tim... wrote:

"Roland Perry" wrote in message
...


The problem with mercury is that even if not "abused" (whatever that
means) it has a tendency to get split, and when it does the tiny droplets
run everywhere and are very difficult to clean up.

thermometers are sealed units

Until they get broken, like the one in my dad's greenhouse which I used to
push the droplets around the wooden shelf with a long nail.


(I have no idea about barometers, but assume likewise)



The mercury column needs to be open to air pressure, but I guess there
could be a sliding piston arrangement of some kind to achieve it. My dad
has a large mercury-column barometer, which IIRC claims to be
spillage-proof even if turned upside down accidentally during transport, so
there must be a seal of some kind.


Anna Noyd-Dryver