How was Time Measured at Sea?

Today, it is easy to glance at your watch to plan your day. Time is no longer a chore requiring sky gazing and complicated calculations. However, it took a long time for inventions such as the pendulum to lead to the making of your wristwatch, and more time still before time was measured at the sea. Due to swaying on the sea, water clocks and pendulums were inaccurate on ships. Thus, other efforts were made:

1. The Hour Glass: This ancient invention was once considered the most reliable measurement of time and was also used to help measure a ship’s speed. A wooden panel attached to rope, wound on a reel, would be tossed overboard a moving ship. The knots on the unwinding rope were counted against a sand clock.
2. The Celatone: Galileo Galilei invented a helmet with a telescope attached to it. This would allow sailors to observe the planet Jupiter’s moon move behind the planet. Since its movement is so regular, he was convinced watching it would allow mariners to calculate time. Unfortunately, keeping sight of the planet onboard a rolling deck proved difficult.
3. Powder of Sympathy: This was made by pounding copper sulphate and then leaving it in the sun. Strangely, it was believed to heal wounds by immersing a blood stained cloth of the wounded person in a bowl of water mixed with the powder. Sir Kenelm Digby suggested this powder could help sailors measure time. He proposed to send a wounded dog on a vessel, while he himself would stay ashore. At noon time, he could apply powder on blood stained bandage causing the dog to howl and thus announce to the sailors the noon time. The idea sank.