Part 20

The above description is all that we have been able to obtain in relation to this plan of an electric telegraph and here introduce, figure 65, to illustrate it. The 30 needles are represented on the screen, each carrying a shade, which conceals the letter when the needle is vertical. The needle belonging to the letter F, is, however, deflected, and the letter is exposed. The screen is supposed to be at the _receiving_ station. To the left hand of the screen, 30 wires, _e, e_, are seen joined to one, _a_; the other 30 wires, _d, d_, are seen below the screen. These wires may be supposed to extend many miles, and to be joined with their corresponding wires, _c_, and also _v, v_, of the _transmitting_ station, where it will be observed, the wire, _c_, connects with the battery at one pole, and from the other pole a wire is continued and soldered to the metallic plate, _o, o_, which extend under all the 30 keys, _i, i_. These keys are each insulated, at their extremity, by being fastened to a wooden standard, L, L, to which a wire is soldered. Now, suppose the key, F, is pressed down, (the sixth key from the left,) the fluid then passes from the battery, B, through the wire to _o_, the plate; then to the key in contact with it; then to its wire, marked by the arrow; thence through the extended wire to its corresponding wire at the receiving station, denoted by the arrow; then through the coils of the multiplier, deflecting the needle, F; then returns through its wire, at the left, to the common wire, _a_; then through the extended wire to C, and the battery, of the transmitting station. In this manner any letter upon the screen may be indicated.

_Extract from the Report of the Academy of Industry, in reference to a suggestion of M. Amyot of an Electric Telegraph._

“M. Amyot announced, in a letter addressed to the Academy of Sciences, in April, 1838, that he also proposed to construct an electric telegraph. It was to consist of a single current, which would move a single needle, which needle would of itself write on paper, with mathematical precision, the correspondence which might be transmitted to the other extremity, by a simple wheel on which it should be written by means of points, differently spaced, the same as they are on the barrels of portable organs. In order to send any news then, he required to write, by means of movable characters, which must be constructed in a certain manner, and immediately it would be repeated and transcribed at the place where he wished to address it, on paper, which could be put into the hands of persons specially employed to transmit despatches. But all that method of execution, which it seems ought to move is clock work, not having been sufficiently described by the author, the _most vague uncertainty_ yet reigns as to the true construction of that apparatus, which appears to us to have been for M. Amyot, rather the occasion, than the end, of this communication; for indeed he attempted to make the possibility admitted of establishing a universal telegraphic language of his invention.”

_Edward Davy’s Electric Telegraph._[34]

The following description of Mr. Davy’s telegraph is taken from his specification and drawings, published in the Repertory of Patent Inventions. Although the specification has given the basis of his plan, yet the description contained therein, and the drawings representing his plan, are so obscure and deficient, that to have given it to the public in that form, would have represented it as perfectly impracticable. He has failed to state the number of signals which it is capable of giving. He has committed great errors in the arrangement of his wires for producing signals. He has introduced two keys, which produce the same signals as two others in the same arrangement. He has employed three extended wires for communicating from one station to another station, and by his arrangement of them, could not have obtained more than four signals. He has also very obscurely described his escapement, by which his marking cylinder is made to advance one division at a time for receiving the signals. This latter difficulty, however, we have been enabled to clear up, by a description of it in a work published by Mr. Bain. Notwithstanding the imperfections and obscurities of his specification and drawings, we have endeavoured to carry out his plan, and give it a practical shape, perhaps, as Mr. Davy originally designed it.

[34] From the Repertory of Patent Inventions, No. lxvii. New Series, London, July, 1839.—Sealed, July 4th, 1888.

As it is now described, there are 26 signals, or marks, indicating letters. The employment of four wires instead of three, or if Mr. Davy chooses to use for the common communicating wire the ground, which is perfectly practicable, it will reduce the number to three, the number he has specified. We have introduced one key more, and so arranged the two superfluous keys as to make them available. With this preliminary, we will proceed with the description.

