LOESS AND ADOBE 



319 



one, and it is doubtless to this that is due its uniform fertility. 

 On p. 318 are given analyses of loess from the United States, the 

 Rhine valley, and from Switzerland. 



The following table will serve to show the fine state of sub- 

 division in which the particles exist in loess as well as in a 

 dust brought down by snow, which will be described on p. 333. 



Mechanical Analysis of Loess and Dust 



CoNSTrruB^TS 



Moisture . . 

 Organic matter 

 Gravel . . . 

 Coarse sand . 

 Medium sand . 

 Fine sand . . 

 Very fine sand 

 Silt .... 

 Fine silt . . 

 Clay .... 



I 



II 



III 



IV 



CO " 



S2 S ::5 



CO •■ 



CO ^ 



^ s 



P5 S 

 W CJ S 



E: S 3 



-< 



M 



s i 



M 



Dust from Snow . 



eockville, 



Indiana 



ft » ■ * 





5.40 % 



3.17% 



ft # * « 



• * • • 



4.96 



11.98 



0.00 0/, 



0.00% 



0.00 



0.00 



0.00 



0.00 



0.00 



0.00 



0.00 



0.01 



0.00 



0.00 



0.01 



0.10 



0.00 



0.00 



7.68 



24.84 



23.14 



0.00 



61.85 



60.98 



54.81 



69.37 



9.60 



2.80 



2.46 



6.80 



15.15 



6.16 



9.45 



9.68 



94.29% 



94.88% 



99.22% 



100.00% 



Aughey^ gives the following section of the loess and soil in 



Nebraska. 



(1) Loess 4 feet 



(2) Black soil 2 ^"^ 



(3) Loess 4 '^ 



(4) Black soil H '' 



(5) Loess 5 '* 



(6) Black soil li '' 



(7) Stratified loess 15 ^^ 



This alternation is accounted for on the assumption of fre- 

 quent changes of level during the loess-forming period. It 

 would seem that the loess was deposited in shallow water and 

 that as the lake became filled plant life came in as in modem 

 bogs and marshes, and throve until sufficient organic matter was 



* Physical Geology and Geography of JSTebraska, p. 276. 



