1919] SOILS FERTILIZERS. 719 



sjind and clay, and poor in fine sand, silt, and fine silt It is a loam, though a 

 heavy loam, rather than a silt soil, and is capable of assuming a very fine 

 tilth if well cultivated. These red soils are usually acid, contain very little 

 lime, and are rather deficient in phosphoric acid, and citric acid-soluble phos- 

 phoric acid is low. A very important feature of these soils is the fact that the 

 ratio of clay to fine silt is usually high, which fact, taken with others, indi- 

 cates that the soil has been in situ long enough to have weathered considerably." 



The next most characteristic soil is a gray sandy loam. " These soils have 

 been deposited from the rivers which come down from the Himalayas, and they 

 consist of coarse or tine quartz sand accompanied by a large percentage of talc 

 and potash mica. They possess fairly high percentages of phosphoric acid and 

 remarkably high figures for citric acid-soluble phosphoric acid. They are 

 rich in potash and the percentage of citric acid-soluble potash is unusually low, 

 and is often present in traces only." 



Other soils of special character are described. 



Contribution to the knowledge of the soil profile in the neig'hborhood of 

 Buitenzorg [Java], J. D. White (Meded. Landboutchoogsch. [Wageningen], 16 

 (1919), No. 3, pp. 57-88, pis. 3). — This is a report of mineralogical, physical, and 

 chemical studies of the soil profile in the vicinity of Buitenzorg in eastern 

 Java. 



This profile is divided into four layers, A, B, C, and D, of which B, C, and 

 D constitute a fossil soil of one geological origin over whicli is layer A, a 

 well-weathered brown soil of volcanic origin. Layer B-C-D is in a much 

 more advanced stage of weathering and decomposition than layer A. Both 

 layers are, however, considered to be stages of laterltic decomposition. An- 

 other layer of soil called CX is a yellow soil. This color is ascribed to 

 the presence of augite, and it is thought that this is less weathered than 

 B-C-D and more than A. It is also considered a stage of lateritic decompo- 

 sition. 



It is generally concluded from these studies that hygroscopicity is a fair 

 measure of the degree of weathering of soils of similar origin and type of 

 weathering. 



The physical texture of soils in its relation to crop production, D. Clouston 

 and A. R. Padmanabha Aiyer (Agr. Jour. India, Indian ScL Cong. No., 1918, pp. 

 89-94, Pl^- ^)- — This is a brief description of the laterite soils of the Central 

 Provinces, which contain about 69 per cent of gravel and stone and only 31 

 per cent of fine soil. It has been found that owing partially, at least, to the 

 porosity of this soil, it can be made relatively productive by irrigation, culti- 

 vation, and manuring. 



Phenomena of clay plasticity explained, R. F. Mac&Iichael {Brick and 

 Clay Rec, 55 (1919), No. 8, pp. 677-680, figs. 2).— This is a technical description 

 of the causes of plasticity in clay as well as other physical characteristics 

 of clay on the addition or expulsion of fluids, based on several years of 

 experiments. 



It has been found that the strength of clay, whether plastic, dry, or burned, 

 is due to the molecular cohesion of the clay particles themselves. Water, 

 when added to a mass of dry clay, produces a disruptive force within the 

 mass, opposing cohesion and reducing the strength of the clay. Plasticity 

 results from a balancing of the forces of coliesion and disruption. Fluids 

 other than water may be used to produce plasticity in clay. Organic matter, 

 soluble salts, and colloids, except as the latter are considered to be merely 

 very fine, insoluble particles of the clay itself, are not essential to plasticity. 

 Shrinkage is considered to be merely a rearrangement of the clay grains. 



