r 
 
 9/B&^
 

 
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 s \2v~J~f" 
 
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 GENERAL OFFICE OF THE WESTERN UNION TELEGRAPH COMPANY, CORNER 
 BROADWAY AND LIBERTY STREET, NEW YORK.
 
 ^MODERN PRACTICE 
 
 or THE 
 
 ELECTRIC TELEGRAPH. 
 
 .X 
 
 A HANDBOOK 
 
 TOB 
 
 ELECTRICIANS AND OPERATORS. 
 
 BY FRANK L. POPE. 
 
 SIXTH EDITION. 
 
 REVISED AND ENLARGED. 
 
 D. VAN NOSTRAND, Publisher, 
 
 23 MTTBBAY STBEET & 27 WABBEX STBEBT. 
 1872.
 
 Entered according to act of Congress, in the year 1372, by 
 
 D. VAN NOSTRAND, 
 In the Office of the Librarian of Congress, at Washington.
 
 -rx 
 
 PREFACE TO THE FOURTH EDITION. 
 
 During the quarter of a century which has elapsed since the 
 introduction of the Electric Telegraph in the United States, thosd 
 engaged in its service have been almost entirely dependent upon 
 verbal instruction, and long practical experience, for a thorough 
 technical knowledge of their profession. The works accessible 
 to the American telegrapher have been of a popular, rather than 
 of a strictly scientific character, or else of so elementary a nature 
 as to be of little service except to the most inexperienced stu- 
 dents. It is true that a number of excellent foreign works have 
 appeared within a few years ; yet the difficulty and expense of 
 obtaining them, as well as their want of applicability to the 
 American telegraphic system, has prevented their general circu- 
 lation among the class for which this work is more especially 
 designed. 
 
 The unexpectedly favorable reception which has been accorded 
 to the first three editions of this work, has led the author to 
 believe that it has, to some extent, supplied the acknowledged 
 deficiency which had previously existed in this branch of litera- 
 ture. The present edition has been carefully revised, as well as 
 enlarged by the addition of much new matter, and is believed to 
 embrace all the recent discoveries and improvements in practical 
 telegraphy, which have successfully passed through the test of 
 actual experience. 
 
 The methods of testing telegraph lines and apparatus by actual 
 measurement, which are now universally employed in Europe, 
 and to some extent in this country, have been treated upon to 
 an extent commensurate with the importance of the subject. It 
 is hoped that, with the aid of this work, the student may obtain 
 a complete and satisfactory knowledge of this useful and beauti- 
 ful system. 
 
 The principles laid down for the guidance of the student in 
 the formation of the telegraphic alphabet, and the subsequent
 
 IV PREFACE. 
 
 progressive exercises intended for practice with the key, differ 
 but slightly from those employed by the author, while teaching 
 a class of students for the American Telegraph Company in 1864. 
 This plan was believed at that time to be original, but as a method 
 of teaching, involving substantially the same principles, was 
 devised and subsequently published by Prof. J. E. Smith, in his 
 Manual of Telegraphy, it seems proper to make this explanation 
 of the circumstances. 
 
 Among the additional matter in the present edition will be 
 found an entire new chapter upon the Eecent Improvements in 
 Telegraphic Practice, as well as a number of articles in the 
 Appendix, on the Equipment of Telegraph Lines, the Working 
 Capacity of Telegraph Lines, and the Electrical Tension of Bat- 
 teries and Lines, etc., etc. 
 
 Most of the illustrations in this volume have been engraved 
 expressly for its pages, from original drawings by the author. 
 
 In conclusion, the author desires to express his acknowledg- 
 ments to his friend David Brooks, for much valuable aid in the 
 preparation of this work, especially of the present edition ; and 
 he would likewise take occasion to thank Mr. G. Farmer, for 
 information which has been kindly supplied by him. Much 
 useful material has also been obtained from Sabine's Electric 
 Telegraph, Culley's Hand-Book of the Electric Telegraph, Clark's 
 Electrical Measurement, Varley's Report on the Condition of the 
 Western Union Lines, and the columns of The Telegrapher. 
 
 ELIZABETH, N. J., January, 1871.
 
 CONTENTS. 
 
 CHAPTER I 
 
 ORIGIN OF THE ELECTRIC CURRENT. GALVANIC BATTERIES. 
 
 MM. 
 
 Simple Galvanic Circuit 9 
 
 Conductors and Non- Conductors 10 
 
 Electrical Tension 11 
 
 Electrical Quantity 11 
 
 The Daniell Battery 12 
 
 Effect of Continued Action 13 
 
 The Deposit of Copper upon the Porous Cup It 
 
 Renewal of the Battery H 
 
 Application of the Darnell Battery to Main Circuits 13 
 
 The Grove Battery 15 
 
 Setting up a Grove Battery 16 
 
 The Carbon Battery 17 
 
 Power of the Carbon Battery 19 
 
 Insulation of Batteries 20 
 
 CHAPTER II. 
 
 ELECTRO-MAGNETISM. 
 
 Deflection of the Magnetic Needle 21 
 
 Electro-Magnets 22 
 
 Intensity and Quantity Magnet 22 
 
 CHAPTER III. 
 
 TELEGRAPHIC CIRCUITS. 
 
 Resistance of the Circuit 24 
 
 Electrical Measurement 25 
 
 Resistance Coils 25 
 
 Simple Telegraphic Circuit 25 
 
 The Earth Circuit 26 
 
 Arrangement of the Batteries 26 
 
 Intermediate Stations 28
 
 VI 
 
 CONTEXTS. 
 
 The Morse System 26 
 
 Other Telegraphic Systems 27 
 
 CHAPTER IV. 
 
 THE MORSE, OB AMERICAN TELEGRAPHIC SYSTEM. 
 
 The Morse Signal Key 28 
 
 The Morse Register 29 
 
 The Relay Magnet 30 
 
 The Sounder 32 
 
 Arrangement of a Terminal Station 34 
 
 Arrangement of a "Way Station , 35 
 
 Adjustment of the Apparatus 3G 
 
 SWITCHES OR COMMUTATORS 37 
 
 The Plug Switch 39 
 
 The Universal Switch 39 
 
 Arrangement of the Connections 41 
 
 Jones' Lock Switch 41 
 
 Lightning Arresters. 42 
 
 The Plate Arrester 43 
 
 Bradley's Arrester 43 
 
 REPEATERS 45 
 
 "Wood's Button Repeater 46 
 
 Hicks' Automatic Repeater 47 
 
 Milliken's Repeater. 50 
 
 Bunnell's Repeater 52 
 
 Combination Locals 55 
 
 Local Circuit Changer 56 
 
 Technical Terms used in the Telegraph Service 57 
 
 CHAPTER V. 
 
 INSULATION. 
 
 The Glass Insulator 59 
 
 The "Wade Insulator 60 
 
 The Hard Rubber Insulator. 60 
 
 The Leflerts Insulator 61 
 
 The Brooks Insulator 61 
 
 Brooks' Stone-ware Insulator 62 
 
 Mode of Testing Insulators 62 
 
 Escape 63 
 
 "Weather Cross 63 
 
 Effect of Escapes and Grounds upon the Circuit 63 
 
 The Laws of the Electric Current 64 
 
 Practical Application of Ohm's Law 65
 
 CONTENTS. YJ 
 
 PAOB. 
 
 Distribution of Batter7 Power 70 
 
 Working Several Lines from One Battery 71 
 
 CHAPTER VI. 
 
 TESTING TELEGRAPH LIKES. 
 
 Interruptions to which Telegraph Lines are Liable 73 
 
 Testing for Disconnection 74 
 
 Partial Disconnection 75 
 
 To Test for an Escape 75 
 
 Testing for Grounds 76 
 
 Testing for Crosses 76 
 
 Testing with the Galvanometer and Resistance Coils. 78 
 
 Testing for the Distance of Faults 80 
 
 The Loop Test 81 
 
 Blavier's Formula for Locating an Escape 84 
 
 To Find the Distance of a Cross. 85 
 
 Advantages of Testing by Measurement 86 
 
 Testing for Conductivity Resistance 87 
 
 CHAPTER VII. 
 
 NOTES ON TELEGRAPHIC CONSTRUCTION. 
 
 Poles 89 
 
 "Wire 89 
 
 Galvanized Wire 90 
 
 Arrangement of Wires upon the Pole. 90 
 
 Joints or Splices 90 
 
 Fixing the Insulators 91 
 
 Leading Wires into Offices 92 
 
 Fitting up Offices 93 
 
 Ground Connections 93 
 
 Cables 93 
 
 Making Joints in Cables 94 
 
 CHAPTER VIII. 
 
 HINTS TO LEARNERS. 
 
 Formation of the Morse Alphabet 96 
 
 Elementary Principles of the Alphabet 97 
 
 Exercises for Practice in Sending 99 
 
 The Alphabet and Numerals 101 
 
 Beading by Sound 102
 
 Vlll CONTENTS. 
 
 CHAPTER IX. 
 
 BECENT IMPROVEMENTS IN TELEGBAPHIC PBACTICE. 
 
 The American Compound Wire 104 
 
 The Gravity Battery 106 
 
 Siemens' Universal Galvanometer 108 
 
 Pope and Edison's Printing Telegraph 112 
 
 CHAPTER X. 
 
 APPENDIX AND NOTES. 
 
 The Equipment of Telegraph Lines 116 
 
 The Working Capacity of Telegraph Lines 121 
 
 The Electrical Tension of Telegraph Batteries and Lines 1 24 
 
 Double Transmission 131 
 
 Edison's Button Eepeater 134 
 
 Bradley's Tangent Galvanometer 135 
 
 Thompson's Reflecting Galvanometer 137 
 
 Mode of Working the Atlantic Cable 141 
 
 Velocity of Electric Signals 144 
 
 Speed of Transmission 145 
 
 Comparison of Wire Gauges 146 
 
 Useful Formula for Weight and Resistance of Wires 147 
 
 Conducting Powers of Materials 147 
 
 Internal Resistance of Batteries 149 
 
 Electro-motive Force of Different Batteries 150 
 
 Measurement of Electro-motive Force 151 
 
 Forces of Electro-magnets 151 
 
 Electrical Formulae 152 
 
 Ohm's Law 152 
 
 Parallel or Derived Circuits 153 
 
 Galvanometers and Shunts 153 
 
 Formula for the Loop Test 153 
 
 Blavier's Formula for Locating a Fault 154 
 
 Measures of Resistance 154 
 
 Strain of Suspended Wires 154 
 
 Index 157
 
 MODERN PEACTICE 
 
 or THS 
 
 ELECTRIC TELEGRAPH. 
 
 CHAPTER I. 
 
 ORIGIN OP THE ELECTRIC CURRENT. GALVANIC BATTERIES. 
 
 1. SIMPLE GALVANIC CIRCUIT. If two plates of dif- 
 ferent metals, such as copper and zinc for example, are 
 immersed in a vessel of water to which a small portion 
 of sulphuric acid has been added, and the upper ends of 
 the two plates are brought in contact, or connected 
 together with a metallic wire as in fig. 1, a, continuous 
 
 current of electricity will pass from the copper to the 
 zinc through the connecting wire, and from the zinc to 
 the copper through the liquid, as indicated by the 
 arrows in the figure. If the metallic communication be 
 interrupted, or the circuit, as it is termed, broken, the 
 current at once ceases, but is instantly renewed when- 
 ever the connection is again formed. Electricity pro- 
 duced by this means is usually termed Galvanic or Vol- 
 taic electricity, from the names of its discoverers, and 
 is the effect of chemical action by the acidulated water 
 upon the zinc.
 
 I MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 2. The plate (usually of zinc), upon the surface of 
 Which the electricity is generated by chemical action, is 
 called the negative pole, and the opposite plate, gen- 
 erally of copper, platina or carbon, is called the posi- 
 tive pole. They are also frequently designated by the 
 signs (minus) and + (plus). 
 
 3. If both metals in this arrangement were equally 
 acted upon by the solution, no electricity would be pro- 
 duced, as this effect arises in all cases from the differ- 
 ence in the chemical action upon the two plates. For 
 this reason the positive plate is made of some metal or 
 other substance upon which the liquid has little or no 
 effect. 
 
 4. The apparatus for producing voltaic electricity, 
 which has been described in its simplest form, is called 
 a battery. As electricity is produced under any circum- 
 stances in which the above conditions have been com- 
 plied with, there are various methods of constructing 
 a battery. The forms used in the practical operation 
 of the telegraph will hereafter be described in detail. 
 
 5. CONDUCTORS AND NON-CONDUCTORS. Some sub- 
 stances, such as metals, possess the property of allow- 
 ing electricity to diffuse itself freely throughout their 
 whole substance, and are therefore termed conductors. 
 Others, such as glass, hard rubber, and dry wood, offer 
 great resistance or opposition to this diffusion, and are 
 called non-conductors or insulators. 
 
 6. This division however is relative and not abso- 
 lute. Few if any bodies are perfect insulators, and 
 even metals, the most perfect of all conductors, offer 
 some resistance to the passage of electricity, or in other 
 words insulate slightly. A good insulator, therefore, 
 is simply a bad conductor, and vice versa. 
 
 7. In the following list each substance named con- 
 ducts better than that which precedes it, the first being 
 the best insulator and the last the best conductor : 
 
 1. Dry Air, 5. India Rubber, 9. Silk, 
 
 2. Paraffine, 6. Gutta Percha, 10. Dry Paper, 
 
 3. Hard Rubber, 7. Sulphur, 11. Porcelain, 
 *. Shellac, 8. Glass, 12. Dry Wood,
 
 GALVANIC BATTERIES. 11 
 
 13. Dry Ice, 18. Mercury, 23. Zinc, 
 
 14. Water, 19. Lead, 24. Gold, 
 
 15. Saline Solutions, 20. Tin, 25. Copper, 
 
 16. Acids, 21. Iron, 26. Silver. 
 
 17. Charcoal or Coke, 22. Platinum, 
 
 8. ELECTRICAL TENSION. If two or more simple bat- 
 teries, or elements as they are called, are connected to- 
 gether in such a manner that the positive plate of the 
 lirst is united by a metallic conductor with the negative 
 plate of the second, and so on, as shown in fig. 2, the 
 
 electrical tension, or power of overcoming resistance, is 
 increased in direct proportion to the number of ele- 
 ments. Four elements will therefore possess four times 
 the tension of one element, and the current generated 
 by their combined action will be capable of overcoming 
 four times the resistance of that from a single element. 
 9. ELECTRICAL QUANTITY. It is important, however, 
 to observe, that although the tension increases with 
 each element added to the series, no greater quantity is 
 produced by a great number of elements than by a 
 single one the action in each cell serving only, as it 
 were, to urge forward a quantity equal to that arising 
 from chemical decomposition in the first cell. If, on the 
 contrary, we connect together the four zincs and the 
 four coppers, forming in effect a single element, with 
 plates equivalent to four times the original surface, 
 there will be four times the original quantity of electri- 
 city generated ; but its tension, or power of overcom- 
 ing resistance, will be no greater than that of a single 
 pair of plates. This distinction is of great importance,
 
 12 
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 and should be thoroughly understood and carefully re- 
 membered. 
 
 10. In the simple form of battery previously described 
 (8), if the poles are united by a conductor for a consider- 
 able length of time, bubbles of hydrogen, arising from 
 the decomposition of the water, cover the positive plate, 
 and in a great measure prevent the liquid from coming 
 in contact with it, and the surface of the plate also be- 
 comes coated with a deposit of zinc, tending to convert 
 the battery into one in which both plates are of zinc, 
 and thus its electro-motive force is weakened and finally 
 destroyed. In order to render the battery constant in 
 its action, it is necessary to prevent these effects by 
 surrounding the negative plate with a solution of a salt 
 of the metal itself. This principle is employed in the 
 arrangement about to be described. 
 
 11. THE DANIELL BATTERY. This combination con- 
 sists of a jar of glass or earthenware, F (fig. 3), about six
 
 GALVANIC BATTERIES. 
 
 inches in diameter and eight or nine inches high. A 
 plate of copper, G, is bent into a cylindrical form, so as 
 to fit within it, and is provided with a perforated cham- 
 ber, to contain a supply of sulphate of copper in crys- 
 tals, and a strap of the same metal with a clamp for 
 connecting it to the zinc of the next element. H is a 
 porous cup, as it is technically termed, made of unglazed 
 earthenware, six or seven inches high and two inches in 
 diameter, within which is placed the zinc, X. This is 
 usually of the shape shown in the figure, which is called 
 the "star zinc," but it is often made in the form of a 
 hollow cylinder, the latter giving greater power, but 
 being somewhat more difficult to clean. 
 
 The outer cell is filled with a saturated solution of 
 sulphate of copper (blue vitriol), and the porous cell 
 with a solution of sulphate of zinc. A series of three 
 elements connected together, as usually employed on 
 American lines for a local battery, is shown at I. 
 
 12. EFFECT OF CONTINUED ACTION. By continued 
 action sulphate of zinc is formed in the porous cup, and 
 the sulphate of copper in the outer cell consumed, the zinc 
 being constantly dissolved away while the copper plate 
 is at the same time increased. When all the sulphate 
 of copper has been decomposed, and the water in the 
 zinc compartment saturated with sulphate of zinc, the 
 action of the battery ceases. Some of the sulphate of 
 zinc in this case usually passes into the copper cell, and 
 appears upon the copper plate in the form of a black 
 powder ; it is therefore necessary to maintain a con- 
 stant supply of pulverized vitriol in the perforated 
 chamber attached to the copper cylinder. 
 
 13. When the solution in the porous cup becomes satu- 
 rated with sulphate of zinc it crystallizes upon the zinc 
 plate, interfering with the action of the battery. Part 
 of this solution should therefore be removed occasion- 
 ally and replaced with water. 
 
 In setting up the battery pure water may be used in 
 the porous cell, and the battery allowed to stand a few 
 hours with a closed circuit, when it will be found
 
 14 MODERN PRACTICE OF THE ELECTRIC TEIEGRAPH. 
 
 ready for use. The addition of a little sulphate of zinc 
 will greatly hasten its action. 
 
 14. THE DEPOSIT OF COPPER UPON THE POROUS CUP. 
 This cannot be entirely prevented, but may be greatly 
 lessened by suspending the zinc so that it will not touch 
 the porous cup below the surface of the liquid, and by 
 saturating the bottom of the cell to the height of half 
 an inch with melted paraffine, or even tallow. 
 
 15. When constructed as above described and used 
 in a local circuit, the Daniell batter}-- will continue in 
 action about ten or fifteen days without attention, the 
 time depending upon the size of the wire in the magnet 
 and the amount of daily service. The sulphate of cop- 
 per solution should be kept of good strength, otherwise 
 the upper portion becomes weak and an extra current 
 is set up within the battery, which tends to eat away 
 and destroy the copper plate without any useful effect. 
 
 16. RENEWAL OP THE BATTERY. In renewing this 
 battery the zincs should be scraped and well cleaned 
 with a stiff brush, the porous cups thoroughly washed, 
 and the old solution contained in them thrown out, with 
 the exception of about one third of the clear portion, 
 which should be returned, otherwise the battery will 
 require some hours to recover its full strength. The 
 copper deposit upon the zincs is valuable, and should be 
 preserved. 
 
 Every two or three months the coppers ought to be 
 taken out and the deposit upon their surface removed, 
 which may be done two or three times. When they 
 become too much encrusted to afford room for the po- 
 rous cups they must be replaced by new ones. 
 
 Porous cups ought to be renewed whenever they be- 
 come too much encrusted with copper. If cracked they 
 should be changed at once, otherwise a great waste of 
 material will ensue. 
 
 17. The crystals which form around the edge of the 
 outer jar require to be occasionally wiped off with a 
 damp cloth, or they will eventually run down the out- 
 side and form a connection between the jars, giving rise
 
 GALVANIC BATTERIES. 
 
 15 
 
 to a great consumption of material without correspond- 
 ing benefit. 
 
 18. In order that the current may act with its full 
 force, it is necessary to keep the clamps and connec- 
 tions of the battery clean and bright, and free from rust 
 or dirt. As chemical action is promoted by heat, the 
 battery will act more vigorously if kept in a warm 
 place. 
 
 19. APPLICATION OP THE DANIELL BATTERY TO MAIN 
 CIRCUITS. This battery is sometimes used for main 
 circuits, but in that case it is preferable to arrange it 
 differently by placing the zincs outside and the copper 
 within the porous cell, as in fig. 4, in which Z shows the 
 
 zinc and P the porous cell. The copper, C, is provided 
 with a perforated shelf, D, upon which the vitriol is 
 placed. 
 
 Other forms have been devised which dispense en- 
 tirely with the porous cup, the two solutions being sepa- 
 rated by the difference in their respective specific grav- 
 ities. Some of these bid fair to come into extensive 
 use. 
 
 20. THE GROVE BATTERY. The most intense and 
 powerful voltaic combination that has yet been dis- 
 covered is that of Grove. For many years it was ex- 
 clusively used for telegraphic purposes in this country, 
 and is still employed in that capacity to a considerable 
 extent. Its component parts are shown in fig. 5, in 
 which A represents a glass jar or tumbler, about 3
 
 1 6 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 inches in diameter and 4 inches high. A thick cylin- 
 der of zinc, B, of a size nearly sufficient to fill the tum- 
 bler, is placed within it, and is furnished with a project- 
 ing arm, to which is attached the positive plate of the 
 next element. The porous cup, C, is placed within the 
 zinc. A thin strip of platina, D, about 2<z inches long 
 and half an inch in width, is soldered to the end of the 
 zinc arm projecting from the adjacent cell, and reaches 
 nearly to the bottom of the porous cup. 
 
 21. SETTING UP A GROVE BATTERY. It is necessary 
 that the zinc should first be thoroughly amalgamated. 
 The ordinary zinc of commerce contains particles of lead, 
 iron, and other impurities, which, when the plate is im- 
 mersed in dilute acid, form as it were small batteries 
 upon the surface, which eat away numerous cavities in 
 the zinc without producing any useful effect. This is 
 termed local action, and may be, in a great measure, 
 prevented by the above process of amalgamation, which 
 is usually performed by immersing the zincs in a vessel 
 containing dilute muriatic or sulphuric acid, and then 
 plunging them in a bath of metallic mercury. After 
 remaining in this for a minute or two they are taken
 
 GALVANIC BATTERIES. 
 
 17 
 
 out and placed in a vat of clean water, where the su- 
 perfluous mercury is allowed to drain off. The mercury 
 dissolves a little of the zinc, which flows over and covers 
 the impurities, and prevents the acid solution from 
 coming in contact with them. 
 
 22. In putting the Grove battery together, first place 
 the glass tumblers in position and fill them about half 
 full of a solution composed of one part of sulphuric acid 
 and twenty to thirty parts water, by measure, thoroughly 
 mixed. Then place the amalgamated zincs in the 
 tumblers, with the arms turned at right angles to the 
 line of cells. Fill the porous cups nearly full of strong 
 nitric acid and place them within the zincs, then turn 
 the zincs around so as to immerse the platina strips in 
 the nitric acid of the adjoining cell, throughout the 
 whole series, as shown at T, in tig. 5. 
 
 23. The strength of the dilute sulphuric acid solu- 
 tion in this battery should be varied in proportion to 
 the number of wires worked from it. The less the num- 
 ber of the latter the weaker the solution may be made. 
 
 24. When in continuous service a Grove battery 
 ought to be taken apart every night, and the nitric acid 
 from the porous cups emptied into a vessel and kept 
 closed until morning. The zincs should be removed 
 and placed inverted in a trough of water, acidulated 
 with sulphuric acid, and in the morning rubbed with a 
 brush, and the mercury diffused evenly over their sur- 
 faces. To every ten parts of the nitric acid taken from 
 the battery add one part of fresh acid every morning. 
 By this means a steady and uniform current will be 
 maintained when the battery is in action. The dilute 
 sulphuric acid requires renewal about twice a week. In 
 handling this battery great care is required not to injure 
 the connection between the zinc and the platina. A set 
 of Grove zincs, in continuous service, will require re- 
 newal about once in three months. 
 
 25. THE CARBON BATTERY. This is a modification of 
 the Grove battery, and is sometimes called the Electrp- 
 poion battery. It is extensively employed on the Ame-
 
 1 g MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 rican lines for main circuits. In its general construction 
 and arrangement it differs but little from the battery 
 last described. The different parts of which it is com- 
 posed are shown in fig. 6, consisting of a glass tum- 
 bler, zinc and porous cup. In place of the platina of 
 the Grove battery, a plate of carbon or coke is em- 
 ployed for the positive element, as shown in the figure. 
 
 A clamp is arranged so as to press a platina button 
 firmly against the carbon, this button being permanently 
 attached to a wire leading to a binding screw on the 
 zinc arm of the next element. The parts are usually 
 made of about the same size as in the Grove battery. 
 
 The carbon connection is sometimes made by means 
 of a platinized copper wire inserted into its upper end, 
 and surrounded with lead, to prevent the action of the 
 acids upon the copper. 
 
 26. In setting up this battery the different parts
 
 GALVANIC BATTERIES. 
 
 should be put together in the position they are to oc- 
 cupy, as shown in fig. 6, and care taken that all the con- 
 nections are firmly screwed up. The zincs must be 
 thoroughly amalgamated, and the dilute sulphuric acid 
 solution mixed as directed for the Grove battery. A 
 sufficient quantity of this solution is poured into the 
 tumblers to cover the cj'lindrical portion of the zincs. 
 The porous cups are then filled with a solution of bi- 
 chromate of potash,* care being taken not to pour it 
 upon the connections or clamps. 
 
 27. When the battery is in service, one third of the 
 bi-chromate solution in the porous cups should be re- 
 moved every morning by means of a large rubber sy- 
 ringe, and replaced with fresh. A new set of zincs will 
 require to be amalgamated a second time after having' 
 been in use three or four days ; after which once in two 
 to four weeks will be often enough depending some- 
 what upon the amount of work required from the bat- 
 tery. The battery ought to be taken apart every two 
 weeks, the zincs brushed, the dilute sulphuric acid solu- 
 tion renewed, and the carbons thoroughly soaked in 
 clean water. It is better, if possible, to have a spare 
 set of cells complete, so that one may be renewed while 
 the other is in use. 
 
 28. POWER OF THE CARBON BATTERY. This is quite 
 equal to that of the Grove, as far as the intensity of its 
 action is concerned. The latter however will work 
 nearly twice as many wires at the same time as the 
 former. The expense of the carbon battery for mate- 
 rials and attendance is less than one third that of the 
 Grove. A set of zincs, if properly cared for, will last 
 from fourteen to sixteen months on an ordinary tele- 
 graph line. It is a good plan to coat the zincs with as- 
 phaltum varnish at the junction of the projecting arm, 
 as these are frequently eaten off while the rest of the 
 zinc remains in good condition. 
 
 * This solution is made as follows : Mix one gallon of sulphuric acid and three 
 gallons of water. Then, in a separate vessel, dissolve five Ibs. bi-chromate of pot- 
 ash in two gallons of boiling water and add to the above, mixing the whole thor- 
 oughly together. The proportion of bi-chromate is sometimes made one fifth greater 
 than the amount giveu.
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 . 29. INSULATION OF BATTERIES. The cells of a bat- 
 tery should always be thoroughly insulated from each 
 other. This is especially important in the case of the 
 Grove battery. A convenient and 
 effective mode of insulation is shown 
 in fig. 7, in which the battery tum- 
 blers, AA, are set upon hollow cy- 
 linders of wood, BB, saturated with 
 asphaltum or paraffine, and insulated 
 from the upright wooden pins, DD, by 
 the glass sockets, CO. The pins are 
 FIG. 7. inserted into a horizontal scantling, 
 
 E, which forms the top of the battery stand. 
 " Battery jars, of different sizes, are now made at the 
 Brooks Paraffine Insulator Works, in Philadelphia, which 
 are composed of stone-ware, thoroughly saturated with 
 paraffine, so that moisture will not penetrate them, nor 
 remain upon their surface. When these jars are em- 
 ployed, no special insulation is required.
 
 CHAPTER II. 
 
 ELECTRO-MAGNETISM. 
 
 30. WHENEVER the poles of a battery are connected 
 by a conductor, or series of conductors, so as to form a 
 circuit, a current of electricity is assumed to flow from 
 the negative to the positive pole, through the battery 
 itself, and from the positive to the negative pole through 
 the conductor. 
 
 31. If the conducting wire is covered with an insu- 
 lator (5), such as silk or cotton, so as to compel the 
 current to traverse its entire length, and is wound into a 
 spiral or coil, surrounding a magnetic needle, the needle 
 will be deflected from its natural position, and will tend 
 to take up a position at right angles to the direction of 
 the current. If the current be passed in the opposite 
 direction through the wire, the deflection of the needle 
 will also take place in the opposite direction. The Gal- 
 vanometer, an extremely useful instrument for the pur- 
 pose of indicating the presence, direction, and strength" 
 of a voltaic current, is constructed upon this principle. 
 
 32. If the conducting wire, covered as above, be 
 wound upon a bar of soft iron, the iron becomes mag- 
 netic as long as the current continues to flow, and pos- 
 sesses the property of attracting other pieces of iron iii 
 its vicinity. This arrangement is called an electro- 
 magnet. (34.) 
 
 33. If the iron is very soft and pure it loses its mag- 
 netism instantly upon the cessation of the current, but 
 if impure, or if hardened by hammering or turning, it 
 retains a certain amount of residuary magnetism, espe- 
 cially after it has been acted upon by a powerful cur- 
 rent. It is, therefore, necessary that the iron cores, as 
 they are termed, of electro-magnets, should be annealed 
 with great care.
 
 22 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 34. ELECTRO-MAGXETS are generally made in a U 
 form, two bobbins or spools, a a (fig. 8), being filled 
 
 with covered copper wire, and the 
 soft iron cores, c c, passing through 
 them, fixed upon a connecting bar, 
 | b, also of soft iron, as shown in the 
 figure. The two spools, a and a. are 
 virtually continuations of one spool, 
 the direction being apparently re- 
 versed by the bend of the U- The 
 ends of the cores, c c, opposite to the connecting bar, 
 are called the poles of the magnet, the magnetic force 
 being accumulated at these points. The bar of soft 
 iron, d, upon which the magnet exerts its force, is called 
 'the armature. 
 
 35. In electro-magnets and galvanometers the mag- 
 netic effect of the current is multiplied by the number 
 of convolutions of the wire in the coil, but it is dimin- 
 ished in proportion to the distance of the wire from the 
 core, each layer of wire acting with less power than the 
 one beneath it. 
 
 36. Every addition to the length of the conducting 
 wire enfeebles the current, because of the increased re- 
 sistance (5, 6,) it offers to its passage. In a very long 
 circuit, such as a telegraph line, the action of the cur- 
 rent will necessarily be feeble, and the coil is, there- 
 jfore, made of/we wire, which occupies little space, and 
 allows many layers to be wound on without too greatly 
 increasing the distance from the cores, while its resist- 
 ance is too small in proportion to the rest of the cir-r 
 cuit to reduce the strength of the current materially. 
 
 37. When, however, the circuit is very short, coarser 
 wire is employed in the coil. A fine wire would add 
 to the resistance of the circuit more than would bq 
 made up by the effect of an increased number of turns, 
 for even a very few layers would double the resistance 
 pf the circuit. 
 
 The former is frequently called an intensity, and the 
 latter a quantity magnet*
 
 ELECTRO-MAGNETISM. . 23 
 
 38. Iron docs not acquire its full magnetism instan- 
 taneousl}', and the act of demagnetization also requires 
 time, but is effected more rapidly than magnetization. 
 The greater the tension of the battery the more rapidly 
 the iron acquires its magnetism ; therefore, if very 
 rapid action is required, even on a short circuit, a num- 
 ber of cells of battery must be used. 
 
 It has also been ascertained by experiment that an 
 electro-magnet with short cores, will acquire and lose 
 its magnetism with much greater rapidity than one with 
 long cores, but in other respects similar.
 
 CHAPTER III. 
 
 TELEGRAPHIC CIRCUITS. 
 
 39. A TELEGRAPHIC CIRCUIT consists of one or more 
 batteries, the line wire, the instruments and the earth. 
 When the circuit is very short a return wire is fre- 
 quently used instead of the earth. 
 
 40. Owing to the immense rapidity with which the 
 electric force is propagated throughout a circuit, any 
 effect which can be produced at hand can be produced 
 in any other part of a circuit, however distant, at the 
 same instant of time, subject to a diminution of force, 
 arising from causes which diminish the quantity of elec- 
 tricity, or the force of the current before its arrival at 
 the distant end, thus weakening its effect. The princi- 
 pal causes of this diminution are the resistance of the 
 circuit and defective insulation, in consequence of which 
 a portion of the current escapes from the line to the 
 earth, and returns without traversing the distant por- 
 tion of the circuit. 
 
 41. The effective force of the current leaving the bat- 
 tery depends upon two things the tension of the bat- 
 tery, which sets the current in circulation, and the 
 resistance the current encounters in traversing the cir- 
 cuit. 
 
 42. RESISTANCE OF THE CIRCUIT. This depends upon 
 the length and size of the conductor, and the material 
 of which it is composed. In an ordinary telegraphic 
 line wire the resistance is in direct proportion to its 
 length, arid also in inverse proportion to its weight per 
 mile. Thus, 150 miles of No. 8 wire will conduct as 
 well as 100 miles of No. 10 wire, and as great an effect 
 can be produced at its remote end with a battery of 
 equal tension. There is, therefore, a great advantage
 
 TELEGRAPHIC CIRCUITS. 25 
 
 in using the larger sizes of wire in the construction of 
 lines intended to be worked in long circuits. 
 
 43. ELECTRICAL MEASUREMENT. In order to institute 
 a comparison between the resistances of different cir- 
 cuits, etc., a standard has been fixed upon by the Brit- 
 ish Association, called the Ohm, which is equivalent to 
 about -rV of a mile of galvanized No. 9 iron wire, such 
 as is usually employed in the construction of telegraph 
 lines. This standard unit of resistance is now made use 
 of by the English electricians. 
 
 44. EESISTAXCE COILS. As no battery is constant in 
 its power, and no magnet uniform in its strength, neither 
 of these can be made use of as an accurate basis of com* 
 parison. Resistance coils, composed of wire of certain 
 alloys of metals, carefully prepared, have been found 
 not to vary T <r<nhnnr in eight years. The only variation 
 is that due to difference in temperature, which may be 
 readily calculated and allowed for when necessary. 
 
 It will, therefore, be understood that the ohm is a unit 
 of resistance in the same manner that an inch is a unit 
 of length, or a pound a unit of weight. 
 
 45. A TELEGRAPHIC CIRCUIT, in its simplest form, is 
 shown in fig. 9. A and B represent two stations. The 
 circuit may be traced as follows : From the + pole of 
 the battery E to the key K (52) and electro-magnet M, 
 thence through the line L to the other station, electro- 
 magnet M' and key K' to the earth at G', and thence 
 through the earth, as represented by the dotted line, to 
 the pole of the battery E. A continuous current will
 
 26 
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 therefore flow through the circuit as long as it remains 
 uninterrupted, and the armatures of the electro-magnets 
 M and M' will be attracted by the cores, but if the cir- 
 cuit be broken by means of one of the keys, K or K', 
 both electro-magnets will be demagnetized. Thus, the 
 breaking of the circuit at either station affects the elec- 
 tro-magnets of both, as they are in the same circuit. 
 
 46. THE EARTH CIRCUIT. In thus using the earth as 
 part of the circuit, it is found that it offers, practically, 
 no resistance to the passage of the current. Although 
 comparatively a poor conductor, it is an infinitely large 
 one in proportion to the wire, and, therefore, its resis- 
 tance is not appreciable (42). 
 
 47. ARRANGEMENT OF BATTERIES. In practice it is 
 usual to divide the battery E into two parts, placing 
 half at each end of the line, for reasons which will 
 hereafter appear. It is important, however, when this 
 is done, that the positive pole of one battery should 
 be connected with the negative pole of the other, other- 
 wise they would neutralize each other, and no effect 
 would be obtained. In such a case the batteries are 
 said to be reversed. 
 
 48. INTERMEDIATE STATIONS. It is evident that in- 
 termediate stations may be introduced at any point 
 upon the line shown in the above figure, each being 
 provided with an electro-magnet and key, forming part 
 of the circuit, and that the breaking and closing of the 
 circuit at any of these points will affect all the electro- 
 magnets through which it passes, in the same manner 
 and at the same instant of time. 
 
 Any desired number of intermediate stations may 
 be placed upon a line until the combined resistance of 
 their electro-magnets reduces the strength of the cur- 
 rent below that required for the convenient working of 
 the circuit. 
 
 49. THE MORSE SYSTEM. The principle of the Morse 
 system of telegraphy consists in conveying arbitrary 
 signals by means of the magnetization and demagneti- 
 zation of an electro-magnet, by the alternate breaking
 
 TELEGRAPHIC CIRCUITS. 
 
 and closing of a voltaic circuit in the manner above ex- 
 plained. The conventional alphabet used in America 
 for this purpose is given in another part of this work. 
 
 50. OTHER TELEGRAPHIC SYSTEMS. The type print- 
 ing telegraph, employing the " Combination" instrument 
 of Phclps, is the only system other than the Morse now 
 in use upon the public lines in the United States. The 
 limited extent to which it is employed renders it unneces- 
 sary to give a detailed description of its construction 
 and mode of operation in a work of this kind. The 
 electro-chemical telegraph of Bain, and the beautiful 
 type-printing instruments of House and Hughes, were 
 formerly extensively employed in this country. The 
 former has now given place to the Morse, while the two 
 latter have been superseded by the equally rapid and 
 more simple and effective instrument of Phelps. 
 
