But in 1909 there appeared a most ingeniously-constructed engine
which was destined to take a very prominent part in the progress
of aviation. This was the famous "Gnome" engine, by means of
which races almost innumerable have been won, and amazing records
established.

We have already referred to the engine shaft of the motor-car,
which is revolved by the pistons of the various fixed cylinders.
In all aeroplane engines which had appeared before the Gnome the
same principle of construction had been adopted; that is to say,
the cylinders were fixed, and the engine shaft revolved.

But in the Gnome engine the reverse order of things takes place;
the shaft is fixed, and the cylinders fly round it at a
tremendous speed. Thus the rapid whirl in the air keeps the
engine cool, and cumbersome tanks and unwieldy radiators can be
dispensed with. This arrangement enabled the engine to be made
very light and yet be of greater horse-power than that attained
by previously-existing engines.

A further very important characteristic of the rotary-cylinder
engine is that no flywheel is used; in a stationary engine it has
been found necessary to have a fly-wheel in addition to the
propeller. The rotary-cylinder engine acts as its own fly-wheel,
thus again saving considerable weight.

The new engine astonished experts when they first examined it,
and all sorts of disasters to it were predicted. It was of such
revolutionary design that wiseacres shook their heads and said
that any pilot who used it would be constantly in trouble with