Figure 66 represents a top view of the arrangement of the wires, mercury cups, and batteries of the _transmitting station_. The close parallel lines represent the wires, of which D, A, B and C are those which proceed to the receiving station. 1′, 2′ and 3′ are the three batteries, of which, P and N are their respective poles. The small circles formed at the termination of the wires, and marked 7, 1, 10, 2, 20, &c. are mercury cups, in which the terminating wires are immersed. The wires 1 and 20, and 2 and 10, &c. which cross each other, are not in contact, but perfectly insulated. The wires shown in this figure, are all secured permanently, with their mercury cups, to one common base board. The letters H, J, K, M, O and U represent the places of the six finger keys, used in transmitting signals. There is, also, another key at 7, for uniting the wire, D and D. In this figure, however, the keys themselves are omitted, in order to render more clear the arrangement of wires under and around them. Another figure, 67, is here introduced to illustrate the plan of one set of wires and their two keys. In figure 67 is represented, in a top view, the two wooden keys, A and B, and their axes, at E and F. G is the battery, of which, 9 is the positive pole, and 10 the negative pole. The small circles, marked 1, 2, 3, 4, 5, 6, 7 and 8 represent the mercury cups. C and C′, and also, D, are the extended wires. The keys, A and B, have each two wires, passing at right angles through the wooden lever. The wires of the key, A, are marked 1 and 2, and 5 and 6, and those of the key, B, are marked 3 and 4, and 7 and 8. These wires, directly over the mercury cups, are bent down a convenient length, so as to become immersed in the cups, when the lever is depressed, and rise out of them, when the lever is elevated. Now, if the key, A, is depressed, the cup, 1, is brought in connection with cup 2; and 5 is connected with 6, by the wires, supported by the lever, being immersed in the mercury; and the key, B, not being depressed, there is no connection of the cup 3 with 4; or 7 with 8. At X and X, under the lever, are springs, which keep the lever elevated; and, consequently, the wires out of the cups, when the keys are not pressed down.

Figure 68 represents a side view of the lever, or key, A, and its axis at E. R is the platform supporting the standard of the axis; the stationary wires; the battery, G; and the mercury cups, _a, a_ and 10. X is the spiral spring, for the purpose of carrying back the lever, after the finger is taken off and sustaining it in its elevated position. Through the centre of the spiral, passes a rod, with a head upon it at the top of the lever, to limit its upward motion. At its lower end, the rod is secured in the platform, R. 4 and 8 are the two wires supported by the lever, A, and are seen to project down directly over the mercury cups, _a_ and _a_, so that by depressing the key, they both enter the cups and form a metallic connection. The key, B, figure 67, has the same fixtures and is similarly arranged as the key, A, represented above.

Figure 69 represents a top view of die arrangement of multipliers at the _receiving_ station. R′, R′ and R′; R, R, and R are six magnetic needles, or bars, each of which move freely upon a vertical axis passing through their centres. The lower point of their axes is immersed in cups of mercury, in which also terminate the wires, I, I, I and L, L, L. The wires, D″, A′, B′ and C′, are those coming from the _transmitting_ station. A′, B′ and C′, each enter the needle arrangement, and first passing from left to right, over the magnetic bars, R′, R′ and R′, in the direction of their length, then down and under and round, making many turns, leave these three needles and pass _under_ the needles, R, R and R, and in like manner from right to left round them, making a number of turns, then pass off and unite together, in the wire, 9, which is a continuation of D″. This wire is called the _common communicating wire_,[35] and the wires, A′, B′ and C′ are called _signal wires_. At right angles, there projects from each magnetic bar, a metallic tapered arm, which rests against the studs, V, V, V, V, V, V, when the needle is undisturbed. But when the needles are made to move in the direction, to carry the arms to the left, they are brought in contact with the metallic stops, S, S, S and T, T, T. To each of these stops, it will be observed, a wire is soldered, and continued respectively from S, S, S to ̈1, ̈3, ̈5, and from T, T, T to ̈2, ̈4, ̈6. It will also be observed, that from each of the mercury cups below the magnetic bars, the wires, I and L, and I and L, and I and L, proceed and unite in pairs at, L, L, L; these three united wires are then continued, and the whole are joined in one at 8. The wires, ̈1, ̈2, ̈3, ̈4, ̈5, ̈6, are continued, in a manner hereafter to be described, and are connected with one pole of a battery. The wire, 8, is also continued and connected with the other pole. So that if any one of the needles should be made to move its arm to the left, thereby coming in contact with its metallic stop, the circuit would be complete and the current would pass along the wire, ̈1, for example, to the metallic stop, then to the arm, and to the magnetic bar; then to the axis; then to the mercury; then to the wire, I, and thence to the wire, 8. In the same manner the current would pass if any other arm was brought against _its_ metallic stop. All the wires represented in this figure are permanently secured in their places upon a common platform.

