SOILS FERTILIZERS. 513 



Society in which the author discusses the influence of the chemical composition, 

 humus content, and physical properties of the soil on the character of its vege- 

 tation. Particular attention is given to the geological formation of different 

 rocks and their subsequent decomposition and soil formation through the action 

 of weathering agents, with special reference to the soils of northern Germany. 



The author emphasizes the fact that it is exceedingly difficult, or even impos- 

 sible, to draw definite conclusions regarding the final soil product from a knowl- 

 edge of the parent rock alone. The position is therefore taken that geological 

 agronomical maps are of great practical importance in fruit growing as well as 

 in all kinds of farming in that they deal not only with the geological aspect of 

 the soil but also with its physical and chemical properties and plant adaptations. 



Some of the more important soil maps applicable to Germany are briefly 

 noted. 



The mechanical analysis of arid soils, W. Beam (Cairo Sci. Jour., 5 (1911), 

 No. 56, pp. 107-119, fig. 1). — The author made a study of different methods of 

 mechanical analysis used by other investigators with a view to adapting them 

 to the analysis of arid soils. 



The method advocated by the Bureau of Soils of this Department appeared to 

 be the most promising, but trials with arid soils showed that it failed, as did 

 most of the other methods, to separate a very considerable portion of the clay, 

 which goes to swell the silt and other fractions. 



Further tests were made of the clay content of arid soils as affected by length 

 of time of agitation, adding varying amounts of sodium carbonate, with and 

 without heat, and the height of the liquid in subsidence, together with a study 

 of the size of clay particles, the silt content, and the classification of soil 

 particles. 



The method of mechanical analysis of soils finally adopted and used with 

 success at the Khartum laboratories is described. The essential points of this 

 method are the use of from -io to i gm. of sodium carbonate in 1CM3 cc. of water 

 and the use of a brush in puddling. Boiling with dilute sodium carbonate with- 

 out the use of the brush not only required double the number of decantations to 

 effect a separation of the clay, " but the sum total of clay removed was 51.5 per 

 cent as against 54 per cent by the use of the brush." 



Separation of the clay by means of the centrifugal machine was found to be 

 more rapid, but required much more of the operator's attention. 



The author calls attention to the fact that although the proposed method is 

 recommended especially for arid soils, " it is equally suitable for those of humid 

 regions. Further, it is held that a method of this kind should invariably be 

 used, since othei'wise the comparison of humid with arid soils becomes impossi- 

 ble. It must be recollected also that the treatment by acid not only results at 

 times in the complete solution of the larger particles, but invariably in the ex- 

 traction of material from the finer constituents, so that as a method of ' mechan- 

 ical ' analysis it can not but be considered scientifically unsound." 



Observations on the moisture of sandy soils, A. J. Supbunenko (Zap. Novo- 

 Aleksandri. Inst. Selslc. Klioz. i Liesov., 21 (1910), No. 1, pp. 1-14 ^ «&«. in 

 Internat. Inst. Agr. [Rome], Bui. Bur. Agr. Intel, and Plant Diseases, 1911, No. 

 2, pp. 279, 280). — This article reports the results of experiments bearing on the 

 moisture content for different depths of typical sandy soils of Novo-Alexandria, 

 in relation to the rainfall and the kind and stage of growth of crop. 



The minimum loss by evaporation was observed in August at a depth of 75 

 cm. (about 29.55 in.) in a soil where oats were grown. 



The penetration of the water was most rapid in the soil where vetch was 

 grown. Where potatoes and rye were grown the moisture was noticeably con- 



