SOILS — FERTILIZERS. 915 



SOILS— FERTILIZERS. 



The mineral composition of soil particles, (4. II. Failyer, J. G. Smith, and 

 H. It. Wade ii'. <S'. Dcpt. Agr., Bur. Hoiln Bui. .5'/, pp. 36). — This bulletin reports 

 the results of chemical analyses of the soil separates of a nuujber of soils cover- 

 ing all of the important asriculturul areas of the United States, includinf? soils 

 of the Coastal Plains, soils from crystalline and metamorpbic rocks, soils of 

 glacir.l origin, derived fi'om limestones and sbales, and soils of tbe arid region. 



The results obtained witli tbe different groups of soils and with rocks, soil.s, 

 and soil separates are compared. 



The results are summarized as follows: 



"As a general rule the smaller particles of soils are richer in potassium, cal- 

 cium, magnesium, and phosphorus tban the coarser particles. 



'' The concentration of these elements in the finer components is the more 

 pronounced as tbe soils have undergone more extreme weathering. 



" In glacial soils and others resulting largely from mechanical processes the 

 coarser particles are relatively high in the percentage of potash, lime, and 

 magnesia. 



" The larger mechanical components contain these elements in forms which by 

 protracted weathering will become more soluble, and they will ultimately be 

 concentrated in the finer components. 



" Calcium is often rather low in clay soils resulting from the weathering of 

 bard, compact limestones. It is generally abundant in soils recently formed 

 from easily broken down limestones. The sands of these latter soils may con- 

 tain a high percentage of calcium, probably as lime sand or as coatings on other 

 large mineral grains. 



"A comparison of soils and soil separates with crystalline rocks indicates that 

 in the process of the weathering of these rocks the phosphate remains of about 

 tbe same proportion or slightly increases. The lime and ix)tash seem to de- 

 crease in percentage, although minerals containing them are always present." 



Contribution to the subject of kaolin formation, O. Hahnel {Jour. PraJct. 

 CIkih., n. scr.. 7H (IDOS), Ao. J7-I8, pp. 2H0-2S.'i). — The author concludes from 

 bis investigations tliat weathering and kaolinization are cbemically distinct 

 processes. Tbe recent decomposition products of granite under humus were 

 found to be very similar in coiiiiyosilion to crude kaolin. 



On the radioactivity of the soil, F. Bobdas (Compt. Rend. Acad. Sci. [Paris], 

 I'll (nws). No. 20, pp. 92/h 925; ahs. in Rev. Sci. [Paris], 5. scr., 10 (1908), No. 

 22, p. 699; Jour. Chem. 8oc. [London], 96 {1909), No. 555, II, p. 7; Chem. 

 Zvnibl., 1909. I, No. 3, p. 209). — Observations are reported which show a de- 

 cided radioactivity in soils of the Andean Plateau, and tbese observations sug- 

 gest till' possibility of a relation bi'tween this natural radioactivity and the 

 formation of the large nitrate deposits in this part of Cbile (I'rovince of 

 Aconcagua). 



Soils of the United States, M. Whitney {TJ. 8. Dept. Agr., Bur. Soils Bui. 55, 

 pp. 2.'i3, pis. 2, figs. 7). — This bulletin contains a summary of recent soil inves- 

 tigations and a classification of the soils of the United States based upon the 

 work of tbe P.ureau of Soils to January 1. 190,S. 



"Tbe first part consists of seven lectures covering tbe activities of the 

 I'lUreau of Soils in the field and in tbe chemical and pbysical lal»oratories for 

 tbe last nine years and discuss«>s In a general way the most notable acbieve- 

 iiK'iits during tliat i>eriod. coni)Ied witb suggestions for furtber researcb in the 

 lundaniental field of soil study." It sums up tb<> more important of tbe con- 

 clusions of the Bureau, as in the main already pul)lislie<l, regarding tbe nature 



