SOILS FERTILIZERS. 315 



Investigations on processes of weathering, K. D. Glinka (Trav. Soc. Imp. 

 Nat. *S7. Pctcrsb., Sect. Gcnl. et Miii., Sj (1906), No. 5, pp. 1-118; abs. in Zhur. 

 Opuitn. Agron. [Russ. Jour. Expt. Landu:'\, 8 (1907), No. 5, pp. 5.'f6, 5.'/7). — This 

 treatise contains a detailed review of the literature of the subject and original 

 investigations, most of whicli have already been published by the author 

 (E. S. R., 19, p. 315). 



In the last part of this treatise he discusses the subject of types of weather- 

 ing, holding that in the future it will be possible to establish the types of 

 weathering according to the chemical processes taking place in a given case. 

 He indicates as the chief agents of weathering, carbonated water, weak salt 

 solutions, humic acids and akali liuuiates, and alkali carbonates, the partici- 

 pation of these or other agents depending mainly on the climatic conditions of 

 the locality. The chief climatic factor is moisture, hence he suggests a possible 

 soil classification based upon the degree of moisture as follows: (1) Soils with 

 optimum humidity — laterites, red earths; (2) soils with medium humidity — • 

 podzols, forest soils; (3) soils with moderate humidity — chernozems, regurs; 

 (4) soils with insufficient humidity — brown, gray, lamellar-columnar soils of 

 semideserts; (5) soils with excessive humidity — marshy, semimarshy; (6) soils 

 with temporarily excessive humidity — alkali lands. 



On the nature of clay soils according to old and recent investigations, A. 

 Atterberg (K. Landtbr. Akad. Handl. och Tidskr., Jf6 (1907), No. 6, pp. 385- 

 424; abs. in Zentbl. Agr. Chcm., 37 (1908), No. 9, pp. 579, 580).— This is a 

 critical study of different systems of classification of clays, and of our present 

 knowledge of their nature and characteristics, with an account of the author's 

 views based on original investigations. The subject is discussed under the 

 following headings: The external characteristics of clay soils; their classifica- 

 tion : is kaolin a characteristic component of clays ; the absorption phenomena ; 

 zeolitic substances as components of clay ; the properties of the colloidal 

 substances ; on the nature of the colloids ; are clay substances actual colloids ; 

 the composition of the decomposition silicates soluble in hydrochloric acid in 

 northern clays; the Russian black soils and North American soils; and com- 

 position of the difficultly soluble decomposition silicates; and the inert com- 

 ponents of clay soils. 



The author is of the opinion that kaolin is not a characteristic component of 

 clays. What has previously been taken for kaolin in northern clays is appar- 

 ently composed of fine mica particles. The most characteristic ingredients of 

 clays appear to be particles of the fineness of the colloids, while the zeolitic 

 colloids are the most important component of clays, agriculturally speaking, as 

 they are of other types of soils. The zeolites and other components soluble 

 in hydrochloric acid ("decomposition silicates") differ greatly in composition 

 according to the course of the decomposition processes under different climatic 

 conditions, the end products being either mixtures of kaolin, aluminum hy- 

 droxid, and iron oxid, or zeolite-like double silicates of aluminum and iron 

 oxids, with a high content of monoxids, besides gravel and sand. In the north- 

 ern clays kaolin and aluminum hydroxid appear to play only a minor part or no 

 part, but where kaolin and bauxite occur in quantities in the older formations 

 they may also be expected in the sedimentary clays. 



On the eolian origin of the soil salts, J. J. Pivovarov (Poclirovyedyeme 

 [PMologie^, 1906, pp. 67-80; abs. in Zhur. Opuitn. Agron. [Russ. Jour. Expt. 

 Landw.], 8 (1907), No. 5, pp. 5//7, 548). — The article gives a survey of the 

 literature of the subject in connection with the hypothesis of Vysotski concern- 

 ing the foi-mation of alkali lands. 



