John Harrison will go down in history as the man who solved the problem of the Ascertaining of Longitude at sea. His sea clocks H1, H2 and H3 are important stages in the development of H4 and the Marine Chronometer. These clocks are on display in the new Time Galleries of the Royal Observatory Greenwich. On the 313th anniversary of his birth on March 24 2006, a memorial plaque was unveiled in the floor of Westminster Abbey by the Duke of Edinburgh, Admiral of the Fleet.
Amid pomp and ceremony, an address was given by Sir Arnold Wolfendale, the 14th Astronomer Royal, who had used his influence to see that the Man who Found Longitude was finally commemorated in the Abbey. The plaque lies adjacent to the stone marking the grave of Thomas Tompion.
The Harrison plaque is shown in this picture which shows a brass and stainless steel bimetallic longitude line (at 000 07'35"W) which runs through Harrison's name as it did through his life.
Harrison is buried in Hampstead and his gravestone is shown here. The inscription carved into the stone is shown under the picture.
IN MEMORY OF JOHN HARRISON Late of Red Lion Square London, inventor of the timekeeper 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 and repairing Clocks and Watches and made a few of the former chiefly of wood. At the age of 25 he employed his Whole Time on Chronometrical Improvements. He was the inventor of the gridiron pendulum and the method of preventing 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 the inventor of most (or all) of the improvements of Clocks and 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 Barbados, the Commissioners of Longitude certified that it had been 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 50 Years of close application to the above pursuit he departed this life on 24th day of March 1770 aged 83
Mrs ELIZABETH HARRISON, wife of the above MR JOHN HARRISON departed this life March 5 1777 aged 72.
Michael Adler July 2006