What is "sprengel pump"

Sprengel pump \Spreng"el pump`\ (spr[e^]ng"el p[u^]mp`). (Physics) A form of air pump in which exhaustion is produced by a stream of mercury running down a narrow tube, in the manner of an aspirator; -- named from the inventor.

The Sprengel pump is a vacuum pump that uses drops of mercury falling through a small-bore capillary tube to trap air from the system to be evacuated. It was invented by Hanover-born chemist Hermann Sprengel in 1865 while he was working in London. The pump created the highest vacuum achievable at that time.