THE COPYING ELECTRIC TELEGRAPH.
The specification of the invention by means of which a letter written in London may be copied verbatim et literatim in Liverpool, has been de- posited in the Enrolment Office, and discloses the means by which this electric correspondence is to be accomplished. Wonderful as it seems to have the power to produce a fac-simile of writing instantaneously at any distance, the mode of operation is extremely simple, and its general prin- ciple may be easily explained. The writing-materials consist of tin foil, varnish, and a quill pen. The letter thus written is applied to a cylinder; a metal style or point presses on the writing as the cylinder revolves; and the point being attached to a screw, it moves gradually along from one end of the cylinder to the other. The thread of the screw is sufficiently fine for the point to traverse six or seven times over each line of writing before it passes by the revolution of the cylinder to the next. The point is con- nected with one pole of a voltaic battery and the cylinder is connected with the other pole, so that the electric current may pass from the former to the latter: but as varnish is a non-conductor of electricity, the circuit is inter- rupted whenever the point presses on the varnish writing. The distant telegraphic instrument is an exact counterpart of the one that transmits; but, in place of the tin foil, paper moistened with a solution readily decom- posed by electricity is applied to the cylinder. Thus the electric current transmitted through the ordinary telegraphic wires is made to pass from the metal points to the cylinders of the two instruments, through the in- terposed moistened paper on one, and through the tin foil on the other. When the metal point of the transmitting instrument is pressing on the bare tin foil, the electric circuit is completed through the paper on the dis- tant cylinder, and by the decomposition of the solution a mark is made; when the point is pressing on the varnish, the circuit is interrupted and the marking ceases. In this manner, the point of the transmitting instrument, by passing several times over each line in different parts from the top to the bottom, produces an exact copy of the forms of the letters; the writing appearing pale-coloured on a dark blue ground, consisting of numerous lines made spirally round the cylinder.
It is essential to the correct working of the instruments that they should rotate exactly together; and this the inventor, Mr. Bakewell, has accom- plished by the regulating power of electro magnets brought into action at regular intervals by means of pendulums. It would be foreign to our pur- pose to enter into the details of this regulating arrangement further than to state, that by means of what is called a " guide line," the operator at the copying-station can tell with accuracy whether his instrument is moving faster or slower than the other; and he can thus regulate the pendulum accordingly. This guide line, we are informed, is so delicate an indication of the reciprocal movements, that a variation in the beat of the pendulums of less than the thousandth part of a second may be detected.
The rapidity with which communications may be transmitted by the copying-telegraph is one of its peculiar features. Cylinders six inches in diameter may, it is stated, be regulated to revolve thirty times in a minute and produce distinct copies of writing. The length of a line round such a cylinder would be about eighteen inches, within which space one hundred letters of the alphabet may be written in round hand. Assuming, there- fore, that thirty revolutions would be sufficient to copy four lines, the rate of copying would be four hundred letters per minute with a single wire; and with two wires and two points that number would be doubled.
The inventor states in his specification, that the copying-telegraph af- fords peculiar facilities for establishing a system of telegraphic transmis- sions and deliveries in all towns every half-hour throughout the day. If this plan could be arranged at a moderate cost, tin foil and varnish would have their compartments in all writing-desks; and we should become so habituated to rapid communications, that a letter by post would appear as tardy as we now consider a parcel sent by stage-waggon.
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