The total and external surface areas of nineteen British clay soils were determined from measurements of their water and nitrogen adsorption respectively. In addition, four physical and chemical properties of these soils were determined ; liquid limit, plastic limit, cation exchange capacity, and clay content.The correlation between these six measured properties was examined. Total surface-area, liquid limit, and cation exchange capacity, had correlation coefficients of 0.90 or greater. This is sufficiently high to enable an indication of these three properties to be obtained from measurements of any one of them.The correlation between these three properties and the rest was slightly lower for the plastic limit, and considerably lower for the clay content and external surface-area, although all were significant at the 5 per cent level.

A procedure for calculating both the external and total areas of soil particles from the relation between vapour pressure and moisture content is tested experimentally for four British clay soils. The calculated surface areas are compared with those obtained by the standard procedure from measurements using both water vapour and nitrogen, and their relation with the mineralogy of the clay fraction of the soil (as determined by X-ray analysis) is examined. It is concluded that this new method is sufficiently accurate to be used as an indication of the clay mineralogy.

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Synopsis Laboratory studies have shown that a red clay soil from Nyeri, Kenya, (which occurred immediately beneath the top soil and was seasonally air dried in situ) possessed unusual properties, including an excessively high moisture sorption, increase in index values with prolonged mixing and abnormally low optimum dry density for B.S. compaction. The explanation of these properties is shown in this Paper to lie in the mineralogy and structure of the soil, and by use of colour studies it is shown that the meta-halloysite and quartz in the soil are coated overall and cemented with haematite. In the Appendix, brief consideration is given to a mechanism of formation of the red clay soil from basalt, and it is shown that this mechanism is consistent with the known geological estimates of the age of the soil. Des études de laboratoire ont montré qu'un sol d'argile rouge de Nyeri, Kenya (qui se trouvait immédiatement au-dessous du sol supérieur et était séche à l'air et sur place pendant la saison), possédait des propriétés peu communes, comprenant une absorption excessivement élevée d'humidité, augmentation des valeurs d'index avec mélange prolongé et densité sèche optimum anormalement basse pour compacité B.S. L'explication de ces propriétés est indiquée dans cette communication comme due à la minéralogie et structure du sol, ct par l'emploi d'études de couleurs on a démontré que le métahalloysite et le quartz dans le sol sont complètement recouverts et cémentés avec de l'hématitc. Dans l'appendice, une considération brève est donnée à un mécanisme de formation du sol d'argile rouge provenant du basalte, et il est démontré que ce mécanisme est consistant avec les estimations géelogiques connues de l'âge du sol.