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It is well-known that tlie number of revolutions at which the operation of a turbine shows the greatest efficiency and economy, is considerably greater than the number of. revolutions at which a ship's propeller is most efficient. Hence when a turbine is used for marine propulsion, it is neces sary either to compromise by adopting an inter mediate speed at which neither the e�gine nor the propeller operates under conditions of greatest efficiency, or to interpose a speed reducing gear between the turbine and the propeller shaft. The construction of a satisfactory speed reducing gear adapted to the requirements of ship propulsion has offered unexpected difficulties. Dr. Foettinger's speed reducing gear consi�ts of a rotary pump driven direct by the turbine and combined in one structure with a water wheel secured upon the propeller shaft. .The water circulates in a closed path formed by the pump, the water wheel and the stationary channels inter posed between the pump and the water wheeL This speed-reducing gear or hydraulic transmission device is called a transformer, and in conjunction with its driving turbine constitutes the turbo transformer. For this new drive, Dr. Foettinger claims not only an efficiency ranging from 70 per cent to S5 per cent and generally exc. eeding 80 per cent, but further the advantage of easy reversibility and of a comparatively small reduction of efficiency when the ship is steaming at cruising speed.