This investigation deals with the determination of certain direct-current electrical properties and thermal properties of porous non-metallic materials and the correlation between the electrical and thermal conductivity of such materials;Although considerable work has been done in the measurement of electrical and thermal properties of many materials, little has been done in connection with porous ceramic materials;The correlation of electrical and thermal conductivity on the basis of a constant ratio has been attempted many times and has been found to be generally possible for pure metals and some alloys. However no definite explanation has been given for the lack of proportionality of these properties for non-metals;It is the purpose of this study to determine and explain the manner of variation of certain of these properties and to determine and explain the relation existing between thermal and electrical conductivity;The electrical conductivities of porous ceramic materials were measured and compared an the basis of porosity. The graphical representation of the variation resembled approximately an equilateral hyperbola;The conductivity is made up of two components, electronic and ionic conductivity. The first of these is very small since few free electrons are present in non-metallic materials. The contribution of electronic flow to the total conduction current may be shown to vary as an inverse function of the first power of the porosity. The fact that the voltage gradient necessarily adjusts itself to produce uniform current flow through the material makes no difference in the electronic component of conductivity since such a voltage gradient change does not alter the electronic resistance of either material, the constancy of which is the basis for the derivation of the hyperbolic relationship;Ionic conduction in this case involves the production of ions by collision. Since the current flow resulting from the motion of these ions is not proportional to the voltage, any change in the voltage gradient produces a corresponding change in the component resistances of the materials in the specimen. That the relation between ionic conductivity and porosity may be represented by a curve steeper than the hyperbolic function may be shown;As the conductivity, by the theorem of superposition, is the direct sum of the ionic and electronic components of conductivity, the total conductivity may be shown to vary as an inverse function of the porosity raised to some power higher than one;The shape of the current-voltage curves for the materials indicated that the ionic conductivity was predominate as assumed in the analysis. That the shape of the conductivity-porosity curve was independent of the applied voltage was evident from the fact that the currents for any two materials were approximately proportional at any voltage.