Development of the distributed sea earth in transatlantic telegraphy

A manuscript, dated 1889, was discovered among the unpublished papers of James Graves, the first Superintendent at the Valentia Island transatlantic cable station. It was intended to appear in the Institution's Journal but its publication was blocked by his employer on the grounds of commercial confidentiality. In the paper, Graves hoped to reinforce his claim to the invention of the sea earth. This technique of using the outer metal sheathing of a cable as the earth return connection was to become standard practise in submarine telegraphy, although, as a direct result of commercial secrecy, its development is still uncertain. In the paper, the basis of Graves's claim is examined in the light of available documentary evidence. The unpublished paper and the correspondence which is generated are presented together. A brief resumé of the financial conditions which led to the suppression of the paper is presented.