  About 1867 William Robinson, then a recent graduate from college, entered actively upon the development of an automatic signal system for preventing accidents of various kinds on railroads. His attention was called to the subject by the consideration of certain railroad accidents which had occurred, and for the prevention of which there were no adequate means known. From this starting point he developed such a system, and in 1869, constructed an elaborate model illustrating the same, which he exhibited at the American Institute Fair in New York City, in 1870. This system was what is now known in the art as a "wire" or "open circuit" system; that is, there were circuit-instruments in proximity to the track which were actuated by the wheels of a car. The action of the wheels on a lever at one point closed the circuit through a relay, whose magnet was so arranged that the instant it was magnetized it attracted its armature and kept its own circuit closed. The circuit of the magnet which directly actuated or controlled the signal was under control of the relay, which operated to open and close the signal circuit directly. When the train or car proceeded to the proper point beyond, it actuated a reversing lever, thus opening the relay circuit and reversing the signal. In the model described the reversing lever operated to open the relay circuit by cutting off the battery therefrom by short circuiting. This model was in continuous and perfect operation throughout the duration of the fair. At the close of the fair Mr. Robinson had some of his descriptive circulars left over. These he immediately sent out to railroad companies at random. One of these circulars, at least, was as seed sown in good ground. It elicited an immediate response from Mr. William A. Baldwin, general superintendent of the Philadelphia and Erie railroad, with the result that Mr. Baldwin, who was an old telegraph operator and a very able and progressive railroad man, on looking into the system was so impressed with its practicability and importance that he at once arranged with Mr. Robinson to make an installation of the system on his road. This was in 1870. At that time Mr. Theodore N. Ely, now chief of motive power (1906) of the Pennsylvania railroad, was assistant superintendent of the Philadelphia & Erie, and, under direction of Mr. Baldwin, furnished Mr. Robinson with all the facilities and material necessary for prosecuting the work of installation. This installation was made at Kinzua, Pa., and after a little experimenting was soon in perfect working order, performing all claimed for it, and considered satisfactory by the railroad company. This was a normally open-circuit wire system, however, controlled by track levers, as above described, in connection with the model. As soon as it was found to be working perfectly and accomplishing all claimed for it, Mr. Robinson, who aimed to be the most severe critic of his own work, entered systematically into a deeper study of the system from the standpoint of a railroad man, with a view of finding the weak points in it, if any existed. He soon discovered the following serious defects, which are inherent in all normally open circuit or wire systems of automatic signaling, without exception. Such systems are extremely limited in their functions, and may, under certain circumstances, show a SAFETY signal when the danger actually exists which they are designed to avert, as in the following cases: First: A train enters regularly upon the section and sets the signal at danger; the train breaks in two, the forward part passes off the section, reverses the signal and shows ALL CLEAR behind that portion of the train remaining on the section; and a following train, lured on by the false signal ALL CLEAR, dashes into the stalled portion of the preceding train left standing on the section. This is extremely liable to happen on sharp curves and grades, where breaks are not of uncommon occurrence. Second: A train may enter within the section from the opposite end or from a siding, thus blocking the track, while the signal, not having been affected, shows ALL CLEAR as before, a false signal again. Third: If a line wire break or other connection be interfered with accidentally or maliciously, or the battery fail from any cause, the signal will invariably show ALL CLEAR, under every train passing over the section, a false signal again. Mr. Robinson at this early date recognized the above serious objections as inseparable from open circuit system of signaling, apparently, before these defects were recognized by any one else, and at once entered upon the solution of the problem presented, of eliminating these objections by producing a signal system which would meet all the requirements of safe and efficient railroading. He reasoned, first, that to accomplish this result every car and every pair of wheels in the train must have controlling power over the signal throughout every inch of the block section, and second, the signal should go to danger by gravity, the electric current being used to hold it at safety. Could these two results be accomplished? Could the rails be used in any way to carry the primary current in a reliable manner? Manifestly not by any open circuit means, for the reason that sections of rails of even moderate length, on open circuit, would form a good ground, especially in damp or wet weather, thus keeping the circuit closed continuously and preventing any operation of any kind. He at once cast aside this open rail circuit idea as fruitless, and having previously, in 1869-70, used the short circuiting principle in his model, as above stated, he concluded that this principle presented the only possible solution of the problem. He then made drawings of the closed rail circuit system substantially as it is used today, and in 1871 applied for a patent thereon, broadly covering the closed rail circuit system. In 1872 he made an exhibition of this system at the State Fair, held at Erie, Pa. Here he placed a large gong on the end of one of