John Harrison

1. John Harrison The inventorof marine chronometer

2. At about twenty years he built a clock without ever having practiced by a watchmaker, had not much experience as a mechanic and carpentiere.In later, in 1712 and in 1717 John Harrison built two wooden clocks. In 1722, Harrison built a clock with wooden gears for Sir Charles Pelham, who is still placed in the tower of his residence at Brocklesby Park, and still works perfectly. • John Harrison created four more watches (designed for high accuracy and precision, these chronometers) which, by calculating the exact longitude, changed the navigation of that time. For he is considered one of the largest contributors among those who made ​​it possible to resolve the long standing and important problem of measuring longitude.

3. The difficulty, however, was in producing a clock which could maintain accurate time on a lengthy, rough sea voyage with widely varying conditions of temperature, pressure and humidity. when longitude at sea is lost, it cannot be found again by any watch. By referring to the clock when it is noon locally (i.e. the Sun is at its highest in the sky where you are) you can read, almost directly from the clock face, how far around the world you are from the leaving where you had regulated the clock. • For instance, if the clock shows that it is midnight in London when it is noon locally, then you are half way round the world, (e.g. 180 degrees of longitude) from London.

4. So John Harrison invented the marine chronometer, a long-sought device in solving the problem of establishing the longitude position of a ship at sea, thus revolutionising and extending the possibility of safe in a travel in the deep sea. The problem was considered so intractable that the British Parliament offered a prize of £20,000 (comparable to £2.87 million in modern currency) for the solution.