art. The explanations of the processes, the manipulation and management of the colours, and the beautifully executed plates will not be the least valuable to th Mudent who aims at making his work a faithful transcript of nature." Building News. Wall Paper. WALL PAPER DECORATION. By ARTHUR SEYMOUR JENNINGS, Author of " Practical Paper Hanging." With numerous Illustra- tions. Demy 8vo. [In preparation, House Decoration. ELEMENTARY DECORATION. A Guide to the Simpler Forms of Everyday Art. Together with PRACTICAL HOUSE DECORA- TION. By TAMES W. FACEY. With numerous Illustrations. In One Vol., 5$. strongly half- bound. Mouse Painting, Graining, etc. HOUSE PAINTING, GRAINING, MARBLING, AND SIGN WRITING, A Practical Manual of. By ELLIS A.DAVIDSON. Sixth Editior. With Coloured Plates and Wood Engravings. i2mo, 6s. cloth boards. " A mass of information, of use to the amateur and of value to the practical man." English Mechanic. Decorators, Heceipts for. THE DECORATOR'S ASSISTANT: A Modern Guide to De- corative Artists and Amateurs, Painters, Writers, Gilders, &c. Containing upwards of 600 Receipts, Rules and Instructions ; with a variety of Informa- tion for General Work connected with every Class of Interior and Exterior Decorations, &c. Sixth Edition. 152 pp., crown 8vo, is. in wrapper. " Full of receipts of value to decorators, painters, gilders, &c. The book contains the gist of larger treatises on colour and technical processes. It would be difficult to meet with a work so full of varied information on the painter's art "Building News. Moyr Smith on Interior Decoration. ORNAMENTAL INTERIORS, ANCIENT AND MODERN. By J. MOYR SMITH. Super-royal 8vo, with 32 full-page Plates and numerous smaller Illustrations, handsomely bound in cloth, gilt top, price i8s. " The book is well illustrated and handsomely got up, and contains some true criticism and good many good examples of decorative treatment. The Builder. DECORATIVE ARTS, etc. 31 British and Foreign Marbles. MARBLE DECORATION and the Terminology of British and Foreign Marbles. A Handbook for Students. By GEORGE H. BLAGROVE, Author of " Shoring and its Application," &c. With 28 Illustrations. Grown 6vo, 35. 6d. cloth. " This most useful and much wanted handbook should be in the hands of every architect and builder." Building- World. " A carefully and usefully written treatise ; the work is essentially practical." Scotsman Marble Working, etc. MARBLE AND MARBLE WORKERS: A Handbook for Architects, Artists, Masons, and Students. By ARTHUR LEE, Author of " A Visit to Carrara," " The Working of Marble, 1 ' &c. Small crown 8vo, 2s. clotb. " A really valuable addition to the technical literature of architects and masons." Building Nevis, DELAMOTTE'S WORKS ON ILLUMINATION AND ALPHABETS. A PRIMER OF THE ART OF ILLUMINATION, for the Use of Begi'iners : with a Rudimentary Treatise on the Art, Practical Directions for its Exercise, and Examples taken from Illuminated MSS., printed in Gold and Colours. By F. DELAMOTTE, New and Cheaper Edition. Small 4to, 65. orna- mental boards. "The examples of anctent MSS. recommended to the student, which, with much good sense, the author chooses from collections accessible to all, are selected with judgment and knowledge as well as taste." Athentzum, ORNAMENTAL ALPHABETS, Ancient ant Medieval, from th* Eighth Century, voiih Numerals; including Gothic, Church-Text, large and small, German, Italian, Arabesque, Initials for Illumination, Monograms, Crosses, &c. &c., for the use of Architectural and Engineering Draughtsmen, Missal Painters, Masons, Decorative Painters, Lithographers, Engravers, Carvers, &c. &c. Collected and Engraved by F. DELAMOTTE, and printed ia Colours. New and Cheaper Edition, Royal 8vo, oblong, zs. 6d, ornamental boards. " For those who insert enamelled sentences round gilded chalices, who blazon shop legends ovei shop-doors, who letter church walls with pithy sentences from the Decalogue, this book will be use- tul." Atftetuzum. EXAMPLES OF MODERN ALPHABETS, Plain and Ornamental; including German, Old English, Saxon, Italic, Perspective, Greek, Hebrew, Court Hand, Engrossing, Tuscan, Riband, Gothic, Rustic, and Arabesque ; with several Original Designs, and an Analysis of the Roman and Old English Alphabets, large and small, and Numerals, for the use of Draughtsmen, Sur- veyors, Masons, Decorative Painters, Lithographers, Engravers, Carvers, &c. Collected and Engraved by F. DELAMOTTE, and printed in Colours. New and Cheaper Edition. Royal 8vo, oblong, as. 6d. ornamental boards. " There Is comprised In It every possible shape into which the letters of the alphabet and numerals can be formed, and the talent which has been expended In the conception of the varioui plain and ornamental letters is wonderful." Standard. MEDIEVAL ALPHABETS AND INITIALS FOR ILLUMI- NA TORS. By F. G. DELAMOTTE. Containing 21 Plates and Illuminated Title, printed in Gold and Colours. With an Introduction by J. WILLIS BROOKS. Fourth and Cheaper Edition. Small 4to, 45. ornamental boards. " A volume In which the letters of the alphabet come forth glorified in gilding andall the colours of the prism interwoven and intertwined and intermingled." Sun. THE EMBROIDERER'S BOOK OF DESIGN. Containing Initials, Emblems, Cyphers, Monograms, Ornamental Borders, Ecclesiastical Devices, Mediaeval and Modern Alphabets, and National Emblems. Col- lected by F. DELAMOTTE, and printed in Colours. Oblong royal 8vo, is. Gd. ornamental wrapper. " The book will be of great assistance to ladles and young children who are endowed with the art of plying the needle in this most ornamental and useful pretty work." East Anglian Times. Wood Carving. INSTRUCTIONS IN WOOD-CARVING, for Amateurs; with Hints on Design. By A LADY. With Ten Plates. New and Cheaper Edition. Crown 8vo, zs. in emblematic wrapper. " The handicraft of the wood-carver, so well as a book can mpart It. may be learnt from ' A Lady's' publication." Ath -nceum 32 CROSBY LOCK WOOD <& SON'S CATALOGUE. NATURAL SCIENCE, etc. The Heavens and their Origin. THE VISIBLE UNIVERSE: Chapters on the Origin and Construction of the Heavens. By J. E. GORE, F.R.A.S. Illustrated by 6 Stellar Photographs and 12 Plates. 8vo, i6s. cloth. " A valuable and lucid summary of recent astronomical theory, rendered more valuable and 1 attractive by a series of stellar photographs and other illustrations." The Times. " In presenting a clear and concise account of the present state of our knowledge, Mr. Gore has made a valuable addition to the literature of the subject." Nature. " As interesting as a novel, and instructive withal ; the text being made still more luminous by " Stellar photographs and other illustrations. . . . A most valuable book." Manchester Exa of the finest works on astronomical science that has recently appeared in our language. Leeds Mercury. One of the finest works on astronomical science that has recently appeared in our lan The Constellations. STAR GROUPS: A Student's Guide to the Constellations. By J. ELLARD GORE, F.R.A.S., M.R.I. A., &c., Author of" The Visible Universe,' " The Scenery of the Heavens." With 30 Maps. Small 4to, 55. cloth, silvered. "A knowledge of the principal constellations visible in our latitudes may be easily acquired from the thirty maps and accompanying text contained in this work." Nature. " The volume contains thirty maps showing stars of the sixth magnitude the usual naked-eye limit and each is accompanied by a brief commentary, adapted to facilitate recognition and bring to notice objects of special interest. For the purpose of a preliminary survey of the ' midnight pomp ' of the heavens, nothing could be better than a set of delineations averaging scarcely twenty square inches in area, and including nothing that cannot at once be identified." Saturday Re-view. " A very compact and handy guide to the constellations." Athenaeum. Astronomical Terms. AN ASTRONOMICAL GLOSSARY; or, Dictionary of Terms used in Astronomy. With Tables of Data and Lists of Remarkable and Interesting Celestial Objects. By J. ELLARD GORE, F.R.A.S., Author of " The Visible Universe," &c. Small crown 8vo, 2s. 6d. cloth. " A very useful little work for beginners in astronomy, and not to be despised by more ad- vanced students." The Times. " Astronomers of all kinds will be glad to have it for reference." Guardian. The Microscope. THE MICROSCOPE : Its Construction and Management, in- cluding Technique, Photo-micrography, and the Past and Future of the Microscope. By Dr. HENRI VAN HEURCK. Re-Edited and Augmented frorn the Fourth French Edition, and Translated by WYNNE E. BAXTER, F.G.S. 400 pages, with upwards of 250 Woodcuts. Imp. 8vo, i8s. cloth. " A translation of a well-known work, at once popular and comprehensive." Times. " The translation is as felicitious as it is accurate." Nature. The Microscope. PHOTO-MICROGRAPHY. By Dr. H. VAN HEURCK. Extracted from the above Work. Royal 8vo, with Illustrations, is. sewed. Astronomy. ASTRONOMY. By the late Rev. ROBERT MAIN, F.R.S. Third Edition, Revised, by WM. T. LYNN, B.A., F.R.A.S., i2mo, as. cloth. " A sound and simple treatise, and a capital book for beginners." Knowledge. Recent and Fossil Shells. A MANUAL OF THE MOLLUSC A : Being a Treatise on Recent and Fossil Shells. By S. P. WOODWARD, A.L.S., F.G.S. With an Appendix on Recent and Fossil Conchological Discoveries, by RALPH TATE, A.L.S., F.G.S. With 23 Plates and upwards of 300 Woodcuts. Reprint of Fourth Edition, 1880. Crown 8vo, 7$. 