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.