As early as 1848 Maury had concluded, from his investigations of the winds and currents, that a broad and level plateau—the "telegraphic plateau"—existed at the bottom of the ocean between Newfoundland and Ireland. His view was confirmed by the deep-sea soundings that were taken at his instance between 1849 and 1853; and early in 1854 he reported to the Secretary of the Navy that, so far as the bottom of the deep sea was concerned, a submarine telegraph between Newfoundland and Ireland was practicable. A plateau seemed to have been placed there especially for holding the wires and keeping them out of harm's way. His views respecting the manner of constructing cables were confirmed, both in the behavior of the first cable, constructed differently from them, which failed, and the others, made more in harmony with them, which were successful. At the dinner given in celebration of the arrival of the first message across the Atlantic, Mr. Cyrus W. Field said, referring to the enterprise, "Maury furnished the brains, England gave the money, and I did the work."
A painful surprise came to Lieutenant Maury when the Naval Retiring Board, under the act of Congress of February 28, 1855, placed him on the retired list on leave-of-absence pay, but without detaching him from the Naval Observatory. He regarded the act as an indignity. He wrote to three of the Secretaries of the Navy under whom he had served for expressions concerning his efficiency, particularly inquiring why he had been kept at the observatory instead of being sent to sea. Ex-Secretary Graham answered: "I considered your services at the National Observatory of far more importance and value to the country and the navy than any that could be rendered by an officer of your grade at sea in the time of peace. Indeed, I doubt whether the triumphs of navigation and of the knowledge of the sea achieved under your superintendence of the observatory will not contribute as much to an effective naval service and to the national fame as the brilliant trophies of our arms." Mr. John P. Kennedy wrote, "From my knowledge of the nature of your scientific pursuits, their usefulness to the country, and your devotion to them, I can say that nothing but such an emergency as left me no alternative, would have induced me to withdraw you from your labors at the observatory by an order to go to sea." Mr. William Ballard Preston wrote to similar effect. In the following winter Maury was, by special act of Congress, reinstated and promoted to the rank of commander, with back pay from the date of his retirement.
Other schemes discussed by Lieutenant Maury in general or special papers, included the location of lighthouses on the Florida