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The signals from the Post Office sender GBR at Rugby on a frequency of 16 kc/s (wavelength 19 km) were received at a distance of about 100 km at two sites whose distance apart was, on one occasion, 15 km, and on another occasion 40 km. Examination of the fading records of the amplitude of the wave reflected from the ionosphere showed that it consisted of a steady component on which was superimposed a randomly varying component. The correlation between records at two points 15 km apart was about 0.8, and at 40 km was 0.35. The time variations of the random component could have been produced by reflection from scattering centres in the ionosphere which moved with random velocities having an r.m.s. value of about 8 m/s in the line of sight, or which drifted steadily with a velocity of about 100 m/s in a direction predominantly east-west.