(1) The cotton growing area in the Gezira consists of a heavy clay soil, the proportion of clay being about 50–60 per cent. in the upper layers with a maximum at about the 4th foot.

(2) The water soluble salts amount to about 0·2 per cent. The proportion is highest at about the 3rd to 5th foot. The alkalinity (pH) is highest at the 2nd foot.

(3) In the first 2 feet, the salts consist mainly of sodium carbonate and the third and fourth of sodium sulphate.

(4) The irrigation (Blue Nile) water is of excellent quality as judged by its natural chemical composition. The concentrated water, however, contains a very high proportion of alkali salts. It is estimated that a season of normal irrigation would cause an increase of 0·01 per cent. in the alkali content of the first 4 feet of soil.

(5) The sodium salts can readily act on the clay and the sodium clay so formed hydrolyses with the formation of sodium carbonate.

(6) Samples taken at the same time from good and bad plots in the same area show a strong correlation between salt content and cropyielding power. There is also a correlation between pH and fertility.

(7) In the same season and in the same area, virgin (i.e. unirrigated) plots give a higher yield than those which have been previously under the same system of cultivation.

1. Experiments in which were measured the resistances to (a) transverse breaking, (b) crushing, and (c) parting under tensile pull of standard blocks of soil prepared in different ways and under particular moisture conditions are described and discussed.

2. The soils examined comprised three highly colloidal siliceous soils containing amounts of calcium carbonate ranging from 7·2 to 0·2 percent., and two red lateritic soils.

3. The most significant results were obtained by employing, in a special tenacity apparatus, granular test-blocks, prepared by moistening sieve-graded dry soil packed into rectangular moulds. The results thus obtained are believed to furnish a reliable measure of the cohesiveness of soil colloidal matter, especially in soil blocks that have previously been brought to constant moisture content in a humidifier. The method of preparation simulates the effect of rain in causing the “running together” of colloidal soil particles.

4. The relative cohesiveness of the soils examined appears to follow the same order as their rates of settling from aqueous suspension. This observation strengthens the view that cohesiveness in colloidal soils is to a certain extent due to chemical forces that depend on the presence of active atoms or atomic groups possessing powerful fields of residual affinity, although probably film tension also plays a part.

(1) The results of experiments on the rate of horizontal flow, and on the rate of gain in mass, or kerosene and of water in fine and crumb fractions of certain West Indian colloidal soils, comprising three siliceous soils containing different amounts of calcium carbonate, and two lateritic soils, are described and tabulated.

(2) The methods of experimentation employed were those elaborated by Green and Ampt, whose equations were found, however, not to fit the values obtained, as is to be expected.

(3) The siliceous soils examined possess relatively high swelling coefficients, and their component particles, when wetted, cohere to a greater or lesser extent, depending on lime content. These properties appear to account for the relatively low rates of permeability to water in these soils. Lateritic soils, on the other hand, possess low swelling coefficients, and low cohesiveness; water percolates through them relatively very rapidly.

An account has been given of an investigation into the changes which occur during the preservation of the oat and tare crop in the clamp silo.

The material obtained from the clamp was divisible into three types: (1) An uppermost thick layer of mouldy material. (2) “Sweet” silage from the middle layers. (3) Wet “sour” silage from the bottom layer. The spoilt material in the top layer represented approximately 19 per cent. of the whole of the crop contained in the clamp, and in addition to this, the silage was extensively spoilt round the sides of the clamp to an average depth of 12 inches. In comparing the processes of ensilage in the tower and in the clamp, it should be remembered that spoiling of this type only affects the top few inches of the material in the tower silo.

The loss of dry matter in the “sour” silage layer, arising from fermentation and drainage away of juice, amounted to more than one-fifth of the dry matter of the crop originally present in the layer. This represents a much bigger loss than any previously recorded at Cambridge in similar work with tower silos. An exceptionally heavy destruction of carbohydrates further characterised the production of the “sour” silage in the clamp.

The loss of dry matter in the “sweet” silage layer was much smaller and was comparable in magnitude with that occurring during the production of “green fruity” silage in tower silos.

The chemical characteristics of the “sour” silage samples were investigated and were found to conform with results discussed in a previous communication, namely, the samples contained a high proportion of volatile bases to amino acids, and the volatile acids were present in appreciable excess of the non-volatile organic acids.

In determining the nitrogen content of the heavy black cotton soil of the Central Provinces, India, by the Kjeldahl process it is important that the determinations be carried out on moist and not on air-dried soil. These soils apparently contain a cementing material probably containing iron which is insoluble in concentrated sulphuric acid and protects organic matter in the interior of the compound particles from the action of the acid.

It may be that these soils are peculiar in this respect, but it would seem of importance that other workers should take into account the possibility of error in the estimation of nitrogen when using air-dry soils.

