History of the Atlantic Cable & Submarine Telegraphy—Velocity Experiments on Telegraph Cables

	History of the Atlantic Cable & Undersea Communications from the first submarine cable of 1850 to the worldwide fiber optic network
Velocity Experiments on the Mediterranean Electric Telegraph Company’s Cable Illustrated London News, 6 October 1855

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Mediterranean Electric Telegraph
Apparatus for the Automatic Recording of the Velocity Experiments

a Metal drum driven by a weight and train of wheels, for the purpose of drawing the chemically-prepared paper. This drum revolves in a trough of water.

b Roll of chemically-prepared paper, enclosed in a circular box; lid removed to display the paper.

c Arm carrying four steel styles, or tracers, of Geneva mainspring, carefully insulated from each other, which press upon the paper. The styles are parallel to each other, and the points are placed in a line directly at right angles to, or across, the slip of paper.

d Pressing or biting roller, to prevent the paper slipping on the drum.

e Trough of water.

f Clock movement driving the pendulum.

g seconds pendulum.

h A “Bain’s break-piece and bar,” somewhat modified and arranged so as to change the contact, at every beat of the pendulum, from No. 1 to No. 4 style, or vice versa.

i Receiving apparatus, or relay, in connection with the home circuit: this makes connection between the printing battery and style No. 2.

j Similar apparatus in connection with the long circuit current, and placed in the middle junction of the wires. This makes connection between printing battery and style No. 3.

k Local printing battery, which may be of any required number of cells. From the zinc terminal (z) a wire goes direct to the frame-work of the metal drum. From the other end of the battery three wires proceed — one to each relay, and one to the “constant” end of the break-piece (h); while, from the alternating end of the break-piece two wires proceed, carrying the current to No. 1 and No. 4 styles, alternating at every beat of the pendulum.

Whitehouse's description of the experiment:

A slip of moistened chemical paper is kept moving by a train of wheels at a moderate speed over a metallic drum. Pressing upon the upper surface of this paper on the drum and parallel to each other, are four steel springs or styles, insulated from the drum and in connexion each with its proper wire. Two of these styles, the first and the fourth in order, record the beats of a seconds pendulum upon each side of the slip of paper alternately, the seconds having in this instance been subdivided into fractional parts—“twelfths” by a very simple revolving arrangement.

Two separate magneto-electric currents, “twin-currents,” as they may be called, synchronous in their origin, but differing in their destinations, and wholly distinct in their metallic circuits, are sent by one and the same movement of a handle. One travels about twenty feet, is received upon a “relay,” or instrument which instantly gives a contact for a local printing battery, and records itself upon No. 2 style; this serves to note the instant when the current going the long circuit began its journey.

The other current, and of course a much stronger one, is sent through 900 miles of wire, and is received upon a similar “relay” placed in the middle junction of these wires, and therefore, at the greatest practicable distance from the source of the current. This current actuating the “relay” when it arrives, gives a contact for the printing battery in the same way as the other, and records itself upon No. 3 style after an appreciable interval of time. For 900 miles this interval of time is very nearly 3-12ths of a second, as will be seen by reference to the slip.

Facsimile of Telegraphic Autograph

Last revised: 23 April, 2010

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