1. The changes in composition of the clay fraction in different horizons of some typical North Welsh profiles have been studied.2. The changes in the molecular ratio of silica to sesquioxides (SiO2/Al2O3+ Fe2O3) throughout a soil profile afford an indication of the nature of the eluviation which has affected the mineral portion of the soil.3. The data for North Welsh soils indicate a general tendency to enrichment of the lower layers in sesquioxides, particularly ferric oxide, at the expense of the surface layers.4. The silica-sesquioxide ratio of the clay fraction is an important aid to series definition.5. The soils of North Wales, particularly in the uplands, have probably been subjected to considerable erosion in the past. The profiles are therefore considered to be more or less truncated.
Increase atom/molecular ratio of the hydrogen discharge