the buildings, on the outside, and inside he had a track made in sections placed in a long water tank made for the purpose. The track was covered several inches deep with water and the running gear of the car model was similarly immersed. The system was connected on the short circuit principle through the rails. Wires connected the gong with the back contact of the track relay. The water had no perceptible effect on the operation of the apparatus, and when the car was run on the signal section it short circuited the current from the relay, which, releasing its armature, closed circuit through its back contact and thus through the magnet of the gong circuit, thus setting the gong ringing loud enough to be heard all over the grounds. On running the car off the section the current returned to the relay energizing the same and thus opening the gong circuit at the back contact of the relay, thereby causing the gong to cease ringing. The whole operation was perfect, demonstrating the successful operation of the closed circuit system, and attracted great crowds of people as well as the marked attention of practical railroad men. It will be understood, of course, that the local circuit may be normally open as above described and used, or normally closed as now commonly used, according to the exigencies or requirements, or preferences of the parties using the same, and when desired, a visual signal may be substituted for the audible signal above described. These are all minor details not involving separate invention. Mr. Robinson had previously explained the new closed rail circuit system to Mr. Baldwin, who was greatly interested and expressed his confidence in it and requested Mr. Robinson to install the system at Kinzua, where he had already installed the open circuit wire system. Robinson's Closed Rail Circuit System Fig. 1. As all the signal apparatus, relays, batteries, office switches and overlapping devices were already in operation there, it took but a short time to convert this open circuit system into a closed rail circuit system. The first experiments proved conclusively that the system would work. The track, however, was in a fearfully unsuitable condition for the purpose. The light rails were fished together by a four foot wooden bar on the outside, and a twelve inch fish plate on the inside. There were two holes through the iron fish plate, allowing one bolt for each rail and four holes through the wooden bar, two for each rail. However, with a little care he managed to get the current working through the whole length of the section about a mile and a quarter in length. It was evident, however, that on such a section as this a rail bond of some kind would be necessary for reliable, continuous service, and here, at this time, in 1872 Mr. Robinson conceived the invention of the bond wire method of electrically connecting the rails, now in universal use, or its equivalent, on every electric railway throughout the world using the rails for a return. As it had been determined to lay new rails at Kinzua, another installation of the closed rail circuit system was ordered and immediately made at Irvineton, Pa. This signal is illustrated in Fig. 1. It will be observed that the above installation, like that at Kinzua, not only displays a visual block signal, but also operates in connection therewith a loud gong which has been easily heard at a distance of a half mile, and was really heard by passengers in trains passing, with closed windows. An engineer could not possibly pass without hearing it. A wire is seen at the upper part of the signal box, running out to the right. This is an overlapping signal wire. A tell-tale bell was also placed in the station, indicating the actual position of the signal, and also a manual switch, whereby the agent could at any time cut off or short circuit the track battery and expose the danger signal against a train and instantly receive a return signal when the danger signal was actually exposed. The Irvineton installation worked perfectly from the first never failing. The locomotive engineers were delighted with it and soon gave it the name of "The old reliable." THE ROBINSON CLOSED RAIL CIRCUIT. Drawing of a closed rail circuit Fig. 2. The Robinson closed rail circuit, which now forms the basis, according to the best information, of every efficient automatic electric, electro-pneumatic and electrically controlled fluid pressure system throughout the world, is illustrated in its simplest form, in Fig. 2. This figure shows the railroad track divided into sections, a mile more or less in length, the section rails being insulated from adjacent sections. A light battery has its terminals connected to the opposite rails at one end of the section and at the other end a relay magnet has its terminals connected to the opposite rails. Thus the current passes through the whole length of the section, keeping the relay on continuously closed circuit and magnetized as its normal condition. The relay thus keeps the secondary circuit, which directly controls the signal, normally closed, whereby the signal is normally held in a position indicating safety. When a train enters upon the section, the wheels and axles, connecting the opposite rails thereof, short circuit the current from the relay, which instantly releases its armature, thus opening the signal circuit. The signal is then instantly thrown to the danger position by means of a counterbalance. The signal may be of the enclosed disk type, electro-mechanical, electro-pneumatic, electrically controlled gas, or of any other kind. The Robinson patented system is broad, basic and a generic creation; it is not limited to any specific construction or arrangement of signal but covers all kinds. In expounding the early history of the art of automatic signaling, the following photographic reproductions from some of Robinson's early circulars and patents will be of interest. The following sections on Curve, Tunnel, Station, Switch and Draw-Bridge Signals are a photographic reproduction