CHAPTER 16.
HUMAN REMAINS IN THE LOESS, AND THEIR PROBABLE AGE.
Nature, Origin, and Age of the Loess of the Rhine and Danube. Impalpable Mud produced by the Grinding Action of Glaciers. Dispersion of this Mud at the Period of the Retreat of the great Alpine Glaciers. Continuity of the Loess from Switzerland to the Low Countries. Characteristic Organic Remains not Lacustrine. Alpine Gravel in the Valley of the Rhine covered by Loess. Geographical Distribution of the Loess and its Height above the Sea. Fossil Mammalia. Loess of the Danube. Oscillations in the Level of the Alps and lower Country required to explain the Formation and Denudation of the Loess. More rapid Movement of the Inland Country. The same Depression and Upheaval might account for the Advance and Retreat of the Alpine Glaciers. Himalayan Mud of the Plains of the Ganges compared to European Loess. Human Remains in Loess near Maestricht, and their probable Antiquity.
NATURE AND ORIGIN OF THE LOESS.
Intimately connected with the subjects treated of in the last
chapter, is the nature, origin, and age of certain loamy deposits, commonly called loess, which form a marked feature in the superficial deposits of the basins of the Rhine, Danube, and some other large rivers draining the Alps, and which extend down the Rhine into the Low Countries, and were once perhaps continuous with others of like composition in the north of France.
It has been reported of late years that human remains have been
detected at several points in the loess of the Meuse around and
below Maestricht. I have visited the localities referred to; but, before giving an account of them, it will be desirable to explain what is meant by the loess, a step the more necessary as a French geologist for whose knowledge and judgment I have great respect, tells me he has come to the conclusion that "the loess" is "a myth," having no real existence in a geological sense or as holding a definite place in the chronological series.
No doubt it is true that in every country, and at all geological
periods, rivers have been depositing fine loam on their inundated
plains in the manner explained above in Chapter 3, where the Nile
mud was spoken of. This mud of the plains of Egypt, according to
Professor Bischoff's chemical analysis agrees closely in
composition with the loess of the Rhine. I have also shown when speaking of the
fossil man of Natchez, how identical in mineral character and in
the genera of its terrestrial and amphibious shells is the ancient
fluviatile loam of the Mississippi with the loess of the Rhine. But
granting that loam presenting the same aspect has originated at
different times and in distinct hydrographical basins, it is
nevertheless true that during the glacial period the Alps were a
great centre of dispersion, not only of erratics, as we have seen
in the last chapter, and of gravel which was carried farther than
the erratics, but also of very fine mud which was transported to
still greater distances and in greater volume down the principal
river-courses between the mountains and the sea.
MUD PRODUCED BY GLACIERS.
They who have visited Switzerland are aware that every torrent
which issues from an icy cavern at the extremity of a glacier is
densely charged with an impalpable powder, produced by the grinding
action to which the subjacent floor of rock and the stones and sand
frozen into the ice are exposed in the manner before described. We
may therefore readily conceive that a much greater volume of fine
sediment was swept along by rivers swollen by melting ice at the
time of the retreat of the gigantic glaciers of the olden time. The
fact that a large proportion of this mud, instead of being carried
to the ocean where it might have formed a delta on the coast or
have been dispersed far and wide by the tides and currents, has
accumulated in inland valleys, will be found to be an additional
proof of the former occurrence of those grand oscillations in the
level of the Alps and parts of the adjoining continent which were
required to explain the alternate advance and retreat of the
glaciers, and the superposition of more than one boulder clay and
stratified alluvium.