Voyage of Discovery — Knowing their location?

[andy52]

Most of the watches of that time frame were verge fusee's which are chain driven and very delicate, It amazes me that this one has survived for almost 225 years and is still in working condition.

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[tenngun]

My understanding was the difference between a regular clock & a chronograph was that the chronograph DIDN"T lose or gain time & was accurate to an extreme degree. Wasn't it this precise time keeping that allowed navigators to accurately fix their longitude by noting the difference between local time & GMT? I was taught that Harrison's great hurdle was developing a clock that didn't lose or gain time on broad a swaying & pitching ship. I have never heard of a chronograph that has a known built in error, but I haven't heard of a lot of things & I'm sure that mechanical chronographs weren't as perfect as today's atomic clocks. Can you elaborate?

His clocks did lose time just not very much but were very expensive. As it was ships normally had from three to five on board and checking time with a passing ship was a normal part of ships routine at sea.
A fleet or convoy kept better time then a lone ship.

 

[tenngun]

Ships usually had several so they at least could use an average.
A ship also usually got a fix on the sun at first day light....As I recall exactly one minute after the sun cleared the horizon, which would be challenging on land as well as at high noon.

I understand ships got a fix at noon. Sunrise comes at a different time every day, and different times along the same longitude depending on how far north or south one was.
Noon is always 24 hours apart on a longitude line no matter what time of year it is. So you get your postion from local noon compared to noon back home or the prime maridian

 

[tenngun]

Most of the timepieces of the time were not highly accurate and very expensive.
Most common people really couldn't afford one. I have a 1797 English-made watch that's accurate to about 5 minutes in a 24 hour period which was pretty good for the time. View attachment 110198View attachment 110199View attachment 110200View attachment 110201

My bad here as I’m tossing in something I can’t reference
I read a book about Waterloo, I do not recall the name of the book or the author, but recall something he talked about in the research he did writing the book. And that was the multiple disagreements in time. Cannon was shooting and regiments attacking before the order was given depending on whose account one was reading.
Not only did the Allies time not agree with French but inside the armies times were ‘wildly’ different
The author pointed out watches lost time, even if they were wound twice a day, some officers set time to London or Paris time, some to their own homes back in Britain or Germany or France, some to local time and some to local time a few days before. So there could be any random number between zero and thirty minutes difference between watches on the field that day.
For some one telling position across the L&C route an hour is five to six hundred miles. A loss of just a few minutes is off by forty to fifty miles. About a 1/6 of a mile per second off.

 

[mhb]

A chronometer is known to lose or gain precisely X amount of seconds or minutes per 24 hours. By knowing this amount time can thus be corrected. The was a great series on PBS about Harrison's development of the chronometer finally adopted by the Royal Navy. I think it was called "Longitude".

When initially tested and regulated, a log was initiated for the chronometer, and the average gain or loss was recorded - this could only be done when the instrument was in the hands of the maker or other specialist with access to an observatory able to provide the correct sidereal time. The rate varied slightly even under ideal conditions (the chronometer was, after all, a mechanical device, subject to the influences of the environment) - knowing the average rate, the subsequent user of the instrument could use it as a basis for his calculations by applying the established average rate change each time a position reading was taken. But, because the rate did change over time and with differing conditions, the true error at any given time could not be known, so, even with the best of chronometers and most accurate observations (and calculations), the errors became cumulative, though some could cancel out, at least partially. The longer the chronometer was used without check and re-regulation against an accurate sidereal time determination, the further out of truth it was likely to be.
The book 'Longitude' is an excellent work, and does thoroughly explain the development of precise means of navigation by 'solving the longitude'. The Board of Navigation offered a prize of 10,000 pounds, an enormous sum at the time, and Harrison was the first to build a chronometer able to meet the Board's test requirements, though he never received the full amount due to political wrangling. A competing means was OLD (Observed Lunar Distance), as mentioned earlier in this thread, but accurate observations at sea were so difficult and unreliable, and the calculations so complex, that it was never a serious competitor to the accuracy of time data provided by the fully developed chronometer.

mhb - MIke

 

[tenngun]

Later:

Lewis is known to have purchased an Arnold chronometer in Philadelphia - for $250, plus 75 cents for the winding key (!).

mhb - MIke

A few years later The Hawken brothers sold their rifles for about $25, a NWG went for about $12.50, Leman would get about $14 for his rifles.
$250 (and change) represented about six months wages for a skilled craftsman. An army private made about $36 A YEAR

 

[Crow-Feather]

They always knew where they were. They were east of the pacific and somewhere in the middle the United States.

 

[Carney Pace]

Get a set of the Lewis and Clark Journals, 8 volumes. They are full of information and observations.

 

[Ben Meyer]

The thing that always amazed me is Clark's map . He wasn't a professional cartographer, he was a military man. Yet, it's a darn good map! Of a VAST swath of land, traversed on foot, by boat, on horseback. I cant even imagine being able to do that.

 

[kipcarter]

My bad here as I’m tossing in something I can’t reference
I read a book about Waterloo, I do not recall the name of the book or the author, but recall something he talked about in the research he did writing the book. And that was the multiple disagreements in time. Cannon was shooting and regiments attacking before the order was given depending on whose account one was reading.
Not only did the Allies time not agree with French but inside the armies times were ‘wildly’ different
The author pointed out watches lost time, even if they were wound twice a day, some officers set time to London or Paris time, some to their own homes back in Britain or Germany or France, some to local time and some to local time a few days before. So there could be any random number between zero and thirty minutes difference between watches on the field that day.
For some one telling position across the L&C route an hour is five to six hundred miles. A loss of just a few minutes is off by forty to fifty miles. About a 1/6 of a mile per second off.

The French, being French, refused to recognize the Greenwich Prime Meridian and used Paris as the Prime Meridian. This meant that French time varied 1/2 hour from everybody else!

 

[FishDFly]

Most of the group carried pocket watches. In Patrick Gass's Journal he is always mentioning what time they were doing something.

 

[tenngun]

The French, being French, refused to recognize the Greenwich Prime Meridian and used Paris as the Prime Meridian. This meant that French time varied 1/2 hour from everybody else!

Time zones had yet to be set at the time of Waterloo. Nor any international agreement on longitude. With the ability to keep time at sea ships could know their position but in 1815 it was not uncommon still to use your home port as your starting point.
As the fastest communication was via symaphore or a light system. Each town at that time set its clocks to local noon.
Good lord do you have any idea how hard it is for me to make an excuse for the French,
I need to go and wash my hands now.

 

[Coot]

Local time lasted beyond the timeframe of this forum. Railroads were the driving force behind standard time zones.