Among the aerial war fleets of the Allied nations, the French offers by far the greatest field for study, since it possesses many different types of dirigibles. The _Astra_ and the _Astra-Torres_ are perhaps the chief representatives of the non-rigid design, and are generally considered the most successful of the French airships. The _Astra_ is the older model, and, like the _Zodiac_, has the long wooden framework or car girder, hung directly to the base of the envelope and distributing to all parts of it the weight of the car. It can be recognized by this and by its stabilizers or small inflated gas bags around the stern of the envelope. The _Astra_ is of medium size, varying in length from 199 to 275 feet. The _Astra-Torres_ is very much longer, those of the 1914 type measuring 457 feet from nose to stern. From the exterior, this airship has a peculiar three-lobed appearance. It tapers very slightly to the stern and is pointed at both ends, but it has not the _Astra's_ inflated stabilizers. Another French airship of non-rigid design is the _Clement-Bayard_. It is similar in design and in size to the _Astra_, but without the inflated stabilizers. Rounded slightly at the nose, the envelope tapers to a sharp-pointed stern. The _Lebaudy_ is the chief example of a French semi-rigid airship. The envelope is long and cylindrical, pointed at the nose and rounded at the stern, where it is fitted with stabilizing "fins." The base of the envelope is fitted to a long keel, which ends at the rear in a rudder and fins. From this keel the car is suspended by strong cables, and beneath the car extends a conical structure of steel tubes, with points falling downward. These serve as a protection in case of a sudden landing. In front of the car and on each side of the keel are planes similar to those of an airplane, which help to give balance to the ship. Among airships of the Allies, the French _Speiss_ furnishes an example of the purely rigid design. Constructed on the plan of the German Zeppelin, its envelope has an inner wooden framework which holds it in place. The _Speiss_ is a large dirigible, measuring about 450 feet. It carries two cars, and in each is a two-hundred horse power motor, giving it great speed. PART III CHAPTER I EARLY EXPERIMENTS WITH HEAVIER-THAN-AIR MACHINES