SOILS — FERTILIZERS. 117 



nant factor concerned in its formation. Since tliis varies with eacli type, it 

 requires that special methods of investigation be used with each soil examined. 



The classification of mineral soils according to external characteristics, 

 A. Atterberg (pp. 284-289). — In this paper the author reports results of studies 

 on firmness and plasticity of soils. 



To determine firmness the soil was made into 2-cm. cubes, dried at 100° C, 

 and the weight required to split the cubes with a steel spatula noted. On this 

 basis the following classification is proposed: Firmness of 60 to 31 kg., clay; 

 30 to 16, strong loam ; 15 to 8, loose loam ; 7 to 0, sand. 



As only clay soils are plastic, it is proposed that plasticity be taken as the 

 dividing line between clay and loam soils. Simple methods of determining the 

 degree of plasticity are described, the plasticity being stated in terms of the 

 water content of the soil used in the plasticity test. On the basis of such tests 

 the author divides soils into highly plastic clays, medium plastic clays, and 

 slightly plastic clays. 



A tentative division of loam soils into firm and loose loams is given, the firm 

 loams being called clay loams. The sandy soils are divided into coarse sands, 

 fine sands, and silt soils. 



The firmness of clay soils is attributed to the extreme fineness of the soil 

 particles. The plasticity, on the other hand, is attributed not only to fineness 

 of particles but to their form as well. 



Concerning agrogcological mapping, K. O. Bjorlykke (pp. 290-296). — This 

 paper discusses the distinctions between geological and agrogeological soil 

 mapping as well as the present status of such work. 



The author holds that a soil survey of a region should contain a geographic 

 and orogrjiphic exposition ; a discussion of climatic relationships and of the 

 agricultural and other industries of the region ; geological observations on the 

 soil-forming rocks and the soil surface ; a description of the different soil types, 

 their physical and chemical characteristics, and their relation to cultivated 

 plants and to general vegetation ; and a discussion of the future agricultural 

 possibilities of the region. The agrogeological maps should be of two kinds, 

 (1) reconnaissance maps and (2) detail maps. The first should include district 

 maps and farm maps. 



Red soils {terra rossa), G. Murgoci (pp. 329, 330).— The author here reports 

 limite<l observations on red soils in Asia Minor. It is believetl that these soils 

 are of the same origin as the red soils of southern Eui-ope. 



The volum.etric constitution of soils (Rev. Set. [Parisi, Jf9 (1911), I, No. 5, 

 p. 150). — This article calls attention to the volumetric variation of soils con- 

 taining like proportions of plant nutrients, and emphasizes the importance of 

 some method of expressing the results of chemical analysis on the basis of vol- 

 ume as well as of weight. 



Tanks for soil investigations at the Florida Agricultural Experiment Sta- 

 tion, A. W. Blair and S. E. Collison (Jour. Indus, and Engin. Chem., 3 

 (1911), No. 1, pp. 32, 33, figs. 3; ahs. in Jour. Soc. Chem. Indus., 30 (1911), No. 

 3, p. IM, fig. 1). — This article describes a series of soil tanks used to supple- 

 ment the field work ui orange culture, to estimate accurately the loss of soluble 

 fertilizing materials in the drainage waters, and to investigate the effects of 

 long-continued use of commercial fertilizers on the soil and on the orange tree. 



Each tank has an inside diameter of 5 ft. 3i in. with a maximum depth of 

 4i ft., and a surface area of one-thousandth of an acre. The tanks are con- 

 structed of heavy galvanized iron, soldered, riveted, and painted inside and out. 

 The bottom slopes to a point near one side, where a strainer opens into a 2-in. 

 tin-lined drainage pipe a little over 4 ft. long. In each of four corners of a 



