Editing Submarine communications cable (section)

===Construction, 19–20th century===
[[File:Bundesarchiv Bild 102-01035, New York, Verlegen von Unterseekabel.jpg|thumb|upright=1.15|right|Landing of an Italy-USA cable (4,704 nautical miles long), on [[Rockaway Beach, Queens]], New York, January 1925.]]
Transatlantic cables of the 19th century consisted of an outer layer of iron and later steel wire, wrapping India rubber, wrapping [[gutta-percha]], which surrounded a multi-stranded copper wire at the core. The portions closest to each shore landing had additional protective armour wires. Gutta-percha, a natural polymer similar to rubber, had nearly ideal properties for insulating submarine cables, with the exception of a rather high [[dielectric]] constant which made cable [[capacitance]] high. [[William Thomas Henley]] had developed a machine in 1837 for covering wires with silk or cotton thread that he developed into a wire wrapping capability for submarine cable with a factory in 1857 that became W.T. Henley's Telegraph Works Co., Ltd.<ref>{{cite web |title=Machine used for covering wires with silk and cotton, 1837 |publisher=The Science Museum Group |url=https://collection.sciencemuseumgroup.org.uk/objects/co44548 |access-date=24 January 2020}}</ref><ref name=Bright/> The [[India Rubber, Gutta Percha and Telegraph Works Company]], established by the Silver family and giving that [[Silvertown|name to a section of London]], furnished cores to Henley's as well as eventually making and laying finished cable.<ref name=Bright/> In 1870 [[William Hooper (chemist)|William Hooper]] established [[Hooper's Telegraph Works]] to manufacture his patented [[Vulcanization|vulcanized rubber]] core, at first to furnish other makers of finished cable, that began to compete with the gutta-percha cores. The company later expanded into complete cable manufacture and cable laying, including the building of the first cable ship specifically designed to lay transatlantic cables.<ref name=Bright>{{cite book |last=Bright |first=Charles |year=1898 |title=Submarine telegraphs: Their History, Construction, and Working |location=London |publisher=C. Lockwood and son |isbn= 9781108069489|lccn=08003683 |pages=125, 157–160, 337–339 |url=https://books.google.com/books?id=3DfeAgAAQBAJ&pg=PA157 |access-date=27 January 2020}}</ref><ref>{{cite web |last=Glover |first=Bill |title=History of the Atlantic Cable & Undersea Communications—CS Hooper/Silvertown |publisher=The Atlantic Cable |date=7 February 2019 |url=https://atlantic-cable.com/Cableships/Silvertown/index.htm |access-date=27 January 2020}}</ref><ref>{{cite web |last=Glover |first=Bill |title=History of the Atlantic Cable & Undersea Communications—British Submarine Cable Manufacturing Companies |publisher=The Atlantic Cable |date=22 December 2019 |url=https://atlantic-cable.com/CableCos/BritishMfrs/index.htm |access-date=27 January 2020}}</ref>

Gutta-percha and rubber were not replaced as a cable insulation until [[polyethylene]] was introduced in the 1930s. Even then, the material was only available to the military and the first submarine cable using it was not laid until 1945 during [[World War II]] across the [[English Channel]].<ref>Ash, Stewart, "The development of submarine cables", ch. 1 in, Burnett, Douglas R.; Beckman, Robert; Davenport, Tara M., ''Submarine Cables: The Handbook of Law and Policy'', Martinus Nijhoff Publishers, 2014 {{ISBN|9789004260320}}.</ref> In the 1920s, the American military experimented with rubber-insulated cables as an alternative to gutta-percha, since American interests controlled significant supplies of rubber but did not have easy access to gutta-percha manufacturers. The 1926 development by [[John T. Blake]] of deproteinized rubber improved the impermeability of cables to water.<ref>{{cite journal|last=Blake|first=J. T.|author2=Boggs, C. R.|title=The Absorption of Water by Rubber.|journal=Industrial & Engineering Chemistry |year=1926|volume=18|issue=3|pages=224–232|doi=10.1021/ie50195a002}}</ref>

Many early cables suffered from attack by sea life. The insulation could be eaten, for instance, by species of [[Teredo (bivalve)|''Teredo'']] (shipworm) and ''[[Xylophaga]]''. [[Hemp]] laid between the [[Steel wire armoured cable|steel wire armouring]] gave pests a route to eat their way in. Damaged armouring, which was not uncommon, also provided an entrance. Cases of sharks biting cables and attacks by [[sawfish]] have been recorded. In one case in 1873, a whale damaged the Persian Gulf Cable between [[Karachi]] and [[Gwadar]]. The whale was apparently attempting to use the cable to clean off [[barnacle]]s at a point where the cable descended over a steep drop. The unfortunate whale got its tail entangled in loops of cable and drowned. The cable repair ship ''Amber Witch'' was only able to winch up the cable with difficulty, weighed down as it was with the dead whale's body.<ref>[https://books.google.com/books?id=_hwAAAAAMAAJ&pg=PA311 "On Accidents to Submarine Cables"], ''Journal of the Society of Telegraph Engineers'', vol. 2, no. 5, pp. 311–313, 1873</ref>