In relation to forward-scatter propagation, expressions for the scattering cross-section and thereceived power are derived inof the quantity which is the three-dimensional Fourier transform of the correlation coefficient of the dielectric-constant fluctuation. Under the assumptionsaturation, it is shown thatthat water vapour in the tropospheric atmosphere is not in thethe dielectric constant of the tropospherecan be expresseddielectric-constantasastate offunctionof temperature alone, and consequently, the correlation coefficient offluctuation is the same as that of temperature fluctuation. therefore, obeys the -11/3-law in ·the inertial. subrange,, In the ionosphere the correlation coefficient. of dielectric-constant. fluctuationtaenacat wam山at or e}ecuon-concenuaaon nucruauon, i ne eq uanon or atauston wntcn musatisfied by the electron concentration is derived. It is shown that now obeysthe -13/3-law in the inertia( subrange.The ways of considering the effect of the dielectric-constant gradient with respect to altitude are indicated.