The maintenance of a constant total lift in lighter-than-air craft falls naturally into two distinct divisions: (1) Recovery of ballast as the consumption of fuel tends to lighten the ship. (2) Control of the temperature and thus the density of the lifting gas in order to compensate for changes of lift due to changes of atmospheric density or superheating of the lifting gas by solar radiation upon the envelope. the recovery of water of combustion from engine exhaust gas by cooling and condensation is feasible as a method for solution of the first problem. This report discusses the principles involved and describes the operation of experimental apparatus installed on No. 1 Naval Airship.