tinuous runs. A flywheel, weighing 23.5 lbs., was fitted to the
engine, and this, together with the ignition system, brought the weight
up to 188 lbs., giving 5.4 lbs. per horse-power. In comparison with the
engine fitted to the Wrights' aeroplane a greater power was obtained
from approximately the same cylinder volume, and an appreciable saving
in weight had also been effected. The illustration shows the arrangement
of the vertical valves at the top of the cylinder and the overhead cam
shaft, while the position of the carburettor and inlet pipes can be
also seen. The water jackets were formed by thin copper casings, each
cylinder being separate and having its independent jacket rigidly
fastened to the cylinder at the top only, thus allowing for free
expansion of the casing; the joint at the bottom end was formed by
sliding the jacket over a rubber ring. Each cylinder was bolted to the
crank-case and set out of line with the crankshaft, so that the crank
has passed over the upper dead centre by the time that the piston is at
the top of its stroke when receiving the full force of fuel explosion.
The advantage of this desaxe setting is that the pressure in the
cylinder acts on the crank-pin with a more effective leverage during
that part of the stroke when that pressure is highest, and in addition
the side pressure of the piston on the cylinder wall, due to the thrust
of the connecting rod, is reduced. Possibly the charging of the cylinder
is also more complete by this arrangement, owing to the slower movement
of the piston at the bottom of its stroke allowing time for an increased
charge of mixture to enter the cylinder.

A 60 horse-power engine was also made, having four vertical cylinders,
each with a diameter of 5.5 inches and stroke of 5.75 inches, developing
its rated power at 1,100 revolutions per minute. By accelerating up to
1,200 revolutions per minute 70 brake horsepower could be obtained, and
a maximum of 80 brake horse-power was actually attained with the type.
The flywheel, fitted as with the original 35 horse-power engine, weighed
37 lbs.; with this and with the ignition system the total weight of
the engine was only 250 lbs., or 4.2 lbs. per horse-power at the normal
rating. In this design, however, low weight in relation to power was
not the ruling factor, for Green gave more attention to reliability and
economy of fuel consumption, which latter was approximately 0.6 pint of
petrol per brake horse-power pe