he high factor of safety, which attribute has astonished
some of the foremost aviation experts in the world.

Great Britain lagged behind her Continental rivals in the development
of the Fourth Arm, especially in matters pertaining to motive power.
For some time reliance was placed upon foreign light highspeed explosion
motors, but private enterprise was encouraged, with the result that
British Motors comparing favourably in every respect with the best
productions upon the Continent are now available. Development is still
proceeding, and there is every evidence that in the near future entire
reliance will be placed upon the native motor.

Undoubtedly, as the war progresses, many valuable lessons will be
learned which will exercise an important bearing upon the design
and construction of warplanes. The ordeals to which the machines are
submitted in military duties are far more severe than any imposed by the
conditions of commerce. Accordingly there is every indication that
the conflict upon the Continent will represent a distinctive epoch in
aeroplane design and construction. Many problems still await solution,
such as the capacity to hover over a position, and it is quite possible
that these complex and baffling questions will be settled definitely
as the result of operations in the field. The aeroplane has reached a
certain stage of evolution: further progress is virtually impossible
unless something revolutionary is revealed, perfected, and brought to
the practical stage.

CHAPTER VIII. SCOUTING FROM THE SKIES

From the moment when human flight was lifted from the rut of experiment
to the field of practical application, many theories, interesting and
illuminating, concerning the utility of the Fourth Arm as a military
unit were advanced. The general consensus of expert opinion was that
the flying machine would be useful to glean information concerning the
movements of an enemy, rather than as a weapon of offence.

The war is substantiating this argument very completely. Although
bomb-dropping is practised somewhat extensively, the results achieved
are rather moral than material in their effects. Here and there
startling successes have been recorded especially upon the British side,
but these triumphs are outnumbered by the failures in this direction,
and merely serve to emphasise the views of the theorists.

The argument was also advanced that, in this particular work, the
aeroplane would prove more valuable