from a circular issued by Mr. Robinson in 1870: CURVE AND TUNNEL SIGNALS. A train approaching a curve will throw up a red signal around the curve as a warning to trains from the opposite direction, and will also exhibit a signal in its rear. Thus, collisions from front or rear are guarded against. These signals may be used throughout the whole extent of a road. In entering a tunnel a train will exhibit a signal at the other end to indicate its entry, and when it gets through it will lower the signal and ring a bell at the opposite end to indicate its exit. STATION SIGNALS. A train when it leaves a station, and at various points as it passes, will indicate to the stations along the line, its Location, Direction, Rapidity and Length. Thus all necessary information regarding moving trains will be automatically announced every few minutes at the stations. SWITCH AND DRAW-BRIDGE SIGNALS. If a switch or draw-bridge is misplaced an approaching train will set an alarm ringing at the station and will also exhibit a red signal ahead of the train as a warning to the engineer that the switch is misplaced. The following heading and sections are photographic reproductions of parts of a circular issued by Mr. Robinson at the time of its date, "September, 1872." It will be observed that certain of these sections are the same as above reproduced from the circular of 1870. It will be noted also that the description of the system begun after the heading is not here completed, for the reason that a full description is found elsewhere in this history. Robinson's improved systems of electric railway signals For Switches, Draw-bridges, Crossings, Curves, Cuts, and Tunnels; also, to indicate the Location, Direction, Rapidity, and Length of Trains. IMPORTANT IMPROVEMENTS.—ELECTRIC SIGNALING WITHOUT TRACK INSTRUMENTS, OR LINE WIRES. THE NEW SYSTEM. The operation of this system is as follows: A railroad track is divided into sections of any desired length, say one mile, more or less, by separating the abutting rails from metallic contact with the adjacent sections, but preserving metallic continuity throughout the length of the section. The insulation of the abutting rails is accomplished CURVE AND TUNNEL SIGNALS. A train approaching a curve throws up a red signal around the curve, as a warning to trains from the opposite direction, and also exhibits a signal in its rear. Thus, collisions from front or rear are guarded against. These signals may be used throughout the whole extent of a road. In entering a tunnel a train exhibits a signal at the other end to indicate its entry, and when it gets through it exhibits a signal at the opposite end to indicate its exit. STATION SIGNALS. A train when it leaves a station, and at various points as it passes, indicates to the stations along the line, its Location, Direction, Rapidity, and Length. Thus all necessary information regarding moving trains is automatically announced every few minutes at the stations. The batteries for operating the signals will last for months without attention, and one man can readily attend to all the signals and batteries throughout the whole extent of a road. In all cases, where practicable, the signal wire should be carried through the coils of a bell-magnet in the nearest office. By this means the operator is informed when the battery power is decreasing, and warned that it requires renewing. Office connections can be made, when desired, so that the signals may be operated by a telegraph key from the office, as well as by passing trains. The signal wires may be tapped at intervals all along the line, and led into small cast iron boxes placed conveniently on the telegraph poles. Conductors of all trains, furnished with keys to these boxes, can, in case of special accident, go to the nearest box, touch a key within the same, and thus set danger signals at some distance in front and rear of their trains. The telegraph keys in these boxes not only set the danger signals as described, but they also place the said signals, for the time being, entirely out of control of moving trains. THE CLOSED CIRCUIT. The new system, as described, with closed circuit, is the best ever devised for "block-signaling," since the failure of the battery through neglect or otherwise, cannot possibly be productive of disastrous results to the train, however implicitly the signals may be relied on. From the French of Feb. 1872 [Translation]. 88th claim. "Connecting a battery B5, and a magnet M5 with the rails a9, b9, of a section of railroad track C5 in such a manner that when said rails are joined by a metallic bridge, the electric current will be diverted from the magnet M5, but so that when said bridging device is removed from said section C5 the electric current will be free to pass through and charge the magnet M5." 93d. "A signal or signals audible or visual in combination with the battery B5 and the rails of a railroad track, the whole being arranged to actuate the signal or signals, substantially as described." William Robinson. St. Petersburg, Clarion County, Pa., September, 1872. It will be observed that some of the foregoing sections refer to the open circuit system, some specifically to the closed circuit system and some are applicable to either or both. The following is a photographic reproduction of a postal card issued and distributed broadcast by Mr. Robinson at the time of its date, "May, 1873." It needs no comments. ROBINSON'S They work as AUTOMATIC BLOCKS with tell-tale alarms, OFFICE, STATION, ROAD CROSSING and SWITCH SIGNALS, and BROKEN RAIL DETECTORS. These signals have worked uninterruptedly through last winter regardless of rain, snow, slush or sunshine. Descriptive circulars on application. May 1873.WM. ROBINSON, St. Petersburg, Pa. Illustration from Robinson's Circular Fig. 3. It is pointed out that the above illustration of January, 1874, shows the Robinson closed track circuit, as heretofore described, the relay R and the track battery I forming a part thereof, the signal actuating magnet E, the signal C