[35] A′, B′ and C′ are also, occasionally, common communicating wires.

In order to understand the combined operation of the keys and needles, figure 70 is here introduced. The right hand figure, is the same as figure 69, and the left hand the same as figure 66.

The wires, D″, A′, B′ and C′, are detached from their corresponding wires of the transmitting station, and it may be imagined that many miles of wire intervene and connect the two. In the left hand figure, those mercury cups above and below, 1 and 10, are joined by two wires passing through a moving lever, in the same manner as has been described in figure 67. We will, therefore, call the key, carrying these two connecting wires, H. In like manner the key for the cups above and below the numbers, 2 and 20, is called J; for 3 and 30, is K; for 4 and 40, is M; for 5 and 50 is O; for 6 and 60, is U. The key which connects the two mercury cups on the right and left of number 7, of the wire, D″, is called 7. There are 7 keys; two for each battery, 1′, 2′ and 3′, and each wire, A′, B′ and C′; and one for the common wire, D″.

It will now appear, that if the key, U and 7, are depressed, the cups above and below, numbers 6 and 60; and the cups on each side of number 7, will be connected together so that the current leaving, P, or the positive pole of the battery, 3′, goes to the lower cup, 50; then by the stationary cross wire to upper cup, 6; then passes to lower cup, 6, by the wire supported by the lever, U, which is now pressed down, and its ends immersed in the two cups; then along the wire, D, to the left hand cup, 7; then to the right hand cup, 7, by the wire supported by the lever, 7, and which is immersed in the two cups; then through the extended wire to D″, of the _receiving_ station; then through 9, to the two multiplying coils of the wire, C′, deflecting the arm of the needle, R, to the right, against the stop, V; and the arm of the needle, R′, to the left against the metallic stop, S, as indicated by the arrow at S; then along the extended wire, back to the lower cup, 60, of the _transmitting_ station; then to upper cup, 60, through the wire supported by the lever, U; then to N, the negative pole of the battery, 3′.

It will be observed of the two needles, R and R′, in the circuit of the same wire, C′, that if R is deflected to the right against the stop, V, then R′ will be deflected to the left against the metallic stop, S. The current, to produce these deflections, being through the wire C′, in the contrary direction to that indicated by the arrow of the wire, C′. But if R is deflected to the left against the metallic stop, T, then R′ will be deflected to the right against the stop, V. The current to produce these deflections, will then be through the wire, C′, in the direction of the arrow of that wire. The same effect is produced upon the two other pairs of needles of the wires, A′ and also B′. These contrary movements of the two needles, when a _current_ is passing, are produced by the coils being so wound, (see figure 69,) that the wire passes round one needle in a contrary direction to what it does round the other.

If, now, we depress the keys, O and 7, the cups above and below, 5 and 50, and on each side of number 7, will be connected. The fluid will then pass from P or positive pole of the battery, 3′, to the lower cup, 50; then through the key wire to upper cup, 50; then along the extended wire, C′ to the _receiving_ station; then through the coils of the multipliers, deflecting the arm of the needle, R, to the left against the metallic stop, T; and the arm of the needle, R′, to the right against the stop, V, as indicated by the arrow at V; then to wire, 9 and D″; then along the extended wire back to the _transmitting_ station, to the right hand cup, 7; then by the key wire to the left hand cup, 7; then to wire, D; then to upper cup, 5; and through the key wire to lower cup, 5; then by the cross wire to upper cup, 60, and then to N, or negative pole of the battery.