6d. cloth. 11 A most valuable storehouse of conchological and geological Information." Science Gossip. Geology and Genesis. THE TWIN RECORDS OF CREATION; or, Geology and Genesis : their Perfect Harmony and Wonderful Concord. By GEORGE W. VICTOR LE VAUX. Fcap. 8vo, 55. cloth. " A valuable contribution to the evidences of Revelation, and disposes very conclusively of the arguments of those who would set God's Works against God s Word. No real difficulty is shirked and no sophistry is left unexposed." The Rock. Geology. RUDIMENTARY TREATISE ON GEOLOGY, PHYSICAL AND HISTORICAL. With especial reference to the British series of Rocks. By R. TATE, F.G.S. With 250 Illustrations, izmo, 5$. cloth boards. NATURAL SCIENCE, etc. 33 DR. LARDNER'S COURSE OF NATURAL PHILOSOPHY. HANDBOOK OF MECHANICS. Re- written and Enlarged by B. LOEWY, F.R.A.S. Post 8vo, 6s. cloth. "Mr. Loewy has carefully revised the book, and brought It up to modern requirements. Nature. HANDBOOK OF HYDROSTATICS & PNEUMATICS. Enlarged by R. LOEWY, F.R.A.S. Post 8vo, 55. cloth. " For those ' who desire to attain an accurate knowledge of physical science without the pro- found methods of mathematical investigation, 1 this work is well adapted." Chemical News. HANDBOOK OF HEAT. Edited and almost entirely Re- written by BENJAMIN LOEWY, F.R.A.S., &c. Post 8vo, 6s. cloth. " The style is always clear and precise, and conveys Instruction without leaving any cloudiness or lurking doubts behind." Engineering. HANDBOOK OF OPTICS. By Dr. LARDNER. Edited by T. O. HARDING, B.A. Post 8vo, 55. cloth. "Written by an able scientific writer and beautifully illustrated." Mechanics Magazine. HANDBOOK OF ELECTRICITY AND MAGNETISM. By Dr. LARDNER. Edited by G. C. FOSTER, B.A. Post 8vo, 55. cloth. " The book could not have been entrusted to anyone better calculated to preserve the terse and lucid style of Lardner." Popular Science Review. HANDBOOK OF ASTRONOMY. By Dr. LARDNER. Fourth Edition by E. DUNKIN, F.R.A.S. Post 8vo, gs. 6d. cloth. " Probably no other book contains the same amount of information In so compendious and well- arranged a form certainly none at the price at which this is offered to the public." Athenceum. "We can do no other than pronounce this work a most valuable manual of astronomy, and we strongly recommend it to all who wish to acquire a general but at the same time correct acquaint- ance with this sublime science." Quarterly "Journal of Science. OR. LARDNER'S MUSEUM OF SCIENCE AND ART. THE MUSEUM OF SCIENCE AND ART. Edited by Dr. LARDNER. With upwards of 1,200 Engravings on Wood. In 6 Double Volumes, i is. in a new and elegant cloth binding ; or handsomely bound in half-morocco, 315. 6d. " A cheap and interesting publication, alike Informing and attractive. The papers combine subjects of importance and great scientific knowledge, considerable Inductive powers, and a popular style of treatment." Spectator. " The ' Museum of Science and Art ' is the most valuable contribution that has ever beea made to the Scientific Instruction of every class of society." Sir DAVID BREWSTER, In the North British Review. *** Separate books formed front the above, fully Illustrated, suitable for Workmen's Libranes t Science Classes, etc. Steam and its Uses. 2s. cloth. Popular Astronomy. 45. 6d.cloth. The Bee and White Ants. zs. cloth. The Electric Telegraph, is. 6d. Common Things Explained. 55. The Microscope, zs. cloth. Popular Geology. 2s. 6d. cloth. Popular Physics, zs. 6d. cloth. Dr. Lardner's School Handbooks. NATURAL PHILOSOPHY FOR SCHOOLS. Fcap. 8vo, 35. 6d. " A very convenient class-book for junior students In private schools." British Quarterly Revietv. ANIMAL PHYSIOLOGY FOR SCHOOLS. Fcap. 8vo, 35. 6d. " Clearly written, well arranged, and excellently illustrated." Gardener's ChronicU. THE ELECTRIC TELEGRAPH. By Dr. LARDNER. Re- vised by E. B. BRIGHT, F.R.A.S. Fcap. 8vo, 2s. 6d. cloth " One of the most readable books extant on the Electric Telegraph." English Mechanic. D 34 CROSBY LOCKWOQD & SON'S CATALOGUE. CHEMICAL MANUFACTURES, CHEMISTRY. Chemistry for Engineers, etc. ENGINEERING CHEMISTRY: A Practical Treatise for the Use of Analytical Chemists, Engineers, Iron Masters, Iron Founders, Students, and others. Comprising Methods of Analysis and Valuation of the Principal Materials used in Engineering Work, with numerous Analyses, Examples, and Suggestions. By H. JOSHUA PHILLIPS, F.I.C., F.C.S. formerly Analytical and Consulting Chemist to the Great Eastern Railway. Second Edition, Revised and Enlarged. Crown 8vo, 400 pp., with Illustra- tions, IDS. 6d. cloth. [Just published. " In this work the author has rendered no small service to a numerous body of practical men. . . . The analytical methods may be pronounced most satisfactory, being as accurate as the despatch required of engineering chemists permits." Chemical News. " Those in search of a handy treatise on the subject of analytical chemistry as applied to the every-day requirements of workshop practice will find this volume of great assistance." Iron. " The first attempt to bring forward a Chemistry specially written for the use of engineers, and we have no hesitation whatever in saymg that it should at once be in the possession of every railway engineer." The Rail-way Engineer. " The book will be very useful to those who require a handy and concise resume of approved methods of analysing and valuing metals, oils, fuels, &c. It is, in fact, a work for chemists, a guide to the routine of the engineering laboratory. . . . The book is full of good things. As a hand- book of technical analysis, it is very welcome." Builder. " Considering the extensive ground which such a subject as Engineering Chemistry covers, the work is complete, and recommends itself to both the practising analyst and the analytical student." Chemical Trade jfottrnal. " The analytical methods given are, as a whole, such as are likely to give rapid and trust- worthy results in experienced hands. There is much excellent descriptive matter in the work, the chapter on ' Oils and Lubrication ' being specially noticeable in this respect." Engineer. Alkali Trade, Manufacture of Sulphuric Acid, etc. A MANUAL OF THE ALKALI TRADE, including the Manufacture of Sulphuric Acid, Sulphate of $oda, and Bleaching Powder. By JOHN LOMAS, Alkali Manufacturer, Newcastle-upon-Tyne and London. With 232 Illustrations and Working Drawings, and containing 390 pages of Text. Second Edition, with Additions. Super-royal 8vo, i IDS. cloth. This book Is written by a manufacturer for manufacturers. The working details of the most approved forms of apparatus are given, and these are accompanied by no less than 932 wood en- gravings, all of which may be used for the purposes of construction. Every step in the manu- facture is very fully described In this manual, and each improvement explained." AthenTitm. " We find not merely a sound and luminous explanation of the chemical principles of the trade, but a notice of numerous matters which have a most important bearing on the successful conduct of alkali works, but which are generally overlooked by even experienced technological authors." Chemical Review. The Blowpipe. THE BLOWPIPE IN CHEMISTRY, MINERALOGY, AND GEOLOGY. Containing all known Methods of Anhydrous Analysis, many Working Examples, and Instructions for Making Apparatus. By Lieut. - Colonel W. A. Ross, R.A., F.G.S. With 120 Illustrations. Second Edition, Revised and Enlarged. Crown 8vo, 55. cloth. "The student who goes through the course of experimentation here laid down will gain a better insight into inorganic chemistry and mineralogy than if he had 'got up 1 any of the best text-books, and passed any number of examinations in their contents." Chemical News. Commercial Chemical Analysis. THE COMMERCIAL HANDBOOK OF CHEMICAL ANA- LYSIS; or, Practical Instructions for the determination of the Intrinsic or Commercial Value of Substances used in Manufactures, in Trades, and in the Arts. By A. NORMANDY, Editor of Rose's "Treatise on Chemical Analysis." New Edition, to a great extent Re-written by HENRY M. NOAD, Ph.D., F.R.S. With numerous Illustrations. Crown 8vo, MS. 6d. cloth. " We strongly recommend this book to our readers as a guide, alike indispensable to the housewife as to the pharmaceutical practitioner." Medical Times. " Essential to the analysts appointed under the new A< t. The most recent results are given and the work is well edited and carefully written." Nature. Dye- Wares and Colours. THE MANUAL OF COLOURS AND DYE-WARES: Their Properties, Applications, Valuations, Impurities, and Sophistications. For the use of Dyers, Printers, Drysalters, Brokers, &c. By J. W. SLATER. Second Edition, Revised and greatly Enlarged. Crown 8vo, 75. 6d. cloth. "A cemplete encyclopaedia of the materia ttnctoria. The Information given respecting each article is full and precise, and the methods of determining the value of articles such as these, so liable te sophistication are pven with clearness, and are practical as well as valuable. 1 Chemist "There W no other work which covers precisely the same ground. To students preparing for examinations in dyeing and printitag It will prove exceedingly useful. "-Chemical Newt. CHEMICAL MANUFACTURES, CHEMISTRY, etc. 35 Modern Breiving and Malting. A HANDYBOOK FOR BREWERS: Being a Practical Guide to the Art of Brewing and Malting. Embracing the Conclusions of Modern Research which bear upon the Practice of Brewing. By HERBERT EDWARDS WRIGHT, M.A. Crown 8vo, 530 pp., 125. 