Previous methods of atmospheric exploration by radio-sounding balloons are reviewed. Arrangements involving radio frequency variations are unlikely to be satisfactory due to the wide frequency band required and the possibility of appreciable interference. In the original method described, a signal of fixed radio frequency is employed, and each meteorological instrument produces a continuous variation of modulation frequency. The pressure- and temp-measuring instruments are arranged to produce variation of modulation frequency without mechanical linkages. The cost of the apparatus is said to be comparatively low, and reproduction in large quantities possible. The results from a number of exptl. ascents are analyzed as showing great reliability and accuracy. Observation of pressure and temperature up to [plus or minus] 10 km. altitude is obtained, the accuracy of these determinations being [plus or minus] 5 mb. and 1[degree] C, respectively.