John Mercer Brooke - Early Life and Career

Early Life and Career

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 the three men being related to Virginia governor Robert Brooke (Virginia).

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 in 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 bottom. Many believed the sea floor was flat but attempted soundings of the past in blue water (deep sea) as far as eleven miles (18 km) could not find the ocean bottom. Part of this was due to powerful under currents 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 after 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 always used afterwards by navies of the world until modern times and modern equipment replaced it. Working together on this project of many trials, Maury wanted to add a sea floor "core sampling device" which Brooke was able to invent.

The outcome was a cannonball with a hollow tube through the center of it—a tube coated with tallow on the inside and other experimental materials until the right coating was decided so as not to contaminate the samples of the sea floor brought up several miles. Studying this sea floor material with his microscope, Maury saw something that fascinated him. For further examination and a professional opinion (in Maury's own words)

. . . a part was sent for examination to Professor Bailey, Jacob Whitman Bailey, professor of chemistry, mineralogy and geology at the United States Military Academy — eminent microscopist. The latter, in November, 1853, thus responded: "I am greatly obliged to you for the deep soundings you sent me last week, and I have looked at them with great interest. They are exactly what I have wanted to get hold of. The bottom of the ocean at the depth of more than two miles (3 km) I hardly hoped ever to have a chance of examining; yet, thanks to Brooke’s contrivance, we have it clean and free from grease, so that it can at once be put under the microscope. I was greatly delighted to find that all these deep soundings are filled with microscopic shells; not a particle of sand or gravel exists in them. They are chiefly made up of perfect little calcareous shells Foraminifera and contain, also, a small number of siliceous shells Diatomacæ..."