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    Re: Children's land-locked "Sextant"
    From: Fred Hebard
    Date: 2007 Nov 29, 08:25 -0500

    I'm not sure the risk is minimal.  Other solutions work fairly well,
    such as using a machinist's level on a flat mirror or cooking oil
    over Karo corn syrup.
    On Nov 29, 2007, at 8:17 AM, glapook@pacbell.net wrote:
    > Gary writes:
    > Navigators have used mercury for years (Lewis and Clark used it when
    > crossing America) and I have never heard of any ill health effects
    > when used in this manner. There is a big difference in risk from
    > exposure to mercury vapor on an everyday basis for many years in an
    > inclosed space (your example and the classic "Mad Hatter") and the
    > occasional use of it outdoors for navigation. "Why voluntarily expose
    > yourself to" it? because it works very well for this purpose, better
    > than anything else and the risk is minimal.
    > gl
    > On Nov 28, 5:06 pm, "Robert Eno"  wrote:
    >> Quite a few years ago -- I think it was during a course where we were
    >> learning how to lab pack hazardous waste -- we were told a story
    >> about the
    >> high incidence of minimata disease amongst high school science
    >> teachers. The
    >> cause?  Broken mercury thermometers and the students' practice of
    >> simply
    >> dumping the waste mercury down the sink drain. Mercury being a
    >> very heavy
    >> metal, simply lodged in the sink trap and stayed there for years,
    >> slowly
    >> volatilizing and dispersing in the science lab. The science teachers,
    >> because they spent so much time in the lab, day after day, year
    >> after year,
    >> suffered a much higher than normal body loading of mercury. Result,
    >> short-circuited nervous system.
    >> Unfortunately I do not have a citation for this story but can
    >> probably find
    >> one from a colleague.
    >> Not to dismiss what Geoffrey has written, but in my opinion -- and I
    >> regularly deal with hazardous wastes -- mercury is not something
    >> to be
    >> trifled with, nor would I ever recommend it to anyone for use as an
    >> artificial horizon. I may come off sounding like a scared old
    >> maid, but the
    >> world being what it is nowadays; that is loaded with contaminants
    >> of all
    >> kinds, why voluntarily expose yourself to even more?
    >> Robert
    >> ----- Original Message -----
    >> From: "Geoffrey Kolbe" 
    >> To: 
    >> Sent: Wednesday, November 28, 2007 4:08 PM
    >> Subject: [NavList 4154] Re: Children's land-locked "Sextant"
    >>> Gary LaPook wrote:-
    >>>> With use it develops a dross floating on the surface which can be
    >>>> removed by filtering it through a piece of cloth like an old t-
    >>>> shirt.
    >>>> You have to twist the cloth to force the mercury though the
    >>>> cloth and
    >>>> it comes though in shiny little balls leaving the dross in the
    >>>> cloth
    >>>> which I then dispose of. You should probibly wear gloves when
    >>>> handling
    >>>> the mercury like this.
    >>> In the 1960's the old Royal College of Science in London was
    >>> pulled down
    >>> to
    >>> build Imperial College, the British attempt to emulate MIT in the
    >>> United
    >>> States.
    >>> The Spectroscopy labs in the RCS had long been plagued with the
    >>> problem
    >>> that continuum spectra always had absorption lines of mercury on
    >>> them. On
    >>> taking up the parquet floor in the lab, a veritable lake of
    >>> mercury was
    >>> found underneath! As far as I know, all the researchers of that
    >>> era lived
    >>> to a ripe old age, despite working for many years in an
    >>> environment where
    >>> the mercury vapour in the air was probably at saturation point.
    >>> Not that I am advocating that we should not take suitable
    >>> precautions when
    >>> using poisonous substances like mercury - its just that people
    >>> somehow
    >>> seem
    >>> to be more susceptible to such things than they used to be in times
    >>> past.... or, at least, that is the perception.
    >>> Geoffrey Kolbe
    > >
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