Air-Pump
an instrument invented by Otto von Guericke of Magdeburg, in 1650. It was designed to exhaust the air from a receiver. The air-pump now genthat they are made to take. The valve will then fly open, and the air from the receiver will fill both the cylinders as well as itself, though, of course, now in a somewhat rarefied state. As the same process is again and again repeated, the air will become increasingly rarefied, though, as stated above, an actual vacuum never can result from the action now described.