Soil resistivity is the property that defines the ability of soil to conduct current and hence whether a given soil type can be expected to provide a good or a poor ground (high or low resistance). B y contrast, earth resistance defines the relationship of a grounding electrode to its immediate environment. They are two different measurements, performed in two different ways, and expressed in two different units. R esistivity measurements are useful data for the design and installation of the electrode. The principal method for measuring resistivity is known as the Wenner M ethod and has been previously described in this series. O ther methods are also practiced in situations where Wenner is not the most suitable, and some of these will be described next.