2. IN COMBINATION A COMBUSTION CHAMBER IN WHICH A FUEL IS BURNED, AN ABSORPTION CHAMBER PARTIALLY FILLED WITH WATER, A FLUE SURMOUNTED BY ONE OR MORE SUPERHEATER TUBES WITHIN SAID ABSORPTION CHAMBER, SAID SUPERHEATER TUBES RISING ABOVE THE SURFACE OF SAID WATER AND TERMINATING BELOW THE SURFACE OF SAID WATER, A VACUUM PUMP CONNECTED THROUGH HEAT ABSORBING DEVICES TO A POINT ABOVE THE LEVEL OF SAID WATER IN SAID ABSORPTION CHAMBER AND DRAWING FLUE GASES RESULTING FORM THE COMBUSTION OF SAID FUEL THROUGH SAID FLUE, SAID SUPERHEATER TUBES OR TUBE, SAID WATER, SAID HEAT ABSORBING DEVICES AND DISCHARGING TO THE ATMOSPHERE.