6d. cloth. " May be consulted with advantage by the student who is preparing himself for examinational tests, while the scientific brewer will find in it a resume of all the most important discoveries of modem times. The work is written throughout in a clear and concise manner, and the author takes great care to discriminate between vague theories and well-established facts." Brewers' Journal. " We have great pleasure in recommending this handybook, and have no hesitation In saying that it is one of the best if not the best which has yet been written on the subject of beer-brewing in this country, and it should have a place on the shelves of every brewer's library." The Brewer's Guardian. " Although the requirements of the student are primarily considered, an acquaintance of half- an-hour's duration cannot fail to impress the practical brewer with the sense of having found a trustworthy guide and practical counsellor in brewery matters." Chemical Trade Journal. Analysis and Valuation of Fuels. FUELS: SOLID, LIQUID, AND GASEOUS, Their Analysis and Valuation. For the Use of Chemists and Engineers. By H. J. PHILLIPS, F.C.S., formerly Analytical and Consulting Chemist to the Great Eastern Railway. Second Edition, Revised and Enlarged. Crown 8vo, 55. cloth. " Ought to have its place in the laboratory of every metallurgical establishment, and wherever fuel is used on a large scale." Chemical News. " Cannot fail to be of wide interest, especially at the present time." Railway News. figments. THE ARTIST'S MANUAL OF PIGMENTS. Showing their Composition, Conditions of Permanency, N on- Permanency, and Adul- terations ; Effects in Combination with Each Other and with Vehicles ; and the most Reliable Tests of Purity Together with the Science and Art Department's Examination Questions on Painting. By H. C. STANDAGE. Second Edition. Crown 8vo, as. 6d. cloth. " This work is indeed tnultum-in-parvo, and we can, with good conscience, recommend it to all who come in contact with pigments, whether as makers, dealers or users." Chemical Review. Gauging. Tables ana Rules for Revenue Officers, Brewers, etc. A POCKET BOOK OF MENSURATION AND GAUGING: Containing Tables, Rules and Memoranda for Revenue Officers, Brewers, Spirit Merchants, &c. By J. B. MANT (Inland Revenue). Second Edition, Revised. i8mo, 4$. leather. " This handy and useful book is adapted to the requirements of the Inland Revenue Depart- ment, and will be a favourite book of reference." Civilian. " Should be in the hands of every practical brewer." Brewers' Journal. INDUSTRIAL ARTS, TRADES, AND MANUFACTURES. Cotton Spinning. COTTON MANUFACTURE : A Manual of Practical Instruc- tion in the Processes of Opening, Carding, Combing, Drawing, Doubling and Spinning of Cotton, the Methods of Dyeing, &c. For the Use of Opera- tives, Overlookers and Manufacturers. By JOHN LISTER, Technical In- structor, Pendleton. 8vo, 75. 6d. cloth. [Just published, "This invaluable volume is a distinct advance in the literature of cotton manufacture." Machinery. " It is thoroughly reliable, fulfilling nearly all the requirements desired." Glasgow Herald. Flour Manufacture) Milling, etc. FLOUR MANUFACTURE: A Treatise on Milling Science and Practice. By FRIEDRICH KICK, Imperial Regierungsrath, Professor of Mechanical Technology in the Imperial German Polytechnic Institute, Prague. Translated from the Second Enlarged and Revised Edition with Supplement. By H. H. P. POWLES, A.-M.Inst.C.E. Nearly 400 pp. Illus- trated with 28 Folding Plates, and 167 Woodcuts. Royal 8vo, 255. cloth. 11 This valuable work is, and will remain, the standard authority on the science of milling. . . The miller who has read and digested this work will have laid the foundation, so to speak, of a sue- cesiiul career ; he will have acquired a number of general principles which he can proceed to apply. In this handsome volume we at last have the accepted text-book of modern milling in good, sound EngUsh, which has little, if any, trace of the German idiom." The Miller. " The appearance of this celebrated work in English is very opportune, and British millers wfll, we are sure, not be slow in availing themselves of its pages." Millers' Gazette, 36 CROSBY LOCK WOOD 6- SON'S CATALOGUE. Agglutinants. CEMENTS, PASTES, GLUES AND GUMS: A Practical Guide to the Manufacture and Application of the various Agglutinants re- quired in the Building, Metal- Working, Wood-Working and Leather-Work- ing Trades, and for Workshop, Laboratory or Office Use. With upwards of 900 Recipes and Formulae. By H. C. STANDAGE, Chemist. Crown 8vo, 25. 6d. cloth. [Just published. " We have pleasure iu speaking favourably of this volume. So far as we have had experience, which is not inconsiderable, this manual is trustworthy." Athenceunt. " As a revelation of what are considered trade secrets, this book will arouse an amount of curiosity among the large number of industries it touches." Daily Chronicle. " In this goodly collection of receipts it would be strange if a cement for any purpose cannot be found." Oil and Colourman' s Journal. THE ART OF SOAP-MAKING: A Practical Handbook of the Manufacture of Hard and Soft Soaps, Toilet Soaps, etc. Including many New Processes, and a Chapter on the Recovery of Glycerine from Waste Leys. By ALEXANDER WATT. Fourth Edition, Enlarged. Crown 8vo, 75. 6d. cloth. "The work will prove very useful, not merely to the technological student, but to the practical soap-boiler who wishes to understand the theory of his art." Chemical Nevis. " A thoroughly practical treatise on an art which has almost no literature in our language. We congratulate the author on the success of his endeavour to fill a void in English tec hnlcal litera- ture." Nature. Paper Making. PRACTICAL PAPER-MAKING: A Manual for Paper-makers and Owners and Managers of Paper-Mills. With Tables. Calculations, &c. By G. CLAPPERTON, Paper-maker. With Illustrations of Fibres from Micro- Photographs. Crown 8vo, 53. cloth. [Just published. " The author caters for the requirements of responsible mill hands, apprentices, &c., whilst his manual will be found of great service to students of technology, as well as to veteran paper makers and mill owners. The illustrations form an excellent feature." Paper Trade Review. " We recommend everybody interested in the trade to get a copy of this thoroughly practical book." Paper Making. Paper Making. THE ART OF PAPER MAKING : A Practical Handbook of the Manufacture of Paper from Rags, Esparto, Straw, and other Fibrous Materials. Including the Manufacture of Pulp from Wood Fibre, with a Description of the Machinery and Appliances used. To which are added Details of Processes for Recovering Soda from Waste Liquors. By ALEXANDER WATT, Author of" The Art of Soap-Making" With Illusts. Crown 8vo, 7$. 6d. cloth. ' It may be regarded as the standard work on the subject. The book Is full of valuable In- formation. The 'Art of Paper-making,' is in every respect a model of a text-book, either for a technical class or for the private student." Paper and Printing Trades yournal. Leather Manufacture. THE ART OF LEATHER MANUFACTURE. Being a Practical Handbook, in which the Operations of Tanning, Currying, and Leather Dressing are fully Described, and the Principles of Tanning Ex- plained, and many Recent Processes Introduced ; as also the Methods for the Estimation of Tannin, and a Description of the Arts of Glue Boiling, Gut Dressing, &c. By ALEXANDER WATT, Author of " Soap-Making," &c, Second Edition, Crown 8vo, gs. cloth. "A sound, comprehensive treatise on tanning and Its accessories. It Is an eminently valuable production, which redounds to the credit of both author and publishers." Chemical Review. Boot and Shoe Making. THE ART OF BOOT AND SHOE-MAKING. A Practical Handbook, including Measurement, Last-Fitting, Cutting-Out, Closing, and Making, with a Description of the most approved Machinery employed. By JOHN B. LENO, late Editor of St. Crispin, and The Boot and Shoe-Maker. i2mo, 2$. cloth limp. " This excellent treatise is by far the best work ever written. The chapter on clicking, which shows how waste may be prevented, will save fifty times the price of the book." Dentistry Const ruction. MECHANICAL DENTISTRY : A Practical Treatise on the Construction of the various kinds of Artificial Dentures. Comprising also Use- ful Formulae, Tables, and Receipts for Gold Plate, Clasps, Solders, &c. &c. By CHARLES HUNTER. Third Edition. Crown 8vo, 3$. 