. The "M-IV"
completed in 1913 is the largest of this type, and differs from its
prototypes in that it carries two cars, each fitted with motors, whereas
the earlier machines were equipped with a single gondola after the
French pattern. This vessel measures 320 feet in length, has a maximum
diameter of 44 1/2 feet, displaces 13 tons, and is fitted with motors
developing 450 horse-power, which is sufficient to give it a speed of
47 miles per hour. This vessel represents a huge advance upon its
predecessors of this design, inasmuch as the latter were about 245 feet
in length by 36 1/4 feet in diameter, and displaced only six tons,
while the single car was provided with a motor developing only 150
horse-power, the speed being 28 miles per hour. Thus it will be seen
that a huge development has suddenly taken place, a result due no doubt
to the co-operation of the well-known engineer Basenach. The "M-IV"
is essentially an experiment and great secrecy has been maintained
in regard to the trials which have been carried out therewith, the
authorities merely vouchsafing the fact that the airship has proved
completely successful in every respect; conclusive testimony of this
is offered by the inclusion of the vessel in the active aerial fleet of
Germany.

But it is the Parseval which is regarded as the finest type of airship
flying the German flag. This vessel is the product of slow evolution,
for it is admitted to be a power-driven balloon. Even the broad lines
of the latter are preserved, the shape being that of a cylinder with
rounded ends. It is the direct outcome of the "Drachen-Balloon,"
perfected by Parseval and Siegsfeld, the captive balloon which is an
indispensable part of the German military equipment.

The complete success of the suspension system in this captive balloon
prompted Parseval to continue his researches and experiments in regard
to the application of power to the vessel, so as to induce it to move
independently of the wind. The suspension system and the car are the
outstanding features of the craft. It is non-rigid in the strictest
interpretation of the term, although, owing to the incorporation of
the steadying hollow "mattress" (as it is called by its inventor), the
strength of the suspension system, and the substantial character of the
car, it conveys an impression of great solidity. The thinnest rope,
both manilla and steel, in the suspension system is as thick as a man's
finger, while the car, measu