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Thread: Caliper Paris Meter?
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12th Dec 2010, 02:04 PM #1New Member
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Caliper Paris Meter?
Hi,
Maybe someone here can help, I cant find any info on a an old brass caliper that has the words, Paris and Meter on it. On one side of the slide it has graduations up to 80mm and the other side has up to 33 units of unknown measure.
Reading the scale shows that 64 mm is aproximately 28.5 units on the other side.
Can anyone identify what the caliper was used for?
Thanks
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12th Dec 2010, 05:08 PM #2
Hi Billy4T, I have seen similar ones that jewellers use, see the photo below, that has inches and meter stamped on it, I am not sure but I google Paris unit of measurement and I found this in wikipedia, may be is related, if so you may really have an antique there, hope it helps,
cheers, Richard.
The French law for the definitive metre of 1799 states that one decimal metre is exactly 443.296 French lines, or 3 French feet, 0 French inches and 11.296 French lines. The French royal foot is exactly 9000/27706 metres, or about 0.3248 metres.[1]
In Quebec, the surveys in French units were converted using the relationship 1 pied (of the French variety, the same word being used for English feet as well) = 12.789 English inches.[2] This makes the Quebec pied very slightly smaller (about 4 parts in one million) than the pied used in France.
This article uses the Paris definitions for the coutume of Paris[3], and definitions for other Ancien régime civil jurisdictions varied, at times quite significantly.
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12th Dec 2010, 05:17 PM #3
Found more info
Paris foot an English name for the French royal foot (pied de roi, see below). Paris point a unit of length equal to 2/3 centimeter (0.2625 inch) used to measure shoe size in most European countries.
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12th Dec 2010, 05:28 PM #4
OK this is the one we were looking for
Paris inch
From Wikipedia, the free encyclopedia
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"The Paris inch is commonly employed as the unit by which to express the focal length of lenses, and it cannot, therefore, be dispensed with"—The Ophthalmoscope (1864)
[1]The Paris inch, or pouce, is an old unit of measure, that among other uses, was common for giving the measurement of lenses.[1] The Paris inch could be subdivided into 12 ligne (Paris line), and 12 Paris inches made a Paris foot.[1] The Paris inch and Paris foot could be abbreviated with " and ' like some other inch/foot units.[1] It was larger than the English inch and the Vienna inch, although the Vienna inch was subdivided with a decimal, not 12 lines. [1]
A Paris inch is equal to 27.069 millimetres.[2] The Paris inch was also known as a pouce.[3]
A famous example of its use is in the first Great Refractor. It had a lens made by Joseph von Fraunhofer which was 9 Paris inches in diameter, which works out to about 24 cm or 9.6 inches (English inches) aperture achromatic lens (the largest of its day).[4][5]
Cheers ,Richard
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12th Dec 2010, 07:33 PM #5
Nice detective work Richard, I think you are spot on...
If one meter == 443.296 French Lines, then 1mm==0.443296 French Lines
So 64mm would be 28.37 French Lines.
That looks to me like the markings on the calipers might be in French Lines..
It would be interesting to get some idea of the date...
Regards
Ray
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12th Dec 2010, 09:31 PM #6New Member
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Looks like it's French lines
Dano48 and RayG,
Thank you very much for the detailed replies!
I bought a old pineapple can of junk at a garage sale and found the calipers lying at the bottom of the can.
I wonder how old it is?
In any case its a nice tool that fits in the hand well, no plastic nor batteries!
Thanks again.
Great site !
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12th Dec 2010, 11:50 PM #7
Glad I could help, if you want to find out how old it is, do your own bloody research
Cheers, Richard.