Clock History Part 4

         Horology evolved as humanity itself evolved, as the need to sail and navigate became a stronger means of trade and exploration. The ability to tell time was vital, as you could not tell how far along on navigation charts, or any map without knowing your speed and time. Speed was easy to tell. Using a knotted rope,  a weight ,and a hour glass  you could figure out how fast you were going at sea (this was called a "chip log" and very quickly became a standard instrument aboard ships). Throwing the weight overboard and starting the hourglass, the amount of knots that were unraveled from the weight would tell how fast the ship was going. This is where the navel speed "knots" came from.
          This was half of the equation for navigation. to accurately get a bearing on where you were at sea, you needed to know the time. The standard pendulum clock would not work, as the constant motion of the ship would jar and move the clock, making it inaccurate. Ship clocks had to be accurate enough that they couldn't gain or lose 10 seconds a day. In 1714, the British government offered a large prize for anyone that could solve this dilemma. The prize (which in modern day terms was about 20,000 pounds) was claimed by John Harrison in 1761. Harrison spent his life improving the device he made, which could accurately keep time at sea by a margin of plus or minus 5 seconds over the course of 10 weeks. The device, known as a Marine chronometer had weighted balances to account for the rocking of the ship, as well as the use of bearings to reduce friction.