CIRCLING EIFFEL TOWER IN AIR SHIP. 587 



and the solution spelled itself on his brain. That is, he reflected that 

 the inflated crinoline had become lighter than air. So he set to work 

 and astounded the world with the first balloon, an humble paper 

 globe tilled with hot air that soared upward but a few yards. Thus 

 having once got into the air, man has ever since been trying and try- 

 ing to steer himself while there. But any motor that would be 

 powerful enough has always made the balloon heavier than air. For 

 instance, Henri Giffard in 1852 tried steam as motive power, and he 

 was the first to adopt the cigar-shaped bag, but his engine would not 

 propel the balloon, simply because it had to be too light for the power 

 exacted of it. Twenty-five years later Dupuy de Lome went back to 

 first principles and tried manpower, but the man was even less ade- 

 quate than Giffard's feeble engine. In 1883 another Frenchman, Tis- 

 sandier, experimented with electricity, but as his batteries had to be 

 light enough to be taken up in the balloon, the} 7 proved effective only 

 in helping to weigh it down to earth again. Krebs and Renard, mili- 

 tary aeronauts, succeeded better with electricity, for they could make 

 a small circuit with their airship, provided only that no air was 

 stirring. Enthusiasts cried out that the problem was solved, but the 

 two aeronauts themselves, as good mathematicians, figured out that 

 they would have to have a motor eight times more powerful than their 

 own, and that without any increase in weight, which was an impossi- 

 bility at that time. 



Shortly after this, though, people began to drive round in carriages 

 without horses, and their motive power was the gasoline engine. Tis- 

 sandier's electro motor weighed 375 pounds per horsepower; Santos- 

 Dumont's petroleum motor, 12 pounds per horsepower. In both cases 

 fuel and all accessories are included. Now, just cxactl} 7 in this enor- 

 mous difference of weight lies the secret of aerial navigation as solved 

 the other da} r by the young Brazilian. 



The explanation why the petroleum motor is such a tremendous 

 giant for its size is very simple. The greater part of its fuel is in the 

 air itself, and the air is all around the balloon, all ready for use. The 

 aeronaut does not have to take it up with him. If he did, he would 

 be crushed to earth with the weight of his reservoir. But that pro- 

 portion of his fuel that he must carry, the coal-oil can, is compara- 

 tively insignificant. The difference between carrying this fraction 

 and carrying all the fuel, as for steam or electricity, makes the differ- 

 ence between the newer kind of motor and the two old kinds. A few 

 figures will prove startling. Two and one-half gallons of gasoline, 

 weighing 15 pounds, will make a 2£ horsepower autocycle cover 94 

 miles in four hours. Santos-Dumont's balloon needs less than 5^ gal- 

 lons for a three hours" trip. It weighs but 37 pounds, and occupies 

 the slender cigar-shaped brass reservoir which you will notice near 

 the motor. Now, then, an electric battery of the same power would 



