Using observation data in the Fe I line, some spatial-time variations of the pressure in the solar photosphere are reproduced and local internal gravity waves are extracted through the corresponding filtration. Internal gravity waves are quasi-periodic in space (on granulation and mesogranulation scales) and time structures spreading along inclined trajectories with subsonic velocities. For the extracted wave trains, the phase and group velocities are orthogonal and their z-projections are of opposite signs.