a single engine of 250 horsepower. With this the
vessel reached the contract speed of 45 miles per hour with a cruising
radius of 18 hours, equivalent to 800 miles when the engines were
running at full speed. The vessel served admirably as a training
airship, for, by the time she was completed, the No. 23 class of rigid
airship had come to being, and thus No. 9 was already out of date.

Three of the 23 class were completed by the end of 1917; it was
stipulated that they should be built with a speed of at least 55 miles
per hour, a minimum disposable lift of 8 tons, and a capability of
rising at an average rate of not less than 1,000 feet per minute to a
height of 3,000 feet. The motive power consisted of four 250 horse-power
Rolls-Royce engines, one in each of the forward and after cars and two
in a centre car. Four-bladed propellers were used throughout the ship.

A 23X type followed on the 23 class, but by the time two ships had been
completed, this was practically obsolete. The No. 31 class followed the
23X; it was built on Schutte-Lanz lines, 615 feet in length, 66 feet
diameter, and a million and a half cubic feet capacity. The hull was
similar to the later types of Zeppelin in shape, with a tapering stern
and a bluff, rounded bow. Five cars each carrying a 250 horse-power
Rolls-Royce engine, driving a single fixed propeller, were fitted, and
on her trials R.31 performed well, especially in the matter of speed.
But the experiment of constructing in wood in the Schutte-Lanz way
adopted with this vessel resulted in failure eventually, and the type
was abandoned.

Meanwhile, Germany had been pushing forward Zeppelin design
and straining every nerve in the improvement of rigid dirigible
construction, until L.33 was evolved; she was generally known as
a super-Zeppelin, and on September 24th, 1916, six weeks after her
launching, she was damaged by gun-fire in a raid over London, being
eventually compelled to come to earth at Little Wigborough in Essex. The
crew gave themselves up after having set fire to the ship, and though
the fabric was totally destroyed, the structure of the hull remained
intact, so that just as Germany was able to evolve the Gotha bomber from
the Handley-Page delivered at Lille, British naval constructors were able
to evolve the R.33 type of airship from the Zeppelin framework delivered
at Little Wigborough. Two vessels, R.33 and R.34, were laid down for
completion; three others were also put dow