6d. cloth. We can strongly recommend Mr. Hunter's treatise to all students preparing for the profession of dentistry as well as to every mechanical denttst." Dublin Journal if Medical Science. INDUSTRIAL AND USEFUL ARTS. 37 Wood Engraving. WOOD ENGRA VING : A Practical and Easy Introduction to the Studv of the Art. By WILLIAM NORMAN BROWN. Second Edition. With numerous Illustrations, ismo, is. 6d. cloth limp. " The book is clear and complete, and will be useful to anyone wanting to understand the first elements of the beautiful art of wood engraving." Grathic. Horology. A TREATISE ON MODERN HOROLOGY, in Theory and Prac- tice. Translated from the French of CLAUDIUS SAUNIER, ex-Director of the School of Horology at Ma9on, by JULIEN TRIPPLIN, F.R.A.S., Besancon Watch Manufacturer, and EDWARD RIGG, M.A., Assayer in the Royal Mint. With 78 Woodcuts and 22 Coloured Copper Plates. Second Edition. Super- royal 8vo, 2 2s. cloth ; 2 IDS. half-calf. " There is no horological -work in the English language at all to be compared to this produc- tion of M. Saunier's for clearness and completeness. It is alike good as a guide for the student and as a reference for the experienced horolegist and skilled workman." Horological Journal. " The latest, the most complete, and the most reliable of those literary productions to which continental watchmakers are indebted for the mechanical superiority over their English brethren to fact, the Book of Books, is M. Saunier's 'Treatise.'"- Watchmaker, "Jeweller and Silversmith. Watchmaking. THE WATCHMAKER'S HANDBOOK. Intended as a Work- shop Companion for those engaged in Watchmaking and the Allied Mechani- cal Arts. Translated from the French of CLAUDIUS SAUNIER, and considera- ably enlarged by JULIEN TRIPPLIN, F.R.A.S., Vice-President of the Horological Institute, and EDWARD RIGG, M. A., Assayer in the Royal Mint. With numerous Woodcuts and 14 Copper Plates. Third Edition. Crown 8vo, 95. cloth. " Each part is truly a treatise In Itself. The arrangement Is pood and the language is clear and concise. It is an admirable guide for the young watchmaker." Engineering. " It is impossible to speak too highly of its excellence. It fulfils every requirement In a hand- book intended for the use ol a workman. Should be found in every workshop." Watch and " This book contains an immense number of practical details bearing on the daily occupation of a watchmaker." Watchmaker and Metal-worker (Chicago). Watches and Timekeepers. A HISTORY OF WATCHES AND OTHER TIMEKEEPERS. By TAMES F. KENDAL, M.B.H.lnst. is. 6d. boards ; or zs. 6d. cloth gilt. "Mr. Kendal's book, for its size, is the best which has yet appeared on this subject in the English language." Industries. " Open the book where you may, there is interesting matter in it concerning the ingenious devices of the ancient or modern horologer. The subject is treated in a liberal and entertaining spirit, as might be expected of a historian who is a master of the craft." Saturday Re-view. Electrolysis of Gold, Silver, Copper, etc. ELECTRO -DEPOSIT ION : A Practical Treatise on the Electrolysis of Gold, Silver^ Copper, Nickel, and other Metals and Alloys. With descrip- tions of Voltaic Batteries, Magneto and Dynamo-Electric Machines, Ther- mopiles, and of the Materials and Processes used in every Department of the Art, and several Chapters on Electro-Metallurgy. By ALEXANDER WATT, Author of "Electro-Metallurgy," &c. Third Edition,Revised. Crown 8vo, gs. cloth. "Eminently a book for the practical worker In electro-deposition. It contains practical descriptions of methods, processes and materials as actually pursued and used in the workshop." Engineer. Electro-Metallurgy. ELECTRO-MET A LL URG Y ; Practically Treated. By ALEXANDER WATT, Author of " Electro-Deposition," &t Tenth Edition, including the most recent Processes. 121110, 45. cloth boards. "From this book both amateur and artisan may learn everything necessary for the succ essful prosecution of electroplating." Iron, Working in Gold. THE JEWELLER'S ASSISTANT IN THE ART OF WORK- ING IN GOLD : A Practical Treatise for Masters and Workmen, Compiled from the Experience of Thirty Years' Workshop Practice. By GEORGE E. GEE, Author of "The Goldsmith's Handbook," &c. Cr. 8vo, 75. 6d. cloth. " This manuaj of technical education is apparently destined to be a valuable auxiliary to a handicraft which is certainly capable of great improvement." The Times. " Very useful in the workshop, as the knowledge is practical, having been acquired by long experience, and all the recipes and directions are guaranteed to be successful." Jeweller and Metal-worker. 38 CROSBY LOCK WOOD & SON'S CATALOGUE. Electroplating. ELECTROPLATING: A Practical Handbook on the Deposi- tion of Copper, Silver, Nickel, Gold, Aluminium, Brass, Platinum, &c. &c. With Descriptions of the Chemicals, Materials, Batteries, and Dynamo Machines used in the Art. By J. W. URQUHART, C.E., Author of " Electric Light," &c. Third Edition, with Additions. Crown 8vo. 55. cloth. " An excellent practical manual." Engineering, " An excellent work, giving the newest information." Horological Journal, JElectrotyping. ELECTROTYPING : The Reproduction and Multiplication of Print- ing Surfaces and Works of Art by the Electro-deposition of Metals. By J. W. URQUHART, C.E. Crown 8vo, 55. cloth. " The book Is thoroughly practical. The reader Is, therefore, conducted through the leading laws of electricity, then through the metals used by electrotypers, the apparatus, and the depositing processes, up to the final preparation of the work." A rt Journal. Goldsmiths' Work. THE GOLDSMITH'S HANDBOOK. By GEORGE E. GEE, Jeweller, &c. Third Edition, considerably Enlarged, izmo, 35. 6d. cl. bds. "A good, sound educator, which will be accepted as an authority." Horological yonrnal. Silversmiths' Work. THE SILVERSMITH'S HANDBOOK. By GEORGE E. GEE, Jeweller, &c. Second Edition, Revised. lamo, 35. 6d. cloth. " The chief merit of the work is its practical character. . . The workers In the trade will peedily discover its merits when they sit down to study it" English Mechanic. *** The above two works together, strongly half-bound, price 7$. Sheet Metal Working, THE SHEET METAL WORKER'S INSTRUCTOR: For Zinc, Sheet Iron, Copper, and Tin Plate Workers. Containing Rules for describing the Patterns required in the Different Branches of the Trade. By R. H. WARN, Tin Plate Worker. With Thirty-two Plates. 8vo, 75. 6d. cl. Bread and Biscuit Baking. THE BREAD AND BISCUIT BAKER'S AND SUGAR- BOILER'S ASSISTANT. Including a large variety of Modern Recipes. By ROBERT WELLS, Practical Baker. Crown 8vo, zs. cloth. " A large number of wrinkles for the ordinary cook, as well as the baker." Saturday Review. Confectionery for Hotels and Restaurants. THE PASTRYCOOK AND CONFECTIONER'S GUIDE. For Hotels, Restaurants and the Trade in general, adapted also for Family Use. By ROBERT WELLS. Crown 8vo, zs. cloth. " We cannot speak too highly of this really excellent work. In these days of keen competition oar readers cannot do better than purchase this book." Bakers? Times. Ornamental Confectionery. ORNAMENTAL CONFECTIONERY: A Guide for Bakers, Confectioners and Pastrycooks ; including a variety of Modern Recipes, and Remarks on Decorative and Coloured Work. With 129 Original Designs. By ROBERT WELLS. Crown 8vo, cloth gilt, 55. "A valuable work, practical, and should be in the hands of every baker and confectioner. The Illustrative designs are alone worth treble the amount charged for the whole work." Bakers' Times. Flour Confectionery. THE MODERN FLOUR CONFECTIONER. Wholesale and Retail. Containing a large Collection of Recipes for Cheap Cakes, Biscuits, &c. With Remarks on the Ingredients used in their Manufacture. By R. WELLS. Crown 8vo, zs. cloth. " The work is of a decidedly practical character, and In every recipe regard is had to economi- cal working." North British Daily Mail. Laundry Work. LA UN DRY MANAGEMENT. A Handbook for Use in Private and Public Laundries, Including Descriptive Accounts of Modern Machinery and Appliances for Laundry Work. By the EDITOR of "The Laundry Journal." Second Edition. Crown 8vo, zs. 6d. cloth. " This book should certainly occupy an honoured place on the shelves of all housekeepers who wish to keep themselves au courant of the newest appliances and methods." The Queen. IND USTRIAL AND USEFUL ARTS. jg HANDYBOOKS FOR HANDICRAFTS. By PAUL N. HASLUCK, EDITOR OF "WORK" (NEW SERIES); AUTHOR OF "LATHEWORK," "MILLING MACHINES," &c. Crown 8vo, 144 pages, cloth, price is. each. tS" These HANDYBOOKS have been written to supply information for WORKMEN, STUDENTS, and AMATEURS in the several Handicrafts, on the actual PRACTICE o] the WORKSHOP, and are intended to convey in plain language TECHNICAL KNOW- LEDGE of the several CRAFTS. In describing the processes employed, and themanipu- lation of material, workshop terms are used ; workshop practice is fully explained ; and the text is freely illustrated with drawings of modern tools, appliances, and Processes. THE METAL TURNER'S HANDYBOOK. A Practical Manual for Workers at the Foot-Lathe. With over 100 Illustrations. Price is. " The book will be of service alike to the amateur and the artisan turner. It displays thorough knowledge of the subject." Scotsman. THE WOOD TURNER'S HANDYBOOK. A Practical Manual for Workers at the Lathe. With over 100 Illustrations. Price is. "We recommend the book to young turners and amateurs. A multitude of workmen have hitherto sought in vain for a manual of this special industry." Mechanical World. THE WATCH JOBBER'S HANDYBOOK. A Practical Manual on Cleaning, Repairing, and Adjusting. With upwards of 100 Illustrations. Price is. " We strongly advise all young persons connected with the watch trade to acquire and study this Inexpensive wotk."Clerkentvell Chronicle. THE PATTERN MAKER'S HANDYBOOK. -A Practical Manual on the Construction ot Patterns for Founders. With upwards of 100 Illustrations. Price is. " A most valuable, if not indispensable, manual for the pattern maker." Knowledge. THE MECHANIC'S WORKSHOP HANDYBOOK. A Practical