Distinguished mainly for his work on the movement of water through porous media, notably soils, where he has led in the subjection to systematic analysis of a complex and hitherto poorlyunderstood set of phenomena. Problems treated comprehensively have been the infiltration of water into an unsaturated medium and the general phenomena of diffusion where the diffusivity is concentration-dependent. He developed the treatment of movement in vapour form between the inter-granular menisci including the influence of a temperature gradient, and hence the evaporation from non-saturated soils. His considerable versatility and originality have provided other miscellaneous contributions of merit in the borderline fields of hydrology, meteorology, and ecology. Basic analyses of the physics of water in plants, and through the soil - plant - atmosphere continuum, have had impact on the understanding of plant-water physiology.
