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    Re: Artificial Horizon, K & E USN No. 6
    From: Alexandre Eremenko
    Date: 2012 Oct 26, 09:15 -0400

    Bruce,
    
    > The basin is cast iron .  The jug also appears to be cast iron. The top
    > also seems to be  cast, but the inside is quite polished and threaded.  I
    > guess I never realized that cast iron could be threaded and shaped so
    > carefully.
    
    The reason is that mercury interacts (amalgamize) with metals like copper,
    bronze or brass. So the only appropriate material is iron.
    The reason why it is so carefully polished is that any dirt can be removed
    easily.
    Nowadays the use of mercury is severely restricted by the government
    regulations
    (because of the environmental concerns), so hardly anyone will use
    it with mercury, but this is a rare collectable.
    
    For the same reason, mercury barometers are not sold anymore.
    8 years ago you could see on e-bay fine marine barometers on gimbals,
    and even buy a new "stick barometer".
    
    Alex.
    
    
    
    

       
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