Maury says, in his Sailing Directions:—"As yet no specimens of the bottom in deep water had been brought up. The line was too small and the lead too heavy to be hauled in. In this state of the case, passed Midshipman John Mercer Brooke, then stationed at the Observatory, proposed a contrivance by which the plummet or shot on striking the bottom, would detach itself and send up the line with a specimen of the bottom. This beautiful invention is called 'Brooke's deep-sea sounding apparatus.'"
Early in 1854, Maury wrote the following letter to the Secretary of the Navy on the subject of these deep sea soundings, with special reference to the project of laying a submarine telegraphic cable across the Atlantic:—
| Sir, | National Observatory, Feb. 22nd, 1854. |
The U. S. brig 'Dolphin,' lieutenant commanding O. H. Berryman, was employed last summer upon special services connected with this office. . . . He was directed also to carry along a line of deep sea soundings from the shores of Newfoundland to those of Ireland. The result is highly interesting upon the question of a submarine telegraph across the Atlantic, and I therefore beg leave to make it the subject of a special report.
This line of deep sea sounding seems to be decisive of the question as to the practicability of a submarine telegraph between the two continents in so far as the bottom of deep sea is concerned. From Newfoundland to Ireland the distance between the nearest points is about 1,600 miles, and the bottom of the sea between the two places is a plateau which seems to have been placed there especially for the purpose of holding the wires of the submarine telegraph, and of keeping them out of harm's way. It is neither too deep nor too shallow; yet, it is so deep that, the wires but once landed will remain forever beyond the reach of the anchors of vessels, icebergs, and drifts of any kind, and so shallow that they may be readily lodged upon the bottom. . . .
