 Although it is now recognized that precise determination of cohesion is impossible because formula_1 is not a fundamental soil property, the Mohr-Coulomb theory is still used in practice today.In the 19th century Henry Darcy developed what is now known as Darcy's Law describing the flow of fluids in porous media.Joseph Boussinesq (a mathematician and physicist) developed theories of stress distribution in elastic solids that proved useful for estimating stresses at depth in the ground; William Rankine, an engineer and physicist, developed an alternative to Coulomb's earth pressure theory.