A brief description is given of a vacuum distillation method which, because of the low temperatures involved, does not tend to coagulate the clay when used for concentration of dilute suspensions.

After CO2 and C are allocated to carbonates and carbonaceous matter, FeO and MgO are allocated to a hypothetical “average” chlorite of composition 12(Fe, MgO). 3Al2O3. 7SiO2. 10H2O, K2O is allocated to muscovite, remaining Al2O3 to kaolinite, remaining SiO2 to quartz, calculated hydroxyls usually agree well with H2O+. Calculated mineral analyses agree well with practical assessment and thermal expansion curves. Chlorite and chlorite-illite are known to occur (X-rays) in this series of clays.

A chloritic mineral found in close association with vermiculite from the Yoshino mine, Kochi Prefecture, agrees well with penninite but shows remarkable exfoliation on heating. Its mineralogical properties were studied by chemical, thermal and X-ray methods.

Fifty per cent. of the soils studied came from the United States and represent samples from sites in which engineering difficulties were encountered; therefore, it is significant that the clay in 50% of all soils examined was an illite-smectite type, while illite-chlorite comprised 15% of the total. For illite-smectite clays, quantitative estimation of the illite and smectite percentages is obtained from the total potash and glycol retention data. The agreement between measured and calculated cation exchange capacities is taken as supporting evidence of the reliability of the methods used. The chlorite component in the illite-chlorite clays was a high-iron chlorite. Regular and random stratification of illite and chlorite components was observed. The most important influence of composition on behaviour is the very high water sensitivity of the expansive minerals. Most of the soils studied which had caused stability or volume change problems in the field contained expansive minerals. For soils with fines of a single mineral species or a simple mixture of minerals, predictions of behaviour can be made with fair accuracy from a knowledge of soil composition. Where the soil fines are interstratified minerals or cemented crystals, predictions can seldom be made with accuracy. Interstratification or cementation usually inhibits the water sensitivity of normally expansive minerals. This fact seriously limits the value of soil compositional data to the engineer.

The clay mineralogy of the soils developed on glacial till derived from Carboniferous igneous and sedimentary rocks, and from sediments of Downtonian, Old Red Sandstone and Permian ages is compared with that of the parent rock. The results show that a definite relationship exists between the different soil types developed on the till from each parent rock, particularly in the case of the sediments. The influence of pedogenic processes on the clay mineral distributions in the soil profiles is discussed.

A study was made of five clays used for brickmaking to determine the reason why certain clays crumbled on firing. Partially weathered biotite was found to be a constituent of the clays which crumbled and the crumbling was due to this mineral exfoliating and so disrupting the bricks at a comparatively low temperature. Fresh biotite and highly weathered biotite do not have this adverse effect.

The synthesis of cobaltiferous clay minerals is described. Two methods, whereby the positioning of ions in such compounds may be adduced, are discussed. The mechanisms involved in synthesis are described.

Under certain circumstances, both glycerol and ethylene glycol form interlayer complexes with vermiculites resembling those formed with the smectites. The rate and degree of complex formation are related to the surface charge on the silicate layers, to the type of interlayer cation present and to crystal size. With glycerol, but not with ethylene glycol, the hydration state of the mineral immediately prior to complex formation is of some importance.

The adsorption of potassium by clay minerals under varying conditions of concentration and pH has been studied. It seems from the experimental data that montmorillonite shows the greatest adsorption at all pH values. The adsorption is found to vary with the concentration of potassium in the solution, pH of the solution and the nature of the cations in the exchange complex. Data are presented for kaolinite, montmorillonite, halloysite and natrolite.

The procedure used for fractionation of soils, rocks, and sedimentary materials involves separation of the clay (less than 2 microns) and silt (2 to 62 microns) by centrifugation. Randomly oriented powders and oriented aggregates of these materials are examined using X-ray diffraction as the principal method of analysis.

Certain of the criteria used for distinguishing vermiculites in clays from smectites are critically examined, and attention is drawn to the urgent need for further research in this field. Difficulties inherent in the differentiation are heightened by the common occurrence of interlayer contamination in the naturally occurring minerals.

The crystal-chemical basis of the relationship between hydrated calcium silicate and clay minerals is discussed, and a review is given of recent work on the tobermorite minerals, the group of hydrated calcium silicates which most nearly resembles the clay minerals. New data are presented for the specific gravities, refractive indices, basal spacings, and dehydration isobars of synthetic tobermorite minerals, and a tentative explanation is proposed for the variability of Ca : Si ratio in these substances.

General techniques for specimen preparation are described, including formation of supporting films and surface replicas, and methods for dispersion of clays.

Precision intensity measurements were made on 27 00l reflexions using Mo Kα radiation. The interpretation of these results leads to the location of the Al and Si atoms of the tetrahedral layer in two different planes.

Four ice advances have been recognised in East Anglia but only two of these, the Lowestoft and the Gipping, have deposited till in the Cambridge area. The clay fractions of these tills have been investigated and compared with those of the Oxford, Ampthill, Kimeridge and Gault Clays, the Lower Greensand and the Chalk, all of which outcrop in the district and could be expected to contribute material to the tills.

The value of clay mineralogical analysis as a means of measuring directions of ice-movement is critically discussed.

An outline account is given of the more important processes of weathering and soil-formation which occur on the Gipping till in the Breckland area.

A method of extruding powder specimens using a hypodermic syringe is described.

The genesis of china-clays in the neighbourhood of Guiscriff is not related to the presence of the peat which is situated on top of the clay layer in the lower parts. The formation of this peat is subsequent to the formation of china-clay. This china-clay was formed under the action of fluids of deep-seated origin of which the remains are included in the quartz veins stretching along the quarry.