ently to begin again, they resolved to make him their teacher and to
take a lesson from him.

Count Zeppelin was about sixty years old when he began to make airships;
he had been long studying the problem and preparing his plans; so that
his many airships do not much differ among themselves in general design,
and a description of the first gives a fair enough idea of its
successors. It was a pencil-shaped rigid structure, about four hundred
and twenty feet long, with a diameter almost exactly one-eleventh part
of its length. The framework, built of aluminium, consisted of sixteen
hoops, connected by longitudinal pieces, and kept rigid by diagonal wire
stays. Before it was covered it resembled a vast bird-cage, and looked
as frail as a cobweb, but was stronger and stiffer than it looked. It
was divided by aluminium bulkheads into seventeen compartments; of these
all but the two end compartments contained separate balloons or
gas-bags. Two or three of these might collapse without completely
destroying the buoyancy of the ship. The whole structure was covered
with a fabric of rubberized cotton. A triangular latticed aluminium keel
ran along below, to give strength to the ship, and to furnish a
passage-way from end to end. At points about a third of the way from
either end of the ship spaces in the keel were made for the two cars, in
each of which was a sixteen horse-power Daimler motor driving two small
high velocity airscrews, one on each side of the ship. The lateral
steering was done by a large vertical rudder, placed aft. The
longitudinal balance was controlled in several ways. In the first ship a
heavy sliding weight in the keel was moved at will, fore and aft. This
was supplemented or superseded in later ships by four sets of elevating
planes, two sets in the fore-part and two sets aft. An advantage of the
rigid ship is that she can tilt herself without danger from the pressure
of the gas on the higher end. Moreover, she can be driven at a very high
speed, and the gas-bags, being housed in the compartments and protected
from the outer air, are less liable to sudden contraction and expansion
caused by variations of temperature.

The great disadvantage of the rigid type has hitherto been that in bad
weather the airship cannot land. A non-rigid airship in a nasty wind can
land and deflate itself at once by ripping the panel in the envelope, at
no greater price than the loss of its gas, and probably some damage to
its c