When planning this trip, we decided to take a cruise to get home. Then we decided to take the Chunnel train to get from Paris to England. Then we realized we could spend a day in London if we wished. I had read the book “Longitude” by Dava Sobel and decided I would like to see the first chronometers. And that’s what we did to end our trip.

(Straddling the Prime Meridian – one foot in the East, one in the West)

It’s a compelling story. Ships can find their latitude from the stars, but they can’t find their longitude. It’s a time of great competition for lucrative trade. England offers a large prize for a solution, with the value graduated to accuracy. John Harrison invents a clock rugged and accurate enough to keep good time on a ship. Sailors can determine their local time from the sun or the stars. If they know the time in London, they can calculate their longitude. Is Harrison’s chronometer accurate enough and rugged enough? Can it be manufactured, or is it an impossibly complicated device that can’t be duplicated?

Harrison built four chronometers over several decades, named H1 – H4. H1 was a huge clock. It replaced a pendulum with 4 large masses swinging back and forth on pivots. (You can see two of the masses in the picture.) It was good, but not quite accurate enough for the maximum prize. H2 was not as accurate as H1. Harrison discovered the heavy mass on long arms can be unstable. He came up with a circular balance (used in mechanical watches today). H3 was better, but still not quite accurate enough. His last chronometer, finished after decades of work, met all the requirements. It looked like a large watch.

We got to see the original of all four chronometers. H1, H2, and H3 were running. H4 is in working order, but is wound only on special occasions.

For our last vacation activity, we saw a ballet. This was an conventional ballet, with a story and traditional dance. There was no mooning. To get from our hotel to the Royal Opera House, we took our first Uber rides.

Our cruise home starts today. We meet a shuttle at the train station, just 1/3 mile from our hotel. Once on board, we will have internet access, but it is immensely expensive. I plan to check Email once a day, but lacking a serious emergency, I won’t post our adventures.