y. These are much
affected by such items as simplicity of design, strength against wear
and tear, ease of assembly and interchangeability of parts, easily
removable engines, increase in durability by the use of metal
construction for parts of the machine and the propeller, the elimination
of rubber joints, substitution of air for water cooling, facilities for
loading and unloading in a commercial machine, simple and efficient
navigational instruments and self-starter. Every improvement, however
small, will assist to reduce running costs. Then revenue must be
increased and the comfort of passengers, as, for instance, ventilation,
warmth, luggage capacity and, more than all, a reduction of noise has to
be carefully considered or they will not travel a second time by air. An
effective engine silencer is at last well on the way. It is obvious what
a great advantage this attainment will be both for service and civil
purposes. Roughly speaking, a high-powered engine without a silencer is
audible at a distance of some seven miles and at a height of 13,000 feet
at night time, though these distances are reduced by about a third by
day when normal ground noises exist. The bulk of noise is caused by the
exhaust, the propeller and mechanical noises in the engine.

I cannot leave this subject without emphasizing the value of research,
both abstract and concrete. But, though it is the keystone of progress,
its results must largely depend on the amount of flying done. It is
clear that for economic reasons new designs can only thoroughly be tried
out by commercial use, and therefore again that real progress is
dependent on commercial activity.

The advance of civil aviation is bound to be slower than was that of war
aviation. But, as war experience improved old and evolved new types, so
will peace requirements and experience shape the type and design of
aircraft and engine best suited to its purposes. Although a good deal
has under the circumstances already been achieved in peace, much remains
to be done. Gradually, however, with a modicum of research, improvements
in the factors already mentioned and the reduction of initial cost and
maintenance expenses, air transport for mails, passengers and goods will
take its place as a normal commercial public utility service, and the
increased speed of communication will assist in the general development
of trade.

AIR SERVICES: BRITISH, CONTINENTAL AND IMPERIAL.

International civil flyi