may differ markedly from the problems of surface measurement. For example; for any instrument used on a floating balloon, some consideration must be given to the effect of solar radiation on its behavior. As mentioned in the discussion of the automatic ballast valve, this effect is especially important in the action of any aneroid or other capsule which is not completely temperature compensated. Since the floating balloon will remain within one parcel of air, rising and falling and moving sidewise as the air does, temperature extremes will result from radiation effects and lack of ventilation. One investigator has estimated that the temperatures to be experienced by such a body range from $ - 6 0^{\circ} \mathrm{C} $ after a night of radiation to a maximum of $ + 5 0^{\circ} \mathrm{C} $ in direct sunlight. Two ways of partially circumventing the undesirable results of this feature are:
1. Temperature compensation of the pressure capsule for some pre-set pressure. This compensation is only complete at one pressure. $ ^{5} $
2. A second method of reducing insolation effects is the use of highly reflective shields.
The methods of height determination used so far are not completely satisfactory. Pressure-heights have been obtained by 72 mc. and 397 mc. radiosonde transmitters with long-life battery packs. Difficulties have been experienced in all long flights due to:
1. Signals being lost due to excessive range or to power failure.
2. When the balloon begins to float and height oscillations result from the action of the automatic ballast valve, it is impossible to identify the radiosonde contact (hence the pressure) using the conventional baroswitch of the Diamond-Hinman type radiosonde. These steps are now being taken to improve height measurements:
1. The addition to the flight train of a light-weight barograph.