British and Irish Magnetic Telegraph Company

This system was problematic because of the limitations of insulation materials available at the time, but the Magnetic was constrained by the wayleaves owned by other companies on better routes.

They had a close connection with the Submarine Telegraph Company and for a while had a monopoly on underwater, and hence, international communication.

[7] In 1859, the Magnetic moved its headquarters from Liverpool to Threadneedle Street in London, in recognition that they were no longer a regional company.

[15] The system, invented by William Thomas Henley and George Foster in 1848,[16] was a needle telegraph and came in double-needle or single-needle versions.

They are so arranged that the right and left bells are struck according to whether a positive or negative pulse of current is received on the telegraph line.

[19] The Magnetic found a method of overcoming the problem of dispersion on long submarine telegraph cables.

[21] This system was developed theoretically by William Thomson and demonstrated to work by Fleeming Jenkin.

[23] Dispersion on the 1858 Atlantic cable had been so severe that it was almost unusable: it was destroyed by misguided attempts to solve the problem using high voltage.

[24] For the 1866 cable, it was planned to use the Magnetic's opposite polarity pulse method, but doubts were expressed over whether it would work over such a great distance.

Magnetic connected together various of their British underground cables to provide a total line length of over 2,000 miles (3,200 km) for proof of principle testing.

[27] The cable core was gutta-percha insulated copper wire made by the Gutta Percha Company.

Laying of the submarine cable was completed on 1 June 1852 by the City of Dublin Steam Packet Company's chartered paddle steamer Britannia of 1825, usually used as a cattle ship, and with assistance from the Admiralty with HMS Prospero.

[31][note 3] In July of the same year, the Electric Telegraph Company of Ireland tried using an insulated cable inside a hemp rope on the Portpatrick to Donaghadee route.

Previously, the test batteries had been lined wooden cases with liquid electrolyte (Daniell cells).

The new 'sand battery' comprised a moulded gutta-percha case filled with sand saturated with electrolyte, making it virtually unspillable.

Several suspect portions of insulation were removed and repaired, by opening up the iron wire armouring with Spanish windlasses.

[36] The cable was too taut as she sailed from Portpatrick, resulting in the test instruments being dragged into the sea.

[37] Magnetic were successful with a new cable in 1853 over the same route, with Newall this time using the chartered Newcastle collier William Hutt.

[41] The Magnetic's network was centred on northern England, Scotland, and Ireland, with its headquarters in Liverpool.

[46] However, a more pressing reason was that many railway companies had exclusive agreements with the Electric, which shut out the Magnetic.

[51] Gutta-percha is a natural rubber that is thermoplastic, so is good for continuous processes like cable making.

[52] On cooling, gutta-percha is hard, durable, and waterproof, making it suitable for underground (and later submarine) cables.

In the west of Ireland, by 1855 they had laid cables that stretched down the entire length of the island on the route Portrush–Sligo–Galway–Limerick–Tralee–Cape Clear.

This was due to the essential oils in the gutta-percha evaporating, leaving just a porous, woody residue.

This problem was the main driver for acquiring the unprofitable British Telegraph Company—so that the Magnetic inherited their overhead cable rights.

They were paid according to the speed with which they could send messages, up to the maximum of ten shillings per week when 10 wpm was achieved.