We have now shown the route of the current, when the keys, U and 7; and the keys, O and 7, were depressed. It will be observed, that when the keys, U and 7 were used, the current through the wire, D″, was from _left_ to _right_; and when the keys, O and 7, were used, the current was from _right_ to _left_. Thus, by means of the six keys, the current of each battery may be made to pass in either direction through the _common communicating_ wire, D″. By the keys, U, M, J, with 7, the current is made to pass from _left_ to _right_ along the wire, D″. By the keys, O, K, H, with 7, the current is made to pass from _right_ to _left_ along the wire, D″. By these six keys, all those various deflections of the six needles are produced, which are necessary to close the circuit of such of the wires, ̈1, ̈2, ̈3, ̈4, ̈5, ̈6, with the wire, 8, as are required for marking the signals desired, on an instrument now to be described.

Figure 71 represents a top view of that part of the instrument at the _receiving_ station, by which the signals are recorded. The seven wires on the left of the figure are a continuation of those wires, marked ̈1, ̈2, ̈3, ̈4, ̈5, ̈6, and 8, in figure 70. The first six pass through a wooden support, _b_ and _b_, and terminate upon the edge of the platinum rings, _a_, _a_, _a_, _a_, _a_ and _a_, forming a metallic contact. The six platinum rings surround a wooden insulating cylinder, _t_, which revolves upon axes in the standards, _h_ and _i_. The rings are _broad_ where they come in contact with the wooden roller, and are bevelled to an _edge_ where they come in contact with the six wires. Y represents a compound battery, with one pole of which, wire 8, from the needle arrangement, figure 70, is connected, and from the other pole the wire proceeds to the electro magnet, Z, Z; it then passes on and is brought in connection with the metallic cylinder, _d_, at the point, _g_. The cylinder, _d_, revolves upon axes, and is supported in the standards, _k_ and _l_. To the cylinder is attached a barrel, _n_, upon which is wound a cord, supporting the weight, _e_, by which the cylinder is made to revolve. C′, C′, represents a prepared fabric, such as calico, (impregnated with hydriodate of potass and muriate of lime,) and is placed between the platinum rings, _a, a, a, a, a, a_, and the metallic cylinder, _d_; _o_ is a cog wheel upon the end of the axis of the cylinder, _d_, and is connected with other machinery, omitted here, but shown in figure 72, which is a side elevation of part of figure 71: _o_ is the cog wheel, (figure 72,) on the arbor of the cylinder, _d_. B and B, are the two sides of the frame containing the clock work, and is secured to the platform, R: _d_ is a part only of the metallic cylinder, upon which is seen a portion of the prepared fabric, K. The cog wheel, _o_, drives the pinion, A, on the shaft of the fly vane, G. M is an end view of the electro magnet, (represented by Z, Z, in figure 71,) of which N and P are the two ends of the wire composing the helix. D is its armature, constructed so as to move upon an axis represented by two small circles. To the armature are connected, and capable of moving with it, two arms, E and I, which project, so as to come in contact with the pallet, _a_, of the fly, G. F is a spiral spring, one end of which is fastened to the armature, D, and the other passes through a vertical hole in the screw, S, in the bar, T, by which the armature is held up in the position now seen, when not attracted by the electro magnet. Now, if the wires, N and P, connected with battery, Y, (figure 71,) have their circuit closed, the current passing through the helix of the magnet, M, brings down the armature, D, in the direction of the arrow, which raises the arm, I, against which the pallet, _a_, of the fly vane, is resting, and releases the fly. It then makes a half revolution and is again arrested by the pallet against the lower arm, E, and the cylinder, _d_, with its fabric, has advanced a half division. If the circuit is now broken, the armature, D, is carried up by the spring, F, at the same time the arm, E, releases the pallet, _a_, and the fly makes another half revolution, and is again stopped by the arm, I. The cylinder has now made another advance of half a division, which, together, makes a whole division the fabric has advanced. The purposes for which this is designed will now be described.