 In addition to these, the magneto-electric dial instru- 
 ment of Edmands & Hamblet, and the electro-magnetic 
 alphabetical instrument of Chester are finding exten- 
 sive employment upon private lines, where extreme 
 rapidity of transmission is not required, thus rendering 
 the employment of skilled operators in such cases un- 
 necessary.
 
 CHAPTER IY. 
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 
 
 51. THE Morse Telegraphic Apparatus consists of a 
 signal key for breaking and closing the circuit, and an 
 electro-magnet, the armature of which is attached to a 
 lever carrying a steel point or stvle, which embosses a 
 mark upon a narrow strip of paper, moved uniformly 
 along by clock-work. As long as a current continues 
 to flow through the coils of the electro-magnet the 
 armature is attracted, and a mark is made upon the 
 moving paper. As soon as the circuit is broken the 
 armature ceases to be attracted, and is withdrawn from 
 contact with the paper by means of a spring. The 
 duration of the current, and consequently the length of 
 the mark, depends upon the duration of the contact made 
 by the key. 
 
 Fio. 10. 
 
 52. THE MORSE SIGXAL KEY is shown in fig. 10.* It 
 consists of a brass lever, A, four or five inches in length, 
 which is hung upon a steel arbor, G, between adjustable 
 set screws, I) 1), in such a manner as to allow it ta 
 move freely in a vertical direction. This movement, 
 however, is limited in one direction by the anvil C, and 
 in the other by the adjustable set-screw, F. 
 
 * The drawings of the signal key, register and relay (figs. 10, 11 and 12), are from 
 instruments manufactured by Bradley.
 
 THK MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 29 
 
 One wire of the main circuit is connected to the 
 metallic frame of the key, and the other to the anvil, C, 
 which is insulated from the frame. These connections 
 arc made by screws passing up through the table from 
 beneath. The lever is provided with a knob of vulcan- 
 ite, B, by means of which it may be pressed down by 
 the finger of the operator, bringing the lever in contact 
 with the anvil, and thus closing the circuit, precisely as 
 if the wires themselves had been brought together. The 
 points of contact between the lever and the anvil are 
 made of platina, as ordinary metals would be fused by 
 the passage of the electric spark when the circuit is 
 broken. A spring beneath the lever restores it to its 
 original position when the pressure of the operator's 
 finger is withdrawn. When the key is not in use the 
 circuit is completed by bringing the lever of the cir- 
 cuit closer, H, into contact with the anvil, C. 
 
 FlQ/ll. 
 
 53. THE MORSE REGISTER. Fig. 11 represents the 
 recording apparatus, usually termed a register, which is 
 made in several different forms, all involving the same 
 principles. M is. the electro-magnet, the two ends of 
 the wire forming the coils fyeing carried to the terminal 
 binding screws on the base\ one of which is shown at 
 s, to which the conducting wires are attached. Above 
 the electro-magnet is seen the, % armature attached to 
 the lever L, which moves upon an.arbor at d. The op- 
 posite extremity of the lever carries a steel point, p.
 
 3(j If ODZRX PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 The strip of paper passes through the guide g and be- 
 tween the grooved rollers r r, which are moved by 
 a train of wheels driven by a weight attached by a cord 
 to the drum, W. 
 
 When the armature is attracted by the magnet the 
 style p is brought forcibly in contact with the paper, 
 moving above it upon the grooved roller, and a raised 
 line is embossed upon it corresponding in length to the 
 time the armature remains attracted. A spring ad- 
 justed by the nut n withdraws the lever when the at- 
 traction ceases. The movement of the lever is limited 
 by the adjustable screw, m. The screw c regulates the 
 pressure of the rollers upon the paper, and the clock- 
 work is started and stopped by the brake a. The 
 weight is wound up occasionally, as required, by the 
 operator. 
 
 54. The Morse instrument is worked either by the 
 main line current or \>y relay. For a distance not ex- 
 ceeding 20 or 30 miles, a register, whose coils are 
 wound with No. 30 copper wire, may be worked by the 
 line current, if the line be well insulated (57). 
 
 55. When the insulation is defective, or the circuit 
 so long that its resistance renders the current too weak 
 to work a register direct, as is usually the case with 
 telegraph lines, it becomes necessary to employ a re- 
 ceiving magnet or relay, which brings a local battery 
 (11) into action at the receiving station, the current of 
 which operates the register. 
 
 FIG. 12. 
 
 56. THE RELAY MAGNET. The construction of the 
 relay is shown in fig. 12. M is the electro-magnet,
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. [. 
 
 which is placed in a horizontal position, and is movable 
 by means of the screw a. The coils of the magnet are 
 of fine wire, usually from No. 30 to No. 36 in size, of 
 great length and closely wound.* The ends are con- 
 nected to the line circuit by the binding screws, m m'. 
 The armature lever b is connected with the binding 
 screw / by a wire carried underneath the base of the 
 instrument. A platina point, c, on the armature lever, 
 is brought in contact with a similar point on the end of 
 the screw d whenever the armature is attracted by 
 the magnet, the screw being in metallic connection with 
 the binding screw /', by means of the frame of the appa- 
 ratus and a wire beneath the base. One of the screws, 
 1 1', is connected to one pole of the local battery (11), 
 and the other to the other pole, embracing the register 
 magnet in its circuit. Therefore, whenever the arma- 
 ture is attracted by the force of the main current acting 
 upon the relay magnet, the circuit of the local battery 
 is completed through the register, As the relay is con- 
 structed with great delicacy, a feeble line current is 
 enabled to actuate a register powerfully through the 
 intervention of a local battery. 
 
 The movement of the armature is regulated to corres- 
 pond with the varying strength of the line current by 
 means of the adjustable spiral spring /. The magnet 
 may be also set at any required distance from the arma- 
 ture by means of the screw a, which is cut with a right 
 and left hand thread, passing through the soft iron bar 
 connecting the two cores, and also through the support- 
 ing post in the rear of the coils. The latter slide through 
 openings in the upright metallic plate which, supports 
 the adjustable platina pointed screw d. 
 
 * In tho instruments manufactured by Dr. Bradley the helices or coils of the 
 electro-magnets, instead of being composed of silk insulated copper wire, as de- 
 scribed in 34, are made of naked wire, ingeniously wound by accurate machinery 
 in such a manner that the convolutions are separated from each other by a space 
 of 1-600 to 1-SOO of an inch, the several layers being insulated frorn. each other by 
 thin paper. It is claimed that, by this method of winding, a coil cf a given length 
 nnd g;iUe of wire, and, consequently, of a given resistance, can be made of much 
 less diameter than is possible with silk insulated wire, while, at the same time, the 
 number of convolutions will bo increased as well as the power of the electro-
 
 32 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 Fig. 13 represents a Pocket Relay, as it is usually 
 termed, although it is properly a main line sounder (57). 
 
 This is provided with a key, as shown in the figure, the 
 whole being conveniently and compactly arranged to fit 
 into an oval case four or five inches long, which may be 
 carried in the pocket It is an extremely convenient 
 apparatus for line repairers. The cut shows the ar- 
 rangement manufactured by the Messrs. Chester. 
 
 FIG. 14. 
 
 67. THE SOUNDER. In many of the larger telegraph 
 offices the recording apparatus is dispensed with, and 
 the communications read by the sound of the armature 
 lever. In that case the Sounder (fig. 14) is employed in 
 the place of the register, the connections of the wires 
 being arranged in precisely the same manner. The 
 Sounder consists simply of the electro-magnet, arma-
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 33 
 
 ture and lever, fixed upon a base.* The coils are usu- 
 ally wound with ]S T o. 23 wire. 
 
 Main Line Sounders are used in some offices, which 
 enables the operator to dispense with the local battery. 
 The coils are wound with line wire, usually No. 80, and 
 are frequently made somewhat larger than those of the 
 relay. A common form of this instrument is known as 
 the "Box Sounder." The lever, striking upon a hollow 
 wooden box containing the magnet, gives a sound that 
 may easily be distinguished by the operator under ordi- 
 nary circumstances. 
 
 Fig. 15 (8. F. Day & Co.) shows an excellent form of 
 Main Line Sounder. The parts of the instrument are 
 mounted upon a metallic plate, the centre of which is 
 raised slightly above the base, so as to form a bridge, as 
 shown in the cut. The armature lever is of steel, and 
 the whole arrangement is well adapted to increase the 
 sound of the lever as much as possible a feature of great 
 value in working with weak currents or on badly insu- 
 lated lines. These instruments are also made in seve- 
 ral other forms, and various devices for increasing the 
 sound of the lever arc made use of. On many lines 
 they are found to answer as well as the usual arrange- 
 ment, employing a relay and local battery. 
 
 * The instrument shown in the figure is from the manufactorj of C. T. & J. N. 
 Chester. 3 ~; ."*K
 
 34 
 
 MODERN PRACTICE OF THE ELECTRIC TELE.GRAPH. 
 
 For circuits of moderate length a Main Line Register 
 (fig 16), manufactured by Day & Co., has been employed 
 with excellent results. 
 
 58. ARRANGEMENT OF A TERMINAL STATION. Fig. 17 
 is a diagram showing the arrangement of wires, batteries, 
 
 Fio. 17. 
 
 and instruments for one of the terminal stations of a
 
 RELAY MAGNET. 
 
 LOCAL SOUNDER. 
 
 COMBINATION MAIN LINE INSTRUMENT. 
 Manufactured bg L. 0. Tittotson & Co., New York.
 
 THE MORSE, OB AMERICAN TELEGRAPHIC SYSTEM. 
 
 35 
 
 line. The line wire L first enters the lightning arrester 
 X, and passes thence through the coils of the relay M 
 by the binding screws, 1, 2, and thence to the key K, 
 main battery E, and finally to the ground at G. The 
 local circuit commences at the + pole of the local bat- 
 tery E' and through the platina points of the relay by 
 the binding screws, 3, 4, thence through the register 
 or sounder coils, S, and back to the other pole of the 
 battery. 
 
 59. ARRANGEMENT OF A WAY STATION. Fig. 18 
 shows a plan of the instruments and connections at a 
 way station. The line enters at L, passes through the 
 lightning arrester X (70), and thence through the relay 
 M, key K, and back to the lightning arrester, and 
 thence to the next station by the line L'. The arrange- 
 ment of the local circuit is the same as in the last figure. 
 The button C, arranged as shown in the figure, is called 
 a " cut-out" (62). When turned so as to connect the two 
 wires leading into the office, it allows the line current 
 to pass across from one to the other without going 
 through the instruments. The instruments should 
 always be cut out by means of this apparatus when 
 leaving the office temporarily, or for the night, and
 
 36 MODERN PRACTICE OF THE ELECTIUC TELEGRAPH. 
 
 also during a thunder storm, to avoid damage to the 
 apparatus. Fig. 21 shows a better arrangement. 
 
 The G-round Switch, Q (63), is used to connect the 
 line with the earth on cither side of the instruments at 
 pleasure. It is only used in case of accidents or inter- 
 ruptions on the lines, as will be hereafter explained. 
 
 60. ADJUSTMENT OF THE APPARATUS. The princi- 
 pal difficulties which the operator is liable to meet with 
 in working the Morse apparatus are as follows : 
 
 1. When the paper in the register does not run freely 
 from the reel on which it is held, or sticks in the guides 
 from irregularity in width, or if the style is adjusted to 
 indent the paper too deeply, the paper moves irregu- 
 larly, shortening dashes into dots, and causing dots to 
 run together. 
 
 2. The style should be adjusted so as to move freely 
 in the groove of the upper roller, or the marks will be 
 more or less indistinct. If it is completely out of the 
 groove, no marks will be produced. These faults gene- 
 rally arise from too much end play in the pivots of the 
 lever, or from the pivot screws working loose. When 
 the lever works too loosely in its bearings, irregular 
 dashes, too deep at their commencement, and tapering 
 off to nothing, will be produced. 
 
 Residuary magnetism sometimes causes the armature 
 of the electro-magnet to stick. This will always hap- 
 pen if the armature is allowed to touch the poles of the 
 magnet. The screw stop should therefore be adjusted 
 so as to prevent the armature from approaching too 
 closely to the poles of the magnet. The upper screw 
 stop, which regulates the play of the lever, should be 
 adjusted so that the movement is just sufficient to with- 
 draw the style from contact with the paper. 
 
 3. If the paper runs between the rollers "crooked,"' 
 the pressure of the upper roller upon the paper is 
 greater at one end than the other. This pressure is re- 
 gulated by two springs, one on each side of the iristr.i- 
 ment, and they should be made as nearly equal in pres- 
 sure as possible.
 
 THE MORSE, OR AMERICA* TELEGRAPHIC SYSTEM. %*J 
 
 4; When the signs are confused the relay requires 
 adjustment to suit the strength of the current. 
 
 5. If the relay moves by the action of the line cur- 
 rent, and the register or sounder does not act, the fault 
 is somewhere in the local circuit. If the register does 
 not work when the relay is moved by the linger, the 
 local circuit is certainly at fault, either from weakness 
 of the local battery, a loose connection, a broken wire, 
 or dirt between the platina points of the relay. The 
 latter should, when too much corroded, be cleaned care- 
 fully with emery paper, taking care to remove as little 
 of the platina as possible. 
 
 6. The sticking of the key, which sometimes occurs, is 
 caused either by the platina points becoming oxidized 
 and dirty, or by small particles of metal and dirt collect- 
 ing behind the circuit closer and about the anvil, caus- 
 ing a partial connection when the key is open. 
 
 7. It is very important that all the connections about an 
 office should be firmly screwed up. Neglect of this pre- 
 caution is a very prolific cause of trouble upon a tele- 
 graph line. 
 
 8. In rainy weather, or when the insulation of the 
 line is defective from any cause, the cores of the relay 
 must be withdrawn to a greater distance from the ar- 
 mature, to avoid the influence of the residual magnet- 
 ism, caused by the escape of the "current" from the 
 line. This is called "adjusting" the instrument, and is 
 one of the most important of an operator's duties, re- 
 quiring great judgment and skill during unfavorable 
 weather and on poorly insulated lines. The key should 
 never be opened without carefully adjusting the relay, 
 to be sure that no other offices are using the line. 
 
 SWITCHES OR COMMUTATORS. 
 
 61. These are employed for the purpose of connect- 
 ing one circuit with another, for dividing a circuit into 
 two parts, or in short, for any purpose where it is neces- 
 sary to alter the connections of a line or circuit. 
 
 62. Fig> 19 shows the simple Button or Circuit Ckser,
 
 33 
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 which is usually employed as a " cut out" (58). The 
 base A is of wood or hard rubber. The brass lever, B, 
 when in the position shown in the figure, forms an elec- 
 trical connection between the metallic studs C C, which 
 
 FIG. 19. 
 
 are continuous with the screws, D D, passing through the 
 table and terminating in binding screws, to which the 
 wires are attached. The spring F, pressing against 
 the lever, insures a firm contact with the studs. This 
 circuit closer is sometimes, for special purposes, made 
 with four connections instead of two. 
 
 63. Fig. 20 represents a Ground Switch (58). The lever
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 30 
 
 A is attached to a wire leading to the earth, and the two 
 studs, B, C, are connected to the line wire on each side 
 of the instruments. 
 
 64. THE PLUG SWITCH is shown in fig. 21. This ar- 
 rangement consists of a brass spring, brought very 
 firmly against a stationary pin. A wedge or plug made 
 of two pieces of brass, separated by an insulating mate- 
 rial, is made in the form shown, to admit of insertion 
 between the spring and the pin. The wires leading to 
 the instrument are attached to this wedge by flexible 
 conductors. When the wedge is inserted, the line cur- 
 rent is diverted through the instrument, but is not in- 
 terrupted. The instrument may readily be withdrawn 
 from the line by taking out the wedge, the spring in- 
 stantaneously closing the main circuit. This arrange- 
 ment is found extremely useful in connecting batter- 
 ies as well as instruments. At a way station it is 
 preferable to a simple cut-out, for the reason that the 
 apparatus is entirely disconnected from the circuit when 
 the wedge is withdrawn (59). 
 
 65. THE UNIVERSAL SWITCH, for the use of offices 
 having a considerable number of wires, is constructed
 
 40 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 in several different forms, although the principle in- 
 volved is nearly the same in each. Fig. 22* represents 
 
 the arrangement most generally used, which is known 
 as the Culgan Switch, from the name of its inventor. 
 The upright straps of brass, A, B, C, D, E, F, are fixed 
 upon a slab of hard wood, or other non-conducting ma- 
 terial, and provided with binding screws at their upper 
 extremities, for the reception of the line wires. The 
 binding screws, I, II, III, IV, V, VI, are in electrical 
 connection with the horizontal rows of buttons, by wires 
 underneath the board, not shown in the figure. Thus, 
 any wire attached to one set of binding screws may 
 readily be connected with any wire attached to the other 
 set, by simply turning the appropriate button. A row 
 of metallic pegs, x x\ are so arranged that either of the 
 upright straps may be separated into two parts by the 
 withdrawal of the peg belonging to it, as shown at x. 
 The object of this device will be explained hereafter. 
 
 This switch may be made of any size and with any 
 number of connections, depending upon the number of 
 lines it is designed to accommodate. The wires may be 
 attached to it in a number of different ways, the parti- 
 
 * L. G. Tillotson & Co., New York.
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. ^ 
 
 cular arrangement adopted in each case depending upon 
 the nature of the changes required to be made. 
 
 66. ARRANGEMENT OF THE CONNECTIONS. The switch 
 shown in the figure, placed at a way station, could be 
 arranged to accommodate three through wires, and an 
 equal number of instruments, providing for all the ne- 
 cessary changes. The arrangements in this case would 
 be as follows : Connect line wires Nos. 1, 2 and 3, east, 
 with A, B and C ; 1 , 2 and 3, west, with D, E and F. 
 Instrument No. 1 to I and II, No. 2 to III and IV, 
 No. 3 to V and YI. Turn the buttons so as to connect 
 A with I and D with II. The circuit of No. 1 wire will 
 then enter at A, go to instrument No. 1 via I, returning 
 to II, and thence going out at D. The other instru- 
 ments may be connected at pleasure in the same man- 
 ner. If it is desired to connect a circuit through, for 
 instance No. 1, leaving the instrument out of circuit, it 
 is done by turning the buttons so as to connect both A 
 and D to the same horizontal wire, either I or II. By 
 a little study it will be seen that any wire cast may be 
 connected with any other wire west, with or without 
 any desired instrument, at pleasure. The ground wire 
 is attached at VII, and may be connected with any line 
 wire east or west at pleasure. 
 
 67. The same switch, placed at a terminal station,' 
 would provide for six wires, by connecting them as be- 
 fore to the screws A, B, C, D, E, F, and the instruments 
 to I, II, III, IV, V, VI. The wires of a loop (87) may 
 be connected to I and II in place of the instrument, 
 and may be put in circuit with any wire by turning the 
 buttons connected with I and II both on to the corres- 
 ponding strap, which is then divided by withdrawing- 
 the peg, forcing the current to pass through the loop.' 
 Extra sets of buttons for loops are usually provided 
 when the switch is intended for a terminal station, which 
 can be used without diminishing the capacity of the 
 switch for other purposes. 
 
 68. JONES' LOCK SWITCH is employed for the same* 
 purposes, and connected in the same mariner as the on#
 
 42 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 last described, but the connection between the vertical 
 and horizontal wires is made by a metallic peg, provided 
 with a spring, as shown in fig. 23 (Chester). This ar- 
 rangement entirely obviates the danger of imperfect 
 connections, from the loosening of buttons, etc., which 
 is sometimes a source of trouble in the Culgan Switch. 
 
 FIG. 23. 
 
 It is also cheaper and much more compact ; a matter of 
 some importance in arranging for the accommodation of 
 a large number of wires. 
 
 69. There are other forms of switches designed for 
 special purposes, which it is unnecessary to describe in 
 a work of this kind. Those already referred to are all 
 that are generally required in fitting up a telegraph 
 station. 
 
 LIGHTNING ARRESTERS. 
 
 70. The danger of injury to the instruments and 
 operators at a telegraph station, by atmospheric elec- 
 tricity, is usually guarded against by the use of an 
 apparatus termed the Lightning Arrester, which is con- 
 structed in accordance with the well established fact 
 that this kind of electricity, being possessed of enor- 
 mous intensity, prefers a short route through a poor 
 conductor to a longer one through a good conductor, 
 while the comparatively low intensity of the voltaic
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 43 
 
 current, used for telegraphic purposes, confines it to 
 the conducting wires. 
 
 71. THE PLATE ARRESTER. The arrester most usu- 
 ally employed upon the telegraph lines in this country 
 consists of a flat plate of brass, about five or six inches 
 in length, which is attached to the "ground wire." 
 Other plates of brass rest upon this, being separated 
 from it by a thin sheet of insulating material. These 
 last mentioned plates are provided with binding screws, 
 for the attachment of the line wires. Any surplus 
 charge of atmospheric electricity, entering by the line 
 wires, forces its way through the insulating material into 
 the ground plate, and is thus carried off to the ground 
 without injuring the apparatus. The form of arrester 
 supplied by the Messrs. Chester is shown in fig. 24. 
 
 The plates in connection with the line wires are 
 firmly held in their places by a wooden cross piece, 
 secured by screws at each end, as shown in the cut. A 
 thin sheet of gutta percha, or paper, is used to separate 
 the plates. When paper is used it should be saturated 
 with paraffine. Mica is, perhaps, better than either, as 
 it is not carbonized by the passage of the spark, as pa- 
 per sometimes is, so as to form a ground connection. 
 The manner in which the arrester is connected with the 
 wires leading into an office will be seen by reference to 
 fig. 18, where the two line wires, L and L', are attached 
 to the two upper plates of the arrester, X, while a wire 
 leading to the ground at G is attached to the lower plate. 
 
 72. BRADLEY'S ARRESTER. Another form of arrester,
 
 44 MODERN PRACTICE OF THE ELECTRIC TELEGRAPK. ! 
 
 designed by Dr. Bradley, is shown in fig. 25, and lias 
 recently been quite extensively employed, with excel- 
 lent results. 
 
 It depends for its action upon the well ascertained 
 fact that lightning always passes from a point to a plate 
 with great facility. The line wires leading into the 
 office are attached to the metallic plates A and B by 
 means of binding screws beneath, the ground wire being 
 attached in the same manner to the plate C. Platina 
 tipped screws, 1, 2, 3, 4, are fixed to each plate, and 
 are adjusted so as to come nearly in contact with the op- 
 posite plate. As lightning occasionally passes from the 
 earth to the clouds, as well as from the clouds to the 
 earth, this arrester is so arranged as to facilitate its 
 passage in either direction. The buttons, F F, are so 
 arranged that the apparatus serves for a "cut-out" and 
 a "ground switch" as well as an arrester. Its appli- 
 cation to these purposes will be at once understood by 
 an inspection of the cut. This form of arrester is 
 peculiarly well adapted for the protection of cables, or 
 any situation where it is exposed to accidental damp- 
 ness, as it is much less apt to interfere with the work- 
 ing of the line in such cases than the plate arrester pre- 
 viously described. 
 
 73. Lightning arresters must always be kept free 
 from dampness and dirt, as far as practicable. Much 
 annoyance often arises from neglect of this precaution, 
 as moisture between the plates will often cause a seri- 
 ous escape, greatly interfering with the working of the 
 line. This difficulty is especially liable to occur where 
 the arresters are used for the protection of submarine 
 cables. A flash of atmospheric electricity also fre-
 
 THE MORSE, OB AMERICAN TELEGRAPHIC SYSTEM. 45 
 
 .quently carbonizes the paper between the plates, or 
 fuses the metal, so as to permanently connect the 
 ground and the line. Consequently, the lightning ar- 
 resters should be frequently taken apart and examined. 
 This should invariably be done after a thunder storm. 
 
 REPEATERS. 
 
 74. When the length of a telegraphic circuit exceeds 
 a certain limit, depending upon the insulation, the size 
 of the conductor, the number of instruments in circuit, 
 etc., the line current becomes so enfeebled, even when 
 large batteries are employed, that satisfactory signals 
 cannot be transmitted. In such cases it was formerly 
 customary to re-write the messages at some interme- 
 diate station, but this duty is now usually performed by 
 an apparatus called a repeater. The principle of this 
 arrangement consists in causing the sounder or register 
 connected with one circuit to open and close the circuit 
 of another line by an action similar to that of a relay 
 (56). Repeaters are also often used for connecting one 
 or more branch lines with a main line, for the purpose 
 of transmitting press news, etc., simultaneously to dif- 
 ferent places. This enables all the stations in connec- 
 tion to write to each other as readily as if they were 
 situated upon the same circuit. 
 
 Since the general introduction of repeaters it has 
 become quite practicable to telegraph direct between 
 places situated at very great distances from each other. 
 It is not uncommon, at the present day, to work direct 
 through four or five thousand miles of continuous line 
 by the aid of these instruments with almost as much 
 facility as if it were one continuous circuit. On one or 
 two occasions the stations at Heart's Content, New- 
 foundland, and San Francisco, California, have been 
 placed in direct communication with each other, the 
 operators at these widely separated points conversing 
 with each other across the entire breadth of the conti- 
 nent without the slightest difficulty.
 
 46 
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 75. WOOD'S BUTTON REPEATER. This is the simplest 
 
 Fig. 26 shows 
 
 arrangement of this kind now in use. 
 
 the most convenient and serviceable form in which the 
 button or switch, and its connections, can be arranged 
 for the purpose of changing the circuits. The instru- 
 ments, batteries, &c., are shown in outline, for conve- 
 nience of explanation. M and M' are the eastern and 
 western relays, S and S' the eastern and western soun- 
 ders. The local connections are not shown, but are run 
 as usual. The eastern and western main batteries are 
 shown at B and B', and are placed with opposite poles 
 to the ground, at the repeating station, so that when the 
 line is put * ; through" the two batteries will coincide. 
 
 By means of this arrangement the following result 
 may be obtained : 
 
 I. Two distinct and independent circuits. The lever L 
 remaining in the position shown in the drawing (marked 
 1), and the button at 4, closed. 
 
 II. A through circuit. The lever L remains as before, 
 but the button at 4 is opened, throwing off the ground 
 connection between the two batteries, B and B'. 
 
 III. Two distinct circuits arranged for repeating. The 
 button at 4 is closed. If the lever L be placed in tho
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 47 
 
 position indicated by the figures '2, 2, the eastern soun- 
 der repeats into the western circuit. If the lever is 
 changed to 3, 3, the western sounder repeats into the 
 eastern circuit. The operator in charge of a button 
 repeater will find his duty very simple if he governs 
 himself by the following 
 
 RULE. When either sounder fails to work coincident 
 with the other, turn the button instantly. 
 
 In connecting up this apparatus, the arrangement of 
 the poles of the main batteries above specified should 
 be carefull} r borne in mind. It is also of the utmost 
 importance that these batteries should be perfectly in- 
 sulated from the ground, as the point at which the cir- 
 cuit is open and closed is between the battery and the 
 ground. Therefore, an escape occurring from the bat- 
 tery to the ground will cause a residual current upon 
 the main line, when the circuit is open at the repeat- 
 ing points of the sounder, and thus interfere with its 
 working. 
 
 In cases where it is not required to work the two 
 lines through in one circuit, the connections are ar- 
 ranged differently from the plan shown in iig. 26, the 
 main battery being placed in the circuit between the 
 lever L and the ground Gr, instead of at B and B', as 
 shown. In this case the switch 4 may be dispensed 
 with altogether. 
 
 76. The lever of the sounder moves through a certain 
 space before closing the circuit of the second line, so 
 that the duration of the current sent forward is shorter 
 than that received from the transmitting station. A 
 second repeater shortens it still more, so that the dots 
 cease to be repeated, and arc frequently lost altogether. 
 The sending operator must therefore transmit the sig- 
 nals more firmly, as it is termed ; that is, increase the 
 length of the key contact, especially when sending dots. 
 For the same reason, the sounder levers in a repeating 
 apparatus should be adjusted to have as little motion as 
 possible. 
 
 77. HICKS' AUTOMATIC REPEATER. This arrangement
 
 48 
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 dispenses with the attendance of an operator for the 
 purpose of changing the circuits while working, the only 
 attention required being to keep the relays properly 
 adjusted. The principle of the apparatus is shown in 
 fig. 27. 
 
 ' The main circuits pass through the relay magnets M 
 and M', thence to the repeating points / g and f g', 
 attached to the opposite sounder levers respectively, 
 and thence to the main battery and ground at G and 
 G'. The platina points of the screws/ and/' are placed 
 uponU shaped springs, which, in a great measure, pre- 
 vents the shortening of the signals referred to in the 
 last paragraph. The local circuits are run through the 
 relay points b arid b' and the sounders R and R', on 
 each side of the apparatus, in the ordinary manner, but 
 to prevent confusion of lines, are omitted in the draw- 
 ing. The "extra local" magnets, L and L' act upon 
 armatures placed upon the relay levers a and a, oppo- 
 site to the regular armature. (See figure.) These 
 extra local magnets are movable by means of the screws 
 d d', and the adjustment of the relays M M' is performed 
 by means of these extra local magnets, the springs s s 1 
 not being used for this purpose. 
 
 In the figure the repeater is shown in its normal 
 position, with both circuits closed. The circuits of the
 
 THE MORSE, OR AMERICAN TELEGRAPHIC STSTEM. 49 
 
 extra local batteries B B' (shown by dotted lines) pass 
 through the sounder levers / /', the screws p p', and 
 thence respectively to the extra local magnets on the 
 opposite side of the apparatus. These magnets must be 
 so adjusted that their attraction is not sufficient to draw 
 the armatures away from M M' unless the main circuit 
 is broken. 
 
 It will also be seen, by referring to the drawing, that 
 when the main circuit is broken and the armature falls 
 back on the point c, that the extra local magnet L is cut 
 out. But the instant this happens the spring s draws 
 the armature away again. As soon as the contact is 
 broken at c there is a circuit through L, and the arma- 
 ture is again drawn back to c. The tension of the 
 spring s being but just sufficient to draw the armature 
 away from c, the armature vibrates on the point c through 
 such a small space, and with such rapidity, that the 
 motion is invisible to the eye. On account of the ex- 
 treme rapidity of these vibrations, it is impossible to 
 close the main circuit at a time when the extra local 
 magnet L is not cut out, and the armature will conse- 
 quently obey the slightest impulse caused by the attrac- 
 tion of the relay magnet. 
 
 The working of the apparatus requires but little fur- 
 ther explanation. If the western main circuit be broken, 
 for instance, the armature lever a falls back and vibrates 
 on the point c, as above described. The sounder lever 
 I first breaks the circuit of the eastern extra local mag- 
 net L', then that of the eastern main line, which passes 
 through the relay M. The circuit through both L' and 
 M' being thus broken, the slight tension of the spring s' 
 will hold the armature in its place, and prevent the 
 local circuit through R, and consequentl} r the western 
 main circuit, from being broken. When the western 
 circuit is again closed the reverse of these operations 
 takes place. 
 
 78. In using this repeater the springs s s' should be 
 adjusted with the smallest possible amount of tension, 
 just sufficient to hold the armature in place. When once
 
 50 
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 adjusted they should be let alone. Care must be taken 
 that none of the wires under or about the magnets touch 
 any part of the brass. The extra local magnets, for 
 example, may be cut out entirely in this way. The 
 screws that adjust the extra local magnets should be 
 oiled with fine oil to prevent wear and make their ad- 
 justment easy. The extra local batteries must be kept 
 of a uniform strength ; if they, are allowed to become 
 weak the instrument will be thrown out of adjustment. 
 79. MILLIKEX'S REPEATER. In the general arrange- 
 ment of its connections this repeater somewhat resem- 
 bles that of Hicks', but 'is more simple in principle. 
 Fig. 28 is a plan of its connections. The main line 
 L - , , 
 
 WEST n^fiHlfr 1 \ 
 
 EAST 
 
 FIG. 28. 
 
 wire from the west passes through the relay magnet M 
 and the repeating points f g' of the opposite soun- 
 der, and thence to the battery and ground at G'. The 
 eastern line passes through M', /and g to G, in a simi- 
 lar manner. 
 
 The extra local magnets L and L' are arranged, as 
 shown in the figure, so that when either of their arma- 
 tures is released it is drawn back by the spring attached 
 to its lever, bringing the latter firmly in contact with 
 the armature lever of the corresponding relay. The 
 extra local batteries arc shown at B and B' the circuit
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 5^ 
 
 of each being indicated by dotted lines. The ordinary 
 local circuit through the relay and sounder is omitted, 
 to avoid confusion in the diagram. 
 
 If the main circuit be broken in the western wire, 
 the relay M breaks the local circuit of the sounder R at 
 5. The movement of the lever / of the sounder first 
 breaks the extra local circuit at p, causing the magnet 
 L' to release the armature d', which is drawn back by 
 the spring s' against the top of the lever a, and, secondly, 
 the eastern main circuit, is also broken at /. g. The 
 lever a is prevented from falling back when* the circuit 
 of M' is broken by the tension of the spring s', which is 
 so adjusted as to be greater than that of the spring h '. 
 The apparatus on the right hand side of the repeater, 
 therefore, remains quiet while the west is working, and 
 vice versa, the current through M' being always restored 
 before that through L' is broken, which is effected by 
 the U shaped spring on the screw/. 
 
 One of the principal advantages in the construction 
 of Milliken's repeater consists in the fact, that any 
 slight variation in the strength of the extra local circuit, 
 from weakness of the battery or other causes, does not 
 affect the adjustment of the relay magnets, as in the 
 case with Hicks' repeater. The adjustment and action 
 of the two magnets are entirely independent of each 
 other, as will be seen by reference to the diagram. The 
 relay levers also move more freely, being unencum- 
 bered with extra armatures or other appliances. 
 
 In this, as in the Hicks repeater, buttons are pro- 
 vided, by means of which each line may be worked 
 separately without interfering with the other, if desired. 
 
 These are omitted in the drawing, to prevent confu- 
 sion, but are arranged so that, when closed, one button 
 forms a permanent connection between /and g, thus 
 preventing the movement of the lever I from breaking 
 the eastern main circuit, and another connects p and /, 
 thus keeping the extra local circuit constantly closed, 
 and the armature lever d' withdrawn from interference 
 with a.
 
 52 
 
 MODERN PKACTICE OF THE ELECTRIC TELEGRAPH. 
 
 The same thing may be accomplished by causing the 
 button to break the extra local circuit entirely, when 
 the instruments are to be worked separately, and " turn- 
 ing down" the adjusting spring s' of the lever d'. It 
 will, of course, be understood that the other side of the 
 repeater is arranged in precisely the same manner. 
 
 J 
 
 80. BUNNELL'S EEPEATER. The arrangement of the 
 main circuits in this repeater is exactly the same as in
 
 THE MORSE, Oft AMERICAN TELEGRAPHIC SYSTEM 53 
 
 the ordinary "button repeater,''' and will be readily 
 understood by reference to fig. 29. The eastern main 
 wire enters at the right, passing through the repeating 
 point, ', of the western sounder, S', and through the 
 coils of the eastern relay, M, and thence to the main 
 battery and earth at E. The western main wire is 
 similarly connected on the opposite side of the instru- 
 ment. In the button repeater (75) a switch is so ar- 
 ranged as to form a connection, cutting out the repeat- 
 ing points of the sounder on the opposite side, when 
 either line is working, requiring a person to be con- 
 stantly stationed at the instrument to make the neces- 
 sary changes when two stations, on opposite sides of the 
 repeater, are corresponding with each other. In Bun- 
 nell's repeater this duty is performed automatically by 
 means of two "governor" or controlling magnets, Gr Gr, 
 the action of which will be hereafter described. 
 
 The eastern and western main circuits both being 
 closed and the apparatus at rest, the course of the local 
 circuit of the eastern instrument is as follows : From 
 the local battery, L, through the coils of the eastern 
 sounder, thence passing through the closed relay points 
 at M, arid returning to the other pole of the battery. 
 The resistance of the governor magnet, G, prevents any 
 appreciable portion of the current from passing through 
 its coils, as long as the closed points of the relay, M, 
 afford it a shorter route. If the local circuit be broken 
 by the relay points at M, it is forced to pass through 
 the coils of the sounder, S, and also of the governor, G-. 
 
 When a circuit of low intensity passes through the 
 coils of two magnets, differing considerably in resistance, 
 the attraction of the magnet having the least resistance 
 is very small in comparison with that of the other. A 
 practical application of this principle is made in this re- 
 peater, by forming the helices of the governor magnet of 
 finer wire than that of the sounders. The effect of this 
 is, that when the local circuit is thrown through both mag- 
 nets by the opening of the relay, that the armature of 
 the governor magnet is attracted with considerable
 
 54 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH* 
 
 strength, while the magnetism developed in the sounder 
 is not sufficient to move its armature, although the same 
 current passes through its coils. This arrangement is, 
 of course, the same on each side of the repeater, and by 
 bearing it in mind the action of the instrument may be 
 readily comprehended. 
 
