. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. 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-f
. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. 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. P
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectpetrolo, bookyear1913