operated thereby, the circuit wires of said magnet E connected to, and controlled by, the relay R, and the overlapping or distant signal L, with its circuit H controlled absolutely by the position of the signal C, the whole showing a complete closed track circuit overlapping system, with home and distant signals. The following sections are from this circular of January, 1874: "When it is desired to operate a secondary signal thrown forward or back of the primary, a line wire H is used, attached to the primary signal C in such a way that the secondary signal cannot possibly operate unless the primary signal C is first exposed, thus closing circuit on the wire H. The primary signal battery K is used to operate the secondary signal." "To set the signal from an intermediate station a wire from each rail of the section A is run into the station. When these wires are connected by a key, the current from the battery I is placed on short circuit, and the signal exposed as before." (See Fig. 7.) "The following functions may be embraced in the signals of a single section. BLOCK SIGNALING, both automatic and manipulated, SWITCH, DRAWBRIDGE, ROAD-CROSSING, and STATION-APPROACH SIGNALING, and BROKEN RAIL DETECTING." "In this system it will be observed that, since the signal is exposed mechanically, any tampering with the rails or connections, or failure of the battery, will invariably result in exposing the signal; any error therefore which may occur from any cause will be in behalf of safety. It is impossible to show safety when the danger exists which the signal is designed to avert." During the early seventies Mr. Robinson made other closed rail circuit installations on the Philadelphia & Erie and other railroads in Pennsylvania and Maryland. Visit of the Pennsylvania R.R. Officials On October 24, 1873, a special inspection train of the Pennsylvania railroad passed over the Philadelphia & Erie railroad, westward. The Pennsylvania R.R. officials aboard were: Mr. A. J. Cassatt, at that time general manager; Mr. Gardner, general superintendent; Mr. Lewis, controller; Mr. Robert Pitcairn, superintendent western division, and Mr. Frank Thomson, superintendent motive power. Mr. Wm. A. Baldwin, general superintendent of the P. & E. road, was of the party, and Mr. Robinson joined the party on the latter road, and continued with it through to Erie, which was reached in the evening. Stops were made at Ridgway on the Middle division and at Irvineton on the Western division to examine the Robinson closed circuit rail system of signals, which were in full operation at those points. A thorough examination and various tests were made, to all of which the signals responded promptly and perfectly. The following is from a letter by Mr. Robinson to his brother on October 25, 1873: "Mr. Baldwin could not say enough in favor of the signals." * * * "Of course I remained in the background, except, as to giving explanations. After a while Cassatt, Pitcairn and Thomson got into a discussion of the battery and other points, and called me into the ring to enter into the discussion, and it was quite animated for some time. Pitcairn proceeded to give his idea of what a signal should be, and Mr. Baldwin and the rest proceeded to show him that this, was exactly his ideal." "Mr. Gardner, after learning modus operandi from diagrams &c. proceeded to lay down the law to the rest, demonstrating how they would have 'prevented those accidents.'" "They were all very much pleased with the signals but their operation seemed such a surprise that I judge it will take them several days to think over and realize the actual operation and importance of the thing." Robinson's Work in New England In December, 1875, Mr. Robinson went to Boston and took up his residence there. In January, 1876, he made an installation of his closed rail circuit system between Elm street and North avenue, West Somerville, on a branch of the Boston and Lowell railroad. This installation worked perfectly from the beginning. The Emperor of Brazil Examines the Robinson Signal System In June, 1876, His Imperial Majesty, Dom Pedro II, Emperor of Brazil, being then in Boston, graciously accepted an invitation from Mr. Robinson to examine his Wireless Signal System in operation on the Boston & Lowell railroad. Accordingly, on June 14, they proceeded together by special train to West Somerville for the purpose. The following is an account of the visit, from the Boston Post of June 15, 1876: "DOM PEDRO II. "His Majesty Witnesses the Operations of Railroad Signals. "Though the visit of His Majesty, the Emperor of Brazil, to this city has been a brief one, yet it is not hazardous to say that no other crowned head or representative of royalty who has ever appeared in Boston has more closely inspected the places where centre arts, sciences and manufacturers than he. "In compliance with an invitation, the Dom proceeded yesterday morning to witness the workings of Robinson's Wireless Signal System, now in operation on a portion of the Lowell railroad. The Emperor and several members of his suit took passage on board a special train on the Lowell railroad soon after 8 o'clock yesterday morning and arrived at the West Somerville station about 8:30, where they were met by Professor Robinson, who at once began to explain to the royal party his system. At Elm street a large visual signal is placed which is controlled by the current from a single cell of a battery connected with the rail sections at North avenue, no line wires whatever being used. While the Emperor watched the signal at Elm street trains were run over the whole length of the signal section in both directions. As soon as the train entered upon the section at either end, the signal, without a moment's delay, showed the track "blocked," and when the train passed off the section it instantly changed the signal to "all clear." Then a rail was torn up, and almost instantly thereafter the signal denoted "danger" and remained so until the rail was restored and properly coupled up, when it