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    Re: Help W French Surveying Compass With Altitude??
    From: Joel Jacobs
    Date: 2005 Apr 30, 11:25 +0000
    Thanks Renee,
    No one could have done a more scholarly job.
    Joel Jacobs
    Visit our website

    -------------- Original message from Renee Mattie <ReneeMattie{at}HOTMAIL.COM>: --------------

    > I believe I am finished translating the sheets on the top and bottom of the
    > case.
    > You can see it all at http://home.comcast.net/~reneemattie/navigation
    > I think I have got the sense of the instructions. I don't mind whether
    > "the carton at shoulder straps" is something that came with this compass
    > or a common (at the time) phrase for some kind of backpack or satchel,
    > though I am curious.
    > I have never come within 1000 miles of the item, but it seems to be
    > a standard compass with a decent sight, something like a cross between
    > a more modern lensatic and a hiker's compass. It seems to have no
    > internal dampening. It is up to the operator to dampen the oscillations
    > with! a brake. I imagine this takes a bit of skill. The face is divided
    > into
    > 6400 parts, which seems a bit odd. The bearing is read from the map. The
    > needle is held captive with a brake, the compass is set on the map with the
    > immobilized needle aligned to the map's magnetic north, the edge of the box
    > running through the sighted object or the current position, and the bearing
    > is read from the map.
    > The compass can be held sideways to measure the incline of a cannon, or to
    > take the height of a distant object. This is the altitude part.
    > One is to sight through the slit stem just as when one is taking an azimuth.
    > The brass inclinometer needle is then viewed in the mirror.
    > There is a graph on the back for figuring slopes (1 in 8, etc.)
    > as well as height or distance off (depending on which is known).
    > This is exactly the sort of little puzzle I am good at! , I suppose,
    > and I have enjoyed scraping together my rusty French, some geometry,
    > and my land navigation skills to figure out the 100-odd-year-old
    > instructions on this obscure, outmoded, virtual device.
    > Renee
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