It is indeed a privilege to be asked to deliver this, the Second Lecture inaugurated by the Royal Aeronautical Society as “ The British Commonwealth and Empire Lecture.” I feel particularly gratified at being asked to follow in the wake of so distinguished a pioneer in Commonwealth Civil Aviation as Mr. Hudson Fysh, who delivered the Lecture last year. I am, however, at the same time distressed by the sequence, because after reading the outline of experience and achievement which was presented in such graphic form by Mr. Hudson Fysh, I realise acutely that I cannot offer you anything comparable. There can be from myself no first-hand account of pioneering or achievement, neither am I a competent spokesman for any of the organisations which have played so great a part in building up the British contribution to world aviation.

The regular operating heights of aircraft, both civil and military, are continually increasing until now regular flights within the stratosphere are planned. There is, therefore, much practical interest in the meteorological conditions to be found in the stratosphere and upper troposphere. For about half a century meteorologists have been sending up small balloons carrying recording instruments which measure the temperature and pressure at heights up to 60,000 ft. or more, while recently radio transmitters have been incorporated in the instruments which transmit the temperature and the pressure to the ground station. By following the path of the balloon either by sight or by radio direction-finding, the velocity and direction of the wind at the various heights can also be found. From measurements made in these ways meteorologists have for many years known the general distribution of temperature and winds up to great heights.