MILITARY AEEONAUTICS SQUIEE. 131 



Propellers. — A pair of three-bladed metal propellers about 15 feet 

 in diameter is placed opposite each car, firmly attached to the frame 

 of the envelope at the height of the center of resistance, where they 

 are most efficient. 



Stahility. — In addition to the long V-shaped keel under the rigid 

 frame, on each side at the rear of the frame are two nearly horizontal 

 planes, while above and below the rear end are vertical fins. 



Steering. — A large vertical rudder is attached at the extreme end 

 of the rigid frame, and an additional one is placed between each set 

 of horizontal planes on the sides. For vertical steering there are 

 four sets of movable horizontal planes placed near the ends of the 

 rigid frame, about the height of the propellers. Each set consists of 

 four horizontal planes placed one above the other and connected with 

 rods, so that they w^ork on the principle of a shutter. These horizon- 

 tal rudders serve another very important purpose, due to the reac- 

 tion of the air. Allien these planes are set at an angle of 15° and 

 the airship is making a speed of 35 miles per hour, an upward pres- 

 sure of over 1,700 pounds is exerted, and consequently all the gas 

 in one compartment could escape and yet by the manipulation of 

 these planes the airship could return safely to its starting point. 



Its best performances were two trips made during the past summer 

 [1008]. The first, July 4, lasted exactly twelve hours, during which 

 time it covered a distance of 235 miles, crossing the mountains to 

 Lucerne and Zurich, and returning to the balloon house at Friedrichs- 

 hafen, on Lake Constance. The average speed on this trip was 32 

 miles per hour. On August 4 this airship attempted a twenty-four- 

 hour flight, which was one of the requirements made for its accept- 

 ance b}^ the Government. It left Friedrichshafen in the morning 

 with the intention of following the Rhine as far as Mainz and then 

 returning to its starting point straight across the country. A stop of 

 four hours and thirty minutes was made in the afternoon of the first 

 day on the Rhine, to repair the engine. On the return, a second stop 

 was found necessary near Stuttgart, due to difficulties with the 

 motors and the loss of gas. While anchored to the ground a storm 

 came up and broke loose the anchorages, and as the balloon rose in 

 the air it exploded and took fire, due to causes which have never been 

 actually determined and published, and fell to the ground, resulting 

 in its complete destruction. On this journey, which lasted in all 

 thirty-one hours and fifteen minutes, the airship was in the air 

 twenty hours and forty-five minutes and covered a total distance of 

 378 miles. 



The patriotism of the German nation was aroused. Subscriptions 

 were immediately opened and in a short space of time $1,000,000 

 had been raised. A Zeppelin society was formed to direct the expendi- 

 ture of this fund. Eighty-five thousand dollars has been expended 



