Almost as soon as the electric telegraph came into widespread use, people began thinking of laying telegraph cables underwater for intercontinental message transmission. Successful installation of submarine cables was not possible at first because insulating materials were inadequate. Early lines run by Samuel Morse in New York Harbor in 1842 and by Ezra Cornell across the Hudson River in 1845, for example, both failed. Then the insulating properties of Malaysian gutta-percha were discovered, and machines for coating telegraph cables with gutta-percha were invented by Werner von Siemens (1847) and Thomas Hancock (1848).

The English brothers John and Jacob Brett laid the first submarine telegraph cable between England and France in 1850, but it was not strong enough, and broke. In 1851 the Bretts laid a second cross-Channel cable. The success of this cable led to the laying of many more underwater lines which, inevitably, led to thoughts of a transatlantic...