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In May 1950 the writer received from Mr. Henry Burgess, of Spiggie, Shetland Isles, a specimen of a material which had been found by a local quarryman. The property of the material which had particularly attracted attention was that when it absorbed water it became soft and pliable and looked like wet leather. The specimen, measuring approximately 4x2X1 inches, had a brownish iron-stained outer skin, and showed slight signs of foliation parallel to its length. Internally it consisted of a white to greyish-white compact material, in which were embedded portions of the syenitie country-rock. This white material has been shown to consist dominantly of the mineral palygorskite (attapulgite).

Synopsis On examination, two samples of clay from Keuper marls have been found to contain a chloritic mineral showing a limited c-axis expansion on glycerol treatment. One of these samples gives the same (001) spacing as montmorillonoids when treated with glycerol, and a heating test is necemary to make the distinction. Après examen de deux èchantillons d'argile des marues Keuper on a trouvè qu'ils contiennent un minèral chloritique qui montre une dilatation limitèe de l'axe c après traitement par le glycèrol. Un de ces èhantillons donne le mème espacement (001) que les montmorillonoides après traitement par le glycèro1, et un essai par le chauffage est nècessaire pour faire la distinction.

Field investigation of the origin and development of three brown-earth (sol Zessiwk) profiles has been supplemented by mechanical and mineralogical analyses and micromorphological studies. Two profiles, representative of the Batcombe and Winchester series, were on Clay-with-flints and the third, of the Charity series, on a Coombe deposit.Particle-size distribution and petrographic data strongly suggest that all three soils are derived in part from loess. The Charity is interpreted as an autochthonous profile formed in a Head deposit composed of chalky and flinty detritus mixed with loess by soliflwion, whereas the Batcombe and Winchester are twostage profiles, formed in composite (non-uniform) parent materials resulting from the superficial incorporation of loess with the truncated or redeposited remains of previously weathered horizons with rotlehm and/or braunlehm fabrics. These Clay-with-flint substrata contain materials derived from Chalk and Eocene beds in varying proportions, weathered in Tertiary or interglacial periods and rearranged by periglacial agencies. Clay-with-flints sensu stricto, as represented in the Winchester subsoil, has distinctive physical, mineralogical, and micromorphological characteristics, and appears to have originated by sub-surface solution of the Chalk and illuvial accumulation of clay derived for the most part from overlying deposits.The land surfaces concerned have probably been subjected to at least one alternation of periglacial and temperate conditions after the addition of loess. Hence the extent to which either profile reflects the influence of the contemporary environment is not readily assessed, but evidence is adduced that the upper horizons of each profile bear the impress of similar pedogenic processes, including eluviation of clay-size material and acidic weathering leading to the accumulation of vermiculite, modified in the Winchester by the effects of erosion and soil creep. (1949), the major group of brown earths or brown forest soils comprises well-drained and moderately well-drained acid mull soils, occurring naturally under deciduous forest, and characterized by brown, friable, sub-surface horizons which are leached of carbonates and show little or no differential eluviation of sesquioxides. This group includes braunerde Kubiena, 19 ) or sols bruns acides relatively young land surfaces on silicate rocks or their clastic derivatives, to ether with texturally differentiated profiles conformin ABC profiles typical of grey-brown podzolic soils or parabraunerde (Tavernier and Smith, 1957; Kubiena, 1956a) but those associated with Clay-with-flints and other high-level deposits normally have thick, intensively weathered subsoils, resembling those of red-yellow odzolic soils, within which no well defined B and C horizons can ge identified. In general, on upland surfaces little affected by recent * Present address : AS defined by Robinson

Summary A series of soils from two areas of Tanganyika have been studied mineralogically. They are derived in the main from amphibolite, but only a small proportion of the more resistant ahminosilicate minerals survive in the soil. The clays (<1.4μ) of the red loams are characterized by a predominance of kaolinite, whereas the more poorly drained grey soils have a disordered kaolin. Other components of the clays are iron oxides and small amounts of illite. The pallid soils contain moderate amounts of montmorillonite in the weathering zone, some of which persists into the soil. The mbuga and black valley soils contain montmorillonite or iliite, with subordinate kaolin.