The electrical conductivity of a partial melt is influenced by many factors, including melt conductivity, crystalline conductivity, and melt fraction, each of which is influenced by temperature. We have performed measurements of bulk conductivity as a function of temperature of an Fo80-basalt partial melt between 684¿ and 1244 ¿C at controlled oxygen fugacity. Melt fraction and composition variations with temperature calculated using MELTS indicate that the effect on melt conductivity of changing melt composition is balanced by changes in temperature (T). Thus bulk conductivity as a function of T or melt fraction in this system can be calculated assuming a constant melt conductivity. The bulk conductivity is well modeled by simple parallel calculations, by the Hashin-Shtrikman upper bound, or by Archie's law (&sgr;partial melt/&sgr;melt=C1Xmn). We estimate apparent values of the Archie's law parameters between 1150¿ and 1244 ¿C as C1=0.73¿0.02 and n=0.98¿0.01. Estimates of the permeability of the system are obtained by using an electrical conductivity-critical scale length relationship and range from ~10-14 to 10-18 m2, comparing favorably with previously published values. ¿ 1999 American Geophysical Union