In conclusion it is with great pleasure that I acknowledge my indebtedness to Mr F. J. Plymen and Dr H. E. Annett for their valuable suggestions and advice during the course of this work.

In the official methods of soil analysis followed in this country, the available phosphate is determined by Dyer's (1) method. This consists in determining the amount of phosphoric acid, which becomes soluble, when 200 gm. of soil are shaken continuously for 24 hours with 2 litres of water, containing 20 gm. of citric acid. The result is expressed as a percentage of the weight of soil. It is usual to infer lack of available phosphate if less than 0·01 per cent. P2O5 becomes soluble under these conditions. Hall (2) has suggested the necessity for a revision of this limit.

1. The exchangeable Fe, Al, Ca, Mg, K, Na have been determined in twenty soils from different parts of the East of Scotland, by extraction with N NH4Cl solution. Data on pH, “Lime Requirement” and loss on ignition are given for the sake of comparison.

2. Only three soils were found to contain Fe and Al in exchangeable form.

3. The content of exchangeable bases varies from 5·6 to 22·2 milligram-equivalents per 100 gm. air-dried soil.

4. The evidence is insufficient to deduce any definite relationship between pH and “Lime Requirement” and the pH cannot be correlated with the content of exchangeable bases except in the case of soils similar in character.

5. It is suggested that the differences in the relative proportions of the exchangeable bases indicate that there are on the one hand fundamental differences due to soil type and on the other hand fluctuating differences due to manurial treatment.

6. Emphasis is laid on the fact that the degree of saturation of a soil is not necessarily indicated by the content of exchangeable bases. At present the absorptive capacities of the soils examined are not known.

7. Until a sufficient number of soils have been examined and classified, it is unlikely that any satisfactory generalisation on the subject of exchangeable bases will be forthcoming.

1. The addition of casein to the mixed lime sulphur-lead arsenate spray causes:

(a) an increase in the amount of soluble arsenic formed on the decomposition of the spray,

(b) no change in the reactions of the polysulphide sulphur.

2. The addition of lime to the spray:

(a) decreases the formation of soluble arsenical compounds,

(b) reduces the fungicidal value of the spray owing to its reaction with the sulphur liberated from the calcium sulphide.

3. The addition of lime-casein to the mixed spray is influenced by the composition of the lime-casein.

If much free lime is present:

(a) the formation of soluble arsenic is dependent on external conditions which in certain cases tend to decrease the amount of soluble arsenic formed,

(b) the fungicidal value of the spray is reduced as in 2 (b).

If slight excess of lime is present, or if the sample has badly carbonated:

(a) the amount of soluble arsenic is increased,

(b) there is little effect on the reaction of the polysulphide sulphur.

4. The addition of gelatine to the spray:

(a) increases the formation of soluble arsenic,

(b) has no effect on the reaction of the calcium sulphide.

5. The rate of decomposition of the mixed spray is retarded by the addition of casein, lime, lime-casein and gelatine.

In a former paper (1) it was shown by solubility curves and pot experiments that the Wagner citric acid method is a satisfactory means of evaluating basic slags but is unsatisfactory for mineral phosphates.

1. A number of soils—treated with acid and washed free from it—have been found to possess in high degree the power of destroying phenol. Soils derived from certain geological formations seem to possess this property more than those derived from others.

2. This effect has been obtained from soils treated with sulphuric, hydrochloric, nitric, phosphoric, formic, and acetic acids.

3. The bulk of the loss of phenol is instantaneous; but the maximum loss is attained within about 20 hours.

4. An inverse relation seems to exist between the period of contact of acid with soil and the extent of the subsequent loss of phenol.

5. The loss of phenol is prevente d by several treatments—ignition of soil before or after acid-treatment; treatment with alkalis or sulphurous acid after acid-treatment; autoclaving the soil after acid-treatment and also in less degree before acid-treatment.

A method is described for the determination of the fluorine content of basic slag.

The fluorine content and the citric solubility of a number of basic slags are compared.

Using the conception of the “ideal soil” a calculation has been made of the cohesion due to the capillary attraction between the particles when wetted. Experimental verification of this theory is afforded by cohesion tests on the ignited silt fraction separated from soil.

1. An improved and simplified laboratory method of measuring the electrical conductivity of soils is described and measurements recorded for diverse soil samples.

2. The results for ignited soil lead to certain interesting confirmations of the capillary theory of an ideal soil.

3. The results for soils generally indicate a sufficiently simple connection between conductivity and moisture for this property to be made the basis of soil moisture determinations.

4. Certain clays were found to form a class apart, and must be regarded as exceptions to the general statement in (3) owing to the more complex nature of the moisture-conductivity relationship.