John Mercer Brooke

John Mercer Brooke (December 18, 1826 – December 14, 1906) was an American sailor, engineer, scientist, and educator. He was instrumental in the creation of the Transatlantic Cable, and was a noted marine and military innovator.

John M. Brooke was born in Fort Brooke (modern-day Tampa), Florida. He was related to Congressman John Francis Mercer. His father was an army officer, General George Mercer Brooke, who died in San Antonio, Texas. He was a kinsman of General Dabney Herndon Maury as well as Virginia governor Robert Brooke.

Brooke graduated from one of the earliest classes of the United States Naval Academy and became a lieutenant in the United States Navy in 1855. He worked for many years with Commander Matthew Fontaine Maury at the United States Naval Observatory (USNO), charting the stars as well as assisting in taking soundings of the ocean's bottom to determine the shape of the sea floor. Many believed the sea floor was flat, but all previous soundings as deep as eleven miles (18 km) could not find the ocean bottom. Part of this was due to powerful undercurrents far below, rivers in the ocean traveling in various directions. In the struggles with soundings, which nobody had done anything of value at great depths, it was Maury's failure with a unique device he invented that gave Brooke an idea of taking deep sea soundings. Brooke perfected a "deep-sea sounding device" which was used afterwards by navies of the world until modern times and modern equipment replaced it. At Maury's direction, Brooke also added a "core-sampling device" for taking samples of the material of the sea floor.

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