# 18th Century clock **URL:** \ **Category:** Factual Questions\ **Created:** [August 20, 2000, 3:38pm UTC](https://boards.straightdope.com/t/18th-century-clock/30054 "2000-08-20T15:38:54Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![galen](https://avatars.discourse-cdn.com/v4/letter/g/ecc23a/32.png) [@galen](https://boards.straightdope.com/u/galen)\ **Post date:** [August 20, 2000, 3:38pm UTC](https://boards.straightdope.com/t/18th-century-clock/30054/1 "2000-08-20T15:38:54Z")
Back in the 18th Century, self-taught clockmaker John Harrison solved the longtitude problem by constructing the first chronometer, H4. it was about 5 inches in diameter and weighed about three pounds. It had a jeweled movement and was accurate to five seconds in six and a half weeks at sea. The question I have is: How did he make such precision parts to tolerances which must have been better that 00001, maybe even 0.00001"? Wouldn’t he have needed precision lathes and milling machines? Think about how primitive machinery was in those days. Amazing. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [August 20, 2000, 3:41pm UTC](https://boards.straightdope.com/t/18th-century-clock/30054/2 "2000-08-20T15:41:02Z")
Part of it dealt with various types of metal expanding and contracting in different weather conditions out at sea. I have a vague recollection of something on the History Channel to that effect. You’d still need reliable percision, but the machining wouldn’t be as difficult. ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [August 20, 2000, 4:55pm UTC](https://boards.straightdope.com/t/18th-century-clock/30054/3 "2000-08-20T16:55:59Z")
Oh, well, duh, obviously he had help from aliens, who wanted us to hurry up and figure out the longitude thing so we could get to Antarctica and discover their hidden city under the ice. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 20, 2000, 7:38pm UTC](https://boards.straightdope.com/t/18th-century-clock/30054/4 "2000-08-20T19:38:33Z")
> [@](#): > > Wouldn’t he have needed precision lathes and milling machines? Think about how primitive machinery was in those days. Amazing. I’m thinking about how primitive machinery was then… Namely, not very. They did, in fact, have precision lathes and milling machines. Most of the advances we’ve made since have either been at scales far too small to matter for a clock (scanning tunneling microscope, for instance), or in making existing technology cheaper. If you’ve got support of the King and the military, you can afford to use the best possible tools for the job, which were quite adequate. ---
**Author:** ![yojimbo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yojimbo/32/232_2.png) [@yojimbo](https://boards.straightdope.com/u/yojimbo)\ **Post date:** [August 20, 2000, 8:48pm UTC](https://boards.straightdope.com/t/18th-century-clock/30054/6 "2000-08-20T20:48:47Z")
Harrison spent his whole life trying to perfect his clocks. He had very little support from the establishment which favored a method of observation of the skys over a clock. The BBC programme _Horizon_ did a show about this story based on the book “Longitude” . [http://www.bbc.co.uk/horizon/longitude.shtml](http://www.bbc.co.uk/horizon/longitude.shtml) ---
**Author:** ![funneefarmer](https://avatars.discourse-cdn.com/v4/letter/f/9fc348/32.png) [@funneefarmer](https://boards.straightdope.com/u/funneefarmer)\ **Post date:** [August 21, 2000, 12:11am UTC](https://boards.straightdope.com/t/18th-century-clock/30054/7 "2000-08-21T00:11:21Z")
I’m assuming you brought this up after watching that wonderful (4 hour long IIRC) movie ‘Longitude’ that A&E (I think it was them) first aired a month or two back. He did it by correcting it to no end, sometimes making the timepiece ever more complicated. It’s a good program but it’s best to tape it and watch it in stages considering its’ length.