There is an interesting, but brief, article about John Harrison's first reliable "sea chronometer" at solarnavigator
. Note Harrison's abandonment of a "large counterweight equals smoothness" approach for a solution centered on low mass, springwork, & constant tension. Quite elegant.
Harrison's H4 made possible Cook's Pacific exploration. Cook used a knock-off of Harrison's H4, reverse-engineered from his original and built to a price-point to make its use on all English
ships feasable (some 200 English
pounds, compared to 500 for a genuine Harrison). Harrison feared this scenario all along (were there even patents then?), and was reluctant to hand over his invention to the Royal Observatory (and into the hands of his chief competitor, Willaim Halley, of comet fame) to collect his 20,000-pound reward, the so-called "Longitude Prize," offered by the Crown for just such a device.
Interestingly, it was a version of this same basic timepiece that Lewis and Clark used on their overland expedition.
Well, that's the little bit I know. Any search engine
yields some very informative sites which detail the entire history
, if one is inclined to such arcana.
Thanks, Gord: you just gave me my afternoon's reading.