1851 Great Exhibition: Official Catalogue: Class X.: Frederick Collier Bakewell
433. BAKEWELL, FRED. COLLIER, 6 Haverstock Terrace, Hampstead — Inventor and Patentee.
Patent copying electric telegraph, for transmitting facsimiles of the handwriting of correspondents, so that their signatures may be identified. Its objects are, authentication of communications, increased means of secrecy, rapidity of action, and economy, as it requires only a single wire.
The transmitting and the receiving instruments are counterparts of each other. Trains of wheels impelled by weights are employed to impart equal movements to cylinders on each instrument. Screws placed parallel to the cylinders, and rotating with them, serve to carry metal styles, which press' lightly on the cylinders, from end to end. The metal styles are insulated by being attached to ivory arms connected with brass nuts that traverse on the screws. One of the poles of the voltaic battery is connected with the cylinder of each instrument; the other pole of the battery is connected with the metal styles, so that the electric current may pass from the styles to the cylinders. The message to be transmitted is written on tin-foil with a pen dipped in sealing-wax varnish, and it is placed on the transmitting cylinder. When the instrument is set in motion, the metal style presses on the writing as the cylinder revolves; by which means the electric circuit is broken every time that the varnish interposes. Upon the cylinder of the receiving instrument, paper, moistened with an acidulated solution of prussiate of potass, is placed, and the metal style employed being a piece of steel wire, the electrochemical decomposition that occurs whenever the electric current passes, produces a line of Prussian blue on the paper. If there were no varnish-writing to interrupt the electric current, the revolution of the cylinder, and the gradual advance of the marking point by the screw, would draw a number of continuous blue lines spirally on the paper, but so close together as to appear parallel. The interruptions, however, caused by the interposition of the varnish-writing on the transmitting cylinder, break the electric circuit in those points, and cause a cessation of marking whilst the style is passing over each letter. As the style traverses several times oven each line of writing, the successions of interruptions, by corresponding with the forms of the letters, produce an exact copy of whatever is written or drawn on the tin-foil message; the writing appearing of a pale colour on a ground of closely- drawn blue lines.
The regulation of the separate instruments, so that they may rotate exactly together, is effected by an electro-magnet or electro-magnets brought into action by local voltaic batteries. When a single wire only is used, contact with the local voltaic batteries of the electromagnets is made and broken by pendulums, each instrument having a pendulum in connection with it; by which means the electro-magnets act at regular and quickly- succeeding intervals. Levers, attached to the armatures of the magnets, press against eccentric wheels fixed upon one of the arbors of each instrument, and retard the motion of the mechanism so long as they bear against them. The instruments are thus regulated at every beat of the pendulums by having their speed retarded. The degree of retardation depends on the amount of weight applied to impel the cylinders; care being taken that the ungoverned speed should be always somewhat greater than it is required to be, to allow for the regulating action. When there are two wires employed, the regulation of the instruments may be effected without pendulums by bringing the regulating magnet of one instrument into action by a make-and-break contact- wheel fixed on to a corresponding arbor of the other instrument. To assist in adjusting two distant instruments, a "guide line" is employed, which consists merely of a strip of paper placed perpendicularly to the lines of writing on the transmitting instrument. When the corresponding instruments are set in motion, the interruptions of the electric current by the guide line indicate exactly, on the paper of the receiving instrument, how much faster or slower the transmitting instrument is moving; and by adding or taking off weights at the receiving instrument, its average speed may be adjusted to that of the transmitting one, so that the marks or gaps in each successive line drawn on the paper may fall under each other. When the instruments are regulated by pendulums, the guide line serves to show whether they are beating together; and thus affords the means of adjusting them with great accuracy. The following cut shows the telegraph.
a, the cylinder of one of the instruments; h, the metal style, connected by the wire g, with one pole of the voltaic battery; o, the ivory arm to which the metal style is attached, and which insulates the style from the screw; r, the screw on which the style traverses as the cylinder revolves; d, cog wheels to turn the screw; e, a fan to regulate the speed of the instrument; f, the impelling weight; h, the wire connected with the distant instrument.
The copying electric telegraph is not yet in operation; but its practicability has been successfully tested by the transmission of messages to and from different stations of the Electric Telegraph Company, with the experimental instruments exhibited.