Longitude, Part II

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As mentioned in the last post about longitude, while one group of people were charting stars and hoping to use tables to help out with the determination, others were working the time angle (so to speak).  What those folk needed was a good clock, one that would keep time even if it got bounced around a bit, like on a ship, because people on the ocean were in especial need of figuring out where they were.

So people worked on it.  And worked on it.  And then worked some more.  Prizes were offered, and went unclaimed.  Then a famous shipwreck in 1707 (involving HMS Association, HMS Eagle, HMS Romney, and HM Fireship Firebrand) took the life of 1500 sailors, apparently because they miscalculated longitude, and Britain was all, “Enough of this!” and 1714 formed the Commission for the Discovery of the Longitude at Sea, which was a mouthful to say so everyone just called it the Board of Longitude.  They offered a prize for calculating longitude and didn’t even insist that the longitude be exact, just within 60 nautical miles for a prize, or within 40 or 30 nautical miles for better prizes.

Uh, nautical miles?  One nautical mile is 1 minute of an arc of latitude, so 60 nautical miles would be 1º and 30 nautical miles would be ½°.  Of latitude.  It translates to just over 1 regular mile.

Where were we?  Oh yes, in England.  Which is also where John Harrison was.   He was born in 1693, and made clocks out of wood with his younger brother.   One of his great achievements was to design the parts so that they had almost no friction, and therefore didn’t need any oil.  This was a big improvement because 18th century oil quite frankly stunk as far as clocks were concerned.

Harrison decided to make a clock good enough to win the prize.  His first clock, conveniently called H1, was made when he was about 40 years old.  And it worked well during the Official Testing on board a couple ships (because you didn’t think a prize would be awarded without checking how the clock did at sea, did you?) but Harrison wasn’t completely happy with it so instead of the full prize he asked for money to make a second version.  He worked on the next clock (H2) from 1737 to 1740, then decided that was all wrong and began work on H3.  This took 19 years — our man Harrison was nothing if not thorough.  But sadly, H3 wasn’t good enough to win the prize, and meanwhile he began working on — hold your breath everyone — H4.

Incidentally, one of the neat things about Harrison’s clocks is that they weren’t just different versions of the same thing.  It’s not like he said, “Hey, I have a new edition out — no, really, the fact that I changed one tiny thing makes it completely different.”  His clocks really were different, and H4 was down to being a pocket watch, which is mighty convenient for being on board a ship.

Here the story gets complicated.  H4 kept really good time, losing less than a second a day, but the Board of Longitude was all, “Well, maybe, maybe not” and Harrison had to make more copies, and blah blah and yadda yadda yadda and the end result was that he also made a new clock H5, plus his buddy Larcum Kendall made a copy (called K1), but the Board was still, “Umm, well” and people  — by people I mean King George III — got all upset and finally in 1773 the Board said, “OK, you win.”

harrisons_chronometer_h5

Interestingly, this recent article from New Scientist says that when they opened up H1 to re-fix something (it had been in disrepair and was fixed more than 40 years ago), the way the parts were manufactured suggested that he had some help with some of the chains and whatnot inside.  It’s a pretty interesting article, and the comments are fun to read (mostly saying things like “Of course he had a bit of help!  He didn’t smelt his own metal, now did he?”) but the best part is the gallery of pictures here.

The photo of H5 is published on wikimedia by racklever under GNU-FDL.  A lot of the information about Harrison is from this site.

2 Responses to “Longitude, Part II”

  1. Latitude « 360 Says:

    […] up:  Longitude (Part I and Part II). Possibly related posts: (automatically generated)A Star of Another […]

  2. Recommended readings 6/5/09 « Division by Zero Says:

    […] longitude, and more longitude ~ I have fond memories of doing celestial […]

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