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Archimedes meets the Tare Bar.



My loved one, Norma was given a well-rounded rock of perhaps
5 cm diameter.
She believed there was a possibility it could be a geode (like the
half rock with interior blue quartz crystals we bought in Arizona,
half a lifetime ago.)

When she asked for a hammer to demolish it with, I suggested a
preliminary test.
I measured its weight, then found a beaker with enough water to
cover it, and a line to hang it from. At this point I would
sometimes reweigh the object while suspended in the water jar.
You will realise I'm sure that this is not the swiftest method -
but habit makes slaves of us.

This time I made use of the tare bar to null the water beaker's
weight, so that the beaker's gain in weight was directly indicated
after the stone was suspended. (i.e. without much consideration,
I stumbled into what I expect is the standard method.)

It is an embarrassment to confess that seeing the stone increase
the water level while the scale indicated the weight of water
displaced, gave me a graphic view at last of the increased head
of water in the beaker, with the consequent increase in down
pressure on the base of the beaker, so that I could reasonably
visualize that the new lamina of water at the surface represented
the reason for the weight indication, representing a stone's volume
of water.
Because the ratio of its dry weight to that of the displaced water
was very like the relative density of quartz, I pronounced against
the likelihood of a potential geode.

The little song and dance accompanying this scientific tour de force
attracted the attention of my younger son, who had also been cherishing
what he called his fossil. This was a leg joint bone of some smallish
animal which seemed so hard, that he believed it could be stone.

The relative density determination seemed to correspond well with the
figure for bone rather than stone, so it seems my Archimedean
recipe extinguished two harmless day dreams.

Oh well!



brian whatcott <inet@intellisys.net>
Altus OK