John Harrison Longitude Problem

For every 15 degrees that one travels eastward, the local time moves one hour ahead. Similarly, traveling West, the local time moves back one hour for every 15° of longitude. Therefore, if we know the local times at two points on Earth, we can use the difference between them to calculate how far apart those places are in longitude, east or west.

This idea was very important to sailors and navigators in the 17th century. They could measure the local time, wherever they were, by observing the Sun, but navigation required that they also know the time at some reference point, e.g. Greenwich , in order to calculate their longitude. Although accurate pendulum clocks existed in the 17th century, the motions of a ship and changes in humidity and temperature
John Harrison took on the scientific and academic establishment of his time and won the longitude prize through extraordinary mechanical insight, talent and determination.

Harrison was born in Foulby, near Wakefield , in Yorkshire in 1693 but his family moved to Barrow, in Lincolnshire , when he was quite young. His father was a carpenter, and John followed in the family trade. He built his first long case clock in 1713 at the age of 20. The mechanism was made entirely from wood, which was not a curious choice of material for a joiner. Three of Harrison's early wooden clocks have survived; the first (1713) is in London , at the Worshipful Company of Clockmakers' Collection in Guildhall; the second (1715) is in the Science Museum; the third (1717) is at Nostell Priory in Yorkshire . During the mid-1720s, John and his brother, James, designed a series of remarkable precision long case clocks to see how far they could push the capabilities of the design. By inventing a pendulum rod made of alternate wires of brass and steel, Harrison eliminated the problem of the pendulum's effective length increasing in warmer weather and slowing the clock. As a result, Harrison's regulators from this period achieved an accuracy of one second in a month - a performance far exceeding the best London clocks of the
Harrison worked on three portable clocks, H1, H2 and H3, filled with features of his great ingenuity. But he eventually won the coveted prize with H4. The H4 is completely different from the other three timekeepers. Just 13 cm in diameter and weighing 1.45 kg, it looks like a very large pocket watch. Harrison's son,William, set sail for the West Indies with H4 aboard the ship Deptford on 18 November, 1761. They arrived in Jamaica on 19 January, 1762, where the watch was found to be only 5.1 seconds slow! It was a remarkable achievement, but it would be some time before the Board of Longitude was sufficiently satisfied to award Harrison the