of very
similar design, and were composed of trestles with some ordinary form
of roof-truss. They were covered externally with corrugated sheeting.
The doors have always been a source of difficulty, as they are
compelled to open for the full width of the shed and have to stand
alone without support. They are fitted with wheels which run on guide
rails, and are opened by means of winches and winding gear.

The later sheds built to accommodate the rigid airship are of much
greater dimensions, and are constructed of steel, but otherwise are of
much the same design.

The sheds are always constructed with sliding doors at either end, to
enable the ship to be taken out of the lee end according to the
direction of the wind.

It has been the practice in this country to erect windscreens in order
to break the force of the wind at the mouth of the shed. These screens
are covered with corrugated sheeting, but it is a debatable point as to
whether the comparative shelter found at the actual opening of the shed
is compensated for by the eddies and air currents which are found
between the screens themselves. Experiments have been carried out to
reduce these disturbances, in some cases by removing alternate bays of
the sheeting and in other cases by substituting expanded metal for the
original corrugated sheets.

It must be acknowledged that where this has been done, the airships
have been found easier to handle.

At the outbreak of war, with the exception of a silicol plant at
Kingsnorth, now of obsolete type, and a small electrolytic plant at
Farnborough, there was no facility for the production of hydrogen in
this country for the airship service.

When the new stations were being equipped, small portable silicol
plants were supplied capable of a small output of hydrogen. These were
replaced at a later date by larger plants of a fixed type, and a
permanent gas plant, complete with gasholders and high pressure storage
tanks was erected at each station, the capacity being 5,000 or 10,000
cubic feet per hour according to the needs of the station.

With the development of the rigid building programme, and the
consequent large requirements of gas, it was necessary to reconsider
the whole hydrogen situation, and after preliminary experimental work
it was decided to adopt the water gas contact process, and plants of
this kind with a large capacity of production were erected at most of
the larger stations. At others electrolytic