e and a Parseval from Germany,
both of which proved very useful in the early days of the War, doing
patrol work over the Channel before the Blimps came into being.

Early in 1915 the 'Blimp' or 'S.S.' type of coastal airship was evolved
in response to the demand for a vessel which could be turned out quickly
and in quantities. There was urgent demand, voiced by Lord Fisher, for
a type of vessel capable of maintaining anti-submarine patrol off the
British coasts, and the first S.S. airships were made by combining a
gasbag with the most available type of aeroplane fuselage and engine,
and fitting steering gear. The 'Blimp' consisted of a B.E. fuselage with
engine and geared-down propeller, and seating for pilot and observer,
attached to an envelope about 150 feet in length. With a speed of
between 35 and 40 miles an hour, the 'Blimp' had a cruising capacity of
about ten hours; it was fitted with wireless set, camera, machine-gun,
and bombs, and for submarine spotting and patrol work generally it
proved invaluable, though owing to low engine power and comparatively
small size, its uses were restricted to reasonably fair weather. For
work farther out at sea and in all weathers, airships known as the coast
patrol type, and more commonly as 'coastals,' were built, and later
the 'N.S.' or North Sea type, still larger and more weather-worthy,
followed. By the time the last year of the War came, Britain led the
world in the design of non-rigid and semi-rigid dirigibles. The 'S.S.'
or 'Blimp' had been improved to a speed of 50 miles an hour, carrying a
crew of three, and the endurance record for the type was 18 1/2 hours,
while one of them had reached a height of 10,000 feet. The North Sea
type of non-rigid was capable of travelling over 20 hours at full speed,
or forty hours at cruising speed, and the number of non-rigids belonging
to the British Navy exceeded that of any other country.

It was owing to the incapacity--apparent or real--of the British
military or naval designers to produce a satisfactory rigid airship that
the 'N.S.' airship was evolved. The first of this type was produced
in 1916, and on her trials she was voted an unqualified success, in
consequence of which the building of several more was pushed on. The
envelope, of 360,000 cubic feet capacity, was made on the Astra-Torres
principle of three lobes, giving a trefoil section. The ship carried
four fins, to three of which the elevator and rudder flaps were
att