on is at the rate
of 3.6 gallons per hour, which corresponds to an endurance of 16 1/2
hours.

With the engine running at 1,800 revolutions, a speed of 50.6 miles per
hour has been reached by one of these ships, but actually very few
attained a greater speed than 40 miles per hour.

The envelopes of S.S. airships are composed of rubber-proofed fabric,
two fabrics being used with rubber interposed between and also on the
inner or gas surface. To render them completely gastight and as
impervious to the action of the weather, sun, etc., as possible, five
coats of dope are applied externally, two coats of Delta dope, two of
aluminium dope and one of aluminium varnish applied in that order.

One ripping panel is fitted, which is situated on the top of the
envelope towards the nose. It has a length of 14 feet 5 inches and a
breadth of about 8 inches. The actual fabric which has to be torn away
overlaps the edge of the opening on each side. This overlap is sewn
and taped on to the envelope and forms a seam as strong and gastight as
any other portion of the envelope. Stuck on this fabric is a length of
biased fabric 8 1/4 inches wide. These two strips overlap the opening
at the forward end by about three feet. At this end the two strips are
loose and have a toggle inserted at the end to which the ripping cord
is tied. The ripping cord is operated from the car. It is led aft from
the ripping panel to a pulley fixed centrally over the centre of the
car, from the pulley the cord passes round the side of the envelope and
through a gland immediately below the pulley.

The nose of the envelope is stiffened to prevent it blowing in. For
this purpose 24 canes are fitted in fabric pockets around the nose and
meet at a point 2 1/4 inches in front of the nose. An aluminium
conical cap is fitted over the canes and a fabric nose cap over the
whole.

Two ballonets are provided, one forward and one aft, the capacity of
each being 6,375 cubic feet. The supply of air for filling these is
taken from the propeller draught by a slanting aluminium tube to the
underside of the envelope, where it meets a longitudinal fabric hose
which connects the two ballonet air inlets. Non-return fabric valves
known as crab-pots are fitted in this fabric hose on either side of
their junction with the air scoop. Two automatic air valves are fitted
to the underside of the envelope, one for each ballonet. The air
pressure tends to open the valve ins