vacuum-pot

from The Century Dictionary.

• noun A chamber within which pressures less than that of the atmosphere and approximating a vacuum are maintained; specifically, a form of steam-engine condenser having the shape of a pot, in which a vacuum is maintained by placing it at the upper end of a water-column 32 feet or more high, so that water drains out of it by gravity and without a pump, maintaining a vacuum which would be Torricellian except for the vapor of warm water and the air entrained with the steam and injection-water, or present from leakage.