The effect of the level in the separation tank of a laboratory Jameson cell on downcomer behaviour -pressure, pool level, gas flowrate, and gas holdup - was studied. When The initial gas flowrate was uncontrolled, changes in the separation tank level affected the downcomer: for example, a decrease in level caused a decrease in pressure and pool level and an increase in gas rate and gas holdup. When the gas flowrate was maintained constant, level changes in the separation tank changed downcomer pressure in the same manner as before bur now had no effect on pool level or gas holdup.