We investigated the properties of the horizontal convective motions in the solar atmosphere using neutral iron line λ ≈ 532.42 nm profiles obtained at the solar limb with high spatial resolution. Asymmetry of the observed spectral line is studied when passing on to the limb. Space-time variations of the velocity were reproduced by the method of λ-metre. Acoustic waves were removed by k-ω filtration. The existence of convective flows of distinct scales is detected: granulation, meso- and supergranulation. Space-time distribution of convective velocity in the photosphere layers and at the heights of the lower chromosphere is analized: horizontal flows of granulation, meso- and supergranulation scales are revealed even at height h ≈ 250 km; horizontal velocities of granulation and mesogranulation increase with the height; vertical velocities of the supergranules do not change practically in the photosphere layers, whereas horizontal velocities of the supergranules can be modified with height. We revealed the asymmetry in the distribution of horizontal velocities in the large convective flows of granulation, meso- and supergranulation.