Manual on Mechanical Manipulation. Embracing Information on various Handicraft Processes, with Useful Notes and Miscellaneous Memoranda, Comprising about 200 Subjects. Price is. " A very clever and useful book, which should be certainly find a place in all technical schools." Saturday Review. THE MODEL ENGINEER'S HANDYBOOK. A Practical Manual on the Construction of Model Steam Engines. With upwards of 100 illustrations. Price is. " Mr. Hasluck has produced a very good little book." Builder. THE CLOCK JOBBER'S HANDYBOOK. A Practical Manual on Cleaning, Repairing, and Adjusting. With upwards of 100 Illustrations. Price is. " It is of inestimable service to those commencing the trade." Coventry Standard. THE CABINET WORKER'S HANDYBOOK: A Practical Manual on the Tools, Materials, Appliances, and Processes employed in Cabinet Work. With upwards of 100 Illustrations. Price is. Mr. Hasluck's thoroughgoing little Handybook is amongst the most practical guides we have seen for beginners in cabinet-work." Saturday Review. THE WOODWORKER'S HANDYBOOK OF MANUAL IN- STRUCTION. Embracing Information on the Tools, Materials, Appliances and Processes employed in Woodworking. With 104 Illustrations. Price is [Just published. THE MET A L WORKER'S HA ND YBOOK. With upwards of i oo Illustrations. [In preparation. *** OPINIONS OF THE PRESS. " Written by a man who knows, not only how work ought to be done, but how to do it, and 'how to convey his knowledge to others." Engineering. " Mr. Hasluck writes admirably, and gives complete instructions." Engineer. "Mr. Hasluck combines the experience of a practical teacher with the manipulative skill and scientific knowledge of processes of the trained mechanician, and the manuals are marvels of what can be produced at a popular price." Schoolmaster. " Helpful to workmen of all ages and degrees of experience." Daily Chronicle. " Practical, sensible, and remarkably cheap." jfoutnal of Edueation. " Concise, clear and practical." Saturday Review. A very clever and useful book, which should be found in every workshop ; and it should " nd a 40 CROSBY LOCKWOOD & SON'S CATALOGUE. COMMERCE, COUNTING-HOUSE WORK, TABLES, etc. Commercial Education. LESSONS IN COMMERCE. By Professor R. GAMBARO, of the Royal High Commercial School at Genoa. Edited and Revised by JAMES GAULT, Professor of Commerce and Commercial Law in King's College, London. Crown 8vo, 35. 6d. cloth. " The publishers of this work have rendered considerable service to the cause of commercial education by the opportune production of this volume. . . . The work is peculiarly acceptable to English readers and an admirable addition to existing- class-books. In a phrase, we think the-- work attains its object in furnishing a brief account of those laws and customs of British trade with which the commercial man interested therein should be familiar." Chamber of Commerccjoumal. " An invaluable guide in the hands of those who are preparing for a commercial career." Counting' House* Foreign Commercial Correspondence. THE FOREIGN COMMERCIAL CORRESPONDENT: Being Aids to Commercial Correspondence in Five Languages English, French, German, Italian, and Spanish. By CONRAD E. BAKER. Second Edition.. Crown 8vo, 35. 6d. cloth. "Whoever wishes to correspond in all the languages mentioned by Mr. Baker cannot do better than study this work, the materials of which are excellent and conveniently arranged. They consist not of entire specimen letters but what are far more useful short passages, sentences, or phrases expressing the same general idea in various forms." Athenaum. "A careful examination has convinced us that it is unusually complete, well arranged, and' reliable. The book is a thoroughly good one." Schoolmaster. Accounts for Manufacturers. FACTORY ACCOUNTS: Their Principles and Practice. A Handbook for Accountants and Manufacturers, with Appendices on the No- menclature of Machine Details ; the Income Tax Acts ; the Rating of Fac- tories ; Fire and Boiler Insurance ; the Factory and Workshop Acts, &c.> including also a Glossary of Terms and a large number of Specimen Rulings. By EMILE GARCKE and J. M. FELLS. Fourth Edition, Revised and En- larged. Demy 8vo, 250 pages, 6s. strongly bound. "A very interesting description of the requirements of Factory Accounts. . . . the principle of assimilating the Factory Accounts to the general commercial books is one which we thoroughly agree with." Accountants' Journal. " Characterised by extreme thoroughness. Tkere are few owners of factories who would not derive great benefit from the perusal of this most admirable work." Local Government Chronicle, . Modern Metrical Units and Systems. MODERN METROLOGY: A Manual of the Metrical Units and Systems of the Present Century. With an Appendix containing a proposed English System. By Lowis D'A. JACKSON, A.M.Inst.C.E., Author of "Aid to Survey Practice," &c. Large crown 8vo, I2S. 6d. cloth. " We recommend the work to all interested in the practical reform of our weights and mea- sures." Nature. The Metric System and the British Standards. A SERIES OF METRIC TABLES, in which the British Stand- ard Measures and Weights are compared with those of the Metric System at present* in Use on the Continent. By C. H. DOWLING, C.E. 8vo, los. 6d. strongly bound. " Mr. Dowling's Tables are well put together as a ready-reckoner for the conversion of one system into the other." Athenaum. Iron and Metal Trades' Calculator. THE IRON AND METAL TRADES' COMPANION. For expeditiously ascertaining the Value of any Goods bought or sold by Weight, trom is. per cwt. to nas. per cwt., and from one farthing per pound to one shilling per pound. By THOMAS DOWNIE. 396 pp., 95. leather. " A most useful set of tables ; nothing like them before existed." Building News. " Although specially adapted to the iron and metal trades, the tables will be found useful in every other business in which merchandise Is bought and sold by weight." Railway Nrwt, Iron Shipbuilders' and Merchants' Weight Tables. IRON-PLATE WEIGHT TABLES: For Iron Shipbuilders,. Engineers, and Iron Merchants. Containing the Calculated Weights of up- wards of 150,000 different sizes ot Iron Plates, from i foot by 6 in. by J in. to 10 feet by 5 feet by i in. Worked out on the basis of 40 Ibs. to the square foot of Iron of i inch in thickness. Carefully compiled and thoroughly Re- vised by H. BURLINSON and W. H. SIMPSON. Oblong 410, 255. half-bound. "This work will be found of great utility. The authors have had much practical experience of what is wanting in making estimates; and the use of the book Hill save much time in traking elaborate calculations. "English Mechanic. COMMERCE, COUNTING-HOUSE WORK, TABLES, etc. 41 Chadwick's Calculator for Numbers and Weights Combined. THE NUMBER, WEIGHT, AND FRACTIONAL CALCU- LATOR. Containing upwards of 250,000 Separate Calculations, showing at a glance the value at 422 different rates, ranging from T lth of a Penny to 205. each, or per cwt., and 20 per ton, of any number of articles consecu- tively, from i to 470. Any number of cwts., qrs., and Ibs., from i cwt. to 470 cwts. Any number of tons, cwts., qrs., and Ibs., from i to 1,000 tons. By WILLIAM CHADWICK, Public Accountant. Third Edition, Revised and Im- proved. 8vo,i8s., strongly bound for Office wear and tear. IS" Is adapted for the use of Accountants and Auditors, Railway Companies,. Canal Companies, Shippers, Shipping Agents, General Carriers, etc. Ironfounders, Brass founders, Metal Merchants, Iron Manufacturers, Ironmongers, Engineers, Machinists, Boilet Makers, Millwrights, Roofing, Bridge and Girder Makers, Colliery Proprietors, etc. Timber Merchants, Builders, Contractors, Architects, Surveyors, Auctioneers, Valuers, Brokers, Mill Owners and Manufacturers, Mill Furnishers, Merchants, and General Wholesale Tradesmen. Also for the Apportionment of Mileage Charges for Railway Traffic. *** OPINIONS OF THE PRESS. " It is as easy of reference for any answer or any number of answers as a dictionary, and the references are even more quickly made. For making up accounts or estimates the book must prove invaluable to all who have any considerable quantity of calculations involving price ana measure in any combination to do." Engineer. " The most complete and practical ready reckoner which it has been our fortune yet to see. 16 Is difficult to imagine a trade or occupation in which it could not be of the greatest use, either in saving human labour or in checking work. The publishers have placed within the reach of every commercial man an invaluable and unfailing assistant." The Miller. " The most perfect work of the kind yet prepared." Glasgow Herald. Harben's Comprehensive Weight Calculator. THE WEIGHT CALCULATOR. Being a Series of Tables upon a New and Comprehensive Plan, exhibiting at One Reference the exact Value of any Weight from i Ib. to 15 tons, at 300 Progressive Rates, from id. to i68s. per cwt., and containing 186,000 Direct Answers, which, with their Combinations, consisting of a single addition (mostly to be performed at sight), will afford an aggregate of 10,266,000 Answers ; the whole being calcu- lated and designed to ensure correctness and promote despatch. By HENRY HARBEN, Accountant. Fourth Edition, carefully Corrected. Royal 8vo> i 55. strongly half-bound. " A practical and useful work of reference for men of business generally ; it is the best