Figure 73 represents a top view of the whole apparatus of the _receiving_ station. The fabric, C′, C′, is marked in equal divisions across it, and in six equal divisions, in the directions of its length, thus marking it into squares. Each platinum ring, _a, a, a_, &c. (when the instrument is not in operation,) is in contact with the fabric at the _middle_ of the squares across the fabric. It will be observed, that the wires ̈1, ̈2, ̈3, ̈4, ̈5, ̈6 are in connection with the battery, Y, and the circuit complete, except at the arms of the needles. Suppose, for example, the arm of the needle, R′, of the wire, C′, is brought up against the stop of the wire, ̈5, at S; the circuit is then closed, and the current leaves the battery, and passes to the electro magnet, (causing the cylinder and fabric to move half a division,) then to the metallic cylinder, _d_; then through the fabric, _c′, c′_, resting upon the cylinder, (where it is in contact with the platinum ring, _a_, of the wire, ̈5,) then to the platinum ring; then to wire ̈5; then to the metallic stop, S; then to the arm of the needle, R′, along its axis to the mercury; then to the wire, I; then to wire, 8, and to the other pole of the battery, Y. Thus a current is passed through the prepared fabric, and a mark produced thereon, in the middle of its square. If the circuit is now broken, the cylinder moves another half division, which will bring the rings to the centre of the squares, ready for the next signal.

But one battery, Y, is used for all the six circuits, formed with the wire, 8; so that, when three of the circuits are closed at the same instant, as will be shown hereafter, the current passes through the three wires of their respective circuits, making each their appropriate mark upon the fabric.

We now proceed to describe the manner of operating with the two instruments, at their respective stations: and, first, we must here designate each needle by its own peculiar mark of reference. Let the two needles upon the wire, A′, be denoted by, A, S and A, T; those of the wire, B′, by B, S and B, T; and those of the wire, C′, by C, S and C, T. It will appear obvious, from the foregoing description, that but _one_ needle of each _wire_, A′, B′, C′, can be made to close its circuit at the same instant. However, _two_ needles, or _three_ needles of _different wires_, may close their circuits at the same instant, but no higher number than three. The various combinations of _one_ mark, _two_ marks, and _three_ marks, upon the same row of six cross divisions of the fabric, constitute the characters representing letters.

Figure 74 represents the _transmitting_ station, which may be supposed to be _London_, and figure 75, the _receiving_ station, which may be at _Birmingham_, with four wires extending from station to station, or three only, if the _ground_ be substituted for the wire, D, D″. The wires, D, A, B and C, are supposed to be united with D″, A′, B′ and C′, respectively. Now, if we depress the keys, in the following order, we shall, for each key, have the following deflections of the two needles, belonging to each key.

No. 1. The keys, H, 7, moves the arm, A, S, to the right, A, T, to the left. “ J, 7, “ A, S, “ left, A, T, “ right. “ K, 7, “ B, S, “ right, B, T, “ left. “ M, 7, “ B, S, “ left, B, T, “ right. “ O, 7, “ C, S, “ right, C, T, “ left. “ U, 7, “ C, S, “ left, C, T, “ right.

These are all the various deflections which it is possible to give the six needles. Those, however, which deflect to the right, not closing the circuit, produce no effect, and are of no account. We will, therefore, omit them, and simply give the table, thus:

No. 2. The keys, H, 7, move the arm A, T, to the left. No. 1. “ J, 7, “ A, S, “ “ 2. “ K, 7, “ B, T, “ “ 3. “ M, 7, “ B, S, “ “ 4. “ O, 7, “ C, T, “ “ 5. “ U, 7, “ C, S, “ “ 6.