ABSTRACT
The expectations of theory colour perception to such a degree that new notions seldom arise from facts collected under the influence of old pictures of the world. New pictures cast their influence before facts can be seen in different perspective. Weathering is that part of epimorphism dealing with the breakdown of minerals. The dominant factor in such breakdown is the hydrogen-ion concentration of the solution in contact with the minerals, for this is responsible for hydrolysis, the most important of the processes whereby silicates are weathered. The main source of hydrogen ions results from the reaction between atmospheric carbon dioxide and water to produce carbonic acid, which ionizes to form bicarbonate and hydrogen ions. In overall terms the process of leaching is responsible for the segregation of the more mobile elements (K, Na, Ca and Mg) from the less mobile (Fe and Al) with silicon occupying a somewhat intermediate position. Biospheric reactions, however, can profoundly alter the whole situation.
