The apparatus consists of an open-ended cylindrical brass tube, 100 cm long and 2.5cm dia, mounted on a polished wooden board. The tube is sealed tightly at the lower end with a side tube connected to a brass reservoir using rubber tubing. The reservoir is mounted on a support, which when raised or lowered, increases or decreases the height of the water column respectively. The height of the column is determined by measuring the distance between the zero-stop and the lower end of the tube using the meter scale attached to the apparatus.