SOILS — FERTILIZERS. 23 



dissolve out a part of the silica. On this account, i. e., in neutral or alkaline 

 soils, they are unable to combine 1 Mol. of base with 1 Mol. AhOz. This shows 

 that the neutral, alkaline, or acid nature of the soil is indicated not by the per- 

 centage by weight of the bases extracted by boiling concentrated hydrochloric 

 acid, but by the molecular relation of the bases to the silica and clay in the 

 decomposing silicate. This relation best characterizes the condition of the 

 soil. 



The determination of the silica by the hydrochloric acid method according 

 to Van Bemmelen is to be recommended. The molecular calculation of re- 

 sults of analysis should also include the uncombined bases. 



The use of the Mitscherlich method of determining hygroscopicity is urgently 

 recommended in the investigation of soils and the use of the method of calcula- 

 tion in equivalents advanced by De Sigmond (E. S. K., 28, p. 318) is discussed. 



The molecular calculation is considered valuable whether dealing with a 

 physical or a chemical combination in the weathered complex. It is of equal 

 value for the calculation and judgment of soils whether the neutral reaction 

 is due to the existence of neutral aluminum silicates or to an absoi-ption maxi- 

 mum which shows the same molecular relation as the neutral aluminum silicate 

 and whether the acid reaction is due to acid aluminum silicates or to absori>- 

 tively unsatisfied gels of silica and alumina. 



Earth flows and structure soil in polar and subpolar regions, K. Sappeb 

 {Intcmat. Mitt. Bodenk., Jf {19H), No. 1, pp. 52-^7; abs. in Rev. Sci. [Parish, 

 52 (1914), I, No. 12, p. 370). — The soil flows occurring in polar and subpolar 

 regions are said to differ from those of tropical regions in that they are less 

 fluid and the stone and earth constituents are not as a rule separated into 

 homogeneous groups and layers by gravity. The soils are either homogeneous 

 or heterogeneous according to the slope of the ground nnd the degree of the 

 sorting and separating action produced by freezing and thawing, capillarity, 

 and alternate wetting and drying. 



The polygon and thufur soils of these regions (E. S. R., 30, p. 515) are said 

 to occur in the more homogeneous forms of flowing soil, the so-called stone 

 strips, nets, rings, and fields in the more heterogeneous forms. Several theories 

 are advanced as to the exact manner of their formation. 



Knox County soils, C. G. Hopkins, J. G. Mosier, J. H. Pettit, and J. E. 

 Readhimek ilUinois Sta. Soil Rpt. 6 {1913), pp. 43, pis. 2, figs. 5). — This is the 

 sixth of the series of the Illinois county soil reports, and deals briefly with the 

 physiography, topography, and formation of the soils, and more fully with soil 

 material and soil tjqpes, chemical composition of the soil, and field tests of the 

 fertilizer requirements of certain of the prevailing types. 



Knox County lies in the upper Illinois glaciation. The soils of the county 

 are divided into three classes as follows: " (1) Upland prairie soils, rich in 

 organic matter. These w^ere originally covered with wild prairie grasses, the 

 partially decayed roots of which have been the source of the organic matter. 

 The flat prairie land contains the higher amount of this constituent because 

 the grasses and roots grew more luxuriantly there and the higher moisture 

 content largely preserved them from decay. (2) Upland timber soils, including 

 those zones along stream courses over which forests once extended. These 

 soils contain much less organic matter because the large roots of dead trees 

 and the surface accumulations of leaves, tveigs, and fallen trees were burned 

 by forest fires or suffered almost complete decay. The timber lands are divided 

 chiefly into two classes — the undulating and the hilly areas. (3) Swamp and 

 bottom lands, which include the flood plains along streams and some small 

 peaty swamp areas. . . . 



48456°— No. 1—14 3 



