The results of these investigations show

1. The substances sold as “Phosphate of lime” and “Calcium Phosphas B.P.” are not pure tricalcic phosphate but are mixtures of di- and tricalcic phosphates.

2. Sodium phosphate (Na2HPO4) added to ammoniacal calcium chloride and the resulting precipitate washed with water yields a mixture of di- and tricalcic phosphate and calcium hydrate.

3. Bone ash dissolved in hydrochloric acid and precipitated with ammonia, the precipitate being well washed, yields also a mixture of di- and tricalcium phosphate and calcium hydrate.

4. When three equivalents of lime (3CaO) are made to act on one equivalent of phosphoric acid (P2O5) and the resulting precipitate removed with little delay pure tricalcium phosphate is obtained.

In the course of a general study of the chemical changes taking place in the manure heap, a number of experiments were made with the object of determining the loss of nitrogen during the aerobic fermentation of urine, straw and faeces, both separately and in various combinations. In the very first experiment with faeces, however, instead of finding a loss of nitrogen, appreciable gains were recorded, and this opened the enquiry which forms the subject of the present paper. In all the experiments a current of washed air was drawn for several hours daily through the flasks containing the substance under examination, any ammonia volatilized being retained by N/10 sulphuric acid. At the end of the experiment the total nitrogen left in the fermented substance, added to any nitrogen recovered in the wash flasks, was compared with the original total nitrogen.

1. By determination of the internal pore space in blocks of soils and comparison with the observed value for the linear shrinkage it is found that a linear relationship appears to exist between the two values.

2. By extrapolating the curve thus obtained an approximation for the limiting value of the shrinkage in the case of pure colloidal clay is arrived at amounting to approximately 23 per cent.

3. On this assumption it becomes possible to calculate the approximate content of colloidal material in any soil from a knowledge of the linear shrinkage.

4. Results are adduced, showing the values obtained for the shrinkage in the case of separated fine silt and clay fractions in the case of two soils of known shrinkage and physical composition, and compared with the values calculated from previous assumptions.

5. The results of the calculation of the content of colloidal clay in the foregoing manner in the case of 16 Leeward Islands soils are appended.

From the agricultural point of view the amount of oxygen carried into the soil as gas dissolved in rain has considerable interest. Since all the oxygen required either for the bacterial activities of the soil or for the root aeration of growing crops must first pass into the dissolved state, the supply of this essential element in a form immediately available must exercise a proportionately beneficial effect on the manufacture of plant food or on the growing crop. Recent work on the decomposition of organic matter in the soil has shown that rainfall is one of the chief factors controlling bacterial activity, but that its influence is due to something more than the supply of water. The oxygen dissolved in the rain appears to be the missing factor. As very little systematic work seems to have been done in this direction, estimations of dissolved oxygen in rain at Rothamsted were made from time to time during the year 1915.

The soils of North Wales have been studied by the writer during the past four and a half years in field and laboratory. A number of types have been recognised and studied. Further work is necessary to elucidate the properties of the types already identified and to establish fresh types. The purpose of the present paper is to give an account of the soils most typical of the area, namely the soils derived from material of the Pre-Cambrian, Cambrian, Ordovician and Silurian formations in the counties of Anglesey, Carnarvon and Denbigh. In this group are included soils derived from the weathering of local glacial drift, and the associated sandy, alluvial and peaty soils. The soils formed of newer materials, including later Palæozoic soils and Glacial drift of external origin may form the subject of a separate paper.

The biochemical decomposition of plant residues and other organic matter in the soil is of fundamental importance for soil fertility. It causes the breaking down of coarse plant fragments which otherwise might open up the soil too much: it leads to the production of colloidal complexes known as humus which exert many beneficial effects both chemical and physical, and it brings about the formation of nitrates, the most important of the nitrogenous plant nutrients.