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    Re: Children's land-locked "Sextant"
    From: Gary LaPook
    Date: 2007 Nov 29, 05:17 -0800

    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.
    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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