as quickly changed to "all right." Mr. Robinson gave various other demonstrations illustrating the working of the system. To all the tests the signal instantly responded. His Majesty was much interested, and entered into a somewhat lengthy discussion with Professor Robinson in regard to the operations which he had witnessed. The Emperor's questions displayed profound scientific knowledge, and he fully comprehended the system. At the conclusion of the experiment Dom Pedro thanked Professor Robinson for his kindness in explaining and illustrating his system, and invited him to communicate with the Brazilian government with a view to introducing the system in Brazil. On the return of the party to the Lowell depot in Boston, the Emperor was received with great applause, which he politely acknowledged by waving his hat." It will be interesting to note that on June 14, 1876, the day the Emperor inspected the Robinson Signal System at West Somerville, the battery had been in operation exactly 180 days without any attention whatever except that on two occasions a little water had been added to make up for evaporation, the signal working perfectly all that time and the battery with full strength. Robinson's Electro-Mechanical Signal in Operation Fig. 4. The following is from a report on the above signal by the station agent at Elm street, dated June 2, 1877, eighteen months after it had been installed: "Robinson's Electric Signal at this place has been working uninterruptedly since it was first put in operation. * * * The signal is entirely reliable." The above signal continued to work perfectly for a number of years until the signal post, which was of wood, rotted down. Drawing of a machine Fig. 4a. The signal mechanism used on the Robinson signal at Elm street was of the electro-mechanical type. Figure 4 is a half tone of the identical signal mechanism in operation there when the Emperor of Brazil examined the system with Mr. Robinson, on June 14, 1876. It is pointed out that the above signal mechanism, Fig. 4, shows a battery or pole changing attachment which is more clearly shown in Fig. 4a, reproduced from Robinson's British patent No. 3479 of August 29, 1879. In this device the movement of the cam i2 not only changes the battery but changes the polarity through the magnet M2, which may be placed anywhere and used for any purpose. A special device for the same purpose was used not only in connection with the relay on the West Somerville signal, but on many others installed by Mr. Robinson. This battery and pole changing device is more fully described in Robinson's U.S. patent, August 25, 1874, No. 154,520, Automatic Commutator; Application filed July 18, 1873. The following extract therefrom, and claim, may be interesting: "It will be observed also, that while the actual change of battery may be caused to take place when the magnet attracts its armature, yet I prefer to arrange it so that no change of connections shall take place when the armature is attracted, the actual change taking place only during the reverse movement of the armature, caused by the retractile force of the spring. Furthermore, when desired, the batteries may be so connected in circuit that reverse currents shall be passed through the magnets every time the batteries are changed." Claim 2. "In combination with the electro-magnetic commutator having the described circuit connections, the rail sections A'A*, the one closing the circuit through the commutator, and thereby determining the battery to be connected to the other rail section, substantially as and for the purpose set forth." It must be admitted that there does not seem to be a very long step between the disclosures of this patent and the present method of operating a distant signal by reversing current through a rail section. It will be observed that in this patent one rail is used as a return for a plurality of batteries connected to independent opposite rail sections. In an autograph letter addressed to the author by Professor Henry, secretary of the Smithsonian Institution, under date of October 14, 1875, the Professor discusses Robinson's peculiar method of using batteries in signaling by which he obtained the above wonderful durability of 180 days or more without renewal, and pronounced the results obtained "very remarkable." His discussion of the subject is somewhat suggestive of the principles of the storage battery. Switches In 1876, 7 and 8, Mr. Robinson made a number of installations on the Boston and Providence, Old Colony and the Boston, Lowell and Nashua railroads. On the latter road, at Wilmington Junction, he equipped two parallel sections of the double track, including six switches, in this short space, five of them connected with one of the blocks. These sections were arranged as regular closed circuit blocks, operative under the moving trains. The switches were also connected up in such a way that every switch had to be closed and locked for the main line or the danger signal would be exposed against approaching trains. This installation was made in 1876. The switch connection applied to these switches is shown in Fig. 5 and a general plan of the same is illustrated in Fig. 6. Both of these figures are reproductions from Robinson's aforesaid British patent of 1879. Drawing of a machine Fig. 5. Drawing of a track Fig. 6. It will be observed that when the switch is on the main line the wires 7, 8 are connected by the plug 6 on the switch connection, thus completing a working circuit through the rails and around the switch, but when the switch is placed for a siding the wires 7 and 9 are connected by the plug 5, thus short circuiting the current from the magnet M, thus producing the same effect as would the presence of a train on the section. It is always better to short circuit the current than trust to the mere opening of circuit since short circuiting is sure to produce instantaneous results. It will be observed, however, that in the above case the movement of the switch connection both opens the rail circuit