Opinion of the Court. wheels and axles of the train will form an electrical connection between the opposite insulated rails, and a circuit will be formed between the conductor C and the conductor Z, traversing wires 1 and 2, magnet M, and wire 3, and the signal attached to M will consequently be displayed. Upon the arrival of the train at a1 the same operation will be repeated, and another connection formed between Cand Z, traversing the wires 4 and 5, magnet M1, and wire 6, while at the same time a portion of the current will traverse the branch-wire 7, magnet m, and wire 8. Thus the signal attached to M1 will be actuated, and simultaneously the action of the magnet m will release or reverse the action of the first mentioned signal. Upon reaching thẹ point a2 the closing of the circuit by the train will, in like manner, cause the signal attached to M2 to be displayed, and the signal last displayed by M1 to be withdrawn. In this manner any required number of such signals may be operated by means of a single battery. "The respective resistances of the several circuits should be so adjusted that they will be as nearly as possible cqual to each other, as a much more perfect action of the apparatus will be secured thereby. "On a railroad having a double track two separate series of signals, one series for each track, may be connected with the conductors C and Z of a single battery, if required. If preferable they may be also operated by means of separate batteries and separate conductors. "In cases where it is required to operate a large number of signals, extending along the road for a distance of many miles, the two conductors C and Z may be extended the entire distance, and a number of batteries attached at convenient intervals, say, for instance, from five to ten miles apart. The several batteries should all be placed with their positive poles in connection with the wire C, and their negative poles in connection with the wire Z, when they will virtually form one large battery, and the principle of operation will remain the same as that herein before described. "I do not desire to confine myself to the use of any particular form of visual or audible signals, nor to the particular devices Opinion of the Court. herein described for closing the electric circuit at points from which a signal is to be operated. Instead of the circuit being closed automatically by the train itself, it may be closed by a signalman by means of a key or switch, or otherwise. "I claim as my invention "1. The battery B, in combination with the positive and negative conductors C and Z, two or more electro-magnets, M, M1, M2, for actuating or causing to be actuated visual or audible signals, and two or more circuit-closers, a, a1, a2, placed at intervals along the line of a railroad, substantially as and for the purposes specified. "2. The battery B, in combination with the positive and negative conductors C and Z, two or more electro-magnets, m, m2, m2, for releasing or reversing visual or audible signals, and two or more circuit-closers, a1 a2, placed at intervals along the line of a railroad, substantially as and for the purpose specified. "3. The combination of the battery B, conductors C and Z, circuit-closer a, and electro-magnet M, for actuating a visual or audible signal, with the circuit-closer a1, wires 5, 7, and 8, and electro-magnet m, for reversing, releasing, or stopping said signal, substantially as specified." Among several defences set up in the answer, the two chiefly relied on were, first, that Thomas S. Hall, and not Pope, the patentee, was the first inventor of the improvement claimed, and, second, that the devices used by the defendants were not an infringement of the patent: The decree below was based on the first of these defences alone, the Circuit Court finding that Hall was entitled in law to priority of invention; but we have not found it necessary to discuss the questions of fact and law embraced in this issue, as we have concluded to dispose of the case upon the ground that the defendants did not, by the devices used by them, infringe the patent of the complainants. Opinion of the Court. This diagram represents the plan of electric railroad signals, placed and put in practical operation, by the defendants, on the line of the Eastern Railroad near Boston, prior to the bringing of this suit. In comparing it with the drawing annexed to the patent, it is to be remembered that the latter represents a series of double signals in succession on the line of a railroad track, divided into blocks, while Exhibit C represents but one pair of such signals in one such block. To make it correspond with the other, as a representation, it should be imagined as being repeated in several successive blocks, constituting portions of one circuit, closed at fixed points by circuit-closers for that purpose. Mr. Pope, the patentee, drew this diagram, and, as a witness on behalf of the complainants, explains it, in comparison with the plan described in the patent, with a view to establish their identity. He says; "I have made a diagram which exhibits the apparatus which I examined, or so much of it as is material to this case, which I annex, and is marked Exhibit C. "A battery of perhaps one hundred cells is placed in the station building at Chelsea. One pole of this battery-I think the negative pole-is connected to the earth. "A conductor is attached to the other or positive pole of the battery, consisting of an insulated wire extending along parallel with the track upon poles. This wire which I examined extended toward Boston, the end remote from Chelsea being disconnected, or, as it is termed, open. A second conductor, consisting of another similar wire insulated and attached to the same poles, was arranged parallel to the first one. The second wire was open at Chelsea, and connected with the earth at its remote end. "The first mentioned wire I have shown in the diagram, and marked 'positive conductor;' the second wire is marked 'negative conductor.' At a short distance from the station a semaphoric signal is placed, consisting of a red disk balanced upon a lever. This was placed in the cupola of a small building at the side of the track. An electro-magnet was arranged with its armature attached to said lever, so that when brought into action the red disk on the other end of the lever would be Opinion of the Court. moved into a position to render it visible through an opening in the cupola. A latch or detent was placed in a position to fasten the lever after the action of the magnet had ceased, and thus continue the exhibition of the signal. A circuit-closer was placed upon the track at a point near the signal, which consisted of a lever so placed as to be depressed by the wheels of a passing train, which movement caused the circuit to be closed by pressing two springs together. When the circuit was thus closed by a passing train a connection was formed between the positive and negative conductors, and the electric current, in passing from one to the other, passed through and operated the magnet by which the signal was displayed. At a point, perhaps a mile distant, another signal was arranged in precisely the same manner in connection with a second circuit-closer, and the same positive and negative conductors. An additional circuit-closer, placed upon the track in the vicinity of this lastnamed signal was arranged to form a connection from the positive to the negative conductor by the way of a third wire running upon the poles back to the signal first mentioned, where it passed through and operated a second magnet, which lifted the latch or detent, and allowed the disk to return to a position concealing it from view. I examined two of these signals, and saw many others along the line of the road. "I find in this arrangement thus described the combination claimed in the first claim of said patent, consisting of a battery in combination with positive and negative conductors, two or more electro-magnets for operating visual signals and two or more circuit-closers placed at intervals along the line of the railroad. Also the combination claimed in the second claim of the patent, consisting of a battery in combination with positive and negative conductors, two or more electro-magnets for reversing visual signals, and two or more circuit-closers placed at intervals along the line of the railway. I also find the combination claimed in the third claim, of a battery, positive and negative conductors, a circuit-closer and electro-magnet for actuating a signal, with a second circuit-closer, wires, and a magnet for reversing said signal." Mr. Moses G. Farmer, an expert witness on behalf of the |