On Fri, 14 Nov 2008 22:17:05 +0000 (GMT), "Dave Liquorice"
wrote:

On Fri, 14 Nov 2008 17:18:02 +0000, wrote:

Is the mercury not sealed in?

Engage brain how could air pressure shove down on the reservior pushing
the column of mercury up the tube if it was sealed in...

is it not to prevent the mercury splitting with the problem of getting
it all back together again?

Are you thinking thermometer not barometer? Thermometers are sealed.

Probably so...lol