 When both main circuits are closed and the repeater 
 at rest, the governor magnets remain open, being cut 
 out by the points of the relays, which, as well as the 
 sounders, are closed on both sides of the apparatus. If, 
 now, we suppose the circuit to be opened by an oper- 
 ator on the western main line, the armature of the relay, 
 M', falls back, opening the sounder, S', and closing the 
 governor magnet, G', as previously explained. This 
 breaks the eastern main circuit at s, and also at a', as 
 well as the circuit of the opposite governor magnet, G, 
 at the point b. The breaking of the eastern main cir- 
 cuit at S' opens the eastern relay, M, and consequently 
 its sounder, S, but the circuit of the governor magnet, 
 G, being broken at 5', it remains inactive, and the wes- 
 tern main circuit is complete through the points, a, 
 although broken at the point, s, by the opening of the 
 sounder, S. Upon the closing of the western main 
 circuit this action is reversed, and the apparatus re- 
 sumes its original position. If the eastern main circuit 
 be opened the same action takes place, but on the 
 opposite side of the repeater. 
 
 In most repeaters hitherto constructed one side of the 
 apparatus remains silent while the opposite side is in 
 action, but in this oire the relays and sounders on both 
 sides work together, the points, a, a, on the armature 
 of the governor magnets acting automatically in the 
 same manner as the switch of a button repeater, when 
 moved by the hand of the operator. 
 
 81. An advantage claimed for this repeater is, that 
 both sides of the apparatus work together, affording the 
 operator in charge a better opportunity to know how 
 both lines are working. The extra local batteries are 
 dispensed with, and the relay levers are not encumbered
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 
 
 55 
 
 with extra armatures and other appliances. The ad- 
 justments required are the same as in a simple relay and 
 sounder. 
 
 82. Various other repeaters have been contrived, and 
 to some extent adopted in this country, but as those we 
 have described are much more extensively used than 
 any others, it has not been deemed necessary to describe 
 the others in a work of this kind. 
 
 83. COMBINATION LOCALS. In offices containing a 
 number of instruments, a single local battery is fre- 
 quently employed to operate all the sounders in the 
 office. Such an arrangement is called a combination 
 local. The best way of making the connections is shown 
 in fig. 30, in which the instruments are represented at 
 
 I, II, III and IV. The local battery is shown at E. 
 The common conductors, a and b, should be of large 
 copper wire, say No. 1 2 or 14. If the ordinary Daniell's 
 battery is used for this purpose, the cells should be con- 
 nected for quantity, as shown in the diagram, and not 
 in a single series. Every sounder in the combination 
 should have the same size and amount of wire in its 
 coils, as nearly as possible, in order to secure the best 
 results. 
 
 84. Another plan is to use separate locals, a wire 
 being run from one pole of each local to its correspon- 
 ding instrument, the opposite poles of the batteries, and 
 the instrument wires being all connected to a common 
 return wire. 
 
 85. These combination locals are very objectionable, 
 however, and their use should be avoided wherever
 
 56 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 possible. The iron cores in two different relays may 
 happen to be in connection with the silk covered wire 
 with which they are wound, a circumstance which fre- 
 quently occurs. In such a case, if the two armatures 
 chance to touch the poles of their respective relays, a 
 metallic connection, technically called a cross, is made 
 between the two main lines. Again, if these two relays 
 are at a terminal station, and in connection with two 
 main batteries, with opposite poles to the ground, the 
 combined force of both batteries is thrown on short 
 circuit, through the local return wire, burning the re- 
 la}^, exhausting the batteries, and interfering with the 
 operation of every wire connected with them. The 
 cause of these troubles being somewhat obscure, it might, 
 for a considerable time, escape detection. 
 
 86. LOCAL CIRCUIT CHANGER. In offices containing 
 two sets of instruments on different circuits, it is often 
 desirable to change them. A simple arrangement for 
 this purpose it shown in fig. 31, in which the relays are 
 
 represented at M and M' ; S and S' are the sounders or 
 registers, E and E' are the local batteries. B is a simple 
 button or circuit closer (62), having four connecting 
 points, 1, 2, 3, 4. When the button is in the position 
 1, 2, as shown in the figure, the relay M works the 
 sounder S, and the relay M' the Sounder S'. By 
 changing the position of the button to 3, 4, S is worked 
 by M' and S' by M. This simple arrangement is often 
 very convenient in railway stations, where a sounder 
 may be placed on one circuit and a register on the 
 other, so that an operator who is unable to read by 
 sound can instantly shift the register upon either line 
 at pleasure.
 
 THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 57 
 
 TECHNICAL TERMS USED IN THE TELEGRAPH SERVICE. 
 
 87. Line. The wire or wires connecting one station 
 with another. 
 
 Circuit. The wires, instruments, c., through which 
 the current passes from one pole of the battery to the 
 other. 
 
 Metallic Circuit. A circuit in which a return wire is 
 used in place of the earth. 
 
 Local Circuit. One which includes only the appa- 
 ratus in. ah office, and is closed by a relay. 
 
 Local. The battery of a local circuit. 
 
 Loop. A wire going out arid returning to the same 
 point, as to a branch office, and forming part of a main 
 circuit. 
 
 Binding Screws or Terminals. Screws attached to 
 instruments for holding the connecting wires. 
 
 To Cross-connect Wires. To interchange them at an 
 intermediate station, as in 117. 
 
 To put Wires straight. To restore the usual arrange- 
 ment of wires and instruments. 
 
 To Ground a Wire, or put on Ground. To make a 
 connection between the line wire and the earth. 
 
 To Open a Wire. To disconnect it so that no current 
 can pass. 
 
 Reversed Batteries. Two batteries in the same cir- 
 cuit with like poles towards each other. 
 
 To Reverse a Battery. To place its opposite pole to 
 the line ; or, in other words, interchange the ground and 
 line wires at the poles of the battery. 
 
 Escape. The leakage of current from the line to the 
 ground, caused by defective insulation and contact with 
 partial conductors. 
 
 Cross. A metallic connection between two wires, 
 arising from their coming in contact with each other, or 
 from other causes. 
 
 Weather Cross. The leakage of current from one 
 wire to another during rainy weather, owing to defec- 
 tive insulation.
 
 CHAPTER V. 
 
 INSULATION. 
 
 88. A telegraph wire suspended on poles is attached 
 to insulators, to prevent the escape of the current to the 
 earth at the points of support. Insulators should be 
 regarded in the light of conductors, whose value depends 
 ,upon their resistance to the passage of the current. 
 
 89. The insulation of a line is never perfect, even in 
 the dryest weather. There is a leakage at every sup- 
 port, which is greatly increased when the surfaces of the 
 insulators are damp, especially if covered with smoke 
 or dirt. Experiments show that soot will destroy the 
 surface insulation of the best insulators, even when 
 exposed to the cleansing action of the rain. This evil 
 is confined, however, principally to cities, and does not 
 manifest itself to nearly so great an extent in the open 
 country. 
 
 90. Insulators, considered as conductors, follow the 
 same law as other conductors. The less the diameter 
 and the greater the length, the more resistance is op- 
 posed to the escape of the current. As in this case the 
 resistance is almost entirely a question of surface, the 
 best insulator is that having the smallest diameter and 
 the greatest length between the wire and the support. 
 The latter is accomplished by making the insulator of 
 a cup form, or still better, of two cups, one placed 
 within the other. 
 
 91. The material of which the insulator is composed 
 shouM be a poor conductor of electricity and heat, a 
 non-absorbent of moisture, with a surface repellant of 
 water, and free from pores or cracks. It should also 
 remain unaffected by exposure to the weather, and the 
 effects of heat and cold. Nearly all of the materials
 
 INSULATION. |f|| . fyty 
 
 ordinarily employed are, however, liable to some of 
 these objections. ',/. 
 
 Insulators of glass and porcelain being conductors 
 of heat, a change of temperature from cold to warm 
 causes a condensation of moisture upon their surfaces, 
 including the portion protect- 
 ed from the direct action of 
 rain, and from this arises 
 the principal objection to 
 the use of these substances 
 in the construction of an in- 
 sulator. 
 
 Hard rubber is in itself a 
 better insulator than glass ; 
 but its surface, from exposure 
 to atmospheric influences, soon 
 loses its property of repelling 
 moisture, and becomes rough 
 and porous. 
 
 A surface which repels wa- 
 tery accumulations will cause 
 theni: to flow disconnectedly 
 in drops, instead of forming 
 a continuous conducting film. 
 This property is therefore one 
 of great value for the pur- 
 poses under consideration. 
 
 .1 
 
 92. THE GLASS INSULATOR. The insulator most com- 
 monly employed in this country is the glass. This is 
 generally made in the form represented by Fig. 32, 
 which is a sectional view of the insulator fixed upon a 
 wooden bracket, the latter being securely spiked to the 
 side of the pole. The line wire passes alongside the 
 groove surrounding the insulator, and is fastened with 
 a tie-wire encircling the insulator, both ends of which 
 are wrapped around the line wire. Tlie concavity of 
 the under side of the glass keeps it dry, in some meas- 
 ure preventing the current from escaping to the wet
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 bracket and pole through the medium of a continuous 
 
 stream of water. 
 
 93. THE WADE INSULATOR. This is largely used in 
 
 the Western States. Its construction is shown in Fig. 33. 
 A glass insulator, somewhat 
 similar in shape to that last 
 { described, is covered with a 
 (wooden shield, to prevent frac- 
 ture from stones and other 
 causes, the wood being thor- 
 oughly saturated with hot coal 
 tar, to preserve it from decay. 
 The line wire is tied to the 
 outside of the shield, in the 
 same manner as when the glass 
 insulator is used. 
 
 This insulator is usually 
 mounted upon an oak bracket, 
 as in Fig. 33, secured by spikes 
 to the side of the pole or other 
 support. When it is intended 
 to be mounted upon a hori- 
 zontal cross-arm it is placed 
 upon a straight wooden pin, 
 instead of a bracket. The pin 
 or bracket is usually saturated 
 with hot coal tar, in the same 
 
 manner as the insulator shield. 
 
 FIG. 34. Fio. 35. 
 
 94. FARMER'S HARD RUBBER INSULATOR. This is 
 shown in Fig. 34. It is a good insulator when new,
 
 INSULATION. 
 
 61 
 
 but by exposure to the weather its surface becomes 
 rough and spongy, and retentive of moisture. It is 
 screwed to the under side of the cross-arm or wooden 
 block, which is secured to the pole. The best form is 
 that which is made with a drip or shed, as shown in 
 the figure. If exposed to the direct action of rain it 
 ought always to be placed in a perpendicular position. 
 It will be noticed that this insulator holds the line wire 
 by suspension. 
 
 95. THE LEFFERTS INSULATOR. This is composed of a 
 suspension hook fixed in a socket of glass, of the form 
 represented in Fig. 35. This is inserted into a hole 
 bored in the under side of a block or cross-arm, and 
 fastened with a wooden pin. In painting the arm or 
 blocks the paint must not be allowed to get on the sur- 
 face of the glass. 
 
 96. THE BROOKS INSULATOR. Figs. 36 and 37 show 
 the construction of this insulator, which consists of a 
 suspension hook cemented into an inverted blown glass 
 bottle, which is again cemented into a cast iron shell, 
 provided with an arm which screws into the pole, as in 
 Fig. 36. Another form is made, designed for attachment
 
 62 
 
 MODEKX PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 to a cross-arm, as in Fig. 38. The remarkable insula- 
 ting properties of this arrangement are mostly due to 
 the use of paraffine, with which the cementing material 
 (sulphur) is saturated. It has also been discovered that 
 blown glass possesses extraordinary properties of repel- 
 ling moisture. Additional advantage of this fact has 
 been taken in the construction of this insulator, as may 
 be seen by reference to the cut. 
 
 97. Some important improvements have quite recently 
 been made in the mechanical construction of the Brooks 
 
 insulator, which are shown 
 in Fig. 39. In the old 
 form of hook, shown in 
 Fig. 37, the wire has three 
 bearings. To hold the 
 wire securely, it is neces- 
 sary that these bearings 
 should be so direct as to 
 make it difficult to place 
 the wire in it, and the 
 latter is often weakened 
 by being bent. The new 
 hook, shown in Fig. 39, 
 has five bearings for the 
 wire, but not so direct as 
 to injure or weaken it by 
 bending. The wire can be 
 placed in this hook without labor or difficulty, and a 
 strain cannot be applied in any direction by means of 
 which the wire can be removed or released. 
 
 98. MODE OF TESTING INSULATORS. The proper way 
 to test the comparative value of insulators is to fix 
 them upon frames or standards, in sets of ten or more, 
 'and place them where they will be fully exposed to 
 the weather. The tests should be made when the 
 weather is very wet, by means of a wire attached to 
 .all of -them in the usual manner, and leading to the 
 testing instrument, battery and ground. By this means 
 
 4he relative resistances of either of the insulators above 
 described, and their consequent value in the construc- 
 tion of a line, may be readily ascertained. 
 
 FIG. 39.
 
 INSULATION. 63 
 
 99. ESCAPE. When the insulation is defective, or the 
 wire comes in contact with the branches of trees, a wet 
 wall, or other partial conductor, a portion of the cur- 
 rent passes to the ground, forming what is technically 
 known as an escape. 
 
 100. WEATHER CROSS. The escape of the current 
 from one wire to another one upon the same poles^ 
 owing to defective insulation, is sometimes wrongly 
 called " induction," or " sympathetic currents." Wea- 
 ther cross is a much more appropriate term. 
 
 As electric currents always move in the direction of 
 the least resistance, their tendency is to escape from a 
 long circuit to a shorter one. This mixing of the cur- 
 rents from different wires is a much more serious evil 
 than a simple escape to ground, for the latter may in 
 most cases be overcome by increased battery power ; 
 but when cross connection exists between different 
 wires upon the same poles, an increase of battery upon 
 one wire gives it an advantage over the others, but 
 necessarily at their expense. 
 
 The effects of weather crosses usually manifest 
 themselves upon the occurrence of a shower sooner 
 than the escape to ground, because the horizontal arms 
 become wet sooner than the vertical pole. 
 
 On the English lines this difficulty is obviated by 
 means of an earth wire attached to each pole, and wrap- 
 ped around the center of the arms, thus cutting off the 
 currents passing from wire to wire, and conveying them 
 to the ground. The battery can then be increased at 
 will on one wire, without interference with the others. 
 A much more economical and effective method of obtain- 
 ing this result is that of improving the insulation. 
 
 101. EFFECT OF ESCAPES AND GROUNDS UPON THE 
 CIRCUIT. If the wire touches a conductor communica- 
 ting with the earth, or the earth itself, in a moist or 
 wet place, so that the point of contact offers littl^-or no 
 resistance compared with the wire beyond, the fault is 
 called a ground. The effect of a ground or escape is to 
 increase the strength of the current going out to the
 
 g^ MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 line, and to exhaust the batteries more rapidly. There- 
 fore, in working with a continuous current, as is the 
 case on American lines, the line current increases in 
 strength in wet weather, but the variation or difference 
 in the current at one station, when the line is opened 
 and closed at another, decreases, and the effective sig- 
 nals are therefore weakened. 
 
 102. THE LAWS OF THE ELECTRIC CURRENT. The 
 laws which govern the propagation and distribution of 
 electric currents are so simple, and at the same time so 
 important, that every telegrapher should be familiar 
 with them. By their aid the phenomena above referred 
 to may be readily comprehended. The most important 
 of these laws was first enunciated by Ohm, in 1827, 
 and is known as Ohm's law. It may be briefly stated 
 as follows : 
 
 Call the sum of the electro-motive forces. . .B 
 " " internal resistance of the battery. .R 
 " " resistance of line and instruments. .L 
 " " the effective strength of current. . .0 
 
 E 
 
 That is : The effective strength of the electric current in 
 any given circuit is equal to the sum of the electro-motive 
 forces divided by the sum of the resistances (174). 
 
 103. PRACTICAL APPLICATION OF OHM'S LAW. FIRST 
 CASE. To illustrate the application of this law to cir- 
 cumstances occurring in practical telegraphy, take the 
 
 case of an ordinary telegraph line (Fig. 40), extend- 
 ing from A to B, and perfectly insulated, having a re- 
 sistance of 100 Ohms. Let the main batteries, E and 
 E' have each an electro-motive force of 1,000, and a
 
 INSULATION. 65 
 
 resistance of 5 ohms, and let the resistance of the in- 
 struments I and I' be equal to 10 ohms each. The 
 total resistance of such a circuit will be : 
 
 100 ohms, line, I = L 
 
 20 " instruments, J ~ 
 10 " batteries, = R 
 
 130 " = R + L 
 
 The line being perfectly insulated, the whole cur- 
 rent from the batteries will necessarily act upon both 
 instruments. 
 
 As the effective strength of the current in any cir- 
 cuit is, by Ohm's law, equal to ^^ in this case it will 
 be 
 
 2000 
 
 130 =15 ' 4 
 With key open at A or B = 00.0 
 
 Difference, or effective working strength . = 15.4 
 
 If, on the above line, an escape occurs between the 
 stations A and B, offering a resistance of -50 ohms, the 
 effect will be the same as if a wire having a resistance 
 of 50 ohms were connected from the centre of the line 
 to the ground. The current from each battery has a 
 tendency to divide at the fault between the two routes 
 open to it, in proportion to their relative conductivity; 
 or, what is the same thing, in inverse ratio to their 
 respective resistances. But in this case the electro- 
 motive forces and the resistances are exactly the same 
 on each side of the fault ; and the positive current from 
 one battery, and the negative from the other, have an 
 equal tendency to escape to ground at the fault. These 
 opposite tendencies consequently neutralize each other, 
 and no effect whatever is produced upon the circuit by 
 the fault as long as the line remains closed both at A 
 and B. 
 
 If, however, A is sending to B, his key is alternately 
 open and closed. When open, the circuit of the bat* 
 
 I
 
 (5Q MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 tery E (Fig. 41) is entirely broken. There will still, 
 however, be a circuit from the battery E', through I 1 
 and the line to the fault F, and thence to the ground. 
 
 
 [ 
 u 
 
 50 
 
 
 
 
 EL.. 
 
 I 
 
 
 By Ohm's law we find the strength of this current to 
 be as follows : 
 
 5 ohms resistance of battery, . . = II 
 10 " " " instrument, ) 
 
 50 " " " i line, ] = L 
 
 50 " " " fault, 
 
 115 = II + L. 
 
 C = JL 
 
 L 115 
 
 With the key dosed at A, the strength of the current 
 in the instrument at B was found to be 
 
 15.4 
 With key open at A, as above 8.7 
 
 Difference, or effective working force. .. 6.7 
 
 In this case the latter will obviously be the same, 
 whether A sends to B or B to A. 
 
 104. SECOND CASE. Suppose the same fault to be 
 located near A (see Fig. 42). 
 
 The current from the battery E will divide at F, part 
 going to the ground through the fault, and the remain- 
 
 der over the line to B, and through the instrument and 
 battery to ground. The current from E' will divide in
 
 INSULATION. (J7 
 
 the same manner between the fault and the route 
 through I and E. Taking the battery E alone, and 
 considering the other battery E' simply as a conductor, 
 the two circuits beyond the fault give the following 
 resistance : 
 
 1. By the line instrument and battery at B. . 115 ohms. .-,. 
 
 2. " faulc F 50 " 
 
 115 x 50 
 Their joint resistance will be * .. r ^ = 34.8 ohms. 
 
 Add resistance of battery itself, 5 ohms, and instru- 
 ment, I, 10 ohms 15 " 
 
 The total resistance will be 49. 8 
 
 1000 
 
 This current will divide at the fault between the two 
 circuits, whose resistances are respectively 115 and 50, 
 or in the proportion of 23 to 10. Therefore 23 parts 
 of the current will go to the ground at F, and 10 parts, 
 = 2^2 = 6<1| wi ii go over the line to B. 
 
 The current from the other battery, E', in like man- 
 ner divides at F, between the fault and the circuit 
 through the instrument and battery at A. The joint 
 resistance of the two circuits is 
 
 15 x 50 
 
 Add the resistance of the battery E, 5 ohms, instrument I, 10 
 
 ohms, and line, 100 ohms ........................... .115.0 
 
 Total resistance ...................... .................. 126.5 
 
 1000 
 The current leaving the battery E will therefore be , = 1.9 
 
 The resistance of the two circuits beyond the fault 
 being 15 and 50, or as 3 to 10, 3 parts will go to 
 ground and 10 parts, or ^ =6.1, through I. . /.^ 
 
 * The joint resistance of any two circuits is found by dividing the product of the 
 two resistances by their sum. When there are three circuits, first find the joint re- 
 'sistance of two circuits as above, and treat it as a single circuit, again applying the 
 same rule. In the same manner the joint resistance of any number of circuits maj 
 be calculated (175).
 
 igg MODERN PRACTICE OF THE ELECTRIC TELEGRAPH, 
 
 When A sends to B, the current in the instrument 
 at B will be : 
 
 Key closed at A. 
 
 From battery E' T.9 
 
 ' E 6.1 
 
 Total strength in I' 14.0 
 
 Key open at A. ^ 
 
 From battery E' -y^r = 6.1 
 
 E ... 0.0 61 
 
 Difference, or available working current at B, 7.9 
 
 Now let B send to A. The current at A will be : 
 
 Key closed at B. 
 
 From battery E ....................... 20.0 
 
 E' . . ..................... 6.1 
 
 Total strength in 1 ..................... 26.1 
 
 Key open at B. 
 
 1000 
 From battery E ............... ^r~ 15.4 
 
 " " E' ....................... 0.0 
 
 Total strength in 1 ................... 15.4 
 
 Difference, or available working current at A, 10.1 
 
 ID 10 10 ' ft 
 
 I 
 
 no. 43. 
 
 105. THIRD CASE. Let the battery at A be doubled, 
 the fault remaining as in the last case. The electro- 
 motive force and internal resistance of E are both dou- 
 bled, as in Fig. 43. The current from E will now be : 
 
 ,' ' 2000 
 
 50 x 115 = 3G.5 
 
 which ^vvill divide at the fault in the same proportion 
 as before, the part going to B being 3g - 5 8 * 10 = 11.0. 
 
 1000 
 
 The current from E' will be ilTj> x * =.7.7, and the 
 portion reaching A 7 - = 5.5.
 
 INSULATION. C9 ' 
 
 "When A sends to B the signals will be as follows : 
 
 Key closed at A. 
 
 Current at B = 7.7 + 11.0 = 18.7 
 
 Key open at A. 
 
 ]000 
 
 Current at B = -T^T- = 6.1 
 
 loo 
 
 Effective strength at B 12.6 
 
 Now let B send to A : 
 
 Key closed at B. 
 
 Current at A = 36.5 -f 5.5 = 42.0 
 
 Key open at B. 
 
 2000 
 ( ';<j Current at A = r - = 28.6 
 
 Effective strength at A 13.4 
 
 A E . 
 
 C: 
 
 FIG. 44. 
 
 106. FOURTH CASE. Double the battery at B, the 
 fault remaining unchanged. See Fig. 44. 
 
 Current from E = 50 x 120 _ 
 
 50 + 120 
 
 19.9 x 5 
 Portion going to B ... = = 5.8 
 
 2000 
 
 Current from E' = 50x15 
 
 + 50 + 15 ~ 15 ' 2 
 
 15.2 x 10 
 Portion going to A.. = ,.. = 11.7 
 
 A sending to B : 
 
 Key closed at A . 
 
 Current at B = 15.2 + 5.8 = 21.0 
 
 Key open at A. 
 
 2000 
 Current at B = -yy^~ = n - 8 
 
 Effective strength at B 9.2
 
 70 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 B sending to A : 
 
 Key closed at B. 
 
 Current at A = 19.9 + 11.7 = 31.6 
 
 Key open at B. 
 
 1000 
 
 Current at A = -rr- = 15.4 
 
 _____ 
 
 Effective strength at A 16.2 
 
 107. Thus we find that on a circuit consisting of 
 
 Line wire resistance 100 ohms. 
 
 2 batteries " .' 10 " 
 
 2 instruments " 10 " 
 
 each battery having an electro-motive force of 1000, 
 the signals received will be as follows : 
 
 Signals at A. Signala at B. 
 
 When the line is perfect 15.4 15.4 
 
 With escape 50 ohms in centre 6.7 6.7 
 
 SamefaultatA 10.7 7.9 
 
 Same fault at A, with battery doubled at A 13.4 12.6 
 
 Same fault at A, with battery doubled at B 16.2 9.2 
 
 108. The results of this investigation may be sum- 
 med up as follows : 
 
 When the batteries and instruments are equal at 
 each end of a line, a given fault will interfere most 
 with the working of the circuit when in the centre. 
 
 When the fault is near one end of the line, the sta- 
 tion farthest from it will receive the weakest signals, 
 and the station nearest it the strongest signals. 
 
 In increasing the battery power for working over an 
 escape, the addition should be made to the battery 
 nearest the fault. 
 
 109. DISTRIBUTION OF BATTERY POWER. If the in- 
 sulation of a line was perfect at all times, the position 
 of the battery in the circuit would be a matter of .in- 
 difference. As all lines, however, are subject to more 
 or less leakage or escape throughout their entire length, 
 the whole battery should not be located at one end of 
 a long line, for in this case signals would be received 
 much better at one end of the line than the other. The 
 usual arrangement is to place half the battery at each
 
 INSULATION. 
 
 end of the line, although if the escape be uniform 
 throughout the entire length of the line, the effect upon 
 its working will be the same, whether all the battery 
 is placed in the centre of the line or a portion of it in 
 the centre and the remainder divided equally between 
 the two ends. 
 
 If a certain portion of the line is especially defective 
 in its insulation, the distribution of battery power may 
 sometimes be varied in accordance with the principles 
 laid down, with manifest advantage. 
 
 The insulation of the batteries themselves is a mat- 
 ter of great importance, and should never be neglected. 
 (29.) 
 
 110. WORKING SEVERAL LINES FROM ONE BATTERY. 
 It has been for many years the practice in this country 
 to work a considerable number of lines at the same 
 time from a single battery. The number of wires that 
 can be worked in this manner without interference de- 
 pends entirely upon the proportion between the inter- 
 nal resistance of the battery employed and the joint 
 resistance of all the circuits connected with it. If the 
 resistance of the battery itself is inappreciably small 
 in comparison with that of the lines connected with it, 
 the current on any given circuit will vary but little, 
 whether the others be open or closed. With the Grove 
 battery of, say, 50 cups, it is possible to work as many 
 as 40 or 50 well insulated lines, of 300 miles or more 
 in length, without appreciable interference. The great 
 objection to this system is that, in wet weather, the re- 
 sistance of the lines is enormously diminished, and the 
 interference of one circuit with another, as a necessary 
 consequence, greatly increased. 
 
 It is a common practice when this occurs to increase 
 the number of cups in the batter} r , which in most cases 
 has a tendency to aggravate the very evil it is sought 
 to remedy; for with every such addition the resistance 
 of the battery becomes greater in proportion to that of 
 the lines, and the currents more unsteady and fluctu- 
 ating. No small part of the trouble experienced in
 
 f'J MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 working lines in wet weather arises from this cause, 
 although usually attributed entirely to defective insu- 
 lation. It is true, however, that the latter indirectly 
 causes the difficulty, by lessening the resistance of the 
 wires. 
 
 111. Experiments made on a very wet day, upon a 
 number of circuits of nearly the same length (100 miles), 
 leading out of New York city, proved that when one 
 such wire was attached to a carbon battery of 60 cups 
 the addition of three other similar wires reduced the 
 current on the first one 12 per cent. It is a common 
 practice to attach as many as eight wires to such a bat- 
 tery, which in the above case would have reduced the 
 current about 25 per cent. 
 
 112. It is the opinion of many scientific experts in 
 practical telegraphy that increased efficiency, as well as 
 economy, would result from working telegraph lines 
 with a single series of Daniell's battery, in its most ap- 
 proved form, upon each circuit. The objection urged 
 against this battery is the increased amount of room it 
 takes up, as well as its somewhat greater original cost. 
 
 113. As long as the present system remains in vogue, 
 care ought to be taken that the different circuits leading 
 from the same battery are as nearly as possible equal 
 in resistance ; and it must not be forgotten that the in- 
 terference caused by attaching too many wires to a 
 battery cannot le remedied by the addition of more cups 
 for intensity. The electro-motive force of a carbon bat- 
 tery is exhausted with a rapidity nearly in proportion 
 to the number of circuits supplied from it. In the case 
 of the Grove battery this effect is not so apparent.
 
 CHAPTER VI. 
 
 TESTING TELEGRAPH LINES. 
 
 1 114. Interruption and interferences from various causes 
 are constantly occurring upon telegraph lines, and one 
 of the most important of an operator's duties is to be 
 able to discover promptly the nature and location of a 
 fault, that measures may immediately be taken for its 
 removal. This is done by an investigation called test- 
 ing. The apparatus and methods now in general use 
 in this country are of a somewhat primitive nature, but 
 the improved modes of testing which have long been 
 employed in Europe are gradually becoming appreci- 
 ated here, and as these are based on sound scientific 
 principles, it is to be hoped that they will soon super- 
 sede the imperfect ones heretofore employed. 
 
 115. The principal interruptions to which a telegra- 
 phic circuit are liable may be summed up as follows : 
 
 DISCONNECTION. The continuity of the circuit is 
 broken, so that no current passes over the line. . 
 
 PARTIAL DISCONNECTION. This is usually caused by 
 rusty and unsoldered joints in the line, or by loose 
 screw connections in offices or about switches, which 
 offer great resistance to the passage of the current. 
 
 ESCAPE or leakage of current from the line to the 
 ground, caused by defective insulation, or contact with 
 trees, &c. When an escape is sufficient to entirely 
 prevent the working of the line it is called a "ground." 
 
 CROSS. When two wires are in contact, so that one 
 cannot be worked without interfering with the other. 
 
 WEATHER CROSS. When a portion of the current 
 from one wire leaks into others upon the same poles, 
 through defective insulation. The effect is similar to 
 that of a cross, but much less strongly marked. This 
 is often improperly called sympathy, or induction.
 
 Y4 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 DEFECTIVE GROUND CONNECTION. It sometimes Lap- 
 pens that the ground wire, or ground plate, at a termi- 
 nal station, is defective. The effect of this is to make 
 the wires connected with it appear as if in contact, or 
 crossed. This difficulty is often caused by the removal 
 of a meter in offices where a gas pipe is used as a 
 ground connection for several lines. 
 
 116. TESTING FOR DISCONNECTION. If the circuit is 
 broken at any point the relays will all remain open. 
 The operator at each way station should immediately 
 proceed to test the wire by connecting his ground wire, 
 first on one side of the instruments and then on the 
 other. If either connection closes the line circuit, the 
 interruption is on that side, as the circuit of the oppo- 
 site main battery is completed through the ground, in 
 place of the broken wire. If the ground wire gives no 
 circuit either way, it is probable that the interruption 
 is in the office, or that the ground connection is defec- 
 tive. Each operator should always first make sure 
 that the fault is not in or about his own office. Having 
 ascertained the direction in which the difficulty lies, he 
 should at once report the state of the case to the ter- 
 minal station at the opposite end. 
 
 FIQ. 45. 
 
 Fig. 45 represents a line with four stations, A. B, C 
 and D. Suppose the wire broken at F. By connect- 
 ing the ground wires at B and C, as shown, two dis- 
 tinct circuits are formed. A can work with B, and C 
 with D, showing that the fault is between B and C. 
 
 Disconnection is usually caused by the breaking of 
 the line wire, or by a key carelessly left open. Some 
 other causes are wires loose in their binding screws, or 
 defective switches, or the fine wire in or about the re-
 
 TESTING TELEGRAPH LINES. ^5 
 
 lay may be broken. The latter is sometimes burned 
 in two by atmospheric electricity. 
 
 317. PARTIAL DISCONNECTION. It is rather difficult 
 to discover this fault by the ordinary relay tests. It is 
 frequently of an intermittent character, and requires to 
 be very carefully tested for. In the latter case, the 
 best plan is to cross connect, or interchange the defec- 
 tive wire with a good one at the terminal, and also one 
 other station, as in Fig. 46. Suppose the fault is at F, on 
 No. 2 wire ; by cross connecting at A and B, as shown, 
 
 FIG. 4G. 
 
 the fault will shift to No. 1 circuit, showing that it is 
 between those points. If it were beyond B, it would 
 remain on No. 2 circuit. In this case, let the wires be 
 put straight at B, and cross connected at C, and so on, 
 station by station. When the fault is passed it shifts to 
 the other circuit, and will therefore be found between 
 the two last stations. 
 
 118. To TEST FOR AN ESCAPE. Call the stations up 
 in rotation, beginning with the one farthest off, and 
 have them open key for a minute or two. When a 
 station beyond the escape is open, more or less current 
 will still pass out to the line through the relay, return- 
 ing through the ground from the fault. 
 
 
 
 Suppose A (Fig. 47) is testing. When the circuit is 
 open at C or D a current will pass from E through the 
 fault, F, which will be interrupted when B opens, show- 
 ing the fault is between B and C.
 
 70 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 119. TESTING FOR GROUNDS. A ground is tested 
 for in a similar manner. The operator at a way sta- 
 tion can ascertain which side of him the ground is 
 situated, from the fact that it cuts off or greatly weak- 
 ens the main battery current from that direction, when 
 tested with a ground wire by means of the finger or 
 tongue. 
 
 Telegraph lines are very liable to be grounded by 
 the action of atmospheric electricity upon the lightning- 
 arresters. These should be carefully looked after at 
 frequent intervals, especially where exposed to damp- 
 ness, as in cable boxes. 
 
 ] 20. TESTING FOR CROSSES. In case a cross is sus- 
 pected between two wires, say Nos. 1 and 2, instruct 
 the most distant station to open one wire, preferably 
 the through wire, or No. 1, and "send dots" upon the 
 other. Open No. 2 at your own station, and if the dots 
 sent on No. 2 at the distant station are received on 
 No. 1, the wires are crossed. Care must, of course, be 
 taken not to be deceived by the leakage from one wire 
 to another, caused by defective insulation. If the 
 wires are in actual contact, the signals received upon 
 No. 2 wire will be nearly or quite as strong as if re- 
 ceived upon No. 1. 
 
 Next, instruct the distant station to leave No. 1 open, 
 and open it also at your own station. No. 2 will now 
 be free from interference, and the stations upon it may 
 be signalled without difficulty. Call them in regular 
 succession, commencing at the farthest end 01 the line, 
 and instruct each one in turn to send dots on No. 2. If 
 the dots are received on both wires the cross is be- 
 tween you and the station sending ; but if upon No. 2 
 only, it is beyond that station. It is better that each 
 operator, while sending dots, should open the other 
 wire, if practicable. 
 
 The principle of this test will be understood by refer- 
 ence to Figs. 48 and 49, which represent a two wire 
 line, with four stations, A, B, C and D, the wires being 
 " crossed" between B and C. The operator testing for
 
 TB3T1XO TELEGRAPH UNES. 
 
 the cross is supposed to be at A. In Fig. 48 station C 
 has No. 1 open, and station A has No. 2 open. If C 
 sends dots on No. 2 the circuit will shift to No. 1, at 
 the cross, as shown by the arrows, and the dots will 
 
 come on No. 1 instrument at A, showing that the cross 
 is between A and C. In case C were unable to open 
 No. 1 the effect would evidently be the same, provided 
 it remains open at D. 
 
 Now let C close both wires, and B open No. 1, and 
 write dots on 2 (Fig. 49). If No. 2 be open at A, B 
 will be unable to work in this case, as both wires are 
 open, one at A and the other at B. With both wires 
 
 closed at A, B's dots will come on No. 2, the current 
 from F passing over both wires to the cross, and from 
 thence on No. 2, No: 1 being open, as shown in the 
 figure. Thus the fault is located between B and C. 
 
 In large offices, where there are a considerable num- 
 ber of wires, it will often be found a much more con- 
 venient and expeditious method of testing for crosses 
 for the operator to station himself at the switch with a 
 single instrument, which can be placed at pleasure on 
 any wire, for the purpose of communicating with differ- 
 ent stations. When any station is " sending dots " the 
 testing operator can feel them by placing a linger upon 
 the ground wire, and another upon the proper line wire
 
 V8' 
 
 MODERN PRACTICE OF TIIS ELECTRIC TELEGRAPH. 
 
 at the switch. The principle involved is of course the 
 same as in the method first described. In wet weather, 
 however, testing by the sense of feeling is attended 
 with much uncertainty, as it is impossible to distinguish 
 between the effect of a metallic cross, or actual contact, 
 and the leakage arising from bad insulation. 
 
 121. It would be difficult to specify all the minor in- 
 terruptions that are liable to occur in and about tele- 
 graph offices, or on the lines ; the operator will there- 
 fore, in many cases, be obliged to depend upon his own 
 ingenuity for the best method of testing applicable to 
 each particular case. By carefully studying, however, 
 the principles heretofore explained, the intelligent tele- 
 grapher will usually be able to cope with any difficulty 
 that may chance to arise in the ordinary service of the 
 lines. 
 
 122. TESTING WITH THE GALVANOMETER AND RE- 
 SISTANCE COILS. In the more accurate and scientific 
 modes of testing, which have been for some years em- 
 
 LINE 
 
 ployed upon the European lines, the instruments used 
 are the differential galvanometer and a set of standard 
 resistance coils (44). 
 
 The arrangement of the connections will be under- 
 stood by reference to Fig. 50.
 
 TESTING TELEQRAPH LINES. *^9 
 
 The galvanometer coils are wound with two wires of 
 the same length and resistance, insulated from each 
 other with the utmost care. The needle is, therefore, 
 surrounded by an equal number of convolutions of each 
 wire, which are also equi-distant from it. 
 
