Plaque Wording: In Memory Of MR. JOHN HARRISON, late of Red-Lion Square, London.
Inventor of the TIME-KEEPER for ascertaining the LONGITUDE at Sea. He was born at Foulby, in the County of York, and was the Son of a Builder at that Place, who brought him up to the same Profession. Before he attained the Age of 21, He without any Instruction, employed himself in cleaning & repairing Clocks & Watches & made a few of the former, chiefly of Wood. At the Age of 25 He employed his Whole Time in Chronometrical Improvements. He was the Inventor of the Gridiron Pendulum and the Method of preventing the Effect of Heat and Cold upon Time keepers by Two Bars of different Metals fixed together. He introduced the Secondary Spring to keep them going while winding up; and was the Inventor of most (or all) of the Improvements in Clocks & Watches during his Time.
In the Year 1735, his first Time keeper was sent to Lisbon, and in 1764 his then much Improved fourth Time keeper having been sent to Barbadoes, the Commissioners of Longitude certified that it had determined the Longitude within one Third of Half a Degree of a great Circle, having erred not more than 40 Seconds in Time.
After near fifty years close Application to the above Pursuits, he departed this Life on the 24th Day of March 1776, Aged 83.