ses. In
addition to the forecasts issued four times daily, collective reports
are issued hourly by wireless from the London terminal aerodrome at
Croydon and copies are distributed to transport companies and others
concerned.

A feature of meteorology which is often overlooked is its economic
value. By making use of a knowledge of the wind at different heights,
aircraft can complete journeys more quickly than would otherwise be
possible, and thereby save their own fuel and their passengers' time.
This will be specially useful in the tropics where the regularity of the
surface winds has its counterpart in the upper air, but even in Europe
time-tables can be drawn up with due attention to the favourable and
unfavourable effect of prevailing winds. The planning of airship routes
in particular, must be considered in close connection with this aspect
of weather conditions.

To-day, however, the aeroplane may be considered as an "all-weather"
craft, save for mist and fog--the enemies of all transport and
particularly to that of the air--to which unfortunately England is
particularly liable during the winter. Experiments have been carried out
on the dispersal of fog, the illumination of aerodromes by fog-piercing
lights, and instruments to record the exact position of the aeroplane
and its height above the ground, but success has not yet been achieved.

Similar to the problems of flying and landing in mist and fog is that of
night flying. Until night flying is practicable, only half the value of
the aeroplane's speed is obtainable, since other transport services run
continuously day and night. Further, as machines become rapidly obsolete
owing to technical progress, it is essential that they should be in use
for the greatest number of hours during their life. Much has been done
in the lighting and marking of aerodromes and in the equipment of
aeroplanes with wireless telephone and direction-finding apparatus.

It may here be mentioned that there are two methods of obtaining the
position of aircraft by means of wireless telegraphy, known as
direction-finding and position-finding. Direction-finding is effected by
means of two coils set at right angles in the aircraft, by means of
which the bearing of a transmitting ground station with reference to the
aircraft's compass can be taken. When two or more bearings on different
ground stations, whose position is known, have been obtained, a "cut" or
"fix" of the aircraft is obtain