In this analysis the total power input per unit volume to a soil is derived under the simplifying assumption that both the individual soil grains and the pore fluid may be considered as incompressible; the analysis is therefore applicable to saturated soils only. Since the analysis is in terms of continuum mechanics (in which the microscopically non-homogeneous soil is replaced by an equivalent homogeneous continuum) the region under consideration must be sufficiently large so that the definitions of stress, strain and porosity are meaningful. The analysis is carried out in terms of tensors, since this notation allows a convenient shorthand for the many components of the different variables. -Autho