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 in 1847 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 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. The outcome was a cannonball with a hollow tube through the center of it — a tube coated on the inside so as not to contaminate the samples. Studying this seafloor material with his microscope, Maury saw something that fascinated him. A sample was sent to
Jacob Whitman Bailey at the
United States Military Academy, who in November 1853 responded: 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
silicious shells (
Diatomaceae). It is not probable that these animals lived at the depths where these shells are found, but I rather think that they inhabit the waters near the surface; and when they die, their shells settle to the bottom. ==Telegraph==