LOESS AND ADOBE 



317 



is stated to be as large as the whole of Germany, while it is 

 found in more or less detached portions over an area in addi- 

 tion, nearly half as large. In the United States the loess 

 covers thousands of square miles throughout the drainage 

 basin of the Mississippi Eiver. It is found in Ohio, Indiana, 

 Michigan, Iowa, Kansas, Nebraska, Illinois, Tennessee, Ala- 

 bama, Mississippi, Louisiana, Arkansas, Missouri, Kentucky, 

 and the Indian Territory. According to Professor Aughey it 

 prevails over at least 

 three-fourths of Nebraska, 

 to a depth ranging from 5 

 to 150 feet, and furnishes 

 a soil of extraordinary 

 strength and fertility. 



As here found, how- 

 ever, the seolian hypoth- 

 esis fails to satisfactorily 

 explain all the existing 

 conditions, and there is 

 little doubt but that it 

 represents in large part 

 the fine silt, the glacial 

 flour formed by the ice of 



the Glacial epoch, borne p^^^ 33.— ShowiBg outlines of particles ii 



southward by streams and Chinese loess. 



deposited in water just 



sufficiently in motion to carry the fine clay farther away. The 



American loess, in fact, illustrates in a remarkable manner the 



wonderful assorting power of water. 



Microscopic and chemical examinations of loess sustain this 

 conclusion. The particles are as a rule quite fresh and sharply 

 angular. Out of 150,000 particles examined under the micro- 

 scope only about 3% measure above .0025 of a millimetre and 

 1% over .005 of a millimetre. Quartz is the preponderating 

 material, with lesser amounts of orthoclase and plagioclase feld- 

 spars, white and dark micas, hornblende, augite, magnetite, 

 dolomite, and caleite. The loess of the Ehine valley and of 

 China offers no differences that can be readily described, though, 

 as will be noticed by reference to the analyses, there may be a 

 wide difference in chemical composition. Indeed, the essential 

 characteristic of the loess is a physical rather than a chemical 



m 



