John Harrison (1693-1776), British inventor. With so many ships being lost due to navigational errors, the British Government in 1713 put up a prize of 20,000 pounds for the first person to accurately calculate longitude aboard a ship. Harrison decided to build a chronometer that could work on a moving ship and allow measurement of time differences, and hence longitude, around the world. He introduced a number of innovations, including bimetallic strips to allow for temperature differences, meaning that his last chronometer, no bigger than a large watch, was more accurate at sea than any other clock was on land. Published in a book in 1849.