 The inner end of one coil surrounding the galvano- 
 meter, g, is joined to the outer end of the other at a, 
 and a key, K, attached to this junction, when de- 
 pressed, forms the connection with the testing battery, 
 E. The other ends of the coils run to binding screws, 
 M M', for the convenient attachment of lines to be 
 tested. The principle upon which the action of the 
 instrument depends is the following : 
 
 When the battery is connected by depressing the 
 key the current divides into two equal portions at a, 
 one flowing from a to M, tending to deflect the needle 
 to the left, and the other from a to M', tending to de- 
 flect it to the right; but as long as the two currents are 
 of the same strength they balance each other, and the 
 needle remains at rest. Suppose that the terminal M' 
 is connected to a telegraph line whose remote end is to 
 ground, and the terminal M is connected through the 
 resistance coils, R, to the ground likewise, as shown in 
 Fig. 50. We have already seen (102) that the strength 
 of an electric current is in all cases equal to the electro- 
 motive force divided by the resistance. Therefore, if 
 in this case we let 
 
 E = electro-motive force of battery, 
 
 I resistance of line wire, 
 
 g = resistance of galvanometer coil, 
 
 r = resistance coils in circuit, 
 
 the current in the two circuits surrounding the needle 
 will be 
 
 E E 
 
 y * r 
 
 If, therefore, the resistance coils in circuit be varied 
 until r = /, the needle will remain unaffected. As the 
 earth offers no appreciable resistance to the passage of 
 the current, the resistance of the line I will be accu-
 
 gO' MODERN PRACTICE OF THK ELECTRIC TELEGRAPH. 
 
 rately represented by the amount of resistance inter- 
 posed at r, in order to bring the needle to zero. The 
 value of the above equation will obviously not be 
 affected by any change in the value of E. 
 
 123. The resistance coils, R; : accompanying the gal- 
 vanometer, are so arranged asjto be adjustable to any 
 required resistance, from 1 ojim up to 10,000. For 
 the measurement of still higher resistances one coil of 
 the galvanometer is provided with three " shunts," or 
 branch circuits, x, y, z, having resistances respectively 
 equal to , J Vt and ^; therefore, if x be connected, 
 T V of the current will pass through g, and /o through 
 the shunt. In the same manner y and z respectively 
 allow but T w and ToVo- of the current to pass through 
 one wire of the galvanometer, when connected, and by 
 this means the instrument maybe made to measure 
 any resistance, from 0.001 up to 10,000,000 ohms. 
 
 124. TESTING FOR THE DISTANCE OF FAULTS. The 
 principle upon which the methods of distance testing are 
 founded is that of finding the resistance of the line wire 
 between the testing station and the fault by means of 
 the apparatus described. When the line is broken at 
 any point one of the following four cases generally 
 occurs : 
 
 1. Line wire broken, giving full, or nearly full, 
 ground connection. 
 
 2. Line wire unbroken, but gives nearly enough 
 escape to ground to make signals imperceptible. 
 
 3. Line wire broken, without making contact with 
 earth. 
 
 4. A cross between two wires, so that signals sent 
 on one are communicated to both. 
 
 125. It is very essential that the resistance of each 
 circuit should be frequently measured and recorded, so 
 that when a fault occurs the actual resistance per mile 
 of the line may be known. If the broken line gives a 
 full ground, its resistance divided by the resistance per 
 mile at once gives the distance of the break from the 
 testing station and if the distant station obtains a
 
 TESTING TELEGRAPH LINES. 31 
 
 corresponding result, the confirmation is complete. 
 Thus, in a line of 100 miles in length, if the tests from 
 the two extremities indicate distances of 45 and 55 
 miles, respectively, the locality of the interruption is 
 clearly indicated. As the fault, however, usually gives 
 a very considerable resistance at the point where the 
 line is in contact with the earth, and the sum of the 
 two resistances, measured from stations at the opposite 
 ends of the line, greatly exceeds the resistance of the 
 line itself when perfect, it is usual in such cases to 
 estimate the fault midway between the two points indi- 
 cated. Thus, when the respective resistances indicate 
 86 and 26 miles, the sum of these exceeds 100 miles by 
 12, and therefore half this excess, or 6, is deducted 
 from each of the measures. 
 
 126. When the line is unbroken, but shows a heavy 
 escape or partial ground, sufficient to weaken signals, 
 two or three different methods are available for deter- 
 mining its locality. The first plan is that of direct 
 measurement, alternately from each end, the distant 
 end at the same time being insulated, or, in other 
 words, left open, in the manner explained in the last 
 paragraph. In this case the resistance of the fault is' 
 measured twice over, and is roughly allowed for by the 
 method of calculation above given. 
 
 127. THE LOOP TEST. A second and more accurate 
 method, which gives a measure entirely independent of 
 the resistance of the fault itself, is known as the loop 
 test. It is only available, however, in cases where 
 there are two or more parallel wires on the same route. 
 In order to make this test, let the operator proceed as 
 follows : 
 
 Make the length to be tested as short as possible, 
 and have all the instruments in circuit taken out. Se- 
 lect a good wire, similar, if possible, to the one it is 
 required to test. Both these wires must then be con- 
 nected together in a loop, at the nearest available sta- 
 tion beyond the fault, without ground connection. The 
 resistance of the faulty wire, when perfect, must be
 
 82 
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 ascertained. This may be taken from previous records,, 
 or it may be found thus : 
 
 ^--Sr M GOOD WIRE 
 
 Connect one end of the 'loop to the + pole of the 
 battery E, and the other to one of the galvanometer 
 wires at M'. Connect also the + pole of the battery 
 with the resistance coils, R, at N, and the pole of 
 the battery to the key, K, and common terminal, a, of 
 the galvanometer. Connect the remaining galvanome- 
 ter wire with the resistance coils at M (Fig. 51). 
 
 Having ascertained the resistance of the loop, ar- 
 range the connections as shown in Fig. 52. 
 
 Upon depressing the key, K, the battery current will
 
 TESTING TELEGRAPH LINES. 
 
 ' ] 
 
 flow through M and R, and also through the loop. The 
 resistance required at R to balance the needle will be 
 equal to the sum of the resistance of the two linesj 
 Although there is a partial ground at F it will not 
 affect the measurement, as there is no other ground in 
 circuit. 
 
 Connect the + pole of the battery E to ground, and 
 connect the pole to the key K. Connect the perfect 
 wire of the loop to one of the galvanometer wires at M\ 
 and the faulty wire to the other galvanometer wire at 
 M, interposing the resistance coils R. When the key 
 K is depressed the current from the battery E flows" 
 into both lines simultaneously, passing to the ground 
 through the fault at F. By adding resistance at R, so 
 as to bring the needle to zero, the resistance a 1ST F 
 will be made equal to a M' F. 
 
 The resistance thus added, deducted from the total 1 
 resistance of the loop, previously ascertained, and di- 
 vided by two, is the resistance of the line between N 
 and F. 
 
 Thus, if the resistance of the loop be 1,000 ohms, 
 and 100 ohms have been added to the defective wire to 
 balance the needle 
 
 Then M0>) ~ 10 450 ohms, the resistance of the wire 
 between the resistance coils R and the fault. 
 
 Let M' F = a, N F = y. 
 
 Then x + y = L, the resistance of the loop. 
 
 As R + y = x, or R + N F = M' P. 
 
 L R 
 Therefore, y = - 
 
 Suppose that the loop of 1,000 ohms measures 120 
 miles, then, by proportion, 
 
 If 1,000 ohms = 120 miles, 450 ohms = 64 miles. 
 
 When an instrument or section of small wire is in- 
 cluded in the circuit, allowance must be made for their 
 resistance. It is a great assistance in these tests to, 
 know from previous records the exact resistance oi 
 every section of the line.
 
 g MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 - 128. BL AVI ER'S FORMULA FOR LOCATING AN ESCAPE. 
 Where there is but one wire the following method may 
 be employed. Three tests have to be taken for the 
 operation, viz : 
 
 ;. * , Let R = resistance of the line before it was defective. This must 
 
 be obtained from previous records. 
 ( " S = resistance of the line when grounded at the distant end. 
 
 " T = resistance of the line when disconnected at the distant end. 
 
 Multiply S by S and T by E, and add the products 
 together; subtract from this amount T times S, and 
 also R times S. Subtract the square root of the re- 
 mainder from S ; the remainder will give the resistance, 
 x, or the distance of the fault from the testing station. 
 
 .This process appears complicated, but is in reality 
 very simple. For example, suppose the line 100 units 
 loner, and the fault 68 units distant, and the resistance 
 of tli2 fault 9G units, as shown in Fig. 53 
 
 X 68 V32 
 
 Then R =: x + y = 63 + 32 = 100 
 
 . s =;.;. =M+ _ = 92 
 
 T = x + z = 68 + 96 = 164 
 
 We shall, however, have obtained these resistances 
 by measurement, and not by calculation. We there- 
 fore have : 
 
 S x S = 92 x 92 = 8464 ) , . ' 
 T x R = 164 x 100 = 16400 J 
 
 T x S = 164 x 92 = 15088 ) 24288 
 R x S = 100 x 92 = 9200 J ~ ^fg 
 
 And the square root of 576 is 24; which deducted, S = 
 92, gives 68 as the resistance of x, or the distance of 
 the fault from the testing station. 
 
 The distance, cc, being known, the others are obtained 
 with ease ; for R 68 gives y, the distance from the 
 opposite end ; and T 68 gives 2, or the resistance of 
 the fault itself. This test should be taken from both 
 
 * See note, 104,
 
 TESTING TELEGRAPH LINES. g 
 
 ends of the line, if possible. In the above calculation 
 the resistance of the fault is supposed to remain con- 
 stant during the measurements ; but as this is not often 
 the case in practice, the average of several measure- 
 ments should be taken. 
 
 129. To FIND THE DISTANCE OF A CROSS. The two 
 wires in contact form a loop, provided they are clean, 
 and are twisted together, so that the contact offers no 
 appreciable resistance. In such a case open both wires, 
 at the nearest station beyond, and test the resistance of 
 the loop. Half this resistance will be the resistance of 
 the wire between the galvanometer and the fault, and 
 from this the distance can be calculated, as before ex- 
 plained (127). All relays in circuit must be taken out, 
 or the proper allowance made for their resistance. 
 
 As it is difficult to tell with certainty whether the 
 cross offers resistance or not, it is a better plan to test 
 it as a ground. Test each wire in turn by the loop 
 method (127), grounding the wire at both ends. The 
 wire tested will then make a ground through the other 
 wire at the point of contact, and the location of the 
 latter may be readily ascertained. 
 
 Second Method* Suppose two wires. A and B,; 
 touch one another at the point F. Connect A to the 
 zinc of the testing battery, leaving it open at the re- 
 mote end ; it will then serve as a battery wire between 
 the battery and the fault (F). Ground B at the distant 
 end, and connect it to one coil of the differential gal- 
 vanometer at the testing station Put the other wire 
 of the galvanometer to ground. The current of the 
 battery will pass along the wire A and "divide at F, 
 one portion going to ground at the distant end of B, 
 and reaching the galvanometer through the wire con- 
 nected with the ground, the other portion returning to 
 the galvanometer through the nearer portion of B. If 
 the cross is exactly in the centre of B the needle will 
 not move, as the two currents will balance each other, 
 
 If one section of B is longer than the other, the resist^ 
 
 _ , * 
 
 * Culley's Handbook, 3d edition, page 279.
 
 g MODERX PRACTICK OF THE ELECTRIC TELEGRAPH. 
 
 ance added to the shorter section to balance the needle 
 will show the difference in the resistance of the two 
 sections. 
 
 Let L = the total resistance of B. 
 " x = resistance of the shorter portion. 
 (i L x = " " longer " 
 1 R = resistance added to shorter portion. 
 
 L-R 
 Then x = ^ 
 
 . 130. ADVANTAGES OF TESTING BY MEASUREMENT. 
 The testing of lines by actual measurement lies at the 
 very foundation of all efforts to improve the working 
 of our telegraphic system. The insulation resistance of 
 each of the principal circuits should be measured every 
 morning, and a record of the results kept for reference. 
 In England the standard of insulation is 1,000, 000 ohms 
 per mile in the worst of weather. Therefore, a line 
 of 200 miles should not give less than ~^ = 5,000 
 ohms. If it gives less than this the low resistance is 
 due to defective insulation. The line should, in that 
 case, be tested in many separate sections, either from 
 the terminal office or by a visit to each section. If the 
 resistance per mile is the same for each section, the 
 fault is probably owing to the nature of the insulation; 
 but if, as is usually the case, some sections are very 
 much worse than others, the trouble will be found in 
 contact with trees, broken insulators, and the like. A 
 visit to the faulty locality will disclose the cause of tho 
 evil. 
 
 131. In comparing the insulation of line wires of 
 different lengths, the insulation per mile must be ascer- 
 tained, othel-wise the longest wire will appear the 
 worst; therefore, multiply the insulation test in ohms 
 by the length of the wire in miles. If the insulation is 
 uniformly good throughout the circuit tested, the leak- 
 age will increase in direct proportion to the length of 
 the wire, irrespective of its thickness or conducting 
 power, for the resistance of the wire is very small in 
 comparison with the insulators, and need not be taken 
 into account.
 
 TESTING TELEGRAPH LINES. $[ 
 
 The following example from Culley's work will illus- 
 trate this. The figures given are the result^ of an ae- 
 tual test : 
 
 The wire A had a leakage equal to 29 
 
 " B " " " 30 
 
 " C " " " 50 
 
 Total leakage. . . : 109 
 
 The three wires, when connected together at the test- 
 ing end and left open at the distant end, gave a com- 
 bined leakage of 110. 
 
 When connected so as to form a continuous wire, open 
 at the distant end, the leakage was still 110. The ex- 
 periment was repeated, and extended to other wires, 
 with the same result. In this case the resistance of the- 
 insulators was very great compared with that of the 
 wire as much as t^o million ohms per mile. But on 
 a wet day three similar wires, whose respective leak- 
 ages were 196, 185 and 141, making a total of 552, 
 when looped in a continuous line, as in the second case 
 above, gave a test of only 476, the distant portion of 
 the wire being in reality tested by a current weakened 
 by the leakage in the nearer portions. 
 
 132. TESTING FOR CONDUCTIVITY RESISTANCE. The 
 metallic resistance of the line wires should be occasion- 
 ally tested in sections, in the finest weather. The re- 
 sistance should be uniformly in proportion to the length 
 of the wire. If any section discloses an unusually high 
 resistance per mile, it is very probable that there are 
 rusty, unsoldered joints in the line, or that the ground 
 connections are defective. It is difficult for those who 
 have not tried it to believe the vast improvement that 
 may be made in any line in a few days by actual mea- 
 surement, and an inspection of the sections which give 
 indications of being defective. 
 
 It is not an uncommon occurrence to find that a single 
 unsoldered joint in galvanized iron wire, which appears 
 perfectly firm and sound, will give a resistance, when 
 tested by the galvanometer, equal to many miles of 
 line. A line containing many bad joints will frequently
 
 88 
 
 MODERX PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 work better in wet than in dry weather, as the mois- 
 ture increases the conductivity of the oxide between 
 the wires at the joints. 
 
 In testing for conductivity, with the distant end of 
 the wire to ground, as in Fig. 54, the result is some- 
 times interfered with by earth currents. It is there- 
 fore better, when practicable, to use the loop method, 
 by connecting the wire to be measured in a loop with 
 another wire of known resistance. Unless this test is 
 made in fine weather, however, the leakage from one 
 wire to the other will decrease the resistance of the 
 loop. The battery must also be insulated from the 
 
 LINE: 
 
 CD J3 
 
 FIG. 54. 
 
 earth, otherwise the leakage at each insulator will de- 
 crease the apparent resistance, especially if the insula- 
 tion is defective. For instance, two wires on the same 
 poles, disconnected and looped at the distant end, had 
 a resistance of 6,475 ohms when the battery was en-? 
 tirely disconnected from the earth. Upon putting the 
 zinc pole of the battery and the line attached to it to 
 earth, the apparent resistance fell to 5,250 ohms. The 
 insulation resistance, with one wire disconnected, was 
 9,250 ohms, the weather being damp.
 
 CHAPTER YII. 
 
 NOTES ON TELEGRAPHIC CONSTRUCTION 1 . 
 
 133. In order to maintain uninterrupted telegraphic 
 communication between any two points, it is of the first 
 importance that the line should be well constructed and 
 properly insulated throughout. There are numerous 
 minor details in the construction and repairing of tele- 
 graph lines which merit much more attention than they 
 generally receive. The bad working of our lines is in 
 a great measure owing to the neglect of these appa- 
 rently trifling details, through ignorance or carelessness. 
 
 134. POLES. The poles intended for an ordinary 
 line should never be less than five inches in diameter 
 at the top, their length depending upon the number of 
 wires to be provided for, and in some measure upon 
 the location of the line. They should be set in the 
 ground to the depth of five feet, wherever practicable. 
 
 In setting poles around the curve of a railway, they 
 should be made to lean back against the strain of the 
 curve. 
 
 135. WIRE. For ordinary lines, galvanized iron 
 wire, of No. 8 or 9, Birmingham gauge, is generally 
 employed. For short lines, No. 10 or 11 will answer 
 very well. The "American Compound Wire," a re- 
 cent invention, is composed of a combination of a steel 
 core with a sheathing of copper. It has come into ex- 
 tensive use within the short time which has elapsed 
 since its introduction, and has, thus far, been found to 
 answer admirably. A wire of this kind, having a con- 
 ductivity equal to a No. 8 iron wire, weighs but 112 
 pounds per mile. 
 
 136. The less the size, and consequently the conduc- 
 tivity of the line wire, the more care is required in its
 
 90 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 insulation, for an increased resistance virtually adds to 
 the length of the circuit. Increased conductivity thus ad- 
 mits of a reduction in battery power, with a consequent 
 decrease in the escape of electricity, and long circuits 
 may be thus worked with much greater facility; a fact 
 which has been most unaccountably ignored in the con- 
 struction of the greater portion of the lines in this 
 country. 
 
 137. GALVANIZED OR ZINC COATED WIRE must 
 always be used for permanent work, for rust reduces 
 the conducting power of wires very rapidly. This is 
 especially the case with the smaller sizes, such as No. 
 11 or 12. In smoky places it is a good plan to paint 
 the wire before it is put up, for the gas arising from the 
 combustion of coal destroys the zinc coating in a short 
 time, as may be observed in many of our larger cities. 
 
 138. ARRANGEMENT OF WIRES UPON THE POLE. 
 Wires arranged vertically upon the poles, or one above 
 another, are more liable to get into contact with each 
 other than when arranged horizontally upon cross-arms. 
 When placed one above another, each alternate wire 
 should be fastened upon opposite sides of the poles. 
 
 It is better not to place wires of different sizes upon 
 the same poles or cross-arms if it can be avoided, as 
 they are much more likely to get " crossed" than wires 
 of the same size would be, as they do not keep time 
 with each other when swung to and fro by the wind. 
 
 139. JOINTS OR SPLICES. In the construction of a 
 line nothing is of greater importance than the perfect 
 continuity of the circuit, and this depends, in a great 
 measure, upon the perfection of the joints. The impor- 
 tance of this has been very generally overlooked by 
 the telegraphers of this country, and much trouble in 
 working lines has been experienced in consequence, the 
 cause of which has remained unsuspected. A single 
 rusty unsoldered joint will often cause more resistance 
 than fifty miles of line. 
 
 No joint or splice, however clean and firm, can be 
 depended upon if made by mere contact or twisting.
 
 NOTES ON TELEGRAPHIC CONSTRUCTION. 
 
 Sooner or later the metals will certainly rust, and this 
 tendency is increased by the passage of the current. 
 When copper and iron wires are joined together the 
 joint is especially liable to become defective from this 
 cause. It is a common error to suppose that joints 
 made in galvanized wire do not require soldering. 
 
 140. In making a joint each wire should be twisted 
 round the other, in the manner represented in Fig. 55, 
 the turns passing as close, and as nearly at right angles 
 as possible to the wire which they surround. A wire 
 must never be spliced by being bent back and twisted 
 around itself. 
 
 141. The best solution for soldering is chloride of 
 zinc, with a little muriatic acid added, for the purpose 
 of cleansing the wire. In connecting copper and iron 
 wire together, it is well to wash off the chloride of zinc, 
 and then coat the joint with paint or rosin, or else to 
 solder with the rosin alone. This will prevent local 
 galvanic action between the metals. 
 
 142. FIXING THE INSULATORS. In attaching insula- 
 tors to the poles they should be arranged in such a 
 manner as to prevent, as far as possible, the lodgment 
 of snow about them, so as to form an escape between 
 the wire and its support. The glass insulator is usually 
 cemented to the bracket by means of white lead or 
 asphaltum. The edge of the insulator must never le per- 
 mitted to touch the shoulder of the bracket; for in this case, 
 during a shower, a continuous stream of water flows 
 directly from the wire to the pole, entirely destroying 
 the usefulness of the insulator. For the same reason 
 an insulator ought never to be fastened down to a 
 bracket by means of a spike driven over it, as is often 
 done where there is an upward strain upon the wire. 
 ,The proper way, in such cases, is to use some form of
 
 92 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 "hook, or suspension insulator, and fasten the line into 
 it with a tie-wire. 
 
 In turning a sharp angle it is better to put on two 
 insulators and brackets at the corner pole, or the wire 
 will be liable to come in contact with it. 
 
 When the Lefferts or Brooks insulator is used, there 
 is danger of fracturing the glass while stringing wire, 
 by violently wrenching the wire into the hooks. By a 
 little precaution this result may be avoided. 
 
 143. Insulators and brackets are sometimes attached 
 to a cross-arm, or other support, in a horizontal posi- 
 tion. This ought never to be allowed, for a driving 
 rain will wet the whole inner surface of the insulator, 
 causing a great leakage of the current at every sup- 
 port. The same thing often occurs with improperly 
 shaped brackets, which cause the spray from falling 
 rain-drops to be dashed against the inside of the insu- 
 lator. The shoulder of the bracket ought to be rounded 
 or sloped off, so as to prevent this from happening. 
 
 Unless the insulator is securely fastened to the pin 
 or bracket which supports it, it is liable to be lifted off 
 by the wind, causing an interruption. 
 
 144. LEADING WIRES INTO OFFICES. The wires lead- 
 ing into offices are fruitful sources of escapes and other 
 interruptions, as the work is often very unskilfully or 
 carelessly done. Gutta-percha covered wires, unless 
 well protected, become entirely useless in a year or 
 two, if exposed to the air and light. The method em- 
 ployed in England to protect this kind of wire might 
 be adopted with great advantage in this country. The 
 gutta-percha wire is first covered with tape, and then 
 saturated with a preservative mixture.* 
 
 The best way to lead wires through the side of a 
 building is to enclose them in hard rubber tubes, with 
 
 * This mixture is made and applied as f >llows: Take equal portions of wood tar, 
 gas tar and slacked Mme. Boil tfiese together, stirring; them well while boiling, until 
 the moisture is entirely driven out, which may be known by the subsidence of the 
 frothing. When cool apply to the taped wire, and then cover the latter with dry 
 sand. ITang the wire up to dry in the air, and in three or four days it will be 
 ready for use. This coating resists sun and moisture, and effectually protects th 
 gutta-percha.
 
 NOTES ON TELEGRAPHIC CONSTRUCTION. Q3 
 
 the outer ends inclined downwards, to prevent moisture 
 from entering. In arranging these wires, it should be 
 borne in mind that the current will follow moisture and 
 dampness along the outer surface of covered wire, 
 unless it is so placed that the line of leakage is broken 
 at some point. 
 
 145. FITTING UP OFFICES. In running wires inside 
 an office, it is better never to allow two wires to touch 
 each other, even when covered with an insulating coat- 
 ing, as this may be burned by lightning or otherwise 
 rendered imperfect causing a cross-connection. The 
 proper mode of arranging the office connections and 
 running the wires to the instruments is shown in Figs. 
 17 and 18, pages 34 and 35. Splices in the office wires 
 should be avoided as far as possible, but when required, 
 they should be made by turning each wire eight or ten 
 times around the other. A less number of turns 
 answers for the line wire, because the strain tends to 
 keep the joint pressed together. Great care must be 
 observed in making the joint between the iron and cop- 
 per wire, which must in all cases be soldered. 
 
 146. GROUND CONNECTIONS. It is of the utmost 
 importance that the ground plate at each end of the 
 line should make a perfect connection with the earth. 
 The plate must be large, and buried deep in wet soil 
 below the reach of frost. A water or gas pipe makes 
 an excellent ground connection. The ground wire 
 should be attached outside the metre, as the latter 
 is liable to be occasionally disconnected for repairs. It 
 is advisable, whenever practicable, to form a connection 
 both with the gas and water pipes. The connection 
 should be carefully made and always well soldered. 
 
 147. CABLES. The shore ends of cables should be 
 bedded well out to low water mark. Dig the trench 
 to a good depth, and cover the cable with a piece of 
 heavy plank or joist, and secure it well with heavy 
 stones, laid at short intervals. -If the covering be 
 merely of sand it will soon wash away and leave the 
 cable uncovered. Newer allow any portion of a calk to
 
 94 
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 le exposed to sun or air, but cover it all the way from 
 the box where the connection is made with the air line. 
 
 Cable boxes always ought to be made double (one box 
 within another), in order to prevent wet from entering. 
 The unskilful manner in which these are often arranged 
 is a fruitful source of trouble in working lines. 
 
 Lightning arresters should be kept attached to cables 
 all the year round. It is not uncommon for heavy light- 
 ning to occur in midwinter in this country. 
 
 148. MAKING JOINTS IN CABLES. In splicing cables, 
 or other gutta-percha wire, the following is the method 
 recommended by the Bishop Gutta-Percha Company, 
 who have manufactured the greater portion of the sub- 
 marine cables in use in this country : 
 
 " Use gutta-percha one sixteenth of an inch thick, cut 
 in pieces to suit the joint. Soften it in hot water, and 
 keep it flat Wipe the surface with a cloth. Heat the 
 surface by holding it near a flat file or other iron, about 
 as hot as a laundress's iron ; if the iron causes the 
 gutta-percha to smoke, it is too hot. When dry and a 
 little sticky, wind two or three coatings of gutta-percha 
 around the joint, taking care that each coating is per- 
 fect and each layer is dry ; then smooth off and lap 
 the joint well over on the gutta-percha on each side of 
 the joining. Use no spirit lamp, nor anything with a 
 Haze. When gutta-percha is burned it cannot be re- 
 stored. Hot water joints are worthless. They will not 
 stand, and will open when dried out. 
 
 "In making joints it is absolutely necessary that the 
 hands of the operator should be clean, and that no 
 water, grease, dirt, or anything of the sort must be 
 allowed to touch the gutta-percha." 
 
 149. Another method is given in Culley's Handbook 
 of Practical Telegraphy, as follows : 
 
 "Prior to making the joint the gutta-percha is 
 removed from the ends of the wires for about one and 
 a half inches, and the copper wires are carefully cleaned 
 by scraping; the wires are twisted together for one 
 inch, the sharp ends being closely trimmed off. The
 
 NOTES ON TELEGRAPHIC CONSTRUCTION. 95 
 
 joint is then soldered with rosin and good soft solder, 
 containing a sufficiency of tin. 
 
 "After this the gutta-percha is scraped, or very 
 carefully pared back for about two inches, to remove 
 its outer surface, which is oxidized, and will not join 
 properly ; the wire joint is covered with Chatterton's 
 compound* and the gutta-percha, heated on both sides, 
 and tapered down over the joint till that from each side 
 meets. The junction is completed by means of a warm 
 joining tool, care being taken to mix the gutta-percha 
 well without burning. As soon as this has cooled an- 
 other coating of Chatterton's compound is spread over 
 the gutta-percha, taking care not to burn the compound. 
 
 "A new and clean sheet of gutta-percha is then 
 heated by means of a spirit lamp, and while so heated 
 carefully stretched so as slightly to thin it. Then, 
 while it and the Chatterton coated joint are still hot, it 
 is laid on the joint, and pinched tightly round it with 
 the finger and thumb, after which it is trimmed off close 
 with scissors. The seam is again pinched and carefully 
 finished off with a warm tool, so as to mix the gutta- 
 percha of the two sides, and the coating of the wire 
 itself, well together. 
 
 "The joint, when cool, is again covered with Chat- 
 terton's compound, and a longer and larger sheet of 
 gutta-percha is laid over it, pinched, cut, and tooled off 
 as before. 
 
 "When the joint is complete, another coating of 
 Chatterton's compound is applied over the whole, well 
 tooled over the joint, and when cool, rubbed with the 
 hand, well moistened, till the surface is smooth. 
 
 "The mixing of the old and the new gutta-percha 
 is most important, and joints generally fail from this 
 having been imperfectly done, or from the percha being 
 overheated. Cleanliness is essential to success. The 
 fingers should be used as little as possible, and must be 
 kept very clean." 
 
 * The ingredients of this are by weight, as follows' one part of Stockholm tar; 
 one part of rosin, and three parts of gutta-percha.
 
 CHAPTER Till. 
 
 HINTS TO LEARNERS. 
 
 150. FORMATION OF THE MORSE ALPHABET. The 
 characters of the American Morse Alphabet are formed 
 of three simple elementary signals, called the dot, the 
 short dash and the long dash, separated by variable 
 intervals or spaces. There are four spaces employed in 
 this alphabet, viz., the space ordinarily used to sepa- 
 rate the elements of a letter ; the space employed in 
 what are termed the "spaced letters," which will be 
 hereafter referred to ; the space separating the letters of 
 a word; and lastly, that separating the words them- 
 selves. 
 
 The value of these spaces should be carefully im- 
 pressed upon the mind of the learner. Beginners are 
 apt to conceive that the Morse alphabet consists solely 
 of dots and dashes, and this misconception has a ten- 
 dency to greatly increase the time required to become 
 good "senders." Uniformity and accuracy in spacing 
 is of no less importance than in the formation of the 
 letters themselves. The foundation of perfect Morse 
 sending lies in the accurate division of time into mul- 
 tiples of some arbitrary unit. 
 
 151. The duration of a dot is the unit of length in 
 this alphabet. 
 
 1. The short dash is equal to three dots. 
 
 2. The long dash is equal to six dots. 
 
 3. The ordinary space between the elements of a let- 
 ter is equal to one dot. 
 
 4. The space employed in the "spaced letters" is 
 equal to two dots. 
 
 5. The space between the letters of a word is equal 
 to three dots. 
 
 6. The space between two words is equal to six dots.
 
 HINTS TO LEARNERS. 97 
 
 The dot is an unfortunate appellation for this sign, 
 because it conveys the idea of a point, or to speak elec- 
 trically, a current of infinitely short duration. Elec- 
 tro-magnets, however, require time in magnetization 
 (38). Currents involve time in transmitting signals. 
 Clock-work requires time to run. Currents must be of 
 sensible duration. The dot, therefore, involves time, 
 but this time is variable, according to circumstances. 
 The length of the dot should increase with the length 
 of the circuit. In long submarine lines the dot has to 
 be made longer than the dash itself on short open air 
 lines, and the same thing occurs in working through 
 repeaters (76). In commencing, therefore, the habit 
 should be acquired of making short, firm dashes, instead 
 of light, quick dots. After the student has once learned 
 to send well, it is very easy to learn to send fast, but 
 after once getting in the habit of sending short and 
 rapid dots, or ''clipping," it is almost impossible to 
 get in the way of sending firmly and steadily. Begin- 
 ners should rather take pride in the accuracy with 
 which they space out the elements of the telegraphic 
 music than in the number of words they can stumble 
 through in a minute. 
 
 152. In the excellent little Manual of Prof. Smith* 
 six elementary principles are laid down as the basis 
 for practicing the alphabet, viz : 
 
 First principle. Dots close together. >^ 
 I S HP 6 
 
 Second principle. Dashes close together. 
 M 5 T 
 
 Third principle. Lone dots, j *~ 
 E 
 
 Fourth principle. Lone dashes. ^_ 
 T L or cipher 
 
 * Published by L. G. Tillotson & Co., New York 
 7
 
 f)g MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 Fifth principle. A dot followed by a dash. 
 A. 
 
 Sixth principle. A dash followed by a dot. 
 
 N 
 
 153. Correctness in sending depends in a great mea- 
 sure upon the manner in which the key itself is handled. 
 Place the first two fingers upon the top of the button 
 of the key, with the thumb partly beneath it, the wrist 
 being entirely free from the table. The motion should 
 be made by the hand and wrist, the thumb and fingers 
 being employed merely to grasp the key. The motion, 
 both up and down, must be free but firm. Tapping 
 upon the key must be strenuously avoided.. 
 
 154. The downward movement of the key produces 
 dots and dashes ; the upward movement spaces. It is 
 first necessary to acquire the habit of making dots with 
 regularity and precision, then dashes, and finally com- 
 binations of dots and dashes. It is the best plan for 
 the student to practice upon a register in a local circuit 
 with his key, as he will the more readily be able to 
 observe and correct the faults in his manipulation. 
 
 155. The student may now proceed to practice upon 
 the elementary principles. 
 
 1. Practice making dots at regular intervals, until 
 they are produced with the regularity of clock-work, 
 and of definite and uniform dimensions. The regular 
 tick of a watch or of a short pendulum is a valuable 
 auxiliary in acquiring this habit. 
 
 2. Next proceed to make dashes, first at the rate of 
 about one per second of time, which may afterwards be 
 slowly increased to three. The space between the 
 dashes must be made as short as possible. If the up- 
 ward motion of the hand, in forming the space, be made 
 full, it cannot be made too quick. 
 
 3. The third principle occurs but once in the alpha- 
 bet, and forms the letter E. It is made by a quick but 
 firm downward movement of the key. In practicing
 
 HINTS TO LEARNERS. <}<) 
 
 upon this or any other character, it should not be 
 repeated too rapidly, nor should the thumb and fingers 
 be taken from the key in the intervals between the suc- 
 cessive repetitions of the letter. 
 
 4. The fourth principle is somewhat difficult. The 
 usual tendency is to make T too long and L too short. 
 It will be observed that the same character is used for 
 L and the cipher or 0. Occurring by itself or among 
 letters it is always translated as L, but when found 
 among figures becomes 0. This would at first seem 
 liable to cause confusion, but in practice it is found not 
 to be the case. It was formerly the custom to make 
 the cipher equal to three short dashes. 
 
 5. The fifth principle, which forms the letter A, may 
 be timed by the pronunciation of the word again, 
 strongly accenting the second syllable. The tendency 
 of beginners is usually to make the dot too long and 
 the dash too short, and more especially to separate 
 them too much. 
 
 6. The final principle, the dash followed by a dot, 
 usually presents some difficulties. The universal ten- 
 dency of the student is to separate the dot from the 
 dash by too great a space. Time the movement by 
 pronouncing the word ninety, with the first syllable 
 somewhat longer than usual. 
 
 156. Having become thoroughly conversant with the 
 six elementary principles, the following exercises may 
 be taken up in order. 
 
 (1.) E I S H P 6 
 
 These should be practiced separately, until the right 
 number of dots can be made invariably, the last dot in 
 each being neither shorter nor longer than the prece- 
 ding ones. 
 
 (2.) T M 5 Tf L or cipher. 
 
 In practicing this exercise, care must be taken not 
 to separate the dashes too much, and to make the final 
 one in each letter exactly equal to the preceding ones.
 
 1'0() MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 Observe not to make the L too short. There is a gen- 
 eral tendency in beginners to shorten the final dash, 
 where two or more occur together. 
 
 (3.) A U Y 4 
 
 The usual tendency to make too much space between 
 the dot and dash, in the above letters, may be avoided 
 by making them as if by prolonging the final dot in I, 
 S, H and P. 
 
 (4.) I A S U 
 
 H V P" T 
 
 These are to be practiced in couples, as represented, 
 the object being to impress upon the student the differ- 
 ence in the characters thus coupled together. 
 
 (5.) N p B _ 8 
 
 The student having thoroughly mastered the sixth 
 elementary principle, he will have no difficulty in form- 
 ing the above characters. 
 
 (6.) AFX Parenthesis 
 
 Comma Semicolon "W 1 
 
 . The only caution necessary in this exercise is to form 
 the letters compactly, with the dashes of equal length. 
 (See Exercise 2.) Observe, that the Parenthesis may 
 be formed by running A U together, and the Semicolon 
 by AF, etc. 
 
 (7.) U Q 2 Period 3 
 
 These differ but little from exercises previously prac- 
 ticed, and require no particular directions. 
 
 (8.) K J 9 Interrogation 
 
 G 7 Exclamation 
 
 J and K are generally considered the most difficult 
 letters in the alphabet. Do not separate J into double:
 
 HINTS TO LEARNERS. 101 
 
 N, and be careful that the dashes correspond in length. 
 (See Exercise 2.) The figures 7 and 9 require care in 
 spacing correctly. 
 
 (9.) R & C Z Y 
 
 These are termed the "spaced letters," and require 
 great care in order to make them correct!}'. The 
 "space" should be just double that ordinarily used 
 between the elements of a letter. The usual tendency 
 is to make it too great. It should be just sufficient t6 
 distinguish these characters from I, S and H. 
 
 157. The construction and manipulation of the alpha- 
 bet having been thoroughly mastered by the practice 
 of the foregoing exercises, it is now presented in its 
 complete and consecutive form. 
 
