Professor James (Jim) Quirk is distinguished for his studies of the properties of soil which are determined by the presence of constituents of colloidal dimensions such as the clay minerals and certain metallic oxides. The properties which are of particular importance include aggregation, porosity, and permeability, and ionic absorption, desorption and exchange. He has paid special attention to the micro-crystalline structure of the clay minerals in so far as these have been revealed by absorption phenomena. Of particular interest has been the recognition of "domains" in these micro-structures. These concepts have been extended to the soil-plant root interface with reference to the movement of nutrients from the soil to the plant. His work is characterised by the use of modern theoretical and practical tools of research.