The fractional convective flux nFc(xc)/zcF is computed for the effective level Xc =logrc =0.125, using bi-dimensional co-spectra for relative continuum-brightness fluctuations AI and radial velocity fluctuations A V measured for the C I 5052.16 spectral line. A more uncertain flux for xre ~-0.9 is obtained for the Fe I 5049.83 line. Since the results (Figure 1) incorporate current uncertainties in RMS~I, RMSav and RMSAT(X), where AT are photospheric temperature fluctuations, they must be considered qualitative until these uncertainties are appreciably reduced. The requirement that the fractional convective flux < 1, places restrictions on these uncertainties which suggest that current RMSa 7" (x)'s are too large.
The results confirm the importance of overshoot at the top of the solar hydrogen convection zone and suggest a non-negligible fractional convective flux throughout the lower photosphere. Qualitatively, they do not agree with the predictions of the generally-used, local, mixing-length theory or those of Parsons' (1969) modified mixing-length theory. However, qualitative agreement with the predictions of the non-local, generalized mixing-length theory of Spiegel ( 1963) and with the nonlocal theory of Ulrich (1970) cannot be considered as observational confirmation of these theories.