Zeppelin No. 4 was destroyed by an accident, but Zeppelin No. 3 was recalled into the national service and in 1909 given the official title of _S.M.S. Zeppelin I_. From this time on dirigible construction in Germany went forward with the greatest speed. Two other names became prominent in the enterprise: those of Major von Parseval and Major von Gross. The "Parseval" design resembled more the French, for it was covered with "Continental fabric," was long and cylindrical, rounded at the front and pointed at the stern, with a large internal air ballonet. The car was suspended from two steel cables or trolleys, which it could slide along, altering its position and the "balance" of the whole airship. The "Gross" type of airship resembled the _Lebaudy_ and the _Patrie_, with its boat-shaped car hung from a steel platform attached to the bottom of the envelope. Out of this brief story of the development of the early airship models of all the nations, we can, if we look carefully, see certain definite types of dirigibles emerging. The experimenters had to solve this problem: What shall we do when owing to loss of gas the balloon envelope begins to get flabby? For of course a flabby, partially filled envelope would flop from side to side, destroying the balance of the airship and checking its speed. [Illustration: BALDWIN U. S. "DIRIGIBLE NO. 1"] The German inventors settled the problem by making the envelope _rigid_, either with a solid covering or with a covering of fabric stretched over an inner framework. Thus the _rigid type_ of airship was evolved. The French inventors solved the same problem by placing inside the envelope a large _empty_ bag of fabric, into which air could be pumped when necessary to fill the balloon out and hold the envelope firm. The air could not be pumped directly into the envelope itself as it would produce an explosive mixture with the gas already there. From this method of dealing with difficulty, the _non-rigid_ type of dirigible was evolved. [Illustration: THE BRITISH ARMY "BABY" DIRIGIBLE] But the _non-rigid_ dirigible presented a new difficulty: how could the car be suspended from it in such a way that it would not swing? For only with a rigid connection between the car and the envelope could the greatest speed be obtained. The _Lebaudy_ solved this problem by attaching to the base of the envelope a rigid steel flooring, from which the car could then be suspended by an immovable connection. And so was evolved the _semi-rigid_ type of airship. In recent years another solution of this problem of preventing the car from swinging has been employed to some extent: By making the car almost as long as the envelope, the connecting cables by which the car is suspended hang almost perpendicular, and there is not the same tendency to swerve as with cables slanting down to a comparatively small car. This type of airship is called the _demi-semi-rigid_.