214 EXPEKIMENT STATION RECORD. 



relation to climate, vegetation, and soil formation. Analyses of some of the 

 soils of these regions show large quantities of gypsum, less sodium sulphate, 

 and some sodium chlorid. The quantity of sodium sulphate is said to be 

 sufficient to limit the vegetation to desert plants. An abundance of gypsum is 

 observed principally where excess moisture is contained in the soil. For this 

 reason the salt deposits are said to be due to the evaporation of atmospheric 

 water and not to subterranean waters, although the formation of underlying 

 salt crusts under the influence of subterranean waters is frequent. 



Tamar River soils, H. J. Colbourn iAg?\ and Stock Dept. Tasmania, Rpt. 

 1912-13, pp. 18, 19). — ^Analyses of basaltic and nonbasaltic soils from the Tamar 

 River Valley are reported with brief comments on their fertilizer needs. 



Soil formation in clays of humid regions, B. Frosterus (Intcrnat. Mitt. 

 BodenJc., 3 {1913), Xo. 2-3, pp. 99-130, figs, ii).— Investigations of the physical 

 and chemical composition of podzol soils found in clay soil deposits in swampy 

 regions are reported. These included a study and comparison of the different 

 layers of these soils and the conditions which determine their character. 



It was found that in many cases two genetically different divisions exist in 

 podzol soils, an upper and a lower. The upper part, which may be considered 

 the podzol proper, is divided into two zones, one composed of layers of humus 

 and of liaolin, the other composed of sedimentary earth and ortstein (hardpan) 

 formations. These layers are formed by the leaching down of the soils from 

 above. The kaolin layer is in an advanced state of weathering and is charac- 

 terized by a high silica content. The layers of the second zone are especially 

 rich in humus, clay and iron, and leachings of magnesia and alkalis. 



The location and condition of the lower part of the podzol soil is determined 

 by the ground-water level, and in some cases this influence extends to the sur- 

 face soil, giving rise to the so-called ground-water soils. In localities where the 

 ground-water level is high and where forest swamps are common such soils 

 take an important place, replacing the true podzol soils. Where they lie near 

 the surface they exercise a bad influence on plant growth. The true podzol 

 formation is directly opposed to the ground-water soil formation. 



The constituents of clay which impart plasticity and cohesion, A. Atter- 

 liERG {Inteniat. Mitt. Bodenlc, 3 {1913), No. 4, pp. 291-330, figs. 2).— In a report 

 of extensive investigations of the causes of plasticity, toughness, and firmness 

 of clays of northern and southern Europe the author defines plasticity, con- 

 sistency, and stickiness as applied to clay, reviews the investigations and con- 

 clusions of other experimenters, and reports the results of his own tests of a 

 large number of mineral samples and chemical preparations made to determine 

 the principal plastic constituents in these clays. The minerals biotite, hematite, 

 and limonite, and mixtures of hematite or limonite with kaolin showed typical 

 clay plasticity combined with a high degree of toughness, as did also ferric 

 oxychlorid (dialyzed iron). 



Those minerals and preparations which appeared plastic showed a leafy or 

 scaly structure from which it is concluded that the particles of leafy or scaly 

 form impart plasticity to a mineral. A high degree of toughness was found in 

 washed products of biotite, hematite, and limonite, as was also a high degree 

 of firmness on drying in fine washed products out of the same materials. Since 

 firmness was not found in all of these products it is concluded that a high degree 

 of firmness is a property only of the scaly shaped particles of colloidal size. 



Since the clays of northern Europe contain biotite in both oxidized and 

 unchanged form it is generally concluded that colloidal biotite washings form 

 their chief constituent and explain their high plasticity. The clays of southern 

 Europe apparently owe their plasticity to their high content of hematite and 

 limonite and mixed hematite or limonite with kaolin. 



