A small-scale experimental model has been constructed for the study of steady-state slow free convection of water in saturated sand. The convection field is confined between coaxial cylinders maintained at constant temperature difference, and the upper and lower boundaries consist of planes with thermal and fluid insulation. Measurements of the temperature distribution within the convection space have been obtained for average boundary temperature differences (T1 − T0) of (I) 18·40° A, (II) 32·70° A, and (III) 46·68° A. Theoretical temperature values predicted from perturbation theory have been fitted by least squares. The first-order estimates of η/(T1 − T0), where η is the convection parameter or modified Rayleigh number, do not differ significantly from a constant value (± 3% S. D.) for the three given values of T1 − T0, indicating good agreement between theoretical and experimental results. First-order estimates are made also of the temperature coefficient of thermal conductivity b of the sand-water mixture, and of the coefficient of radiation loss c at the upper insulated boundary, but these estimates are less reliable. Separate determinations of η/(T1 − T0), b, c by direct physical measurement are in good agreement with the least-squares estimates.