of the kind we have seen." Ironmonger. "Of priceless value to business men. It is a necessary book In all mercantile offices." Shef- field Independent. Harben's Comprehensive Discount Guide. THE DISCOUNT GUIDE. Comprising several Series of Tables for the use of Merchants, Manufacturers, Ironmongers, and others, by which may be ascertained the exact Profit arising from any mode of using Discounts, either in the Purchase or Sale of Goods, and the method of either Altering a Rate of Discount or Advancing a Price, so as to produce, by one operation, a sum that will realise any required profit after allowing one or more Discounts : to which are added Tables of Profit or Advance from i J to- 90 per cent., Tables of Discount from ij to g8f per cent., and Tables of Com- mission, &c., from to 10 per cent. By HENRY HARBEN, Accountant, Author of " The Weight Calculator." New Edition, carefully Revised and Corrected, Demy 8vo, 544 pp., i 55. half-bound. " A book such as this can only be appreciated by business men, to whom the saving of time means saving of money. We have the high authority of Professor J. R. Young that the tables throughout the work are constructed upon strictly accurate principles. The work is a model 1 of typographical clearness, and must prove of great value to merchants, manufacturers, and general traders." British Trade Journal. New Wages Calculator. TABLES OF WAGES at 54, 52, 50 and 48 Hours per Week. Showing the Amounts cf Wages from One-quarter-of-an-hour to Sixty-four hours in each case at Rates of Wages advancing by One Shilling from 45. to. 555. per week. By THOS. GARBUTT, Accountant. Square crown ^vp. 6s.. half-bound. [Just published 42 CROSBY LOCK WOOD <* SON'S CATALOGUE. "DIRECT CALCULATOR S," By M. B. COTSWORTH, of Holgate, York. QUICKEST AND MOST ACCUEATE MEANS OF CALCULATION KNOWN. ENSURE ACCURACY and SPEED WITH EASE, SAVE TIME and MONEY. Accounts may be charged out or checked by these means in about one third the time required by ordinary methods of calculation. These unrivalled " Calculators " have very clear and original contrivances for instantly finding the exact answer, by its fixed position, without ven sighting the top or side of the page. They are varied in arrange- ment to suit the special need of each particular trade. Ail the leading firms now use Calculators, even where they employ experts. N.B. Indicator letters in brackets should be quoted. "RAILWA Y & TRADERS' CALCULATOR " (R. & T.) IDS. 6d. Including Scale of Charges for Small Parcels by Merchandise Trains. " Direct Calculator "the only Calculator published giving exact charge for Cwts., Qrs. and Lbs., together. " Calculating Tables" for every id. rate to iocs, per ton. " Wages Calculator." " Percentage Rates." " Grain, Flour, Ale, &c., Weight Calculators." " DIRECT CALCULATOR (I R) " including all the above except " Calculating Tables." 75. "DIRECT CALCULATOR (A)" by %d., 2*. each opening, exact pence to 405. per ton. 55. "DIRECT CALCULATOR (B) " by id., 45. each opening, exact pence to 40$. per ton. 45. 6d. "DIRECT CALCULATOR (C) " by id. (with Cwts. and Qrs. to nearest farthing), to 405. per ton. 45. 6d. "DIRECT CALCULATOR (Ds) " by id. gradations. (Single Tons to 50 Tons, then by fifties to 1,000 Tons, with Cwts. values below in exact pence payable, fractions of \d,. and upwards being counted as id. 6s. 6d. "DIRECT CALCULATOR (D) " has from 1,000 to 10,000 Tons in addition to the (Ds) Calculator. 75. 6d. "DIRECT CALCULATOR (Es) " by id. gradations. (As (D) to 1,000 Tons, with Cwts. and Qrs. values shown separately to the nearest farthing). 5 s. 6d. "DIRECT CALCULATOR (E) " has from 1,000 to 10,000 Tons in addition to the (Es) Calculator. 6s. 6d. "DIRECT CALCULATOR (F) " by id., 25. each opening, exact pence to 405. per ton. 45. 6d. -" DIRECT CALCULATOR (G) " by id., is. each opening ; 6 in. by 9 in. Nearest \d. Indexed (G I) 3$. 6d. zs. 6d. " DIRECT CALCULATOR (H) " by id., is. each opening ; 6 in. by 9 in. To exact pence. Indexed (H I) 35. 6d. zs. 6d. " DIRECT CALCULATOR (K) " Showing Values of Tons, Cwts. and Qrs. in even pence (fractions of id. as id.), for the Retail Coal Trade. 45. 6d. "RAILWAY AND TIMBER TRADES MEASURER AND CAL- CULATOR (T)" (as prepared for the Railway Companies). The only book published giving true content of unequal sided and round timber by eighths of an inch, quarter girth, Weights from Cubic Feet Standards, Superficial Feet, and Stone to Weights Running Feet from lengths of Deals Standard Multipliers Timber Measures Customs Regulations, &c. 35. 6d. AGRICULTURE, FARMING, GARDENING, etc. 43 AGRICULTURE, FARMING, GARDENING, etc. Dr. Fr cam's New Edition of "The Standard Treatise on Agriculture." THE COMPLETE GRAZIER, and FARMER'S and CATTLE- BREEDER'S ASSISTANT: A Compendium of Husbandry. Originally Written by WILLIAM YOUATT. Thirteenth Edition, entirely Re-written, considerably Enlarged, and brought up to the Present Requirements of Agricultural Practice, by WILLIAM FREAM, LL.D., Steven Lecturer In the University of Edinburgh, Author of "The Elements of Agriculture, 1 &c. Royal 8vo, 1,100 pp., with over 450 Illustrations. i us. 6d. strongly and handsomely bound. EXTRACT FROM PUBLISHERS' ADVERTISEMENT. " A treatise that made its original appearance in the first decade of the century, and that enters upon its Thirteenth Edition before the century has run its course, has undoubtedly established its position as a work of permanent value. . . The phenomenal progress of the last dozen years in the Practice and Science of Fanning has rendered it necessary, however, that the volume should De re- written,. . . . and for this undertaking the publishers were fortunate enough to secure tne services of Dr. FREAM, whose high attainments in all matters pertaining to agriculture have been so emphatically recognised by the highest professional and official authorities. la carrying out his editorial duties, Dr. FREAM has been favoured with valuable contributions by froi. J. WORTLEY AXE, Mr. E. BROWN, Dr. BERNARD DYER, Mr. W. J. MALDEN, Mr. R. H. REW, Prof. SHELDON, Mr. T. SINCLAIR, Mr. SANDERS SPENCER, and others. " As regards the illustrations of the work, no pains have been spared to make them as repre- sentative and characteristic as possible, so as to be practically useful to the Farmer and Grazier. SUMMARY OF CONTENTS. BOOK I. ON THE VARIETIES, BREED- ING, REARING, FATTENING, AND MANAGEMENT OF CATTLE. BOOK II. ON THE ECONOMY AND MAN- AGEMENT OF THE DAIRY. BOOK III. ON THE BREEDING, REAR- ING, AND MANAGEMENT OF HORSES. BOOK IV. ON THE BREEDING, REAR- ING, AND FATTENING OF SHEEP. BOOK V. ON THE BREEDING, REARING, AND FATTENING OF SWINE. BOOK VI. ON THE DISEASES OF LIVE STOCK. BOOK VII. ON THE BREEDING, REAR- ING, AND MANAGEMENT OF POULTRY, BOOK VIII. ON FARM OFFICES AND IMPLEMENTS OF HUSBANDRY. BOOK IX. ON THE CULTURE AND MAN- AGEMENT OF GRASS LANDS. BOOK X. ON THE CULTIVATION AND APPLICATION OF GRASSES, PULSE, AND ROOTS. BOOK XI. ON MANURES AND THEIR APPLICATION TOGRASS LAND&CROPS BOOK XII. MONTHLY CALENDARS OF FARMWORK. V OPINIONS OF THE PRESS ON THE NEW EDITION. " Dr. Fream is to be congratulated on the successful attempt he has made to give us a work which will at once become the standard classic of the farm practice of the country. We believe that it will be found that it has no compeer among the many works at present in existence. . . . The illustrations are admirable, while the frontispiece, which represents the well-known bull, New Year's Gift, bred by the Queen, is a work of art." The Times. " The book must be recognised as occupying the proud position of the most exhaustive work /reference in the English bnguage on the subject with which it dzz\s."Athenaut. " The most comprehensive guide to modern farm practice that exists in the English language to-day. . . . The book is one that ought to be on every farm and in the library of every land- owner." Mark Lane Express. " In point of exhaustiveness and accuracy the work will certainly hold a pre-eminent and unique position among books dealing with scientific agricultural practice. It is, in fact, an agri- cultural library of itself."- North British Agriculturist. " A compendium of authoritative and well-ordered knowledge on every conceivable branch of the work of the live stock farmer ; probably without an equal in this or any other country." Yorkshire Post. British Farm Live Stock. FARM LIVE STOCK OF GREAT BRITAIN. By ROBERT WALLACE, F.L.S., F.R.S.E., &c., Professor of Agriculture and Rural Eco- nomy in the University of Edinburgh. Third Edition, thoroughly Revised and considerably Enlarged. With over 120 Phototypes of Prize Stock. Demy 8vo, 384 pp., with 79 Plates and Maps, izs. 6d. cloth. " A really complete work on the history, breeds, and management of the farm stock of Great Britain, and one which is likely to find its way to the shelves of every country gentleman's library." The Times. " The latest edition of ' Farm Live Stock of Great Britain ' is a production to be proud of, and Its issue not the least of the services which its author has rendered to agricultural science." Scottish Farmer, " The book is very attractive . . . and we can scarcely imagine the existence of a farmer who would not like to have a copy of this beautiful work." Mark Lam Express. " A work which will long be regarded as a standard authority wl enever a concise history and iSescription of the breeds of live stock in the British Isles is required." Bell's Weekly Messenger. 