Author Topic: Barometer Attached Thermometer  (Read 5334 times)

Randi

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Re: Barometer Attached Thermometer
« Reply #15 on: January 01, 2013, 07:55:00 am »
I haven't seen anything from Bunts in a long time. I've been thinking about him too. His knowledge and humor and humor are much missed!

Randi

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Re: Barometer Attached Thermometer
« Reply #16 on: January 01, 2013, 08:24:37 am »
Randi_2 and Janet,
                                Thanks for your re-assuring replies.  if you wish to know a bit more about
barometers at sea, look at :  http://en.wikipedia.org/wiki/Robert_FitzRoy .   There's a paragraph
about his work in Meteorology plus some sea-going history.

TuxfordC.

Thanks, the Meteorology section was interesting. We have, or will have, ships from that period.

Craig

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Re: Barometer Attached Thermometer
« Reply #17 on: January 01, 2013, 10:39:56 am »
I haven't seen anything from Bunts in a long time. I've been thinking about him too. His knowledge and humor and humor are much missed!

Did you mean "and humour"?  ;)

Caro

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Re: Barometer Attached Thermometer
« Reply #18 on: January 01, 2013, 11:31:28 am »
Bunts! I'll see if I can reach him.

Pleased to meet you, TuxfordC.

Craig

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Re: Barometer Attached Thermometer
« Reply #19 on: January 01, 2013, 11:45:19 am »
I am also pleased to meet you TuxfordC. That was an interesting article about Robert Fitzroy. Darwin was in good hands with him as captain.

Randi

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Re: Barometer Attached Thermometer
« Reply #20 on: January 01, 2013, 11:49:36 am »
I haven't seen anything from Bunts in a long time. I've been thinking about him too. His knowledge and humor and humor are much missed!

Did you mean "and humour"?  ;)

No, I just meant to imply some doubt about his humor being missed ;)

Love to all my OW family!

tuxfordc

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Re: Barometer Attached Thermometer
« Reply #21 on: January 02, 2013, 04:57:10 am »
Quote:  "When I read your initial question, TuxfordC, I was glad to hear the answer to an itch at the back of mind - how some mercurial barometers can be recorded without any attached thermometer." 

 Janet,
            Barometers were around for a while before folk started thinking about temperature corrections.  There another factor too.
We/they are supposed to be reading the height of a column of mercury that indicates the pressure of the air.  At the bottom of every
practical barometer is a reservoir that stores the mercury that's not in the 30 inch  tube. As the height of the tube column
varies, so does the height of the mercury in the reservoir.  The Fortin pattern barometers make allowance for this by making the
reservoir partly of leather which can be squeezed by an adjusting screw to vary the height of mercury in the reservoir.  There is
a fixed marker pointer, once made of ivory, and the observer has to adjust the reservoir until the marker is just touching the surface
of reservoir mercury.  Then, the reading at the top of the column is correctly showing the height of that column and hence the pressure.

I found it hard to enough to correctly adjust the pointer when on stable Mother Earth (according to my Tutor) so can imagine the
difficultly of using a Fortin pattern on a pitching and rolling vessel. Perhaps they did not?  Certainly barometers are mounted in
gymbals, even on land, but the only ones I have read at sea were aneroid pattern relying on an accurate metal vacuum box rather
than a column of mercury.
  TuxfordC

  PS  Thankfully they used mercury instead of water. A water barometer is about 30 feet.One could be taking baro' readings up in the tops'ls.

Janet Jaguar

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Re: Barometer Attached Thermometer
« Reply #22 on: January 02, 2013, 06:49:49 am »
By the logs we've seen, both the Royal and US Navies were switching over from mercurial to aneroid  - beginning at the turn of the century for the US, and during WWI for the Royal Navy.  Every ship with a working instrument kept it for its lifetime.  When a new instrument was needed, the aneroid was mostly the one installed.  And by the online pictures at the Greenwich Maritime Museum, all of them always had an attached thermometer and gimbals.  You'd know more than me about their details looking at the pictures.

Quote
Greenwich Museum online photo, part of caption
This is an early marine barometer and dates from around 1800. As far back as 1668, when Robert Hooke presented his findings on the matter to the Royal Society, it was thought that the ability to measure air pressure at sea would be advantageous. The problem of the oscillation of the mercury caused by the motion of the ship, however, meant it was to be another century before such a measuring instrument was perfected. This example has a round mahogany case with a silvered brass scale and a thermometer fitted to the inside of the barometer door. A manual vernier is fitted to the barometer scale to ensure that accurate readings can be taken. It would have been hung from brass gimbals and was weighted to ensure it remained upright on board ship.