So what was Harrison's big breakthrough wrt the chronometer?

Since I’m asking another GQ on longitude I thought I’d try find out something that’s been bothering me for a couple of years since I read Sobel’s “Longitude”. She writes very interestingly about the 18th century quest to find an accurate way of telling the time at sea, which was necessary in order to determine the ship’s east - west position. However she goes into disappointingly little detail on how John Harrison finally solved the problem when he made “H4”, the chronometer which is really a very accurate watch. Until then he had been labouring with clock technology, as watches were regarded as too innaccurate. Sobel does not explain how Harrison managed to suddenly and so dramatically improve watch technology, other than mentioning something about jewels used to combat friction. I’m guessing that the problem was something to do with the watchspring, which is used instead of a pendulum to regulate the seconds, but what did Harrison actually do to improve the watchspring, or whatever?

It wasn’t “suddenly”. In the documentary I saw on him it apparently took him over 40 years of experimentation to get the design and several false starts. Near as I remember the innovation was making a timepiece whose movement was unaffected by motion and changes in temperatures.
You can read a little more here.

From this site:


Hope this helps!


It was actually more sudden than you make out. Much of the 40 years of experiment was with clocks; his breakthrough came when he decided to go for a completely different type of timepiece. You only need to look at how different H1, H2 and H3 are from H4 to realise this. At first glance that website also does not appear to answer the point of my question; what did Harrison do to so dramatically improve watch technology?

Thanks, godzillatemple, that’s more what I’m looking for.

My pleasure. The author of the information I quoted is none other than Jonathan Betts, the Curator of Horology at the National Maritime Museum, Greenwich.

Let me know, BTW, if you need assistance with any of the terminology in that article.


Come visit my Pocket Watch Collection!

IIRC, he used metals. Wood was in common use for parts back then (for bearings even!), making them much larger, but he skipped wood and stuck to metals. This also allowed him to use oil instead of the “Frictionless wheels” Which, over the space of an atlantic crossing, actually produced enough friction to throw even the chronometers made by the finest craftsmen end up off by not only minutes, but hours, and minutes=miles. IIRC, he was anal enough to produce gears with a higher number of teeth, with ended up making everything a bit more exact. I think that it really was just a bunch of little things that he did that made it such a breakthrough. Some of the best inventors don’t come up with new things, they just take existing things and combine them in ways no-one has ever thought of.