44 CROSBY LOCKWOOD & SON'S CATALOGUE. Dairy Farming. BRITISH DAIRYING. A Handy Volume on the Work of the Dairy-Farm. For the Use of Technical Instruction Classes, Students in Agricultural Colleges, and the Working Dairy-Farmer. By Prof. J. P. SHELDON, ate Special Commissioner of the Canadian Government, Author of " Dairy Farming," &c. With numerous Illustrations. Crown 8vo, 25. 6d. cloth. " We confidently recommend it as a text-book on dairy farming." Agricultural Gazette. "Probably the best half-crown manual on dairy work that has yet been produced." North British Agriculturist. " It is the soundest little work we have yet seen on the subject." The Times. Dairy Manual. MILK, CHEESE AND BUTTER: A Practical Handbook on their Properties and the Processes of their Production, including a Chapter on Cream and the Methods of its Separation from Milk. By JOHN OLIVER, late Principal of the Western Dairy Institute, Berkeley. With Coloured Plates and 200 Illusts. Crown 8vo, ?s.6d. cloth. [ Just published. " An exhaustive and masterly production. It may t>e cordially recommended to all students and practitioners of dairy science." N.B. Agriculturist. " We strongly recommend this very comprehensive and carefully- written book to dairy-farmers and students of dairying. It is a distinct acquisition to the library of the agriculturist." Agricul- tural Gazette. Agricultural Facts and Figures. NOTE-BOOK OF AGRICULTURAL FACTS AND FIGURES FOR FARMERS AND FARM STUDENTS. By PRIMROSE McCoNNEU., B.Sc. Fifth Edition. Royal szmo, roan, gilt edges, with band, 45. " Literally teems with information, and we can cordially recommend it to all connected with agriculture." North British Agriculturist, Small Farming. SYSTEMATIC SMALL FARMING; or, The Lessons of my Farm. Being an Introduction to Modern Farm Practice for Small Farmers. By R. SCOTT BURN. With numerous Illustrations, crown 8vo, 6s. cloth. " This Is the completest book of its class we have seen, and one which every amateur farmer will read with pleasure and accept as a guide." Field, Modern Farming. OUTLINES OF MODERN FARMING. By R. SCOTT BURN. Soils, Manures, and Crops Farming and Farming Economy Cattle, Sheep, and Horses Management of Dairy, Pigs, and Poultry Utilisation of Town-Sewage, Irrigation, &c. Sixth Edition. In One Vol., 1,250 pp., half- bound, profusely Illustrated, 125. " The aim of the author has been to make his work at once comprehensive and trustworthy and he has succeeded to a degree which entitles him to much credit." Momine Advertiser, Agricultural Engineering. FARM ENGINEERING, THE COMPLETE TEXT-BOOK OF. Comprising Draining and Embanking ; Irrigation and Water Supply ; Farm Roads, Fences, and Gates ; Farm Buildings ; Barn Implements and Ma- chines ; Field Implements and Machines ; Agricultural Surveying, &c. By Prof. JOHN SCOTT. 1,150 pages, half-bound, with over 600 Illustrations, I2S. "Written with great care, as well as with knowledge and ability. The author has done his work well ; we have found him a very trustworthy guide wherever we have tested his statements. The volume will be of great value to agricultural students," Mark Lane Express. Agricultural Text-JSoo/c. THE FIELDS OF GREAT BRITAIN : A Text-Book of Agriculture, adapted to the Syllabus of the Science and Art Department. For Elementary and Advanced Students. By HUGH CLEMENTS (Board of Trade). Second Edition, Revised, with Additions. i8mo, 2s. 6d. cloth, "A most comprehensive volume, giving a mass of information." Agricultural Economist. "It tea long time since we have seen a book which has pleased us more, or which contains nch a vast and useful fund of knowledge." Educational Times. Tables for Farmers, etc. TABLES, MEMORANDA, AND CALCULATED RESULTS for Farmers. Graziers, Agricultural Students, Surveyors, Land Agents, Auc- tioneers, etc. With a New System of Farm Book-keeping. By SIDNEY FRAN- CIS. Third Edition, Revised. 272 pp., waistcoat- pocket size, is. 6d. leather. "Weighing less than i oz., and occupying no more space than a match box, it contains a mass of facts and calculations which has never before, in such handy form, been obtainable. Every operation on the farm is dealt with. The work may be taken as thoroughly accurate, the whole of the tables having been revised by Dr. Fream. We cordially recommend it."etfs Weekly Attssengtr. AGRICULTURE, FARMING, GARDENING, etc. 45 ^Artificial Manures and Foods. FERTILISERS AND FEEDING STUFFS: Their Proper- ties and Uses. A Handbook for the Practical Farmer. By BERNARD DYER, D.Sc. (Lond.) With the Text of the Fertilisers and Feeding Stuffs Act of 1893, the Regulations and Forms of the Board of Agriculture and Notes on the Act by A. J. DAVID, B.A., LL.M., of the Inner Temple, Barrister-at-Law. Crown 8vo, 120 pages, is. cloth. [Just published. " An excellent shilliugsworth. Dr. Dyer has done farmers good service in placing at their dis- posal so much useful information in so intelligible a form." The Times. The Management of Bees. BEES FOR PLEASURE AND PROFIT: A Guide to the Manipulation of Bees, the Production of Honey, and the General Manage- ment of the Apiary. By G. GORDON SAMSON. Crown 8vo, is. cloth. " The intending bee-keeper will find exactly the kind of information required to enable him to make a successful start with his hives. The author is a thoroughly competent teacher, and his book may be commended." Morning Post. Farm and Estate Book-keeping. BOOK-KEEPING FOR FARMERS < ESTATE OWNERS. A Practical Treatise, presenting, in Three Plans, a System adapted for all Classes of Farms. By JOHNSON M. WOODMAN, Chartered Accountant. Second Edition, Revised. Crown 8vo, 35. 6d. cloth boards ; or 2s. 6d. cloth limp. " The volume is a capital study of a most important subject." Agricultural Gazette. The young farmer, land agent, and surveyor will find Mr. Woodman's treatise more than epay its cost and study.' 1 Building News. Farm, Account Book. WOODMAN'S YEARLY FARM ACCOUNT BOOK. Giving a Weekly Labour Account and Diary, and showing the Income and Expen- diture under each Department of Crops, Live Stock, Dairy, &c. &c. With Valuation, Profit and Loss Account, and Balance Sheet at the end of the Year. By JOHNSON M. WOODMAN, Chartered Accountant, Author of " Book- keeping for Farmers." Folio, 75. 6d. half -bound. [culture, "Contains every requisite form for keeping farm accounts readily and accurately." Agri~ Early Fruits, Flowers, and Vegetables. THE FORCING GARDEN ; or, How to Grow Early Fruits, Flowers, and Vegetables. With Plans and Estimates for Building Glass- houses, Pits, and Frames. By SAMUEL, WOOD. Crown 8vo, 3$. 6d. cloth. 1 ' A good book, and fairly fills a place that was in some degree vacant. The book is written with great care'and contains a great deal of valuable teaching." Gardeners' Magazine. Good Gardening. A PLAIN GUIDE TO GOOD GARDENING ; or, How to Grow Vegetables, Fruits, and Flowers. By S. WOOD. Fourth Edition, with con- siderable Additions, &c., and numerous Illustrations. Crown 8vo, 35. 6d. cl. " A very good book, and one to be highly recommended as a practical guide. The practical directions are excellent." Atheneeunt. " May be recommended to young gardeners, cottagers, and specially to amateurs, for the plain, simple, and trustworthy information it gives on common matters too often neglected " Gardeners' Chronicle. Gainful Gardening. MULTUM-IN-PARVO GARDENING; or, How to make One Acre of Land produce 620 a-year by the Cultivation of Fruits and Vegetables ; also, How to Grow Flowers in Three Glass Houses, so as to realise 176 per annum clear Profit. By SAMUEL WOOD, Author of " Good Gardening," &c. Fifth and Cheaper Edition, Revised, with Additions. Crown 8vo, is. sewed. "We are bound to recommend it as not only suited to the case of the amateur and gentleman's .gardener, but to the market grower." Gardeners' Magazine. Gardening for Ladies. THE LADIES' MULTUM-IN-PARVO FLOWER GARDEN, and Amateurs 1 Complete Guide. With Illusts. By S. WOOD. Cr.Svo, 35. 6d. cl. Receipts for Gardeners. GARDEN RECEIPTS. Edited by CHARLES W. QUIN. i2mo, is. 6d. cloth limp. Market Gardening. MARKET AND KITCHEN GARDENING. By Contributors to "The Garden." Compiled by C. W. SHAW, late Editor of "Gardening Illustrated." izino , 35. 6d. cloth boards. 46 CROSBY LOCK WOOD Surveyor, Valuer, &c. Royal szmo, 55. cloth. " A neat and concise book of reference, containing an admirable and clearly-arranged list of prices for inventories, and a very practical guide to determine the value of furniture.