SOILS FERTILIZERS. 719 



Studies on the formation of silt and its transportation by streams in the 

 Alps and Pyrenees, A. Muntz and E. Lain^ {Compt. Rend. Acad. t^ci. [Puris], 

 160 {1915), Ko. 15, pp. 462-467). — Further studies on the character and amount 

 of the silty material carried bj' streams in the Alps and Pyrenees confirmed 

 the results noted in the above report. 



It was found that the quantities of soluble matter and matter carried in sus- 

 pension by the streams are extremely variable according to the geological origin 

 of the formations which are drained by them. Ancient formations, consisting 

 mostly of rocks, yield little silt, while recent formations yield relatively more 

 silt. Erosion is, therefore, greater in the Alps than in the Pyrenees. 



Analyses of water from the more important streams witli reference to the 

 content of suspended matter and matter in solution showed that where the 

 latter is large the former is frequently much larger. ^Mechanical analyses of 

 silts showed the close relation of the physical composition of the suspended 

 and deposited silt to the velocity of the stream. 



Observations on irrigation canals in the Alps region showed that at a ve- 

 locity of about 5 ft. per second, the sand grains deposited were between about 

 0.0039 and 0.0097 in. in diameter. With a velocity of about 2i ft. per second 

 the sand grains were between about 0.0019.5 and 0.003 in. in diameter, while 

 with a current about IJ ft. per second, the diameter of the silt particles de- 

 posited was less than 0.001 in. The matter remaining in suspension consists, 

 therefore, of the finest particles. 



It is pointed out from these results that the mountain waters, particularly 

 those of the Alps, when used for irrigation will deposit an appreciable layer of 

 silt on the land, the grains of which will varj- in size from coarse to fine as the 

 streams approach the plains and the grades and velocities diminish. 



Studies as to the agricultural value of these deposits are in progress. 



Physical and chemical conditions of cultivated and forest soils, A. Pab- 

 KOzzAxi {A7in. R. Sta.::. Sper. Affrum. e Friitticol. Acireale, 2 (1914), PP- 23-46). — 

 The views of others with reference to the physical and chemical properties of 

 forest soils are briefly presented, and studies of the changes produced in the 

 physical and chemical properties of forest soils by deforestation and cultivation 

 are reported. 



Little difference was, on the whole, observed between the nitrogen content 

 of the forested and deforested soils. The total nitrogen content of forested 

 soils was highest in soils partially cultivated and supporting olive and chestnut 

 trees, and lowest in typical forest soils supporting oak and beech trees. In the 

 oak soils the total nitrogen increased in the surface soil as the closeness of 

 texture decreased, while the opposite was true for the subsoil. In the deforested 

 soils the total nitrogen content was always high in those lying fallow, and 

 especially low in those planted to beans. 



The ammonia content of dense cork-oak soils was greater and the nitrate 

 content less than in medium or loose soils of the same type. Of the deforested 

 soils, those lying fallow contained the most ammonia. The deforested soils, 

 in general, contained more nitrate than the forested soils, although the sub- 

 soil of olive soils contained more nitrate than deforested cultivated soils. 

 There were more nitrates in the surface soil of the forested soils than in the 

 subsoiL 



The cultivated soils had a greater absorbing power, especially for potash, 

 than the forested soils. The water-soluble matter in the cork-oak soils de- 

 creased as the looseness in texture increased. The total soluble matter in 

 forested soils, especially in the surface soil, was increased after oxidation with 

 hydrogen peroxid. The same was true for the subsoil of recently deforested 

 soils, except fallow soil. 