 I. ALPHABET. 
 
 A ~ -- 
 
 B - P 
 
 C -. Q 
 
 D R ... 
 
 E - S ... 
 
 F T _ 
 
 G U 
 
 H .... Y - 
 
 I - W 
 
 J X 
 
 K Y .... 
 
 L Z .... 
 
 M & .... 
 
 N , 
 
 II. NUMERALS. 
 
 1 . 6 . 
 
 2 7 
 
 3 8 
 
 4 9 
 
 5
 
 102 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH, 
 
 III. PUNCTUATION, ETC. 
 
 *Period Exclamation . 
 
 Comma fParenthesis 
 
 Semicolon Italics 
 
 Interrogation ^Paragraph 
 
 Numbers are always sent twice over, to avoid error ; 
 once written out in full, and then in figures. In frac- 
 tions one dot is used to represent the line between the 
 numerator and denominator. 
 
 158. It is necessary to again caution the student 
 against falling into the common error from which most 
 books on the telegraph are not exempt that is enter- 
 tained respecting the elementary signs of the Morse 
 alphabet. It is said to consist of two characters, the 
 dot and the dash. The importance of the space is 
 utterly ignored. The difference between good and bad 
 sending is almost entirely a matter of spacing. A com- 
 mon fault of young operators is to run their words too 
 closely together. 
 
 If the principles laid down in this work be firmly 
 adhered to, the learner will be surprised, not only at 
 the rapidity with which he masters what appears to be 
 a very difficult lesson, but at the extreme accuracy with 
 which he manipulates his instrument. He must also 
 carefully bear in mind that one of the most universal 
 faults, among those attempting to learn the telegraphic 
 art, is that of going over a great deal and learning 
 nothing well. 
 
 159. READING BY SOUND. This can only be attained 
 by constant and persevering practice, keeping in mind 
 the principles above given. The lever of the Morse 
 apparatus makes a sound at each movement, the down- 
 
 * The Semicolon, Parenthesis and Italics are seldom used in this country. It is 
 customary among operators to ejnphasize particular words by separating the letters 
 more widely than ordinarily. 
 
 | Preceding and following the words to which they refer. 
 
 $ When this occurs the copyist makes a new paragraph, b/ commencing the 
 next word upon another line.
 
 HINTS TO LEARNERS. 103 
 
 ward motion producing the heavier one, or that repre- 
 senting clots and dashes ; or, more properly, the heavy 
 stroke indicates the commencement of a dot or dash 
 and the lighter one its cessation. A dot makes as much 
 noise as a dash, the only difference being in the length 
 of time between the two sounds. Thus, if the recoil or 
 lighter stroke be dispensed with, it would be impossible 
 to distinguish E, T and L from each other. 
 
 In learning to read by sound it is best for two per- 
 sons to practice together, taking turns at reading or 
 writing, and each correcting the faults of the other. 
 The characters must first be learned separately, and 
 then short words chosen and written very distinctly and 
 well spaced, the speed of manipulation being gradually 
 increased as the student becomes more proficient in 
 reading. After becoming sufficiently well versed in the 
 art to read at the rate of twenty-five or thirty words 
 per minute, the best practice will be found in copying 
 with a pen and ink from an instrument connected with 
 a line employed in transmitting regular commercial 
 messages, in order that the student may familiarize 
 himself with the usages of the lines and the minute 
 details of actual telegraphic business. 
 
 In conclusion, the student is warned against falling 
 into the common error of expecting great results from 
 little labor. To become an expert operator requires 
 much time and patience, and the most unwearied appli- 
 cation. Remember, that whatever is worth doing at all 
 is worth doing well. The time will seldom or never be 
 found when a thoroughly competent operator cannot 
 obtain immediate and remunerative employment, how- 
 ever overcrowded the lower walks _of the profession 
 may have become.
 
 CHAPTER IX. 
 
 UECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 
 
 160. THE AMERICAN COMPOUND .WIRE. This impor- 
 tant improvement in telegraphic conductors, referred 
 to in another part of this work (135), has, within two 
 or three years of its first introduction, become so 
 extensively used that it seems likely in time to work a 
 complete revolution in the American system of line 
 construction. This wire is composed of a core of steel 
 enveloped in a sheathing of pure copper, and coated 
 with an alloy, of which tin is the principal ingredient, 
 which serves to protect the whole from oxidization. 
 ; The relative strength of this wire is more than 50 
 per cent, greater than that of iron wire of equal weight, 
 and its conductivity is also largely in excess of the 
 latter. If we take, for example, a No. 8 galvanized 
 iron wire, the gauge now usually employed in this 
 country in the construction of the best lines, and 
 compare it with a compound wire of nearly similar 
 electrical capacity, the superiority of the latter will be 
 manifest. 
 
 
 Weight 
 per mile. 
 
 Tensile 
 Strength. 
 
 Conductivity. 
 
 Poles 
 per mile. 
 
 . 
 
 Galvanized Iron Wire (No. 8) 
 American Compound Wire (No. 8) . 
 
 375 
 
 112 
 
 1091 
 514 
 
 1 
 1 07 
 
 35 
 23 
 
 In the above table the average conductivity of a 
 mile of No. 8 galvanized wire is taken as 1, as a standard 
 of comparison. The last column shows the number of 
 poles per mile which will give the same percentage of 
 strain upon the ultimate strength of the wire. In 
 practice, however, it is safe to reduce the proportionate 
 number of poles used for the compound wire, as the
 
 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 
 
 105 
 
 fiteel core is much more homogeneous and less liable 
 to fracture on account of flaws, than the iron wire. 
 
 The advantages which arise from increased conduc- 
 tivity of the line wire and the diminution of the number 
 of points of insulation and support are fully treated 
 upon in another part of this work. The mechanical 
 advantages of the compound wire are also very great. 
 The labor of handling and stringing a light wire is much 
 less than when a heavy one is employed. In running 
 the wires over buildings, a mode of construction which 
 has become very common in all large cities, stretches 
 may safely be made double the length of those taken 
 with the ordinary wire, and yet with less strain upon 
 the insulators. Another important point in favor of 
 this wire is the imperishable nature of the copper, 
 which is the exposed metal. It is well known that 
 the zinc coating of galvanized iron wire is soon de- 
 stroyed near the sea-coast, and from the effects of 
 carbonic acid arising from the combustion of coal in 
 cities (137). Copper, under the same conditions, 
 remains wholly unimpaired. Many cases occur in the 
 construction of lines in which transportation is an item 
 of great expense. In such cases, wire of the same 
 or greater conductivity than galvanized iron, weighs 
 materially less, with no disadvantage whatever arising 
 from its lightness. 
 
 161. The following table exhibits the weight, size, 
 and relative strength of compound wires, equivalent in 
 conducting power to the ordinary sizes of iron wire 
 used in telegraphic construction. 
 
 1 
 
 6 
 
 8 
 
 f; 
 
 6 
 
 GALVANIZED IRON WIRE. 
 
 COMPOUND STEEL, AND COPPER WIRE. 
 
 Weight 
 per mile. 
 
 Relative 
 Strength. 
 
 Weiirht 
 per mile. 
 
 Relative 
 Strength. 
 
 Size of 
 Steel Core. 
 
 Size of 
 Compound. 
 
 313 
 375 
 449 
 525 
 
 2.9 
 2.9 
 2.9 
 2.9 
 
 99 
 112 
 121 
 
 147 
 
 4.9 
 4.6 
 44 
 4.5 
 
 16 
 16 
 16 
 15 
 
 14 
 14-1- 
 13- 
 12-
 
 106 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 
 
 The term relative strength, used in the preceding 
 table, is the quotient obtained by dividing the strain 
 which would break the wire by its weight per mile. 
 
 In constructing lines with the compound wire, much 
 care should be used in making the joints so as not to 
 separate the copper sheathing from the steel core, thus 
 allowing moisture to penetrate to the steel and oxidize 
 it. This may, however, be guarded against by care- 
 fully soldering the joints. 
 
 162. THE GRAVITY BATTERY. Several modifications 
 of the Daniell battery (19), especially adapted to tele- 
 graphic use, are finding much favor within the past few 
 years. The most economical and generally useful of 
 these improved forms is the gravity battery. The best 
 arrangement is that known as the Callaud. Another 
 combination very closely resembling it, and giving 
 nearly as favorable results, is known in this country as 
 the Hill battery. In these elements the porous cup of 
 the Daniell battery is entirely dispensed with, the two 
 
 FIG. 56. 
 
 solutions being prevented from mingling by the differ- 
 ence of their respective specific gravities. The zinc 
 plate of the Callaud element, in the form of a short 
 hollow cylinder, open at both ends, is suspended in the 
 upper portion of the containing jar, as shown in Fig. 
 56, by means of three hooks projecting from its upper 
 edge, resting upon the jar. A strip of copper rolled 
 into a spiral form is soldered to a copper wire covered 
 with gutta-percha, forming the positive pole and con- 
 necting it to the zinc of the next element.
 
 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 
 
 107 
 
 163. The manner of setting up this battery is as 
 follows : 
 
 A sufficient quantity of soft water is poured into 
 each jar to fill it to a point above the upper surface 
 of the zinc. The battery should now be placed in the 
 position which it is to permanently occupy, unless this 
 has been already done. After the connections are 
 made and everything in readiness, about three-quarters 
 of a pound of sulphate of copper in lumps of the size of 
 a hickory nut or larger, is dropped in, taking care that 
 it does not lodge upon the zinc. The solution of sul- 
 phate -of copper being of greater specific gravity, will 
 remain at the bottom of the jar. The battery, after 
 it is set up, should be kept on a closed circuit for 
 about twelve hours, when its resistance will have become 
 reduced so that the force will be available. As the bat- 
 tery continues in action, the sulphate of copper solu- 
 tion gradually becomes weaker and the zinc solution 
 stronger. It is therefore necessary from time to time 
 to add crystals of sulphate of copper, and to remove a 
 portion of the zinc solution and replace by water. A 
 good practical rule for maintaining this battery is to 
 always see that the stratum of liquid around and in 
 contact with the copper is kept of a blue color. The 
 formation of transparent crystals upon the zinc indi- 
 cates that the point of saturation of the zinc solution 
 has been reached and that it should be diluted with 
 water. A Baume hydrometer is very convenient for 
 determining the density of the zinc solution. The latter 
 should be maintained at from 20 to 30 in a main 
 battery, and from 15 to 25 in a local. 
 
 It often occurs in using this battery that stalactites 
 of copper attach themselves to the lower edge of the 
 zinc and hang suspended in the solution, slowly but 
 constantly increasing in length. These are first pro- 
 duced by a deposit of copper upon the zinc, which sets 
 up a local action followed by a rapid decomposition of 
 the solution and a further deposit of copper. These 
 should be removed by means of a bent wire and allowed
 
 108 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. . 
 
 to fall to the bottom of the jar, as they occasion a use- 
 less expenditure of sulphate. 
 
 Absolute quietude is essential to the proper per- 
 formance of this battery. A slight jar will cause the 
 solutions to mingle, and this effect will be followed by 
 a rapid deposition of metallic copper upon the zinc. 
 When the zincs are removed for cleansing, care must be 
 taken not to agitate the solution. 
 
 Prof. Hough, of the Dudley Observatory, has sug- 
 gested the use of sheet lead in the place of the copper 
 spiral, as it is cheaper and more readily cut and formed 
 into proper shape. There is no perceptible difference 
 in the electro-motive force or in the resistance of the 
 battery when lead plates are substituted for copper in 
 this way. 
 
 The electro-motive force of the gravity battery is 
 the same as the Daniell, and the average resistance 
 when in good working condition about three units. 
 
 164. SIEMENS' UNIVERSAL GALVANOMETER. The ap- 
 paratus employed for the measurement of electrical 
 resistances consists essentially of a standard resistance, 
 which is used for the purpose of comparison, a galva- 
 nometer, by which the result is indicated, arid a galvanic 
 battery. In the different methods of testing, these 
 appliances are arranged in various ways, as particular 
 circumstances may render convenient or desirable. 
 The various methods of testing in use may be classified, 
 however, under three heads, viz. : 
 
 1. By the angles of deflection of a galvanometer 
 needle. 
 
 2. By the differential galvanometer. 
 
 3. By the Wheatstone bridge, or electrical balance. 
 The first-named method is the simplest in principle, 
 
 and, with proper care, gives very accurate results. It 
 is not so convenient as the other two methods for ordi- 
 nary use, but is applicable more especially for the 
 measurement of very high resistances, such as insula- 
 tors, etc. It is also employed in measuring the inter- 
 nal resistance of batteries. As the strength of the
 
 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICK. 109 
 
 current passing through the coils of a galvanometer is 
 always proportionate to the sine or tangent of.the angle 
 of deflection of the needle, and is also inversely pro- 
 portional to the resistance in circuit, it follows that if 
 we find the deflection with a certain known resistance 
 in circuit to be only 22, and we then substitute for 
 this known resistance an unknown one, which gives us 
 a deflection of 39. the tangent of the latter will be 
 twice that of the former, and the unknown resistance 
 is consequently found to be half that of the known re- 
 sistance. (170.) 
 
 The second method is very convenient and is much 
 used, although not equal in strict accuracy to the third 
 method. The galvanometer coils are wound with two 
 wires of the same length and resistance, insulated from 
 each other with the utmost care. The needle is there- 
 fore surrounded by an equal number of convolutions of 
 each wire, which are also equidistant from it. One 
 end of each wire is connected to the battery, but in 
 such a manner that the current flows in opposite direc- 
 tions through the two wires. When, therefore, the two 
 currents are of equal strength, one tends to deflect the 
 needle to the right and the other to the left with equal 
 power, and the needle remains at rest. If we insert 
 an unknown resistance into the circuit of one of these 
 wires the current is weakened, as is also its effect on 
 the needle, which no longer remains balanced and at 
 rest, but is deflected to one side. If we now insert a 
 series of known resistances into the circuit of the other 
 wire, until the needle is again brought into equilibrium, 
 we are certain that the unknown resistance in one cir- 
 cuit is exactly equal to the known resistance in the 
 other. (122.) 
 
 The third method is susceptible of the greatest accu- 
 racy of measurement, when proper precautions are ob- 
 served. The connections of the "bridge" are arranged 
 as follows : 
 
 We will suppose the wires A B C D (Fig. 57), arranged 
 in the form of a parallelogram, to be of exactly equal
 
 110 
 
 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 
 
 resistance. If we attach the two poles of a battery, E, 
 to the points 1 and 2, its current will divide at 1, half 
 of it going through A B, and the other half going 
 through C D, to the point 2, and thence to the other 
 pole of the battery. The galvanometer Gr, placed on a 
 wire connected across from 3 to 4, will not be affected 
 as long as A B is equal to C D, no matter what the 
 absolute resistance may be. 
 
 Again, when A bears the same proportion to C that 
 B does to 1), or when A: C: : B: D, no current will 
 pass from 3 to 4 through the galvanometer. If the 
 resistance of A be made 10, that of B 1, of C 1,000, 
 
 FIG. 57. 
 
 and of D 100, the total resistance of A B will now be 
 11. and that of C 1,100 ; but the tension in each 
 branch will have fallen in the same proportion at the 
 points 3 and 4, and no current will pass between those 
 points. 
 
 If, therefore, we insert a known standard resistance 
 in the wire B, and an unknown one in D, and divide a 
 given resistance between A and C until we get no effect 
 upon the galvanometer needle, we are then certain that 
 the resistance of A bears the same proportion to that 
 of B as the known resistance does to the unknown one 
 D, which may be readily calculated by proportion or 
 the "rule of three." 
 
 It is not necessary, of course, that the wires should 
 be arranged in the exact form shown, nor in fact is it
 
 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. Ill 
 
 often done, but the principle is more easily explained 
 and remembered when thus arranged. 
 
 165. The Universal Galvanometer of Dr. Werner 
 Siemens is constructed upon the principle of the Wheat- 
 stone bridge, just described, but its connections are so 
 arranged that it may be used when desired for the 
 method of deflections first mentioned. 
 
 The galvanometer is mounted upon a disk of slate 
 about six inches in diameter. A groove in the edge of 
 this disk, extending about half way round the circum- 
 ference, contains a wire of considerable resistance, 
 which corresponds to the wires A and C in the above 
 diagram. A small platina roller, mounted upon a 
 radial arm, is connected to one pole of the battery, and 
 forms the connection with the wire A C, as shown at 1 
 in the diagram. The wire corresponding to B is sup- 
 plied with three standard resistances of 10, 100, and 
 1,000 Siemens' units, respectively, either of which may 
 be placed in circuit at pleasure, by means of contact 
 plugs. The wire D is provided with binding screws for 
 the attachment of the wire, or other resistance which 
 it is required to measure. The galvanometer consists 
 of a pair of very delicate astatic needles, suspended by 
 a fine silk fibre. The coil has a resistance of 1 00 Sie- 
 mens' units. 
 
 The radial arm carrying the platina roller also car- 
 ries a pointer or index, moving over a scale upon the 
 circumference -of the slate disk, which is divided into 
 300 degrees, and which may be read to one-fifth of a 
 degree by means of a vernier. 
 
 In using the instrument, the standard resistance cor- 
 responding most nearly to the unknown resistance 
 which is to be measured is unplugged and placed in 
 circuit at B (Fig 57), while the unknown resistance 
 itself is inserted at D. The radial arm carrying the 
 platina roller 1 is now moved towards A or C, until 
 the needle is balanced. The proportion of A to C is 
 then read off the scale, from which the proportion of B
 
 112 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 
 
 to D is readily calculated, or is taken from a printed 
 table furnished with the instrument. 
 
 This galvanometer may also be employed for com- 
 paring electro-motive forces, according to the method 
 of Poggendorff,* and is applicable to almost any pur- 
 pose for which an apparatus of the kind may be re- 
 quired. 
 
 This instrument usually has a constant of about four 
 degrees, with one Danieli's cell through 1,000,000 Sie- 
 mens' units. When used as a Wheatstone bridge, its 
 range of measurement is from O.L7 to 59,000 Siemens' 
 units. Higher resistances, such as insulators, may be 
 measured by the method of deflections. The entire 
 apparatus (except the battery) occupies a space only 
 nine inches in diameter, and the same in height. It is 
 packed in a neat case, and can be carried about with 
 great convenience. 
 
 166. POPE & EDISON'S PRINTING TELEGRAPH. Type- 
 printing telegraph instruments, which were formerly 
 employed for commercial telegraphing, have, within 
 two or three years, been extensively introduced, in a 
 modified and simple form, in the various branches of 
 private telegraphy, with great success. One of the 
 best of these is that of Pope <fe Edison, which is shown 
 in Fig. 58. 
 
 The different portions of the apparatus, with the 
 exception of the battery, are mounted upon a small 
 table, similar in size and construction to that of an 
 ordinary sewing-machine. At the back of the table 
 are six binding screws to which are attached the line 
 and ground wires, and the wires leading to the main 
 and local batteries. The instrument operates upon 
 what is known as the " open circuit principle," each 
 station transmitting with its own main battery the 
 line at the receiving station being connected directly 
 through the relay to the ground without the interven- 
 tion of a second battery. 
 
 * See Clark's '-Electrical Measurement," p. 105. Also Sabine's "Elect 
 Tel.,' 1 p. 320.
 
 
 I 
 
 a: 
 
 ; 
 
 H
 
 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 113 
 
 The printing apparatus is placed upon a circular 
 iron base in the centre of the table. In front of it is 
 placed a dial containing the letters of the alphabet, 
 arranged in a circle and provided with an index or 
 pointer, mounted upon a horizontal shaft. This shaft 
 also carries a type wheel, with the letters of the alpha- 
 bet engraved upon its periphery, and a scape-wheel, 
 with rachet-shaped teeth, corresponding in number to 
 the characters upon the type wheel and dial. An 
 electro-magnet beneath the base is provided with an 
 armature, attached to a vibrating lever, the latter 
 armed with pawls or clicks, so arranged in relation to 
 the scape-wheel that every time the electro-magnet 
 attracts its armature, the wheel is made to revolve a 
 distance of one tooth, and the type wheel and index 
 upon the same shaft a distance of one letter. At the 
 extreme right of the circular base, and partly beneath 
 it, as seen in the engraving, is placed a second electro- 
 magnet, whose armature lever passes in a horizontal 
 direction below the type wheel. Directly underneath 
 the type wheel an india-rubber pad is fixed upon the 
 lever, by means of which an impression of the letter 
 which is opposite it upon the type wheel may be taken 
 in the manner hereafter to be described. This lever is 
 also provided with a simple mechanical device for 
 moving the paper forward the proper distance, as the 
 impression of each successive character is imprinted 
 upon it. This may be seen at the left of the printing 
 apparatus. The type wheel is provided with a suitable 
 inking roller, as shown in the engraving. 
 
 It will thus be understood that the printing mechan- 
 ism is operated by two distinct electro-magnets, one 
 of which is so arranged that its successive pulsations 
 may be made to advance the index step by step to 
 any required letter, while the other forces the strip 
 of paper against the inked type upon the wheel, after 
 it has been moved to the proper position by the first 
 magnet. The type wheel is, of course, so arranged in 
 reference to the index upon the same shaft, that when
 
 114 RECENT IMPROVEMENTS IX TELEGRAPHIC PRACTICE. 
 
 the latter points to any given letter the correspond- 
 ing letter upon the type wheel is opposite the impres- 
 sion pad. 
 
 These two electro-magnets are placed in the circuit 
 of a local battery, which is brought into action by a 
 relay placed in the main line circuit, as in the ordinary 
 Morse apparatus. The relay is shown at the right of 
 the printing mechanism, covered by a small glass 
 shade. It is the same in principle as the ordinary 
 Morse relay, with the addition of a device termed 
 the "polarized switch," which consists of a perma- 
 nently magnetized steel bar, pivoted between the poles 
 of the relay magnet, and forming a part of the local 
 circuit. This is attracted to the right or left accord- 
 ing to the polarity of the relay magnet, which itself, 
 in turn, depends upon the direction of the electrical 
 current in the main circuit. The polarized switch 
 determines the direction of the local circuit, causing it 
 to pass through the magnet for moving the type 
 wheel, or through the impression magnet, as may be 
 required. 
 
 Two lever finger keys, with vulcanite knobs, are 
 placed on each side of the printing apparatus, as 
 shown in the engraving ; and it is by means of these 
 that the instrument is operated. They are connected 
 to opposite poles of the main battery in such a man- 
 ner that, by depressing the right hand key, the posi- 
 tive pole of the battery is connected, through the relay 
 magnet to the line, and the negative to the ground, 
 while the left hand key, on the contrary, sends a neg- 
 ative current through the relay and line in the same 
 manner. 
 
 The mode of operating the instrument is exceed- 
 ingly simple. By depressing the right hand key a 
 sufficient number of times in rapid succession, a series 
 of positive currents is sent through the relays at both 
 ends cf the line, which are repeated upon the local 
 circuits of both instruments. The positive currents 
 deflect the polarized switches to the left, so that the
 
 RECENT IMPROVEMENTS IN TELEGRAPHIC PRACTICE. 115 
 
 local circuit is directed into the type-wheel magnet. 
 The index and type wheel of both instruments, there- 
 fore, advance one letter every time the key is de- 
 pressed, and they may thus be readily brought to any 
 desired letter. When this has been done, the left hand 
 key is depressed, which sends a negative current, 
 reversing the polarized switch, and the local circuit 
 is directed through the printing magnet, producing 
 the impression of that letter upon the strip of paper, 
 and this process may be continued indefinitely. 
 
 Suitable arrangements are provided for bringing the 
 type wheels of the two instruments together in case 
 they should accidentally be thrown out of correspond- 
 ence. 
 
 These instruments are entirely automatic in their 
 action, and a despatch may be printed at the remote 
 end of the line, in the absence of an attendant. In the 
 event of any derangement of the printing apparatus, it 
 may be used as a dial instrument as conveniently as if 
 especially constructed for that purpose. 
 
 The battery is always disconnected, except at the 
 moment of working, and therefore is consumed but 
 slowly. Other systems require the battery to be con- 
 stantly connected to the line whether working or idle. 
 A battery of two carbon cells per mile, and in many 
 cases even less, will work the instrument and remain 
 in action front one to four weeks without renewal, 
 according to the amount of telegraphing done upon 
 the line. 
 
 It is impossible for the main circuit to be acciden- 
 tally left open. Only one adjustment that of the 
 tension spring of the relay is required after the 
 instrument is first put in operation, and that but rarely 
 on lines of ordinary length.
 
 CHAPTER!. 
 
 APPENDIX AND NOTES. 
 
 167. THE EQUIPMENT OF TELEGRAPH LINES. The 
 satisfactory performance of any given telegraphic cir- 
 cuit depends largely upon the maintenance of a proper 
 relation between the respective resistances of the line, 
 instruments, and batteries. There is in all cases an as- 
 certainable definite proportion between these, which 
 gives, theoretically, the best result with the least ex- 
 penditure ; to which practice should always be made to 
 approximate as nearly as possible. The disregard of 
 the well-established laws of electrical and magnetic 
 action is not only the source of grave difficulties in the 
 practical operation of lines, but also entails an enor- 
 mous waste of material and supplies. 
 
 It is one of the fundamental laws of the electric cir- 
 cuit, that with a given resistance of conducting wire and 
 battery, the maximum magnetic force is developed when 
 the. total resistance of the coils of the electro- magnet or 
 magnets is equal to the resistance of the other portions of 
 the circuit, i. e., the batteries and conducting wires. (173.) 
 
 The resistance of the conductor, which must of ne- 
 cessity, always form a large proportion of the total 
 resistance in every main circuit, is in practice deter- 
 mined within certain well-defined limits, by considera- 
 tions of distance, mechanical construction, and first 
 cost. It therefore becomes necessary to adjust the 
 resistance of the remaining parts of the circuit with 
 reference to that of the conductor, which in practice 
 usually ranges from 10 to 20 units per mile. With the
 
 APPENDIX AXD NOTES. 
 
 117 
 
 No. 9 galvanized iron wire generally used, it approxi- 
 mates closely to the latter figure. 
 
 The resistance of the batteries forms but a very small 
 portion of the total resistance in an ordinary main cir- 
 cuit, and admits of comparatively little variation, so 
 that the actual problem which presents itself, is to deter- 
 mine the proper resistance of the relays when the 
 resistance of the conductor is given, and the form of 
 battery which will supply the necessary electrical power 
 for operating the line with the least expenditure of 
 materials and labor. 
 
 The size of the conductor having been fixed upon, 
 this taken in connection with the length will determine 
 its total resistance. The combined resistance of the 
 relays should be made to equal this amount as nearly 
 as possible. It is hardly necessary to add that the re- 
 sistance of the different relays should be uniform in 
 respect to each other. With good rekys the amount 
 of battery required to operate the main circuit should 
 not exceed 1 cell of Grove or Carbon battery for each 
 150 units resistance, and will generally be less than 
 this. About double this number of the Daniell, Hill, 
 or Callaud battery will be needed. 
 
 For example, suppose it is required to construct a 
 telegraph line 300 miles in length, with 15 stations. 
 If No. 9 iron wire is used as a conductor its resistance 
 will be say 300 X 20 = 6000 units. The resistance of 
 all the relays being made equal to that of the line, we 
 have as the proper resistance for each relay - 6 yf = 400 
 units. The amount of battery required will be -f{j-- 
 =80 cups of Grove or Carbon, or about 160 cups of 
 Daniell, Hill, or Callaud. 
 
 The approximate average resistance, and compara- 
 tive electro-motive force of the different batteries in 
 use is as follows, the Grove battery being taken as the 
 standard at 100 : 
 
 Electromotive 
 Resistance. force. 
 
 Grove 5 units. 100 
 
 Bi-Chromate or Carbon 10 " 107 
 
 Danii-11 2.0 " 56 
 
 Callaud .. 3.0 " 56
 
 118 
 
 APPENDIX AND NOTES. 
 
 These figures refer to the ordinary sizes of the Grove 
 and Carbon battery, and to the Daniell and Callaud 
 when adapted to a jar eight inches high and six 
 inches inside diameter. Although the resistance of the 
 battery when included in a single main circuit of the 
 usual length, has but little influence upon the effec- 
 tive strength of the current as a whole, yet in 
 local circuits, and in main batteries from which a 
 number of lines are worked at the same time (110), 
 it becomes an essentially important element in the 
 calculation. 
 
 Another important law of electrical action, which 
 applies especially to instruments which are to be worked 
 by a local circuit, is the following : 
 
 The greatest effective force of any given battery is 
 developed when the sum of all the external resistances 
 in the circuit is equal to the internal resistance of the 
 battery. 
 
 In a local circuit there are practically no resistances 
 except those of the battery and magnet, and it is there- 
 fore obvious that these should be so adjusted as to equal 
 each other as nearly as possible. Tested by this rule, a 
 great portion of the sounders, registers, and repeaters, 
 in use in this country, will be found to have magnets 
 of too low resistance, most of them being adapted to 
 the use of a local of 1 Grove cell, although nearly all 
 the local batteries in use are composed of 2 or "6 cells 
 of Daniell. Such a magnet will only partially develop 
 the effective force of a Daniell battery, and still less 
 that of a Callaud or Hill. 
 
 The sizes of copper wire generally used in local 
 helices vary from No. 19 to 22, American gauge, and 
 the resistance from 0.5 units to 4 units. The most 
 usual resistance is about 1 unit. If we take a sounder 
 of this resistance and apply a cell of Grove battery, we 
 have the following result : 
 
 Bcsistance of magnet 1 unit. 
 
 " " battery 1 " 
 
 Total... .. 2 "
 
 APPENDIX AND NOTES. 119 
 
 Calling the electro-motive force 100, and dividing 
 this by the resistance, we get 50 as the effective strength. 
 If we take the same sounder and apply a Daniell ele- 
 ment with 2 units resistance the total resistance will be 
 3, the electro-motive force 56, and the quotient or effec- 
 tive force 18.6, but little more than one-third that of 
 the Grove. With 2 Daniell cells we have 
 
 Resistance of magnet 1 unit. 
 
 " " battery t 4 " 
 
 Total ~5 " 
 
 The electro-motive force of 2 cells will be 56 x 2 = 
 112, and dividing this by the resistance, 5, we have 
 22.4. With 2 Callaud cells the effect would be still 
 less, in fact only 16. 
 
 Now let us take the same sounder, and remove the 
 helices of No. 19 wire, which give a resistance of 1 
 unit, and rewind them with No. 23 wire, and observe 
 the effect. With a given strength of current, the mag- 
 netic effect is proportional to the number of convolu- 
 tions, and the latter increase inversely as the square of 
 the diameter of the wire. The resistance of the wire 
 also increases as its length, and inversely as the square 
 of its diameter. The squares of the respective diame- 
 ters would be as follows : 
 
 No. 19 00128381 
 
 " 23 00051076 
 
 The average length of each convolution in a helix 
 of a given size will be the same with any sized wire. 
 The length being in inverse proportion to the square 
 of the diameter, the resistance due to the increased 
 length will be 
 
 .00051076 : .00128881 : : 1 unit : 2.52 units. 
 
 But the resistance is further increased in inverse pro- 
 portion to the square of the diameter of the wire, there- 
 fore 
 
 .00051076 ; .00128881 : : 2.52 : 6.3
 
 120 APPENDIX AND NOTES. 
 
 6.3 units would, therefore, be the resistance of the 
 new helices. This is not strictly accurate, as no 
 allowance has been made for the spaces between the 
 convolutions, which occupy more room in the coil 
 when finer wire is used, and somewhat reduce the 
 number of convolutions as well as the length and resist- 
 ance of the wire. We will, therefore, call the resist- 
 ance of the new helices 6 units. This resistance will 
 give the greatest possible effect obtainable with 2 Gal- 
 laud cells, which will be as follows : 
 
 Resistance of magnet 6 units. 
 
 " battery. 6 " 
 
 Total resistance... 12 " 
 
 Divide the electro-motive force 112 
 
 = 9.3 
 
 By the total resistance 12 
 
 But the magnetic effect is increased by the greater 
 number of convolutions in the proportion of the 
 squares of the diameters, or as 2.52 to 1. Therefore 
 9.3 x 2.52 = 23.43. This is greater than the magnetic 
 effect of 2 Daniell cells upon the sounder of 1 unit 
 resistance, which we before found to be 22.4. Making 
 some deduction for the slight decrease in the number 
 of convolutions, owing to the greater number of spaces, 
 we may consider the actual magnetic effect to be the 
 same in both cases. Experience has shown that this is 
 amply sufficient to operate a well-constructed sounder 
 or register. 
 
 In the above calculations the resistance of the Daniell 
 is given as 2 units. It is actually over 3, except when 
 the porous cell is defective, or so excessively porous as 
 not to separate the liquids properly. The Callaud is 
 also given as 3 units, but in point of fact does not ex- 
 ceed 2 after it has been 2 weeks in use. The resist- 
 ance of the different Callaud cells is very uniform, 
 while cells of the ordinary form of Daniell will often 
 vary widely under precisely similar conditions. Some- 
 times one cell will measure 10 units, and another
 
 APPENDIX AND NOTES. 121 
 
 only 2, owing principally to difference in the quality 
 of the porous cups. A cell of high resistance will 
 diminish instead of increasing the effect in a local 
 circuit. 
 
 The obvious advantage of using the Callaud battery 
 for local circuits in connection with a magnet whose 
 resistance is properly adjusted to it, consists in its great 
 economy, the expense of maintenance not being more 
 than one-fifth as great as when the ordinary Daniell 
 is employed. The above calculations show that a 
 great saving can be made when the Daniell itself is 
 used, by regulating the resistance of the magnets to cor- 
 respond with that of the battery. 
 
 1 68. THE WORKING CAPACITY OF TELEGRAPH LINES. 
 In order to secure the best possible result in the work- 
 ing of telegraph lines we must keep down the resist- 
 ance of the conductors in the circuit (42), and increase 
 the resistance of the insulation (90) to the greatest 
 practicable extent. In other words, the resistance must 
 be as small as possible in the route we wish the electric 
 current to travel, and as great as possible in every 
 other direction. The practical working value of a tele- 
 graph line is the margin between the joint resistance of the 
 conductor and the insulation, and that of the insulation 
 alone. The tension of the retracting spring of the 
 relay armature, when upon a "working adjustment," 
 is the measure of this margin or difference. It is evi- 
 dent that this margin may be increased in two ways, 
 viz. : 
 
 1. By increasing the insulation resistance. 
 
 2. By decreasing the resistance of the conductor. 
 
 For example, suppose a line of telegraph 100 miles 
 in length the weather being rainy. Suppose that the 
 conductor has a resistance of 20 units per mile, while 
 the resistance of the insulators is 1,000,000 units per 
 mile. Let the receiving magnet and battery be situ- 
 ated at one extremity of the line and the key at the 
 other. When the key is closed, the force acting upon
 
 122 APPENDIX AND NOTES. 
 
 the armature of the magnet is in proportion to the 
 quantity of electricity leaving the battery and passing 
 through the magnet to the line, and this quantity is 
 made up of that escaping through the insulation along 
 the line, in addition to that going through the con- 
 ductor to the other end of the route. When the key is 
 open, the force exerted upon the armature is due to the 
 current passing through the insulation alone. The 
 effective working strength is therefore the difference 
 between the attractive forces acting upon the armature, 
 when the key is opened, and when it is closed at the 
 other end of the line or, in other words, the working 
 margin is the difference between the sum of the forces dv# 
 to the joint conductivity of the wire and insulators and that 
 of the insulators alone (104). 
 
 Thus, in the case cited : 
 
 The total resistance of the wire is 2,000 units. 
 
 " insulation 10,000 " 
 
 The joint resistance of wire and insulators is 1,666 " 
 
 The strength of current being inversely proportional 
 to the resistance, it will be as follows : 
 
 When key at other end is closed 100.00 
 
 " " open 16.66 
 
 Difference, or effective working margin. 
 
 It is not the absolute resistance of the conductor or 
 of the insulators that determines the value of a line. 
 It is operated by the marc/in or difference between these 
 two values (101). It is important that this should not 
 be lost sight of. 
 
 Now let us observe the effect of substituting a wire 
 of twice the weight, having a resistance of only 10 
 units per mile. We now have : 
 
 Total resistance of wire 1,000 units. 
 
 '' " insulation (as before')..'...'...".. 10,000 " 
 
 Joint resistance... 909 "
 
 APPENDIX AND NOTES. 
 
 123 
 
 The proportionate strength of current will become 
 
 When key is closed 100.00 
 
 " "" open 9.09 
 
 Difference 
 
 We have given the strength of current with key 
 closed as 100 iu both the above cases, in order to show 
 the proportionate increase of margin. The absolute 
 strength of current in the two cases is as 100 to 183, 
 an increase of 83 per cent., while the increase of work- 
 ing margin is only 9 per cent. 
 
 We will now take the result of an actual measure- 
 ment. A new No. 9 galvanized wire, 1L5 miles in 
 length, on a clear and fine day, gave a resistance of 
 2,400 units, or about 21 units per mile. On the same 
 poles was a No. 10 plain wire, which had been in use 
 nineteen years. This wire, including eight instruments 
 in circuit, gave a resistance of 13,300 units. In a rain 
 the insulation resistance of the good wire measured 
 15,300 units, and the bad wire 19,650. 
 
