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combination with a battery, and with two or more circuit-closers operated by moving trains or otherwise, whereby a series of two or more visual or audi. ble signals, situated at intervals along the line of a railroad, may be operated by currents of electricity derived from a single battery, thereby obviating the inconvenience and expense of employing, as heretofore, one or more separate batteries situated at or near each signal for the purpose of actuating the same.

“In the accompanying drawing, A, A, represents a portion of the track of a railroad. At intervals of, say, a mile, more or less, sections of the said track, a, a', a, are electrically insulated from the remainder in a manner well understood, and therefore requiring no detailed description. B is a galvanic battery, of any suitable construction, and placed in any convenient location near the line of the railroad. Two wires or other conductors, C and Z, are attached to the positive and negative poles, respectively, of the battery, B, and extended to any required distance in a direction parallel or nearly so to the line of the railroad. The conductors, C and Z, may be placed on poles, and should be suitably insulated from each other and from the earth. The conductors, C and Z, are virtually prolongations of the positive and negative poles of the battery, B. Each of the insulated sections of track, a, , a?, etc., is placed at some point at or near which it is desired to erect a signal, and any required number of these may be employed to meet the requirements of any particular case. M, M1, and M’ are the electro-magnets, which actuate or display the respective signals. The said signals may be of any suitable construction, and should be provided with some suitable means of retaining them in position or action after the circuit through the magnets, M, M1, or M?, has been interrupted. m, m', and mo are magnets so arranged as to release, reverse, or stop the action of said signals, which have previously been brought into action by the magnets, M, M', and Mo.

"The operation of the apparatus is as follows: Suppose a train moving along the track, A, A, from left to right in a direction indicated by the arrow. Upon reaching the point, a, the 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, 2, 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 al the same operation will be repeated, and another connection formed between C and Z, traversing the wires, 4 and 5, magnet, M, 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 the point, a’, the closing of the circuit by the train will, in like manner, cause the signal attached to Mo 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 resistance of the several circuits should be so adjusted that they will be as nearly as possible equal 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 neg. ative 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 hereinbefore 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*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, M, M’, for actuating, or causing to be actuated, visual or audible signals, and two or more circuit-closers, a, a', a?, placed at intervals along the line of a railroad, substantially as and for the purpose specified. (2) The battery, B, in combination with the positive and

conductors, C and 2, two or more electro-magnets, m, m', m?, for releasing or reversing visual or audible signals, and two or more circuit-closers, a?, a’, 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, a', wires, 5, 7, and 8, and electro-magnet, m, for reversing, releasing, or stopping said signal, substantially as specified.

Among several defenses 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 defenses 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 é did not, by the devices used by them, infringe the patent of the complainants. These devices are illustrated by a drawing, of which the following is a copy:

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* This diagram represents the plan of electric railroad signals, placed and

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.

v.58—68

in one such block. To make it correspond with the other, as a representation, it should be imagined as being repeate. 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 towards 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 conauctor;' 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 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 last-named 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 complainants, makes the same comparison, with the result, according to his opinion, of establishing that the defendants' system is essentially the invention described in the patent. On the other hand, Prof. Henry Morton, an expert witness on

behalf of the defendants, points out two particulars, in which the plan, as practiced by the defendants and shown in Exhibit C, differs from that of the Pope patent so materially that they cannot be considered substantially the same: The first of these is, that in the patent, insulated sections of the railroad track, used, when covered by a locomotive or cars, as a circuit closer, are made essential to the combinations claimed, while they are dispensed with in the Hall system, other and independent circuit closers being employed. The second is thus described by Prof. Morton in his testimony: “I also find a difference between the plan described in the patent and that shown in Exhibit C in another regard. In the plan of the patent, the conductors, C and Z, are connected respectively with the positive and negative poles of the battery, or, as the patent itself states, are virtually prolongations of the positive and negative poles of the battery.' In the plan shown in Exhibit C, however, the conductor, C, or positive conductor only, is connected with the battery, the other conductor, Z, or, as it is called, negative conductor, having no connection with the battery. In consequence of this difference of arrangement in the system of the patent, the positive conductor, C, carries the positive current in one direction, away from the battery, and the other, or negative conductor, Z, brings the positive current in the opposite direction, or back to the battery, and thereby involves the production of circuits of different resistance for each station. In the system represented in Exhibit C, on the other hand, both the conductors, C and Z, serve to carry the positive current in the same direction, away from the battery, and should, therefore, properly be both called positive conductors. As a result of this arrangement, the current always passes through the same or equal circuits, no matter at which station the connection is made, simply changing from one to the other of these equal parallel wires at the station where the contact is effected. It is for this reason that in this system no equalization of resistance, in the sense involved in the description of the patent, is required."

It is upon these two points that the question of infringement depends. In considering them it is important to bear in mind that the patent is for a combination merely, in which all the elements were known and open to public use. No one of them is claimed to be the invention of the patentee. He does not claim them himself as separate inventions. It is simply a new combination of old and well-known devices for the accomplishment of a new and useful result that is claimed to be the invention secured by the patent. And the well-settled principles of law, heretofore applied to the construction of patents for combinations merely, must apply and govern in the present case. The object of the patented combination was the accomplishment of a particular result, that is, to work electric signals on what was known as the "block" system, by means of circuits, operated by a single battery instead of many. But this result or idea is not monopolized by the patent. The thing patented is the particular means devised by the inventor by which that result is attained, leaving it open to any other inventor to accomplish the same result by other means. To constitute identity of invention, and therefore infringement, not only must the result attained be the same, but in case the means used for its attainment is a combination of known elements, the elements combined in both cases must be the same and combined in the same way, so that each element shall perform the same function, provided, however, that the differences alleged are not merely colorable, according to the rule forbidding the use of known equivalents.

The first question we have to consider upon the issue as to infringement, is whether insulated sections of the rails, as circuit-closers, constitute an essential element in the combinations described in the patent. And that question we are constrained to answer in the affirmative. These insulated sections of track are shown and marked on the drawing which accompanies the specification, and in its descriptive part they are referred to as parts of the arrangement. It

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