An experimental determination of the melting of Mg0.9Fe0.1SiO3 under lower mantle conditions is presented. Samples were compressed and laser heated (Nd-YAG) in a Mao-Bell-type diamond cell. The temperature fields generated in the sample are measured using a simple tomographic technique and spectroradiometer. Mg0.9Fe0.1SiO3 in the perovskite structure melts at 3000¿300 K independently of pressure over the range of 22--65 GPa. The melting curve of Mg0.9Fe0.1SiO3 represents an experimental upper bound upon the geotherm from 700 to 1500 km. This melting curve corresponds to a homologous temperature of 0.70 or 0.85 for one- or two-layer mantle convection, respectively. This is consistent with either one- or two-layer mantle convection and a lower mantle of constant viscosity (based upon homologous temperature arguments). ¿ American Geophysical Union 1987