So much has been said and written concerning the Zeppelin airship, particularly in its military aspect, that all other developments in this field have sunk into insignificance so far as the general public is concerned. The Zeppelin dirigible has come to be generally regarded as the one and only form of practical lighter-than-air type of aircraft. Moreover, the name has been driven home with such effect that it is regarded as the generic term for all German airships.

These are grievous fallacies. The Zeppelin is merely one of a variety of types, even in Germany, although at the moment it probably ranks as the solitary survivor of the rigid system of construction. At one time, owing to the earnestness with which the advantages of this form of design were discussed, and in view of the fact that the Zeppelin certainly appeared to triumph when all other designs failed, Great Britain was tempted to embrace the rigid form of construction. The building of an immense vessel of this class was actively supported and it was aptly christened the "May-fly." Opponents of the movement tempered their emphatic condemnatory criticism so far as to remark that it MAY FLY, but as events proved it never did. The colossal craft broke its back before it ever ventured into the air, and this solitary experience proving so disastrous, the rigid form of construction was abandoned once and for all. The venture was not in vain; it brought home to the British authorities more convincingly than anything else that the Zeppelin was a mechanical monstrosity. The French never even contemplated the construction of such a craft at that time, estimating it at its true value, and the British failure certainly served to support French antagonism to the idea. Subsequently, however, an attempt at rigid construction was made in France with the "Spiess" airship, mainly as a concession to public clamour.

Even in Germany itself the defects of the Zeppelin were recognised and a decided effort to eliminate them was made by Professor Schutte in co-operation with a manufacturer of Mannheim named Lanz. The joint product of their ambitions, the Schutte-Lanz, is declared to be superior to the Zeppelin, but so far it has failed to justify any of the claims of its designers. This vessel, which also favours the colossal, is likewise of the rigid type, but realising the inherent dangers accruing from the employment of metal for the framework, its constructors have used wood, reinforced and strengthened where necessary by metallic angle-iron, plates, and bracing; this utilisation of metal is, however, carried out very sparingly. The first vessel of this class was a huge failure, while subsequent craft have not proved much more successful.

In fact, one of the largest German airships ever designed, L4, is, or rather was, a Schutte-Lanz, with a capacity of 918,000 cubic feet, but over 6,000 pounds lighter than a Zeppelin of almost similar dimensions. I say "was" since L4 is no more. The pride of its creators evinced a stronger preference for Davy Jones' Locker than its designed realm. Yet several craft of this type have been built and have been mistaken for Zeppelins owing to the similarity of the broad principles of design and their huge dimensions. In one vital respect they are decidedly inferior to their contemporary - they are not so speedy.

The most successful of the German lighter-than-air machines are those known respectively as the semi rigid and non-rigid types, the best examples of which are the Gross and Parseval craft. Virtually they are Teutonic editions of the successful French craft of identical design by which they were anticipated. The Lebaudy is possibly the most famous of the French efforts in this direction. The gas-bag has an asymmetrical shape, and is pointed at both ends, although the prow is blunter or rounder than the stem. The gas-bag comprises a single chamber for the inflating agent, the distended shape of the envelope being sustained by means of an air-ballonet. By varying the contents of the latter through the agency of a pump the tension of the gas in the lifting envelope can be maintained, and the shape of the inflated balloon preserved under all conditions.

Beneath the gas-bag is a long strengthened girder, and from this in turn the car is suspended. It is the introduction of this rigid girder which is responsible for the descriptive generic term of "semi-rigid." On the other hand the "non-rigid" type may be roughly described as a pisciform balloon fitted with propelling machinery, inasmuch as the car containing the driving machinery is suspended from the balloon in the manner of the car in the ordinary drifting vessel. So far as the French effort is concerned the Bayard-Clement type is the best example of the non-rigid system; it is represented in Germany by the Parseval class.