Jeremy Thacker was an 18th century writer and watchmaker, who coined the word chronometer

Chronometer

Chronometer may refer to:* Chronometer watch, a watch tested and certified to meet certain precision standards* Hydrochronometer, a water clock* Marine chronometer, a timekeeper used for celestial navigation...

 for precise clocks designed to find longitude

Longitude

Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 at sea. He himself created a marine chronometer

Marine chronometer

A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...

 positioned on gimbal

Gimbal

A gimbal is a pivoted support that allows the rotation of an object about a single axis. A set of two gimbals, one mounted on the other with pivot axes orthogonal, may be used to allow an object mounted on the innermost gimbal to remain immobile regardless of the motion of its support...

s and within a vacuum, but it was a failure. The idea of a vacuum for a marine clock had already been proposed by the Italian clockmaker Antonio Tempora in 1668. Slightly later, John Harrison

John Harrison

John Harrison was a self-educated English clockmaker. He invented the marine chronometer, a long-sought device in solving the problem of establishing the East-West position or longitude of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age...

would successfully build marine chronometers from 1730.

He wrote The Longitudes Examined in 1714.

Hoax?

According to an article published in the Times Literary Supplement in November 2008, "Thacker never existed and his proposal now emerges as a hoax".