 The joint resistance of the good wire and its insula- 
 tors was 2,077. The proportion of current escaping 
 by the insulators was to the whole current as 13.51 to 
 100, giving a margin to work on of 86.49. 
 
 The joint resistance of the bad wire and its insula- 
 tors was 7,982. The proportion of escape to the 
 whole current was as 40 to 100, giving but 60 percent, 
 as an available working margin. This wire could not 
 be worked except when the other circuits on the same 
 poles remained idle, either closed or open. The good 
 wire was worked without difficulty. The escape was 
 apparent, but was not sufficiently great to cause any 
 serious inconvenience. The relative working margins 
 were in the proportion of 86.49 to 60. 
 
 On a clear and cold day the insulation of the good 
 wire showed a resistance of 2,400,000 units, the work- 
 ing margin being 99.99. The bad wire showed an 
 insulation resistance of 1,700,000 units, the working 
 margin being 99.93. The difference in this case
 
 124 APPEXDIX AXD NOTES. 
 
 between the two wires was only 00.06, an amount not 
 appreciable in practice. The poor wire worked as well 
 as the good one, but the current was not so strong. 
 This difference could be compensated for by increasing 
 the battery on the former. 
 
 In the above instance we have two wires on the 
 same poles. One is new and a good conductor, the 
 other old and a poor conductor. In fine weather the 
 insulation of the new wire is the most perfect, but the 
 difference in their working is inappreciable. In rain, 
 although the insulation of the old wire is actually 
 the best, yet it does not work nearly so well as 
 the new wire, and this is attributable solely to the 
 fact that the new wire has a much greater conductive 
 capacity. 
 
 Take another example, also from actual measure- 
 ment : A new wire, 150 miles in length, on a clear 
 day gave a resistance of 2,200 units. On the same 
 poles was an old rusty No. 11 wire, which gave a re- 
 sistance of 23,500 units. On a very wet day the insu- 
 lation resistance of the new wire was 4,800 units, and 
 of the old wire 32,000 units. The working margin of 
 the new wire was 78, and that of the old wire 60. In 
 this case the amount of current escaping over the 
 insulators of the new wire was 2.7 times that passing 
 through the old wire and its insulators combined ! In 
 other words, the current with key open on the new 
 wire was nearly three times as strong as on the old 
 wire when the key was closed. 
 
 In these examples the resistance of the batteries and 
 instruments has not been taken into account, as they do 
 not materially affect the results. 
 
 169. THE ELECTRICAL TENSION OF TELEGRAPHIC BAT- 
 TERIES AND LINES. In another part of this work (8) it 
 was briefly stated that the electrical tension of a battery, 
 or its power of overcoming resistance, is increased in 
 direct proportion to the number of elements of which 
 the battery consists. Suppose we have a battery of 
 100 cells, and the electro-motive force of each element
 
 APPENDIX AND NOTES. 125 
 
 of this battery be such as to produce a difference in 
 tension between its plates equal to 1, the difference 
 between its poles or end plates will be equal to 100. 
 But it must be understood that degrees of tension are 
 only relative or comparative. The earth being our 
 great reservoir of electricity, its tension is called zero, 
 and it affords us a convenient standard of reference in 
 comparing other tensions, but even the absolute tension 
 of the earth sometimes varies in different times and 
 places. 
 
 Suppose we take the battery of 100 cells above 
 referred to, place it upon a well-insulated stand, and con- 
 nect one pole of it, say the zinc or negative pole, to 
 earth, and leave the other pole disconnected, and there- 
 fore insulated by the air. The end which is connected 
 with the earth being in free communication with it, -will 
 now have a tension of zero, and the opposite end of the 
 battery will have a tension of 100 positive, or above 
 that of the earth, and if a wire were connected from it 
 to the earth a powerful current of electricity will pass 
 between them. 
 
 If now the copper or positive pole be placed to the 
 earth, and the zinc pole insulated, the tension of the 
 former will now be zero, and that of the latter 100 
 negative, or below that of the earth. In each of these 
 cases the degree of tension is the same, but in one case 
 it is above that of the earth, or positive, and in the other 
 case below that of the earth, or negative. 
 
 If the zinc or negative pole of the same battery be 
 now connected to the earth, and the positive pole, in- 
 stead of being left free, is connected by a short and 
 thick wire, of no appreciable resistance, to the negative 
 pole, the tensions throughout the circuit will be 
 materially changed, although the electro-motive force 
 will remain unaltered. The tension at the copper 
 pole of the battery, which was 1,000 when the pole was 
 entirely disconnected, now becomes the same as that 
 of the earth, or at least but very little above it. If a 
 wire offering considerable resistance be substituted for
 
 126 APPENDIX AND NOTES. 
 
 the short and thick wire which connects and Z, the 
 tension at C will be raised, although that of Z will still 
 be kept at zero by its connection with the earth at that 
 point. In proportion as the resistance of this connect- 
 ing wire is increased, the tension at C rises until, when 
 the resistance becomes infinite, the tension will again 
 reach 100, for infinite resistance is absolute insulation. 
 The tension is now equal to the electro-motive force, 
 but it is obvious that it can never exceed it under any 
 circumstances. 
 
 If a battery of 100 cells is connected to a telegraph 
 line of 100 miles in length, whose insulation is perfect, 
 and which is not connected to the earth at the remote 
 end, the line will instantly acquire a tension of 100 
 throughout its whole length (this being equal to the 
 electro-motive force of the battery), and this would oc- 
 cur if the wire were a thousand or a million times that 
 length. After the line has acquired the same tension 
 as the pole of the battery to which it is attached, no 
 current will flow from the battery. 
 
 If the distant end of the line is connected to the 
 earth, the battery will come into action, and a current 
 of electricity will pass through it. This will at once 
 change the tensions throughout the whole line. The 
 distant end of the line, which originally had a tension 
 of 100, will now have a tension of zero, being con- 
 nected directly to the earth, and from this point the 
 tension will rise gradually and regularly along the 
 whole length of the line to the pole of the battery. 
 So also the tensions within the cells of the battery 
 itself follow the same law. 
 
 The relation existing in a voltaic circuit between the 
 resistances, electro-motive forces, and tensions, may be 
 graphically and accurately represented to the eye by a 
 geometrical projection based upon mathematical reason- 
 ing, a method first suggested by Ohm, and more 
 recently elaborated by Mr. F. C. Webb, and which he 
 explains as follows : 
 
 Let all the parts of a circuit; whether liquid or solid,
 
 APPENDIX AND NOTES. 127 
 
 be expressed in their successive order by portions of a 
 continuous horizontal line, which shall be to one another 
 as the reduced lengths or resistances of those parts. 
 Let the tension at any given point in the circuit be 
 represented by the perpendicular height of a point 
 above, or depth below, the horizontal line representing 
 the resistances. This when above the line will indi- 
 cate a positive, and when below, a negative tension. 
 The horizontal line of resistances may be termed the 
 axis. 
 
 In order to represent the tension at every point in 
 the circuit, we must construct a line termed the line of 
 tension. The perpendicular height of this line above 
 the axis at any point, indicates a corresponding positive 
 tension at that point, and its depth below in the same 
 manner indicates a negative tension. When this line 
 crosses the axis the point of intersection has no tension. 
 
 Electro-motive force consists in a sudden and con- 
 stant difference in the tension of the points situated 
 immediately upon opposite sides of the surface of 
 junction between the zinc element and the liquid of 
 the battery. The electro-motive forces in the circuit 
 must, therefore, be represented by a sudden rise in the 
 line of tension at the points along the axis at which 
 they occur, thus forming lines perpendicular to the 
 axis. The magnitude of these lines must be propor- 
 tional to the electro - motive force they represent. 
 Moreover, as the electro-motive force is a quantity 
 depending solely upon the nature of the elements at 
 the surface of junction at which it occurs, and not at 
 all on any change in the resistance or electrical state 
 of the circuit, these perpendicular lines constantly 
 maintain the same magnitude, although their posi- 
 tion as regards the axis may be altered in various 
 ways. 
 
 Now let us construct a diagram which shall correctly 
 represent the electro-motive forces, tensions, resist- 
 ances, and strength of current, as a telegraph line with 
 a closed circuit, having a battery of three cells at each
 
 128 APPENDIX AND NOTES. 
 
 end of the line, which will be a sufficient number to 
 correctly represent the arrangement of the circuit or- 
 dinarily used on American telegraph lines. 
 
 Let the horizontal line N P' (see Fig. 59) represent 
 the axis, or line of resistances, the latter being repre- 
 sented in their respective order, beginning at the point 
 of contact, N, between the extreme zinc plate of the 
 battery and the liquid of the cell. N B, B C, and C 
 P represent the respective internal resistances of the 
 three battery cells, and N P that of the entire battery. 
 Let P H N' represent the resistance of the line wire, 
 and N' P' that of the battery at the opposite end of 
 the line. Erect a perpendicular, N E, at the point N, 
 and divide it into three portions, N F, F Of, and G E, 
 which shall be to each other as the electro-motive 
 forces at N, B, and C. The other battery, N' P', having 
 its negative pole, N', to the line, will give a negative 
 tension; therefore a perpendicular P' E' let fall below 
 the axis from the point P, and divided in the same 
 manner, will represent the electro-motive forces of the 
 battery N' P'. Therefore the line N P' represents the 
 sum of all the resistances, and N" E + P' E' the sum of 
 the electro-motive forces. It necessarily follows 
 that the line of tension, M H M', which we get by 
 joining E and E', varies in the angle of its inclination 
 to the axis according to the proportion between the 
 sum of the electro-motive forces, N" E and P' E', and
 
 APPENDIX AND NOTES. 
 
 129 
 
 the sum of the resistances, N P'; and the degree of its 
 inclination will therefore accurately represent the 
 effective working strength of the current in all parts of 
 the circuit. 
 
 The varying tensions within the battery maybe cor- 
 rectly represented as follows : Having joined JEand E', 
 erect perpendiculars at B and C and P. Now as the 
 effective strength of current, represented by the incli- 
 nation of the line E E', is the same at every point 
 throughout the whole circuit, draw F I parallel to E E'. 
 Then F I will be the line of tension in the first cell, 
 falling regularly through the resistance of the liquid to 
 the surface of generation, B, of the second zinc, where 
 it rises suddenly to the extent of the electro-motive 
 force there situated. Draw Gr K parallel to E E', inter- 
 secting B at J. I J will then be equal to F Gr, 
 which represents the electro-motive force at B, and J K 
 will be the line of tension in tne second cell. Now as 
 G K is parallel to E E', K L will be equal to Gr E, the 
 electro-motive force at C, and L M will be the line of 
 tension in the third cell. In the same manner the line 
 of tension within the other battery N P'. 
 
 The terminal points of the line N and P', being con- 
 nected directly with the earth, their tension will be 
 equal, and the same as that of the earth, which is 
 assumed to be zero ; that is, neither positive nor neg- 
 ative. It is manifest that at the point II, midway of 
 the circuit where the line of tension crosses the axis, 
 the tension is the same as that of the earth, or zero. 
 
 In the illustration given, the line is supposed to be 
 in a condition of perfect insulation. In actual practice 
 there isaleakage at every support throughout the whole 
 length of the circuit. The line of tension in this case 
 would form a double catenary curve, its angle of incli- 
 nation to the axis constantly increasing from H to M 
 and M', because in an imperfectly insulated or leaky 
 line the current continually increases in strength in each 
 direction from the neutral point to the battery poles 
 atP andN'.
 
 130 APPENDIX AN'D NOTES. 
 
 Mr. Webb has demonstrated the correctness of the 
 
 ", above method of geometrical projection by applying 
 
 Ohm's formula for obtaining the tension at any point 
 
 \ of the circuit. The results are found to correspond in 
 
 every case. This formula may bo stated as follows : 
 
 Let T = the tension at any given point of the circuit a;. 
 
 Y = the abscissa of that point y, taking as origin the point of 
 
 least tension. 
 
 A = (he sum of the electro-motive forces. 
 L = the reduced leugth or resistance of the entire circuit. 
 O = the sum of the electro-motivo forces included in Y. 
 C = the tension of the whole circuit to external objects. That 
 
 is to say, the tension of the circuit, if it be an insulated 
 
 circuit, uud electrified by a source not contained within 
 
 it. 
 
 Then T == ~ Y - + C. 
 
 J_J 
 
 As, in the case under consideration, the earth forms 
 part of the circuit, the constant C disappears and the 
 formula becomes 
 
 Now take a point x in the diagram, and the tension 
 x x' will be found to agree with the formula. 
 
 The quantities in the formula are thus represented 
 geometrically in the figure : 
 
 A = NE 
 
 O = x' x" 
 T^xx' 
 
 Now since the triangles H N E and H x x" are sim- 
 ilar, we have 
 
 N H : N E : : n x \ xx" 
 
 Consqnently x x" = ^-7, H x, 
 .M H 
 
 and J K being parallel to L, we have 
 
 a' x" = K L. 
 But x x = x x" - x' x" ; 
 
 Therefore xx' = ^-r. H X - x" x", 
 
 Or, T = Y - O. 
 
 L
 
 APPENDIX AN1> NOTES. 
 
 131 
 
 An experimental proof of the above theory of ten- 
 sion may be obtained by connecting a wire from the 
 neutral point in the middle of 'the closed circuit of- a 
 telegraph line, and inserting a galvanometer or relay. 
 It will be found that no current passes between the 
 line and the earth, which proves that the electric ten- 
 sion or potential at that point is zero, or the same as, 
 that of the earth itself. 
 
 170. DOUBLE TRANSMISSION. One of the most inte- 
 resting problems in practical telegraphy is that of double 
 transmission, or working in opposite directions at the 
 same time over a single wire. This apparently para- 
 doxical result may be accomplished in several different 
 ways, the principles involved being very simple arid 
 easily understood. The method shown in the accom-; 
 paiiying diagram is that of Siemens & Halske, of Ber- 
 lin, Prussia ; the apparatus now used in this country 
 differing slightly from it in some of its minor details. 
 
 Fia. 
 
 A and B (Fig. 60), are the two terminal stations of 
 the line. The main battery E, at station A, is placed 
 with its -f , and the battery E' at station B with its
 
 132 APPENDIZ AND NOTES. ) 
 
 pole to the line, as represented. M and M' are the 
 receiving magnets or relays, which are wound through- 
 out with two similar wires of equal length, as shown in 
 the figure, whose connections will hereafter be explained. 
 The rheostat or resistance, X, must be adjusted so as to 
 be exactly equal to that of the line A, B, added to that 
 of the relay wire 7, 5, at the other station. Similarly 
 X' is also made equal to the line including the relay 
 wire 3, 1. 
 
 If, now, the key K at station A be depressed, the 
 current from the battery E will divide at the point 1, 
 one portion going through the relay coils to 3, over the 
 line A, B to 7, and thence through the relay M' to 5, 
 key lever 6'. and contact C' to the earth at G', and the 
 other portion in an opposite direction through the relay 
 coils from 2 to 4, and thence through the resistance X 
 to the negative pole of the batter} 7 . These two cur- 
 rents will be equal to each other, the resistance being 
 the same by each of the two routes, as before explained, 
 but as they pass in opposite directions through tb.o two 
 wires surrounding the relay M, they produce no mag- 
 netic effect upon it. The relay at B, however, will be 
 affected by the current coming from A through the 
 wire 7, 5, and will give signals corresponding to the 
 movements of the key at that station. 
 
 If, now, the key at B be also depressed, the same 
 action takes place ; one half the current passes over 
 the line, combining with the current from A, and the 
 other half returns to the battery through the other 
 Wire of the relay and the rheostat. 
 
 The relay wires 1, 3 and 7, 5 are now traversed by 
 the double current, equal to 5 + 5, but the wires 2, 4 
 and 6, 8 are traversed only by the current of a single 
 battery, having at A the force of and at B the force of 
 j. The latter current being in the opposite direction to 
 the former, the relays at both stations are affected by 
 the difference in the forces of these currents, the relay 
 at A by (J+J) - J, and the relay at B by (J+5) - .
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 133 
 
 Thus each station receives its signal through the action 
 of the distant battery only. 
 
 In the arrangement shown in figure 60 a third posi- 
 tion occurs, where one of the keys, at B for instance, 
 is in the act of changing from the front contact A' to 
 the rear contact C', or vice versa, in which case the cur- 
 rent from A is interrupted at B', and therefore passes 
 through the second wire of the relay 6, 8, but this time 
 in the same direction, and thence through the rheostat 
 X' to the ground. The current arriving at B is con- 
 siderably weakened in consequence of the additional 
 resistance encountered at X', but this is compensated 
 for by its passing through both wires of the relay M in 
 the same direction, and its action upon the relay, there- 
 fore, remains about the same as before. 
 
 One slight difficulty, however, arises in this connec- 
 tion. It will be seen that when the current at the 
 receiving station is thus momentarily thrown through 
 both relay wires and the rheostat, it must necessarily 
 cause an unequal division of the current between the 
 two opposing relay wires at the sending station, as the 
 resistance of the long circuit becomes about double that 
 of the short one. This effect is avoided in the Ameri- 
 can system by a modification of the transmitting appa- 
 ratus, which is operated by the lever of a sounder placed 
 in a local circuit in connection with the key. When 
 the local circuit is closed the downward movement of 
 the sounder lever makes the battery connection upon 
 a flat spring, and the movements thus imparted to the 
 spring breaks the earth contact. The spring being at- 
 tached to the line wire the connection is necessarily 
 always complete, either direct or through the battery, 
 and it is not obliged to pass through the rheostat when 
 the transmitter is changing from the battery to the earth 
 contact, or vice versa. The disadvantage in this case 
 arises from the fact that the main battery is thrown on 
 short circuit at each movement of the transmitter, ren- 
 dering it necessary to interpose a considerable addi- 
 tional resistance between the back contact and the bat-
 
 134 APPENDIX AND NOTES. V' = 
 
 tery, to prevent the rapid consumption of the latter 
 which would otherwise ensue. These improvements 
 "were devised by Mr. J. B. Stearns. 
 
 In working this system, it is necessary to keep the 
 rheostat so adjusted that its resistance will correspond 
 exactly with that of the line, as above shown. If the 
 relay works too feebly the counter current must be 
 weakened by increasing the resistance of the rheostat. 
 If the magnetism is too strong the resistance should be 
 diminished. A careful study of the diagram will show 
 that this system operates equally well, whether similar 
 or opposite poles of the two batteries are placed to- 
 wards the line. With like poles the action will be as 
 follows: 
 
 If the key at A be depressed, the current on the 
 line will be \ and through the rheostat , neutralizing 
 each other upon the relay of A, but giving a current 
 of g in the relay at B. Now, if the key at B be also 
 depressed, a current equal to f is thrown through each 
 wire of his relay, but the current being equal and 
 opposite to the current of the main line will 0. 
 
 The current through the second wire of the relays 
 being still unaffected, each relay will give a signal cor- 
 responding to the time the key at the other station is 
 depressed. 
 
 171. EDISON'S BUTTON REPEATER. This is a very 
 simple and ingenious arrangement of connections for a 
 button repeater, which has been found to work well in 
 practice. It will often be found very convenient in 
 cases where it is required to fit up a repeater in an 
 emergency, with the ordinary instruments used in 
 every office. Fig. 61 is a plan of the apparatus. 
 
 M is the western and M' the eastern relay. E is the 
 main battery, which, with its ground connection G, is 
 common to both lines. E' is the local battery, and L 
 the sounder. S is a common " ground switch," turn- 
 ing on two points, 2 and 3. In the diagram the switch 
 is turned to 2, and the eastern relay, therefore, repeats 
 into the western circuit, while the western relay ope-
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 135 
 
 rates the sounder, the circuit between 1 and 2 through 
 
 the sounder and local battery being common to both 
 
 the main and local currents. If the western operator 
 
 e breaks the relay 
 
 WEST 1 
 
 E -S- 
 
 M opens, and con- 
 
 sequently the soun< 
 dcr, L, ceases tp 
 work. The opera- 
 tor in charge then 
 turns the switch to 
 3, and the reverse 
 operation takes 
 place; the westera 
 relay repeats into 
 the eastern circuit, 
 and the eastern 
 relay operates the 
 sounder. The soun- 
 der being of coarse wire, offers but a slight resistance to 
 the passage of the main current. 
 
 172. BRADLEY'S TANGENT GALVANOMETER. The com^ 
 mon galvanometer used for the measurement of elec- 
 tric currents consists of a magnetized steel needle, 
 suspended in the centre of a hollow frame covered with 
 insulated copper wire. The degree of deflection of this 
 needle from its normal position in the magnetic meridian, 
 when a current is passing, indicates the strength of the 
 current. In the ordinary galvanometer, however, the 
 angle through which the needle is moved, or in other 
 words, the number of degrees over which it passes, is not 
 .an accurate measure of the strength of the current when 
 the deflection exceeds 15, for the further the needle 
 moves from a position parallel to the wires of the coil 
 the more nearly does it approach a right angle, in whicji 
 position the effect is null, so that the action of the cur- 
 rent upon it becomes less and less powerful as the de- 
 viation increases. Several arrangements have been 
 tried in order to obviate this objection, the most com- 
 mon being that of a ring having a groove on its edge
 
 APPENDIX AND NOTES. 
 
 filled with wire. The needle is hung precisely in the 
 centre of the ring, and must not be longer than one 
 sixth of its diameter a half inch needle requiring a 
 three inch ring. The needle is then deflected with a 
 force varying as the tangent of the number of degrees 
 through which the needle moves. Owing to the great 
 distance of the coil from the needle, this arrangement 
 has very little sensitiveness compared with the common 
 galvanometer. 
 
 In Bradley 's Galvanometer a compound needle is 
 employed, composed of several needles of thin, flat 
 steel, fixed horizontally upon a light flat ring of metal, 
 forming a complete circular disc of needles, having an 
 agate cup in the centre, to rest upon the pivot upon 
 which it moves. At each extremity of the meridian 
 light points project, to indicate the degrees of deflection. 
 This compound needle, after having been magnetized, 
 is placed within or over a coil whose breadth is exactly 
 equal to the diameter of the disc. This compound cir- 
 cular needle, being under the influence of the same 
 number of convolutions of the coil in all its deflections, 
 fulfils the required conditions for a true tangent gal- 
 vanometer. 
 
 The theorem, " The intensity of currents, as measured 
 by the tangent galvanometer, is proportional to the tangents 
 of the angles of deflection" may be verified in the fol- 
 lowing manner : 
 
 Call the terrestrial magnetism, whose tendency is to di- 
 rect the galvanometer needle to the magnetic meridian, 
 the unit of directive force, and let this unit be represented 
 geometrically by the line A M (Fig 62), which is the 
 radius of the circle M B M the line M A M representing 
 the meridian. When there is no other force acting on the 
 needle its direction is with the meridian. Now let an 
 electric current be sent through the galvanometer coil, 
 whose directive force is precisely equal to the terrestrial 
 force, and whose tendency is to direct the needle in 
 a line perpendicular to the meridian, and let this force 
 be represented by the line A B.
 
 MODERN PRACTICK OP TUB ELECTRIC TELEGRAPH. 
 
 137 
 
 If the terrestrial force could now, for a moment, be 
 suspended, the needle would point due east and west ; 
 
 but the combined action of 
 the two equal forces will 
 direct the needle toward 
 the point of intersection of 
 the line drawn perpendic- 
 ularly from M, and that 
 drawn horizontally from B, 
 at 1, which direction cuts 
 the quadrant at 45, the line 
 M 1 being the tangent of 
 45, which is 1. 
 
 Now, if we augment the 
 intensity of the current 
 through the coil to twice 
 its present force, which will 
 be 2, and will be represen- 
 ted by the line A C, the 
 combined forces A M and 
 A C will direct the needle 
 toward the point 2. If we 
 now lay a protractor on the 
 circle, we find that the line A 2 cuts it about 63 30', of 
 which the tangent is 2. 
 
 We may increase the parallelogram erected upon A 
 M at pleasure, and the two forces combined will 
 always so balance the needle between them as to make 
 it point from A, diagonally, across the parallelogram 
 to its opposite angle, the height of which is the tangent 
 of the angle of deflection. 
 
 By inspection of the diagram it is seen that the law 
 holds good in the subdivisions of the force A B, as at 
 .5 .25 and .125, a truth admitted by all experimenters, 
 as to the relations, up to 14. 
 
 173. THOMPSON'S REFLECTING GALVANOMETER. This 
 is the most delicate apparatus of this kind which has 
 yet been devised, and is for this reason employed in 
 operating the Atlantic Cables. 
 
 FIG. 62.
 
 138 APPENDIX AND NOTES. 
 
 The special feature which distinguishes this galvan- 
 ometer from an ordinary one, is the extreme lightness 
 of the magnet or needle, and the delicacy with which 
 it is suspended in a horizontal position. Instead of an 
 index needle, to render the motions of the magnet visi- 
 ble to the eye, a reflected ray of light is made use of, 
 which, of course, can be made of any required length. 
 This arrangement is of great practical value in mea- 
 suring faint electrical currents, too feeble to be indicated 
 by any other apparatus. It is especially valuable in 
 submarine telegraphing, because it permits the use of 
 such extremely low battery power. 
 
 When the insulation of a cable is in the slightest 
 degree defective at any point, a current of intensity 
 has a tendency to aggravate the fault, and to corrode 
 and eat away the conductor by chemical decomposi- 
 tion, at the point where the escape occurs, finally des- 
 troying the communication altogether. 
 
 Fig. 63 is a side elevation of this instrument, show- 
 ing a section through the galvanometer coils and the 
 outer case containing them. Fig. 64 is a cross section 
 through the coils, showing the magnet, technically 
 termed the needle. Similar letters refer to like parts 
 in both figures. The magnet A is a small bar of steel, 
 one half inch in length and one tenth of an inch square, 
 cemented to the back of a very thin circular glass mir- 
 ror, a. The mirror is suspended in a brass frame, B 
 (Fig. 64), by an exceedingly delicate silk fibre, and is 
 adjusted in height by the screw b. This frame slides 
 into a vertical groove left in the centre of the coil, 
 dividing it into two parts. The coil and mirror are 
 enclosed in the brass case D, this case having pieces of 
 glass let in wherever necessary, to permit the passage 
 of light. The object of this arrangement is to pre- 
 vent the mirror and its attached needle from being dis- 
 turbed by currents of air. 
 
 A narrow pencil of luminous rays from the lamp, E, 
 passes through the opening, F, which is capable of ad- 
 justment by the slide G-. This pencil of light, passing
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 139 
 
 through the lens, is reflected by the mirror back through 
 the lens upon an ivory scale at I, as shown by the dot- 
 ted lines. The scale is horizontal, extending to the 
 
 right and left of the centre of the instrument, the zero 
 point being exactly opposite the lens. The luminous 
 pencil is brought to a sharp focus upon the scale by a
 
 |40 APPENDIX AND NOTES. 
 
 sliding adjustment of the lens M, in the tube N. When 
 the needle is at rest in its normal position, and no cur- 
 rent is passing, the spot of light which serves as an in- 
 dex will remain at zero on the scale. 
 
 The operator reads the signals from a point just in 
 the rear of the magnet and coils, the light of the lamp 
 being cut off by the screen Y, so that he only sees the 
 small luminous slit through which the light enters the 
 instrument, and a brilliantly denned image of the slit 
 upon the white ivory scale just above, which is kept in 
 deep shadow by the screen Y. A very minute dis- 
 placement of the magnet gives a very large movement 
 of the ray of light on the scale I, the angular dis- 
 placement of the ray of light being double that of the 
 needle. 
 
 It is obvious that the ray of light from the needle 
 will be reflected to the right or left of zero on the scale, 
 according as the deflection is produced by a positive or 
 negative current. The Morse alphabet is used for sig- 
 naling through the Atlantic cable, deflections on one 
 side of zero indicating dots, and on the other side 
 dashes. 
 
 It will be observed that the end, and not the broad 
 part of the flame of the lamp, is presented to the slit 
 F, which is also arranged to receive the brighest part of 
 the vertical section of the flame. 
 
 The galvanometer coils, E, consist of many thousand 
 convolutions of fine insulated copper wire, arid they 
 are insulated from the case, D, by a disc of hard rub- 
 ber, T, to which they are fastened. 
 
 The instrument is usually provided with a directing 
 magnet, by which its sensitiveness may be varied to a 
 great extent. This magnet is in the form of a bar, 
 slightly curved, and is of considerable power. It is 
 placed upon a vertical rod passing through its centre, 
 which is fixed above the coil immediately over the 
 needle, in such a manner that it can be turned horizon- 
 tally so as to follow the movements of the needle, or 
 be removed nearer to or further from it vertically. If
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 141 
 
 it is placed with its south pole over the north pole of 
 the needle, it will add its directive force to that of the 
 earth, and by holding the needle more powerfully in 
 its position, will lessen its sensitiveness. The nearer 
 the magnet approaches the needle the greater will be 
 its power over it, and it can be arranged so as to hold 
 the needle in any desired position. If it is placed in a 
 reverse direction, so as to repel the needle instead of 
 attracting it, it will lessen the attractive force of the 
 earth so as to increase its sensitiveness, and in a cer- 
 tain position will render the galvanometer astatic. 
 When the magnet is too near the needle it repels to 
 the full extent of the scale. If it is raised upon the 
 supporting rod the repelling effect will decrease, until, 
 at a certain distance from the magnet, the spot of light on 
 the scale can be held at zero. The greatest sensibility 
 is obtained at the point at which the slightest lowering 
 of the magnet upon the rod will again repel the needle 
 to the full extent of its swing. 
 
 An improvement in this instrument, made by Mr. C. 
 F. Varley, consists in giving the mirror a concave form, 
 silvered upon the back, and thus dispensing with the 
 use of the lens above described. 
 
 174. MODE OF WORKING TOE ATLANTIC CABLES. 
 Yery little has been made public in regard to the pre- 
 cise method employed in signaling through the Atlantic 
 cables. As before remarked, the reflecting galvanome- 
 ter is employed as a receiving instrument, and by em- 
 ploying deflections on one side of zero to represent 
 dashes, and those on the other side dots, the Morse 
 alphabet is found to answer the purpose admirably. It 
 is said that the two cables have been looped in a metallic 
 circuit without ground connection, arid that they have 
 also been worked separately witlr and without conden- 
 sers. The latter method is made use of in order to 
 avoid the disturbances generated by what arc known 
 as " earth currents." 
 
 Different parts of the earth and sea are found to be 
 at different electric potentials. One part is electro-
 
 142 APPENDIX AND NOTES. 
 
 positive or electro-negative to another. That is to saj*, 
 there is the same difference between the two parts of 
 the earth that exists between the two poles of a bat- 
 tery. If, therefore, these two points are joined by a 
 wire, a current will flow through that wire as if from a 
 battery, and this current is termed an earth current, to 
 distinguish it from the current generated by an ordi- 
 nary voltaic battery. This difference of potential be- 
 tween two given points, such as Newfoundland and 
 Valencia, is not constant but continually varies, causing 
 a corresponding variation in the current it produces. 
 This current and its fluctuations interfere with the sig- 
 naling current, disturbing the distinctness of the sig- 
 nals. When very rapid changes take place in the elec- 
 tric condition of the earth, it is known as a magnetic 
 storm, and this occasionally interferes with the work- 
 ing of all telegraph lines. 
 
 By the method of working with condensers the dis- 
 turbances from this cause are avoided. The condenser 
 is constructed of alternate layers of tin foil and thin 
 plates of mica, gutta-percha or paper, saturated with 
 paraflBne, arranged like the leaves of an interleaved 
 book. Each alternate metal plate is connected so as to 
 form two distinct series, insulated from each other, one 
 of which is connected with the line and the other with 
 the earth. By an inductive action, similar to that of 
 the well known Leyden jar, a quantity of electricity, 
 in proportion to the amount of surface exposed, may be 
 accummulated or stored up upon the metallic plates. If, 
 therefore, one series of plates be charged with positive 
 electricity .the other series will become negative by 
 induction, and by means of this induction a much 
 larger quantity of electricity may be accumulated than 
 would otherwise be the case. 
 
 The manner in which the condenser is made use of ia 
 working a cable is as follows : 
 
 The sending apparatus consists of a battery, B (Fig. 
 G5), which is permanently connected with the cable 
 through the back contact of a Morse key, K, and the
 
 MODERN PRACTICE OP THE ELECTRIC TELEGRAPH. 
 
 143 
 
 CABLE 
 
 cable is therefore kept constantly charged from this 
 batter}-. When the key is depressed the cable is 
 placed in connection with the earth at E. The receiv- 
 ing apparatus consists of the reflecting galvanometer 
 G (1G3), one terminal of which is attached to the cable 
 and the other to one series of plates in the condenser 
 
 C the other series 
 
 |0 beingconnectcd with 
 
 the earth, as shown 
 in the figure. R is: 
 a very high resist- 
 ance, inserted in a 
 wire leading from 
 the point 0, between 
 the cable and the 
 galvanometer, so as 
 to allow a very slight but constant leakage from the 
 cable to the earth. The cable is, therefore, charged to 
 the tension of the battery B, and the condenser to a 
 tension equal to that of the point but owing to the 
 high resistance at R the tensions are nearly the same. 
 Upon charging the cable with the battery at K a charge 
 of electricity enters the cable, and a quantity sufficient to 
 charge the condenser passes through the galvanometer, 
 deflecting the mirror until the condenser is charged 
 equal to the tension of the point when the mirror 
 will return to zero. By putting the cable to earth at 
 K a portion of the charge will be withdrawn, and the 
 tension of the point lowered below that of the con- 
 denser. A portion of the charge of the latter, there- 
 fore, flows into the cable, deflecting the galvanometer in 
 the opposite direction. The right and left hand deflec- 
 tions necessary for signaling are therefore produced with- 
 out reversing the currents, or rendering it necessary to 
 entirely discharge tho cable after each signal. This 
 mode of signaling possesses many important advan- 
 tages over the old method, in point of rapidity of action 
 and freedom from interference by earth currents. The 
 rate of working through the cable by expert operators
 
 144 APPENDIX AND NOTES. 
 
 is said to average from fifteen to twenty words per 
 minute. 
 
 175. VELOCITY OF ELECTRIC SIGNALS. For many 
 years the velocity of electric signals in passing through 
 a conductor was supposed to be infinitely great, or at 
 least so great as to be incapable of measurement. In 
 1849, Professor Sears C. Walker, of the United States 
 Coast Survey service, while engaged in measuring 
 longitude by means of the electric telegraph, discovered 
 a perceptible retardation. Experiments between Wash- 
 ington and St. Louis indicated a velocity not far from 
 16,000 miles per second. Some of the measurements 
 were as low as 11,000 miles per second. On the even- 
 ing of the 28th of February, 1868, a number of experi- 
 ments were made by the officers of the Coast Survey, 
 for the purpose of determining accurately the difference 
 in longitude between Cambridge, Mass., and Sari Fran- 
 cisco, Cal. A wire was connected from Cambridge to 
 San Francisco and back, embracing thirteen repeaters 
 the whole distance thus traversed by the signals being 
 about 7,000 miles. 
 
 The following table shows the time, in hundredths of 
 a second, occupied by a signal in passing from Cam- 
 bridge to each of the repeating stations and back. The 
 number of repeaters in circuit is also given : 
 
 TIME OF TRANSMISSION FROM CAMBRIDGE. 
 
 Seconds. 
 
 To Buffalo and Return - 0.10 1 Repeater. 
 
 " Chk-ago " 0.20 3 
 
 " Om. ha " 0.33 5 
 
 " Salt Lake " 0.54 9 
 
 " Virginia City " 0.10 11 
 
 " San Fraucisco " 0.7413 
 
 The actual time of transmission from Cambridge to 
 San Francisco and back was estimated not to exceed 
 three tenths of a second, the "armature times" of the 
 thirteen repeaters probably amounting to four or five 
 tenths of a second. 
 
 In submarine cables the velocity of signals is con- 
 siderably less than upon air lines. Prof. Gould, in his
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. \^ 
 
 experiments upon the Atlantic Cable, found it to ba 
 between 7,000 and 8,000 miles per second being 
 greater when the circuit was composed of the two 
 cables, and less when the earth formed a part of the 
 circuit. His experiments seemed to show that, instead 
 of travelling around the entire circuit in one direction, 
 the electric wave, or polar influence, travelled both 
 ways from the battery, and the signal was received 
 when the two influences met. Experiments made on 
 air lines indicate that an instrument placed at the cen- 
 tral point of resistance between the two poles of the 
 battery will record the signal sooner than when placed 
 in any other part of the circuit, it being understood 
 that the two terminal batteries of a telegraph line are 
 in effect but one, being connected by the earth, which is 
 a conductor of infinitely small resistance. 
 
 176. SPEED OF TRANSMISSION. The average rate of 
 transmission, by the most skilful operators upon the 
 Morse apparatus, is about 1,800 words per hour. ;This 
 has been considerably exceeded, however, by many 
 operators within the past two or three years. On tho 
 evening of January 28th, 1868, 2,520 words of Press 
 news were sent from New York to Philadelphia in one 
 hour, and legibly copied by the receiving operator, 
 without a stop or break the average rate being forty- 
 two, and the maximum rate forty-six words per minute. 
 On the 7th of February following 2,630 words of Press 
 news were sent from Milwaukee, Wis., to St. Paul, Minn., 
 in one hour, the distance being about 400 miles. On 
 the 19th of the same month 1,352 words of Press news 
 were sent from New York to Philadelphia in thirty 
 minutes, the average rate being over forty-five words 
 per minute. 
 
