For sale: Life and times of `Longitude' clockmaker

EVER SINCE Dava Sobel wrote her best-selling novel Longitude, readers have been fascinated by the struggles of the Yorkshire horologist John Harrison to convince the Board of Longitude he had solved the greatest scientific problem of his age.

His efforts to develop a clock that would keep precise time at sea, something no clock had ever been able to do on land, are well documented from the minutes of meetings between Harrison and the board. But the clockmaker's own account of what happened has never been heard. Now his diary is to be auctioned by Sotheby's on 17 December and is expected to fetch upwards of pounds 150,000.

Peter Beal, of Sotheby's, said the diary unquestionably belonged to Harrison: "This is his story in his own words, which has never been published before. It is a formal record of how he deserved the prize and of everything he went through."

The quest for a solution to the problems of longitude occupied scientists for almost two centuries. Lacking the ability to measure longitude meant that sailors were literally lost at sea as soon as they lost sight of land. In 1714, Parliament offered pounds 20,000 to anyone who could solve the problem and the race, which attracted scientists across Europe, was on.

Harrison invented a clock that would keep the precise time at sea so that sailors could compare the time in Greenwich with the position of the midday sun and thus plot their position.

But his efforts to claim the prize were frustrated at every turn and he made several enemies on the board. The journal, penned by Harrison's lawyer, Walter Williams, and annotated by his son William, (Harrison could not write) tells of the often acrimonious meetings.

After one such meeting, the diary recorded: "The Doctor [James Bradley, Astronomer Royal] seemed very much out of temper and in the greatest passion told Mr Harrison that if it had not been for him and his plaguey Watch Mr [Tobias] Mayer and he should have shared the Ten thousand pounds before now ..."

After one trial of his final timepiece, H4, which lost less than two minutes in five months at sea, Harrison should have been able to claim his prize. But the board continued to question him. He stormed out of one meeting declaring "so long as he had a drop of English blood in his Body he would not comply with their Resolutions without they would explain them".

Harrison was eventually granted the prizemoney in instalments but was never acknowledged as the winner. His diary remained in the family until 1900. It surfaced nearly 70 years later and has since been in private ownership.