and short circuits the current from the relay. It may be here stated that Mr. Robinson equipped three switches in one closed circuit block, in the manner described above, on the Philadelphia and Erie railroad in 1873. Drawing of a track Fig. 7. Fig. 7, from Robinson's English patent of 1879, aforesaid, shows the switch G arranged to operate the signal by hand from an office, station or telegraph post by the roadside, as heretofore described. Drawbridges About the time he made the Wilmington installations above described, Mr. Robinson made an installation of his system also on the Old Colony railroad, in which one block signal section at Somerset included a drawbridge. He included the track rails of the drawbridge in the track circuit in such a way that the withdrawing or loosening of any one of the bridge lock-bolts would display the danger signal, which remained exposed until the bridge and its lock-bolts were all restored to their normal condition insuring safety. Tunnels Long wet tunnels present peculiar difficulties to the reliable operation of the rail circuit; and yet these difficulties are readily overcome by including one or more additional relays in the signal section, as shown in Fig. 8, which illustrates the application of the Robinson track circuit system as applied to the Tehauntepec tunnel in California. Mr. Robinson forwarded the signals and necessary instructions, and the installation was made by Mr. Stephen D. Field, secretary of the Electrical Construction and Maintenance Co. of San Francisco. Drawing Fig. 8. Figure 8 is from a sketch made by Mr. Field in a letter dated San Francisco, March 21, 1877, addressed to Mr. Robinson. In this letter Mr. Field says: "I am just in the receipt of yours of the 12th. I had anticipated your diagram and have the signals arranged as you show. "I use the system connected up as follows: "In the tunnel the rails are buried in wet mud; outside no moisture touches them for six months of the year." It will be noted that in the above case the signal section is two miles long, the tunnel being one mile long, with its rails "buried in wet mud," and the section extending one-half mile at either end of the tunnel. An extra relay and battery are placed in the center of the section connected up as shown. Thus, where conditions require, a signal section may be divided up into a number of sub-sections. Later advices showed that the above signals worked perfectly and gave entire satisfaction. Insulated Joints In 1872 and the early seventies Mr. Robinson insulated the rail joints to form the sections by wooden bars, substantially as shown in Fig. 9. Fig. 9. Drawing Fig. 10. In 1876 and later he usually insulated the joints as shown in Fig. 10, using the Fisher & Norris trussed joint as a basis. Vulcanized fiber is placed between the bottom of the rail ends and the base plate, and fiber is placed between the flanges of the rails and the forelocks, and fiber, the shape of the rail section is placed between the ends of the adjacent rails, all as shown in Fig. 10. This makes an excellent insulated joint, both mechanically and electrically. Rail Bonding Dry rust forming between the fish plates and the rails of the track, at the joints, makes a poor conductor, and hence the low current, from only one or two cells of battery used in the rail circuit for signaling is very liable to find sufficient resistance at the joints from this cause to prevent the continuous passage of the current through the rails to the relay. Mr. Robinson discovered this difficulty in his first experiments in rail signaling in 1872 and the necessity for making a reliable electrical connection from rail to rail in order to insure the reliability of his closed circuit signal system. As heretofore stated, therefore, he at that time conceived the invention of the bond wire, Fig. 11, for this purpose, the connection to be made by drilling holes in the adjacent rails, driving the ends of the wires tightly into these holes, and making the connection so close that there would be no room for moisture to penetrate or rust to form. And as an alternative form he proposed to secure the ends of the wire, or of a plate, to the adjacent rails by soldering, as shown in Fig. 12. In those early days there were serious technical objections to both of these methods. First: The difficulty and expense of boring holes in all the rails of the section and connecting them up, and the difficulty of getting the railroad company to consent to such an innovation to test what at that time might be regarded as an experiment, and Second: Soldering seemed impracticable on account of the difficulty of heating up the rail quickly enough at the required point. Mr. Robinson, therefore, postponed the application of the bond wire until he could secure better facilities for applying and using it. He, meantime, experimented along other lines, however, for the purpose of securing good electrical connection between adjacent rails without boring holes therein. One of these methods was very successful. It consisted in the use of elastic split springs having their ends resting on the flanges of the adjacent rails, and held in place by small blocks secured to the ties. The passing of a train depressing the rails slightly caused a slight frictional movement between the rails and the springs, thus preserving good electrical contact. In the West Somerville installation, near Boston, made in January, 1876, as heretofore described, Mr. Robinson used the bond wire shown in Fig. 11. In applying this, holes were bored in the rails and the wire, fitting the holes as closely as possible, were forced in. A semi-circular punch was then carefully used to set the metal up close around the wire. There has been no better bond wire devised since then except in mechanical construction. Bonds of various designs have been made heavier, and with heavier end plugs for mechanical connection to the rails. These are good features as they render the bond less liable to breakage, and, as is well known, for electric