 This is believed to be the quickest time on record 
 which has been made in the transmission of regular 
 business by the Morse system. The receiving opera- 
 tor, in all the above cases, copied entirely from the 
 sound of the instrument. 
 
 The speed of the printing instrument exceeds that
 
 146 
 
 APPENDIX AND NOTES 
 
 of the Morse under favorable circumstances. On the 
 24th of September, 1867, the Combination instrument 
 transmitted from Albany to New York 1,453 words of 
 Press news in thirty-three minutes. It is claimed that, 
 on some occasions, as many as 2,900 words per hour 
 have been transmitted by the House instrument. 
 
 177. COMPARISON OF WIRE GAUGES. The different 
 sizes of wire employed for telegraphic and other pur- 
 poses are designated by a series of arbitrary numbers. 
 The system known as the Birmingham gauge is the one 
 in most general use at the present time, but is objec- 
 tionable, both on account of the irregularity of its gra- 
 dations and the absence of any authorized standard 
 wire of the same number from different makers often 
 varying considerably in its size. The American gauge 
 is formed upon a geometrical progression, and it is to be 
 hoped will eventually supersede the old gauge : it is 
 already employed to a considerable extent.* The fol- 
 lowing table gives the diameter, in thousandths of an 
 inch, of each number in the American and Birmingham 
 gauges : 
 
 TABLE OF DIAMETERS OF "WIRES. 
 
 Kumber. 
 
 American 
 Gauge. 
 
 Birmingham 
 Gauge. 
 
 Number. 
 
 American 
 Gauge. 
 
 Birmingham 
 Gauge. 
 
 0000 
 
 .460 
 
 .454 
 
 19 
 
 .03589 
 
 .042 
 
 000 
 
 1 .40964 
 
 .425 
 
 20 
 
 .OIJI9G 
 
 .035 
 
 00 
 
 .36480 
 
 .380 
 
 21 
 
 .02846 
 
 .032 
 
 
 
 .32495 
 
 .340 
 
 22 
 
 .0253"3 
 
 .028 
 
 1 
 
 .28930 
 
 .300 
 
 23 
 
 .02257 
 
 .025 
 
 2 
 
 .25763 
 
 .284 
 
 24 
 
 .0201 
 
 .022 
 
 3 
 
 .22942 
 
 .259 
 
 25 
 
 .0179 
 
 .020 
 
 4 
 
 .20431 
 
 .238 
 
 26 
 
 .01591 
 
 .018 
 
 5 
 
 .iai94 
 
 .220 
 
 27 
 
 .01419 
 
 .016 
 
 I 
 
 .16202 
 
 .203 
 
 28 
 
 .01264 
 
 .014 
 
 1 
 
 .14428 
 
 .180 
 
 29 
 
 .01126 
 
 .013 
 
 8 
 
 .12849 
 
 .165 
 
 30 
 
 .01002 
 
 .012 
 
 9 
 
 .11443 
 
 .148 
 
 31 
 
 .00893 
 
 .010 
 
 10 
 
 .10189 
 
 .134 
 
 32 
 
 .00795 
 
 .009 
 
 11 
 
 .09074 
 
 .120 
 
 33 
 
 .00708 
 
 .008 
 
 12 
 
 .08081 
 
 .109 
 
 34 
 
 .one:; 
 
 .007 
 
 13 
 
 07196 
 
 .095 
 
 35 
 
 .00561 
 
 .005 
 
 14 
 
 .06408 
 
 .083 
 
 36 
 
 .005 
 
 .004 
 
 15 
 
 .05707 
 
 .072 
 
 37 
 
 .00445 
 
 .... 
 
 16 
 
 .05082 
 
 .065 
 
 38 
 
 .00396 
 
 '..'.'. 
 
 17 
 
 .04526 
 
 .058 
 
 39 
 
 .00353 
 
 .... 
 
 ... 18 
 
 .0403 
 
 .049 
 
 40 
 
 .00314 
 
 
 This gauge is manufactured by Darling, Brown & Sharpe, of Providence, E. I.
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 
 
 147 
 
 178.' USEFUL FORMULAE FOR WEIGHT ANI> RESISTANCE 
 OF WIRES. The following formulae, from Clark's tables-, 
 will be found convenient in telegraphic work : 
 
 The weight of any iron wire, per statute mile of 52SO 
 feet, is T-IVir Ibs. ; c? 2 denoting the square of the diame: 
 ter of the wire in" mils " or thousandths of an inch. 
 
 The conductivity of ordinary galvanized iron wirej 
 compared with pure copper 100, averages about 14, or 
 about one seventh that of pure copper. 
 
 The resistance per statute mile of a galvanized iron 
 wire is about IMS*", o hms a t 00 Fahr. 
 
 The resistance of iron wire increases about .35 per 
 cent, for each degree, Fahr. 
 
 The weight per statute mile of 5280 feet, of any cop 
 per wire, is ^/^ Ibs. A mile of No. 16 wire weighs 
 in practice from 63 to 66 Ibs. 
 
 The resistance per statute mile of any pure copper 
 wire is ^^r- 2 ohms at 60 Fahr. No. 16 copper wire 
 of good quality has a resistance of about 19 ohms. 
 
 The resistance of any pure copper wire I inches in 
 length, weighing n grains, ^JL!l ohms. 
 
 The resistance of copper increases as the temperar 
 hire rises, .21 per cent, for each degree, Fahr. 
 
 The conductivity of any copper wire is obtained by 
 multiplying its calculated resistance by 100, and divi- 
 ding the product by its actual resistance. Pure copper 
 is taken as 100. 
 
 179. CONDUCTING POWERS OF MATERIALS. According 
 to the experiments of Mr. M. Gr. Farmer, made some 
 years since, the relative electrical resistance of differ- 
 ent metals and fluids at ordinary temperatures is as fol- 
 lows, pure copper being taken as 100 : 
 
 Silver ' 
 
 98 
 
 Zinc '' 
 
 ... 370 
 
 Gold ' . .. 
 
 1.13 
 
 IJrass " 
 
 3.88 
 
 
 5 63 
 
 
 11.30 
 
 Lead ' 
 
 .. .. 10.76 
 
 Nickel " 
 
 7.70 
 
 
 50.00 
 
 
 2.61 
 
 Palladium W ire 
 
 5.50 
 
 Aluminum " .... 
 
 1.H 
 
 Platinum " . 
 
 . 6.78 
 

 
 148 
 
 APPENDIX AND NOTES. 
 
 : ; His experiments with fluids gave the following 
 results : 
 
 Pure Rain Water 40,653.723,00 
 
 Water, 12 parts ; Sulphuric Acid, 1 part 1,305.467.00 
 
 Sulphate Copper, 1 pound per gallon 18,450,00'.0< 
 
 Saturated solution of common salt 3,173.000.00 
 
 " " of sulphate of zinc 17.330.000,00 
 
 Nitric Acid, 30 B 1,606,000,00 
 
 > The following table gives the specific resistance in 
 ohms of various metals and alloys, at 32 Fahr., 
 according to the most recent determinations of Dr. 
 Matthiessen : 
 
 , | vj, : NAMS or MKTAIA 
 
 Resistance 
 of wire 1 
 foot long, 
 weighing 
 1 grain. 
 
 Resistance 
 of wire 1 
 foot long, 
 1- 1000th 
 inch in 
 diameter. 
 
 Approximate 
 per cent, 
 variation in 
 resistance 
 per decree 
 t-mpt'ratura 
 at 20 degrees. 
 
 Silver annealed 
 
 * )0 14 
 
 9 936 
 
 0377 
 
 " hard drawn 
 
 ''421 
 
 9 151 
 
 
 
 
 9718 
 
 388 
 
 
 2106 
 
 9 940 
 
 
 
 5849 
 
 12 52 
 
 365 
 
 
 5950 
 
 19 74 
 
 
 
 068 <> 2 
 
 17 72 
 
 
 Zinc pressed 
 
 57] 
 
 32 22 
 
 365 
 
 
 
 55 09 
 
 
 Iron annealed 
 
 1 2425 
 
 59 10 
 
 
 
 1 0785 
 
 75 78 
 
 
 
 1 317 
 
 80 36 
 
 365 
 
 
 3 236 
 
 119 39 
 
 387 
 
 
 18 746 
 
 600 00 
 
 072 
 
 Platinum silver alloy, hard or annealed, used 
 for standard resistance coils 
 
 4 43 
 
 148 35 
 
 031 
 
 German silver, hard or annealed, commonly 
 used for resistance coils 
 
 2 652 
 
 127 32 
 
 044 
 
 Gold silver alloy, 2 parts gold, 1 part silver, 
 
 2 391 
 
 66 10 
 
 og5 
 
 
 
 
 
 The use of this table is as follows : Suppose it is 
 required to find the resistance at 32 Fahr. of a con- 
 ductor of pure hard copper, weighing 400 Ibs. per knot. 
 This is equivalent to 460 grains per foot. The resist- 
 ance of a wire weighing one grain is found by the table 
 to be 0.2106, therefore the resistance of a foot of wire 
 weighing 460 grains will be ^J-f 5 , but the resistance of
 
 VODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 140 
 
 one knot will be 6087 times that of one foot, therefore 
 the resistance required will be 6087 4 Y 8 '- !L = 2.79 ohms. 
 If the diameter of the wire be given instead of its 
 weight per knot, the constant is taken from the second 
 column. Thus the resistance at 32 Fahr. of a knot of 
 pure hard drawn copper wire 0.1 inch in diameter 
 would be ~~ = 6.05. The resistance of wires is 
 materially altered by annealing them, and a rise in 
 temperature increases the resistance of all metals. Dr. 
 Matthiessen found that for all pure metals the increase 
 of resistance between 32 and 212 Fahr. is sensibly 
 the same. The resistance of alloys is much greater 
 than the mean of the metals composing them. They 
 are very useful in the construction of resistance coils. 
 
 The highest value which has probably been found 
 for the conducting power of pure copper is sixty times 
 that of pure mercury, according to Sabine. Commer- 
 cial copper may be considered of good quality when 
 its conducting power is over fifty. Different samples 
 of copper vary greatly in their specific conductivity, 
 as may be seen by the following table, which gives the 
 result of careful determinations by Dr. Matthiessen, 
 the conducting power of pure copper at 59.9 Fahr. 
 being taken as 100. 
 
 take Superior, native, not fused 98.3 at 50 9 
 
 fused (commercial) 92.6 at f,9 
 
 Burr.iBurrn 88.7 at 67.2' 
 
 Best sck-eted 81.3 at 57.5 
 
 Biigl.t copper wire 72.2 at ".2 
 
 Tough copper 71.0 at G3 1 
 
 Dem -doff 59.3 at 54.8 
 
 Kio Tiiito 1 i.2 at 58.6 
 
 Thus Rio Tinto copper possesses no better conduct-, 
 ing power than iron. This shows the great importance 
 of testing the conductivity of the wire used in the 
 manufacture of electro-magnets, cables, etc. 
 
 180. INTERNAL RESISTANCE OF BATTERIES. This may 
 be measured by the sine or tangent galvanometer. 
 Place the battery to be measured in circuit with a sine 
 galvanometer giving a certain deflection. Insert resist- 
 ance till the sine of the deflection becomes half what
 
 150 
 
 APPENDIX AND NOTES. 
 
 it originally was. The total resistance of the circuit 
 is now doubled, and the resistance added is, therefore, 
 equal to the original resistance. Deduct the resistance 
 of the galvanometer and connections from the resist- 
 ance added, and the remainder is the resistance of the 
 battery. 
 
 " Second Method* Let D = the deflection obtained 
 with the battery in circuit with a galvanometer whose 
 deflections arc proportional, and some resistance r; 
 and d the deflection with some larger resistance li (the 
 resistance of the galvanometer being included in II and 
 r\ and let x = the resistance of the battery. 
 
 Then D: d :: P. -i- x : r + x 
 
 and * = 11- r> ~ P *_L> 
 
 ii D d 
 
 - In using this method any other resistance y may be 
 included with x, and the formula becomes 
 
 '.', (d y R)- (D x r) , 
 
 D d, 
 
 and by deducting x we get the value of y, or if y be 
 large in comparison with x, the latter may be neglected. 
 By this method one resistance r may be compared with 
 another. 
 
 The approximate resistance of the batteries in com- 
 mon use is as follows, according to Mr. Farmer : 
 
 ftrove 0.41 ohms 
 
 - ''~ Carbon O.C t " 
 
 Daniell 1.70 " 
 
 181. ELECTRO-MOTIVE FORCE OF DIFFERENT BAT-" 
 TERIES. The following table gives approximately the 
 electro motive force of various batteries, being the 
 mean of numerous observations taken on a sine galvan- 
 ometer by Mr. Latimcr Clark. f The electro-motive 
 force of batteries is within certain limits very variable, 
 depending on a variety of undetermined causes. It {3 
 not much affected by temperature. 
 
 Clark, Eedrical Measurement, p. 100. \ Electrical Measurement, p. 108.
 
 MODERN VUACTICE OF THE ELECTRIC TELEGRAPH. 151 
 
 Grove's. 100 
 
 Carbo-. with bi-chromate solution 107 
 
 Daniell's 5G 
 
 Smee's (when not ia action) 57 
 
 " (when iu action) about 25 
 
 Copper and zinc in acid (Wollaston) 46 
 
 Sulphate mercury and graphite (Marie Davy) 76 
 
 Chloride silver 62 
 
 Chloride lead 30 
 
 When connected on short circuit, the electro-motive 
 force of several of the batteries, especially Smee's and 
 Wollaston 's, will fall off 50 per cent, or more, owing to 
 the formation of hydrogen on the negative plate. 
 Grove's and Daniell's do not so fall off, because tho 
 hydrogen is reduced by the nitric acid in one case and 
 by the oxygen in the other. 
 
 182. MEASUREMENT OF ELECTRO-MOTIVE FORCE.* 
 When a number of cells are joined up in circuit with, 
 .but in opposition to, a number of other cells with a 
 galvanometer inserted, by adjusting the number of 
 cells so that no current passes, the relative electro- 
 motive force of the two batteries may be determined. ' 
 
 Second Method. Call the electro-motive forces of the 
 two batteries E and E'; join them up successively in 
 circuit with the same galvanometer, and by varying 
 the resistance, cause them both to give the same de- 
 flection ; their forces will then be in direct proportion 
 to the total resistances in circuit in each case, or 
 
 - I X 
 
 where E represents the resistance with E (including 
 that of battery, galvanometer, and the adjustable re- 
 sistance) and R' with E'. 
 
 183. FORCES OF ELECTRO-MAGNETS. The laws which 
 govern the forces of electro-magnets have been investi- 
 gated by Lenz, Jacobi and Miiller. 
 
 Let M = the magnetic force of the electro-magnet 
 
 n the number of convolutions of wire. 
 
 d = the diameter of the soft iron core. 
 
 Q = tho quantity of electricity in circulation, 
 and c a constant multiplier. 
 
 Then M = c n Q V d. 
 
 * Clark, Electrical Measurement, p. 103.
 
 152 : "'Vs* APPENDIX AND NOTES. 
 
 This law only holds good for bars of iron whose 
 length is considerably greater than their diameter, for 
 feeble currents of electricity, and under the supposi- 
 tion that the number of convolutions of wire is not so 
 great as materially to diminish the influence exerted 
 by the outer coils upon the bar of iron. These condi- 
 tions are fulfilled in the electro-magnets used for tele- 
 graphic purposes. 
 
 It will be noticed, in the above formulae, that M in- 
 creases directly as Q and as n, but Q decreases as n 
 increases, supposing the electric force to remain con- 
 stant. Hence it is evident that a certain proportion 
 between the resistance of the wire and that of the 
 remaining portions of the circuit must be preserved to 
 obtain the maximum magnetic force. This relation is 
 found to be the following: 
 
 When the resistance of the coils of the electro-magnet 
 is equal to the resistance of the rest of the circuit, i. e., the 
 conducting wire and battery, the magnetic force is a maxi- 
 mum* 
 
 The application of this law to a telegraphic circuit 
 would be to make the sum of the resistances of all 
 the magnet coils in circuit equal to the resistance of 
 the line and batteries, but as in practice the resistance 
 of a telegraphic circuit varies, being considerably re- 
 duced by defective insulation, the total resistance of 
 the instruments should be less than that of the line 
 when in good condition, to attain the best results dur- 
 ing unfavorable weather. 
 
 ELECTRICAL FORMULAE. 
 
 184. OHM'S LAW. Let C = the quantity, or strength, 
 or force, or intensity of the current, as it is variously 
 called. 
 
 Let n = the number of cells. 
 " E - the electro-motive force in each cell. 
 " R = the internal resistance of each cell. 
 " r = the resistaucea exterior to tho battery. 
 Then c = n E 
 
 tt + r. 
 
 * Noad'a Students' Text-book of Electricity, p. 277.
 
 MODERN PRACTICE OF THE ELECTRIC TELEGRAPH. 153 
 
 185. PARALLEL OR DERIVED CIRCUITS. 1. The joint 
 resistance of any two parallel or derived circuits, whose 
 resistances = a and b, is equal to their product divided 
 by their sum, or 
 
 + 6 
 
 2. The joint resistance of any three circuits, a, b 
 and c, is 
 
 a 5 c 
 
 R = 
 
 3. The joint resistance of any number of circuits is 
 obtained by adding their reciprocals together, thus : 
 
 "=--;-- 
 
 b 
 
 186. GALVANOMETERS AND SHUNTS. 1. The joint 
 resistance of a galvanometer and shunt is as follows: 
 
 Let g = resistance of galvanometer. 
 s = resistance of shunt. 
 
 ThenR= JLL. 
 
 g + s 
 
 2. The multiplying power of any shunt is equal to 
 
 a s 
 
 3. To prepare a shunt having some definite multiply- 
 ing power, for example 10 100 or 1,000, 
 
 Let n = the multiplying power required, 
 Then s = - 
 
 187. FORMULA FOR THE LOOP TEST (127 . Let x = 
 resistance of shortest part of the loop. 
 
 y = resistance of longest part 
 
 L = total resistance of both. 
 
 R resistance added to shortest part, to make it equal to the longer. 
 
 Then x + y = L. 
 y =. x + R. 
 
 and X = L ~ R
 
 154 APPENDIX AND NOTES. 
 
 188. BLAVIER'S FORMULA FOR LOCATING A FAULT 
 (128). Let R = resistance of line when in good 
 order, S = resistance of defective line when distant 
 end is to ground, and T the resistance when it is dis- 
 connected or open at distant end. 
 
 The distance (x) of the fault from the testing station 
 will be 
 
 x =. S ^ -4- T li T 8 It S~ 
 or x =. S ^(tt .S) x (I 1 S)i 
 
 and the resistance of the fault (z) will be 
 
 z =_ T S + ^&~+ T It ~"T~S~ 
 or z = T S + "'(IT S) * (T b) 
 
 189. MEASURES OF RESISTANCE. 1.0456 Siemen's 
 units = 1 ohm. To convert Siemen's units into ohms. 
 multiply by .9564. 
 
 1 Varley'a unit = 25 ohms. 
 1 Megohm = 1,000,0,0 ohms. 
 -1 Microhm = 1<inr j iinnr ohms. 
 
 STRAIN OF SUSPENDED WIRES.* The ordinary dip 
 of line wires, for a span of 80 yards, is about 18 inches 
 in mild weather ; this gives with No. 8 wire a strain 
 of 420 Ibs., its breaking weight being about 1,300 Ibs. 
 (Culley.) 
 
 .- The strain varies directly as the weight of the wire, 
 arid inversely as the dip or versine ; it increases as 
 the square of the span if the dip be constant ; but to 
 preserve a given strain the dip or versine must in- 
 crease as the square of the span, or, 
 
 ^ \ . - . L ! : P : : V j v. f 
 
 The strain is greater at the point of suspension than-' 
 at the lowest point of the span, by a quantity (equal 
 to the weight of a length of wire of the same height as 
 the versine) which maybe neglected in practice. Call-' 
 ing / the length of the span in feet, w the weight in 
 
 * Clark. Heaiatance Measurement, p. 154.
 
 MODERH PRACTICE OF THE ELECTRIC TELEGRAPH. 155 
 
 cwts. of one statute mile, v the versine in inches, and 
 s the strain in Ibs., 
 
 P X w 
 
 Strain = 31 43 x y Ibs. approximately. 
 
 P X w 
 and dip ^- inches. 
 
 When both supports are of the same height the 
 lowest point in the curve will be in the centre of 
 the span ; but if one support be higher than the 
 other the lowest point will be near the lower support, 
 so that the greater portion of the weight is borne by 
 the higher pole. In calculating the strain the wire 
 should be considered as if prolonged beyond the lower 
 end to a point equal in height to the upper one, and 
 the strain will be proportional to the length thus in- 
 creased, or to twice the distance from the top to the 
 bottom of the dip. 
 
 The weight of a wire increases with its strength, the 
 quality being the same. The advantage of using thin 
 wire for long spans is only in diminishing the weight 
 upon the supports. 
 
 Iron expands TTTTIT of its length, or about 4 T 'o- inches 
 per mile for every ten degrees of heat. (Culley.) 
 
 THE KNO.
 
 I N D E X 
 
 ALPHABET Morse, 101 ; Formation of the, 96 ; Exercises for practising, 97; 
 
 Spaced letters in, 101. 
 
 AMERICAN COMPOUND WIKE, the, 89-104. 
 
 APPARATUS, adjustment of the, 36. 
 
 APPENDIX AND NOTES, 116. 
 
 ARMATURE, 22. 
 
 ATLANTIC CABLES, method of working, 141. 
 
 BATTERIES -Insulation of, 20 ; P.irafflned jars for, 20; Arrangement of, 26; 
 Reversed, 57 ; Table of Resistances of, 117 ; Table of electro-motive 
 forces of, 117; Measurement of electro-motive forces of, 151; Working 
 several lines from, 71; Electrical tension of, 124. 
 
 BATTERY, CARBON, OR ELECTROPOION, 17; Setting up the, 18; Solution, recipe' 
 for making, 19 ; Renewal of the, 19 ; Resistance of, 117, 151 ; Electro- 
 motive force of, 117, 151. 
 
 BATTEISY, DANIELL -12; Effect of continued action on the, 13; Deposit of cop- 
 per upon porous cup of the, 14 ; Renewal of the, 14 ; Application to 
 main circuit of the, 15. 
 
 BATTERY, GROVE 15; Setting up a, 16 ; Renewal of the, 17; Resistance of, 
 117, 150; Electro-motive force of, 117, 151. 
 
 BATTERY, GRAVITY 106; Callaud, 106; Hill, 106; Manner of setting up, 107; 
 Maintenance of, 107 ; Internal resistance of, 117, 149 ; Eloctro-motiva 
 force of, 117. 
 
 BATTERY POWER Distribution of, 70. 
 
 BINDING SCREWS, 57. 
 
 BRIDGE, Wheatstoue's, 109, 110. 
 
 BUTTON REPEATER Wood's, 46, Edison's, 134. 
 
 CABLES, 93; Making joints in, 94. 
 
 CABLES, Atlantic Mo 3e of working the, 141. 
 
 CIRCUIT, 57; Simple galvanic, 9; Earth, 26; Metallic, 57; Local, 30, 57. 
 
 CIRCUITS, Telegraphic, 24, 25. 
 
 CIRCUIT CHANGER, for locals, 56. 
 
 COMPOUND WIRE, the American, 89, 104. 
 
 COMBINATION PRINTING INSTRUMENT, the, 27. 
 
 COMBINATION, locals, 55. 
 
 CONDENSER, used in working Atlantic Cable, 141. 
 
 CONDUCTIVITY RESISTANCE, testing for, 87. 
 
 CONDUCTORS AND NON-CONDUCTOBS, 5 ; Table of, 5.
 
 158 INDEX. 
 
 CONDUCTING POWEB OF MATERIALS, Table of, 147. 
 
 CONSTRUCTION, telegraphic, notes on, 89. 
 
 CBOSS, 57, 73 ; Weather do., 57, 73 ; Testing for, 76 ; To find the distance of, 
 
 85. 
 
 CBOSS CONVICTING WIBES, 57, 75. 
 CUKEENT, Eflfective force of, 24; Laws of, 64. 
 CURRENTS, Earth, 88, 141. 
 
 DEBITED Ciscurrs, formula for, 153. 
 
 DISCONNECTION, 73; Testing for, 75; Partial do., 73; Testing for 75. 
 
 DIAMETERS OF WIBES, table of, 146. 
 
 DOUBLE TRANSMISSION, 131. 
 
 EARTH CIRCUIT, the, 26 ; Resistance of, 26. 
 
 EARTH CURRENTS, 88, 141. 
 
 ELECTRIC CURRENTS, laws of the, 64. 
 
 ELECTRIC SIGNALS, velocity of, 144. 
 
 ELECTRO-MAGNETS, forces of, 151. 
 
 ELECTRO-MAGNET, 21, 22; Cores of, 21; Construction of, 22. 
 
 ELECTRO-MAGNETISM. 21. 
 
 ELECTRO-MOTIVE FORCES, measurement of, 151; Table of, 117, 151. 
 
 ESCAPE, 57, 63, 73 ; Testing for, 75 ; Blavier's formula for locating, 84, 154; 
 
 Effects of upon the circuit, 63. 
 EQUIPMENT OF TELEGRAPH LINES, the, 117. 
 
 FAULTS, Testing for distance of, 80. 
 
 FORMULA Blavier's, for locating an escape, 84, 154 ; For weight and resist- 
 ance of wires, 147 ; Electrical, 152; Ohm's, 152 ; Parallel or derived cir- 
 cuits, 153; Joint resistance of parallel circuits, 153; Galvanometers and 
 shunts, 153; For the loop test, 153. 
 
 GALVANOMETER, 21 ; Testing with, 78 ; Differential, 78, 109 ; Siemens Univer- 
 sal, 108, 111; Bradley 's tangent, 135; Thompson's reflecting, 137. 
 GALVANOMETERS AND SHUNTS, formula for resistance of, 153. 
 GAUGES, wire, comparison of, 146. 
 GROUNDS, testing for, 76. 
 
 GROUND CONNECTIONS, 93; Defective, testing for, 74. 
 GROUND SWITCH, 36, 38. 
 
 INSULATION, 58 ; English standard of, 86; Mileage, 86. 
 
 INSULATOR Glass, 59 ; Wade, 60 ; Hard rubber, 60 ; Lefferte', 61 ; Brooks'. 
 
 61, 62. 
 
 INSULATOBS, mode of testing, 62; Fixing upon poles, 91. 
 INTEBRUPTIONS UPON LINES, 73. 
 INTERNAL RESISTANCE OF BATTERIES, 149. 
 
 JOINTS OB SPLICES, 90; In Cables, method of making, 94. 
 JOINT RESISTANCE, 67, 121; Formula for, 126.
 
 INDEX. 159 
 
 LIGHTNING ARRESTERS, 42; Chester's plate, 43; Bradley's, 43. 
 
 LOCALS, 57; Combination, 55. 
 
 LOCAL CIRCUIT CHANGEK, 56. 
 
 LINE, 57. 
 
 LOOP, 57. 
 
 LOOP TEST, the, 81; Formula for, ib3. 
 
 LEADING WIRES INTO OFFICES, 92. 
 
 LEARNERS. Hiuts to, 97. 
 
 MAGNETS, Electro, 20; Formula for forces of, 151. 
 
 MEASURES, Electrical, 154. 
 
 MEASUREMENT, Electrical, 25; Standards of, 25, 154; Advantages of testing by, 
 
 .80. 
 MORSE SYSTEM, the, 26, 28; Signal key of the, 28; Register of the, 29; Relay 
 
 magnet ol the, 30; Alphabet of the, 101. 
 NOTES ON TELEGRAPHIC CONSTRUCTION, 89. 
 NOTES, APPENDIX AND, 116. 
 
 OHM, definition of the, 25. 
 
 OHM'S LAW, 04, 152; Practical application of, 64. 
 
 OFFICES, leading wires into, 92; Fitting up, 92; Arrangement of wires in, 34, 
 35. 
 
 POLES, Telegraph, 89. 
 
 PRINTING TELEGRAPH the combination, 27; Pope and Edison's, 112. 
 
 QUANTITY, Electrical, 11. 
 
 RESISTANCE, 10; Of the circuit, 42 ; Units of, 25, 154 ; Conductivity, testing 
 for, 87 ; Of unsoldered joints, 87 ; of relays, 117; Of Batteries, table of 
 117; Of different metals, table of, 148; Of liquids, 148; Of copper, 149; 
 Of batteries, to ascertain the, 149. 
 
 RESISTANCE COILS, 25; Testing with, 78. 
 
 REGISTER, Morse, the, 29; Mainline, the, 34; Proper resistance of, 118. 
 
 RELAY, the Morse, 30; Pocket, the, 32. 
 
 RELAYS Proper resistance for, 117. 
 
 READING BY SOUND, 102. 
 
 REPEATERS, 45 ; Wood's button, 46 ; Hicks' automatic, 47 ; Milliken'g, 50 ; 
 Bnnnell's, 52; Edison's button, 107. 
 
 RECENT IMPROVEMENTS IN TELEGRAPH PRACTICE, 104. 
 
 SERVICE, TELEGRAPHIC Technical terms used in the, 57. 
 
 SIEMENS' UNIT, 154; Universal galvanometer, 108, 111. 
 
 SHUNTS of galvanometer, 80 ; Formula for resistance of, 153 ; Multiplying 
 
 power of, 80, 153. 
 SIGNAL KEY, the Morse, 28. 
 SIGNALS ELECTRIC, velocity of, 144 . 
 SOUNDER, the Morse, 32; Main line, the, 33; Proper resistance of, 118.
 
 16Q INDEX. 
 
 SOUND, reading by, 102. * 
 
 SPLICES OK JOISTS, 90. 
 
 SPEED OF TRANSMISSION, 145. 
 
 STATIONS, intermediate, 26 ; Arrangement of, 35 ; Terminal, arrangement of, 
 
 34. 
 
 STBAIN OF SUSPENDED WIKES, 151. 
 SWITCH Ground, 36, 38 ; Button, 37; Plug, 39 ; Universal, 40 ; Culgan, 40 ; 
 
 Jones' lock, 41. 
 SWITCHES OB COMMCTATOBS, 37. 
 
 TECHNICAL TERMS USED IN THE TELEGRAPH SERVICE, 57. 
 
 TENSION, electrical, 11; Of batteries and lines, 124; Diagram of, 128. 
 
 TELEGRAPH LINES Equipment of, 116 ; Electrical tension of, 124 ; Working 
 capacity of, 121. 
 
 TELEGRAPHIC CONSTRUCTION, notes on, 89. 
 
 TEST, the loop, 81 . 
 
 TESTING Insulators, 62; Telegraph lines, 73 ; For disconnection, 74; Partiaf 
 disconnection, 75 ; Escape, 75 ; Cross, 76 ; Ground, 76 ; By galvano- 
 meter and resistance coils, 78 ; For distance of faults, 80 ; By measure- 
 ment, advantages of, 86; For conductivity resistance, 87. 
 
 TRANSMISSION Double, 131 ; Speed of, 145. 
 
 UNITS OF ELECTRICAL MEASUREMENT British Association or Ohm, 25, 154 ; 
 Siemens', 154; Varley's, 154. 
 
 VELOCITY OF ELECTRIC SIGNALS, 144. 
 VARLEY'S UNIT OF MEASUREMENT, 154. 
 
 WEATHER CROSS, 57. 
 
 WIRES To cross connect, 57, 75 ; To put straight, 57 ; To ground, 57 ; To 
 
 open, 57 ; Arrangement of, upon the poles, 90 ; Method of splicing, 90 ; 
 
 Strain of, when suspended, 154. 
 WIRE For telegraph lines, 89 ; American compound, 89, 104 ; Galvanized, 
 
 90 ; Table of diameters of, 119; Iron, formula for ascertaining weight 
 
 of, 147 ; Kesistance of, 147 ; Copper, weight of, 147 ; Resistance of, 
 
 147. 
 
 WIRE GAUGES, comparison of, 146. 
 WHEATSTONE'S BRIDGE, 109, 110. 
 WORKING CAPACITY OF TELEGRAPH LINES, 121 ; How to increase, 121.
 
 SCIENTIFIC BOOKS. 
 
 ' (J. B.) Hydraulic Experiments. Lowell Hydraulic Ex- 
 -- periments being a Selection from Experiments on Hydraulic 
 Motors, on the Flow of Water over Weirs, and in Open Canals of 
 Uniform Rectangular Section, made at Lowell, Mass. By J. B. 
 .FRANCIS, Civil Engineer. Second edition, revised and enlarged, in- 
 cluding many New Experiments on Gauging Water in Open^Canals, 
 and on the Flow through Submerged Orifices and Diverging Tubes. 
 With 23 copperplates, beautifully engraved, and about 100 new 
 pages of text, i vol., 4to. Cloth. $15. 
 
 Most of the practical rules given in the books on hydraulics have been determined from ex- 
 periments made in other countries, with insufficient apparatus, and on such a minute scale, that 
 In applying them to the large operations arising in practice in this country, the engineer cannot 
 but doubt their reliable applicability. The parties controlling the great water-power furnished 
 by the Merrimack River at Lowell, Massachusetts, felt this so keenly, that, they have deemed it 
 necessary, at great expense, to determine anew some of the most important rules for gauging 
 the flow of large streams of water, and for this purpose have caused to be made, with great care, 
 several series of experiments on a large scale, a selection from which are minutely detailed in 
 this volume. 
 
 The work is divided into two parts PART I., on hydraulic motors, includes ninety-two experi- 
 ments on an improved Fourneyron Turbine Water- Wheel, of about two hundred horse-power, 
 with rules and tables for the construction of similar motor? : Thirteen experiments on a model 
 of a centre- vent water-wheel of the most simple design, and thirty-nine experiments on a centre 
 vent water-wheel of about two hundred and thirty horse-power. 
 
 PART II. includes seventy-four experiments made for the purpose of determining the form of 
 the formula for computing the flow of water over weirs ; nine experiments on the effect of back- 
 water on the flow over weirs ; eighty-eight experiments made for the purpose of determining 
 the formula for computing the flow over weirs of regular or standard forms, with several tables 
 of comparisons of the new formula with the results obtained by former experimenters ; five ex- 
 periments on the flow over a dam in which the crest was of the same form as that built by the 
 Essex Company across the Merrimack River at Lawrence, Massachusetts ; twenty-one experi- 
 ments on the effect of observing the depths of water on a weir at different distances from the 
 weir ; an extensive series of experiments made for the purpose of determining rules for gang- 
 ing streams of water in open canals, with tables for facilitating the same; and one hundred and 
 one experiments on the discharge of water through submerged orifices and diverging tubes, the 
 whole being fully illustrated by twenty-three double plates engraved on copper. 
 
 In 1855 the proprietors of the Locks and Canals on Merrimack River, at whose expense mot 
 of the experiments were made, being willing that the public should share the benefits of the 
 scientific operations promoted by them, consented to the publication of the first edition of this 
 work, which contained a selection of the most important hydraulic experiments made at Lowell 
 up to that time. In this second edition the principal hydraulic experiments made there, subse- 
 quent to 1855, have been added, including the important series above mentioned, for determin- 
 ing rules for the ganging the flow of water in open canals, and the interesting series on the flow 
 through a submerged Venturi's tube, in which a larger flow was obtained than any we find re- 
 corded. 
 
 FRANCIS (J. B.) On the Strength of Cast-iron Pillars, with Tables 
 for the use of Engineers, Architects, and Builders. By JAMES B, 
 FRANCIS, Civil Engineer, i vol., 8vo. Cloth. $2.
 
 Scientific Books. 25 
 
 WILLIAMSON (R. S.) On the Use of the Barometer on Surveys 
 and Reconnaissances. Part I. Meteorology in its Connection 
 with Hypsometry. Part II. Barometric Hypsometry. By R. S. 
 WILLIAMSON, Bvt. Lieut. -Col. U. S. A., Major Corps of Engineers. 
 With Illustrative Tables and Engravings. Paper No. 15, Professional 
 Papers, Corps of Engineers. I vol., 4to. Cloth. $15. 
 
 " SAN FRANCISCO, CAL., Feb. 27, 1867. 
 " Gen. A. A. HUMPHREYS, Chief of Engineers, U. S. Army: 
 
 " GENERAL I have the honor to submit to you, in the following pages, the results of my in- 
 vestigations in meteorology and hypsometry, made with the view of ascertaining how far the 
 barometer can be used as a reliable instrument for determining altitudes on extended lines of 
 survey and reconnaissances. These investigations have occupied the leisure permitted me from 
 my professional duties during the last ten years, and I hope the results will be deemed of suffi- 
 cient value to have a place assigned them among the printed profession al papers of the United 
 States Corps of Engineers. Very respectfully, your obedient servant, 
 
 "R. S. WILLIAMSON, 
 " Bvt. Lt.-Col. U. S. A., Major Corps of U. S. Engineers." 
 
 TUNNER (P.) A Treatise on Roll-Turning for the Manufacture of 
 Iron. By PETER TUNNER. Translated and adapted. By JOHN B. 
 PEARSE, of the Pennsylvania Steel Works. With numerous engrav- 
 ings and wood-cuts, i vol., 8vo., with i vol. folio of plates. Cloth. $10. 
 
