Describing how the total weight of an airship becomes less as its flight continues and how its elevators can be used to keep the airship's nose pointed downward, thus balancing the excess lift by “dynamic lift,” the author says that 5 hr. is about the limit of flight for which the too great lightness can be overcome in this fashion safely, explains how different the conditions become on long flights and gives details of the means used to counteract this rising tendency.
Valving of gas to overcome airship lightness is wasteful and costly, especially when the craft is inflated with helium gas but, if this is not done, some substance must be collected and stored at the same rate as that at which fuel is consumed in the engines and the most practicable method seems to be to recover water from the exhaust gases.
Gasoline combustion is analyzed and it is brought out that, for every 100 lb. of gasoline burned, 145 lb. of water is present in the exhaust, varying somewhat with the weather conditions and the composition of the fuel. The problem is to make available, as ballast, two-thirds of the water known to be present. How it is present is explained and means for its utilization discussed.
Experimental work that led eventually to the equipment of the airship Shenandoah with water-recovery apparatus is reviewed and the results following its installation are stated.