This instruments is equipped with two heavy glass cylinders having inner dia. of 40mm and 15mm, respectively both fitted with non-return valves, and leather covered pistons, pump worked by hand lever 31.5cm long ratio about 2:1 safety value provided in the large piston so that pressure in excess of that which can safely be applied to the glass cylinder enables the water to rise above the piston and escape through the overflow pipe at the top;