&c." Standard, " Contains a large quantity of varied and useful information as to the valuation for purchase, sale, or renewal of leases, annuities and reversions, and of property generally, with prices fo Inventories, and a guide to determine the value of interior fittings and other effects." Builder. Auctioneewng. AUCTIONEERS: THEIR DUTIES AND LIABILITIES. A Manual of Instruction and Counsel for the Young Auctioneer. By ROBERT SQUIBBS, Auctioneer. Second Edition, Revised and partly Re-written. Demy 8vo, 125. Od. cloth, %* OPINIONS OF THE PRESS. " The standard text-book on the topics of which it treats." Athenceum. " The work is one of general excellent character, and gives much information in a compen- dious and satisfactory form." Builder. " May be recommended as giving a great deal of information on the law relating to auctioneers, in a very readable form." Law Journal. " Auctioneers may be congratulated on having so pleasing a writer to minister to their special needs." Solicitors' Journal. "Every auctioneer ought to possess a copy of this excellent work." Ironmonger. " Of great value to the profession. . . . We readily welcome this book from the fact that it treats the subject in a manner somewhat new to the profession." Estates Gazette, Inwood's Estate Tables. TABLES FOR THE PURCHASING OF ESTATES, Freehold, Copyhold, or Leasehold; Annuities, Advowsons, etc., and for the Renewing of Leases held under Cathedral Churches, Colleges, or other Corporate bodies, for Terms of Years certain, and for Lives : also for Valuing Reversionary Estates, Deterred Annuities, Next Presentations, &c. ; together with SMART'S Five Tables of Compound Interest, and an Extension of the same to Lower and Intermediate Rates. By W. INWOOD. 24th Edition, with considerable Additions, and new and valuable Tables of Logarithms for the more Difficult Computations of the Interest of Money, Discount, Annuities, &c., by M. FEDOR THOMAN, of the Societe Cr6dit Mobilier oi Paris. Crown 8vo, 8s. cloth. "Those interested in the purchase and sale of estates, and in the adjustment of compensation cases, as well as in transactions in annuities, life insurances, &c., will find the present edition of eminent service." Engineering. " ' Inwood's Tables ' still maintain a most enviable reputation. The new issue has been enriched by large additional contributions by M. Fedor Thoman, whose carefully arranged Tables cannot fail to be of the utmost utility." -Mining Jemrnal. Agricultural Valuer's Assistant. THE AGRICULTURAL VALUER'S ASSISTANT. A Prac- tical Handbook on the Valuation of Landed Estates ; including Rules and Data for Measuring and Estimating the Contents, Weights, and Values of Agricultural Produce and Timber, and the Values of Feeding Stuffs, Manures, and Labour ; with Forms of Tenant-Right-Valuations, Lists of Local Agricultural Customs, Scales of Compensation under the Agricultural Holdings Act, &c. &c. By TOM BRIGHT, Agricultural Surveyor. Second Edition, much Enlarged. Crown 8vo, 55. cloth. "Full of tables and examples in connection with the valuation of tenant-right, estates, labour, contents, and weights of timber, and farm produce of all kinds." Agricultural Gazette. " An eminently practical handbook, full of practical tables and data of undoubted interest and ralue to surveyors and auctioneers in preparing valuations of all kinds." Farmer. Plantations and Underwoods. POLE PLANTATIONS AND UNDERWOODS: A Practical Handbook on Estimating the Cost of Forming, Renovating, Improving, and Grubbing Plantations and Underwoods, their Valuation for Purposes ot Transfer, Rental, Sale, or Assessment. By TOM BRIGHT, Author of " The AgriculturalValuer's Assistant," &c. Crown 8vo, 35. 6d. cloth. " To valuers, foresters and agents it win be a welcome aid." North British Agriculturist. "Well calculated to assist the valuer in the discharge of his duties, and of undoubted interest and use both to surveyors and auctioneers in preparing valuations of all kinds." Kent Hernia. AUCTIONEERING, VALUING, LAND SURVEYING, eU. 47 Hudson's Land Valuer's Pocket-Booh. THE LAND VALUER'S BEST ASSISTANT: Being Tables on a very much Improved Plan, for Calculating the Value of Estates. With Tables for reducing Scotch, Irish, and Provincial Customary Acres to Statute Measure, &c. By R. HUDSON, C.E. New Edition. Royal 32010, 45. leather. " Of incalculable value to the country gentleman and professional man." Farmers' yournal. Ewart's Land Improver's Pocket-Book. THE LAND IMPROVER'S POCKET-BOOK OF FORMULA, TABLES, and MEMORANDA required in any Computation relating to the Permanent Improvement of Landed Property. By JOHN EWART, Surveyor. Second Edition. Royal 3210.0, 45. leather. Complete Agricultural Surveyor's Pocket-Book. THE LAND VALUER'S AND LAND IMPROVER'S COM- PLETE POCKET-BOOK. Being of the above Two Works bound together. Leather, with strap, 7$. 6d. House Property. HANDBOOK OF HOUSE PROPERTY. A Popular and Practi- cal Guide to the Purchase, Mortgage, Tenancy, and Compulsory Sale of Houses and Land, including the Law of Dilapidations and Fixtures ; with Examples of all kinds of Valuations, Useful Information on Building, and Suggestive Elucidations of Fine Art. By E. L. TARBUCK, Architect and Surveyor. Fifth Edition, Enlarged. I2mo, 55. cloth. "The advice Is thoroughly practical." Law Journal. 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Comprising the Local Government Act, 1894 (establishing District and Parish Councils) ; Finance Act, 1894 (imposing the New Death Duties) ; Merchant Shipping Act, 1894; Prevention of Cruelty to Children Act, 1894; Building Societies^ Act, 1894 5 ,0/ tits Hours Act, 1892; Small Holdings Act, 1892; and many other important new Acts. Crown 8vo, 750 pp., price 6s. Sd. (saved at every consultation!), strongly bound in cloth. [Just published, *** The Booh will be found to comprise (amongst other matter) THE RIGHTS AND WRONGS OF INDIVIDUALS LANDLORD AND TENANT VENDORS AND PURCHASERS LEASES AND MORTGAGES PRINCIPAL AND AGENT PARTNERSHIP AND COMPANIES MASTERS, SERVANTS, AND WORKMEN CONTRACTS AND AGREEMENTS BORROWERS, LENDERS, AND SURETIES SALE AND PURCHASE OF GOODS CHEQUES, BILLS, AND NOTES -BILLS OF SALE BANKRUPTCY-RAILWAY AND SHIPPING LAW- LIFE, FIRE, AND MARINE INSURANCE ACCIDENT AND FIDELITY INSURANCE CRIMINAL LAW- PARLIAMENTARY ELECTIONS-COUNTY COUNCILS-DISTRICT COUNCILS PARISH COUNCILS MUNICIPAL CORPORATIONS LIBEL AND SLANDER PUBLIC HEALTH AND NUISANCES COPYRIGHT, PATENTS, TRADE MARKS HUSBAND AND WIFE DIVORCE- INFANCY CUSTODY OF CHILDREN TRUSTEES AND EXECUTORS CLERGY, CHURCH- WARDENS, ETC. 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V* OPINIONS OF THE PRESS. 11 A complete code of English Law, written In plain language, which all can understand. Should be in the hands of every business man, and all who wish to abolish lawyers' bills. . . .' Weekly Tintts. 11 A useful and concise epitome of the law, compiled with considerable care." Law Magazine. "A complete digest of the most useful facts which constitute English law." Globe. "Admirably done, admirably arranged, and admirably cheap." Leeds Mercury. " A concise, cheap and complete epitome of the English law. So plainly written that he who runs may read, and he who reads may understand." Figaro. "The latest edition of this popular book ought to be in every business establishment, and on every library table." Sheffield Post. " A complete epitome of the law ; thoroughly intelligible to non-professional readers." Belts Life. Legal Guide for Pawnbrokers, THE LAW OF LOANS AND PLEDGES. With Statutes and a Digest of Cases. By H. C. FOLKARD, Esq., Barrister-at-Law. Fcap. 8vo, 35. 6d. cloth. The Law of Contracts. LABOUR CONTRACTS : A Popular Handbook on the Law of Contracts for Works and Services. By DAVID GIBBONS. Fourth Edition, Appendix of Statutes by T. F. UTTLEY, Solicitor. Fcap. 8vo, 35. 6d. cloth. The Factory Acts. SUMMARY OF THE FACTORY AND WORKSHOP ACTS (1878-1891). For the Use of Manufacturers and Managers. By EMILE GARCKE and J. M. FELLS. (Reprinted from " FACTORY ACCOUNTS.") Crown 8vo, 6d. sewed. OODEN, SMALS AND CO. LIMITED, PRINTERS, GREAT SAFFRON HILL, B.C. LONDON, 1862, PRIZE MEDAL Was awarded to the Publishers of WEALE'S SERIES RUDIMENTARY SCIENTIFIC,EDUCATIONAL, AND CLASSICAL. Comprising nearly Three Hun dred and Fifty distinct works in almost every department of Science, Art, and Education, recommended to the notice of Engineers, Architects, Builders, Artisans, and Students generally, as -well as to those interested in Workmen's LibrarieT, Instittitions, Colleges, Schools, Science Cla ses, &*c., &~c. tS" " WEALE'S SERIES includes Text-Books on almost every branch of Science and Industry, comprising such subjects as Agriculture, Architecture and Building, Civil Engineering, Fine Arts, Mechanics and Mechanical Engineering, Physical and Chemical Science, and many miscellaneous Treatises. The whole are constantly undergoing revision, and new editions, brought up to the latest discoveries in scientific research, are constantly issued. The prices at which they are sold are as low as their excellence is assured." American Literary Gazette. 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PHILADELPHIA, 1876, THE PRIZE MEDAL Was awarded to the Publishers for Books : Rudimentary, Scientific, "WEALE'S SERIES," ETC. CROSBY LOCKWOOD & SON, STATIONERS' HALL COURT, LUDGATE HILL, LONDON, E.C, * # * 'Catalogues post free on application. WEALE'S RUDIMENTARY SERIES. WEALE'S RUDIMENTARY SCIENTIFIC SERIES. V* The volumes of this Series are' freely Illustrated with Woodcuts, or otherwise, where requisite. Throughout the fol- lowing List it must be understood that the books are bound in limp cloth, unless otherwise stated ; but the volumes marked with a % may also be had strongly bound in cloth boards for dd. extra. JV.S. In ordering from this List it is recommended, as a means of facilitating business and obviating- error, to quote the numbers affixea to the volumes, as well as the titles and prices. CIVIL ENGINEERING, SURVEYING, ETC. No. 31. WELLS AND WELL-SINKING. By JOHN GEO. SWINDELL, A.R.I.B.A., and G. R. BURNELL, C.E. Revised Edition. 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