Re: Ho exactly does a Mercury Vacuume pump operate?

I recall seeing pictures of a simple mercury vacuum pump.  Yes, liquid mercury 
was used (the weight of the mercury metal was important to the operation of the 
pump.)

The mercury was allowed to dribble down through a narrow vertical tube, where 
it formed a series of droplets which fill the whole cross-section of the tube.  
As these heavy droplets fall, they move past a side pipe in the tube.  This 
pipe is connected to the light bulb.  Air in the bulb rushes into the gap 
between the drops of mercury.  The heavy mercury pushes this air down the tube, 
and when the next mercury drop passes, more air from the light bulb rushes into 
the space between the mercury drops.  At the bottom of the long tube the 
mercury and the air comes out.  At the top of the tube is a mercury resevoir 
which must be kept filled.  After the pump has run for long enough, nearly all 
of the air has been swept out of the light bulb and down the vertical mercury-
drop tube.