In 1714, the British Parliament offered a cash reward to anyone who could invent a clock accurate enough for use in navigation at sea. Thousands of sailors died because they were unable to find their exact position, because the exact time was needed to find longitude, and pendulum clocks would not work at sea. For every minute lost by a clock, it meant that there would be a navigational error of 15 miles, and sailors died because they were lost or smashed against rocks because they were unable to figure out their exact position. Then, in 1761, after 4 attempts, John Harrison finally succeeded at inventing a small clock accurate enough to use for navigation at sea. This tiny pocket watch lost only 5 seconds in 6 and ½ weeks.