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During dry seasons the winds picked up this dust and spread it out still more widely, forming the great banks of yellow loess whose fertile soil mantles the sides of many a valley in the Mississippi basin. Thus glaciers, streams, and winds laid down ten, twenty, fifty, or even one hundred feet of the finest, most fertile soil.
My reluctance in 1846 to regard the fossil human bone as of Pleistocene date arose in part from the reflection that the ancient loess of Natchez is anterior in time to the whole modern delta of the Mississippi. It has now risen more than 200 feet above its pristine level.
In the valley of the Rhine, as I before observed, the body of the loess, instead of having been formed at successively lower and lower levels as in the case of the basin of the Somme, was deposited in a wide and deep pre-existing basin, or strath, bounded by lofty mountain chains such as the Black Forest, Vosges, and Odenwald.
The farmers have found it more advantageous to clear away the boulders from the coarser drift in order to win soil which would give them fair returns. Those areas which are occupied by soil materials which have been brought into their position by the action of the wind may, as regards their character, be divided into two very distinct groups the dunes and loess deposits.
In the first place, I may remind the reader that the vertical movement of 250 feet, required to elevate the loess of Natchez to its present height, is exceeded by the upheaval which the marine stratum of Cagliari, containing pottery, has been ascertained by Count de la Marmora to have experienced.
They were of an age long posterior to that of the loess containing the bones of elephants and in which the human jaw now at Leyden is said to have been embedded. Geological Structure of the Island of Moen. Great Disturbances of the Chalk posterior in Date to the Glacial Drift, with Recent Shells. M. Puggaard's Sections of the Cliffs of Moen.
We know now that it consists of an inextricable entanglement of valleys, the mean altitude of which exceeds three thousand metres; we know that it is dominated by the peaks of Gouroumdi and Kauffmann, twenty-two thousand feet high, and the peak of Tagarma, which is twenty-seven thousand feet; we know that it sends off to the west the Oxus and the Amou Daria, and to the east the Tarim; we know that it chiefly consists of primary rocks, in which are patches of schist and quartz, red sands of secondary age, and the clayey, sandy loess of the quaternary period which is so abundant in Central Asia.
Even the colour of some of the land-shells, as that of Helix nemoralis, is occasionally preserved. In parts of the valley of the Rhine, between Bingen and Basle, the fluviatile loam or loess now under consideration is several hundred feet thick, and contains here and there throughout that thickness land and amphibious shells.
I found the Succinea oblonga, before mentioned, and Helix hispida in the Belgian loess at Neerepen, between Tongres and Hasselt, where M. Bosquet had previously obtained remains of an elephant referred to E. primigenius. This pachyderm and Rhinoceros tichorhinus are cited as characterising the loess in various parts of the valley of the Rhine.
Calcareous loam, buff-coloured, resembling loess, for the most part unstratified, in some places with slight traces of stratification, containing freshwater and land shells, with bones of elephants, etc.; thickness about 15 feet. 3.