62 THE PRINCIPLES OF SOIL MANAGEMENT 



so soft it may be easily carved with a shovel. Another 

 character common to much of the formation is the 

 presence of nodules and tubes formed by cementation 

 by lime carbonate. 



The loess is associated in occurrence with the margin 

 of the glacial deposits, especially in America and Europe, 

 and possibly in China. Just what this relation is is not 

 known, but much of the loess seems to be a fine rock- 

 flour of glacial origin, which has been drifted by the 

 wind and deposited on both purely glacial deposits 

 and on residual and water deposits, for it extends from 

 Illinois southward over the limestone region on to the 

 coastal plain in Mississippi. 



The adobe soils of the arid regions are thought by 

 some to be related to the loess in mode of formation. 

 Adobe also has peculiar physical properties, later to be 

 mentioned, but it exhibits a closer relation to water 

 deposits with which it has been classed. 



In parts of Kansas, Nebraska and other western 

 states, are soils formed of dust from volcanic vents and 

 deposited from the atmosphere. Such dust may be so 

 fine as to be carried long distances and remain in sus- 

 pension for a long period. Dust from the eruption of 

 Krokatoa, in the island of Java, was wafted around 

 the world, and gave a red glow to the sunset for a year 

 after its discharge. 



Table VII shows the chemical composition of the 

 wind deposits, chiefly loess. Columns I and X are 

 analyses of the hydrochloric acid solution. All others 

 are complete analyses. Agriculturally, sand-dunes are 

 of small value, largely because of their unfavorable 