railroads they should be much heavier than required in signaling, for the sake of conductivity. A bond wire, to get best results, should be homogeneous, made of a single piece of metal, or if made of several pieces, all the pieces should be welded, or at least, soldered together. They should be of sufficient length to insure flexibility without disturbing the connection if the rails should move relatively to each other, and the whole circumferential surface of the plug end, or its equivalent, when possible, should be in the closest possible direct contact with the rail, that is, the bond plug should make connection with the rail as nearly as possible—homogeneous. Welding would be the ideal connection but it is not always practicable. The reason for the above is obvious: that there should be no room left between the bond and rail for rust to form. It follows then that a bond held in position by an independent plug which renders it necessary for the current to pass from the bond to the intermediate plug and from that plug to the rail, is not the best form of bond, for the reason that it presents a double surface on which rust may form. Figures 11 and 12 show Robinson's bond wires and strips of 1872, Fig. 12 showing the bond soldered to the rail. In 1876, 7 and 8 he used on various roads in the vicinity of Boston, the bond shown in Fig. 11. In 1876 he used on the Boston and Providence road the bond shown in Figs. 11, 13 and 14. In the form shown in Fig. 13, holes are bored through the upper ends of the plugs, which were slightly tapering. The wire was forced through these holes, and the wire and plugs were then soldered together with hard solder. The plugs being materially larger than the wire, could readily be driven home with a good deal of force, thus insuring an excellent electrical connection without endangering the wire. Drawing Fig. 11. Drawing Fig. 12. Drawing Fig. 13. Drawing Fig. 14. Drawing Fig. 15. Drawing Fig. 16. In Robinson's British patent No. 3479, of August 29, 1879, aforesaid, he illustrated the form of bond shown in Figs. 15 and 16, which is an equivalent of that shown in Fig. 14, used by him in 1876. Mr. Robinson claimed the bond wire broadly in this British patent, in the following claims: 10. "The wire A3 in combination with the rails B3, B3, and securely fastened thereto, for the purpose described. 11. "In combination the wire A3, the rails B3, B3, and the rivets a3, a3, the whole arranged substantially as described for the purpose of securing electrical continuity between said rails." The above is believed to be the first disclosure of means for electrically connecting rails by a bond wire in any patent, although Robinson had disclosed it to various parties, and used it on installations years before. On the subject of rail bonding the following bit of evidence may be of interest: In a letter dated Baltimore, October 29, 1874, addressed to Mr. Robinson by Mr. J. H. C. Watts, of Watts & Co., manufacturers of Robinson's signal apparatus, he says: "Am afraid your idea of soldering a strip of copper to the rails will prove very troublesome in carrying out, as it is a most difficult matter to heat so large a body of iron sufficiently to make a sure joint such as you require, or that will stand the jarring of passing trains, &c., to say nothing of sneak thieves who abound wherever copper is lying around loose. I know however you scoff at theory so will 'dry up.'" The electric dynamo of today has removed the above pointed out difficulty. Bond wires or strips are now welded to the adjacent rails for the purpose of securing reliable electrical connection between them. Welding is soldering, according to the definition of the term. Thus, the Encyclopedic dictionary gives the definition: Solder: "To unite or cement together in any way. * * * In autogenous soldering the two pieces are directly united by the partial fusion of their contiguous surfaces." Thus, more than thirty years ago Robinson proposed to solder bond wires or strips to the rails for the purpose of securing good electrical continuity between the same. But it became necessary to wait some twenty years for the development of a commercially practical process for accomplishing this result. This is found in the modern electric welding process. Robinson's object was to secure a perfectly homogeneous joint or connection between the bond and the rail. His invention, in this connection, consisted in a metallic bond arranged for electrically connecting adjacent rails of the track and means for forming a homogeneous connection between the bond and the rails. This embraces any mode of accomplishing that result. Robinson had simply anticipated the electric process by some twenty years, but that process now accomplishes the result in a simple manner impossible thirty years ago. The splice bars now welded to opposite sides of street rails in many places are used primarily for the purpose of electrically bonding the rails; incidentally they serve the double purpose of also making a good joint mechanically. Every electric railroad uses the bond wire or plate in some form, originally invented and used by Robinson, for electrically bonding rails together. Thus, it is clear, this simple invention of Robinson made more than thirty years ago, an outgrowth of his original creation of the closed rail circuit system, has made possible the electric railroading of today, and the method of rail-bonding is now used on every electric railway using a rail return, throughout the world. Drawing ROBINSON'S LATEST ELECTRIC SIGNALING APPARATUS. Figure 17 is a reproduction from a postal card dated September, 1875, and issued at that time. It illustrates means for operating a positive safety signal in the cab of a locomotive when the track ahead is clear and safe, the operative current passing through the rails from the distant end of the track section upon which the train is entering. This system is elaborated in Robinson's British patent of August 29, 1879, where it is shown operatively applied to a single track