Steam, Steel and Electricity

by James W. Steele

Imagine now another stream entering the first at right angles to it, and that the rush stands in the center of both currents. It will then bend to the force of the second stream also, and the direction in which it will lean will be a compromise between the forces of the two. Lessen the flow of the current in one of the streams, and the rush will bend a little less before that current and swing around to the side from which it receives less pressure. Cut off either of the currents entirely, and it will bend in the direction of the other current only. In a word, if the quantity or strength of the current of both streams can be controlled at will, the rush can be made to swing in any direction between the two, and its tip will describe any figure desired, aided, of course, by its own disposition to stand upright when there is no pressure.

Let us imagine the rush to be a pen or pencil, and the two streams of water to be two currents of electricity having power to sway and move this pencil in proportion to their relative strength, as the streams did the rush. Imagine further that these two currents are varied and changed with reference to each other by the movements of a pen in a man's hand at another place. It is an essential part of the mechanism of the telautograph, and the movement is known among mechanicians as "compounding a point."

Gray, while using the principles involved in compounding a point, seems to have discarded the ways of transmitting magnetic impulses of varying strength commonly in use. His method he calls the "step-by-step" principle, and it is a striking example of what patience and ingenuity may accomplish in the management of what is reputedly the most elusive and difficult of the powers of nature. The machine was some six years in being brought into practical form, and was perfected only after a long series of experiments. In its operation it deals with infinitesimal measurements and quantities. The first attempts were on the "variable current" system, which was later discarded for the "step-by-step" plan mentioned.

In writing an ordinary lead pencil may be used. From the point of this two silk cords are extended diagonally, their directions being at right angles to each other, and the ends of these cords enter openings made for them in the cast iron case of the instrument on each side of the small desk on which the writing is done.

Inside the case each cord is wound on a small drum which is mounted on a vertical shaft. Now if the pencil-point is moved straight upward or downward it is manifest that both shafts will move alike. If the movement is oblique in any direction, one of the shafts will turn more than the other, and the degree of all these turnings of each shaft in reference to the other will be precisely governed by the direction in which the pencil-point is moved.

Now, suppose each shaft to carry a small, toothed wheel, and that upon these teeth a small arm rests. As the wheel turns this arm will move as a pawl does on a ratchet. Imagine that at each slight depression between the ratchet-teeth it breaks a contact and cuts off a current, and at each slight rise renews the contact and permits a current to pass. This current affects an electro-magnet--one for each shaft--at the receiving end, and each of these magnets, when the current is on, attracts an armature bearing a pawl, which, being lifted, allows the notched wheel, upon which it bears, to turn to the extent of one notch. The arrangement may be called an electric clutch, that may be arranged in many ways, and the detail of its action is unimportant in description, so that it be borne in mind that each time a notch is passed in turning the shaft by drawing upon or relaxing the cords attached to the pencil-point, an impulse of electricity is sent to an electro-magnet and armature which allows a corresponding wheel and its shaft to turn one notch, or as many notches, as are passed at the transmitting shaft. In moving the pencil one inch to one side, we will suppose it permits the shaft on which the cord is wound to turn forty notches. Then forty impulses of electricity have been sent over the wire, the clutch has been released forty times, and the shaft to which it is attached has turned precisely as much as the shaft has which was turned, or was allowed to turn, by the cord wound upon it and attached to the pencil.

It will be remembered that the arrangement is double. There are two shafts operated by the writer's pencil--one on each side of it. Two corresponding shafts occupy relative positions in respect to the automatic pen of the receiving instrument. There are two circuits, and two wires are at present necessary for the operation of the instrument. It remains to describe the manner of operating the automatic pen by connection with its two shafts which are turned by the step-by-step arrangement described, precisely as much and at the same time as those of the transmitting instrument are.

To each shaft of the receiving instrument is attached an aluminum pen-arm by means of cords, each arm being fixed, in regard to its shaft, as a bow drill is in regard to its drill. These arms meet in the center of the writing tablet, V-shaped, as the cords are with relation to the writer's pencil in the sending instrument. A small tube conveys ink from a reservoir along one of the pen-arms, and into a glass tube upright at the junction of the arms. This tube is the pen. Now, let us imagine the pencil of the writer pushed straight upward from the apex of the V-shaped figure the cords and pencil-point make on the writing desk. Then both the shafts at the points of the arms of the V will rotate equally. [[30]] The number of impulses sent from each of these shafts, by the means explained, will be equal. Each of the shafts of the receiving instrument will rotate alike, and each draw up its arm of the automatic pen precisely as though one took hold of the points of the two legs of the V, and drew them apart to right and left in a straight line. This moves the apex of the V, with its pen, in a straight line upward at the same time the writer at the sending instrument pushed his pencil upward. If this one movement, considered alone, is understood, all the rest follow by the same means. This is, as nearly as it may be described without the use of technical mechanical terms, the principle of the telautograph. It must be seen that all that is necessary to describe any movement of the sender's pencil upon the paper under the receiving pen is that the rotating upright shafts of the latter should move precisely as much, and at the same time, with those two which get their movement from the wound cords and attached pencil-points in the hand of the writer.