318 EXPERIMENT STATION EECORD. 



lion to determine the effect of glaciatiou on agriculture in certain typical dis- 

 tricts along the glacial boundary in Ohio showed that " while the ice sheet did 

 not materially affect the fertility of the soil ... it was of great economic im- 

 portance in making more of the land available for profitable cultivation." 



Studies on the change of the soil surface, R. Hoffman x {Landw. Vers. 

 Stat., 85 {I'JlJf), No. 1-2, pp. i23-i^7).— Studies on the effects of freezing and 

 fertilization on the total surface area of different soils, as determined by the 

 Itodevvald and Mitscherlich hygroscopicity method, are reported. 



No variation in the surface area of six different surface soils due to freezing 

 could be detected, and it is concluded that, as the effect of each successive freez- 

 ing on surface soil steadily decreases, the actual effect of frost on the soil sur- 

 face approaches a maximum value in approximately an asymtotic manner. It 

 was further found that the quantities of organic and inorganic fertilizers which 

 are used in practice effect no important or lasting change in soil surface. Ap- 

 parently the mass of irreversible colloids of surface soils is so reduced by freez- 

 ing and drying that the hygroscopicity values of the remaining irreversible 

 colloids are fully covered by the hygroscopicity values of the other soil 

 constituents. 



The action of hydroxyl ions on clay and clay soils, P. EouLA^'D (Landic. 

 Vers. Stat., 85 (1914), No. 1-2, pp. 105-108) .—The author defends his views set 

 forth in a previous note (E. S. R., 30, p. 23) as attacked by Maschhaupt (E. S. R., 

 31, p. 216) and maintains that the flocculation of colloids in clay soils is caused 

 by the hydroxyl ions of calcium and other hydroxids. See also a related note 

 by Wiegner (E. S. R., 31, p. 618). 



The colloids of clay and humus soils, P. Rohland (Xaturw. Ztschr. Foist u. 

 Landw., 12 (1914), No. 8, pp. 380-385). — In a further discussion of the subject 

 (E. S. R., 30, p. 718; 31, p. 514) the author points out that in the colorometric 

 method for determining colloids a relation exists between absorption and the 

 composition and reaction of the coloring matter used. He reviews experiments 

 with different soils which indicate that the absorptive power of soil colloids 

 for water steadily decreases after repeated drying. He also discusses the 

 importance of colloidal content in determining plasticity and similar properties 

 of soils. 



The adsorptive power of soil colloids, P. Rohland (Monatsh. Landw., 7 

 (1914), ^0. 7, pp. 159-165). — The author discusses the properties of soil colloids 

 along the same lines as in the above and previous articles. 



The colloidal properties of red soils, P. Rohland (Kolloid Ztschr., 15 (1914), 

 No. 2, pp. 96-98). — ^The author reviews investigations by himself and others 

 which in his opinion prove that the chai'acteristic properties of red soils are 

 due to silicates of a strongly colloidal nature and that these colloidal properties 

 are very important agriculturally. 



Colloidal properties of the acid soils of Japan, T. Tadokobo (Jour. Col. Agr. 

 Tohoku Imp. Univ., 6 (1914), No. 2, pp. 27-50, pis. S).— Studies of the colloidal 

 properties of certain of the acid soils of Japan, with particular reference to 

 swelling on contact with water or salt solutions, the development of heat 

 accompanying swelling, hygroscopicity, physical adsorption, and absorption of 

 ammonia are reported. 



The degree of swelling of a soil was found to vary with the type of reagent 

 used, indicating the formation of different gel forms with different reagents, 

 and that the gel forming materials, particularly in acid soils poor in humus, do 

 not x'epresent individual substances. The small difference in increased volume 

 found between the original humus-poor soil and the residue extracted with 

 water was taken to indicate that colloidal substances extracted from such soils 

 with pure water have no important connection with the swelling of the soil. 