in such a manner as to operate a signal on a locomotive approaching from either direction, the operative current coming from the opposite end of the section—no line wires being used. It is not thought necessary, therefore, to more fully describe the system here. In General The scriptural injunction, "Prove all things, hold fast that which is good," is the key note of scientific progress. He who would discover truth must not accept anything because it is popularly accepted, or reject anything because it is popularly rejected; nor must he regard anything as impossible because never heretofore accomplished, although perhaps attempted by the most able scientists. While giving full weight to principles and laws demonstrated and verified by original investigations, he must bear in mind that those principles and laws may be capable of various combinations and interpretations; that the popular interpretation may not be capable of general application, and if not, it must be erroneous. In short, he must enter upon his investigations systematically, independently and untrammeled by prejudice. These remarks apply to electrical science with great force at the present time. Those who enter this field to advantage should be men of culture, of theoretical knowledge, and eminently practical. These facts are illustrated by the efforts heretofore put forth in Europe and the United States to develop systems of rail signaling. Such efforts, in the early days, appear to have been exerted principally by theorists whose propositions and complications prove them to be not only ignorant of some of the fundamental principles of electrical science, but also, some of them, extremely unpractical. That the efforts in this direction may be fairly understood we will direct attention to a few of the systems of rail signaling proposed,—those which have elicited most attention—giving outline illustrations of some of the circuits which form their bases, and pointing out their defects and merits. Early Rail Systems So far as we have knowledge, the idea of using the rails as conductors for electric signaling purposes was first suggested in an English patent of 1848. This was merely a suggestion, however, and no attempt was made to describe any specific method of using the rails for the purpose. In 1853, however, an English patent was granted to George Dugmore and George Millward, in which is described a method proposed for using the rails as conductors. The design of the invention is to communicate between trains on the same line, and between trains and stations, for which purpose it is proposed to use long sections of rails. The unpractical part of this system is that to make it operate it is necessary, as the inventors say, to insulate the opposite wheels of all the carriages from each other, in order that electrical connection may not be established between the opposite rail line by the wheels and axle. Imagine one of our gigantic locomotives having its opposite drivers electrically insulated from one another! Figure 18 represents the signal system described in William Bull's English patent of October 31, 1860. In this system, it will be observed, the rail sections used are short, "twenty feet, more or less," and are the terminals of line wires which connect with the battery and magnet at the station. The signal at the station is visual and consists of an indicator operated by wheel work actuated or controlled by the electro-magnet M shown in the diagram. The signal as described, moved in one direction only, by a step-by-step movement. In the following diagram M represents magnet and B battery. Drawing Fig. 18. Mr. Bull says: "At the stations at which it is required that the progress of the train shall be indicated, a battery is fixed and in connection therewith a dial or indicator, both of which are also connected with the line permanent way wire, the terminals of which are the pairs of insulated rails, as before described. "When the train arrives at the contact points on the line, the electric circuit would be completed by the wheels of the engine connecting the two insulated rails, when the current would flow and actuate the electro-magnetic armature," &c. The mode of insulating the rails from each other is described by Bull as follows:—"Between the end of the rails, and also between the joint plates and rail ends, I insert a thin piece of leather, mill-board, gutta percha, or other suitable substance, suitable for cutting off metallic contact, and thereby insulate one rail of twenty feet, more or less, as may be necessary." In Pope, in a description of his experiment at Charlestown, in a paper read by him before the New York Society of Practical Engineers—of which, by the way, Mr. Robinson was a charter member—and subsequently published, admits that he did not use the "rail circuit" at all in any proper sense of the term. On the contrary, he used line wires forming his main circuit terminating in short sections of rails, forty-two feet in length according to my recollection, that is, the length of one rail. The train passing over the short rail section at one point closed the circuit through the line wires, thus exposing the signal, which was held in place by a "detent." The train, having reached a distant point, passed over another similar short section of rails, closing circuit through another magnet which released the "detent" and reversed the signal. It will be observed that the essential features of the device used in Pope's experiment, on which he laid great stress, and described in Bull's patent, are identical, that is, the circuit closer consists, in the one case of a section of rails "twenty feet long, more or less," on open circuit, and the other identically the same, but with a rail section forty-two feet long, both using line wires. Pope and his friends heralded this experiment—a revival of Bull's device—as demonstrating a wonderful invention on the part of Pope. What Robinson Has Done in Automatic Electric Signaling
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