In the course of a fixed‐frequency ionospheric study, employing a pulse‐triggered transmitter operating on 3.5 Mc/s and three spaced‐receivers, the transmission delay was continuously recorded. Aside from a vertical‐incidence transmission, two oblique transmissions were thus available with 62 and 109 km as base lines, the latter being correspondingly oriented in an approximate west‐east and northwest‐southeast direction.An analysis of the echoes from theF‐region was made for the period between August 1952 and December 1953. Successive irregularities observed simultaneously on three records displayed frequently consistent time‐displacements. Assuming the midpoints of the transmissions to be characteristic and preferred areas for the reflection of the h.f.‐pulses, the time‐displacements were interpreted as being due to a mechanical motion of theF‐region. Direction and speed of this movement were thus obtained, and semiannual and annual periods of these compo