Water depression flow meter for oxygen
Date of manufacture:
The outer cylinder is filled with water to the marked level. The inner glass tube has a succession of loes below the waterline. Delivered oxygen depresses the water level in the tube in proportion to the flow and causes bubbles to appear betraying the degree of depression. The device calibration is engraved on the immersed metal plate alongside the tube.
Macintosh Mushin & Epstein 'Physics for the Anaesthetist', 3rd Edn. 1963, Blackwell