Photospheric brightness fluctuations were recorded photoelectrically across a part of the sun near the center of the disk, and simultaneously for two regions of the continuous spectrum chosen at various wavelengths between 23500 ~ and ).5500 ~.
The auto-correlation functions and spatial power spectra were derived for each recording, and the cross-correlation functions, spatial relative phase and coherence spectra were computed for each pair of recordings. The main results are:
(1) The cross-correlation between any two recordings obtained for various regions of the continuous spectrum, is a function of the wavelength distance 32 between these regions. The decrease of the cross-correlation with increasing 32 is due to the fact that separate photometric inhomogeneities radiate in limited spectral ranges.
(2) A constant relative displacement of the location of the brightness fluctuations in two different regions of the continuum, expressed in an asymmetry of cross-correlation function, is observed. On the average, the "violet" inhomogeneities are displaced to the west relatively to "yellow" ones in all fifteen cases investigated.
(3) The correlation radius depends on the wavelength and increases by a factor 3 to 4 from 25400/~ to 23500/~.
(4) Sometimes a periodic systematic component in the auto-correlation and cross-correlation functions is observed. This component seems to be caused by supergranulation. For 16 long recordings the wavelength A0 of this component has a mean value of (22 4-6).103 km and does not show any clear dependence on 2.