The safety of the machine and the reliability of an air service largely depend on accurate weather forecasts. In order to co-ordinate the meteorological work of the country as a whole, and for the special assistance of aviation, the Meteorological Services of Great Britain have been amalgamated under the Department of Civil Aviation, and, working in close co-operation with the Communications Branch of the Department, have made improvements in the rapid collection and distribution of meteorological information for all purposes. 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.