 SHAFFNER (T. P.) Telegraph Manual. A Complete History and 
 Description of the Semaphoric, Electric, and Magnetic Telegraphs 
 of Europe, Asia, and Africa, with 625 illustrations. By TAL. P. 
 SHAFFNER, of Kentucky. New edition, i vol., Svo. Cloth. 850 pp. 
 $6.50. 
 
 IN^FIE (WM.) Mechanical Drawing. A Text-Book of Geomet- 
 rical Drawing for the use of Mechanics and Schools, in which 
 the Definitions and Rules of Geometry are familiarly explained ; the 
 Practical Problems are arranged, from the most simple to the more 
 complex, and in their description technicalities are avoided as much 
 as possible. With illustrations for Drawing Plans, Sections, and 
 Elevations of Buildings and Machinery ; an Introduction to Isomet- 
 rical Drawing, and an Essay on Linear Perspective and Shadows. 
 Illustrated with over 200 diagrams engraved on steel. By WM 
 MINIFIE, Architect. Seventh edition. With an Appendix on the 
 Theory and Application of Colors. I vol., Svo. Cloth. $4. 
 
 It is the best work on Drawing that we have ever seen, and is especially a text-book of Geo 
 metrical Drawing for the use of Mechanics and Schools. No young Mechanic, such as a Ma- 
 chinist. Engineer, Cabinct-Makcr, Millwright, or Carpeater should be without it." Scientific 
 Aiiiei-ica.'i. 
 
 ' Ono of the most comprehensive works of the kind ever published, and cannot but possess 
 great value to builders. The style is at once elegant and substantial." PeniuujlKania Inr/um-r 
 
 " Whatever is said is rendered perfectly intelligible by remarkably well-executed diagram* on 
 steel, leaving nothing for mere vague supposition ; and the addition of an introduction to i.-*o- 
 metrical drawing, linear perspective, and the projection of shadows, winding up with a useful 
 index to technical terms." Glaxyow Mechanics'' Journal. 
 
 fW The British ^ jvermueut has authorized the use of this book in their schools of art at 
 Sumerset House, London, and throughout the kingdom. 
 
 MINIFIE (WM.) Geometrical Drawing. Abridged from the octavo 
 edition, for the use of Schools. Illustrated with 48 steel plates. 
 Fifth edition, i vol., I2mo. Half roan. $1.50. 
 
 "It is ivell adapted as a text-book of drawing to be used in our High Schools and Academiei 
 where Ji ., useful branch of the fine arts has been hitherto too much neglected." Rpston Journi. 
 
 M
 
 26 D. Van Nostrand's Publications. 
 
 PEIRCE'S SYSTEM OF ANALYTIC MECHANICS. Physical 
 and Celestial Mechanics, by BENJAMIN PEIRCE, Perkins Professor 
 of Astronomy and Mathematics in Harvard University, and Con- 
 sulting Astronomer of the American Ephemeris and Nautical Al- 
 manac. Developed in four sysiems of Analytic Mechanics, Celestial 
 Mechanics, Potential Physics, and Analytic Morphology, i vol., 
 4to. Cloth. $10. 
 
 /""* ILLMORE. Practical Treatise on Limes, Hydraulic Cements, and 
 V-J Mortars. Papers on Practical Engineering, U. S. Engineer De- 
 
 partment, No. 9, containing Reports of numerous experiments con- 
 
 ducted in New York City, during the years 1858 to 1861, inclusive. 
 
 By Q. A. GILLMORE, Brig. -General U. S. Volunteers, and Major U. 
 
 S. Corps of Engineers. With numerous illustrations. One volume, 
 
 octavo. Cloth. $4. 
 
 ROGERS (H. D.) Geology of Pennsylvania. A complete Scien- 
 tific Treatise on the Coal Formations. By HENRY D. ROGERS, 
 Geologist. 3 vols., 4to., plates and maps. Boards. $30.00. 
 
 BURGH (N. P.) Modern Marine Engineering, applied to Paddle 
 and Screw Propulsion. Consisting of 36 colored plates, 259 
 Practical Woodcut Illustrations, and 403 pages of Descriptive Matter, 
 the whole being an exposition of the present practice of the follow- 
 ing firms :' Messrs. J. Penn & Sons; Messrs. Maudslay, Sons, & 
 Field ; Messrs. James Watt & Co. ; Messrs. J. & G. Rennie ; Messrs. 
 R. Napier & Sons ; Messrs. J. & W. Dudgeon ; Messrs. Ravenhill 
 & Hodgson ; Messrs. Humphreys & Tenant ; Mr. J. T. Spencer, 
 and Messrs, Forrester & Co. By N. P. BURGH, Engineer. In one 
 thick vol., 4to. Cloth. $30.00. Half morocco. $35.00. 
 
 ING. Lessons and Practical Notes on Steam, the Steam-Engine, 
 Propellers, &c. , &c., for Young Marine Engineers, Students, 
 and others. By the late W. R. KING, U. S. N. Revised by Chief- 
 Engineer J. W. KING, U. S. Navy. Ninth edition, enlarged. 8vo. 
 Cloth. $2. 
 
 ARD. Steam for the Million. A Popular Treatise on Steam and 
 its Application to the Useful Arts, especially to Navigation. By 
 J. H. WARD, Commander U. S. Navy. New and revised edition. 
 i vol., 8vo. Cloth. $i. 
 
 ALKER. Screw Propulsion. Notes on Screw Propulsion, its 
 Rise and History. By Capt. W. H. WALKER, U. S. Navy, i 
 vol., 8vo. Cloth. 75 cents. 
 
 THE STEAM-ENGINE INDICATOR, and the Improved Mano- 
 meter Steam and Vacuum Gauges : Their Utility and Application. 
 By PAUL STILLMAN. New edition, i vol., I2mo. Flexible cloth. 
 $i. 
 
 T SHERWOOD. Engineering Precedents for Steam Machinery. Ar- 
 1- ranged in the most practical and useful manner for Engineers. By 
 B. F. ISHERWOOD, Civil Engineer U. S. Navy. With illustration* 
 Two volumes in one. 8vo. Cloth. $2.50. 
 
 K 
 
 W 
 
 W
 
 Scientific Books. 27 
 
 POOR'S METHOD OF COMPARING THE LINES AND 
 DRAUGHTING VESSELS PROPELLED BY SAIL OR 
 STEAM, including a Chapter on Laying off on the Mould-Loft 
 Floor. By SAMUEL M. POOK, Naval Constructor. i vol., 8vo. 
 With illustrations. Cloth. $5. 
 
 SWEET (S. H. ) Special Report on Coal ; showing its Distribution, 
 Classification and Cost delivered over different routes to various 
 points in the State of New York, and the principal cities on the 
 Atlantic Coast. By S. H. SWEET. With maps, i vol., 8vo. Cloth. 
 $3- 
 
 A LEXANDER (J. H.) Universal Dictionary of Weights and Meas- 
 t*- ures, Ancient and Modern, reduced to the standards of the United 
 States of America. By J. H. ALEXANDER. New edition, i vol., 
 8vo. Cloth. $3.50. 
 
 " As a standard work of reference this book should be in every library ; it is ote which wo 
 have long wanted, and it will save us much trouble and research." Scientific American. 
 
 CRAIG (B. F. ) Weights and Measures. An Account of the Deci- 
 mal System, with Tables of Conversion for Commercial and Scien- 
 tific Uses. By B. F. CRAIG, M. D. i vol., square '321110. Limp 
 cloth. 50 cents. 
 
 " The most lucid, accurate, and useful of all the hand-books on this subject that we have yet 
 Been. It gives forty-seven tables of comparison between the English and French denominations 
 of length, area, capacity, weight, and the centigrade and Fahrenheit thermometers, with clear 
 instructions how to use them : and to this practical portion, which helps to make the transition 
 as easy as possible, is prefixed a scientific explanation of the errors in the metric system, and 
 how they may be corrected in the laboratory." Nation. 
 
 BAUERMAN. Treatise on the Metallurgy of Iron, containing 
 outlines of the History of Iron manufacture, methods of Assay, 
 and analysis of Iron Ores, processes of manufacture of Iron and 
 Steel, etc., etc. By H. BAUERMAN. First American edition. Re- 
 vised and enlarged, with an appendix on the Martin Process for 
 making Steel, from the report of Abram S. Hewitt. Illustrated 
 with numerous wood engravings. I2mo. Cloth. $2.50. 
 
 " This is an important addition to the stock of technical works published in this country. It 
 embodies the latest facts, discoveries, and processes connected with the manufacture of iron 
 and steel, and should be in the hands of every person interested in the subject, as well as in all 
 technical and scientific libraries." Scientific American. 
 
 HARRISON. Mechanic's Tool Book, with practical -rules and sug- 
 gestions, for- the use of Machinists, Iron Workers, and others. 
 By W. B. HARRISON, associate editor of the "American Artisan." 
 Illustrated with 44 engravings. I2mo. Cloth. $2.50. 
 
 " This work is specially adapted to meet the wants of Machinists and workers in iron gener- 
 ally. It is made up of the work-day experience of an intellrgent and ingenious mechanic, who 
 had the faculty of adapting tools to various purposes. The practicability of his pUns 8t>4 sug- 
 gestions ire made apparent even to the unpractised eye by a series of well-executed v,'on& ro 
 p*;-\ns." Philadelphia Inquirer.
 
 N 
 
 28 D. Van Nostrands Publications. 
 
 "DLYMPTON. The Blow-Pipe : A System of Instruction in its prao 
 -L tical use, being a graduated course of Analysis for the use of 
 students, and all those engaged in the Examination of Metallic 
 Combinations. Second edition, with an appendix and a copious 
 index. By GEORGE W. PLYMPTON, of the Polytechnic Institute, 
 Brooklyn. I2mo. Cloth. $2. 
 
 " This manual probably has no superior in the English language as a text-book for beginners, 
 or as a guide to the student working without a teacher. To the latter many illustrations of the 
 utensils and apparatus required in using the blow-pipe, as well as the fully illustrated descrip- 
 tion of the blow-pipe flame, will be especially serviceable." New York Teacher. 
 
 UGENT. Treatise on Optics : or, Light and Sight, theoretically 
 and practically treated ; with the application to Fine Art and In- 
 dustrial Pursuits. By E. NUGENT. With one hundred and three 
 illustrations. I2mo. Cloth. $2. 
 
 " This book is of a practical rather than a theoretical kind, and is designed to afford accurate 
 and complete information to all interested in applications of the science." Bound Table. 
 
 O ILVERSMITH (Julius). A Practical Hand-Book for Miners, Met- 
 ^-? allurgists, and Assayers, comprising the most recent improvements 
 
 in the disintegration, amalgamation, smelting, and parting of the 
 
 Precious Ores, with a Comprehensive Digest of the Mining Laws. 
 
 Greatly augmented, revised, and corrected. By JULIUS SILVERSMITH. 
 
 Fourth edition. Profusely illustrated, i vol., i2mo. Cloth. $3. 
 
 C LOUGH. The Contractors' Manual and Builders' Price-Book. By 
 A. B. CLOUGH, Architect, i vol., i8mo. Cloth. 75 cents. 
 
 BRUNNOW. Spherical Astronomy. By F. BRTTNNOW, Ph. Dr. 
 Translated by the Author from the Second German edition, i 
 vol., 8vo. Cloth. $6.50. 
 
 C~"HAUVENET (Prof. Wm.) New method of Correcting Lunar Dis- 
 tances, and Improved Method of Finding the Error and Rate of a 
 Chronometer, by equal altitudes. By WM. CHAUVENET, LL.D. i 
 vol., 8vo. Cloth. $2. 
 
 A SYNOPSIS OF BRITISH GAS LIGHTING, comprising the 
 essence of the " London Journal of Gas Lighting" from 1849 to 
 1868. Arranged and executed by JAMES R. SMEDBERG, C. E. of the 
 San Francisco Gas Works. Issued only to subscribers. 4to. Cloth. 
 $15.00 In press. 
 
 AS WORKS OF LONDON. By ZERAH COLBURN. i2mo. Boards. 
 60 cents. 
 
 HEWSON. Principles and Practice of Embanking Lands from 
 River Floods, as applied to the Levees of the Mississippi. By 
 WILLIAM HEWSON, Civil Engineer, i vol., 8vo. Cloth. $2. 
 
 " This is a valuable treatise on the principles and practice of embanking lands from river 
 Jloods, as applied to Levees of the Mississippi, by a highly intelligent and experienced engineer. 
 The author says it is a first attempt to reduce to order and to rule the design, execution, and 
 measurement of the Levees of the Mississippi. It is a most use.lu! and needv. contribution ta 
 ientific literature." Philadelphia Evening Journal. 
 
 G
 
 Scientific Books. 29 
 
 WEISBACH (Julius). Principles of the Mechanics of Machinery 
 and Engineering. By DR. JULIUS WEISBACH, of Freiburg. 
 Translated from the last German edition. Vol. i. Svo, cloth. $10. 
 
 HUNT (R. M.) Designs for the Gateways of the Southern Entrances 
 to the Central Park. By RICHARD M. HUNT. With a descrip- 
 tion of the designs, i vol., 4to. Illustrated. Cloth. $5. 
 
 TDEET. Manual of Inorganic Chemistry for Students. By the late 
 -L DUDLEY PEET, M. D. Revised and enlarged by ISAAC LEWIS PEET, 
 A. M. i8mo. Cloth. 75 cents. 
 
 WHITNEY (J. P.) Colorado, in the United States of America. 
 Schedule of Ores contributed by sundry persons to the Paris 
 Universal Exposition of 1867, with some Information about the 
 Region and its Resources. By J. P. WHITNEY, of Boston, Com- 
 missioner from the Territory. Pamphlet. 8vo., with maps. Lon- 
 don, 1867. 25 cents. 
 
 WHITNEY (J. P.) Silver Mining Regions of Colorado, with some 
 account of the different processes now being introduced for 
 working the Gold Ores of that Territory. By J. P. WHITNEY. 
 I2mo. Paper. 25 cents. 
 
 " This is a most valuable little book, containing a vast amount of practical information about 
 that region. It will be found useful to men of a scientific turn of mind, should they never COH- 
 template a journey to the region of silver and gold/' fall E'w&r News. 
 
 CILVER DISTRICTS OF NEVADA. 8vo., with map. Paper. 
 ^ 35 cents. 
 
 McCORMICK (R. C.) Arizona : Its Resources and Prospects. 
 By Hon. R. C. McCoRMiCK. With map. Svo. Paper. 25 cents. 
 
 PETERS. Notes on the Origin, Nature, Prevention, and Treatment 
 of Asiatic Cholera. By JOHN C. PETERS, M. D. Second edition. 
 With an appendix and map. iamo. Cloth. $1.50. 
 
 SEYMOUR. Western Incidents connected with the Union Pacific 
 Railroad. By SILAS SEYMOUR. I2mo. Cloth. $i. 
 
 EULOGIES IN MEMORY OF MAJ.-GEN. JAMES S. WADS- 
 WORTH AND COL. PETER A. PORTER, before the " Cen- 
 tury Association." Tinted paper. Svo. Paper. $i. 
 
 PALMER. Antarctic Mariners' Song. By JAMES CROXALL PALMER, 
 U. S. N. Illustrated. Cloth, gilt, bevelled boards. $3. 
 
 " The poem is founded upon and narrates the episodes of the exploring expedition of a small 
 jailing vessel, the ' Flying Fish,' in company with the ' Peacock,' in the South Seas, in 1S3&- 
 42. The 'Flying Fish' was too small to be safe or comfortable in that Antarctic region, al- 
 though wo find in the poem bnt little of complaint or murmuring at the hardships the sailors 
 were compelled to endure." Athenaeum. 
 
 FRENCH'S ETHICS. Practical Ethics. By Rev. J. W. FREXCH. 
 D. D., Professor of Ethics, U. S. Military Academy. Prepared foi 
 the Uf.e of Students in the Military Academy, i vol. Svo. Cloth, 
 
 $4.53,
 
 Scientific Books. 31 
 
 THE MECHANIC'S AND STUDENT'S GUIDE in the Designing 
 and Construction of General Machine Gearing, as Eccentrics, 
 Screws, Toothed Wheels, etc., and the Drawing of Rectilineal and 
 Curved Surfaces ; with Practical Rules and Details. Edited by 
 FRANCIS HERBERT JOYNSON. Illustrated with 18 folded plates. 8vo. 
 Cloth. $2.00. 
 
 "The aim of this work is to be a guide to mechanics in the designing and construction 
 of general machine-gearing. This design it well fulfils, being plainly and sensibly written, and 
 profusely illustrated." Sunday Times. 
 
 FREE-HAND DRAWING - a Guide to Ornamental, Figure, and 
 Landscape Drawing. By an Art Student. i8mo. Cloth. 
 75 cents. 
 
 THE EARTH'S CRUST : a Handy Outline of Geology. By DAVID 
 PAGE. Fourth edition. iSmo. Cloth. 75 cents. 
 
 " Such a work as this was much wanted a work giving in clear and intelligible outline the 
 leading facts of the science, without amplification or irksome details. It i? admirable in 
 arrangement, and clear and easy, and, at the same time, forcible in style. It will lead, we hope, 
 to the introduction of Geology into many schools that have neither time nor room for the study 
 of large treatises." The Aluseum. 
 
 HISTORY AND PROGRESS OF THE ELECTRIC TELE- 
 GRAPH, with Descriptions of some of the Apparatus. By 
 ROBERT SABINE, C. E. Second edition, with additions. i2mo. 
 Cloth. $1.75. 
 
 TRON TRUSS BRIDGES FOR RAILROADS. The Method of 
 
 J- Calculating Strains in Trusses, with a careful comparison of the 
 
 most prominent Trusses, in reference to economy in combination, etc., 
 
 etc. By Brevet Colonel WILLIAM E. MERRILL, U. S. A., Major 
 
 Corps of Engineers. With illustrations. 4to. Cloth. $5.00. 
 
 USEFUL INFORMATION FOR RAILWAY MEN. Compiled 
 by W. G. HAMILTON, Engineer. Second edition, revised and 
 enlarged. 570 pages. Pocket form. Morocco, gilt. $2.00. 
 
 REPORT ON MACHINERY AND PROCESSES OF THE IN- 
 DUSTRIAL ARTS AND APPARATUS, OF THE EXACT 
 SCIENCES. By F. A. P. BARNARD, LL. D. Paris Universal Ex- 
 position, 1867. i vol., 8vo. Cloth. $5.00. 
 
 THE METALS USED IN CONSTRUCTION : Iron, Steel, Bessemei 
 Metal, etc., etc. By FRANCIS HERBERT JOYNSON. Illustrated. 
 i2mo. Cloth. 75 cents. 
 
 " In the interests of practical science, we ere bound to notice this work ; and to those wlw. 
 wish further information, we should say, buy it ; and the outlay, we honestly believe, will b 
 tonsidered well spent." Scientific Review. 
 
 DICTIONARY OF MANUFACTURES, MINING, MACHINERY, 
 AND THE INDUSTRIAL ARTS. By GEORGE DODD. i2mo. 
 Cloth. $2.00.
 
 WORKS ON ELECTRICITY 
 
 AND 
 
 THE ELECTRIC TELEGRAPH. 
 
 A HAND-BOOK OF PRACTICAL TELEGRAPHY. 
 
 By- R. S. CULLEY, 
 
 Engineer to the Electric and Intel-national Telegraph Company. 
 
 Published with the sanction cf the Chairman and Directors of the Electric 
 and International Telegraph Company, and adopted by the Department of 
 Telegraphs for India. 
 
 FOURTH EDITION, REVISED AND ENLARGED.] 
 1 vol., 8vo, cloth, $5.00. 
 
 HiSTORI AND PROGRESS OF THE ELECTRIC TELEGRAPH, 
 
 WITH DESCRIPTIONS OF SOME OF THE APPARATUS. 
 
 By ROBERT SABINE. 
 Second Edition, with Additions. l'2rno, cloth, 1-.W.* /' 2-J 
 
 Modern Practice of the Electric Telegraph. 
 
 A HAND-BOOK FOR ELECTRICIANS AND OPERATORS. 
 By FRANK L. POPE. 
 
 lition. 8vo, illustrated. Cloth, 
 
 THE TELEGRAPH MANUAL. 
 
 A COMPLETE HISTORY AND DESCRIPTION OF THE 
 
 SEMAPHORIC, ELECTRIC, AND MAGNETIC TELEGRAPHS 
 
 OF 
 EUROPE, ASIA, AFRICA, AlfD AMERICA, 
 
 ANCIENT AND MODERN. 
 
 WITH SIX HUNDRED AND TWENTY-FIVE ILLUSTRATIONS. 
 By TAL. P. SHAFFNEK. 
 
 8vo, cloth, $6.50. 
 
 D. VAST ^OSTEA]\ T D, 
 
 Publisher, Bookseller, and Importer of Scientific Books, 
 
 2% Murray and 27 Warren Street, New Yo k. 
 
 *,* Any of the above sent free by mail on receipt of price.
 
 CHARLES T. & J. IV. CHESTER, 
 
 104 Centre St., New York* 
 
 ENGINEERS, 
 
 AND MANUFACTURERS OF 
 
 Instruments, Batteries, 
 
 AND EVERY DESCRIPTION OF 
 
 INSULATED AND OFFICE WIKES. 
 
 We are now prepared to furnish, after an experience of three year?, an Insulated 
 AViiv, which can be buried in the earth or exposed to rain and sun, or to the vapor of 
 acids, without injury. Professor SII.LIMAN, who has exposed it to the most destructive 
 agencies, finds that it remains uninjured in an atmosphere of ozone which would de- 
 stroy gutta-percha in a few hours. It exceeds glass, or any other known substance, 
 as a'non-conductor. We have made special arrangements to furnish this article for 
 office purposes at a reduced rate. Also, Agents for the new insulator, 
 
 KRYOLITE. 
 
 Haider than glass, and possessing the best insulating properties. 'We construct the 
 
 DIFFERENTIAL GALVANOMETERS AND RESISTANCE BOXES 
 
 used bv English electricians, and described in this work, for measuring resistances and 
 ascertaining faults. 
 
 To accommodate these instruments to the wants of our Telegraph patrons we have 
 made them at different prices, as the absolute accuracy required in the philosophical 
 investigation of Electrical phenomena is not necessary for ordinary telegraphic prob- 
 lems. These instruments instantly determine the resistances of magnets and lines, 
 and furnish every required assistance in line tests. 
 
 We have submitted to the test of more than a year's active use our new 
 
 ENDURING BATTERY. 
 
 For thirteen months it has given a constant current, day and night, on a short tele- 
 graph line. So equal is the current derived from it that the adjustments of magnets 
 formerly necessary on that line have been almost entirely dispensed with. The con- 
 sumption of material for currents equal to those from the sulphate of copper battery 
 used on lines from the same office, is only about one-tenth. The reason for this great 
 difference is that the salts decomposed in exciting electrical action are separate from 
 the other elements, and are retained in a reservoir insulated, but allowed to escape and 
 carry on their action entirely under control. Thus, for Electrical Clocks, where the 
 amount of current required is very small, the adjustments can be so made that the 
 battery will last two years. For a local, this battery acts admirably ; though having 
 less quantity force than many now in use, it has quite power enough for a well con- 
 structed Sounder or Eegister. 
 We also construct a 
 
 made with great perfection. It is very compact, works on one wire, does not easily 
 get out of order, works with speed, and will, in many cases, be used for commercial 
 purposes on private lines where our dial instruments have been largely used. 
 We have, after a test of live years, an 
 
 ALPHABETICAL TELEGRAPH 
 
 in extensive use. Over thirty of these are employed in the Police Telegraph System 
 of St. Louis, and have given perfect satisfaction. They are used by the Steamship 
 Companies, by Iron Founders, Lumber Merchants, Coal Dealers, Sugar Kctineries, and 
 wherever the nature of the business requires a separation of office aiid factory. 
 We supply every description of 
 
 ELECTRICAL BE&CHINERV- AND APPLIANCES 
 
 for submarine and subterranean blasting. Also, complete 
 
 PORTABLE APPARATUS 
 
 For the safe manufacture of NITROGLYCERINE at the place where it is to be used. 
 Our Catalogue, embracing a large amount of new matter and description, is now 
 ready for distribution.
 
 CHESTER, PARTRICK & CO, 
 
 CONTRACTORS, etc., 
 37 South Fourth Street, Philadelphia, 
 
 Manufacturers of and Dealers in every variety of 
 
 TELEGRAPHIC, ELECTRIC AND PHILOSOPHICAL APPARATUS, BAT- 
 
 TERIES, WIRE, ACIDS, INSULATORS, MEDICAL INSTRUMENTS 
 
 AND OTHER SUPPLIES. 
 
 Also, Contractors for the construction, re-construction and repair of 
 
 TELEGRAPH LINES, SIMPLE BURGLAR ALARMS FOR PRIVATE 
 
 RESIDENCES, AND BURGLAR ALARMS WITH " TELL-TALE 
 
 CLOCK," AND OTHER APPARATUS FOR BANKS 
 
 AND PUBLIC BUILDINGS. 
 
 Among other Telegraphic Supplies constantly kept on hand, they are prepared 
 to furnish promptly the following novel articles : 
 
 KERITE (OR HORN COVERED) COPPER, OR COMPOUND WIRE OR 
 
 CABLES, 
 
 COVERED COMPOUND AIR LINE WIRE ; 
 
 BLASTING APPARATUS, CARTRIDGES, BATTERIES, &c., &c. 
 CALCIUM LIGHTING APPARATUS, 
 
 MEDICAL BATTERIES, 
 
 INDUCED AND DIRECT CURRENTS ; 
 
 ELECTRO-PLATERS' BATTERIES AND MATERIALS, 
 
 ELECTRO GONGS OF ANY DESIRED SIZE OR WEIGHT ; 
 
 ALARM APPARATUS, 
 
 PATENT APPARATUS for the MANUFACTURE of NITRO-GLYCERINE, 
 
 ELECTRICAL CLOCK-WORK, 
 
 &c., &c., &c. 
 
 They guarantee to give satisfact'.on to all who favor them with orders, in the 
 promptness of execution and in the quality of articles supplied.
 
 L. G. TILLOTSON & CO., 
 
 3STo. :Q T^e-y Street, 3STev^ Y 
 
 MANUFACTURERS OF 
 
 TELEGRAPH INSTRUMENTS, 
 
 BATTERIES AND SUPPLIES, 
 
 OF EVERY DESCRIPTION, 
 
 Glass Insulators, Plain or with Screw; Brackets, &c.; Zincs, Tum- 
 blers, Porous Cups, and all kinds of Battery Material; Hill's 
 Patent Galvanic Battery ; Ogden's Improved Carbons, 
 with the Immersed Platina Connection; Pure 
 Nitric and Sulphuric Acids; Agents 
 for the Best English and American 
 Plain and Galvanized Wire. 
 
 Agents for Gutta-Percha Covered Wire 
 
 and Cables, American Manufacture; 
 
 Agents of American Compound 
 
 Telegraph Wire Company; 
 
 SOLE AGENTS FOR 
 
 Brooks' Patent Paraffine Insulator. 
 
 This Insulator, as now constructed, is, beyond question, the best in use. 
 MANUFACTURERS OF 
 
 JONES' PATENT LOCK SWITCH BOARD. 
 
 e invite attention to our cuts, opposite pages 29 and 35 of this work. 
 
 BLISS, TILLOTSON & CO,, 171 So, Clark St., Chicago,
 
 CHARLES WILLIAMS, JR., 
 
 1O9 COURT STREET, 
 
 BOSTON, MA.SS., 
 
 (ESTABLISHED 1856.) 
 
 MANUFACTURER OF 
 
 TELEGRAPH INSTRUMENTS, 
 BATTERIES AISS MATERIALS, 
 
 'SOLK MANUFACTURE OF 
 
 THE GRIGim CELEBRATED 
 
 EMI- A. 
 
 All Instruments and Materials used in furnishing and working 
 
 TELEGRAPH LINES, 
 
 
 
 including Registers, Belays, Main Sounders, Local Sounders, 
 Keys, Switches, Cut-outs, Galvanometers, Repeaters, Arresters, 
 Rheostats, Resistance Coils, Boll Calls, Dial Telegraphs, Gongs, 
 Batteries, Porous Cups, Zincs, Coppers, Blue Vitriol, Acid, Insu- 
 lators, Line Wire, Insulated Wire, Cables, etc., constantly on 
 hand, and for sale at the lowest prices. Also, Electro-Medical 
 Instruments and Magnetical Apparatus of every description.
 
 IMPROVED PREMIUM TELEGRAPH INSTRUMENTS. 
 DR. L. BRADLEY, 
 
 Ko. 7 EXCHANGE PLACE, JERSEY CITY, N. J. 
 
 KEEPS CONSTANTLY ON HAND AND FOR SALE HIS CELEI RATED 
 
 flnjnmim JmpromI S^Irgraplt 
 
 BRADLEY'S Relays were awarded the 
 
 FIRST 
 
 of the late Great Fair of the American Institute, New York, and their superi- 
 ority is generally acknowledged by operators who use them. 
 
 Aside from the advantages apparent upon inspection of these magnets, 
 their acknowledged merits consist in the construction of the helix, which was 
 patented August 15, 1865 this being of naked copper wire, so wound that the 
 convolutions are separated from each other by a regular and uniform space of 
 the l-800th of an inch, the layers separated by thin paper. In helices of silk 
 insulated wire the space occupied by the silk is the l-150th to the l-300th of 
 an inch ; therefore a spool made of a given length and size of naked wire will 
 be smaller, and will contain many more convolutions around the core than 
 one of silk insulated wire, and will make a proportionably stronger magnet, 
 while the resistance will be the same. 
 
 He is also manufacturing superior Lightning Arresters, with Cut-out 
 Switch and Switches for grounding either wire. 
 
 From hundreds of testimonials there is space only for the following : 
 
 80 BROADWAY, NEW YOEE, March 15, 1870. 
 L. BRADLEY, Esq. 
 
 DEAR SIB, I have used a very large number of the Magnets manufactured 
 by you, with the patent naked wire helices, principally in the manufacture of 
 printing instruments, and they have in all cases given entire satisfaction. 
 With a given battery power and equal resistance, I have found them 20 per 
 cent, stronger than silk covered magnets will average. They are remarkably 
 even in quality and free from permanent magnetism. 
 
 FRANK L. POPF, Electrical Engineer. 
 
 PRICKS 
 
 will be as favorable as goods of equal or approximate excellence can be pur- 
 chased of any other manufacturer. 
 
 The following list comprises the principal articles manufactured and sold 
 at this establishment : 
 
 Button Repeaters, Pony Sounders, Keys. 
 
 Kelays, with Helices in Bone Rubber Cylinders (very fine). 
 
 Box Relays, large and small ; Excellent Registers. 
 
 Large and small Box Main Sounders. 
 
 A new style of both Main and Local Sounders (very loud and fine). 
 
 Pocket Relays, with all the adjustments of the above, and good Lever Keys. 
 
 All other kiuds of Telegraph Apparatus manufactured to order. 
 
 Extra Spools, for replacing such as may be spoiled by lightning, fur- 
 nished at $1.25 each. Old Spools taken at the price of new wire by the pound. 
 Goods sent to all parts of the continent with bill C. 0. D. Or, to save ex- 
 pense of returning funds by express, remittances may be made in advance by 
 certified check, payable in New York, or by Post-office order, in which case 
 he will make no charge for package. 
 
 He has ample facilities for furnishing all other kinds of Telegraph Sup- 
 lisj at the lowest manufacturers' prices.
 
 BROOKS' 
 
 Patent Paiaffine Insulator Works, 
 
 ;...::':,.., 1 1 
 21 Aspen 5>reet, North of 2123 Chestnut Street, Philadelphia, Pa. 
 
 DAVID BROOKS, Proprietor. 
 
 L, G, TILLOTSON & CO,, 8 Dey Street, New York, 
 
 WORKS ON ELECTRICITY 
 
 AND 
 
 THE ELECTEIC TELEGEAPH, 
 
 FOE SALE BY 
 
 ID. "V ^ 1ST 1ST O S T R^ 1ST D, 
 
 PUBLISHER AND BOOKSELLER, 
 
 23 Murray Street and 27 Warren Sreent, New York. 
 
 Prescott's Theory and Practice of the Electric Telegraph. 12mr., 
 
 illustrated. Cloth, $2. 50. 
 
 Blight's Electric Telegraph. 12mo, illustrated. Cloth, $1.75. 
 Ferguson's Electricity. 12mo, illustrated. Cloth, $1.75. 
 Noad's Student's Text-Book of Electricity. Crown 8vo, illust'd. $6.25. 
 Electrical Measurement. By LATIMEK CLABK. 12mo, illustrated. Cloth. $3. 
 The Atlantic Telegraph. Its History. 12mo, illustrated. Cloth, $1.00. 
 Blavier's Traite de Telegraphic Electrique. 2 vols., 8vo. Paper, $10. 
 Du Moncel's Traite Theorique et Pratique de Telegraphic Electrique. 
 
 bvo. Paper, $5. 
 
 Gavarret's Telegraphic Electrique. 12mo. Paper, $2.50. 
 Tennant's Manuel Pratique de Telegraphic Sous-Marine. 12mo. 
 
 Paper, SI. 75. 
 Boussac Precis de Telegraphic Electrique. 8vo. Paper, $3.50.
 
 TZEiZE! 
 
 JOURNAL OF THE TELEGRAPH, 
 
 A SEMI-MONTHLY PAPEK, 
 
 DEVOTED TO THE 
 
 Interests of the Telegraph in the United States, 
 
 And a record of its progress throughout the world. 
 
 Published on the 1st and 15th of each Month, 
 
 AT THE 
 
 EXECUTIVE BOOMS OF THE WESTEBN UNION TELEGRAPH CO., 
 145 BROADWAY. NEW YORK. 
 
 The JOUBNAL OF THE TELEGKAPH is the Official Organ of the Western 
 Union Telegraph Company, through which are promulgated, for the informa- 
 tion of the Stockholders and the public, authentic details relating to tho 
 financial affairs of the Company embracing a monthly statement of earn- 
 ings, expenditures, and net profits and the orders of the Executive Offi- 
 cers to the employes. In its columns will also be found accurate and 
 valuable information in regard to the operation and extension of the lines, 
 and a full discussion of all other matters of a scientific or general character 
 pertaining to the telegraphic art. 
 
 Over five thousand copies of the JOURNAL OF THE TELEGKAPH are now 
 issued, every Telegraph Office in the country receiving one, and many Stock- 
 holders and others being subscribers. 
 
 TEKMS OF SUBSCEIPTION. 
 
 One copy, one year $1 00 
 
 Five copies, " 400 
 
 Single copies, five cents. 
 
 inserted at reasonable rates. All communications and remittances for the 
 JOURNAL OF THE TELEGRAPH should be addressed to 
 
 JAMES D. REID, Editor, 
 
 145 BRO Jilt WAY, XJ2W TO11K.
 
 THE ' TELEGRAPHER: 
 
 A JOURNAL OF 
 
 Electrical I? j? ogress. 
 
 PUBLISHED EVERY SATURDAY, 
 
 AT 
 
 Nos. 78 and 80 Broadway (Room 48), New York. 
 
 (OVER THE GOLD EXCHANGE.) 
 Devoted strictly and exclusively to Telegraphic interests, and the only recognized 
 
 organ of the 
 
 TELEGRAPHIC PROFESSION 
 in this country or the world. 
 
 Experience, energy, industry, and capital will all be combined to make THE TKI.F- 
 GRAPHER what it purports to be A. JOURNAL OF ELECTRICAL, PROGRESS and to rer- 
 der it worthy of the continuance of the liberal support which it has received from the 
 profession and others interested in E'ectrical Science and Telegraphic Art, and to make 
 it a creditable representative of the Practical Telegraphic Talent of the United State?. 
 Correspondence, items of news or personal interest, and newspaper extracts relating 
 to Telegraphic matters, are solicited. The co-operation of every person interested in 
 sustaining a first-class Telegraphic newspaper is cordially invited. 
 
 TERMS OF SUBSCRIPTION" : 
 
 One copy, one year $2 00 
 
 Six copies, one year to one address 10 00 
 
 Twelve" " '' " 1700 
 
 Single copies, five cents. 
 
 ^^ Subscribers in the British Provinces must remit 20 cents, Great Britain, 
 France, Italy, Spain and Portugal, $1.04, Russia, Prussia, and the west coast ot 
 S^uth America, $3.12 per annum, in addition to the subscription price, for prepay- 
 ment of American postage. 
 
 THE PAPER WILL ALWAYS BE DISCONTINUED WHEN THE PAID SUBSCRIPTION EX- 
 PIRES. 
 
 Remittances may be made by Registered Letter or Post-office Order, at our risk. 
 
 will be inserted at reasonable rates, but no Advertisement will be inserted for less than 
 One Dollar for each insertion. 
 
 Any persons who may interest themselves in procuring Subscribers at the adver- 
 tised rates, and remitting us the money, will be entitled to an extra copy for one year, 
 for every club of not less than six Subscribers'. 
 
 All communications, and letters relating to or intended for THE TELEGRAPHER, 
 must be addressed to the 
 
 PUBLISHER AND EDITOR, 
 
 P, O. BOX 6010, 
 
 NEW YORK.
 
 m 
 
 53(03 
 
 n 
 
 THE LIBRARY 
 UNIVERSITY OF CALIFORNIA 
 
 Santa Barbara 
 
 THIS BOOK IS DUE ON THE LAST DATE 
 STAMPED BELOW.
 
 A