Maury’s researches in oceanography led to his connection with one of the most romantic and far-reaching scientific achievements of the century, the laying of the first Atlantic telegraph cable. Mention has already been made of the deep-sea soundings undertaken, under his direction, by American naval officers during the years 1849–1853. With the data furnished by these officers and by some others who were not engaged solely in sounding operations, Maury was enabled in the autumn of 1852 to construct an orographic map of the North Atlantic Ocean and to give a profile representing a vertical section of its bottom between America and Europe near the parallel of 39° north latitude. This showed the existence of what he called “the telegraphic plateau”. Up to this time no specimens of deep-sea ooze had been brought up from the bottom, and each sounding involved the loss of all the twine used as well as the cannon ball attached to it; and besides there was some uncertainty each time as to whether the bottom had really been reached. Fortunately, Lieutenant John Mercer Brooke, who was then at the Observatory, invented a simple but effective contrivance known as “Brooke’s deep-sea sounding apparatus”, which was well adapted to Maury’s needs. The instrument was used by Lieutenant Berryman in the _Dolphin_ during the year 1853 with great success, and the specimens which he obtained from the bottom were forwarded by Maury to Professor Bailey of West Point, for examination under the microscope. Upon examination the specimens were found not to contain a particle of sand or gravel mixed with them, but to be mites of sea-shells as perfect and unworn as when they were alive. This suggested to Maury the idea that there were no abrading forces at play upon the bottom of the deep sea, and that, if an electric cord were ever laid down upon the telegraphic plateau, there it would remain without anything to chafe or wear it except alone the tooth of time.