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Email: Greetings from Greenwich


Date: Wednesday, 8 October 2003 09:14 PDT
Subject: Greetings from Greenwich

Captions for pictures and sounds:
1. Greenwich Royal Observatory at the Prime Meridian or Longitude 0 degrees
2. H4 sound clip

3 October 2003 – Day #13

Today, we visited the Royal Observatory in the town of Greenwich (as in “Greenwich Mean Time”) just outside of London. This is the location of the Prime Meridian or Longitude 0 degrees. The exhibit that caught my attention was the story of John Harrison. It told of his contribution to the science of navigation.

In 1707, England lost 4 ships and almost 2,000 men on the shallow water off the coast of England. In response, Parliament commissioned a panel of experts called the Board of Longitude. They offered 20,000 pounds (a lot of money 300 years ago) to the first inventor that could come up with an easy and accurate way of determining longitude at sea.

Before Harrison came around, determining Longitude was a challenge. First, the navigator would make three measurements with something called an astrolabe. He then would look up the result in a book called the Navigation Almanac. It worked, but it was time-consuming and subject to error. It also wasn’t available on cloudy days. Harrison determined the solution involved the development of an accurate clock.

Over the period of 30 years (1730-1759), John Harrison built a series of clocks. The early ones look like the works of a coo-coo clock. The last one (dubbed “H4”) looks like a large pocket watch. The last three clocks used two springs – the main spring and a smaller spring called the remontior. Basically, the main spring winds the smaller one. Because the museum has restored all four clocks, I was also able to grab a sound clip of the last one – the H4. You can actually hear the remontier if you listen carefully. It sounds like an alarm clock going off towards the end of the clip.

The first trial of the H4 was a 64 day round-trip voyage from London to Jamaica and back. The H4 only lost 5 seconds during this extended period. Surprisingly, Harrison had difficulty collecting the reward. The Board of Longitude wasn’t satisfied and added more conditions. Harrison appealed for many years. He was eventually awarded the prize at age 80.

God’s Blessings,